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Self-anisotropizing universe and gravitational waves in Horndeski theory
2018-11-15     Text Size:  A

CAS Key Laboratory of Theoretical Physics

Institute of Theoretical Physics

Chinese Academy of Sciences

Seminar

Title

题目

Self-anisotropizing universe and gravitational waves in Horndeski theory

Speaker

报告人

Hiroaki Tahara

Affiliation

所在单位

Research Center for the Early Universe, University of Tokyo

Date

日期

2018年11月15日(周四)上午10:00

Venue

地点

Conference Room 6420, ITP new building

Abstract

摘要

As opposed to Wald’s cosmic no-hair theorem in general relativity, we find that the Horndeski theory admits anisotropic inflationary attractors if the Lagrangian depends cubically on the second derivatives of the scalar field. We name such a solution a self-anisotropizing inflationary universe, because anisotropic inflation can occur without introducing any anisotropic matter fields such as a vector field. Next, we investigate perturbations in homogeneous anisotropic background, and find that speed of gravitational waves depend on direction of its propagation. This investigation reveals, however, that the speed of gravitational waves in some directions diverges in the self-anisotropizing inflationary background and it suggests unfitness for representing our present universe. On the other hand, it is also revealed that as long as our universe is anisotropic, speed of gravitational waves can have angular dependence. Such a nature is not seen in general relativity, and it shows us abundance of phenomenology in Horndeski theory.

Contact Person

所内联系人

Rong-Gen Cai
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