We study the gravitational waves (GWs) spectrum produced during the electroweak phase transition in a scale-invariant extension of the Standard Model (SM), enlarged by a dark U (1)D gauge symmetry. This symmetry incorporates a vector dark matter (DM) candidate and a scalar field (scalon). Because of scale invariance, the model has only two independent parameters and for the parameter space constrained by DM relic density, strongly first-order electroweak phase transition can take place. In this model, for a narrow part of the parameter space, DM-nucleon cross section is below the neutrino-floor limit, and therefore, it cannot be probed by the future direct detection experiments. However, for a benchmark point form this narrow region, we show the amplitude and frequency of phase transition GW spectrum fall within the observational window of space-based GW detectors such as eLISA.

The thermodynamic properties of the quark gluon plasma (QGP ) as well as its phase diagram are calculated as a function of baryon density (chemical potential) and temperature. The QGP is assumed to be composed of the light quarks only, i.e. the up and the down quarks, which interact weakly and the gluons which are treated as they are free. The interaction between quarks is considered in the framework of the one gluon exchange model which is obtained from the Fermi liquid picture. The bag model is used, with fixed bag pressure (B) for the nonperturbative part and the quantum chromodynamics (QCD) coupling is assumed to be constant i.e. no dependence on the temperature or the baryon density. The effect of weakly interacting quarks on the QGP phase diagram are shown and discussed. It is demonstrated that the one gluon exchange interaction for the massless quarks has considerable effect on the QGP phase diagram and it causes the system to reach to the confined phase at the smaller baryon densities and temperatures. The pressure of excluded volume hadron gas model is also used to find the transition phase-diagram. Our results depend on the values of bag pressure and the QCD coupling constant which the latter does not have a dramatic effect on our calculations . Finally, we compare our results with the thermodynamic properties of strange quark matter and the lattice QCD prediction for the QGP transition critical temperature.

The thick center vortex model with the idea of using domain structures is used to calculate the potentials between two G(2) heavy sources in the fundamental, the adjoint and the 27 dimensional representations. The potentials are screened at large distances. This behavior is expected from the thick center vortex model since G(2) has only a trivial center element which makes no contribution to the average Wilson loop at the large distance regime. A linear potential is obtained at intermediate distances for all representations. This behavior can be explained by the thickness of the vortices (domains) and by defining a flux for the trivial center element of G(2). The role of the SU(3) subgroup of G(2) in the linear regime is also discussed. The string tensions are in rough agreement with the Casimir operators of the corresponding representations.

We study a conformal version of the Standard Model (SM), which apart from SM sector, containing a U D (1) dark sector with a vector dark matter candidate and a scalar field (scalon). In this model the dark sector couples to the SM sector via a Higgs portal. The theory is scaleinvariant in lowest order, therefore the spontaneous symmetry breaking of scale invariance entails the existence of a scalar particle, scalon, with vanishing zeroth-order mass. However, one-loop corrections break scale invariance, so they give mass to the scalon. Because of the scale invariance, our model is subjected to constraints which remove many of the free parameters. We put constraints to the two remaining parameters from the Higgs searches at the LHC, dark matter relic density and dark matter direct detection limits by PandaX-II. The viable mass region for dark matter is about 1-2 TeV. We also obtain the finite temperature one-loop effective potential of the model and demonstrate that finite temperature effects, for the parameter space constrained by dark matter relic density, induce a strongly first-order electroweak phase transition. * syaser.ayazi@semnan.ac.ir † a.mohamadnejad@ut.ac.ir and fermionic loop contributions to the Higgs mass within supersymmetry can also explain the hierarchy problem. However, concerning the null results at the first and second LHC runs [3,4], and other popular theoretical resolutions of the hierarchy problem, such as large extra dimensions, investigating alternative approaches are appealing.As it was mentioned, one approach of addressing the hierarchy problem is the radical assumption that the fundamental theory describing Nature does not have any scale. This idea is well worth considering for its potential to be an sparing solution to the hierarchy problem. The CW mechanism with a Higgs does not work for the electroweak symmetry breaking because the large top mass does not permit radiative breaking of the electroweak symmetry, but, simple extensions of the Higgs sector with additional bosonic degrees of freedom are known to be phenomenologically viable (see, e.g., ). On the other hand, the scale-invariant extension of the Higgs sector, is a generic feature of many DM models with scalar [27][28][29][30][31][32][33][34][35][36][37][38], fermionic [39][40][41][42][43][44][45] and vector [46-52] DM candidates.There are plenty astronomical and cosmological evidences that around 27 percent of the Universe is made of DM. According to the dominant paradigm, DM consists of weakly interacting massive particles (WIMPs) that successfully explain the large scale structures in our Universe.However, the nature of DM is not well understood, and its particle properties such as spin, mass and interactions all are unknown. Therefore, it is not surprising that despite many previous models, there are still opportunities for DM model building.In this paper we consider spin one (vector) gauge fields as DM candidates. Without concerning scale invariance, vector DM [53-72] and some of its theoretical and phenomenological aspe...