Physics and Astronomy Colloquia, Academic Year 2016-2017

Colloquium committee: Leonardo Rastelli (Chair),  Alexandre Abanov, Matthew Dawber, Eden Figueroa, Joanna Kiryluk, Rosalba Perna, and Dmitri Tsybychev

Coffee & Tea served at 3:45 pm.

Talk begins at 4:15 pm.

Location: Harriman 137 (bottom of square C4 on the campus map)

Movies:  To watch the recorded movies, please  read the instructions here.

Fall 2016 colloquia

Sept. 13

Chair Colloquium

Chair’s Colloquium

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Sept. 20

Brian O’Shea

Michigan State University

Better living through computation:  Exploring the first generations of galaxies with cosmological simulations
Galaxies are complicated beasts - many physical processes operate simultaneously, and over a huge range of scales in space and time. As a result, accurately modeling the formation and evolution of galaxies over the lifetime of the universe presents tremendous technical challenges. In this talk I will discuss these challenges and their solutions, and will also present results from the Renaissance Simulations - a suite of physics-rich simulations of high redshift galaxy formation done on the Blue Waters supercomputer.  These calculations, which include radiation transport and a wide variety of other physical effects, resolve virtually every halo that may possibly form stars and make a variety of predictions about the transition to metal-enriched star formation, the bulk properties of high-redshift galaxies, and the high-redshift luminosity function.
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Sept. 27

Xi Yin

Harvard University

From spin chains to quantum gravity, or how little we know about physics in one dimension

Quantum critical systems in one spatial dimension exhibit rich dynamics and connect widely different subjects, from spin chains to strings and quantum gravity. I will discuss old and new constraints on the dynamics from conformal symmetry, and highlight some questions in strong coupling quantum dynamics whose answers may be key to decrypting the holographic dictionary.
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Oct. 4

Ashoke Sen
Harish-Chandra Research Institute

Managing divergences in string theory

Quantum field theories suffer from two kinds of divergences -- infrared and ultraviolet. String theory is known to be free from ultraviolet divergences but suffers from the usual infrared divergences of quantum field theories. After briefly reviewing the absence of ultraviolet divergences in string theory, I shall describe recent progress towards understanding infrared divergences in string theory.

The colloquium will take place in the Simons Center auditorium. 

Refreshments at 3:45pm in the Simons Center lobby.
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Oct. 11

Alan Aspuru-Guzik

Harvard University

Quantum computer simulation of chemistry and materials: Advances and Perspectives

Quantum computers promise the numerically exact simulation of molecules and materials. Furthermore, they are amongst the algorithms that have the lowest resource requirements for surpassing the power of classical computers. In this talk, I will briefly introduce the basic concepts of quantum computing and quantum simulation. Then, I will review the recent rapid progress in developing more efficient algorithms that have been achieved by many researchers in the field including our research group. I will describe the families of available algorithms (phase estimation, adiabatic and variational quantum eigensolver approaches) as well as the status of several experimental implementations of them either carried out or underway. These implementations span most of the currently available quantum architectures includingquantum optics, ion traps, NV centers and superconducting quantum bits. I will provide a prelude of the relevance of these applications to society and will conclude with the prospects of the field.
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Oct. 18

Alexei Tkachenko
Brookhaven National Lab

Tales of Emerging Complexity: from Self-Assembly to Self-Replication
Self-assembly is a key phenomenon in living matter, and at the same time, a booming field of modern material science and engineering. In my talk I will review emerging  trends and ideas in this field, and give theorist's perspective on its conceptual challenges.  I will discuss the strategy of programmable self-assembly that uses molecular recognition properties of DNA to build nano- and micro-scale building blocks  with designed pairwise interactions.  This approach opens an entirely new class of theoretical problems in statistical physics. Instead of studying phenomenology of a large system of  particles with  given properties, we must solve the inverse problem: finding the interactions that would result in a self-assembly of a desired macroscopic or mesoscopic morphology. I will start with a discussion of self-assembly in a very simple binary system of spherical particles, and gradually move towards a greater complexity of both the building blocks and the resulting structures. Eventually, from the problem of programmable self-assembly we will shift to a pursue of the simplest system capable of self-replication.
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Oct. 25

