Physics and Astronomy Colloquium 2017-2018

Thursdays, 4:00-5:00 pm

1-434 Physics and Astronomy (map)

Reception from 3:30-4:00 p.m.
(unless otherwise posted)

For more information, contact Jay Hauser


Fall 2017


Thursday, October 5, 2017

APS Bridge Program: Changing the Face of Physics Graduate Education

Theodore Hodapp

American Physical Society (APS)


In nearly every science, math, and engineering field there is a significant falloff in participation by underrepresented minority (URM) students who fail to make the transition between undergraduate and graduate studies.  The American Physical Society (APS) has realized that a professional society can erase this gap by acting as a national recruiter of URM physics students and connecting these individuals with graduate programs that are eager to a) attract motivated students to their program, b) increase domestic student participation, and c) improve the diversity of their program.  Now in its fifth year the APS has placed enough students into graduate programs nationwide to eliminate this achievement gap.  The program has low costs, is popular among graduate programs, and has inspired other departments to adopt practices that improve graduate admissions and student retention. This presentation will review project activities, present data that demonstrate effectiveness, and discuss future actions.

This material is based upon work supported in part by the National Science Foundation under Grant No. (NSF-1143070).


Thursday, October 12, 2017 - 4:00pm to 5:00pm

Searches for new TeV resonances decaying to electroweak bosons with the CMS detector at the highest LHC energies

Michalis Bachtis

University of California, Los Angeles


After the discovery of the Higgs boson in 2012, the priority of the experiments at CERN’s large hadron collider is to search directly for new physics beyond the Standard Model at the highest energies attainable. The current data-taking at  the LHC is at a center of mass energy of 13 TeV, about 1.6 times higher than in 2012, and has been extremely successful with twice as many proton collisions already recorded. This opens new frontiers in both energy and intensity enabling searches for heavy new particles with masses of several  TeV, more than ten times heavier than the heaviest known elementary particle, the top quark. Meanwhile, precision measurements of Standard Model processes indicate that searching mass scales at least this high is probably required to find new physics. My group’s latest results using the full dataset of the Compact Muon Solenoid experiment will be presented along with an overview of my group’s plans for upgrading the capabilities of the CMS detector that are essential to maintain good quality physics output in even higher beam intensities.


Thursday, October 19, 2017


Thursday, October 26, 2017 - 4:00pm to 5:00pm

Seeking ultra-high energy neutrinos in Antarctica with the radio detection technique

Amy Connolly

The Ohio State University


Ultra-high energy neutrinos ($>10^{18}$~eV) are uniquely capable of probing the most energetic astrophysics sources at cosmic distances, and fundamental physics at center-of-mass energies beyond what is probed by current particle accelerators.  The IceCube Neutrino Observatory at South Pole has announced the first measurements of a neutrino flux of astrophysical origin up to approximately $10^{15}$~eV through an optical signature.  In the last two decades, the radio technique has emerged as the most promising way to detect enough neutrinos in the UHE regime to extract the wealth of information that they carry about astrophysics and particle physics. I will present the latest developments in the field in terms of the experiments, analytical techniques and theoretical groundwork that are bringing us ever closer to the era of UHE neutrino astronomy.  I will also present some first attempts to study the radio sky with our antenna arrays, and I will also introduce some new ideas that our group at OSU is developing to use genetic algorithms in both the design of our projects and in data analysis.  

Thursday, November 2, 2017 - 4:00pm to 5:00pm

Ultrashort meets Ultracold (in the Ultraviolet)

Wesley Campbell

University of California, Los Angeles


By using narrow-band lasers to damp atomic motion, samples of atoms and a few molecules can be produced routinely at sub-millikelvin temperatures. These "ultracold" atoms can be used as quantum sensors, simulators of quantum many-body physics, and precision probes of fundamental physics.  Likewise, "ultrashort" pulse broadband lasers have been employed to study vibrational and electronic motion on extremely short timescales.  The contrast between the spectral widths (or, equivalently, timescales) of these two types of lasers has largely led to the development of separate ultracold and ultrashort communities.  However, progress in merging these two fields has already yielded some unexpected advances, and new work along these lines shows further promise.  Among the surprises, we will discuss the extension of laser-cooling to chemically-prevalent atoms, the non-destructive observation of harmonic electron motion in a single atom, phonon lasing ("phasing?") from trapped ions, and the generation of strong, stimulated optical forces for the deceleration of molecular beams.

