## 2020/7/20 (月)## Attracted by Particle Production †## Soichiro Hashiba †Whenever a value of field changes, particles coupled with this background field are produced. This particle production is quite universal and it can induce considerable backreaction by extracting the energy of the background field. In other words, this particle production behaves as a kind of attractive force. By using this effect, we can trap the background field at a certain point where coupled particles are produced most efficiently. In this talk, I will explain the mechanism of field trapping by particle production and then introduce several applications, moduli trapping and trapped inflation. References: ## 2020/7/13 (月)## Thermodynamical interpretation for the second law of Cosmology †## Ido Ben-Dayan †The area of a future holographic screen increases monotonically. Associating this area with entropy results in a generalized second law for Cosmology (GSLC). Unlike black hole horizons, screens relevant to Cosmology have no thermodynamical interpretation. ## 2020/7/6 (月)## Introduction of peak statistics of Gaussian random fields †## Minxi He †In this talk, the statistical theory of peaks of Gaussian random fields are introduced, based on Bardeen, Bond, Kaiser, and Szalay (1986) which is usually called BBKS or peak theory. This theory is originally used to study the statistical properties of the structure formation in the Universe. Recently, this theory is applied to the study of primordial black holes. ## 2020/6/29 (月)## From scattering amplitudes to binary system †## Hiroaki Tahara †I will briefly introduce a few recent letters which calculate classical Hamiltonian for compact spinless binaries up to third post-Minkowskian order with modern tools for scattering amplitudes. [1] C. Cheung, et al., “From scattering amplitudes to classical potentials in the post-Minkowskian expansion,” PRL 121, no.25, 251101 (2018) [arXiv:1808.02489 [hep-th]]. ## 2020/6/22 (月)## Experiments towards the Quantum Nature of Gravity and the Related Theoretical Challenges †## Tomohiro Fujita †Quantum gravity is one of the most outstanding problems in physics. In fact, we do not know if References: ## 2020/6/15 (月)## de Sitter wave function and Euclidean AdS †## Yusuke Yamada †In cosmology, correlation functions are important observables. One can evaluate them e.g. within the in-in perturbation formalism or using wave functional(=path integral). The wave functional/path integral approach manifests the relation to the path integral in Euclidean AdS. References ## 2020/6/8 (月)## Cosmological superfluids and phonons †## Kohei Kamada †Spontaneous space-time symmetry breaking is now known to be a key to explore cosmology References ## 2020/6/1 (月)## Stochastic dynamics from Quantum mechanics †## Jun'ichi Yokoyama †I will introduce several very old papers to extract References (chronological order) ## 2020/5/25 (月)## Quantum entanglement in the early Universe †## Kouki Tokeshi †The quantum state becomes squeezed after inflation due to cosmological perturbations, and hence there exists quantum entanglement. In this talk, we start with the simplest example which shows quantum entanglement, and see the relation between Hawking temperature of a BH and the entangled particle pair near the horizon, in the viewpoint of themo field dynamics (TFD). After these examples, we consider the quantum squeezed state after inflation, and from the result we finally draw some implications on PBHs. Refs. ## 2020/5/18 (月)## Inhomogeneous nucleosynthesis †## Fumio Uchida †A nonstandard model for big-bang nucleosynthesis (BBN) is introduced in this talk. The standard theory of BBN developed after the famous paper written in 1948 by R. Alpher, H. Bethe, and G. Gamow, to have achieved a great success in describing the abundance of light nuclei in our universe. However, there remain some open questions such as the Lithium 7 problem. Attempts to model inhomogeneous big-bang nucleosynthesis (IBBN) is introduced, and so are the motivations for it and latest results. ## 2020/5/11 (月)## Thermodynamical aspects of gravity and its application. †## Takumi Hayashi †The entropy of the blackhole was proposed by Hawking and others several decades ago and developed into the notion of thermodynamics in gravity. It has still been intensively studied, because it could possibly offer the window to the nature of the quantum gravity such as the microstates of the theory. ## 2020/4/27 (月)## Gravitational Wave Production right after Primordial Black Hole Evaporation †## Keisuke Inomata †We discuss the footprint of evaporation of primordial black holes (PBHs) on stochastic gravitational waves (GWs) induced by scalar perturbations. We consider the case where PBHs once dominate the Universe but eventually evaporate before the big bang nucleosynthesis. The reheating through the PBH evaporation could end with a sudden change in the equation of state of the Universe compared to the conventional reheating caused by particle decay. We show that this "sudden reheating" by the PBH evaporation enhances the induced GWs, whose amount depends on the length of the PBH-dominated era and the width of the PBH mass function. ## 2020/4/20 (月)## Gravitational lensing of gravitational wave †## Junya Kume †The effect of gravitational lensing on the propagation of gravitational wave (GW) have been extensively studied recently. Since the sensitivity of the GW detector improved and many GW events are now observed, we can have the opportunity to observe "lensed" GW. ## 2020/4/13 (月)## Deformation of the gravitational wave spectrum by density perturbations †## Ryusuke Jinno †Abstract: ## 2020/4/6 (月)## Time complexification for particle production †## Soichiro Hashiba †Abstract: ## 2020/3/9 (月)## Introduction to induced second-order gravitational waves †## Minxi He †Abstract: This is a introductory talk about the induced second-order gravitational waves. As we know that gravitational wave (GW) astronomy is now one of the most popular topic in physics. In fact, GW is not only for astronomy but cosmology. The most famous example is the primordial GW predicted by inflation, although that is usually supposed to be detected by CMB b-mode. This talk will focus on higher frequency range of GW which could possibly detected by future interferometer GW detectors. The (non-)detection of these GW will give hints on cosmology, such as distinguishing cosmological models, and primordial black holes. This talk is based on the following papers: https://arxiv.org/abs/gr-qc/0612013 https://arxiv.org/abs/hep-th/0703290 https://arxiv.org/abs/1804.08577 https://arxiv.org/abs/0812.4339 ## 2018/3/12 (月)UTAPwiki/セミナー/初期宇宙・相対論速報 ## 2018/3/5 (月)UTAPwiki/セミナー/初期宇宙・相対論速報 ## 2018/2/27 (火)UTAPwiki/セミナー/初期宇宙・相対論速報 ## 2018/2/26 (月)UTAPwiki/セミナー/初期宇宙・相対論速報 |

Last-modified: 2013-11-20 (水) 11:11:56 (2453d)