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Alumni Speaker 2015 David Dunn

Where were you? Woodrum

Muonium, Positronium, Proton Radius, and all that

Dr. Michael Eides University of Kentucky I will discuss physics of exotic muonium and positronium atoms, high precision quantum electrodynamic calculations of energy levels, and determination of the electron-muon mass ratio. I'll introduce the proton radius puzzle, discuss briefly the experimental data on muonic hydrogen, deuterium, and helium, and explain the status of the respective theory.

Enhancing Exoplanet Discovery and Characterization through Stellar Photometric “Flicker”

Dr. Fabienne Bastien Pennsylvania State University As a result of the high precision and cadence of surveys like MOST, CoRoT, and Kepler, we may now directly observe the very low-level light variations arising from stellar granulation in cool stars. Here, we discuss how this enables us to more accurately determine the physical properties of Sun-like stars, to understand the nature of surface convection and its connection to activity, and to better determine theproperties of planets around cool stars. Indeed, such sensitive photometric "flicker" variations are now within reach for thousands of stars, and we estimate that upcoming missions like TESS will enable such measurements for ~100 000 stars. We present recent results that tie “flicker” to granulation and enable a simple measurement of stellar surface gravity with a precision of 0.1 dex. We use this, together and solely with two other simple ways of characterizing the stellar photometric variations in a high quality light curve, to construct an evolutionary diagram for Sun-like stars from the Main Sequence on towards the red giant branch. We discuss further work that correlates “flicker” with stellar density, allowing the application of astrodensity profiling techniques used in exoplanet characterizationto many more stars. We also present results suggesting that the granulation of F stars must be magnetically suppressed in order to fit observations. Finally, we show that we may quantitatively predict a star's RV jitter using our evolutionary diagram, permitting the use of discovery light curves to help prioritize follow-up observations of transiting exoplanets.

Topological Insulators 101

Dr. Ganpathy Murthy University of Kentucky We thought we knew all there was to know about band insulators back in the 1930s. However, in the last 10 years we have learnt that there distinct types of band insulators in 2 and 3 dimensions. The distinction between these types is "topological", a term I will explain. I will introduce the idea of band topology in detail in 2D. I will then use the example of the integer quantum Hall effects to show that a topological insulator has edge states that are robust to disorder. Next I will introduce time-reversal invariance, which puts powerful constraints on band insulators. Once again, edge modes will prove to be extremely useful in characterizing the different types of band insulators. I will end up by talking about 3D topological insulators and some of the phenomenology associated with them.

Merit Weekend 2015

The College of Arts & Sciences at the University of Kentucky offers the opportunity to work with renowned faculty in over forty varied departments. From Economics to Earth and Environmental Studies, A&S offers a hands-on educational experience, preparing you for a successful career after graduation.

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