Host: Prof. Peter Yunker

Title: Evolutionary dynamics of non-motile cells growing on surfaces

Abstract:

Surface-associated microbial populations are ubiquitous in nature and display evolutionary dynamics that are not yet well characterized, despite their importance to human health and technology. Dense populations of non-motile microbes expand on surfaces by cell growth and division, while interacting mechanically with neighboring ones. In this talk, I will show that mechanical forces among proliferating cells reduce the power of natural selection in microbial colonies, prolonging the survival of deleterious mutations and reducing the rate at which beneficial mutations expand in these populations. These mechanical interactions also favor the maintenance of genetic diversity in colonies growing in time-varying environments. Additionally, I will present evidence that evolutionary adaptation can change the way in which cells interact mechanically with each other. By repeatedly propagating cells from the periphery of Saccharomyces cerevisiae colonies and using them to initiate new colonies, we have observed significant changes in cell shape and budding polarity, with cells becoming progressively more elongated with time. These adaptations lead to altered mechanical interaction between cells and may promote faster colony expansion. The evolutionary insights from our research may have implications for our understanding of pathogenic yeast strains, many of which are characterized by an elongated cell shape that is presumed to enhance their ability to infiltrate host tissues.

Host: Colin Parker

Title: Breakthroughs in epitaxial graphene electronics: semiconducting graphene and the spectacular edge state.

Abstract: Graphene electronics was conceived at Georgia Tech 22 years ago when the first graphene, devices were produced using graphene grown on silicon carbide substrates (so called epigraphene) [1], and the worlds’ first graphene electronics patent was filed[2]. The GT team has made steady progress since. Several years ago we noted that narrow graphene ribbons exhibited resistances that are always close to 26 k Ohms, which corresponds to the resistance quantum h/e2 where h is Planck’s constant an e is the charge of the electron, that turned out to be caused by a unique state at the edge of the ribbon. We have recently shown that this edge state does not involve an electron or a hole, which are the usual carriers of currents in graphene, but the carrier appears to be a combination of the two to form a zero-energy mode [3]. Moreover, several of its properties resemble those of a Majorana fermion which was predicted in 1937. Very recently we have also discovered that the first graphene layer to grow on the silicon terminated silicon carbide crystal face, which has long been considered to an insulator, is in fact an excellent semiconductor when it is properly annealed. It is found to have a band gap of 0.6 eV and a room temperature mobility that exceeds 5000 cm2/Vs, which is greater than that of silicon and exceeds all other 2D semiconductors by a factor of 20 or more (Nature, in press). These two breakthrough discoveries put epigraphene on the path to become an important new 2D electronic material.

1. Berger, C., et al., Ultrathin Epitaxial Graphite:  2D Electron Gas Properties and a Route toward Graphene-based Nanoelectronics. The Journal of Physical Chemistry B, 2004. 108(52): p. 19912

2. de Heer, W.A., Berger,C, First,P.N, Patterned thin film graphite devices and method for making same. US patent US7015142B2 (Provisional filed Jun. 12, 2003).

3. Prudkovskiy, V.S., et al., An epitaxial graphene platform for zero-energy edge state nanoelectronics. Nature Communications, 2022. 13(1): p. 7814.

Bio: Walt A. de Heer is a Georgia Tech Regents’ Professor of Physics. His pioneering epitaxial graphene program, initiated in 2001, was inspired by his discovery of the room temperature ballistic transport properties of carbon nanotubes in 1998 and focuses on developing a viable silicon carbide platform for graphene-based nanoelectronics, which is currently his main interest. He has published more than 400 papers on epigraphene, carbon nanotubes and metallic clusters. He has an h-index of 97, and he has received the Web of Science Group’s Highly Cited Researcher Award yearly from 2010-2019.

Host: Prof. Simon Sponberg

Title: : Information gathering as a guiding principle for animal (and robot) movement

Abstract: 

I study how organisms integrate sensory information from multiple modalities across time and space to make decisions in complex naturalistic environments. My end goal is twofold: to understand how brains process sensory information, and to generate new, bioinspired, algorithms for engineered systems that enable the kind of resilience characteristic of biology. In my talk I will describe recent work in my lab that leverages optogenetics in freely flying fruit flies to remotely activate their sense of smell. Using this approach, we discovered a novel behavior they localize odor sources in still air. We also show that flying flies are capable of estimating the presence and direction of ambient wind. To understand how they might achieve this my group developed new control-theoretic tools for empirically assessing the nonlinear observability of individual states—that is, what sensor combinations and movement motifs are required such that wind direction can be estimated. Finally, I will describe our preliminary efforts to design nonlinear observers for wind direction, and describe a framework for how this approach could lead to estimation strategies that are resilient to unanticipated measurement anomalies.

Bio: Floris van Breugel is an assistant professor at the University of Nevada, Reno in the Mechanical Engineering Department, with affiliations with the Integrative Neuroscience and Ecology and Evolution programs. Floris earned his BS in Biological Engineering at Cornell, where he worked with Hod Lipson on bio-inspired flapping machines. He earned his PhD in Control and Dynamical Systems at Caltech under Michael H Dickinson and Richard Murray, with support from Hertz and NSF fellowships. After continuing as a postdoc with Michael, he did a brief postdoc at the University of Washington with Jeff Riffell, Nathan Kutz, and Bing Brunton with support from a Moore/Sloan Data Science Fellowship. He started his lab at UNR in 2019. His research brings together control theory, neuroscience, behavior, and bio-inspired robotics.  

Title: Neutrinos, reactors & anomalies

Abstract: Abstract: Neutrinos were discovered using a nuclear reactor as a source and since then much of our knowledge about neutrinos comes from experiments using reactors. I will briefly touch on the history of the use of reactors as neutrino source and motivate why they still play an important role today and in the future. An overview of the physics of how neutrinos are generated in reactors and how we can compute neutrino fluxes will follow. The developments of the past decade will be reviewed in particular. 2021 may have seen the resolution of one major riddle regarding the neutrino yield from uranium-235 and I will comment on this. I also will present the current status of the sterile neutrino in electron neutrino disappearance  including recent gallium results. I will conclude with an outlook towards the future both for our understanding of the reactor neutrino flux and reactor neutrino measurements. I also will be touching on coherent elastic neutrino nucleus scattering at reactors.

Bio: Patrick Huber is a professor of physics and an affiliate professor in the nuclear engineering program and a member of the Virginia Tech faculty since 2008. Huber conducts research on neutrino physics. He has helped build an internationally recognized program in neutrino physics both in basic science and applications to global and national security. He has authored more than 170 publications and has built an impactful research program.

In 2010, Huber co-founded the Center for Neutrino Physics at Virginia Tech and since 2018 he is serving as its director.. He was a lead developer of the GLoBES software package which is the standard for computing the physics sensitivity of many large neutrino experiments. In 2011, he performed what is currently the most accurate calculation of the reactor antineutrino spectrum emitted by nuclear reactors.

He has been a member or leader of a large number of study and planning efforts in the neutrino community, including his current service on the Particle Physics Project Prioritization Panel (P5), setting the research and budget priorities for the field in the United States for the next decade.

He is the recipient of multiple awards, including the Fermilab Distinguished Scholar, the Breakthrough Prize in Fundamental Physics, Early Career Research Award of the U.S. Department of Energy Office of High Energy Physics and election as a Fellow of the American Physical Society.

He earned a master’s degree and Ph.D. from Technical University of Munich, Germany.

Title: From sea cells to sea shells

Abstract: At the microscopic scale, virtually everything moves. From diverse patterns of movement one can distinguish living from non-living matter, bacteria from eukaryotes, random from directed, purposeful movement. I will discuss our recent work on phenotyping the motility of diverse microeukaryotes from long-time trajectory statistics. These include microswimmers that orchestrate propulsion-generating appendages (cilia and flagella) for swimming through fluids, as well as organisms that glide mysteriously without the need to resort to any appendages at all. We derive species-agnostic measures of active motility from high-speed live imaging experiments. We show how to distinguish between distinct yet stereotyped states (or gaits) of activity, and demonstrate how environmental cues (e.g. physical confinement, light, chemicals) induce systems-level cellular signalling whose effect becomes measurable in terms of transition probabilities between states. Finally, we speculate on the implications of these findings for the evolution of cellular decision making in basal eukaryotes.

Bio: Kirsty Y. Wan is associate professor at the Living Systems Institute, University of Exeter, UK, where she heads an interdisciplinary group researching the biophysics of microscale navigation, with particular emphasis on the motility and coordination of cilia. She obtained her PhD in biological physics from the Department of Applied Mathematics and Theoretical Physics, University of Cambridge, where she also held a Thomas Nevile Junior Research Fellowship at Magdalene College (2014–2017). In 2020, she received an ERC Starting Grant to explore the origins of motility and cognition in diverse protists.

Title: Gravitational Wave Detectors during the 4th Observing Run of the Advanced Detector Era

Abstract: The era of gravitational wave astronomy has accelerated rapidly, from the first direct detection of gravitational waves in 2015 to our current observing run with candidate events detected several times per week.  The Laser Interferometer Gravitational wave Observatory (LIGO) is jointly operated by Caltech and MIT for the National Science Foundation, and is currently in an observing phase that began in May 2023, and will continue through 2024. I will discuss innovations that have enabled the unprecedented sensitivity of the Advanced LIGO detectors, plans for future upgrades, as well as the exciting plethora of gravitational wave candidates we have seen so far in our 4th observing run.

Bio: Dr. Jenne Driggers is the Detection Lead Scientist at the LIGO Hanford Observatory.  She completed her PhD at the LIGO Caltech 40m interferometer prototype in 2015, and was a postdoc at the LIGO Hanford Observatory before joining the observatory staff.

