Modern Physics Letters A

This review briefly describes light dark matter searches performed by the BABAR experiment. Although dark matter candidates have traditionally been associated with heavy particles appearing in extensions of the Standard Model, a lighter component remains a well-motivated alternative, and many scenarios of light dark matter have been recently proposed. Thanks to their large luminosities, B factories offer an ideal environment to probe these possibilities, complementing searches from direct detection and satellite experiments.

The GSI anomaly brings the theoretical controversy whether the total amplitude of the electron capture (EC) decay is the coherent sum of the amplitude of the different massive neutrino channel. According to the coherent interpretation, the oscillation of the EC decay rate is the result of the flavor state of the neutrino and the time scale of order 10–100 s. We find that the introduction of the flavor state and that of the nonzero time scale in the frame of the time-dependent perturbation theory would bring the considerable flavor violation in the total decay rate, which is in contradiction with the micro-causality. Employing the correct time scale t(t≪1 s), the right EC decay rate is obtained which is the result of the incoherent sum of the component probability with the mass eigenstates. Accordingly, there is no oscillation term in the total decay rate.

In this paper, we work with teleparallel gravity and show that the values of the torsion vector and the torsion axial-vector depend on the choice of the tetrad field. We choose two different sets of tetrad fields, each of them satisfies the tetrad's conditions and leads to the Van Stockum spacetime. We obtain expressions for the torsion vector and the torsion axial-vector. In addition, we found that the obtained expressions are quite different for the two sets of tetrad fields. For the spacetime under consideration, if the metric coefficients are assumed to be functions of t only, it is then shown that the torsion axial-vector vanishes completely and the torsion vector still depends on the choice of tetrad fields. Finally, we found the spin precession of a Dirac particle in the spacetime under consideration.

In this work, we reconstruct the f(R) modified gravity for different ghost and generalized-ghost dark energy (DE) models in FRW flat universe, which describes the accelerated expansion of the universe. The equation of state and deceleration parameter of reconstructed f(R) gravity have been calculated. The equation of state and deceleration parameter of reconstructed f(R)-ghost/generalized-ghost DE, have been calculated. We show that the corresponding f(R) gravity of ghost/generalized-ghost DE model can behave like phantom or quintessence. Also the transition between deceleration to acceleration regime is indicated by deceleration parameter diagram for reconstructed f(R) generalized-ghost DE model.

Brane inflationary universe model in the context of logamediate inflation is studied. As the energy density we consider two different fields, first a standard scalar field, and then a tachyon field. In the high-energy limit we describes the conditions for theses models. The parameters of our models are constrained from the observational data.

We report the results of neutron measurements carried out during the application of ultrasounds to bars of iron and steel. Like in our previous similar works with cavitated solutions of iron, neutrons were emitted in bursts and the spectrum of this peculiar emission was measured for the first time. A further and very interesting outcome of these experiments was the unexpected appearance of circular, macroscopical and regular damages on the lateral surface of the bars which was not directly in contact with the sonotrode. The superficial elemental microanalysis on these spots showed some interesting and macroscopic departures of the concentration of chemical elements from that of the undamaged surface, which may suggest that, along with the emission of neutrons, some transmutations occurred as well.

The BCFW recursion relation allows to find out the tree-level scattering amplitudes for gluons and tensor gauge bosons in generalized Yang–Mills theory. We demonstrate that the corresponding MHV amplitudes for the tensor gauge bosons of spin-s and n gluons are invariant under conformal group of transformations. This is highly unexpected result for the higher-spin particles, in particular this is not true for the scattering amplitudes of gravitons. We discuss and compare the tree-level scattering amplitudes for the charged tensor bosons with the corresponding scattering amplitudes for gravitons, stressing their differences and similarities.