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Colloquium

The colloquium is currently held at 4:30PM on Tuesdays in Harriman 137.  Cookies, Tea and Coffee are served from 4:15PM outside the lecture hall.

Colloquium committee: Marivi Fernandez-Serra (Chair), Will Farr, Dmitri Kharzeev, Rouven Essig and Giacinto Piacquadio

Archive of colloquia from 1999 to the present

Spring 2022 Colloquia
Date Speaker Title & Abstract

Feb

1

Navid Vafaei-Najafabadi

Stony Brook University

Recruiting the 4 th state of matter to miniaturize particle accelerators


Particle accelerators have been an invaluable tool for scientific discovery and research. Future discoveries in high energy physics will require significantly more energetic particles than those currently produced. However, simply scaling the current machines to higher energies is a significant challenge because of their cost as well as the required space. A fundamental limitation that dictates the size of these machines is that the peak electric field used for accelerating particles must be below the damage threshold of the accelerating structures. Using a plasma, an ensemble of ionized atoms also known as the fourth state of matter, this limitation can be circumvented. In particular, high amplitude waves can be generated in a plasma using a high-power laser or a particle beam. The resulting structures have been shown to sustain accelerating fields that are hundreds of times higher than those currently generated in particle accelerators. In this talk, I will discuss how plasma waves are particularly well suited for accelerating electrons, the status of the state-of-art research, as well as the challenges that need to be overcome for plasma-based accelerators to form the foundation of next generation of high-energy particle beams. 

Feb

8

Wendy Freedman

University of Chicago

This colloquium will be fully virtual.

Increasing Accuracy in Measurements of the Hubble Constant: Is There Evidence for New Physics?


An important and unresolved question in cosmology today is whether there is new physics that is missing from our current standard Lambda Cold Dark Matter (LCDM) model. Recent measurements of the Hubble constant, Ho -- based on Cepheids and Type Ia supernovae (SNe) -- are discrepant at the 4-5-sigma level with values of Ho inferred from measurements of fluctuations in the cosmic microwave background (CMB). The latter assumes LCDM, and the former assumes that systematics have been fully accounted for. If real, the current discrepancy could be signaling a new physical property of the universe. I will present new results based on an independent calibration of SNe Ho based on measurements of the Tip of the Red Giant Branch (TRGB). The TRGB marks the luminosity at which the core helium flash in low-mass stars occurs, and provides an excellent standard candle. Moreover, the TRGB method is less susceptible to extinction by dust, to metallicity effects, and to crowding/blending effects than Cepheid variable stars.   I will  address the current uncertainties in both the TRGB and Cepheid distance scales, the promise of upcoming James Webb Space Telescope data, as well as discuss the current tension in Ho and whether there is need for additional physics beyond the standard LCDM model.

Feb 15

Jin Koda

Stony Brook University

Increasing Accuracy in Measurements of the Hubble Constant: Is There Evidence for New Physics?


Molecular gas and molecular clouds host virtually all star formation in the local Universe, and therefore their formation and evolution are the first step leading to star formation and galaxy evolution. In this talk, I will argue for long life and evolutional timescales of molecular gas and clouds (~>100Myr), as opposed to the recently-(again)-suggested short timescales (10-30Myr), by looking at their evolution through galactic rotation, i.e., how they form and evolve through spiral arms and inter-arm regions, in the Milky Way and in nearby galaxies. Although the popular spiral density-wave theory predicts a rapid phase transition from atomic to molecular and then to atomic phases through spiral arm passages, the observed fraction of molecular gas over atomic gas remains high even in the inter-arm regions in MW-like spiral galaxies. Hence, the molecular gas and clouds are not destroyed much toward the inter-arm regions. Recent ALMA data show diverse molecular structures in the inter-arm regions of nearby galaxies, many of which contain large masses. Their formation requires very long timescales (~100Myr) just to assemble the masses. If they are destroyed quickly in the short timescales, their formation would not catch up with the destruction; the galaxies should have much more atomic gas than the observed. The long life and evolutional timescale of molecular gas impacts the picture of star formation - the star formation has to be triggered in the long-existing molecular structures, rather than starting at an onset of gravitational collapse from diffuse atomic gas to dense molecular clouds.