Giacinto Piacquadio

Stony Brook University

What bottom quarks can tell us about the Higgs sector

After a successful first run of the Large Hadron Collider leading to the discovery of the Higgs boson, the journey towards the unknown has restarted at the highest collision energy ever produced by mankind. I will explain how Higgs boson decays to bottom quarks can be used to characterize the Higgs sector and as a tool to search for new physics; what we have learnt so far and what we may discover in the years to come.
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Nov. 1

Thomas Killian

Rice University

Studying Collisions and Transport in Strongly Coupled Systems with Ultracold Plasmas

Ultracold neutral plasmas, formed by photoionizing laser-cooled atoms near the ionization threshold, explore matter at the intersection of atomic, soft condensed matter, and plasma physics. Because of the low electron and ion temperatures (Te=1-1000K and Ti=1K), the Coulomb interaction energy per particle can exceed the thermal energy, which makes the system strongly coupled. Strong coupling is of interest in many areas of physics. It leads to spatial correlations and surprising equilibration dynamics, and it makes theoretical description much more difficult. Ultracold plasmas provide a valuable window into these phenomena because of the excellent control of initial conditions and diagnostics that are available. I will describe recent results that give the first measurement of equilibration rates [1] and diffusion coefficients in the strongly coupled regime [2], which are relevant for plasmas produced through short-pulse laser irradiation of solid targets, such as in inertial confinement fusion. The dynamics also shows non-Markovian or memory effects that are reminiscent of the behavior of metal liquids. 

This work is supported by the National Science Foundation, Department of Energy, and the Air Force Office of Scientific Research.
[1] “Velocity Relaxation in a Strongly Coupled Plasma,” G. Bannasch, J. Castro, P. McQuillen, T. Pohl and T. C. Killian, Phys. Rev. Lett. 109, 185008 (2012).
[2] “Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma,” T. S. Strickler, T. K. Langin, P. McQuillen, J. Daligault, and T. C. Killian, Phys. Rev. X 6, 021021 (2016).
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Nov. 8

Giancarlo La Camera

Stony Brook University

The elusive nature of ongoing brain activity

The human brain contains about 10^10 interconnected neurons — excitable cells that are constantly interacting with one another. Much of theoretical neuroscience has focused on understanding how sensory inputs are processed, and motor outputs are produced. However, it is well known that neurons are active even while a subject is neither actively engaged in a task, nor stimulated with external stimuli known to drive those neurons. Characterized by seemingly erratic dynamics and complex activity patterns, for decades this ongoing activity has been dismissed as noise and detrimental to neural computation. Recently it has been discovered that ongoing activity is in fact finely structured, and it resembles to various degrees the activity evoked by sensory stimulation. I will describe a recent approach to understand ongoing activity, both in terms of its structure and its involvement in perception. I will show how through mean field theory and computer simulations of networks of neurons, a unified model of ongoing activity and its relationship to stimulus-evoked activity has started to emerge, providing an explanation of many observations and a possible mechanism for the expectation of anticipated events.
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Nov. 15

David Vanderbilt

Rutgers University

The search for quantum anomalous Hall insulators

The quantum Hall effect, discovered 35 years ago, is a bizarre phenomenon in which a 2D gapped system can nevertheless carry a current. Moreover, the transverse conductivity of the system is precisely quantized in units of e^2/h.  Unfortunately, this behavior requires a strong perpendicular magnetic field, and has only been observed at low temperatures.  Work of Haldane in 1988 raised the possibility that similar physics could be observed in two-dimensional magnetic systems without any external magnetic field, and potentially at much higher temperatures.  Such a system is known as a "quantum anomalous Hall" (QAH) or "Chern" insulator. In this talk I will introduce the essential physics of the QAH effect, provide a tutorial on its mathematical description in terms of Berry phases, and briefly describe recent successes in finding low-temperature realizations.  I will then review some of our own recent work in which we propose the deposition of atoms with strong spin-orbit interactions onto the surfaces of magnetic insulators as a promising route toward the synthesis of higher-temperature QAH systems.
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Nov. 22

