The detection of GW170817 and its electromagnetic counterpart has revealed the speed of gravitational waves coincides with the speed of light, cT= 1. Inspired by the possibility that the physics implied by GW170817 mi...The detection of GW170817 and its electromagnetic counterpart has revealed the speed of gravitational waves coincides with the speed of light, cT= 1. Inspired by the possibility that the physics implied by GW170817 might be related with that for the primordial universe, we construct the spatially ?at stable(throughout the whole evolution)nonsingular bounce models in the beyond Horndeski theory with cT= 1 and in the degenerate higher-order scalar-tensor(DHOST) theory with cT= 1, respectively. Though it constricts the space of viable models, the constraint of cT= 1 makes the procedure of building models simpler.展开更多
First, we do a Taylor series expansion of Entropy. Afterwards we define the arrow of time. After that, we define what terms we will analyze in the Taylor series expansion of entropy to help in finding initial conditio...First, we do a Taylor series expansion of Entropy. Afterwards we define the arrow of time. After that, we define what terms we will analyze in the Taylor series expansion of entropy to help in finding initial conditions which may allow for the earliest possible identification of the Arrow of Time in cosmology. Definition of the arrow of time will allow choosing different initial starting points. That is, that in the actual equations of classical GR, there is no reason to have time asymmetry after given initial conditions. Time asymmetry is built into initial conditions and we start to explore which initial conditions may assist in evaluating contributions to Entropy via an analysis of which terms in a Taylor series survive, and what their sign and contribution values are.展开更多
基金Supported by National Natural Science Foundation of China under Grant Nos.11575188 and 11690021
文摘The detection of GW170817 and its electromagnetic counterpart has revealed the speed of gravitational waves coincides with the speed of light, cT= 1. Inspired by the possibility that the physics implied by GW170817 might be related with that for the primordial universe, we construct the spatially ?at stable(throughout the whole evolution)nonsingular bounce models in the beyond Horndeski theory with cT= 1 and in the degenerate higher-order scalar-tensor(DHOST) theory with cT= 1, respectively. Though it constricts the space of viable models, the constraint of cT= 1 makes the procedure of building models simpler.
文摘First, we do a Taylor series expansion of Entropy. Afterwards we define the arrow of time. After that, we define what terms we will analyze in the Taylor series expansion of entropy to help in finding initial conditions which may allow for the earliest possible identification of the Arrow of Time in cosmology. Definition of the arrow of time will allow choosing different initial starting points. That is, that in the actual equations of classical GR, there is no reason to have time asymmetry after given initial conditions. Time asymmetry is built into initial conditions and we start to explore which initial conditions may assist in evaluating contributions to Entropy via an analysis of which terms in a Taylor series survive, and what their sign and contribution values are.