Until August 14, 2022, a recording of this colloquium may be accessed here, using the following passcode:
91.?S1YD

Feb 22

Murray Holland

University of Colorado Boulder

Extreme sensing, clocks, and squeezing atoms and molecules with light


I will describe recent ideas for lowering the temperature of ensembles of ultracold atoms and molecules into the extreme quantum regime, for using interactions to entangle atoms and molecules into non-classical quantum states, and for using these non-classical states to realize quantum advantages for metrology, clocks, and matter-wave interferometry. One such topic is a new experimentally demonstrated idea for laser cooling by Sawtooth Wave Adiabatic Passage (SWAP). This is mostly relevant to atoms and molecules that possess narrow linewidth transitions, such as the ultranarrow clock transitions, and promises to be an important extension to the toolbox of AMO physics for laser cooling and trapping. We are exploring ways to use optical cavities and cavity-mediated interactions to entangle atoms so that we may improve optical clock performance, make repeated quantum measurements beyond the standard quantum limit, and continuously track squeezed quantum phases. These approaches take full advantage of the powerful combination of the extreme optical coherence that is possible using atomic clocks, with the rich possibilities offered by many-body physics that arises when the atoms interact strongly. Atomic clocks have already progressed to the point that understanding how to take advantage of quantum effects will be crucial in order to progress to the next generation of devices.

Until August 21, 2022, a recording of this colloquium may be accessed here, using the following passcode:
=3V&hEVn

Mar 1

 

 No colloquium.

Mar 8

Laura Cadonati

Georgia Institute of Technology

Exploring the cosmic graveyard with gravitational waves


A new era in astrophysics has begun with the 2015 discovery of gravitational waves from the collision of two black holes in data from the Laser Interferometer Gravitational-wave Observatory (LIGO). The additional 2017 LIGO-Virgo detection of gravitational waves from the collision of two neutron stars in coincidence with a gamma ray burst and a kilonova, elevated multi-messenger astrophysics from concept to tool for discovery and exploration. Many more gravitational wave signals have been observed since then from collisions of compact binary coalescence, and gravitational waves are a new, important probe for understanding the universe, with a rich science potential ranging from astronomy to cosmology to nuclear physics. This talk will present a selection of the  latest results from LIGO and Virgo, with their GWTC-3 gravitational wave transient catalog, and an outlook for the next decade.

Mar 22

Alexandra Gade

Michigan State University

This colloquium will be fully virtual.

The science of FRIB: From the nuclear many-body challenge to the origin of the elements in the Universe


There are approximately 300 stable and 3,000 known unstable (rare) isotopes. Estimates are that over 7,000 different isotopes are bound by the nuclear force. It is now recognized that the properties of many yet undiscovered rare isotopes hold the key to understanding how to develop a comprehensive and predictive model of atomic nuclei, to accurately model a variety of astrophysical environments, and to understand the origin and history of elements in the Universe. Some of these isotopes also offer the possibility to study nature's underlying fundamental symmetries and to explore new societal applications of rare isotopes. This presentation will give a glimpse of the opportunities that arise once the Facility for Rare Isotope Beams (FRIB) comes online at Michigan State University in a few weeks.

Until September 18, 2022, a recording of this colloquium may be accessed here, using the following passcode:
&n5*qKQK

Mar 29

Dmitry Tsybychev

Stony Brook University

Experimental studies of the electroweak symmetry breaking at CERN Large Hadron Collider


Understanding of electroweak symmetry breaking mechanism is one of the highest priority problems facing the field of high-energy physics and most importantly whether such breaking occurs solely through the weak interactions. The divergence of electroweak interactions in the Standard Model of particle physics, in particular, scattering of longitudinally polarized of heavy gauge bosons, at the TeV scale is solved by introduction of a Higgs boson. We will present studies of the electroweak symmetry breaking at ATLAS experiment at the Large Hadron Collider (LHC), operating at center-of-mass energies of 7-14 TeV, the highest collision energy in the world.

Until September 25, 2022, a recording of this colloquium may be accessed here, using the following passcode:
d?n9qHse

Apr 5

Heather Gray

Berkeley

Computing Challenges for Future Colliders — could quantum computing play a role?


High-energy physics is facing a daunting computing challenge with the large and complex datasets expected from the HL-LHC in the next decade and future colliders to follow the LHC. The landscape of computing has been evolving rapidly and field of quantum computing in particular has been making dramatic progress in recent years. I will outline the challenges facing high-energy physics, provide a brief introduction to quantum computing focusing on recent progress and discuss recent work that may lead to solutions for high-energy physics.