Adam Showman 

Arizona State University

Atmospheric circulation of hot Jupiters

Over 3500 planets have been discovered around other stars, many of which orbit extremely close-in, where they receive enormous stellar fluxes.  The intense radiation on these planets is expected to drive a vigorous atmospheric circulation that shapes the day-night temperature difference, infrared light curves, spectra, albedo, atmospheric composition, and perhaps even the long-term evolution and planetary radii.  Recent spacebased and groundbased telescope observations

exhibit extensive evidence for such circulations in the atmospheres of these planets.  This new observational vanguard opens the possibility of extending our understanding of atmospheric circulation beyond the confines of the Solar System, and it raises fundamental questions about planetary climate and habitability.  Here I will survey this exciting new field and describe recent research elucidating the dynamical mechanisms that operate to control the atmospheric circulation in these planets' atmospheres.  To emphasize the similarities as well as differences, I will ground this discussion in our understanding of the more familiar atmospheric dynamical regime of Earth, as well as our "local" giant planets Jupiter, Saturn, Uranus, and Neptune.
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Nov. 29

Nadia Fomin

University of Tennessee

Life and Death of the Free Neutron

Modern neutron sources provide extraordinary opportunities to study a wide variety of physics topics, including the physical system of the neutron itself. One of the processes under the microscope, neutron beta decay, is an archetype for all semi-leptonic charged-current weak processes. Precise measurements of the correlation parameters in neutron beta decay as well as the neutron lifetime itself are required for tests of the Standard Model and for searches of new physics. The state of the field will be presented and a program of current and future experiments and potential impacts explored.
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Dec. 6

Mark van Raamsdonk

University of British Columbia

Gravity and Entanglement
The AdS/CFT correspondence from string theory provides a quantum theory of gravity in which spacetime and gravitational physics emerge from an ordinary non-gravitational quantum system with many degrees of freedom. In this talk, I will explain how quantum entanglement between these degrees of freedom is crucial for the emergence of a classical spacetime, and describe progress in understanding how spacetime dynamics (gravitation) arises from the physics of quantum entanglement

The colloquium will take place in the Simons Center auditorium. 

Refreshments at 3:45pm in the Simons Center lobby.
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Spring 2017 colloquia

Jan. 24

Peter Capak

Transforming Cosmological Measurements Using Big Data Techniques

Current and proposed measurements of dark matter and dark energy are heavily reliant on large galaxy surveys which treat galaxies as test particles.  However, galaxies are biased test particles that systematically vary in their bias with a range of variables.  This talk will show how I have applied advanced computational (big data) techniques to characterize the galaxy population and its biases in order to optimize cosmological measurements.  Specifically, I will show applications to measuring redshifts for weak lensing cosmology and estimating emission line strengths for spectroscopic surveys.  While powerful, big data techniques are often misapplied. I will highlight the importance of understanding the underlying physics problems and working across fields to implement solutions.  I will conclude by giving an overview of the new computational tools needed to extract information from the next generations of cosmological surveys.
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Jan. 31

Kendrick Smith

Perimeter Institute

CHIME: The Canadian Hydrogen Intensity Mapping Experiment

CHIME is a new interferometric telescope at radio frequencies 400-800 MHz.  The mapping speed (or total statistical power) of CHIME is among the largest of any radio telescope in the world, and the technology powering CHIME could be used to build telescopes which are orders of magnitude more powerful.  This breakthrough sensitivity has the power to revolutionize radio astronomy, but meeting the computational challenges will require breakthroughs on the algorithmic side.  I'll give a status update on CHIME, with an emphasis on new algorithms being developed to search for fast radio bursts and pulsars.
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Feb. 7

Cinzia Da Via

University of Manchester

Radiation Detectors and Imaging Technologies

The talk will discuss how the development of radiation instrumentation has been crucial for fundamental scientific discoveries and for the improvement of human life. After a brief historic introduction there will be an overview of some of the modern technologies used in radiation imagers in various fields followed by potential future trends.
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Feb. 14

Martin Zirnbauer
Kohln University

On symmetry-protected topological states: from free fermions to the Haldane phase

The Nobel-Prize winning Haldane phase of spin-1 antiferromagnetic spin chains is a paradigm for symmetry-protected topological phases. When local charge fluctuations are allowed, there has been a debate: protection by what? My answer is that there exists an adiabatic path to a  free-fermion topological phase of class AIII, protected by a particle-hole symmetry. To set the stage, I will review Dyson’s Threefold Way and recall the Tenfold Way of disordered fermions.
The colloquium will take place in the Simons Center auditorium. 

