NSBP Innovate Seminar Series

Exploring Super Atomic Crystals

Super atomic crystals offer an exciting opportunity to improve materials used in technological devices including solar panels, lithium-ion batteries, and quantum computing hardware. By studying their properties, we can explore their design complexity and offer insights into their potential functionality to engineers who then have the challenge of building these materials. In my talk, I will answer these questions: What is a super atomic crystal? How do we use computational materials science techniques to discover their properties? And how can these properties potentially improve certain technologies?

About the Speaker

LaToya Anderson is an Associate Research Analyst at the Simons Foundation and a physics undergraduate at Brooklyn College.

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Tuesday, November 29, 2022 at 3:00 PM ET

The Chiral Universe

Among a handful of mysteries in the LambdaCDM paradigm of cosmology, I focus on three: Dark Matter, Baryogenesis and the origin of structure. I then provide a pedagogical introduction to Chiral Gravity and show how these three mysteries may be interconnected. I also discuss some observational windows including the inevitability of parity violation in galaxy distributions.

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Ultracool Dwarfs as Tracers for Galactic Structure and Star Formation History: Prospects with Large-Scale Surveys

Ultracool dwarfs (UCDs) are low-temperature stars and brown dwarfs with masses < 0.1 solar masses. These objects comprise > 20% of all stars in the Milky Way, and they have long lifetimes (>1 trillion years). As brown dwarfs do not fuse hydrogen, they cool down with time. This cooling provides an additional age tracer that can be exploited to characterize various galactic environments such as globular clusters. Additionally, spectral energy distributions of UCDs display strong molecular features that are sensitive to chemical abundance effects; and UCDs preserve the initial chemistry of their progenitor molecular clouds. As such, UCDs serve as unique probes of the structure, formation, and evolution of the Milky Way System. However, because of their low luminosities, UCD samples have been limited to the local volume (d < 100 pc) and have remained under-utilized as tracers for galactic structure. Deep imaging and spectroscopic surveys, particularly with space-based telescopes, provide an opportunity to find distant brown dwarfs out to >1 kpc. In this talk, I present my work on finding distant ultracool dwarfs in two HST/WFC3 parallel surveys, WISPS & 3D-HST. I demonstrate how machine learning techniques provide more robust selection than traditional index-based methods in deep spectroscopic samples, and present a sample of 164 late-M, L and T dwarfs extending to 2 kpc. With this sample, I measured population scaleheights and ages as a function of spectral class using a Monte-Carlo simulation framework that accounts for the stellar mass function, star formation history, UCD evolutionary models, galactic structure, and survey properties and selection functions. I confirm that thin disk L dwarfs are younger than late-M dwarfs due to brown dwarf cooling. I also apply this modeling technique to predict that the next generation of deep and wide-field observatories, including JWST, the Nancy Grace Roman Telescope, the Vera Rubin Observatory, Euclid, and SPHEReX, will uncover millions of UCDs throughout various environments in the Galaxy, opening up a new era for understanding the history of the Milky Way.

About the Speaker

Christian is a final-year graduate student at UC San Diego and a graduate of Morehouse College. He studies properties of low-mass stars and brown dwarfs and how they can be leveraged to understand the formation and the history of the Milky Way. He is also interested in detecting gaps in globular cluster streams as potential avenues for testing dark matter models. He is a recent winner of the NBSP Beth Brown Memorial Award.

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Thursday, September 22, 2022 at 7:00 PM ET

Geologic Mapping of Resurfacing Features on Europa

There is ample evidence to suggest that Jupiter’s moon Europa is geologically active, with previous investigations suggesting that a subset of domical features on the icy moon may be cryovolcanic in origin. Cryovolcanism, the eruption of water phases or other aqueous solutions that would otherwise be frozen solid at the normal temperature of an icy satellite’s surface, has likely played a role in the resurfacing of Europa in recent geologic time. Although several of these domes have been classified as extrusive cryovolcanic domes, they have not been extensively investigated, warranting a re-examination of cryolava domes on Europa. Here we mapped domical features characterized by their lobate shape and relatively smooth surfaces. These domes are distinct from the surrounding terrain and have been interpreted to have formed via the axisymmetric flow of viscous fluids onto Europa’s surface. Pinpointing the spatial distribution of these domes and their geologic context will provide insights into regions of recent geological activity on Europa and into Europa’s cryovolcanic evolution.

