The David and Edith Harris Physics Colloquium Series

FALL 2019 Schedule

Thursdays // Socials: 3:30pm in 4-349 (Pappalardo Room) // Talk: 4:00pm in 10-250 (unless otherwise noted)

SEPTEMBER 5, 2019
JOHN PARMENTOLA
Adjunct Staff at RAND Corporation
Host: Robert Jaffe

Physics in the Interest of Society Lecture

"The Great Mystery of Economic Growth"

This talk challenges commonly held beliefs about economic growth by identifying what actually causes it, how the cause created technology revolutions, how it enabled the U.S. to become the world economic and military power after World War II, how the decline in the support of it through a change in our national culture should be of concern to all of us, and ultimately, how to continue prosperity for future generations.

The content of the talk does not express the views of RAND Corporation and are solely mine.

SEPTEMBER 12, 2019
MARK VOGELSBERGER
MIT
Host: Robert Simcoe

"Exploring the Universe with Cosmological Simulations"

Over the last decades, cosmological supercomputer simulations have emerged as a crucial theoretical framework and tool to study the formation of structures and galaxies in the Universe. Such simulations can now predict a plethora of properties of galaxies that agree remarkably well with observational data, and they, therefore, provide an ideal testbed for exploring theoretical models of galaxy formation. In my talk, I will highlight the enormous progress of this field over the last years and present the methods and predictions of these simulations. I will focus on the Illustris simulation and the novel IllustrisTNG project currently representing the largest and most detailed galaxy formation simulations. After demonstrating the success of galaxy formation theories and simulations, I will discuss their limitations and directions for further improvements over the next couple of years.

SEPTEMBER 19, 2019
DAN MARRONE
University of Arizona
Host: Salvatore Vitale & Scott Hughes

"The Black Hole Shadow in M87"

The Event Horizon Telescope (EHT) is an international collaboration to observe black holes at horizon-scale resolution. The EHT uses the technique of very long baseline interferometry (VLBI) and submillimeter telescopes all over the globe to perform VLBI experiments at 1mm wavelength, where we expect to resolve the event horizons of two targets, M87* and SgrA*. In 2017, the EHT performed its first experiment, using eight observatories at six geographic locations. In this talk I will report on the first results from that experiment, the image of the nuclear black hole in M87. From these data we have improved our understanding of this source, estimated its mass, and attempted a new test of General Relativity. I will also describe the path to these results and the next steps for this project.

SEPTEMBER 26, 2019
YEN-JIE LEE
MIT
Host: Bolek Wyslouch

"Probing the Trillion Degree Quark Soup"

Quantum Chromodynamics (QCD) is a complete theory of the strong interaction. However, generally, calculations with QCD are notoriously difficult. In particular, the phases of quark matter are poorly understood. Predicted by lattice QCD calculations, the Quark-Gluon Plasma can be created in relativistic heavy-ion collisions. This strongly interacting quantum liquid, first discovered at the Relativistic Heavy Ion Collider (RHIC), was found to flow more freely than any other known fluid with charged particle angular correlation analyses.

To go beyond the studies of the debris of the QGP, we can study the passage of color charged particles through this fascinating medium. One studies heavy-ion collisions which produce not only the QGP but also heavy quarks, energetic gluons, and quarks by chance. High energy quarks and gluons lose energy by radiating gluons or by colliding with the other quarks and gluons as they traverse through the QGP, a phenomenon often referred to as “Jet Quenching”. The slow-moving heavy quarks, which are interacting with the QGP strongly, open a window to the study of in-medium color force.

In this talk, I will review the most striking observations made in recent data collected by the Compact Muon Solenoid detector at the Large Hadron Collider and the properties of the QGP fluid extracted from these measurements.

OCTOBER 3, 2019
NICK GIORDANO
Auburn University
Host: Greg Fiete

"Physics of Wind Musical Instruments"

The application of basic physics principles to understand musical instruments has a long and interesting history, involving such well known physicists as Helmholtz and Raman. We are now at a point where, with the use of high performance computing, we can apply the fundamental equations of mechanics to calculate the sound produced by realistic models of musical instruments. Wind instruments provide the greatest challenge since they require the application of the Navier-Stokes equations, a set of nonlinear partial differential equations. In this talk I describe the application of the Navier-Stokes equations to the modeling of wind instruments including the recorder, the flute, and the trumpet, and discuss the kinds of insights that can be gained from this kind of modeling.