Thursday, November 9, 2017 - 4:00pm to 5:00pm

New Windows into the Strong Interaction

Iain Stewart

Massachusetts Institute of Technology


The strong interaction is described by a remarkable theory called Quantum Chromodynamics (QCD), a fully consistent quantum field theory at all distance scales which gives rise to interesting emergent phenomena.  It plays a crucial role in a variety of interesting physical processes, from binding together quarks and gluons in the proton, to the evolution of matter in the early universe, to producing streams of collimated particles called jets in high energy collisions.  Precise control over the strong interaction is necessary for studies of the Higgs boson, as well as for measuring the fundamental parameters of the standard model of particle and nuclear physics.   In this talk I will describe modern developments that enable precision control of the strong interaction in certain situations, as well as a number of important open questions.   Examples will include enhancing our understanding of jet data to dramatically improve the measurement of one of the fundamental parameters of nature, the strong interaction coupling constant, and improving predictions for proton collisions to strengthen our ability to hunt for new particles and forces at very short distances.



Thursday, November 16, 2017 - 4:00pm to 5:00pm

Rewards are worth the Risk: Working in Direct Dark Matter Detection

Kimberly Palladino

University of Wisconsin - Madison


For particle physicists, determining the nature of Dark Matter is one of the greatest open mysteries. An abundance of astrophysical evidence indicates that the matter density of the universe is dominated by a new form of matter, which played a key role in growth of large scale structure. One candidate for Dark Matter is the Weakly Interacting Massive Particle (WIMP). We hope to detect WIMPS by seeing them scattering off of the target materials in our detectors. Liquid xenon has proved itself an excellent target, and LZ is a dual-phase TPC that will begin taking science data in 2020.  Much of the originally proposed parameter space for WIMPS has been excluded over the past few decades, so I will also delve into the sociology of working on direct dark matter searches.


Thursday, November 23, 2017 - Thanksgiving break


Thursday, December 7, 2017 - 4:00-5:00 p.m.




Winter 2018

Thursday, January 18, 2018 - 4:00-5:00 p.m.


What happened 13.8 billion years ago?

Paul Steinhardt

Princeton University)


According to the prevailing view, the universe sprang into existence 13.8 billion years ago in a sudden violent event known as the big bang; and this was soon followed by a brief period of accelerated expansion, known as inflation, which set the large-scale properties of the universe.  In this talk, we will explain the reasons why this idea fails and present a simple alternative – replace the big bang with a bounce and eliminate the need for inflation.   


Thursday, January 25, 2018 - 4:00-5:00 p.m.


Cell mechanical phenotype in cancer: from screening cells to disease biophysics

Amy Rowat

University of California, Los Angeles


Cell mechanical phenotype, or ‘mechanotype’, determines how physical forces are transduced into the cell, and can also signal a transformation in a cell’s physiological state, such as in malignant transformation. If we could obtain higher throughput measurements of cell mechanotype, this would enable a deeper understanding of the molecular origins of cell mechanical properties, as well as screening based on mechanotype. To address these needs, we have used insights from physics to develop a mechanotyping platform that enables us to extract measurements of single cell elastic modulus and fluidity, and to screen cells based on their mechanotype. I will discuss how we are applying our fluidic-based deformability methods to develop a deeper understanding of cell mechanotype in cancer progression. One example application is our discovery that stress hormones, which promote metastasis in mice, also elicit changes in cell mechanical properties: we find that breast cancer cells treated with isoproterenol become stiffer due to actin remodeling, myosin II activity, and increased calcium. Using assays to measure cell invasion through in vitro protein networks, we also discovered that these stiffer isoproterenol-treated breast cancer cells are more invasive. Taken together, our results provide insight into how the mechanical phenotype of cancer cells is associated with their functional behavior.


Spring 2018

Thursday, April 19, 2018 - 4:00pm to 5:00pm

Is Basketball Scoring Just a Random Walk?

Sid Redner

Boston University and Santa Fe Institute


Watching basketball is nearly the same as watching repeating coin tossings!  By analyzing recently available data from recent NBA basketball seasons, basketball scoring during a game is well described by a continuous-time anti-persistent random walk, with essentially no temporal correlations between successive scoring events.  We show how to calibrate this model to account for many statistical season-long metrics of NBA basketball.  As further fillustrations of this random-walk picture, we show that the distribution of times when the last lead change occurs and the distribution of times when the score difference is maximal are both given by the celebrated arcsine law -- a beautiful and surprising property of random walks.  We also use the random-walk picture to construct the criterion for when a lead of a specified size is "safe" as a function of the time remaining in the game.  The obvious application to game-time betting is left as an exercise for the interested.