| Tuesday, December 13, 2022 |
| ASTRO Journal Club | |
| Event Type: Other | |
| Time: 12:30 PM - 1:30 PM | |
| Location: 726 Broadway, 940, CCPP Seminar | |
| Evidence for Long-range AGN Jet Feedback in the Low Redshift Lyman-alpha Forest | |
| Blakesley Burkhart, Flatiron Institute | |
| Event Type: Astro Seminar | |
| Time: 2:00 PM - 3:00 PM | |
| Location: 726 Broadway, 940, CCPP Seminar | |
| Abstract: The Lyman-α forest is a key diagnostic for the state of diffuse baryons in the intergalactic medium (IGM) and for fundamental cosmological parameters. At high redshift (i.e., z ≥ 2) the Lyman-α forest is observed in optical wavelengths from ground-based observatories and has been used to constrain small-scale cosmic structure, the dark matter distribution, the IGM gas temperature, and the evolution of the ultraviolet ionizing background (UVB) radiation. However, the low redshift (z~0.1) Lyman-α forest, observed from space-based UV instruments such as HST COS, has challenged our theoretical understanding of the Lyman-α forest as the choice of AGN feedback and UVB models both affect the Lyman-α forest statistics. In this talk, I will show how black hole feedback physics can be at least as important (or more!) as the UVB for the neutral gas in the low redshift IGM. The AGN feedback signatures appear in the neutral gas statistics beginning around z~1, thus possibly affecting 21-cm intensity mapping programs that target this redshift range (i.e., HIRAX). These findings herald a significant paradigm shift for cosmological simulations and observations that target the low redshift IGM. | |
| Tensor models, large N limit and double scaling limit | |
| Adrian Tanasa, University of Bordeaux | |
| Event Type: HEP Seminar | |
| Time: 4:00 PM - 5:00 PM | |
| Location: 726 Broadway, 940, CCPP Seminar | |
| Abstract: Matrix models, seen as quantum field theoretical models, are known to represent a successful approach to 2D quantum gravity and to have many other interesting applications in Physics. Some of the main results of the study of matrix models in theoretical physics are the 't Hooft large N limit (the perturbative series can be reorganized in powers of 1/N (N being the matrix size)) and the double scaling limit mechanism (known to be related to the continuuos limit of the models). After a brief introduction dedicated to matrix models, I will focus in this talk on tensor models, which are a natural quantum field theoretical generalization of these matrix models. In particular, I will present the implementation of the large N limit (N being now the size of the tensor) and the double scaling limit mechanisms for various tensor models, such as the O(N)³-invariant tensor model, initially introduced in O dimensions by Carrozza and Tanasa, arXiv:1512.06718, and then extended to the 1-dimensional case, by Klebanov and Tarnopolsky, arXiv:1611.08915. In the last part of the talk I will present how tensor models have been related (initially by Witten and then shortly after by Klebanov and Tarnopolsky) to the Sachdev-Ye-Kitaev model, which is known to be a particularly interesting toy model for holography. | |