OCTOBER 10, 2019
JOSEPH FORMAGGIO
MIT
Host: Peter Fisher

"Weighing Neutrinos"

Neutrino oscillation experiments performed throughout the latter half of the twentieth century have yielded valuable information about the nature of neutrinos. The data gathered has provided the first positive evidence for neutrinos having mass, the first alteration of the Standard Model. Yet, the mass scale of neutrinos continues to be experimentally elusive. My talk will present the most recent results from the Karlsruhe Neutrino mass experiment (KATRIN), an experiment designed to measure the mass of the neutrino directly. I will also discuss future efforts to measure the mass scale of neutrinos.

OCTOBER 17, 2019
ELIOT QUATAERT
UC Berkeley
Host: Peter Fisher

PAPPALARDO FELLOWSHIPS IN PHYSICS LECTURE

"Neutron Star Mergers, Gravitational Waves and the Origin of the Elements"

The discovery of compact object mergers by LIGO has opened up a new window into the Universe's most exotic objects, neutron stars and black holes. Maximizing the scientific return of this new window requires connecting gravitational wave detections to the wealth of electromagnetic data on similar sources. I will describe the remarkable progress in this direction with the first neutron star merger detected in August 2017, emphasizing the simple underlying physics behind these discoveries. I will also look ahead to some of the diversity that may be expected in the joint electromagnetic-gravitational wave sky.

OCTOBER 24, 2019
HAIYAN GAO
Duke University
Host: Phiala Shanahan

"The Proton Remains Puzzling"

Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99% of the visible matter in the universe. Despite decades of efforts in studying its internal structure, there are still a number of puzzles surrounding the proton such as its spin, mass, and charge radius. While major progress has been made in the last three decades in understanding the proton spin "crisis'', which originated in the late 1980s by the European Muon Collaboration experiment, the nature of proton spin remains puzzling. Another proton puzzle developed in recent years concerns the proton charge radius. The ultrahigh precise value of the proton charge radius determined from muonic hydrogen Lamb shift measurements is significantly smaller than the values determined from electron-proton scattering experiments and the CODATA value of the hydrogen spectroscopy measurements. In this talk I will introduce the proton spin, mass puzzle first, and then focus on the proton charge radius, the PRad experiment at Jefferson Lab and its result on the proton charge radius.

OCTOBER 31, 2019
ALEKSANDRA WALCZAK
CNRS and ENS, Paris
Host: Leonid Levitov and Arup Chakraborty

"Prediction in immune repertoires"

Living systems often attempt to calculate and predict the future state of the environment. Given the stochastic nature of many biological systems how is that possible? I will show that even a system as complicated as the immune system has reproducible observables. Yet predicting the future state of a complex environment requires weighing the trust in new observations against prior experiences. In this light, I will present a view of the adaptive immune system as a dynamic Bayesian machinery that updates its memory repertoire by balancing evidence from new pathogen encounters against past experience of infection to predict and prepare for future threats.

NOVEMBER 7, 2019
ERWIN FREY
Arnold-Sommerfeld-Center, LMU Munich.
Host: Nikta Fakhri

"Emergence and Self-Organization in Biological Systems"

Isolated systems tend to evolve towards thermal equilibrium, a special state that has been a research focus in physics for more than a century. By contrast, most processes studied in biological systems are driven and far from thermal equilibrium. A fundamental overarching hallmark of all these processes is the emergence of structure, order, and information, and we are facing the major challenge to identify the underlying physical principles. Two particular exciting problems are the self-organised formation of functional spatio-temporal patterns in cells and the robust self-assembly of complex structures. In both fields there are recent advances in understanding the underlying physics that will be reviewed in this talk. In reaction-diffusion systems, it has been shown that the essential dynamics is the spatial redistribution of the conserved quantities which leads to moving equilibria. This has led to new insights into the robustness and evolvability of biochemical networks driving biological patterns. Efficient self-assembly of macromolecules and protein clusters is a vital challenge for living organisms: Not only are resources limited but also are malfunctioning aggregates a substantial threat to the organism itself. We will discuss recent advances in this field, in particular the role of stochastic effects and broken detailed balance.