About the Speaker

Kierra Wilk is a 1st year PhD student at Brown University in the Department of Earth, Environmental, and Planetary Sciences. Prior to her graduate studies, Kierra received her Bachelor of Science in Geology with a minor in Astrobiology from Rensselaer Polytechnic Institute.

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Friday, February 4, 2022 at 5:30 PM ET

Multicomponent multiscatter capture of dark matter

In recent years, the usefulness of astrophysical objects as dark matter (DM) probes has become more and more evident, especially in view of null results from direct-detection and particle-production experiments. The potentially observable signatures of DM gravitationally trapped inside a star, or another compact astrophysical object, have been used to forecast stringent constraints on the nucleon–dark matter interaction cross section. Currently, the probes of interest are at high redshifts, Population III (Pop III) stars that form in isolation or in small numbers, in very dense DM minihalos at z ∼ 15–40, and, in our own Milky Way, neutron stars, white dwarfs, brown dwarfs, exoplanets, etc. None of these objects are truly single component and, as such, capture rates calculated with the common assumption made in the literature of single-component capture, i.e., capture of DM by multiple scatterings with one single type of nucleus inside the object, are not accurate. In this paper, we present an extension of this formalism to multicomponent objects and apply it to Pop III stars, thereby investigating the role of He in the capture rates of Pop III stars. As expected, we find that the inclusion of the heavier He nuclei leads to an enhancement of the overall capture rates, further improving the potential of Pop III stars as dark matter probes.

About the Speaker

Caleb Levy is a junior physics student at Colgate University who was born and raised in Kingston, Jamaica. Caleb currently works with Dr. Cosmin Ilie at Colgate on dark matter phenomenology in astrophysical objects and hope to study theoretical cosmology and particle theory after graduation. Caleb is also an avid music lover (currently learning Jazz piano), amateur tennis enthusiast, and lover of dogs!

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Wednesday, December 1, 2021 at 5:30 PM ET

Towards Event Horizon Scale Physics from Movies and Polarization Maps

Recent radio observations of inflowing and outflowing plasma in the vicinity of supermassive black holes are linked to plasma physics models via simulations through a methodology called “Observing” Jet/Accretion flow/Black hole (JAB) Systems. For M87, HARM jet simulations are viewed from Very Large Array (43 GHz) to Event Horizon Telescope (230 GHz) scales to replicate the observed collimation and magnetic field configuration, while serving as the basis for a semi-analytic model used to generate polarization maps and spectra. This model varies plasma content from ionic (e-p) to pair (e-e+). Emission at the observed frequency is assumed to be synchrotron radiation from electrons and positrons, whose pressure is set to relate to the local magnetic pressure through parametric prescriptions. Polarization maps and spectra are found to be observationally distinguishable through positron effects such as decreasing intrinsic circular polarization and Faraday conversion. For Sagittarius A* in our Galactic Center, we include a turbulent heating electron temperature model. Intensity map movies simulating hourly timescales show that these models can be classified into at least four types: 1.) thin, asymmetric photon ring with best fit spectrum; 2.) coronal boundary layer with thin photon ring and steep spectrum; 3.) thick photon torus with flat spectrum; and 4.) extended outflow with flat spectrum. These models may be distinguishable by the Event Horizon Telescope.

About the Speaker

Dr. Richard Anantua is a postdoctoral fellow at the Center for Astrophysics | Harvard & Smithsonian and Black Hole Initiative at Harvard. As a member of the Event Horizon Telescope Collaboration, Richard coordinates the Outreach Group and links observational features of near-horizon shadows of supermassive black holes to the plasma physics of nearby accretion disks and jets which light them up. Prior to Harvard, Richard held a postdoctoral/instructor position at U.C. Berkeley after completing his Ph.D. in Physics at Stanford under Prof. Roger Blandford and a B.S. from Yale in (Physics & Philosophy) and (Economics & Mathematics).

