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Colloquium

Colloquia are held on Thursdays at 4pm in room 4327 (building 4) of the Stevenson Science Center unless otherwise noted. Click here for directions, or phone the department. A reception with the speaker is held at 3:40pm in Stevenson 6333.

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Fall 2017

Thursday, August 24---Fall Faculty Assembly

Thursday, August 31

Alyson Brooks, Department of Physics & Astronomy, Rutgers University

Re-Examining the Astrophysical Constraints on the Dark Matter Model   (show abstract)

The cosmological model based on cold dark matter (CDM) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our Universe. However, at small scales (in the smallest galaxies and at the centers of larger galaxies), a number of observations seem to conflict with the predictions of CDM cosmology, leading to recent interest in alternative dark matter models. I will summarize a number of ways that including baryonic physics (the physics of gas and stars) can resolve the conflict between theory and observations, by significantly altering the structure and evolution of galaxies. Despite all of the successes of baryonic physics in reconciling CDM with observations, I will explain why alternative dark matter models are still viable and interesting.

Host: K. Holley-Bockelmann, F. Munshi

Thursday, September 7

Jonathan McMurry, Associate Vice President for Research, Professor of Biochemistry, Kennesaw State University

Being Crash Davis Ain’t So Bad: Life in the Science Minor Leagues   (show abstract)

In the 1988 baseball masterpiece, Bull Durham, Crash Davis is a career minor-league catcher tasked with preparing pitching prospect Ebby Calvin “Nuke” LaLoosh for the major leagues. Davis, an excellent older player who experienced only one brief call-up to “The Show,” is frustrated about being relegated to class A ball with the Durham Bulls in the twilight of his career. He ends the film setting the career minor league home run record before retiring. Seemingly every graduate student sets out to land a tenure-track job at a Research 1 university. But just like professional baseball players, the vast majority simply won’t make it to The Show. In this talk, a career ‘minor league’ scientist reviews his career path, critically reviewing the roles of talent, luck, ambition and choices have played. Discussion of academic career options beyond R1s will highlight possibilities for serious research programs at primarily undergraduate universities, the benefits of avoiding the R1 tenure grind and the fulfillment to be found in merely staying in the game. Practical advice to those considering applying for undergraduate institution jobs will precede QA. Attendees will be asked to ponder that while Nuke might make it to the majors, Crash gets the girl. And that (particularly when it’s Susan Sarandon) ain’t so bad.

Host: S. Hutson

Thursday, September 14

Herbert Levine, Hasselmann Professor of Bioengineering and Director, Center for Theoretical Biological Physics, Rice University

A physicist looks at cancer metastasis   (show abstract)

Most cancer deaths arise when then primary tumor metastasizes and cancer takes root in distant organs. From the point of view of cellular behavior, metastatic spread requires many capabilities (motility, immune resistance, avoidance of cell death due to lack of adhesion, and ability to grow in a foreign location) which seem beyond what is normally possible for cells in typical organs. To address this issue, we focus on the phenomenon of phenotypic plasticity, the idea that the nonlinear dynamics of cellular genetic networks can lead to transitions to states that are capable of these feats. These new phenotypes can be studied with the help of mathematical models both of the underlying network and of the resultant biophysical properties (such as motility). By revealing the factors most responsible for the formation of these aggressive cellular types, we hopefully can suggest new targeting therapies for what remains the most recalcitrant aspect of cancer.

Host: W. Holmes

Thursday, September 21

Raphael Pooser, Oak Ridge National Laboratory

Practical Quantum Sensing at Ultra Trace Levels with Squeezed States of Light   (show abstract)

Quantum sensors are devices that exploit quantum mechanical effects to obtain enhanced sensitivity over their classical counterparts. Sensors that exploit quantum noise reduction, or squeezed light, have seen renewed interest in recent years as a growing number of devices that utilize optical readout – from gravitational wave detection to ultra-trace plasmonic sensing at the nanoscale – have approached their absolute limits of detection as defined by the Heisenberg uncertainty principle. At this limit, the noise is dominated by the quantum statistics of light (the shot noise limit when coherent light is used). Simultaneously, many devices, including nanoscale sensors, have reached tolerance thresholds in which power in the readout field can no longer be increased. Beyond these limits, squeezed light is required in order to further improve sensitivity in these platforms. In this colloquium we will give a brief overview of quantum optics and quantum noise reduction and place the concepts within the historical context of quantum sensing. Further, we will present our work geared towards producing practical, ubiquitous quantum sensors that break through the shot noise limit to achieve state of the art sensitivities beyond the capabilities of classical devices. We demonstrate atomic magnetometers, atomic force microscopes, compressive imaging, quantum plasmonic imaging, and ultra-trace quantum sensors with state of the art quantum noise levels well below the shot noise limit. We will outline how these devices enable quantum sensing in a ubiquitous, off-the-shelf configuration enhanced with squeezed light in order to beat the state of the art achieved in the analogous classical sensor for the first time

Host: R. Haglund

Thursday, September 28

Rachael Beaton, Department of Astronomical Sciences, Princeton University

Engineering the Measurement of the Hubble Constant   (show abstract)

