Physics Colloquium - Fall 2021

Recent advances in wearable devices boosted demand of batteries with high energy density and excellent robustness towards mechanical stresses. We address this challenge by eliminating electrochemically inactive metal current collectors, binders and additives from Li-ion battery architecture by using self-standing electrodes, and thereby approaching the ceiling of gravimetric energy density imposed by Li-storage material. This novel solution-free electrode fabrication technology is based on in-situ mixing of as-grown pristine single-wall carbon nanotubes with aerosolized active materials in ratios that provide electrical conductivity higher than percolation value, adequate mechanical robustness under stretching ( ≤15%), bending (d≥2mm) and twisting (θ>180o) cycles. This technology eliminates the use of toxic solutions and binders from production line, and thereby allows easy recycling of the constituent materials. Moreover, it promotes the ecofriendly circular economy for batteries, which is vital in anticipation of about two million metric tons of annual battery waste generated globally by industries. As examples, I will present a wristband-shape flexible battery that powers a commercial smartwatch (3.7V, 250mAh) that operates as a heart rate monitoring sensor, as well as batteries integrated into a functional textile for powering a commercial accelerometer sensor.

Dr. Avetik R. Harutyunyan is currently a Senior Chief Scientist    and Research Director at Honda Research Institute USA Inc., (San Jose, CA). His areas of research include the studies of nanoscale materials for quantum information science (QIS) and alternative energy applications perspectives. He is an author of more than 150 scientific publications and more than 100 patents.  He is a Fellow of APS and AAAS also Elected Chairman of External Advisory Board of ECS. Harutyunyan received his B.A. degree in “Quantum Physics and Electronics” and Ph.D. in “Solid-State Physics and Mathematics”. 

Speaker:  Douglas L Tucker , Fermilab

Abstract: On August 14, 2019 the LIGO/Virgo Collaboration (LVC) detected the gravitational waves spawned by a possible neutron star-black hole merger (NSBH), a rare event which was later designated as GW190814 by the LVC team.  An extensive search for an optical counterpart --- a kilonova ---  was undertaken by the Dark Energy Survey (DES) Gravitation Wave (GW) team using two instruments located in the Chilean Andes:  the DECam imaging camera on the Blanco 4-m telescope and the Goodman spectrograph on the SOAR 4-m telescope.  I will describe the LVC detection of GW190814 and the DES-GW team’s search for its optical counterpart, the results of the search, and the lessons learned for optical follow-up of future LVC gravitational wave detections.

Space-based slitless spectroscopy capabilities on-board the Hubble Space Telescope have made it possible for us to conduct spatially-resolved studies of star formation in high redshift galaxies for the first time. The future is truly slitless, with the James Webb Space Telescope and the Nancy Grace Roman Space Telescope vastly improving and capitalizing on the scientific gains we will make with this mode of observation. I will begin by demonstrating how spatially resolved studies with the Hubble Space Telescope have allowed us to determine which galaxy size growth mechanisms dominate and how the quiescent (not forming stars) population of galaxies builds up with redshift. Subsequently, I will unveil the first spatially resolved H-Alpha emission line maps of cluster galaxies at z~1 from the GCLASS survey, made possible with the Wide Field Camera 3 G141 grism on-board the Hubble Space Telescope, revealing what they have taught us about the shutdown of star formation in galaxy clusters at this crucial epoch in the history of cosmic star formation. I will end by presenting deep spatially resolved H-Alpha emission line maps of CANDELS galaxies at z~0.5 from the CLEAR survey, made possible with the Wide Field Camera 3 G102 grism on-board the Hubble Space Telescope, and what these have unveiled on galaxy size growth via star formation at intermediate redshifts. By synthesizing the few existing spatially-resolved studies of High-Redshift Galaxies between 0.5 < z < 1.7 we now have, I will provide the first results on how star formation propagates spatially in galaxies over time.

