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We study the superheavy dark matter (DM) scenario in an extended $B-L$ model, where one generation of right-handed neutrino $ u_R$ is the DM candidate. If there is a new lighter sterile neutrino that co-annihilate with the DM candidate, then the annihilation rate is exponentially enhanced, allowing a DM mass much heavier than the Griest-Kamionkowski bound ($sim10^5$ GeV). We demonstrate that a DM mass $M_{ u_R}gtrsim10^{13}$ GeV can be achieved. Although beyond the scale of any traditional DM searching strategy, this scenario is testable via gravitational waves (GWs) emitted by the cosmic strings from the $U(1)_{B-L}$ breaking. Quantitative calculations show that the DM mass $mathcal{O}(10^9-10^{13}~{rm GeV})$ can be probed by future GW detectors.
Domain walls can form after breakdown of a discrete symmetry induced by first-order phase transition, we study the heavy dark matter produced around the temperature of the phase transition that yields the breakdown of a $mathbb{Z}_{3}$ symmetry. The
We discuss the gravitational creation of superheavy particles $chi$ in an inflationary scenario with a quartic potential and a non-minimal coupling between the inflaton $varphi$ and the Ricci curvature: $xi varphi^2 R/2$. We show that for large const
The direct detection of gravitational waves offers an exciting new window onto our Universe. At the same time, multiple observational evidence and theoretical considerations motivate the presence of physics beyond the Standard Model. In this thesis,
We present the relation between the sphaleron energy and the gravitational wave signals from a first order electroweak phase transition. The crucial ingredient is the scaling law between the sphaleron energy at the temperature of the phase transition
The $U(1)_{B-L}$ gauge symmetry is a promising extension of the standard model of particle physics, which is supposed to be broken at some high energy scale. Associated with the $U(1)_{B-L}$ gauge symmetry breaking, right-handed neutrinos acquire the