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Friday, October 22, 2021 at 5:30 PM EDT

Detecting Biosignatures in the Atmospheres of Gas Dwarf Planets with the James Webb Space Telescope

Exoplanets with radii between those of Earth and Neptune have stronger surface gravity than Earth, can retain a sizable hydrogen-dominated atmosphere. In contrast to gas giant planets, we call these planets gas dwarf planets. The James Webb Space Telescope (JWST) will offer unprecedented insight into these planets. Here, we investigate the detectability of ammonia (NH3, a potential biosignature) in the atmospheres of seven temperate gas dwarf planets using various JWST instruments. We use petitRADTRANS and PandExo to model planet atmospheres and simulate JWST observations under different scenarios by varying cloud conditions, mean molecular weights (MMWs), and NH3 mixing ratios. A metric is defined to quantify detection significance and provide a ranked list for JWST observations in search of biosignatures in gas dwarf planets. In this talk, I will show that it is very challenging to search for the 10.3-10.8 micron NH3 feature using eclipse spectroscopy with MIRI in the presence of photon and a systemic noise floor of 12.6 ppm for 10 eclipses. NIRISS, NIRSpec, and MIRI are feasible for transmission spectroscopy to detect NH3 features from 1.5 to 6.1 microns under optimal conditions such as a clear atmosphere and low MMWs for a number of gas dwarf planets. In this talk, I will show that searching for potential biosignatures such as NH3 is feasible with a reasonable investment of JWST time for gas dwarf planets given optimal atmospheric conditions.

About the Speaker

Caprice Phillips is a third year PhD student at The Ohio State University working with Dr. Ji Wang in the Department of Astronomy. Her research involves the detectability of potential biosignatures in the atmospheres of gas dwarf exoplanets with upcoming telescopes like JWST and Twinkle.

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Thursday, September 30, 2021 at 5:30 PM EDT

Genomics, Networks, And Computational Concepts For Polytopic SUSY Representation Theory

The mathematical topic of Supersymmetry (SUSY) is about a half century old. Yet, it still holds unsolved mysteries. Gell-Mann's 'Eight-fold Way' diagrams opened the door of discovery for the Standard Model. The analogous diagrammatic structures for SUSY are poorly understood and only now starting to be revealed. This search is presented in this talk.

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Tuesday, August 31, 2021 at 5:30 PM EDT

String Theory without Really Trying: Integrated Correlators in N=4 SO(2N) Supersymmetric Yang-Mills Theory

Outside of theoretical physics, it's hard to really understand the buzz around string theory and supersymmetry. In the past couple of decades, we've gotten quite a bit of mileage through the framework of holography, namely the Anti de Sitter/Conformal Field Theory (AdS/CFT) correspondence, where a theory of quantum gravity can be described by a purely quantum theory on its boundary. I don't know very much at all about the details of string theory, but I do know how to compute quantities in certain conformal field theories, so the audience is in luck: we will set out to compute quantities in string theory only with the conformal field theory on the boundary, so we won't need to know a thing about string theory. Specifically, we will compute integrated correlators in N=4 SO(2N) Super-Yang-Mills theory, which correspond to scattering amplitudes in the bulk supergravity theory. This is a pretty overkill method as far as ordinary quantum field theories are concerned, so we'll also see how supersymmetry can be a powerful tool for theories like QCD, which describes the strong nuclear force.

About the Speaker

Nico Cooper is a recent graduate of Princeton University, and currently a graduate student in math at Northwestern. His research has focused broadly on high energy theoretical physics, and superconformal field theories, and he has worked as a black queer activist in many capacities, recently as a member of the NSBP Student Council.

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Wednesday, June 30, 2021 at 5:30 PM EDT

A theory of Hybrid monodromy inflation with two fields

In this talk I will revisit the hybrid inflation theory first proposed by A.Linde.
In his original paper, A.Linde considers an inflationary model involving two coupled massive scalar fields. This theory fails to predict a spectral index coherent with the Planck data. I will focus on a model developed by Stewart that allows for a viable spectral tilt that fits the current data.
We will see that we can study this hybrid inflation as an effective field theory showing that its predictions agree with the Planck data. Furthermore, I will explore the quantum stability of this model and outline a possible mechanism realizing the scalars as compact axions dual to massive 4-forms.

About the Speaker

Morgane König is a sixth year PhD candidate at the University of California, Davis, whose work focuses on particle physics, cosmology and gravity theory. Upon graduation, König will be the 9th black woman to receive a PhD in theoretical physics in the USA, and the first black student to get a PhD in physics at UC Davis. König was born and raised in Paris, France where she studied the piano, classical music theory, and ballet for 10 years at the conservatoire du 5eme arrondissement. More about Morgane König at: https://morganekonig.carrd.co/.

