Modern Physics Letters A

The flavor-changing neutral current transition b → s can serve as a sensitive probe of WIMP dark matter models, if the WIMP mass is under 2 GeV. In this work we extend our earlier analysis to a generic class of models where the interaction between the dark matter sector and the Standard Model matter sector is mediated by the Higgs boson(s). We show that experimental limits on the decays of B-mesons to K(K*) and missing energy provide stringent constraints on the parameter space of such models, but do not rule out sub-GeV WIMPs in a model-independent way. We find that in the context of the NMSSM with light pseudoscalar Higgs, the WIMP masses under a few hundred MeV are generically excluded with the exception of few highly tuned points in the parameter space.

One of the main aims in the next generation of precision cosmology experiments will be an accurate determination of the equation of state (EOS) for the dark energy (DE). If the latter is dynamical, the resulting barotropic index ω should exhibit a nontrivial evolution with the redshift. This is usually interpreted as a sign that the mechanism responsible for the DE is related to some dynamical scalar field, and in some cases this field may behave non-canonically (phantom field). Present observations seem to favor an evolving DE with a potential phantom phase near our time. In the literature, there is a plethora of dynamical models trying to describe this behavior. Here we show that the simplest option, namely a model with a variable cosmological term, Λ = Λ(t), leads in general to a nontrivial effective EOS, with index ω_e, which may naturally account for these data features. We prove that in this case there is always a "crossing" of the ω_e = -1 barrier near our time. We also show how this effect is modulated (or even completely controlled) by a variable Newton's gravitational coupling G = G(t).

We use the Einstein energy–momentum complex to calculate the energy distribution of static plane-symmetric solutions of the Einstein–Maxwell equations in 3+1 dimensions with asymptotic anti-de Sitter behavior. This solution is expressed in terms of three parameters: the mass, electric charge and cosmological constant. We compare the energy distribution to that of the Reissner–Nordström–anti-de Sitter solution, pointing to qualitative differences between the models. Finally, we examine these results within the context of the Cooperstock hypothesis.

We consider a few topics in E₁₁ approach to superstrings/M-theory: even subgroups (Z₂ orbifolds) of E_n, n = 11, 10, 9 and their connection to Kac–Moody algebras, particularly to EE₁₁ subgroup of E₁₁; possible form of supersymmetry relation in E₁₁; decomposition of first fundamental representation l₁ w.r.t. the SO(10, 10) and its square-root at first few levels; particle orbit of l₁ ⋉ E₁₁. Possible relevance of coadjoint orbits method is noticed, based on a self-duality form of equations of motion in E₁₁.

In this paper, we argue that the log-area type correction to black hole entropy is also obtained from a gravitationally-induced modification to de Broglie wave-particle duality. A formula for the corrected temperature is presented. The negative temperature might be an interesting hint, although its meaning is still unclear. We make comparisons between our work and relevant literatures.

According to the Campbell–Magaard theorem, any analytical spacetime can be locally and analytically embedded into a five-dimensional pseudo-Riemannian Ricci-flat manifold. This embedding for Gödel's universe can be found. The embedding space is Ricci-flat and has a non-Lorentzian signature of type (+ + - - -). We also show that the embedding found is global.