Host: Prof. Peter Yunker

Title: : Barbed end depolymerization and pointed end polymerization - turning treadmilling on its head

Abstract: 

Actin is an essential protein. For over two decades, intracellular actin filaments have been thought to elongate at their barbed ends and depolymerize from pointed ends. This process, referred to as “treadmilling” has formed the central bedrock of our understanding of actin dynamics. Recent results from our lab however suggest that the treadmilling dogma might not always hold true. Using a combination of in vitro multicolor single molecule and single filament reconstitution experiments, we have discovered two new activities that call for reevaluation of the treadmilling dogma. First, we discovered the first-ever pointed-end polymerase VopF that processively polymerizes filament pointed ends in cells and from purified proteins. Further, VopF accelerates polymerization in presence of profilin and is a mechanosensitive protein - its rate of polymerization increases under pN-range pulling forces. Second, we have recently discovered that twinfilin, a member of the cofilin family of proteins, induces depolymerization of filament barbed ends. Interestingly we find that the depolymerase twinfilin, polymerase formin and blocker CP form a multicomponent complex at the filament barbed end. Importantly, both of these processes persist in physiological conditions containing high concentrations of profilin-bound monomers – strongly indicating intracellular implications for these newly discovered activities. Taken together, our findings call for taking a fresh look at actin treadmilling and its implications in cellular actin dynamics.

Biography:
Dr. Shashank Shekhar is an assistant professor of physics and cell biology at Emory University. His research interests in biological self-assembly lie at the interface of physics, biology and biochemistry. He is the recipient of several awards including the Whitman Early Career Award at the Marine Biological Laboratory and the Grand advances in Biology Prize from the French Academy of Sciences. He received his PhD in experimental cell biophysics from University of Twente (The Netherlands). He earned his master’s in Nanoscience and Molecular Bioengineering from TU Delft (Netherlands) and TU Dresden (Germany) and undergraduate degree in Physics in India.

Title: Beyond the Images: Astrochemistry with the James Webb Space Telescope

Abstract: 

In late 2021, the James Webb Space Telescope (JWST) was launched into space on an Ariane 5 rocket from French Guiana. JWST has unprecedented sensitivity and angular resolution and is now the premier space-based facility for near- and mid-infrared (0.6-28.5 μm) astronomy. The 6.5-meter telescope is equipped with four state-of-the-art instruments which include imaging, spectroscopy, and coronagraphy modes. These instruments are already returning amazing spectra and images of distant galaxies, star-forming regions, and planets in and out of the solar system. JWST's spectroscopic capabilities have already provided details of the composition of star forming regions, evolved stars, and planetary atmospheres that have not been measured previously. The complementary nature of this observatory with other high resolution imaging facilities (e.g., ALMA) will help us further our understanding of molecular heritage throughout the stellar lifecycle. We are entering the next era of Astrochemistry with JWST as we start to disentangle the complex molecular processes in the solar system, throughout the galaxy, and beyond. This presentation will highlight the some of the first Astrochemistry results with JWST and the capabilities it has to offer for this field of study.

Bio:

Dr. Milam works in the Astrochemistry Laboratory at the NASA Goddard Space Flight Center. She is an expert in rotational spectroscopy, observations, and laboratory modeling of astrochemistry and molecular astrophysics of the interstellar medium, evolved stars, star formation regions, and comets. Her observational focus is on the compositional studies of primitive bodies, namely comets and interstellar objects, and uses ground- and space-based facilities to understand their connection to the formation and evolution of planetary systems. She also has a laboratory dedicated to simulate interstellar/cometary/planetary ices and detect trace species employing the same techniques used for remote observations to help constrain the chemical complexity of the ices, the amount of processing that occurs, and interpret past and present data from missions that observe ice features.  Dr. Milam has been working on the James Webb Space Telescope (JWST) as Deputy Project Scientist for Planetary Science since 2014. Under this role she has helped enable observations within our own solar system from Near-Earth Asteroids to the farthest reaches of the Kuiper belt and even the brightest objects in the infrared sky (e.g. Mars). She has also led the study team for solar system science for WFIRST. In 2021, she was honored with asteroid 40706 (1999 RO240) was renamed to 40706 Milam. She received the NASA Exceptional Scientific Achievement Medal in 2022 for her work on enabling Solar System Science with JWST.

Title: 101 Mistakes to Avoid Before Submitting a Paper

Abstract: There is a strong desire, often driven by real or perceived pressures, to publish research in a top tier journal like Science.  However, with a rejection rate above 93%, it is a difficult process.  Beyond this, the publication landscape has gotten more complex with pre-print servers, predatory journals, mega-publishers, etc.  In this talk, I will describe the publication process at Science, within the broader context of publishing good papers in any journal.  I will focus on steps you can take to simplify the process both prior to submission and during the review and revision process.

Bio:

Undergrad – Chemical Engineering at the University of Toronto (Canada)

PhD – Materials Science at Cambridge University (UK)

Post-docs @ Bristol (Physics) (UK) and MIT (Chemical Engineering) (US)

Started as an editor at Science in 2001

Host: Prof. Harold Kim

Title: : Direct Observation of Self-Assembled Water Chains and their Coil-to-Bridge Transitions in a Nanoscopic Meniscus 

Abstract: 

Structures and behaviors of water confined between two surfaces are important in bio/nano sciences and water-based nanotechnology. I report observations of self-assembled water chains and their transitions from a coil state to a bridge state in a nanoscopic water meniscus in air. Large sawtooth-like oscillatory forces were shown when the normal and friction forces were measured as a function of distance between a sharp probe and a flat oxidized silicon surfaces using a force-feedback force microscope called “cantilever-based optical interfacial force microscope” (COIFM). In the force-distance plot, each oscillation is comprised of a rising-shaped (ö)  curve in the upward portion and a sigmoidal-shaped (ò) curve in the downward portion as the tip-sample distance decreases. Further analysis of each upward portion with the freely joined chain (FJC) model reveals that each portion is developed from self-assembled water chains with lengths ranging from 14 to 42 chain units in the meniscus. The analysis of downward portions reveals that each portion is generated by a “coil-to-bridge” transition of self-assembled water chains, whose lengths are between 197 and 383 chain units. The observed coil-to-bridge transitions explain many mysterious properties of confined water at the nanometer scale (e.g. long condensation distances, long nucleation timescale, high surface tension, long-range biomolecular interactions, etc.), thus dramatically improving the understanding of a variety of water systems in nature [1].

1. Byung Il Kim, Self-Assembled Water Chains: A Scanning Probe Microscopy Approach (Springer Nature, 2023).

Title: Searching for a Gravitational Wave Background with Pulsar Timing Arrays

Abstract: 

Bio: Sarah Vigeland is a gravitational wave astrophysicist whose work focuses on detecting gravitational waves with pulsar timing arrays. She is a member of the NANOGrav Collaboration, and currently serves as chair of the Gravitational Wave Detection Working Group. She earned her Ph.D. from MIT in 2012, and did postdocs at the Jet Propulsion Laboratory and the University of Wisconsin-Milwaukee before joining the faculty at the University of Wisconsin-Milwaukee as an assistant professor in 2019.

Title: The Blob: Topologically Entangled Living Matter

Abstract: Tangled active filaments are ubiquitous in nature, from chromosomal DNA and cilia carpets to root networks and worm collectives. How activity and elasticity facilitate collective topological transformations in living tangled matter is not well understood. In this talk, I will share our discoveries on why aquatic worms braid, tangle, and knot with their neighbors to form extraordinary mechano-functional living blobs - the stuff of science fiction. I will discuss how these soft, squishy, and 3-D blobs rapidly morph their shape, crawl, float, climb, self-assemble, and disassemble topological tangles. Using both mathematical models and robotic analogs, I will discuss how these “living polymers” solve Gordian knot problems using clever biophysics mechanisms that open a path to new classes of active topologically tunable robotic swarms.

Bio: 

Saad Bhamla studies biomechanics across species to engineer knowledge and tools that inspire curiosity. Saad Bhamla is an assistant professor of biomolecular engineering at Georgia Tech. A self-proclaimed "tinkerer," his lab is a trove of discoveries and inventions that span biology, physics and engineering. His current projects include studying the hydrodynamics of insect urine, worm blob locomotion and ultra-low-cost devices for global health. His work has appeared in the New York Times, the Economist, CNN, Wired, NPR, the Wall Street Journal and more. Saad is a prolific inventor and his most notable inventions includes a 20-cent paper centrifuge, a 23-cent electroporator, and the 96-cent hearing aid. Saad's work is recognised by numerous awards including a NIH R35 Outstanding Investigator Award, NSF CAREER Award, CTL/BP Junior Faculty Teaching Excellence Award, and INDEX: Design to Improve Life Award. Saad is also a National Geographic Explorer and a TED speaker. Newsweek recognized Saad as 1 of 10 Innovators disrupting healthcare. Saad is a co-founder of Piezo Therapeutics. Outside of the lab, Saad loves to go hiking with his partner and two dogs (Ollie and Bella).

Title: Active structures and flows in living cells

Abstract: Flows in the fluidic interior of living cells can serve function, and by their structure shed light on how forces are exerted within the cell. Some of these flows can arise through novel collective instabilities of the cytoskeleton, that set of polymers, cross-linkers, and molecular motors that underlie much of the mechanics within and between cells. I'll discuss experiments, mathematical modeling and analysis, and simulations of two such cases. One is understanding the emergence of cell-spanning vortical flows in developing egg cells, while the other arises from studying the nature of force transduction in the dynamics of microtubule arrays inside of synthetic cells. Both show the importance of polymer density in determining dynamics and time-scales, and have required the development of new coarse-grained models and simulation methods.

