Gravitational waves from cosmic bubble collisions

The European Physical Journal C

Dong-Hoon Kim¹  Jongmann Yang²  Wonwoo Lee³  Bum-Hoon Lee⁴  Dong-han Yeom⁵ 

[1] Basic Science Research Institute, Ewha Womans University, 120-750, Seoul, Republic of Korea;Institute for the Early Universe, Ewha Womans University, 120-750, Seoul, Republic of Korea;Basic Science Research Institute, Ewha Womans University, 120-750, Seoul, Republic of Korea;Institute for the Early Universe, Ewha Womans University, 120-750, Seoul, Republic of Korea;Department of Physics, Ewha Womans University, 120-750, Seoul, Republic of Korea;Center for Quantum Spacetime, Sogang University, 121-742, Seoul, Republic of Korea;Center for Quantum Spacetime, Sogang University, 121-742, Seoul, Republic of Korea;Department of Physics, Sogang University, 121-742, Seoul, Republic of Korea;Center for Quantum Spacetime, Sogang University, 121-742, Seoul, Republic of Korea;Yukawa Institute for Theoretical Physics, Kyoto University, 606-8502, Kyoto, Japan;Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, 10617, Taipei, Taiwan;

关键词: Scalar Field;    Gravitational Wave;    Flat Spacetime;    False Vacuum;    True Vacuum;   

DOI  :  10.1140/epjc/s10052-015-3348-2

来源: Springer

【 摘 要 】

Cosmic bubbles are nucleated through the quantum tunneling process. After nucleation they would expand and undergo collisions with each other. In this paper, we focus in particular on collisions of two equal-sized bubbles and compute gravitational waves emitted from the collisions. First, we study the mechanism of the collisions by means of a real scalar field and its quartic potential. Then, using this model, we compute gravitational waves from the collisions in a straightforward manner. In the quadrupole approximation, time-domain gravitational waveforms are directly obtained by integrating the energy-momentum tensors over the volume of the wave sources, where the energy-momentum tensors are expressed in terms of the scalar field, the local geometry and the potential. We present gravitational waveforms emitted during (i) the initial-to-intermediate stage of strong collisions and (ii) the final stage of weak collisions: the former is obtained numerically, in full General Relativity and the latter analytically, in the flat spacetime approximation. We gainqualitative insights into the time-domain gravitational waveforms from bubble collisions: during (i), the waveforms show the non-linearity of the collisions, characterized by a modulating frequency and cusp-like bumps, whereas during (ii), the waveforms exhibit the linearity of the collisions, featured by smooth monochromatic oscillations.

【 授权许可】

CC BY