Apr 12

Dave Kawalll

University of Massachusetts

An Anomaly in an Anomaly? First Results from the Fermilab Muon g-2 Experiment


The Fermilab muon g-2 experiment recently released its first measurement of the magnetic behavior of the muon. Muons are like electrons, but heavier and short-lived. Their magnetic properties can be predicted with impressive, sub-ppm precision through the techniques of quantum field theory. An interesting feature is that an accurate prediction requires the addition of quantum corrections that arise due the interactions of the muon with all the other fundamental particles of nature such as electrons, photons, quarks, etc. Comparison of experimental results with theoretical predictions then serves as a powerful test of the completeness of the Standard Model of nature, and the long-standing discrepancy we observe might indicate the need for new physics. The concepts behind the Fermilab experiment and the many challenges it faces will be presented, along with the comparison with theory and future prospects.

Until October 9, 2022, a recording of this colloquium may be accessed here, using the following passcode:
CyYyXU$0

Apr 19

Mark Palmer

Brookhaven National Laboratory

An Energy Frontier Muon Collider: Progress Towards a Machine to Drive Particle Physics Discovery


Muon colliders offer a unique path to multi-TeV, high-luminosity lepton collisions. Muon collisions with a center-of-mass energy of 10 TeV or above would offer significant discovery potential where the constituent collision energies exceed those of the LHC program by an order of magnitude. Significant progress on the fundamental R&D and design concepts for such a machine has led to a new international effort to assemble a conceptual design within the next few years. This effort will assess the viability of such a machine as a successor to the LHC program. The remaining challenges and the R&D required to deliver a complete machine description will be described.

Until October 16, 2022, a recording of this colloquium may be accessed here, using the following passcode:
b*&J29Z8

Apr 26

John Wilkerson

University of North Carolina

This colloquium will be fully virtual.

Probing the elusive nature of neutrinos


Neutrinos, enigmatic fundamental particles, were long assumed to be massless until a series of revolutionary experiments over the past two decades revealed that they actually exhibit complex behavior and must possess non-zero mass. From these and other recent measurements we know that neutrinos have minuscule masses, at least 500,000 times lighter than the electron. Yet we still do not know the neutrino’s actual mass nor why it is so light? Nor do we understand their fundamental nature, are they Dirac or Majorana particles? If neutrinos are their own antiparticles, Majorana neutrinos, then this would provide an explanation for their elusive lightness while at the same time offering a potential explanation of the universe’s observed matter - antimatter asymmetry. This talk will briefly review our current understanding of neutrinos, their role in cosmology, astrophysics, and fundamental interactions, and then address the questions of both how one “weighs” a neutrino and how to determine its Dirac or Majorana nature. The techniques and latest results from cosmology, direct kinematical methods, and double beta decay will be presented.

Until October 23, 2022, a recording of this colloquium may be accessed here, using the following passcode:
H4Uq.v$1

May 3

Matthew Dawber

Stony Brook University

Graduate Colloquium

Fall 2021 Colloquia

Date

Speaker

Title & Abstract

Aug 31

Matthew Dawber

Stony Brook University 

Building better functional materials with advanced deposition and x-ray diffraction

If the oft-quoted maxim in materials design is that “the whole is more than the sum of the parts”, it is also true that “the devil is in the details”.  In the case of ferroelectric oxides, this is especially true. Our work in building artificially layered heterostructure of these materials has shown that their key functional properties, including the nanoscale arrangement of electrical polarization and their ability to act as photocatalysts to generate hydrogen fuel, are determined by events that occur during their fabrication. They also depend strongly on tiny details such as the precise arrangement of atoms on their surfaces. Hence we will add to our list of handily appropriate sayings, “the journey is as important as the destination”. 
Historically, the approach to material fabrication has largely been like taking a red-eye with your eyeshades on, you know where you started and where you land, but have very little idea about what happened in between. (It’s also pretty tedious and uncomfortable). 
Through the use of synchrotron x-ray diffraction performed in-situ during growth and other dynamic processes we have begun to peel off the eyeshades, learning a great deal about the processes and also developing insight into how we can influence the processes at key points to greatly enhance the final properties of our materials. It’s a bit like being awake when the meal cart goes by, i.e., very much to your advantage!  

Sept 7

Chang Kee Jung

Stony Brook University

Chairs Colloquium


 

Sept 14

Gregory Falkovich

Weizmann Institute

Physical Nature of Information

How much can we do and say about something we do not know? Trying to answer this question quantitatively brought us thermodynamics, statistical mechanics and information theory. I shall present a brief history of these developments, emphasizing the analogies in the limits imposed by uncertainty on engines, measurements, communications and computations. The review is panoramic aiming to show that the people working on quantum computers and the entropy of black holes use the same tools as those designing self-driving cars and market strategies, studying molecular biology, animal behavior and human languages, and figuring out how the brain works. I’ll finish with some recent applications to turbulence as an ultimate far-from-equilibrium state with the lowest entropy.
 

