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Astrophysics Seminars From 2020 - 2021

Contents


Fall 2020


September 30, 2020

NOTE: No seminar today



October 7, 2020

 CASS-SDSU Seminar welcome event led by George Fuller/Eric Sandquist

Zoom link


 Zoom password: cass-sdsu



October 14, 2020

 "WIMP Dark Matter In An Unusual Cosmological History"

Seyda Ipek
UC President's Postdoctoral Fellow
UC Irvine
https://ucsd.zoom.us/j/98208404473


 Or iPhone one-tap :
US: +16699006833,,98208404473# or +12133388477,,98208404473#
Or Telephone:
Dial(for higher quality, dial a number based on your current location):
US: +1 669 900 6833 or +1 213 338 8477 or +1 669 219 2599 or 888 475 4499 (Toll Free) or 833 548 0276 (Toll Free) or 833 548 0282 (Toll Free) or 877 853 5257 (Toll Free)
Webinar ID: 982 0840 4473
International numbers available: https://ucsd.zoom.us/u/adMT0Gnx6h

ABSTRACT: WIMP miracle has been an important paradigm in the search for dark matter. However the WIMP parameter space is under great tension from direct detection experiments. I will give you a WIMP scenario with an alternative cosmological history of our universe where the quarks confined into mesons at an earlier stage compared to the standard cosmology with the Standard Model. This alternate scenario will open up WIMP parameter space that is not excluded by dark matter experiments.



October 21, 2020

 "A Glimpse Below the Lyman Limit: New observational advances on the escape of ionizing photons from local galaxies"

John Chisholm
Professor
UT Austin
https://ucsd.zoom.us/j/98688518404


 Or iPhone one-tap :
US: +16699006833,,98688518404# or +12133388477,,98688518404#
Or Telephone:
Dial(for higher quality, dial a number based on your current location):
US: +1 669 900 6833 or +1 213 338 8477 or +1 669 219 2599 or 833 548 0276 (Toll Free) or 833 548 0282 (Toll Free) or 877 853 5257 (Toll Free) or 888 475 4499 (Toll Free)
Webinar ID: 986 8851 8404
International numbers available: https://ucsd.zoom.us/u/abScIFDBlg

ABSTRACT: The neutral gas between galaxies was rapidly reionized at redshifts between 6-10. The origin of these ionizing photons remains elusive, but fundamentally shapes the subsequent evolution of the galaxies and the formation of large-scale structure in the universe. The key to unraveling the epoch of reionization is an understanding of both the sources emit ionizing photons (stars vs. active galactic nuclei) and how these ionizing photons escape galaxies. I will present an overview of the recent observational advances that have led to the discovery of local star-forming galaxies that emit ionizing photons, including a recent large Hubble Space Telescope survey that has more than doubled the known number of emitters of ionizing photons. A statistical sample allows for the first detailed look into what types of star-forming galaxies emit ionizing photons and how those ionizing photons can escape star-forming galaxies. I will focus on new probes from the rest-frame ultraviolet that promise to diagnose the porosity of the neutral medium within galaxies at high-redshift. These local surveys set the stage for upcoming telescopes to determine the impact of star-forming galaxies on Cosmic Reionization.



October 28, 2020

 "Inference can constrain a model of neutrino flavor transformation in core-collapse supernovae”

Eve Armstrong
Assistant Professor, Department of Physics
New York Institute of Technology
https://ucsd.zoom.us/j/95800291521


 Or iPhone one-tap :
US: +12133388477,,95800291521# or +16692192599,,95800291521#

Or Telephone:
Dial(for higher quality, dial a number based on your current location):
US: +1 213 338 8477 or +1 669 219 2599 or +1 669 900 6833 or 888 475 4499 (Toll Free) or 833 548 0276 (Toll Free) or 833 548 0282 (Toll Free) or 877 853 5257 (Toll Free)