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Thursday, April 29, 2021 at 4:00 PM EDT

Se diffusion into SrTiO3 substrate in monolayer FeSe/SrTiO3

Monolayer FeSe on a SrTiO3 (STO) substrate is a high-temperature superconductor with reported Tc as high as 100 K, but the mechanism for such enhanced Tc remains poorly understood. Samantha's research characterizes the atomic structural and chemical composition of the FeSe/STO interface using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). These measurements reveal the presence of selenium in the top layers of STO, located on interstitial sites and in the TiO2 layers. We support our measurement with density functional theory (DFT) calculations. We discuss implications of our findings on substrate-induced electron doping in the FeSe/STO heterostructure.

About the Speaker

Samantha O’Sullivan is a Junior undergraduate student at Harvard University concentrating in Physics and African-American Studies. She currently conducts research in experimental condensed matter physics at Harvard with a focus in electron microscopy of high temperature superconductors. She recently presented her research at the 2021 APS March Meeting and at NSBP's 2020 Annual Conference, where she won the award for "Best Talk in Condensed Matter". Outside of condensed matter Samantha is interested in plasma physics, and she will join Princeton's Plasma Physics Laboratory this summer to investigate tokamak edge physics. In her free time, Samantha enjoys genealogy research, running, and poetry.

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Monday, March 29, 2021 at 5:30 PM EDT

Next-Generation Simulations of The Remarkable Deaths of Massive Stars

Core-collapse supernova explosions (CCSN) are one possible fate of a massive star. Simulations of CCSNe rely on the properties of the massive star at core-collapse. As such, a critical component is the realization of realistic initial conditions. Multidimensional progenitor models can enable us to capture the chaotic nuclear shell burning occurring deep within the stellar interior. I will discuss ongoing efforts to progress our understanding of the nature of massive stars through next-generation hydrodynamic stellar models. In particular, I will present recent results of three-dimensional hydrodynamic models of massive stars evolved for the final moments before collapse. These recent results suggest that realistic 3D progenitor models can be favorable for obtaining robust models of CCSN explosions and are an important aspect of massive star explosions that must be taken into consideration. I will conclude with a brief discussion of the implications our models have for predication of multi-messenger signals from CCSNe.

About the Speaker

Carl E. Fields is a Ph.D. Candidate in the Department of Physics & Astronomy at Michigan State University working with Prof. Sean Couch. Carl's research focusses on astrophysical sources of gravitational waves, stellar nucleosynthesis, and multi-dimensional simulations of core-collapse supernova explosions and their massive star progenitors. Carl is jointly supported by the National Science Foundation and Los Alamos National Laboratory. Carl received his undergraduate degrees in Physics and Earth & Space Exploration (Astrophysics) where he worked with Prof. Frank Timmes. In 2020, Fields was award the Price Prize by Ohio State University and named to the Forbes 2021 Class of 30 under 30 for Science.

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Wednesday, January 27, 2021 at 5:30 PM EST

Axionic Dark Matter – New Search Techniques

It is well known that a light, pseudo-scalar particle called the Axion can solve several fundamental physics problems. Proposed to explain the lack of a neutron EDM, such a weakly interacting particle has the right characteristics to explain formation of galaxies, by providing the needed mass in the form of Cold Dark Matter. Additionally, there has been data collected on the decay of several radioactive nuclei suggesting the need for weakly interacting particles streaming from the sun and throughout the galaxy. This talk will review the theory behind axion particles, examples of early experimental searches and some new search techniques. The nuclei data reviewed here can provide complimentary results to any existing axion searches as well as a novel type of search that can be conducted.

About the Speaker

Dr. Carol Scarlett is an assistant professor of physics at Florida A&M University. She is involved in dark matter research as well as developing a program to use positrons to study plasmas and weak interactions. Her research group is also involved with a measure of the weak interaction cross section for a positron on a neutron.

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Tuesday, November 24, 2020 at 5:30 PM EST

Interacting Bosons in the Flat Band of an Optical Kagome Lattice

Geometric frustration of particle motion in a kagome lattice causes the single-particle band structure to exhibit a dispersion-less, flat band. Generally, frustration can cause a vast degeneracy of low-energy states, and instabilities in the presence of atomic interactions may lead to the manifestation of exotic states of matter. The kagome lattice, a pattern of vertex-sharing triangular plaquettes, offers the highest degree of frustration among two-dimensional lattice geometries. We create an optical kagome lattice by superimposing two optical triangular lattices made from laser light with commensurate wavelengths. We probe the band structure of the kagome lattice by preparing a Bose-Einstein condensate in excited Bloch states of the lattice, and then measuring the atoms’ group velocity via the atomic momentum distribution. We find that atomic interactions renormalize the kagome lattice band structure, significantly increasing the dispersion of the third band, which, according to non-interacting band theory, should be nearly flat (dispersion-less). Measurements at various lattice depths and gas densities agree quantitatively with predictions from the lattice Gross-Pitaevskii equation, which indicates that the observed band structure distortion, onset by atomic interactions, is caused by the distortion of the overall lattice potential away from the kagome geometry.
[+] https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.133001.
[+] https://arxiv.org/abs/2007.05928.

