Quasinormal modes of charged magnetic black branes & chiral magnetic transport

We compute quasinormal modes (QNMs) of the metric and gauge field perturbations about black branes electrically and magnetically charged in the Einstein-Maxwell-Chern-Simons theory. By the gauge/gravity correspondence, this theory is dual to a particular class of field theories with a chiral anomaly, in a thermal charged plasma state subjected to a constant external magnetic field, $B$. The QNMs are dual to the poles of the two-point functions of the energy-momentum and axial current operators, and they encode information about the dissipation and transport of charges in the plasma. Complementary to the gravity calculation, we work out the hydrodynamic description of the dual field theory in the presence of a chiral anomaly, and a constant external $B$. We find good agreement with the weak field hydrodynamics, which can extend beyond the weak $B$ regime into intermediate regimes. Furthermore, we provide results that can be tested against thermodynamics and hydrodynamics in the strong $B$ regime. We find QNMs exhibiting Landau level behavior, which become long-lived at large $B$ if the anomaly coefficient exceeds a critical magnitude. Chiral transport is analyzed beyond the hydrodynamic approximation for the five (formerly) hydrodynamic modes, including a chiral magnetic wave.Comment: 29 pages + appendix, 14 figures; v2: references added, published versio

MEMS 411: Design of a wiffle ball pitching machine

This project designs a wiffle ball pitching machine that would demonstrate the Magus Effect to the audience in St. Louis Science Center. Primarily made out of wood, this design is portable and able to pitch wiffle balls both indoor and outdoor. With two spinning wheels whose maximum spinning rate is 5044 rpm, this design is able to pitch balls with topspin, backspin, and no spin, and the trajectory of the traveling balls can be recorded by naked eye. The highest recorded traveling velocity of the pitched ball is 67 mph. Several function that would facilitate the demo process are included in this design: accurate pitching and angle adjusting--it is able to pitch balls at an angle range of 0 degrees to 90 degrees and in the testing trial, 12/12 balls are able to hit a 20\u27 by 20\u27 target placed 20 feet away from the machine. There are several risks that a user might take notice of when using the machine: the spinning wheels might scratch a user\u27s hand when it gets too close; the wires connected to the motor would trip users; a user might be hit by a traveling wiffle ball; and if used improperly, a user may get electric shock. Warning signs are prepared on the device to prevent the such risks for happening

Data Collection Research for Multidisciplinary Design & Prototyping Fall 2023: Spring 2023 MEMS 400 Independent Study

Dr. Jackson Potter is a Mechanical Engineer and professor at Washington University in St. Louis. One of the classes he teaches is called Multidisciplinary Design & Prototyping (MEMS 312). The class is taken by students from various disciplines to learn about design processes and develop new skills. In addition, this class typically has a theme to make the prototyping process more realistic and have an end goal. For 2022 the theme was accessible gaming, where students would create universal gaming controllers for people that might not be able to use traditional controllers. For the next year, Dr. Potter wanted to focus on sensors, so the theme focuses on creating robust designs that could house sensors and be functional outside, teaching students about the different sensors and prototyping the housing for it. Additionally, a real life application is that an air quality monitoring system needs to be stored and deployed efficiently, so we tried to come up with a minimum viable prototype to address the issue. This document is for compiling all potential content for the Fall 2023 course theme

Pressure study of nematicity and quantum criticality in Sr3_3Ru2_2O7_7 for an in-plane field

We study the relationship between the nematic phases of Sr$_3$Ru$_2$O$_7$ and quantum criticality. At ambient pressure, one nematic phase is associated with a metamagnetic quantum critical end point (QCEP) when the applied magnetic field is near the \textit{c}-axis. We show, however, that this metamagnetic transition does not produce the same nematic signatures when the QCEP is reached by hydrostatic pressure with the field applied in the \textit{ab}-plane. Moreover, a second nematic phase, that is seen for field applied in the \textit{ab}-plane close to, but not right at, a second metamagnetic anomaly, persists with minimal change to the highest applied pressure, 16.55 kbar. Taken together our results suggest that metamagnetic quantum criticality may not be necessary for the formation of a nematic phase in Sr$_3$Ru$_2$O$_7$

A novel non-Fermi-liquid state in the iron-pnictide FeCrAs

We report transport and thermodynamic properties of stoichiometric single crystals of the hexagonal iron-pnictide FeCrAs. The in-plane resistivity shows an unusual "non-metallic" dependence on temperature T, rising continuously with decreasing T from ~ 800 K to below 100 mK. The c-axis resistivity is similar, except for a sharp drop upon entry into an antiferromagnetic state at T_N 125 K. Below 10 K the resistivity follows a non-Fermi-liquid power law, rho(T) = rho_0 - AT^x with x<1, while the specific heat shows Fermi liquid behaviour with a large Sommerfeld coefficient, gamma ~ 30 mJ/mol K^2. The high temperature properties are reminiscent of those of the parent compounds of the new layered iron-pnictide superconductors, however the T -> 0 properties suggest a new class of non-Fermi liquid.Comment: 6 pages, 4 figure