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We meet every other Wednesday at 3:00PM in room P119.

Previous year's GRADTALKS are available here:
- 2016-2017 School Year

Date Speaker Presentation Abstract
October 5th 2017 Guadalupe Maria Barrios Sazo Simulating white dwarf mergers and black widow pulsars with Castro Castro is an adaptive mesh refinement code that solves the compressible hydrodynamics equations for astrophysical flows. The applications of Castro include Type Ia supernovae and core-collapse studies. In this talk I will describe the code capabilities and its role exploring models of white dwarfs (WD) as progenitors for Type Ia supernovae. I will give special emphasis to the white dwarf merger model. In addition, I will mention some initial exploratory efforts made towards simulating a black widow pulsar (BWP). The BWP consists of a millisecond pulsar in a tight binary system with a low mass star. Observations infer intriguing masses for the neutron star, which could be better characterized with simulations.
October 26th 2017 Anya Gura Artificially Layered Ferroelectric Oxides and Their Uses in the Control of Graphene Through Ferroelectric Switching We use a ferroelectric (FE) material to harness the electric functionalities of graphene (Gr) by engineering Gr-FE Field Effect Transistors. In these devices, the underlying FE superlattice layer is used to control the charge state of the Gr channel. By using artificially layered FE superlattices and optimizing parameters during growth and Gr deposition, we have obtained ideal interfaces that result in hysteretic devices. However, our successful devices using PbTiO3/SrTiO3 as the FE layer display a shift of the gating and C-V curves towards positive gate voltages, making the polarization state unstable. We believe this is caused by ordered structural defects that arise during growth of the superlattice. To overcome this obstacle we have designed a hybrid superlattice system consisting of PbTiO3/SrTiO3/PbTiO3/SrRuO3 alternating layers. In these samples the C-V measurements are centered on 0V, providing retention of the polarization state without any applied compensation bias and enabling non-volatile polarization switching as a result of strain applied by an AFM Tip. We studied local changes in conductivity of the Gr and demonstrate the use this technique to design re-writable circuit elements on the graphene-FE hybrid devices.
November 9th 2017 Jeremy Jae Hyeok Chang Dark Matter Phenomenology Although there are a lot of evidences of dark matter, its properties are still puzzling. Finding out the properties is one of most important topics in particle physics. I’ll talk about an overview of dark matter phenomenology including dark matter evidences, candidates, and searches. I’ll mostly focus on Weakly Interacting Massive Particles (WIMP) and the dark photon models along with constraints and direct detection experiments for the models.
March 8th 2018 Gabriel Santucci GUTs and Nucleon Decay Does the Proton Decay? Proton stability is not guaranteed by any fundamental symmetry. Standard Model interactions share the same structure: gauge theories with unitary symmetry. Grand Unified Theories (GUTs) unifies the SM interactions at very high energies (GUT scale) - beyond the reach of accelerators. Most GUTs predict nucleon decay with a very long lifetime (> 1030 years). Thus, nucleon decay serves as a direct probe of GUTs. But very massive detectors are necessary for these searches.
March 22nd 2018 Connor Behan Conformal Invariance: What's it Good For? Typical field theories are invariant under rotations and translations which both preserve the angle between two vectors. However, there are other transformations that preserve angle and one can consider field theories that preserve all of those. This leads us to a conformal field theory (CFT). In this talk I will explain why CFTs are interesting for topics ranging from phase transitions to string theory. I will also show that some CFTs can be solved exactly, while others can be approximated to unprecedented accuracy by methods that were discovered in 2008.
April 11th 2018 (5PM) Ludwig Krinner Ultracold Atoms in the Schneble Laboratoy: A Novel Perspective on Spontaneous Emission Ultracold atoms are a versatile platform, enabling the study and potentially simulation of hard to calculate systems. In my talk I give a brief outline of the experimental techniques involved in reaching quantum degeneracy in dilute gases, followed by a brief presentation of results from the laboratory of Prof. Schneble on spontaneous emission of matter waves from engineered matter-wave emitters. While spontaneous emission is usually limited to a rate equation regime (Markov approximation), we can easily tune our emitters outside the Markov-regime, observing non-Markovian, partially reversible, dynamics as well as a bound-state feature.
March 15th 2018 Nikko Pomata