To promote scientific discussions during this pandemic, we are organizing an online seminar series, i.e. Copernicus Webinar Series, seeking the most outstanding speakers to introduce innovative ideas and important progress in the field of gravity and cosmology. This series is named after the famous Polish Astronomer, Nicolaus Copernicus, whose discovery eventually marked the dawn of modern science.
We would like to invite you to take part in the upcoming 61st Copernicus Webinar joint-talks co-presented by Xi Tong and Weikang Lin
Time: 21st Sept, Tuesday, 3pm CEST (9pm Beijing time, 10pm JST, 9am EDT)
1st speaker: Xi Tong (Hong Kong University of Science and Technology)
Title: Chemical-Potential-Assisted Particle Production in FRW Spacetimes
Abstract: We analyze gravitational particle production assisted by chemical potential. By utilizing the uniformly smoothed Stokes-line method and Borel summation, we gain insight into the fine-grained history of enhanced particle production. Analytic/semi-analytic formulae describing the production amount, time and width are obtained for both spin-1 and spin-1/2 particles in various FRW spacetimes. Our work also serves as a concrete demonstration of the uniformly smoothed Stokes-line method applied to cosmology.
2nd speaker: WeiKang Lin (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)
Title: Uncalibrated cosmic standards (UCS) and Early-Universe-Physics Insensitive determinations of the Hubble Constant
Abstract: To further investigate whether pre-recombination physics alone can resolve the Hubble tension, we explore H0 determinations that are insensitive to early-universe physics. The similarity between the two sound horizons at recombination and at the drag epoch is insensitive to early-universe physics. This allows us to relate the two horizons and treat them as free parameters. Together with Type Ia supernovae, these uncalibrated cosmic standards (UCS) robustly constrain the matter density fraction. Combining with other non-local observations, we obtain several constraints on H0 with significantly reduced sensitivity to early-universe physics, which are consistent with Planck. These results suggest that pre-recombination physics cannot fully resolve the Hubble tension.
We also would like to invite you to take part in the upcoming 7th Colloquium talk,
speaker: Matias Zaldarriaga (IAS)
Time: 23rd September, Thursday, 3pm, CEST (9pm Beijing time, 10pm JST, 9am EDT)
Title: GW astrophysics with LIGO/VIRGO data
Abstract: I will describe our recent work re-analyzing the GW data made public by the LIGO collaboration. More broadly I will discuss some of the outstanding questions related to binary black hole mergers, what the data might be saying and what we might expect in the near future. I will focus on what can be inferred from the spin measurements.
Zoom link for the Colloquium: https://hkust.zoom.us/my/copernicus
meeting id: 9423380685