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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 3:30pm in Stevenson 6333.

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Fall 2019

Thursday August 29th 2019 4:00 PM

Carlos Silva, Georgia Institute of Technology

Exciton polarons in two-dimensional organic-inorganic hybrid perovskites   (show abstract)

While polarons — charges bound to a lattice deformation induced by strong electron-phonon coupling — are understood to be primary photoexcitations at room temperature in three-dimensional hybrid organic-inorganic perovskite (HOIP) lattices, excitons are the stable quasiparticles in two-dimensional (2D) HOIPs. In this colloquium, I will address the question: are polaronic effects consequential in the exciton properties of these materials? Establishing the role of exciton polarons is a key fundamental issue for the rigorous description of the materials physics of 2D HOIPs. Based on our recent work, I will argue that exciton-polaron effects are manifested in the generally observed spectral fine structure comprised of four distinct, non-degenerate exciton resonances with constant inter-peak energy spacing that varies weakly upon substitution of organic cation. I will discuss the possible role of polaronic effects in establishing the finestructure along with alternative interpretations presented in the literature, including the effects of vibronic structure, Rashba splitting, and exchange interactions. Finally, I will address the consequences of polaronic effects on the quantum dynamics of these materials, relevant for applications in optoelectronics, such as light-emitting diodes, lasers, and polariton spontaneous coherence.

Host:R. Haglund

Thursday September 5th 2019 4:00 PM

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Thursday September 12th 2019 4:00 PM

Scott Gaudi, Ohio State University

The Demographics of Exoplanets with WFIRST   (show abstract)

Measurements of the demographics of exoplanets over a range of planet and host star properties provide fundamental empirical constraints on theories of planet formation and evolution. I will discuss various efforts to measure and synthesize exoplanet demographics over broad regions of parameter space. Because of its unique sensitivity to low-mass, long-period, and free-floating planets, microlensing is an essential complement to our arsenal of planet detection methods. I motivate, and provide expectations for, a microlensing survey with WFIRST, which when combined with the results from Kepler, will yield a nearly complete picture of the demographics of planetary systems throughout the Galaxy.

Host:R. Scherrer

Thursday September 19th 2019 4:00 PM

FRANCIS G. SLACK LECTURE

Gerald Gabrielse, Trustees Professor and Director of the Center for Fundamental Physics at Northwestern University

Tabletop Searches for New Physics: a Tale of Two Electron Dipole Moments    (show abstract)

The fundamental mathematical description of physical reality, the Standard Model of Particle Physics, is the great triumph and the great frustration of modern physics. The great triumph is that all laboratory measurements are so far consistent with its predictions. The great frustration is that the Standard Model is clearly wrong, or at least significantly incomplete, in that it cannot account for many basic features of our universe. Measurements of the magnetic and electric dipole moments of the electron are crucial tests of the Standard Model. The measured magnetic dipole moment of the electron, the most accurately determined property of an elementary particle, is a test of the Standard Model's most precise prediction. The measured electric dipole moment of the electron tests the relative validity of the dramatically predictions of the Standard Model and of proposed improvements (e.g. supersymmetric models) This work was supported by the USA NSF.

Host:N. Tolk

Monday September 23rd 2019 4:00 PM

David Brin, Astrophysicist and Novelist

Our place in the Cosmos and Is Anyone Out There   (show abstract)

In both science and literature, the question of ‘others’ can be a mirror illuminating our own origins and plausible destinies. Are we a fluke? Might we be the first to navigate the minefield of existence? Astrophysicist and novelist David Brin will (briefly) survey both what we know and can speculate about life in the universe.

Host:R. Scherrer

Thursday September 26th 2019 4:00 PM

Les Johnson, NASA

Perspectives at 50: Space Science and Exploration Past, Present, and Future   (show abstract)

After the Apollo astronauts landed on the moon, the Space Race ended. The achievements in human space flight continued with the successes of Skylab, the Space Shuttle, and the International Space Station. With the retirement of the Space Shuttle fleet in 2011, America has been relying on Russia to carry its crews into space. Today, we are in the midst of a new Race to Space, with various commercial companies vying to claim the mantle of returning Americans to space in American-made rockets – providing revolutionary changes in the economics of space travel. A similar revolution in cost and capability is occurring in the robotic science community, allowing small businesses, universities, and non-profit research institutions to build and fly small spacecraft with capabilities rivaling those previously in the exclusive domain of governments. Today, for the first time since the 1960’s, there is a sense of unbounded optimism regarding the human future in space and our ability to send our robotic emissaries to the outer reaches of the solar system and beyond.

Host:N. Tolk

Thursday October 3rd 2019 4:00 PM

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Thursday October 10th 2019 4:00 PM

Julie Hogan, Bethel University

CMS Particle Flow: the LEGO tutorial and searches for new massive quarks   (show abstract)

The Compact Muon Solenoid detector at CERN's Large Hadron Collider uses a method called "particle flow" to interpret electronic signals in detector elements as particles like electrons or muons. This critical software is rarely learned in detail by young CMS researchers. I will share an engaging new hands-on tool developed for summer tutorials at Fermilab: the Particle Flow LEGO Experience. Then I will present recent searches for new physics particles called "vector-like quarks", which decay to a variety of massive quarks and bosons. In these searches we connect the particle flow information from showers of quark-based particles with machine learning algorithms to probe for evidence of new physics.

Host:S. Starko and R. Scherrer

Thursday October 17th 2019 4:00 PM

WENDELL HOLLADAY LECTURE

Calen Henderson, IPAC-Caltech

Finding Planets with Microlensing

Host:S. Jacklin

Thursday October 31st 2019 4:00 PM

Shriram Ramanathan, Purdue University

Host:R. Haglund

Thursday November 7th 2019 4:00 PM

Prem Kumar, Northwestern University

Quantum Information Processing

Host:Sharon Weiss

Thursday November 14th 2019 4:00 PM

FORMAN LECTURE

Deborah Berebichez

Outrageous Acts of Science

Host:S. Hutson

Thursday November 21st 2019 4:00 PM

Andrew Mugler, Purdue

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Thursday November 28th 2019 4:00 PM

Thanksgiving Holidays

Thursday December 5th 2019 4:00 PM

Thomas Weiler, Vanderbilt University

Host:S. Hutson

Spring 2020

Thursday January 9th 2020 4:00 PM

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Thursday January 16th 2020 4:00 PM

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Thursday January 23rd 2020 4:00 PM

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Thursday January 30th 2020 4:00 PM

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Thursday February 6th 2020 4:00 PM

Zina Cinker, National Graphene Association

Host:N. Tolk

Thursday February 13th 2020 4:00 PM

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Thursday February 20th 2020 4:00 PM

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Thursday February 27th 2020 4:00 PM

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Thursday March 5th 2020 4:00 PM

Spring Holidays

Thursday March 12th 2020 4:00 PM

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Thursday March 19th 2020 4:00 PM

Jeffrey Nico, NIST

Neutron Lifetimes

Host:R. Scherrer

Thursday March 26th 2020 4:00 PM

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Thursday April 2nd 2020 4:00 PM

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Thursday April 9th 2020 4:00 PM

Saul Teukolsky

Host:R. Scherrer

Thursday April 16th 2020 4:00 PM

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