International Journal of Modern Physics A

Asymmetric dark matter models are based on the hypothesis that the present-day abundance of dark matter has the same origin as the abundance of ordinary or "visible" matter: an asymmetry in the number densities of particles and antiparticles. They are largely motivated by the observed similarity in the mass densities of dark and visible matter, with the former observed to be about five times the latter. This review discusses the construction of asymmetric dark matter models, summarizes cosmological and astrophysical bounds, and touches on direct detection prospects and collider signatures.

We study two fermionic systems that have an underlying supersymmetric structure, namely a color superconductor and Dirac fermion in a Reissner–Nordström–anti-de Sitter gravitational background. In the chiral limit of the color superconductor, the localized fermionic zero modes around the vortex form an N = 2 with zero central charge d = 1 quantum algebra, with all the operators being Fredholm. We compute the Witten index of this algebra and we find an unbroken supersymmetry. The fermionic gravitational system in the chiral limit too, has two underlying unbroken N = 2, d = 1 supersymmetric algebras. The unbroken supersymmetry in the later is guaranteed by the existence of fermionic quasinormal modes in the Reissner–Nordström–anti-de Sitter background. In this case the operators are not Fredholm and regularized indices are deployed.

We compare the recently formulated multifractional spacetimes with field theories of quantum gravity based on the renormalization group (RG), such as asymptotic safety and Hořava–Lifshitz gravity. The change of spacetime dimensionality with the probed scale is realized in both cases by an adaptation of the measurement tools ("rods") to the scale, but in different ways. In the multifractional case, by an adaptation of the position-space measure, which can be encoded into an explicit scale dependence of effective coordinates. In the case of RG-based theories, by an adaptation of the momenta. The two pictures are mapped into each other, thus presenting the fractal structure of spacetime in RG-based theories under an alternative perspective.

The time-varying gravitational field produced by a Weber bar is used to explore physical and mathematical features of the linearized Einstein equation. We present a self-contained formal framework for the treatment of the linear field, that is applicable to several sources for which the standard quadrupolar formulas are not adequate. The expressions for retarded integrals reveal a singularity associated with boundary conditions. Results from the transverse traceless subgauge are compared with the radiation calculated from retarded integrals. Lienard–Wiechert potentials are used in a treatment of the Weber bar as a collection of point particles and further possible applications are outlined. The Riemann tensor clarifies the transition from near-field geodesic forces to tidal forces in the far field.

If a Higgs field is conformally coupled to gravity, then it can give rise to the scale invariant density perturbations. We make use of this result in a realistic inert Higgs doublet model, where we have a pair of Higgs doublets conformally coupled to the gravity in the early universe. The perturbation of the inert Higgs is shown to be the scale invariant. This gives rise to the density perturbation observed through CMB by its couplings to the standard model Higgs and the subsequent decay. Loop corrections of this conformally coupled system gives rise to electroweak symmetry breaking. We constrain the couplings of the scalar potential by comparing with the amplitude and spectrum of CMB anisotropy measured by WMAP and this model leads to a prediction for the masses of the lightest Higgs and the other scalars.

The influence of an external electromagnetic field on the vacuum structure of a quantized Dirac field is investigated by considering the quantum corrections to classical Maxwell's Lagrangian density induced by fluctuations of the nonperturbative vacuum. Effective Lagrangian densities for Maxwell's theory in (3 + 1) and (2 + 1) dimensions are derived from the vacuum zero-point energy of the fermion field in the context of a consistent Pauli–Villars–Rayski subtraction scheme, recovering Euler–Kockel–Heisenberg and Maxwell–Chern–Simons effective theories. Effective Scalar Quantum Electrodynamics is also discussed.

In this paper, we analytically investigate the properties of Weyl's corrected p-wave holographic superconductors by the matching method. The relation between the critical temperature T_c and the charge density ρ has been obtained as T_c ∝ ρ^⅓ and the dependence of the expectation value of the condensation operator on the temperature has been found analytically in the form . The critical exponent of the condensation also comes out to be ½, which is the universal value in the mean field theory and which has nothing to do with the Weyl coupling γ. Our results are in very good agreement with the existing numerical results and have been obtained using the variational method.

The slope and curvature of Isgur–Wise function for B_c meson is computed in a QCD potential model in two different approaches of choosing the perturbative term of the Cornell potential. Based on heavy quark effective theory the exclusive semileptonic decay rates of B_c meson into the states are exploited. Spin symmetry breaking effects are ignored up to a particular point and the form factors are connected with Isgur–Wise function for other kinematic point since the recoil momentum of from B_c is small due to its heavy mass.