| Wednesday 15 January 2025 | |
| Events for day: Wednesday 25 October 2023 |
| 11:00 - 12:00 Wednesday Weekly Seminar - meeting Lorentz violation effects on CMB polarization School PARTICLES AND ACCELERATORS Abstract: In this talk, we will discuss the impact of Lorentz symmetry violation on the polarization of the Cosmic Microwave Background (CMB). In the standard model of cosmology, no circular polarization is predicted for CMB radiation. However, if we consider the frame of a moving particle, where Lorentz symmetry is violated, it can result in the emergence of circular polarization in the CMB radiation. This talk will provide a study of this phenomena and its implication for our understanding of the CMB polarization. Indico Link https://indico.hep.ipm.ir/e/s.tizchang Meeting Place: ... 12:45 - 13:45 Geometry and Differential Equations Seminar Calabi-Yau theorem School MATHEMATICS In a seminal work, Yau proved Calabi conjecture which states that any volume form on a compact Kahler manifold is the volume form associated to a kahler metric. In this seminar, we present C^0 and C^2 apriori estimates proved by Yau. Venue: Niavaran, Lecture Hall 1 ... 13:30 - 15:00 Weekly Seminar NANOGrav's Discovery of Low-Frequency Gravitational Waves School ASTRONOMY Abstract Astrophysicists from the NANOGrav consortium have found convincing evidence of slowly oscillating ripples in the fabric of space-time. Their research showcases a firmly correlated stochastic signal among 67 pulsars drawn from a rich 15-year pulsar-timing dataset. This pattern of correlations aligns with expectations for a stochastic low-frequency gravitational-wave background, potentially stemming from cosmological or astrophysical sources. In this presentation, I will provide a detailed review of these findings and demonstrate how a model of single field inflation containing an intermediate phase of ultra slow ... 14:00 - 15:00 Combinatorics and Computing Weekly Seminar The Jump of the Clique Chromatic Number of Random Graphs School MATHEMATICS The clique chromatic number of a graph is the smallest number of colors in a vertex coloring so that no maximal clique is monochromatic. In 2016 together with McDiarmid and Pralat we noted that around $p ≈ n^{−1/2}$ the clique chromatic number of the random graph $G(n, p)$ changes by $n^{Ω(1)}$ when we increase the edge-probability $p$ by $n^{o(1)}$, but left the details of this surprising phenomenon as an open problem. In this talk, we settle this problem, i.e., resolve the nature of this polynomial ''jump'' of the clique chromatic number of the random graph $G(n, p)$ around edge-probability $p = n^{−1/2}$ . ... 16:00 - 17:00 Mathematics Colloquium Random π-lifts and Expansion Lower Bounds for Random Regular Graphs School MATHEMATICS In this talk I aim to discuss asymptotically almost sure (aka a.a.s.) expansion lower bounds of the uniform ensemble of d-regular graphs and show that random π-lifts may be used to obtain some improvements. In this regard, after introducing the model, I briefly go through some techniques already used in this area of research and based on a recent joint contribution with MH. Shojaedin, I will introduce a general reduction method that provides a.a.s. lower bounds when a.a.s. upper bounds are known, which is based on the analysis of a contiguous ensemble constructed through random π-lifts. This model gives rise to a dual approximation ... |