Astrophysics research at the University of Southern Queensland (USQ) aims to improve understanding of the shared evolution of stars and their planetary systems. This is because the host star profoundly impacts the formation, evolution and habitability of their planetary system, and observing stellar magnetic activity can help us confirm and characterise exoplanets and infer the histories of planetary systems including our own. Key research projects at USQ include the Shared Skies Partnership with the University of Louisville that supports the use of Mt Kent Observatory in Queensland, Australia, for photometric observations of exoplanet transits and MINERVA-Australis radial velocity spectroscopy for the NASA TESS exoplanet survey mission. The Mt Kent site also has a new SONG stellar seismology node that can characterise exoplanet host stars. USQ participates in Australia’s GALAH galactic archaeology stellar spectroscopic survey with the 3.9m Anglo-Australian Telescope (AAT) at Siding Spring, and in the international BCool collaboration studying cool star magnetic fields, stellar activity, dynamos, winds, exoplanets around active young stars, and exoplanetary space weather. Looking to the future, stellar and exoplanet research will be combined using the AAT’s Veloce spectrograph and its forthcoming RAPTOR auxiliary telescope, and USQ has joined the international Twinkle Space Mission consortium planning a space telescope survey combining stellar and exoplanet atmosphere studies.

Speaker: Nathan de Lee, Ph.D., (Northern Kentucky University)

Abstract: The fifth incarnation of the Sloan Digital Sky Survey (SDSS-V) began observations in Fall of 2020. In this presentation, I will talk about SDSS-V and how it combines both optical and infrared spectroscopy along with a robotic fiber positioning system to create a survey the observes across the whole sky. I will focus much of my talk on the Milky Way Mapper program within SDSS-V and its goals of understanding the Milky Way and its constituent stars. The first of its major goals is to understand the history and structure of the Milky Way. Following upon work done with the APOGEE-1 and 2 surveys, the Milky Way Mapper will use approximately 6 million stars to trace out the detailed structure of the Galaxy. The second major goal is to understand stellar astrophysics. The Milky Way Mapper contains several smaller programs called cartons, whose goals cover a wide variety of stellar candidates including white dwarfs, binary stars, young stellar objects, planet hosts, asteroseismology targets and x-ray binaries. These cartons will allow us to explore all sorts of interesting topics that can only be done with a large-scale spectroscopic survey.

Speaker: Robert, Yzhe Song (CUNY Graduate Center & American Museum of Natural History)

Abstract: Gamma-ray emission can be generated from a wide variety of high-energy astrophysical phenomena, from stellar flares to pulsating neutron stars, and from interstellar clouds to the center of the Milky Way Galaxy. Entering the 13th year of its orbit around Earth, the Fermi Space Gamma-ray Telescope has been continually surveying the gamma-ray sky with its Large Area Telescope (LAT) on board. The latest Fermi source catalog contains almost 6000 sources. Yet, a lot of sources that are expected to emit gamma-rays are not detected, and only small percentages of some populations are detected. For example, solar flares are detected in gamma-rays, do other stellar flares also produce gamma-ray photons? Only 10% of pulsars discovered to date are detected in gamma-rays, do the remaining 90% emit gamma-rays too? This work aims to provide a novel technique to analyze Fermi-LAT data as we approach the point source sensitivity limit of the instrument. Detecting and characterizing gamma-ray emission from these underlying populations is important for understanding the physical processes associated with these sources. Stacking methods are used to uncover as much information as possible about populations of sources hidden in the noise, and to study the origins of the high-energy emission. In this thesis, the proposed methods are applied to varied sources such as flare stars, pulsars, globular clusters, and low-mass X-ray binaries. I will discuss general properties of the overall population, and their emission mechanisms, such as stellar auroral phenomena, inverse Compton scattering, particle acceleration, etc.

Speaker: Alex Maloney, Ph.D.

Abstract: I will describe recent progress on the relationship between quantum information theory and quantum gravity.  I will review the theoretical evidence that classical space-time geometry emerges from the entanglement of more fundamental quantum mechanical degrees of freedom, and that -- in a sense -- space-time *is* entanglement.  This evidence comes from recent advances in our understanding of quantum black holes and the holographic (AdS/CFT) correspondence.  I will also explain the sense in which black holes are the fastest scramblers of information in nature, which leads to an intriguing relationship between black hole physics, quantum chaos, and the physics of disordered systems.  This will be an expository talk: no advanced background beyond quantum mechanics and relativity will be assumed.