Refreshments at 3:45pm in the Simons Center lobby.
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Feb. 21

Jack Harris
Yale University

Topological physics with a pair of oscillators: beyond Berry's phase via exceptional points

Topological phenomena appear in a number of physical systems, from exotic quantum states to carefully engineered waveguides. These phenomena offer new forms of control, and are also intriguing in their own right. I will describe a topological feature that is generically present in one of nature's simplest systems: a pair of coupled oscillators. I will describe experiments in which we demonstrate this feature and use it to achieve topological control over the vibrational modes of a mechanical oscillator. Although these effects are classical, our experiments are carried out using an optomechanical device that is also capable of detecting the membrane's quantum fluctuations. I will describe some prospects for studying the interplay of topological and quantum effects in such a system.
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Feb. 28

Peter Melchior

Princeton University

A cosmic census — and the means to do it rightWeak gravitational lensing is an important driver of large astronomical surveys. It presents the only way to determine the mass distribution in the universe over a wide range of scales: galaxies, galaxy clusters, voids, and the cosmic web as a whole. I will show the latest results of the Dark Energy Survey for each of those scales and illustrate what we learn from them about the fundamental building blocks of the universe. I will also discuss what holds us back: improper treatment of observational realities, theoretical challenges, and a widening chasm between observers and theorists. To address those, I will present new techniques for image analysis that are based in identifying the mathematical principles governing the observations, as well as collaborative efforts to bridge the gaps within the astronomical community. These approaches are interdisciplinary in nature: they draw from advances in astrophysics, mathematics, and statistics, and will enable us to fully  utilize the wealth of information in current and upcoming cosmological surveys.
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March 7

Irina Novikova
William & Mary

Cool quantum optics with hot atoms

Efficient and reliable quantum communication will require the control of the quantum state of both photons and atoms. In this talk I will discuss a possible realization of strong coupling between quantum optical field and collective spin excitation in atomic vapor via  electromagnetically induced transparency, as well as possible applications of the effect for precision metrology, quantum memory and generation of non-classical light.
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March 14

Spring Break: No classes and no colloquium

March 21

Grigory Falkovitch

Weizmann Institute

Planar flows: from graphene to planet atmospheres

Fluid mechanics in two dimensions has wide range of applications and possesses unique mathematical properties which are far from being fully explored. Even laminar and regular flows in two dimensions are of great interest ranging from microfluidics to emerging viscous electronics in graphene and other strongly interacting systems. They possess such remarkable features as negative resistance and super-ballistic conductance. On the other hand, a landmark feature of turbulence in two dimensions is an inverse cascade, that is an appearance of large vortices and jets out of multi-scale random flow. It is the most significant and most surprising discovery in turbulence in the last fifty years. We still have no adequate conceptual framework for this counter-intuitive process of self-organization. Several inverse cascades demonstrate conformal invariance, found empirically and still having no theoretical explanation. After the inverse cascade reaches the system size, it creates a coherent flow called condensate. Interaction of turbulence and condensate is presently one of the most active fields of turbulence research. Apart from fundamental importance, inverse turbulence cascades and condensates are ubiquitous features of astrophysical, geophysical and industrial flows, from planet atmospheres to tokamak plasma. This colloquium will give an elementary presentation of physical phenomena ranging from current vortices in graphene to jets and vortices in planet atmospheres
The colloquium will take place in the Simons Center auditorium. 