Webinar ID: 958 0029 1521

International numbers available: https://ucsd.zoom.us/u/abrCIcEfzE

ABSTRACT: The multi-messenger astrophysics of compact objects presents a vast range of environments where neutrino flavor transformation may occur and may be important for nucleosynthesis, dynamics, and a detected neutrino signal. Development of efficient techniques for surveying flavor evolution solution spaces in these environments, which augment existing computational tools, could leverage progress in this field. To this end, we continue our exploration of statistical data assimilation (SDA) to identify solutions to a small-scale model of neutrino flavor transformation. SDA is a machine learning (ML) formula wherein a dynamical model is assumed to generate any measured quantities. Specifically, we use an optimization formulation of SDA wherein a cost function is extremized via the variational method. Regions of state space in which the extremization identifies the global minimum of the cost function will correspond to parameter regimes in which a model solution can exist. Our study seeks to infer the flavor transformation histories of two mono-energetic neutrino beams coherently interacting with each other and with a matter background. We require that the solution be consistent with measured neutrino flavor fluxes at the point of detection, and with constraints placed upon the flavor content at various locations along their trajectories, including the point of emission and the locations of the Mikheyev-Smirnov-Wolfenstein (MSW) resonances. We show how the procedure efficiently identifies solution regimes and rules out regimes where solutions are infeasible. Overall, results intimate the promise of this “variational annealing” methodology to efficiently probe an array of fundamental questions that traditional numerical simulation codes render difficult to access.



November 4, 2020

NOTE: No seminar today



November 11, 2020

NOTE: No seminar today: Veteran's Day Holiday



November 18, 2020

 "Solar System Archaelogy: Multidisciplinary Approaches to Understanding Planetary System Formation"

Gerardo Dominguez
Associate Professor, Physics
CSU San Marcos


 ABSTRACT: Astronomical observations by the Kepler space telescope have confirmed, to date, the existence of over 3,000 planetary systems in our Galactic neighborhood. The distributions of planet size, compositions, and orbital parameters derived from these observations pose a fundamental challenge for models of planetary system formation which currently do not provide an explanation for why some molecular cloud regions collapse to form planetary systems that are rich in terrestrial planets, water, and possibly life while others do not. Historically, our understanding of planetary system formation has relied on astronomical observations of our Solar System. Much less appreciated, however, is the role that that the analysis of planetary materials (i.e. meteorites, cometary dust, and solar wind particles) has played in this understanding. In this talk, I will review how observations of our solar system at the chemical and isotopic level provided us with tight constraints on planetary system formation and the origins of water on terrestrial planets like our own. Incorporating these observations into comprehensive models, I argue, will require combining theoretical and laboratory studies of astrochemical processes that occur in molecular clouds and protoplanetary disks. To illustrate, I will highlight the recent accomplishments made by my research group and collaborators in understanding astrochemical processes with high precision chemical and isotopic resolutions. I conclude by highlighting recent advances in laboratory astrophysical measurement technology including the measurement of radiation induced isotope exchange between water ice and silicate surfaces at 10K, the direct measurement of the optical properties of individual dust grains from the Stardust mission in the laboratory using NanoIR, and the development of planetary exploration instrumentation for the in-situ determinations of the isotopic compositions of lunar ice. I will conclude by discussing how these studies may help us understand the origins of the planets and water in the solar system.



November 25, 2020

NOTE: No seminar today



December 2, 2020

Gina Panopoulou
NASA Hubble Fellow
Caltech



December 9, 2020

Michael McElwain
JWST Project Scientist
NASA Goddard Space Flight Center



December 16, 2020

NOTE: No seminar today


Winter 2021


January 6, 2021

Matthew Povich
Associate Professor, Department of Physics and Astronomy
Cal Poly Pomona



January 13, 2021



January 20, 2021



January 27, 2021



February 3, 2021



February 10, 2021



February 17, 2021



February 24, 2021



March 3, 2021



March 10, 2021



March 17, 2021


Spring 2021


March 24, 2021



March 31, 2021



April 7, 2021



April 14, 2021



April 21, 2021



April 28, 2021



May 5, 2021



May 12, 2021



May 19, 2021



May 26, 2021



June 2, 2021



June 9, 2021