Bio: Dr. Michael J. Shelley is an applied mathematician who works on the modeling and simulation of complex systems arising in physics and biology. This has included, of late, modeling the dynamics of complex and active fluids, and examining transport and self-organization processes in cellular biophysics. He is co-founder and co-director of the Courant Institute's Applied Mathematics Lab at New York University, and is the Director of the Center for Computational Biology at the Flatiron Institute. He is a Fellow of the American Physical Society, the Society for Industrial and Applied Mathematics, and the American Academy of Arts and Sciences, and is a member of the National Academy of Sciences.

Title: Open quantum systems in cosmology

Abstract: The open questions in cosmology have been open for decades: Why is the present-day universe undergoing accelerated expansion? What is the particle physics behind the origin of structure in the universe? What is the dark matter? All of these questions must be answered in the framework of a quantum theory, and at least two also require quantum gravity. I will discuss why open quantum systems, where an unobserved environment affects the evolution of the observed system, are starting to play a more prominent role in cosmology and how they help to generate new ideas for long-standing puzzles.

Title: Error Mitigation and Suppression in Superconducting Quantum Processors

Abstract: In principle, quantum computers have the potential to be able to solve problems that are intractable with classical computers. However, all currently existing quantum platforms suffer from errors; typical state of the art error rates are approximately one error per thousand operations. The central problem in building and operating these devices successfully is how we deal with these errors. Using superconducting quantum processors as an example, I will discuss some sources of errors, including decoherence, crosstalk, and control noise. With these in mind, I will then discuss at a high level three main strategies for handling these errors: error suppression, error mitigation, and error correction.

Bio: Dr. Oliver Dial was named an IBM Fellow in 2021 for his contributions to quantum computing hardware. He is IBM Quantum’s CTO, ensuring IBM’s quantum hardware and software together deliver an outstanding experience. Oliver received his PhD from MIT in 2007 for research in two-dimensional electron and hole systems. He then entered the field of quantum computing as a post-doc at Harvard, demonstrating the first two-qubit gate between semiconductor singlet-triplet qubits and performing pioneering charge noise spectroscopy in these systems. He joined IBM as a research scientist in 2012.

Committee members:
Dr. James (JC) Gumbart, School of Physics, Georgia Institute of Technology (advisor)
Dr. Simon Sponberg, School of Physics, Georgia Institute of Technology
Dr. Peter Yunker, School of Physics, Georgia Institute of Technology
Dr. Ingeborg Schmidt-Krey, School of Chemistry & Biochemistry, Georgia Institute of Technology
Dr. Lynn Kamerlin, School of Chemistry & Biochemistry, Georgia Institute of Technology

Abstract: “This dissertation explores the evolution and development of proteins, specifically membrane-embedded proteins in microorganisms, including viruses and bacteria, using computational methodologies like Molecular Dynamics (MD) simulations and machine learning techniques.

We first study outer-membrane proteins (OMPs) in Gram-negative bacteria, specifically the Escherichia coli protein OmpX. Through simulation of its engineered variants, we find a link between β-barrel size, shape, and the presence of inward-facing glycines. we find that the fraction of glycines in β-barrels decreases as the strand number increases, suggesting an evolutionary role in the addition or removal of glycine in OMP sequences.

Next, our investigation shifts to the Spike protein in SARS-CoV and SARS-CoV-2 viruses. Despite differences in their receptor-binding domains, the two proteins bind to the human ACE2 receptor in similar ways. Using MD simulations, machine learning, and free-energy perturbation calculations, we quantify these subtle mutations and demonstrate how evolutionary changes directly influence binding affinity.

Lastly, we study the glycosylation profiles of virus variants and their impact on the glycan shield of the Spike protein. Our findings reveal that the Spike protein in the Omicron variant is less enveloped by glycans, affecting the accessible area in specific residues.

This work sheds light on the evolution of membrane proteins, their structure, interactions, and glycan shields, offering valuable insights into protein evolution.”

Committee:      Dr. Roman Grigoriev, Department of Physics, Georgia Institute of Technology (advisor)
                          Dr. Michael Schatz, Department of Physics, Georgia Institute of Technology
                          Dr. Kurt Wiesenfeld, Department of Physics, Georgia Institute of Technology
                          Dr. Elisabetta Matsumoto, Department of Physics, Georgia Institute of Technology
                          Dr. Alberto Fernandez-Nieves, Department of Physics, University of Barcelona

Summary:

The Sparse Physics-Informed Discovery of Empirical Relations (SPIDER) algorithm is a technique for data-driven discovery of partial differential equations (PDEs). SPIDER combines knowledge of symmetries, physical constraints like locality, the weak formulation of differential equations, and sparse regression to find new physical descriptions of data with spatiotemporal variation. SPIDER is a valuable tool in synthesizing scientific knowledge as demonstrated by its applications.

A novel feature of this algorithm is to not only learn physics in a symmetry-consistent way, but to learn only relations in irreducible representations. That is, relations are broken down into their indivisible parts, so that each PDE is learned truly independently. This prevents implicit bias and unknowingly using evidence from one relation for an independent one. A library of nonlinear functions is constructed for each irreducible representation of interest, and sparse linear combinations of these library terms are sought.

The weak formulation of differential equations is used: library terms are sampled not at individual points but integrated over spacetime domains with flexible weight functions. Integration by parts sidesteps numerical differentiation in many situations and increases robustness to noise by orders of magnitude. Clever weight functions can remove discontinuities and even entirely remove unobserved fields from analysis. Once these library terms have been sampled, sparse regression algorithms can find relations ranging from dominant balances to multi-scale quantitatively accurate PDEs.

Applications to numerical 3D fluid turbulence and 2D active nematic turbulence are presented. It is demonstrated that SPIDER can recover complete mathematical models of both systems and consistent redundancies across disjoint irreducible representations. In every representation analyzed, at least one relation is found. The active nematic system is of particular interest, as a new effective 2D description of the system is identified by SPIDER. While this system of equations holds only in regions of saturated microtubule density, it offers valuable physical insight.

Committee: 

Dr. Colin Parker, School of Physics, Georgia Institute of Technology (advisor)
Dr. Michael Chapman, School of Physics, Georgia Institute of Technology
Dr. Brian Kennedy, School of Physics, Georgia Institute of Technology
Dr. Martin Mourigal, School of Physics, Georgia Institute of Technology
Dr. Joshua Kretchmer, School of Chemistry and Biochemistry, Georgia Institute of Technology

Abstract:

Real world material systems often have properties with roots in quantum mechanics which we are interested in. Studying such systems by classical models is often unsuitable, being either ineffective or inefficient. The general approach is through quantum simulations, in which laser cooled and trapped atoms are used as simulators. This thesis presents our study of ultracold quantum gases of Li-6, signifying our progress in building a quantum simulator. At first, we demonstrate the achievement of molecular BECs of Li-6 in its lowest and second lowest hyperfine state pairs by an all-optical method. We employ mostly standard techniques, but also introduce several unique features in our hardware system. Then, by preparing a degenerate Fermi gas of Li-6 in a mixture of its second lowest two hyperfine states and measuring its spin susceptibility in the BEC-BCS crossover, we study the “pseudogap” effects and compare it to the high-Tc cuprates. We develop a novel radiofrequency method to map the mixture to an RF-dressed basis. Imbalances are created between thermally equilibrium RF-dressed states, from which the spin susceptibilities are extracted over the interaction strength-temperature phase diagram. The results of such measurements for gases in the strongly interacting regions are compared to a mean-field model, to the ideal Fermi gas model, and to experimental results from several other publications. Lastly, we implement a 1D optical lattice. We tune the single particle dispersion relation using a shaken lattice by Floquet engineering. The driving signal is modulated through an IQ modulator fed to two AOMs. By loading a molecular BEC of Li-6 pairs into the shaking lattice, we have achieved coupling between the first two energy bands resulting in a double-well dispersion. The major result of our observations is that the atomic cloud under the inverted dispersion bifurcats into two soliton-like peaks in the momentum space. While in the position space, a density corrugation is formed in the atom cloud, which is caused by the two bifurcated wave peaks with opposing momentum beginning to separate. We have not yet fully understood the mechanism behind this phenomenon. For now, we model the result semi-classically by the Gross-Pitaevskii equation. The numerical simulations match reasonably well with the experimental results. 

Committee:
Dr. Gongjie Li, School of Physics, Georgia Institute of Technology
Dr. Tamara Bogdanovic, School of Physics, Georgia Institute of Technology
Dr. Predrag Cvitanovic, School of Physics, Georgia Institute of Technology
Dr. Chris Reinhard, School of Earth & Atmospheric Sciences, Georgia Institute of Technology
Dr. Smadar Naoz, Department of Physics and Astronomy, UCLA

Abstract
This work focuses on the gravitational interactions of astrophysical systems. In particular, we focus on the triple system dynamics, including mildly hierarchical three body secular dynamics, as well as precession induced resonances of binaries under the perturbation of a third companion. We apply our theoretical investigations of these physical processes to wide-orbit planetary systems and black hole binaries embedded in AGN disks.

More specifically, we consider the secular dynamics of a test particle in a mildly-hierarchical configuration. We find the limit within which the secular approximation is reliable, present resonances and chaotic regions using surface of sections, and characterize regions of phase space that allow large eccentricity and inclination variations. Finally, we apply the secular results to the outer solar system. We focus on the distribution of extreme trans-neptunian objects (eTNOs) under the perturbation of a possible outer planet (Planet-9), and find that in addition to a low inclination Planet-9, a polar or a counter-orbiting one could also produce pericenter clustering of eTNOs, while the polar one leads to a wider spread of eTNO inclinations.