October 19

Xiaoxing Xi

Temple University

Crackdown on Academic Collaboration with China Harms American Science

Academic collaboration with China was once encouraged by the US government and universities. As tension between the two countries rises rapidly, those who did, especially scientists of Chinese descent, are under heightened scrutiny by the federal government. Law enforcement officials consider collaborating with Chinese colleagues “by definition conveying sensitive information to the Chinese.” In 2015, I became a casualty of this campaign despite being innocent. “China Initiative” established by the Justice Department in 2018 has resulted in numerous prosecutions of university professors for alleged failure to disclose China ties. In this talk, I argue that academic decoupling is not in America’s interest. It is a tall order to convince the public and policy makers of this fact, but the scientific community must try lest the American leadership in science and technology will be irreparably damaged.

 

November 2

Angela Kelly

Stony Brook University

Access and Equity in the Physics Education Pipeline

Science, technology, engineering, and mathematics (STEM) careers have traditionally served as mechanisms for socioeconomic advancement in the U.S., yet participation in academic coursework that prepares students for the STEM workforce has not been equitable. Recent calls for reform in physics education have highlighted persistent disparities in access and equity for traditionally underrepresented populations in precollege and university settings. The Institute for STEM Education (I-STEM) at Stony Brook houses the Ph.D. Program in Science Education, where faculty and researchers examine important questions related to STEM educational outcomes. This  colloquium  will present recent research exploring three main segments of the physics education pipeline: (1) physics educational opportunities, participation, and teacher quality in high school settings; (2) science academic gatekeeping in community colleges; and (3) undergraduate experiences in physics, particularly remote laboratory classes. Findings utilizing a variety of research methodologies will be presented, along with implications for policy and practice in physics education.  

November 9

Sergey Syritsyn

Stony Brook University

A more perfect Universe: the role of lattice QCD in constraining fundamental symmetry violations

Violations of fundamental symmetries, in particular CP(charge*parity) and baryon number conservation, are immensely important to understanding the origin of matter in the Universe. Evidence for such violations, such as proton decay, neutron-antineutron oscillation, and the neutron electric dipole moment, have not yet been observed despite decades of dedicated experiments. In these searches, the common "probes" are protons and neutrons. Precise knowledge of their structure in terms of their elementary constituents, quarks and gluons, is crucial to connecting experimental bounds to theories incorporating symmetry violations. In my talk, I will review the role, the methods, and the status of Quantum Chromodynamics calculations on a lattice that connects quark-gluon interactions and nucleon structure.

November 16

Anja von der Linden

Stony Brook University

Cosmology with Galaxy Clusters

The observed number of galaxy clusters provides a sensitive probe of the structure of the Universe, including dark energy, by measuring the evolution of the halo mass function. However, already current cluster surveys are systematically limited by uncertainties in the relation between cluster mass and observables (e.g. number of galaxies, X-ray luminosity, or the imprint on the Cosmic Microwave Background). I will discuss the challenges in determining mass-observable relations, and how the combination of weak gravitational lensing and X-ray observations can address these. I will review current cluster cosmology results, including those from the "Weighing the Giants" project which placed some of the tightest single-probe constraints on dark energy to date. I will comment on how cluster triaxiality and orientation bias can alleviate the surprisingly low matter density inferred from clusters in the Dark Energy Survey. I will conclude with an outlook towards cluster cosmology with future sky surveys, in particular the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST).

November 30

Xijie Wang

SLAC

Watch water molecules dancing with MeV electrons
 

Water is one of the most important, yet least understood, liquids in nature. Many strange properties of liquid water, such the highest density at 39 degrees Fahrenheit and high surface tension, originate from its well-connected hydrogen bond network. A complete unveiling of the intermolecular dynamics of water requires direct time- and structure-resolved measurements. It is a challenge to  use X-ray or  neutron scattering to study water’s hydrogen bond structure dynamics due to the lacking in scattering sensitivity (X-ray) or time resolution (neutron).  Recent developments in  megaelectronvolt electron ultrafast electron diffraction (MeV-UED) [1-3] made it possible, for the first time, watching water molecule  interacts with its neighbors [4] and formation of the short-lived hydroxyl-hydronium pair of the ionized water molecule [5].  Our experiment directly observed the quantum mechanical nature of how the hydrogen atoms are spaced out, and this quantum effect could be the missing link in theoretical models describing strange properties of water. I will also discuss development of MeV-UED - a new paradigm in ultrafast electron scattering.