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Register a new userPhase transition gravitational waves from pseudo-Nambu-Goldstone dark matter and two Higgs doublets
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We investigate the potential stochastic gravitational waves from first-order electroweak phase transitions in a model with pseudo-Nambu-Goldstone dark matter and two Higgs doublets. The dark matter candidate can naturally evade direct detection bounds, and can achieve the observed relic abundance via the thermal mechanism. Three scalar fields in the model obtain vacuum expectation values, related to phase transitions at the early Universe. We search for the parameter points that can cause first-order phase transitions, taking into account the existed experimental constraints. The resulting gravitational wave spectra are further evaluated. Some parameter points are found to induce strong gravitational wave signals, which have the opportunity to be detected in future space-based interferometer experiments LISA, Taiji, and TianQin.
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The idea to have Higgs doublets as pseudo Nambu-Goldstone (PsNG) multiplet is examined in the framework of supersymmetric E_6 unified theory. We show that extra PsNG multiplets other than the expected Higgs doublets necessarily appear in the E_6 case. If we demand that the extra PsNG multiplets neither disturb the gauge coupling unification nor make the color gauge coupling diverge before unification occurs, only possibility for the extra PsNG is 10+bar{10} of SU(5). This is realized when the symmetry breaking E_6 to SO(10) occurs in the phi(27)+phi(bar{27}) sector while E_6 to SU(4)_Ctimes SU(2)_Ltimes U(1)times U(1) in the Sigma(78) sector. The existence of 10+bar{10} multiplets with mass around 1 TeV is therefore a prediction of this E_6 PsNG scenario. Implication of their existence on the proton decay is also discussed.
If dark matter (DM) acquires mass during a first order phase transition, there will be a filtering-out effect when DM enters the expanding bubble. In this paper we study the filtering-out effect for a pseudo-scalar DM, whose mass may partially come from a first order phase transition in the hidden sector. We calculate the ratio of DM that may enter the bubble for various bubble wall velocities as well as various status of DM (in the thermal equilibrium, or out of the thermal equilibrium) at the time of phase transition, which results in small penetration rate that may affect the final relic abundance of the DM. We further study the stochastic gravitational wave signals emitted by the hidden sector phase transition at the space-based interferometer experiments as the smoking-gun of this model.
We investigate first order phase transitions in a holographic setting of five-dimensional Einstein gravity coupled to a scalar field, constructing phase diagrams of the dual field theory at finite temperature. We scan over the two-dimensional parameter space of a simple bottom-up model and map out important quantities for the phase transition: the region where first order phase transitions take place; the latent heat, the transition strength parameter $alpha$, and the stiffness. We find that $alpha$ is generically in the range 0.1 to 0.3, and is strongly correlated with the stiffness (the square of the sound speed in a barotropic fluid). Using the LISA Cosmology Working Group gravitational wave power spectrum model corrected for kinetic energy suppression at large $alpha$ and non-conformal stiffness, we outline the observational prospects at the future space-based detectors LISA and TianQin. A TeV-scale hidden sector with a phase transition described by the model could be observable at both detectors.
Motivated by recent constructions of TeV-scale strongly-coupled dynamics, either associated with the Higgs sector itself as in pseudo-Nambu-Goldstone boson (pNGB) Higgs models or in theories of asymmetric dark matter, we show that stable solitonic Q- balls can be formed from light pion-like pNGB fields carrying a conserved global quantum number in the presence of the Higgs field. We focus on the case of thick-wall Q-balls, where solutions satisfying all constraints are shown to exist over a range of parameter values. In the limit that our approximations hold, the Q-balls are weakly bound and parametrically large, and the form of the interactions of the light physical Higgs with the Q-ball is determined by the breaking of scale symmetry.
We propose a novel scenario of Dark Matter production naturally connected with generation of gravitational waves. Dark Matter is modelled as a real scalar, which interacts with the hot primordial plasma through a portal coupling to another scalar field. For a particular sign of the coupling, this system exhibits an inverse second order phase transition. The latter leads to an abundant Dark Matter production, even if the portal interaction is so weak that the freeze-in mechanism is inefficient. The model predicts domain wall formation in the Universe, long time before the inverse phase transition. These domain walls have a tension decreasing with time, and completely disappear at the inverse phase transition, so that the problem of overclosing the Universe is avoided. The domain wall network emits gravitational waves with characteristics defined by those of Dark Matter. In particular, the peak frequency of gravitational waves is determined by the portal coupling constant, and falls in the observable range for currently planned gravitational wave detectors.
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