Beyond mildly hierarchical triple dynamics, we also propose a novel pathway through which compact binaries could merge due to eccentricity excitation, including in a near coplanar configuration. Mechanisms have been proposed to enhance the merger rate of stellar mass black hole binaries, such as the Von Zeipel-Lidov-Kozai mechanism (vZLK). However, high inclinations are required in order to greatly excite the eccentricity and to reduce the merger time through vZLK. Specifically, a compact binary migrating in an AGN disk could be captured in a precession-induced resonance, when the apsidial and nodal precession rates of the binary are commensurable to the orbital period around the supermassive black hole. We find 8 such resonances upto quardupole order of the Hamiltonian.  We show that if a binary is captured in these resonances and is migrating towards the companion, it can experience large eccentricity and inclination variations. Eccentricity is excited when the binary sweeps through the resonance which happens only when it migrates on a timescale 10-100 times the libration timescale of the resonance. Libration timescale decreases as the mass of the disk increases. The eccentricity excitation of the binary can reduce the merger timescale by a factor up to $10^{3−5}$.

Committee:
Dr. Roman Grigoriev, Department of Physics, Georgia Institute of Technology (advisor)
Dr. Michael Schatz, Department of Physics, Georgia Institute of Technology
Dr. Kurt Wiesenfeld, Department of Physics, Georgia Institute of Technology
Dr. Predrag Cvitanović, Department of Physics, Georgia Institute of Technology
Dr. Luca Dieci, Department of Mathematics, Georgia Institute of Technology

Abstract
Chaos is an intrinsic property of many real world systems, impacting a number of today's open research questions. While many chaotic systems have known governing equations and are deterministically ``solved," we still lack a comprehensive framework for predicting, controlling, and simply making sense of such systems. And while recent advances in technology allow us to explore these systems through direct numerical simulation better than ever before, the need for an insightful theoretical framework is still very much alive. 

Such a framework exists in a subset of chaotic systems, known as Axiom A chaotic systems and, as a result, Axiom A systems are understood quite well. However, the requirements for a system to be Axiom A are quite strict, and the overlap between systems that are Axiom A and those that are physically significant is quite small.

A very important concept in Axiom A systems is the notion of shadowing, which allows the chaotic dynamics to be decomposed piecewise-in-time in terms of much easier to analyze solutions known as periodic orbits. Periodic orbits are solutions to the governing equations that, unlike chaos, repeat in time. Their compactness make periodic orbits very simple objects to manipulate, both numerically and theoretically. A decomposition in terms of periodic orbits results in a predictive theory of Axiom A systems, both deterministically and statistically.

In this talk, I will discuss how to generalize aspects of this decomposition to a broader class of (non Axiom A) chaotic systems, specifically, fluid turbulence. Although recent studies suggest that Exact Coherent Structures (ECS)---e.g., repeating solutions to the Navier-Stokes equation---are descriptive of turbulence, it is an open question whether they are to turbulence what periodic orbits are to Axiom A chaos. I will present evidence of ECS being shadowed by turbulence in various fluid geometries and, additionally, present preliminary work suggesting a statistical picture of turbulence in terms of ECS may also be feasible. "

Title: Entropy, molecular motors, and non-thermal equilibrium statistical physics

Abstract: The transport of molecular cargos in neuronal cells is analyzed in the context of new developments in statistical physics. Our development of very bright optical probes enabled the long-term single tracking of molecular cargos in live neurons for tens of minutes. The number of dynein motors transporting a cargo was found to switch stochastically from one to up to five motors during the long-range transport in neurons. We are able to resolve individual molecular steps, and formulated a new, quantitative chemo-mechanical model where two ATP molecules are hydrolyzed sequentially. Our model is consistent with extensive structural, single-molecule and biochemical measurements.

The observed fluctuations in movement can be described by a steady-state non-thermal equilibrium effective temperature. The Fluctuation Theorem, first proved in 1993 and applicable in any non-thermal equilibrium processes, is shown to yield a minimum “uncertainty principle” limit, where the product of heat entropy and the statistical precision of any physical operation is greater than or equal to 2kBT. In the context of intercellular molecular transport, we show that a smaller variance in the movement of the cargo vesicle demands a greater expenditure of energy.

Committee:
Dr. Chandra Raman, School of Physics, Georgia Institute of Technology (advisor)
Dr. Colin Parker, School of Physics, Georgia Institute of Technology
Dr. Carlos Sa de Melo, School of Physics, Georgia Institute of Technology
Dr. Martin Mourigal, School of Physics, Georgia Institute of Technology
Dr. Ronghua Pan, School of Mathematics, Georgia Institute of Technology

Abstract: 
Relaxation or thermalization of isolated or driven quantum systems has drawn considerable research interest, and defect formation is known to be closely related to the progress towards equilibrium or steady states. In our work, we use quasi-1D spinor Bose-Einstein condensates (BECs) as platforms to tackle such non-equilibrium problems. The spinful superfluids feature for their rich internal degrees of freedom and give rise to novel defects such as vector solitons. We report on our studies of two essential ingredients of non-equilibrium dynamics in spinor BECs, namely magnetic solitons and spin waves. Using a spin-dependent phase imprinting technique, we generate magnetic solitons in an antiferromagnetic spin-1 BEC, where the solitons manifest themselves as a localized spin excitation propagating upon a balanced two-component condensate[1]. The study is then extended to three-component solitons by harnessing the underlying SO(3) symmetry of the spin-1 manifold[2]. Moreover, we theoretically explore magnetic solitons in ferromagnetic spin-1 BECs, where the solitons behave as a local spin-flip propagating on top of a spin-polarized background[3]. Most recently, we investigate resonance phenomena in a driven spinor BEC. By driving the quadratic Zeeman shift periodically, we observe the spin waves generated from the parametric amplification of the spin-mixing dynamics.

[1] Phys. Rev. Lett. 125, 030402

[2] Phys. Rev. Research 3, L012003

[3] Phys. Rev. A 105, 013313

Committee:
Dr. Ignacio Taboada, School of Physics, Georgia Institute of Technology (advisor)
Dr. David Ballantyne, School of Physics, Georgia Institute of Technology
Dr. Nepomuk Otte, School of Physics, Georgia Institute of Technology
Dr. John Wise, School of Physics, Georgia Institute of Technology
Dr. Carlos Argüelles-Delgado, Department of Physics, Harvard University

Abstract: 
Our current understanding of the universe stems from observations across the electromagnetic spectrum as well as additional messengers, such as gravitational waves, cosmic rays, and neutrinos. Particularly, we have observed a high-energy astrophysical diffuse neutrino flux using the IceCube Neutrino Observatory at the South Pole for the past 10 years. However, the specific sources that contribute to this flux are not known. More recently, IceCube reported evidence of neutrino emission from the nearby AGN and Seyfert II galaxy NGC 1068. In this work, I present a new method to ask: Is NGC 1068 a time-variable neutrino source? By applying this method to an identical data sample that was used to report the evidence of emission, I conclude that the neutrino emission from NGC 1068 is consistent with a steady source. This new method can be applied to future candidate point sources observed by IceCube and serves as a source characterization tool.

Hawking radiation elegantly unifies quantum field theory, general relativity, and thermodynamics. Primordial Black Holes (PBHs) offer a way to directly observe Hawking radiation as the hole evaporates over the age of the universe. No evidence for Hawking radiation or PBHs has been reported yet and PBHs have been extensively studied as Dark Matter (DM) candidates in the past. In this work, I present a search for high-energy neutrino emission from an individual PBH that is evaporating in our local universe using data collected by IceCube. This is the first time high-energy neutrinos have been used to search for Hawking radiation from an evaporating PBH. Due to null detection in this search, I present an upper limit to the PBH evaporation density rate and compare it to existing limits from gamma-ray telescopes.

Committee:
Dr. John Wise, School of Physics, Georgia Institute of Technology
Dr. Laura Cadonati, School of Physics, Georgia Institute of Technology
Dr. Gongjie Li, School of Physics, Georgia Institute of Technology
Dr. Surabhi Sachdev, School of Physics, Georgia Institute of Technology
Dr. Alexander Ji, Department of Astronomy and Astrophysics, University of Chicago

Abstract:
The exact evolution of elements in the universe, from primordial hydrogen and helium to heavier elements like gold and platinum, is still under scrutiny. The transformation from primordial to heavier elements starts with the first generation of stars, through nuclear fusion in their cores. These first stars, called Population III or Pop III, are the first radiating objects, formed from metal-free gas clouds in the very early universe. The supernova deaths of these stars leads to the enrichment of their local environments with new metals, and can leave behind neutron stars as remnants. These compact objects can end up in binary systems with other neutron stars, and eventually merge, which allows for the rapid neutron capture (r-process) to take place. This process is responsible for half of the elements heavier than iron, some of which end up enhancing the next generation of stars with this r-process material. These r-process enhanced stars, seen in the universe in ultra-faint dwarf galaxies like Reticulum II, can give us insight into the stellar ancestors of these stars. With the launch of JWST, we may be able to soon see the galaxies made up of the first stars, and thus understanding early star formation is critical as we observe parts of the universe never seen before.

In this work, I have studied the birth sites of Pop III stars using high resolution, cosmological simulations. I have found that the minimum mass threshold, the minimum threshold at which galaxies can form Pop III stars, is not affected by the instantaneous Lyman-Werner radiation background, and H2 self-shielding allows smaller mass halos to form Pop III stars. I have found that multiple Pop III stars can form in a single halo, and high mass halos can accumulate both young and old Pop III stars through hierarchical merging. I then focused on how neutron star mergers (NSMs) affect the second generation of stars by varying the explosion energy and the delay time, the time between NS binary system formation and r-process production, in a suite of zoom-in simulations of a single halo. I found that in general, a NSM leads to significant r-process enhancement in the second generation of stars. A high explosion energy leads to all enhanced r-process stars being highly enhanced, while a lower explosion energy leads to a higher mass fraction of stars being r-process enhanced, but not as many being highly r-process enhanced. When a NSM has a short delay time, there is a higher mass fraction of stars being r-process enhanced, but a smaller fraction being highly r-process enhanced. Finally, in collaboration with my research group, I have created a fitting pipeline to model the spectral energy distributions of photometric data of high redshift galaxies detected by JWST. We use scaling relations from high redshift cosmological simulations to better model galaxies in the early universe and determine their full star formation history. We also include other bright sources in the total SED, like an active galactic nuclei and binary stellar populations. We find that our fitting pipeline matches the photometry of high redshift galaxies very well, and conclude that models of the high redshift universe need to be further refined in order to accurately model this early environment.