The local expansion rate of the Universe, the Hubble constant, is one of the fundamental parameters in our current concordance cosmology and one that anchors the expansion history of the Universe. The resolution of the historical factor-of-two controversy in the Hubble constant nearly two decades ago (e.g., the Hubble Space Telescope Key Project; Freedman et al. 2001) has evolved into a 3.4-sigma tension between the traditional Cepheid-distance ladder measurements (Riess et al. 2016, Freedman et al. 2012, Freedman et al. 2001) and that determined from modelling anisotropies in the cosmic microwave background (CMB; Planck Collaboration et al. 2016). At the heart of the tension, is not only a difference in method, but also a fundamental difference in the state of the observed Universe: the distance ladder measures the local rate in the nearby universe (e.g., z~0), whereas the CMB anisotropy measurements uses the very young Universe (z ~1100). Resolution of the tension requires (i) a full scale evaluation of the systematic effects in either technique or (ii) “new physics” added to the standard cosmological model. The trigonometric parallaxes provided by Gaia in the near term permit an unprecedented opportunity to use alternative standard candles and construct a full end-to-end distance ladder without Cepheids. The Carnegie-Chicago Hubble Program is doing just that; we are in the middle of building a new distance ladder that relies on the tip of the red giant branch (TRGB; Beaton et al. 2016). As I will demonstrate, this not only provides a direct cross-check on the Cepheid path, but there are numerous advantages to using a distance indicator that, as a standard candle from old stellar populations, is nearly ubiquitously present low-crowding and low-extinction components of galaxies. More specifically, by being able to calibrate every ‘local’ SNe Ia and easily probing ever-larger volumes with JWST and WFIRST, the TRGB-based distance ladder paves a clear path to a 1% measurement within the foreseeable future.

Host: S. Stewart

Thursday, October 5

Nicole Joseph, Department of Teaching & Learning, Peabody College, Vanderbilt University

The Complexities of Black Women and Girls in STEM   (show abstract)

The experiences of Black women and girls in STEM, mathematics in particular, is an understudied line of inquiry. We know very little about how they experience mathematics teaching and learning across the pipeline. The aim of this interactive talk is to problematize and interrogate the current circumstances surrounding Black women and girls in mathematics that deny them access, power, participation, and opportunity to develop mathematics identities.

Host: S. Hutson

Thursday, October 12---Fall Break

Tuesday, October 17, 3pm (NEW TIME), SC 4327 SPECIAL COLLOQUIUM

Zsuzsa Marka, Department of Physics, Columbia University, NYC

Multimessenger Astrophysics with Gravitational-Waves   (show abstract)

This year's Nobel prize in physics was awarded for the observation of gravitational waves with the LIGO detectors. Advanced LIGO's second observing run ended on August 25, 2017. Gravitational-wave data was analyzed near-real time to rapidly enable comprehensive multimessenger analyses, searching for the electromagnetic and neutrino counterparts. The history and status of the global multimessenger effort will be discussed.

Hosts: S. Hutson, N. Tolk

Thursday, October 19

David Hogg, Professor of Physics and Data Science, NYU

Making accurate physical measurements with data-driven models.   (show abstract)

We have spent more than a century building elaborate (computational) physical models, some of which are extremely successful. These include (for example) QCD, cosmological structure formation, and Earth climate. Despite their successes, these physical models disagree with the data in structured and repeatable ways, and we have enormous amounts of data to discover, test, and measure these disagreements. In many cases, we can combine good physical knowledge with good data to build a predictive model that is more powerful than any model built with either used on its own. Here I demonstrate these general points with the specific example of red-giant stars, where our data-driven model is now delivering more precise measurements of detailed stellar chemical compositions (the products of stellar nucleosynthesis) than any purely physical model. I will give comments on statistics and criticisms of machine learning that are relevant to many scientific domains.

Host: J. Bird

Thursday, October 26---GUY & REBECCA FORMAN LECTURE

Mary James, Dean of Institutional Diversity, Reed College

Host: D. Ernst

Thursday, November 2

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Thursday, November 9---WENDELL HOLLADAY LECTURE

Ed Zganjar, Department of Physics & Astronomy, Louisiana State University

Host: J. Hamilton, A. Ramayya

Thursday, November 16

Chris Stanton, Department of Physics, University of Florida

Coherent Phonons in Condensed Matter Systems

Host: N. Tolk

Thursday, November 23---Thanksgiving

Thursday, November 30

David Hilton, Department of Physics, University of Alabama at Birmingham

Host: K. Hallman, R. Haglund

Thursday, December 7

Patrick Young, School of Earth and Space Exploration, Arizona State University

Host: N. Hinkel

Spring 2018

Thursday, January 11

Vince Cinciolo, ORNL

Fundmental Physics Measurements at the Spallation Neutron Source

Host: J. Velkovska

Thursday, January 18

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Thursday, January 25

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Thursday, February 1

Michael Strickland, Kent State

Quarkonia in heavy ion collisions

Host: J. Velkovska

Thursday, February 8

Ekaterina Poutrina, Air Force Research Lab

Host: Sharon Weiss

Thursday, February 15

Jamie Nagle, University of Colorado, Boulder

Host: J. Velkovska

Thursday, February 22

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Thursday, March 1---FRANCIS SLACK LECTURE

Gabriela González, LIGO and Department of Physics & Astronomy, Louisiana State University

Host: D. Ernst

Thursday, March 8---Spring Break

Thursday, March 15

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Thursday, March 22

Ned Wingreen, Howard A. Prior Professor of the Life Sciences, Departments of Molecular Biology and Physics, Princeton University

Host: E. Rericha

Thursday, March 29

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Thursday, April 5

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Thursday, April 12

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Thursday, April 19

Margaret Turnbull, Global Science Institute

Host: N. Hinkel