Modern Physics Letters A

Free neutron beta decay is the simplest nuclear beta decay and the prototype charged-current semileptonic decay. It has some theoretical advantage over other nuclear decay systems in that there are no nuclear structure corrections, and it is the only mixed Fermi/Gamow–Teller beta decay for which the relative matrix elements can be directly calculated. The status of the electron–antineutrino angular correlation (a-coefficient) in neutron beta decay and its role in elucidating fundamental properties of the weak interaction are reviewed, with an emphasis on experiments. A new generation of experiments intended to reduce the uncertainty in the a-coefficient to less than 1% is described.

The infrared behavior of Yang–Mills theory at finite temperature provides access to the role of confinement. In this review recent results on this topic from lattice calculations and especially Dyson–Schwinger studies are discussed. These indicate persistence of a residual confinement even in the high-temperature phase. The confinement mechanism is very similar to the one in the vacuum for the chromomagnetic sector. In the chromoelectric sector screening occurs at the soft scale g²T, although not leading to a perturbative behavior.

The relativistic generalization of Faddeev–Yakubovsky approach is constructed in the form of the dispersion relations. The five-quark amplitudes for the low-lying pentaquarks including the u-, d-, s-quarks are calculated. The poles of these amplitudes determine the masses and widths of θ-pentaquarks.

In this paper two consequences of the generalized uncertainty principle (GUP) are discussed in a heuristic manner. Both could be regarded as the evidences that prefer the cosmic censorship hypothesis (CCH). The first one is that the second law tends to decline the massless charged particles if the effects of the GUP on the thermodynamics of a de Sitter spacetime are considered. This weakens the threat to the horizon of an extreme charged black hole. The second one is that the uv/ir correspondence provides a constraint on the relation between the energy and the size of a system, which is incompatible to the naked singularities.

It is shown that among the different classes of claimed static wormhole solutions of the vacuum Brans–Dicke theory only Brans Class I solution with coupling constant ω less than -1.5 (excluding the point ω = 2) gives rise to physically viable traversable wormhole geometry. Usability of this wormhole geometry for interstellar travel has been examined.

We study , i = e, μ, τ decays in the two-Higgs doublet model, with the inclusion of one and two spatial non-universal extra dimensions. We observe that the branching ratio is sensitive to two extra dimensions in contrary to a single extra dimension.