The gravitational waves from the collapsing domain walls in the complex singlet model
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Springer
Received: April 26, Revised: July 5, Accepted: July 25, Published: August 25,
2020 2020 2020 2020
Ning Chen,a Tong Lia and Yongcheng Wub a
School of Physics, Nankai University, Tianjin 300071, China b Ottawa-Carleton Institute for Physics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6, Canada
E-mail: chenning [email protected], [email protected], [email protected] Abstract: We study the CP domain walls and the consequent gravitational waves induced by the spontaneous breaking of the CP symmetry in the complex singlet extension to the Standard Model. We impose the constraints from the unitarity, stability and the global minimal of the vacuum solutions on the model parameter space. The CP domain wall profiles and tensions are obtained by numerically solving the relevant field equations. The explicit CP violation terms are then introduced to the potential as biased terms to make the domain walls unstable and collapse, The BBN bound on the magnitude of the energy bias is taken into account. To achieve sufficiently strong gravitational wave signals, the domain wall tension σ is required to be at least σ/TeV3 ∼ O(103 ). We find that the gravitational wave spectrum can be probed in the future SKA and/or DECIGO programs, when the typical mass scale is at least ∼ O(10) TeV and the explicit CP violation terms are as small as O(10−24 )−O(10−23 ). The gravitational waves from collapsing domain walls thus provide a complementarity to the probe of extremely small CP violation at high-energy scale. Keywords: Beyond Standard Model, Cosmology of Theories beyond the SM, CP violation ArXiv ePrint: 2004.10148
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP08(2020)117
JHEP08(2020)117
The gravitational waves from the collapsing domain walls in the complex singlet model
Contents 1
2 The complex singlet extension to the SM 2.1 The mass spectrum with the SCPV and the broken Z2 symmetry 2.2 The theoretical constraints: unitarity, stability, and the global minimal 2.2.1 The perturbative unitarity 2.2.2 The stability of the tree-level potential 2.2.3 The global minimum condition
3 4 6 6 7 8
3 The CP domain walls in the cxSM 3.1 The CP domain wall solution 3.2 The biased terms in the cxSM
9 9 10
4 The GWs from the collapsing domain wall 4.1 The constraints and predictions to the GW signals 4.2 The future probes of the GWs
11 11 13
5 Summary
15
A The stability of the potential
16
1
Introduction
Topological defects, realized as some non-trivial vacuum objects in the early Universe, can arise as a result of the spontaneous breaking of symmetries in new physics beyond the Standard Model (SM) [1–4]. A well-known example is the formation of domain walls which occur when a discrete symmetry is spontaneously broken. Since the discovery of the gravitational waves (GW) by the LIGO/Virgo collaboration [5, 6], it is widely believed that the further probes of various GW signals in different frequencies can provide an unprecedented window to the new phy
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