University Events

Description: The UMASS Dartmouth Physics Department Colloquia


A weekly seminar series of fully online colloquia featuring speakers from around the globe. This week's colloquia features a series of three lightning talks lasting for the duration of 10-15 minutes each.


Date: Thursday, February 4, 2021

Time: 6:00pm


Zoom Link: https://umassd.zoom.us/j/98360315189?pwd=VktzWEJFZXF4bUMxUStUbEdiOE56dz09


Talk #1

Title: Studying the Relationship Between Flare counts and Stellar Properties



Speaker: Patrick Stanley and Kiley Fridley, Iowa State University


Abstract:

In the first phase of this project, AltaiPony, a flare finding program, was used to verify the flare counts of flaring Kepler stars. It was found that the original program used by Davenport et al. (Appaloosa) was overcounting flares. Using a combination of a Kepler catalog of flaring stars (Davenport et al. 2016) and a catalog of rotating stars (McQuillan et al. 2014), a sample of 60 stars was obtained. Using AltaiPony, 3597 candidate flares were found, compared to the 12055 Davenport candidate flares for the same stars. However, this number of candidate flares is very conservative as AltaiPony is undercounting flares in most cases. Thus-far, a loose relationship between the rotation period, flaring rates, and spectral types of these stars, that is matching the theoretical relationship, has been found. Originally, the sample was larger, but stars that had problematic light curves (binary stars, RR Lyraes, Cepheids, etc.) and stars that did not have object types had to be removed. By analyzing the flaring rates of these stars, we are hoping to uncover previously unexplored relationships between spectral type, flaring rates, and other stellar properties such as temperature and rotational period.

Talk #2


Title: Late-Time Dynamical Friction Effects Infinite Disks

Speaker: Mark Ivan Ugalino, University of Massachusetts Dartmouth

Abstract:

Models describing the dynamical friction experienced by a moving massive object involve an assumption that, throughout its trajectory, the background medium is infinite; that is, the characteristic length of the background is much larger than the orbital radius. However, in most cases, astrophysical objects like planets and stars evolve in gaseous disks whose dimensions are finite. In this thesis, we derived an expression for the hydrodynamical drag experienced by a point particle moving through a finite fluid background with cylindrical symmetry. We assume in this method that the particle has completed several orbits before measuring the force exerted.

Talk #3


Title: Quantum Entanglement and Thermal Behavior in Charged-Current Weak Interactions

Speaker: George Iskander, University of Chicago

Abstract:

We show that quantum entanglement between causally separated regions of a nucleon in antineutrino-nucleon scattering manifests itself as a thermal component in the resulting pion momentum distribution. For antineutrino scattering coherently from the (carbon) nucleus as a whole, this thermal component is absent, as expected by our quantum entanglement thermalization proposition. These phenomena, which have been observed in proton-proton collisions at the Large Hadron Collider, and in electromagnetic deep inelastic scattering, are now for the first time shown to exist in electroweak interactions as well.


For additional information please contact Dr. Robert Fisher (rfisher1@umassd.edu) or Dr. Renuka Rajapakse (rrajapakse@umassd.edu)