Title: That’s Not Physics

Abstract: Have you ever left a colloquium or a seminar and thought to yourself ``that was interesting, but it wasn’t physics”? If so, you are in good company, because there has long been disagreement in our community about which research specialties belong to the canon of physics and which do not, particularly when it comes to hiring faculty members into physics departments to train PhD students.  In this talk, I discuss some aspects of this debate from the founding of American Physical Society to the present day.  Examples include a field that was once a part of physics but is not anymore; a field that was once ``not physics” but is definitely so today; and a field whose status as “physics” remains unsettled in the minds of many.

Abstract: Black holes as massive as several billion solar masses appeared within a billion years after the Big Bang.  The origin of these objects remains a mystery.  I will present three competing ideas on how such massive black holes may have formed in the early universe, (i) via catastrophic collapse of gas in protogalaxies, (ii) via rapid gas accretion onto the black hole remnants of the first stars, or (iii) via many successive mergers between black holes.  I will then discuss the role of ambient gas in facilitating mergers between black holes, producing unique observational signatures, and impacting low-frequency gravitational wave emission.  Upcoming observations with the recently launched James Webb Space Telescope (JWST) and with the space-based Laser Interferometer Space Antenna (LISA) will help us understand the origin of massive black holes, including the details of their mergers.

Bio: Professor Zoltan Haiman received a Physics B.S. degree from MIT, and he attended graduate school in Cambridge, UK, and at Harvard University, where he received a Ph.D. in Astronomy in 1998. He was chosen as one of Popular Science Magazine's Brilliant 10 young scientists in 2002 and received the New York Academy of Sciences Blavatnik Award in 2010 and a Simons Fellowship in Theoretical Physics in 2016. He was a Hubble Fellow at Princeton and a postdoc in the theory group at Fermilab, before joining the faculty at Columbia University.

Professor Haiman's research has explored broad topics in theoretical astrophysics and cosmology, including the formation of the first stars, the emergence of massive black holes, the nature of dark energy and dark matter, as well as astrophysical sources of gravitational waves.

Bio: Hirohisa Tanaka earned his PhD from Stanford University, where he studied rare decays of the B meson on the BaBar experiment at SLAC. As a postdoc at Princeton University, he worked on MiniBooNE, an experiment probing potentially exotic properties of the neutrino. As a faculty member at the University of British Columbia, the Institute of Particle Physics, and the University of Toronto he worked on the T2K neutrino oscillation experiment. Since 2018, he returned to SLAC and Stanford University as a faculty member and participates in the DUNE collaboration.

In this colloquium I will illustrate progress on two forefronts of this vast and highly active research field.

First, I will present a universal classification of the different dynamical phases of matter which can occur in cavity QED with multi-level atoms and with bosonic (or fermionic) species [1]. Such categorization is not only the first effort to encapsulate the broad plethora of non-equilibrium phenomena which have been uncovered in the last decade in cooperative quantum optics [2], but it also offers a versatile route to generate on demand non-equilibrium, coherent, phases of matter.  Along these lines, I will discuss applications for the enhancement of superconducting response in quantum simulators of BCS models [3] (originally realized in conventional cold atoms experiments [4]), and to classical and quantum synchronization [1].  

 In the second part, I will discuss a counterintuitive proposal for controlling photon losses in order to enhance quantum coherence and mold on-demand different dynamical correlation patterns which don’t have a counterpart in purely isolated systems [5]. Harnessing dissipation in cavity QED allows us to realize exotic instances of critical phenomena with tunable scaling behavior [6], and to produce novel spin-squeezed states at a target wave-vector, with applications to the magnetometry of inhomogeneous fields [5]. 

Time permitting, I will flash how dissipation control can inspire novel algorithms for memory retrieval and universal decoding in large scale quantum circuits, with unexpected connections to the black hole paradox in quantum information science [7].

_{References:
[1] R. Valencia-Tortora, S. Kelly, T. Donner, G. Morigi, R. Fazio, JM, arXiv:2210.14224 (2022)
[2] JM, M. Eckstein, M. Foster,  A. M. Rey, Rep. Prog. Phys. 85 116001 (2022)
[3] S. Kelly, J. Thompson, A. M. Rey, JM, Phys. Rev. Research 4, L042032 (2022)
[4] S. Smale, P. He, B. Olsen, K. Jackson, H. Sharum, S. Trotzky, JM,  AM Rey, J. Thywissen, Science Advances 5 (8), eaax1568 (2019)
[5] K. Seetharam, A. Lerose, R. Fazio, JM, Phys. Rev. Research 4, 013089 (2022)
[6] JM, Phys. Rev. Lett. 129, 050603 (2022)
[7] Z. Weinstein, S. Kelly, JM, E. Altman, arXiv:2210.14242 (2022)}

Bio: Jamir Marino was born and studied physics in Palermo, Sicily. After his PhD under the supervision of A. Silva at SISSA (Trieste), he went for a postdoctoral job in the group of S. Diehl in 2014 (Innsbruck-Dresden). In Winter 2015 he became Alexander von Humboldt Fellow in Cologne, and in Summer 2017 moved to the US working at JILA/CU Boulder in the groups of A. M. Rey and R. Nandkishore. In Spring 2018, Jamir started a Marie Curie Global Fellowship at Harvard University, collaborating with the research team of E. Demler.

Since October 2019 he was the Junior Professor at the University of Mainz leading a research team of 15 young scientists. In Spring 2022 he held a Senior Scientist position at UC Berkeley, as part of a sabbatical semester.

Prof. Marino’s approach to non-equilibrium dynamics pivots around interdisciplinary applications which are capable to connect different AMO platforms. His approach aims at enriching modern quantum simulators using a many-body and statistical mechanics perspective, focusing on emergent phenomena and employing a condensed matter language.

Speaker: Itamar Kolvin

Host: Zeb Rocklin

Abstract: Biological interfaces are continuously perturbed by energy-consuming molecules. Active stresses at interfaces make cells crawl, change shape, and reorganize their content. How should we understand the dynamics of active interfaces?  I will present experiments that couple active stresses to soft interfaces. Active liquid-liquid interfaces are formed by merging molecular motors and their associated biofilaments with water-soluble phase-separating polymers. Consequently, interfaces support wave propagation without inertia, droplets undergo spontaneous fission, and fluids climb vertical walls. I will also show how active stresses mold crosslinked actin filament bundles into dynamic solid membranes. Giant bending fluctuations endow membranes with soft stretching degrees of freedom. For membranes that are a few millimeters in width, system-size periodic oscillations appear that are coupled to unidirectional flow waves. Active stress is thus an emerging paradigm for the assembly and dynamics of matter.

Bio: I am an experimental physicist interested in the multi-scale dynamics of matter. I obtained my Ph.D. in Physics from the Hebrew University of Jerusalem for studying dynamic fracture in brittle hydrogels. In 2017, I became a Human Frontier Science Program fellow at UC Santa Barbara. I assemble materials from biological components with unique functionalities to ask how active matter moves and how fibrous gels deform.

Cell flows in the early Drosophila embryo are driven by an interplay between biological signaling and tissue mechanics. Using live imaging, we observe how changes in the expression of force-generating proteins, and the geometry of the tissue relate to tissue dynamics at the onset of morphogenesis. We use theoretical and computational methods to model the behavior of the tissue and challenge our findings using select genetic perturbations of the embryos. With this combination of experimental and modeling approaches, we have uncovered how organized multicellular dynamics emerge from genetic, mechanical, and geometric “information” during early Drosophila development.

This type of biological process relies heavily on the consumption of energy, which keeps the system from relaxing to an equilibrium (or dead) state. I will briefly introduce how, in combination with biophysical studies, synthetic model systems allow us to perform highly-controlled tests on the impact of energy input on the self-organization of form and function in different systems.  

Bio: Emily Gehrels is a postdoctoral researcher at the Marseille Developmental Biology Institute working to understand the physical mechanisms at play during Drosophila embryo development. Previously, she completed her doctoral work at Harvard University where she created responsive and dynamic systems using colloids. In her future work, she plans to bring together the perspectives of soft-matter physics and developmental biology to uncover the fundamental principles underlying the creation of form in both living and synthetic systems.

Abstract: Cuprates — superconductors (SC) with high critical temperature (Tc) — are prominent examples of strongly correlated systems. The emerging fields of Moire systems, where 2 crystalline patterns interfere to form a long period modulation, meanwhile shed new light on strong correlation physics. In this colloquium I will describe a gapless chiral superconductor, arising from symmetry constraints, in Moire cuprate systems.

Twisted cuprates hold promise for high Tc topological SC, with potential implications for quantum computing. While previous predictions are based on simple weakly interacting models, here we examine the vital role played by realistic aspects and strong correlations and report a gapless chiral SC. We discuss signatures which are being studied in ongoing experiments. Alternate routes towards topological SC and other directions in Moire systems will be discussed.