Refreshments at 3:45pm in the Simons Center lobby.
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March 28

Eun-Ah Kim

Cornell University

Neural network based machine learning approach to quantum condensed matter

There is rapidly growing interest in using neural network based machine learning to extract physical information out of fluctuating data, be it numerical or experimental. In this talk I will discuss our recent works demonstrating the how one can use neural network based machine learning to speed up acquisition of quantum phase  diagram with topological order. I will also discuss our recent results on detecting universal features from scanning tunneling microscopy data using neural network based machine learning.
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April 4

Eun-Suk Seo
University of Maryland

High-flying Experiments to Investigate Mysteries of Cosmic Rays

One of the most exciting possibilities in cosmic ray research is the potential to discover new phenomena. Elementary particles were discovered in cosmic rays before modern-day accelerators became available to study their detailed properties.  Since the discovery of cosmic ray antiprotons in 1979 using a balloon-borne magnet spectrometer, a series of magnet spectrometers have been flown to search for the signature of dark matter annihilation in antiprotons and positrons. Being the same as particles except for their opposite charge sign, antiparticles are readily distinguished as they bend in opposite directions in the magnetic field. As long-duration balloon flights over Antarctica became available, not only antiproton to proton ratios, but also measurements of antiproton energy spectra became possible. Furthermore, PAMELA on a Russian Satellite and AMS-02 on the International Space Station (ISS) are currently providing precision measurements of various particles and anti-particles, including positions and antiprotons. In particular, excess positrons generated a lot of excitement due to their possible explanation of dark matter. More recently, the JAXA-led CALET ISS mission and the DAMPE Chinese Satellite were launched. NASA’s ISS-CREAM was delivered to KSC to await launch by SpaceX after completing its final verification at GSFC. These missions will provide complementary measurements exploring energies higher than previously possible to constrain cosmic ray propagation models in search of dark matter and the origin of cosmic rays. Recent results, their implications, and the outlook for the field will be presented. 
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April 11

David Kawall
UMass Amherst

The Curious Case of the Muon's Anomalous Magnetic Moment

The muon has played an important role in the development of particle physics since its discovery in 1936. The muon is structureless so its properties can be predicted with impressive precision from modern particle physics theory. Interest in the muon has risen since a recent measurement at Brookhaven of the anomalous magnetic moment of the muon yielded a result which differs from expectations. The difference might be due to new physics with new particles that influence the results of the measurement but are not included in the Standard Model prediction. To help resolve this mystery, an experiment at Fermilab will improve the precision of the measurement fourfold to 140 ppb. The incredible journey by land and sea of the giant storage ring at the heart of the experiment, and the principles underlying the measurement will be described.
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April 18

Chang Kee Jung
Stony Brook University

Capturing Innovations and Underlying Physics in Sports

(Selected Topics: Basketball, High Jump, Gymnastics and Swimming)

Featuring Bedel Saget, a New York Times graphics/multimedia editor for sports

Sports occupies an important part of American life as well as other parts of the world. It is often difficult to flip through the TV channels without encountering sports shows. Surprisingly, large fraction of the intriguing and often spectacular sports actions and feats can be explained using relatively basic physics concepts. In this talk I will explain the physics behind some remarkably creative innovations in popular sports (basketball, high jump, gymnastics and swimming)  using basic concepts in college entry level classical physics. The talk will feature exquisite and exclusive videos created by the New York Times graphics/multimedia team for sports that capture  innovative feats of athletes like Simone Biles, Derek Drouin and Ryan Lochte. Just a few days after the colloquium, Bedel Saget will receive a 2nd place award for his team's work, titled, "The Fine Line: Simone Biles Gymnastics" at the prestigious 2017 World Press Photo Digital Storytelling contest in the Immersive Storytelling category.

Bedel Saget is an Emmy nominated producer, award winning photographer and video journalist with over 28 years of experience developing content for The New York Times and other news outlets like ESPN. He is currently a Sports Graphics/Multimedia Editor at The New York Times where he conceives, reports and creates interactive informational graphics and videos on as

well as the charts, maps and diagrams for the print newspaper. Saget’s work has received numerous citations and awards from the Society of News Design, the Associated Press Sports Editors (APSE) and the Malofiej international information graphics competition.
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April 25

Zohar Komargodski

Using Topology to Solve Strongly Coupled Quantum Field Theories

I will begin by describing an interacting model in Quantum Mechanics where exact results about the ground state can be established by using tools from topology. I will then argue that such tools are also useful for tackling interesting problems in Quantum Field Theory. In particular, I will review Yang-Mills theory and argue that using topology one can make several predictions about its possible phases. 

The colloquium will take place in the Simons Center auditorium. 

Refreshments at 3:45pm in the Simons Center lobby.
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May 2

Graduate Director

Graduate Awards and Summary

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