About the Speaker

Dr. Charles Brown is an experimental quantum physicist, science communicator, and champion for increased Black American representation in physics. Charles earned his B.S. with honors in physics at the University of Minnesota, Twin Cities. He also earned a Ph.D. in physics at Yale University, where he conducted experiments with superfluid helium-filled optical cavities, and magnetically levitated superfluid helium drops in vacuum. He is now a postdoctoral scholar and Ford Foundation fellow at the University of California, Berkeley. At Berkeley, he is a member of the Ultracold Atomic Physics Group, where he investigates ultracold atoms trapped in optical lattices, which offers an avenue to study a rich variety of many-body quantum physics phenomena. Charles has a long history of both empowering students - spanning the elementary through graduate levels - to pursue their STEM interests, and advocating for the interests of Black students. Charles recently wrote a widely read op-ed about Black underrepresentation in physics that appeared in Physics Today, which has been sparking important conversations regarding necessary changes in the physics community.

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Tuesday, September 29, 2020 at 5:30 PM EST

Beyond BCS Theory: Exact Model for Superconductivity and Mottness

High-temperature superconductivity in the cuprates remains an unsolved problem because the cuprates start off their lives as Mott insulators in which no organizing principle such a Fermi surface can be invoked to treat the electron interactions. Consequently, it would be advantageous to solve even a toy model that exhibits both Mottness and superconductivity. In 1992 Hatsugai and Khomoto wrote down a momentum-space model for a Mott insulator which is safe to say was largely overlooked, their paper garnering just 21 citations (6 due to our group). I will show exactly[1] that this model when appended with a weak pairing interaction exhibits not only the analogue of Cooper's instability but also a superconducting ground state, thereby demonstrating that a model for a doped Mott insulator can exhibit superconductivity. The properties of the superconducting state differ drastically from that of the standard BCS theory. The elementary excitations of this superconductor are not linear combinations of particle and hole states but rather superpositions of doublons and holons, composite excitations signaling that the superconducting ground state of the doped Mott insulator inherits the non-Fermi liquid character of the normal state. Additional unexpected features of this model are that it exhibits a superconductivity-induced transfer of spectral weight from high to low energies and a suppression of the superfluid density as seen in the cuprates.
[1] https://www.nature.com/articles/s41567-020-0988-4.

About the Speaker

Professor Philip Phillips received his bachelor's degree from Walla Walla College in 1979, and his Ph.D. from the University of Washington in 1982. After a Miller Fellowship at Berkeley, he joined the faculty at Massachusetts Institute of Technology (1984-1993). Professor Phillips came to the University of Illinois in 1993. Professor Phillips is a theoretical condensed matter physicist who has an international reputation for his work on transport in disordered and strongly correlated low-dimensional systems. He is the inventor of various models for Bose metals, Mottness, and the random dimer model, which exhibits extended states in one dimension, thereby representing an exception to the localization theorem of Anderson's.

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Thursday, August 27, 2020 at 5:30 PM EST

Observable Blueshift from Circular Equatorial Orbiters around Kerr Black Holes

With the success of the Event Horizon Telescope, identifying new observational signatures of black holes are of increasing interest. In this talk we investigate blueshift of photons from an equatorial accretion disk of emitters orbiting on stable circular orbits terminating at the ISCO.
We analytically calculate the blueshift of photons that escape to the celestial sphere (instead of falling into the black hole) and numerically calculate the maximum blueshift received by an observer at fixed angle on the celestial sphere.

About the Speaker

Delilah Gates is a graduate student in Prof. Andrew Strominger’s group studying observational signatures of high-spin black holes and near-horizon near extreme limits related to the emergent near-horizon conformal symmetry of the Kerr black hole solution.

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Tuesday, July 21, 2020 at 1:00 PM EST