Bio: Xue-Yang Song obtained her PhD in theoretical condensed matter in 2021, working with Ashvin Vishwanath and is currently a Moore postdoctoral fellow at MIT. She studies strongly correlated matter that shows emergent quantum phenomena like fractionally charged excitations and high-temperature superconductivity. She is interested in both developing formal theories and making concrete connections to realistic solid state or synthetic systems. Besides physics, she enjoys cycling and playing with her cat.

Abstract: Soft matter, condensed matter with large response functions to external stimuli, is of great importance in natural systems and technological applications. Liquid crystal (LC), one of the textbook soft matter, is the core material of our Digital Age which still amazes us with new findings and applications. In this talk, I will introduce a series of LC-based systems under microscopy to see how the partial order of LCs gives rise to novel phenomena in a wide range of materials problems. First, I will show the confined LCs having unique elastic properties manifest unexplored topological aspects of chiral materials. In the second part, pulsating bubbles dispersed in LC reveal a critical role of spatiotemporal symmetry breaking of the anisotropic medium in the bubbles' propulsion. Extending this problem, we adopt motile bacteria in LC to study how bacteria interact with liquid-liquid interfaces. Lastly, unveiling skin formation in drying deposits of aqueous LCs and solutions, I will share my vision for future soft matter research utilizing X-ray/neutron radiography.

Bio: Joonwoo Jeong is currently an associate professor in the Department of Physics at UNIST (Ulsan National Institute of Science and Technology), Korea. He obtained his Ph.D. in Physics at KAIST (Korea Advanced Institute of Science and Technology), studying the effect of external fields on soft matter systems ranging from liquid crystals to colloids and polymers. Then, he pursued his postdoctoral research at the University of Pennsylvania from 2012 to 2014, pioneering the field of water-loving chromonic materials. Since he joined UNIST in 2015 as the principal investigator of the Experimental Soft Matter Physics Lab (SOPHY), he has expanded his research area into radiography for soft matter and statistical physics with active matter, such as lab-grown bacteria.

Abstract: Unlike crystalline solids, disordered materials live in a complex and rugged energy landscape with multiple local energy minima, each corresponding to a different state with its own set of properties. In this multitude of possibilities, the challenge is to identify states that have unusual and desirable behavior. For e.g., a jammed packing of granular particles, a quintessential disordered system, has well defined bulk properties that depend on, among other factors, the interparticle interactions. Here I present “particulated” granular metamaterials - flexible tessellations filled with a small number of particles in each cell. By limiting inter-particle interactions to individual cells of a larger system, we create a material with a rich and complex mechanical response that is unlike conventional granular packings. Another feature of disordered systems is that they are often out-of-equilibrium and evolve over time. Such a material has a memory of its history which affects its properties, including its response to external perturbations. By controlling the external forces acting on a system, we can direct a material's evolution to modify its behavior in a favorable way. We can train a material to modify and tune its elastic properties in the non-linear as well as the linear regimes without having to control the material at the microscopic level. Disordered systems thus have the potential to be the basis for creating broad classes of materials with specific functionality.

Bio: Nidhi Pashine is a postdoctoral associate in the School of Engineering and Applied Sciences at Yale University. She obtained her Ph.D. in Physics in 2021 from the University of Chicago. Nidhi is a soft matter experimentalist whose interests include mechanical metamaterials, granular systems, robotic soft materials, and memory and training in materials.

Abstract: Optical atomic clocks are some of the most precise measurement systems we have available to measure physical parameters. Based on the manipulation and control of ultracold strontium atoms, today’s atomic clocks have a precision that can resolve gravitational redshifts on the millimeter scale! Exploiting quantum entanglement in the form of spin squeezing promises to be an enabling development to improve the precision of atomic clocks beyond the standard quantum limit of unentangled atoms.

In this talk, I will describe two ideas to produce spin-squeezed states of ultracold alkaline earth atoms trapped in an optical cavity, that utilize their multilevel atomic structure. First, I will describe how to use cavity-mediated unitary interactions between multilevel atoms to produce a two-mode squeezed state, and utilize it for quantum metrology. I will discuss the robustness of this method to decoherence in the form of collective and single-particle emission of light. Second, I will describe how dissipation in the form of collective light emission into the cavity can be used to robustly produce a two-mode squeezed state with multilevel atoms. I will conclude by discussing prospects for multimode-squeezed multilevel atoms in quantum metrology.

Bio: I conduct research at the intersection of atomic, molecular and optical physics, quantum information science, and condensed matter physics. My research has included topics in quantum simulation of many-body physics with ultracold gases, variational quantum algorithms for probing quantum systems and solving combinatorial optimization problems, and quantum metrology with ultracold atoms. I completed my Masters and PhD in physics at Cornell University, did postdoctoral research with Kaden Hazzard at Rice University, Peter Zoller at the Austrian Academy of Sciences, and Ana Maria Rey at the University of Colorado, Boulder. I'm currently a research engineer working towards achieving quantum advantage at Rigetti Computing.

Abstract: Frustrated magnetism arises when spins interact through competing exchange interactions which cannot be simultaneously satisfied. When the frustrations are strong enough, exotic states can emerge such as long-range entangled spin liquids. Unfortunately, solid state materials are complicated and frustrations are hard to control: To this date, quantum spin liquids are still challenging to be realized in experiments. Naturally, researchers turn to more manageable experimental systems, in the hope of engineering frustrated magnetism constructively. I will discuss my recent works on spin liquids in two types of such manageable systems: moire heterostructures in van der Waals materials where many tuning knobs are available; and monitored quantum circuits where designer gates and measurements are exploited as new sources of frustrations.

Bio: Zhu-Xi received her B. S. in Economics at Fudan University in China. From 2014-2019 he did her Ph. D.  in physics at the University of Utah. Between 2019-2022 she was a postdoc at the Kavli Institute for Theoretical Physics, University of California, Santa Barbara. In September 2022 she joined Harvard University as a postdoc. Her research is centered around discovering, understanding, and realizing exotic states of matter.

• Livestream: youtube.com/c/thegeorgiatechobservatory
• In Person: Georgia Tech Observatory at Howey Physics Building

Lunar Eclipse Timeline for Atlanta:

• 4:09 am Tue, Nov 8    Partial Eclipse begins
• 5:16 am Tue, Nov 8    Total Eclipse begins 
  (The Earth's shadow now covers all of the Moon.)
• 5:59 am Tue, Nov 8    Maximum Eclipse    
  (Moon is closest to the center of the shadow.)
• 6:41 am Tue, Nov 8    Total Eclipse ends    
  (The Earth's shadow covers only part of the Moon.)
• 7:10 am Tue, Nov 8    The Moon sets            
  However, the Maui telescope stream will see the entire eclipse.
• 7:49 am Tue, Nov 8    Partial Eclipse ends    
  However, the Maui Aloha Telescope stream will see the entire eclipse.

Read about the Georgia Tech Aloha Telescope project in an article by The AJC.

Spring 2022 Series Schedule

Please see this page for cancellations and changes to this schedule, along with hours for each night:

If you park in a campus Visitor Lot, please pay the fee upon arrival.

The Public Night is contingent on clear weather. Potential closures and driving directions are on the official website.

Spring 2022 Series Schedule

Please see this page for cancellations and changes to this schedule, along with hours for each night:

If you park in a campus Visitor Lot, please pay the fee upon arrival.

The Public Night is contingent on clear weather. Potential closures and driving directions are on the official website.

Spring 2022 Series Schedule

Please see this page for cancellations and changes to this schedule, along with hours for each night:

If you park in a campus Visitor Lot, please pay the fee upon arrival.

The Public Night is contingent on clear weather. Potential closures and driving directions are on the official website.

Repeats every Friday through Nov. 19, 2021. A list of instructors for each Friday's seminar, along with more information, is available here. 

College of Sciences faculty, staff, graduate students, and postdocs will receive a calendar invitation for the virtual CoS Fall 2021 Plenary. Check your inbox for the BlueJeans Events link (search "CoS Fall 2021 Plenary"). The virtual event's agenda includes updates on the College's priorities, culture, business, searches, values, research, and more. An open Q&A will follow plenary presentations. Please join us!

The Center for Space Technology and Research (C-STAR), along with the ExplOrigins Group representing the Georgia Tech Astrobiology community, presents Space Science Week at Tech, a week's worth of lectures and presentations celebrating the latest information from space exploration activities. 

Friday, Feb. 12
11 a.m. The World In A Grain of Sand: What the Perseverance Rover Can Tell Us About the Geology of Mars
Speaker: Aileen Yingst, Senior Scientist, Planetary Space Institute; Co-Investigator, SHERLOC/WATSON, Perseverance Rover; Deputy Primary Investigator, MAHLI Camera, Curiosity Rover 
Registration: https://primetime.bluejeans.com/a2m/register/gpddbxfs

Wednesday/Thursday, Feb. 17-18
ExplOrigins Colloquium
5 p.m. Feb. 17 - Poster Session
10 a.m.-2 p.m. Feb. 18 - Colloquium
Registration: https://bit.ly/3cXu6Bh

Thursday, Feb. 18
2:15 p.m. NASA Mars Perseverance Landing Watch Party
Registration:  https://primetime.bluejeans.com/a2m/register/xecvbzja

Friday, Feb. 19
11 a.m. Mars+Landing Panel

• Glenn Lightsey, Professor, Aeronautics Engineering
• Frances Rivera-Hernandez, Assistant Professor, Earth and Atmospheric Sciences
• James Wray, Associate Professor, Earth and Atmospheric Sciences; Co-Investigator, HiRISE & CRISM, MRO
• Angela Dapremont, PhD Candidate, Planetary Science

Registration: https://primetime.bluejeans.com/a2m/register/buzhyshh

About the Prize

Half of the 2020 Nobel Prize in Physics was awarded to Roger Penrose for the discovery that black hole formation is a robust prediction of the general theory of relativity.