NOVEMBER 14, 2019
ALLAN MACDONALD
University of Texas, Austin
Host: Long Ju

"Electrons, Holes, and Photons in Two-Dimensional Materials"

The properties of electron-hole pair (exciton) condensates are closely analogous to those of superconducting electron-electron pair condensates. Over the years experimental studies of exciton condensation have often been controversial, partly because the electrons and holes are typically induced by optical pumping that can drive the system far from equilibrium. I will speak about recent progress in understanding the properties of electrically controlled equilibrium or quasi-equilibrium electron-hole fluids formed in two-dimensional semiconducting materials, and about prospects for creating new coherent coupled light-matter states when two-dimensional semiconductors are placed in a planar optical cavity.

NOVEMBER 21, 2019
UWE-JENS WIESE
Institute for Theoretical Physics; Albert Einstein Center for Fundamental Physics University of Bern
Host: William Detmold and Phiala Shanahan

"Quantum Simulation of Abelian and non-Abelian Gauge Theories"

Strongly coupled gauge theories play an important role in different areas of physics. Quantum Chromodynamics (QCD) is the non-Abelian SU(3) gauge theory that describes the strong interactions between quarks and gluons in particle physics. Some strongly correlated electron systems in condensed matter physics are described by Abelian U(1) gauge theories, and the toric code, a quantum information storage device, is an Abelian Z(2) gauge theory. Many non-trivial aspects of gauge theories are accessible to accurate numerical simulations on classical computers. However, at high fermion density or in out-of-equilibrium situations such simulations suffer from notorious sign problems that prevent the importance sampling underlying Monte Carlo calculations. Quantum simulators are accurately controllable quantum devices that mimic other quantum systems. They do not suffer from sign problems, because their hardware is intrinsically quantum mechanical. For example, trapped ions that follow a laser-driven stroboscopic discrete time evolution through a sequence of quantum gate operations, have been used as a digital quantum simulator for particle-anti-particle pair creation. Analog quantum simulators, on the other hand, follow the continuous time-evolution of a tunable model Hamiltonian. Using ultra-cold atoms in optical lattices, analog quantum simulators have been designed for Abelian and non-Abelian gauge theories. Their experimental realization is a challenge for the foreseeable future, which holds the promise to access the real-time dynamics of string breaking, the out-of-equilibrium decay of a false vacuum, or the evolution of a chiral condensate after a quench, from first principles. Quantum link models which realize gauge theories including QCD, not with classical fields but with discrete quantum degrees of freedom, are ideally suited for implementation in ultracold quantum matter. For example, the nuclear spin of alkaline-earth atoms can be used to embody the SU(3) color degrees of freedom of quarks and gluons. SU(3) quantum spin ladders are closely related condensed matter systems which can be quantum simulated in a similar manner.

DECEMBER 5, 2019
IBRAHIM CISSÉ
MIT
Host: Mehran Kardar

"Super-resolution imaging of transcription in living cells"

We will discuss the latest efforts in our laboratory to develop highly sensitive methods of microscopy, to go directly inside living cells and uncover the behavior of single biomolecules as they effect their function in transcription. Transcription is the first step in gene expression regulation, during which genetic information on DNA is decoded into RNA transcripts. Methodologically, the so-called live cell single molecule and super-resolution techniques – that break the optical diffraction limit– are revealing with unprecedented spatial and temporal resolutions, novel emergent phenomena inside the living cells. We will discuss our recent discoveries on highly dynamic biomolecular clustering, and phase transitions in vivo. These discoveries are challenging the ‘textbook view’ on how our genome (DNA) is decoded in living cells.

Last updated on July 15, 2020 11:59 AM