Here are some of the submitted and accepted presentations:
Adam Furman, Brown University
To better understand and identify the four top quark production event in proton-proton collisions at the Large Hadron Collider, a machine learning approach is used. Using a simulated set of results, a neural network is trained. Each simulated event contains 76 variables, and the importance of each variable is calculated by comparing the neural network’s performance with and without access to that variable’s data over the course of thousands of iterations. Only a few variables are found to have high significance, potentially indicating physical processes of interest and enabling a high-accuracy model to be created using only a subset of the input data.
Adam Tropper, Brown University
While the Standard Model of Particle Physics is the most accurate description of the fundamental properties of nature that occur on a quantum level, many mysteries still remain. One of the most illusive such mysteries is the so-called fermion mass hierarchy problem which poses the question: “if elementary particles obtain their mass from the Higgs mechanism in an identical way, why do their masses differ by factors of over a million?” Our current solution is to just plug the requisite parameters (which again differ by factors of over a million) into the Standard Model by hand; however, this is a woefully lacking approach as it makes no mention of why these parameters should be so extraordinarily different in the first place. In this talk, I will present one approach to resolving this fermion mass hierarchy problem that emphasizes the underlying role that randomness might play on our reality. Perhaps nature is fundamentally random and chaotic rather than prescribed and ordered at a quantum level.
Anna Zuckerman, Brown University
Lasers provide a potentially energy efficient, powerful, and technology simple form of transmitting and receiving information over interstellar distances, and thus are of special interest in the search for extraterrestrial intelligence. Past works have directly searched through the spectra of target stars for features that match the expected characteristics of laser signals: high intensity in a narrow wavelength band, gaussian shape due to travel through the telescope optics, and no clear natural explanation. Most have used observations from the Keck telescope. This project introduces a new method: by first matching the target spectrum to a library of spectra corresponding to stars with known properties, then subtracting a linear combination of the closest matching spectra from the target spectrum, we produce a residual which contains only features unique to the target spectrum. Examining the residual for laser signals will provide a more sensitive laser search than previously conducted. We also present a calibration of the laser search algorithm to demonstrate its wider applicability in analyzing Automated Planet Finder, rather than only Keck, observations.
Anshul Bhargava University of Massachusetts
Simulating the dielectric function for TMDC heterostructures.
Grant Rutherford, Brown University
To study how initial conditions of PFRC-2, a reversed-field configuration device at Princeton, affect startup and the relative importance of different processes during startup, we constructed and solved a 0D model as an initial value problem. Incorporated into the model are hydrogen processes using collisional radiative rate coefficients taken from EIRENE, charged particle loss due to flow parallel to B, enhanced confinement from mirror fields and the FRC, electron interactions with the ends of the machine, and subsequent generation of nonthermal, high energy electrons. By solving the model we obtain electron density and energy as a function of time and can determine the delay to densification. Additionally, we present trends in these outputs as functions of major machine inputs, namely: P_in, n_H2, τe, and B.
Huaijin Wang, Yale University
Wendelstein 7-X (W7-X) is an optimized stellarator plasma experiment featuring 50 complex non-planar superconducting coils operating at 4.2 K, providing a three-dimensional steady-state toroidally closed magnetic cage with an on-axis field strength of 2.5 T. The goal of this experiment is to bring the stellarator concept to maturity in order to prepare a next-step device towards a stellarator fusion power plant. For this purpose, a systems code framework is used to make design assessments and to channel the experience gained from W7-X into a next-step stellarator device. Neutronic analysis determines the distribution of highly energetic neutrons produced by the deuterium-tritium plasma on the stellarator first wall, and is essential in the design of critical components such as the blanket and the magnetic field coils. In this presentation, I will describe a new method of fast evaluation of the Neutron Wall Load distribution for arbitrary stellarator geometry and its application in stellarator optimization, which will provide critical information for design parameters used in the systems code.
Joyce Caliendo University of Connecticut
Jungho Daniel Choi, Brown University
Despite decades of research into the fractional quantum Hall (FQH) effect, the microscopic origin and behaviour of this phenomenon has not yet been fully understood by physicists. Recent experimental strides have been made in measuring quantised heat flow in FQH states, allowing physicists to probe their edge structures. Given the recent nature of the discovery, there has only been limited work on understanding the equilibration of thermal edge modes in the FQH effect, which inhibits our ability to comprehend and interpret thermal conductance data. I first give a brief overview of the relevant background required to understand the current framework physicists use to understand the FQH effect. Given this understanding, I then discuss the importance of thermal edge modes as probes to characterise and better understand the nature of FQH states. I also present my work on improving preliminary phenomenological models of thermal edge mode equilibration, which was done by incorporating the temperature dependences of a characteristic parameter known as the equilibration length into these models. I conclude by showing that this modification leads to different predictions for thermal conductance measurements as well as shining light on some possible counterintuitive cooling behaviour that may occur on the FQH edges.
Matthew Regala, University of Connecticut
The evolution of a super massive black hole’s mass and spin is dependent on the history of events in the black hole’s lifetime. Merging with other black holes and gradually absorbing accretion disks can change the mass and the magnitude of its spin. We have found that merger dominated black holes are larger and accretion dominated black holes have a larger magnitude of spin.
Peter DeRosa University of Massachusetts
“Excited states in Scandium isotopes have been populated following the fusion-evaporation of 14C at 45 MeV impinged on a thin 36S target with a Ag backing at the John D. Fox Superconducting Laboratory at Florida State University. The evaporation channels were selected with a zero degree particle telescope while emitted gamma radiation was detected with a mixed array of Clover and single coaxial HPGe detectors. The observed level schemes of [48-45]Sc will be presented from coincident data. Results will be discussed and contrasted against single particle shell model results. "