In 1957 Penrose, then a graduate student, met Georgia Tech’s late David Ritz Finkelstein in a fateful meeting that changed both men’s lives forever after. It was Finkelstein’s extension of the Schwarzschild metric which provided Penrose with an opening into general relativity and set him on the path to his 1965 discovery celebrated by this year’s prize.

The other half of the 2020 Nobel Prize in Physics was awarded jointly to Reinhard Genzel and Andrea Ghez for the discovery of — in Ghez’s words — "The Monster at the heart of the Milky Way," a black hole whose existence had been hypothesized since the early 1970s.

In order to visually observe an object that famously does not emit any light, precise measurements of stars moving in the black hole’s gravitational field had to be carried out. The independent work of Genzel and Ghez mapping the positions of these stars over many years has led to the clearest evidence yet that the center of our Milky Way galaxy contains “The Monster”, that possibly every galaxy contains a black hole, and that the environment near it looks nothing like what was expected.

Learn more: 2020 Nobel Prizes in Chemistry and Physics, Explained

Tune into the livestream of this year's pumpkin drop on Friday October 30 at 3 PM ET on Twitch: twitch.tv/gatechsps

Series Schedule

Sep.20, 8-10:30  Moon, Saturn, Mars

Oct.18, 7:30-10  Moon, Mars

Nov.15, 7-9  Moon, Mars

Dec.13, 7-9  Moon, Mars

Jan.17, 7-9  Moon, Orion Nebula

Feb.14, 7-9  Moon, Orion Nebula

March 14, 8-10:30  Moon, Orion Nebula

April11, 8:30-11  Moon, Star Cluster

If you park in a campus Visitor Lot, please pay the fee upon arrival.

The Public Night is contingent on clear weather. Potential closures and driving directions are on the official website. 

Georgia Tech faculty are helping organize the meeting. College of Engineering Professors Donald Webster and  P. K. Yeung co-chairs of the local organizing committee. Seven faculty from the College of Sciences are members of the local organizing committee

• Annalissa Bracco, School of Earth and Atmospheric Sciences
• Daniel Goldman, School of Physics
• Roman Grigoriev, School of Physics
• David Hu, Schools of Biological Sciences and Physics
• Michael Schatz, School of Physics
• Marc Weissburg, School of Biological Sciences
• Jeannette Yen, School of Biological Sciences

Georgia Tech faculty are working with colleagues from the other hosts institutions: Auburn University, Clemson University, Emory University, University of Alabama, University of Georgia, and Vanderbilt University. 

Financial support was provided by the host institutions, including Georgia Tech College of Engineering and College of Sciences.

Full information is available at the conference website. 

Important Dates

Registration Deadlines

• Early Registration Rate: on or before September 16, 2018
• Regular Registration Rate: September 17 – October 21, 2018
• On-Site Registration Rate: October 22 – November 20, 2018
• Cancellation Deadline (no registration refunds past this date): November 7, 2018

Housing

APS/DFD Hotel Block opens June 4, 2018 (See Hotels & Travel tab for more information)

Hotel's Reduced Rate Ends: October 14, 2018, or earlier if block sells out

Abstracts

Abstract Submission Deadline: August 1, 2018

Travel and Child Care

Travel Grant Application Deadline: August 1, 2018, 5:00 PM EDT

Child Care Grant Application Deadline: August 1, 2018, 5:00 PM EDT

Travel Assistance for Participants with Disabilities Deadline: August 1, 2018, 5:00 PM EDT

Gallery of Fluid Motion GFM

• GFM Posters and Video Submission Entries Must be Made by September 14, 2018
• Videos must be uploaded by October 5, 2018
• GFM Poster: Bring to meeting

Because it is organized and attended by only graduate students, postdocs, and select undergraduates, AbGradCon is an ideal venue for the next generation of career astrobiologists to form bonds, share ideas, and discuss the issues that will shape the future of the field. Take a look at the AbGradCon 2017 conference website to see what's happened in the past.

George Tan, a Ph.D. student of Amanda Stockton in the School of Chemistry and Biochemistry, chairs the AbGradCon 2018 organizing committee, comprising the following Ph.D. students and postdocs: 

               Marcus Bray                    Justin Lawrence
               Bradley Burcar                 Adriana Lozoya
               Anthony Burnetti              Kennda Lynch
               Heather Chilton               Santiago Mestre Fos
               Chase Chivers                 Marshall Seaton
               Dedra Eichstedt               Micah Schaible
               Zachary Duca                  Elizabeth Spiers
               Jennifer Farrar                 Scot Sutton
               Nicholas Kovacs              Nadia Szeinbaum

Full information is available at the AbGradCon 2018 website. View the AbGradCon 2018 program here.

This popular meeting for students is funded primarily by the NASA Astrobiology Institute. The organizers have also received support from the following:

• ACS Publications
• ELSI, Earth Life Science Institute 
• Georgia Institute of Technology
• John Templeton Foundation
• Nature Publications
• Simons Foundation

"I will talk about mental health as it affects graduate students and physicists and offer some best practices to support those who experience mental health problems," she says.  

LHCb stands for Large Hadron Collider beauty. It is a special experiment investigating the slight differences between matter and antimatter by studying a type of particle called the "beauty quark," or "b quark".

 About 700 scientists from 66 institutes and universities worldwide are involved in the experiment. Together they make up the LHCb collaboration. Collaboration members meet for a week every three months to discuss various issues concerning the science and the scientists. 

The 88th LHCb collaboration meeting, on June 11-15 2018, includes a session on early careers, gender, and diversity. Organizers have invited Andrea Welsh to participate in the session. Welsh is a Ph.D. student in the lab of School of Physics Professor Flavio Fenton.

Welsh is an advocate for mental health awareness, diversity and inclusiveness, and women in science, technology, engineering, and mathematics (STEM). 

IceCube is a neutrino observatory in the South Pole, the first detector of its kind. An international group of scientists responsible for the scientific research makes up the IceCube Collaboration. Currently, the collaboration includes more than 300 people from 49 institutions in 12 countries. It began in 1999 with the submission of the first IceCube proposal, and many of the original members are still active on the project.

The meetings will include planning, workshops, talks, and a banquet.

Ever wonder what it would be like to live and work at one of the coldest, most remote places on Earth? James Casey, Georgia Tech alumnus with a Ph.D. in Physics, and Martin Wolf can tell you all about it.

They are adjusting to life in more moderate conditions after 13 months operating the biggest and strangest telescope in the world, the IceCube Neutrino Observatory at the South Pole.

See incredible pictures of their exciting and challenging adventure, and learn what it takes to capture the almost invisible neutrino, nicknamed the ghost particle.

About the Speakers

James Casey
James Casey is from Huntsville, Alabama. Before becoming an IceCube winterover (a person who spends the winter in the South Pole) for the 2016-2017 South Pole season, James completed his Ph.D. in physics at Georgia Tech as a member of the IceCube Collaboration. For his graduate studies, his research focused on neutrinos generated in gamma-ray bursts. Besides physics, he also enjoys amateur radio, general aviation, and scuba diving.

Martin Wolf
Martin Wolf grew up in Germany and was part of the IceCube Collaboration for six years—receiving his Ph.D. in astrophysics—before becoming one of the two IceCube winterovers for the 2016-2017 South Pole season. Photography is one of his personal interests, and you can see his talent from the many wonderful photos he took while at the Pole.

This event is sponsored by IceCube and the School of Physics at Georgia Tech: https://meetings.wipac.wisc.edu/Atlanta2018/Home

Optical phenomena visible to everyone abundantly illustrate important ideas in science and mathematics. The phenomena considered include rainbows, sparkling reflections on water, green flashes, earthlight on the moon, glories, daylight, crystals, and the squint moon. The concepts include refraction, wave interference, numerical experiments, asymptotics, Regge poles, polarization singularities, conical intersections, and visual illusions.

About the Speaker
Sir Michael Berry is a theoretical physicist known for his research in the ‘borderlands’ between classical and quantum theories and ray and wave optics. His emphasis is on geometrical singularities such as ray caustics and wave vortices.

Berry discovered the geometric phase, a phase difference arising from cyclically changing conditions, with applications in many areas of wave physics, including polarisation optics, condensed matter, and self-propulsion of animals and robots.

He delights in finding the arcane in the mundane: mathematical singularities in rainbows and the dancing lines at the bottom of swimming pools; the twists and turns of a belt that underlie the quantum behaviour of identical particles; a laser pointer shone through bathroom window glass to demonstrate abstract aspects of wave interference; and oriental magic mirrors, illustrating the mathematical Laplace operator.

Berry has received numerous awards, including the Maxwell Medal and the Dirac Medal of the Institute of Physics, the Royal Society’s Royal Medal, the London Mathematical Society’s Pólya Prize, the Wolf Prize, and the Lorentz Medal. He serves on scientific committees of various institutes. He was knighted in 1996.

About the Joseph Ford Commemorative Lecture
Joseph Ford was one of the pioneers in the field of chaotic dynamics in the 1960s. He spent most of his 34-year career furthering the discipline at the Georgia Tech School of Physics. He dedicated his time between research, isupported largely by the National Science Foundation, and education, through conferences or in the classroom. This commemorative lecture is named to honor Ford's memory and influence as a scientist, teacher, and colleague in Georgia Tech and the scientific global community.

About the Speaker
Sylvester James Gates Jr. was appointed Ford Foundation Professor of Physics at Brown University in 2017. He also holds an appointment in the Department of Mathematics.

Gates first joined the Brown community in fall 2016, as an inaugural Provost Visiting Professor. Earlier, he was Distinguished University Professor, University Regents Professor, John H. Toll Professor of Physics, and Director of the Center for Particle and String Theory at the University of Maryland.

Gates received the 2011 National Medal of Science and is a member of the National Academy of Sciences, the American Academy of Arts and Sciences, and the American Philosophical Society. He is a fellow of both the American Association for the Advancement of Science and the American Physical Society.

He served on the Maryland State Board of Education and was a member of the President’s Council of Advisors on Science and Technology (PCAST). As a PCAST member, he was co-chair of the council's working group on STEM preeminence for the nation. He co-authored a report to the President: ”Prepare and Inspire K-12 Education in Science, Technology, Engineering, and Math (STEM) for America’s Future.”

About Frontiers in Science Lectures
Lectures in this series are intended to inform, engage, and inspire students, faculty, staff, and the public on developments, breakthroughs, and topics of general interest in the sciences and mathematics. Lecturers tailor their talks for nonexpert audiences.

Gates's lecture is made possible by a collaboration between the College of Computing, the College of Sciences, and the School of Physics.

For the second year in a row, Flashpoint is hosting the Innovation for All Conference. The theme for 2018 is Building a Deliberately Innovative Culture. Participants will learn how entrepreneurs, large enterprises, and educational institutions use deliberate innovation practices to avoid common failure paths and innovate reliably.

The conference will begin with a panel discussion moderated by Rich A. DeMillo, director of the Center for 21st Century Universities  at Georgia Tech.

Among the panel discussants are two faculty members from the College of Sciences: Lew Lefton and Michael Schatz. Lefton is Georgia Tech assistant vice president for research cyberinfrastructure, College of Sciences assistant dean for information technology, and School of Mathematics senior academic professional. Schatz is a professor in the School of Physics.

The conference includes a demonstration of Flashpoint techniques in a master class-type setting, with innovation teams from startups, large companies and from Georgia Tech. 

Register at http://flashpoint.co/demo-days/

The VERITAS collaboration operates four telescope arrays in southern Arizona. Researchers will discuss recent results obtained with the instruments and where the work is headed. Also to be discussed are some management items.

The CTA-US collaboration is constructing a new type of telescope at the VERITAS site for a future experiment. Researchers will discuss the status of construction and experiment planning. 

August 17, 2017, is a milestone date for astrophysics. For the first time, the LIGO and Virgo gravitational-wave observatories detected signals from the collision of two neutron stars. The powerful event shook space-time and produced a fireball of light and radiation from the formation of heavy elements.

Satellites and observatories all around the world observed the light produced by this event. For the first time, we have measured gravitational waves and light produced in the same astrophysical event.

What this discovery means for astrophysics is equivalent to the difference between looking at a black-and-white photo and watching a 3-D IMAX movie! 

The combined information of gravitational waves and light is greater than the sum of its parts. The combination allows us to learn new things about physics, the universe, and what we are made of – and perhaps explain mysteries that continue to emerge.  No one has ever been able to do this before!

The historic detection of a cataclysmic celestial collision using signals from multiple messengers signals the era of multi-messenger astrophysics. Discussing the milestone and its implications are School of Physics Professors Laura Cadonati, Nepomuk Otte, and Ignacio Taboada. School of Physics Chair and Professor Pablo Laguna will moderate the discussion. The panel discussion is part of the College of Sciences' Frontiers in Science Lecture Series. 

About Frontiers in Science Lectures

Lectures in this series are intended to inform, engage, and inspire students, faculty, staff, and the public on developments, breakthroughs, and topics of general interest in the sciences and mathematics. Lecturers tailor their talks for nonexpert audiences.

The world of quantum physics appears mysterious, even spooky, and far removed from everyday phenomena we can observe in the world around us. Especially the realm of living organisms was thought to be far too disorganized and noisy for quantum phenomena to play a role.

Recently, however, clues have been mounting that the rules governing the subatomic world may play an unexpectedly pivotal role for phenomena in biology. One particularly fascinating example of this emerging field of quantum biology is bird navigation.

Even without GPS, birds are able to travel up to thousands of miles and return to their original location, aided by a physiological magnetic compass sense. Despite having been discovered more than 50 years ago, the underlying mechanism for this “sixth sense” still remains a mystery.

Thorsten Ritz will present evidence for the idea that a quantum mechanical reaction may lie at the heart of the magnetic compass of birds and possibly other organisms.

About the Speaker 

Thorsten Ritz is a biophysicist and assistant professor in the Department of Physics and Astronomy at the University of California, Irvine. Ritz received his Diplom degree from the University of Frankfurt in 1996 and then joined Klaus Schulten’s theoretical biophysics group at the University of Illinois. He finished his Ph.D. under the direction of Schulten and Nienhaus at the University of Ulm in 2001. Ritz received a postdoctoral fellowship from the Fetzer Institute and worked in the Phillips group in the Department of Biology at Virginia Tech and with Peter Hore’s group in the Department of Physics at Oxford.

Ritz’s area of science is very broad. He has already published 13 papers at the interface of the physical and biological sciences. Currently he is interested in the assembly of protein aggregates in cells though his study of light-harvesting systems (photosynthesis). He is also interested in the effect of weak magnetic fields on biochemical reactions, in particular on photosynthesis. This route led him to study and propose a new chemical mechanism for how birds use the geomagnetic field to provide them a sense of direction. He has proposed several experiments to verify this new idea, which could solve a very fundamental problem in sensory biology.

This meeting will discuss recent advances in gravitational physics and cosmology, and the exciting future of this field following the recent direct detection of gravitational waves.

School of Physics Chair Pablo Laguna will deliver a lecture on "The Kicking of Black Holes" on July 4, 2017.

Here's a complete list of conference speakers:

Bruce Allen (Max Planck Institute)
Raphael Bousso (Berkeley)
Mihalis Dafermos (Cambridge)
Gary Gibbons (Cambridge)
Gabriela González (LSU) 
James Hartle (UCSB)
Thomas Hertog (Leuven)
Gary Horowitz (UCSB)
Theodore Jacobson (Maryland)
Renata Kallosh (Stanford)
Eiichiro Komatsu (Max Planck Institute)
Pablo Laguna (Georgia Tech)
Andrei Linde (Stanford)
Viatcheslav Mukhanov (Munich)
Hiranya Peiris (UCL)
Harald Pfeiffer (Toronto)
Frans Pretorius (Princeton)
Douglas Stanford (IAS)
Jeff Steinhauer (Technion)
Andy Strominger (Harvard)

The day will include breakfast, lunch, and coffee. 

Registration is FREE, but required. Registration deadline is May 8, 2017.

The following are the invited speakers:

• Itai Cohen, Cornell University
• Ravi Kane, Georgia Tech
• Eric Weeks, Emory University
• Alberto Fernandez-Nieves, Georgia Tech
• Khalid Salaita, Emory University

Register now: http://Soft Materials Workshop

1.3 billion years ago, two black holes inspiraled and merged, releasing a power that is 50 times that of the visible universe, in the form of gravitational waves. Since then, the waves have traveled through the Universe and reached Earth on the morning of September 14, 2015.  In this talk I will describe this groundbreaking discovery, what we have learned from it, and discuss why this is opening a new field of gravitational wave astronomy. 

In materials science, the control over the spatial arrangement of colloids in soft matter hosts
implies control over a wide variety of materials properties, ranging from the system’s rheology,
to its optics, to its catalytic activity. To direct particle assembly, colloids are often manipulated
using external fields to steer them into well-defined structures at given locations. We have
been developing alternative strategies based on fields that arise when a colloid is placed within
soft matter to form an inclusion that generates a potential field in its host. Such potential fields
allow particles to interact with each other. If the soft matter host is deformed in some way,
the potential allows the particles to interact with the global system distortion. The concept is
quite general, and applied within any medium in which distortions cost energy. We have
explored these ideas in three media: curved fluid interfaces, where particles interact with the
host interface via capillarity; confined nematic liquid crystals, where particles interact with the
host director field via elastic interactions, and deformed lipid bilayers, where particles interact
o tense membranes. These example systems have important analogies and pronounced
differences which we seek to understand and exploit.

The first terrestrial observation of gravitational waves by Advanced LIGO heralds an era of gravitational-wave astronomy. Binary systems of compact objects, such as black holes and neutron stars, are the primary sources targeted by these observatories. While Numerical Relativity (NR) has already been instrumental in shaping gravitational-wave searches, the concurrent discovery of "heavy" black hole binaries (masses ~ 30-35 Msuns) by Advanced LIGO opens up new avenues for its application to future searches. In this talk, I will discuss results from recent LIGO-Virgo searches; highlight the involvement of NR so far, and discuss some prospective NR applications to future binary black hole observations.

[1] J. Riest and G. Nägele, Short-time dynamics in dispersions with competing short-range attraction and long-range repulsion, Soft Matter 11, 9273 (2015).

[2] Collaboration with D. Godfrin (MIT), Y. Liu (NIST) and N. Wagner (UDEL), work in progress.

In this talk, I will begin by presenting our recent results on valley Zeeman effect, where in analogy to spins, valleys shift in energy with magnetic field. Next, I will discuss our theoretical results on how the non-trivial geometry of Bloch bands modifies the excitonic fine structure of TMDs resulting in an orbital Zeeman effect in reciprocal space and a Lamb-like shift of levels. Finally, I will present our recent results on the observation of microcavity polaritons confirming the strong light-matter interactions in these materials. The presence of valley degree of freedom, non-trivial geometry of bands, and the possibility of introducing non-linearities in form of quantum emitters makes polaritons in TMDs particularly appealing for studying correlated many-body physics and topological states of matter.

[1]. A. Srivastava et al., Nature Phys. 11, 141-147 (2015).
[2]. A. Srivastava et al., Nature Nanotech. 10, 491-496 (2015).
[3]. A. Srivastava and A. Imamoglu, Phys. Rev. Lett. 115, 166803 (2015).