Modern Physics Letters A

Here, we discuss the cosmological consequences of a previous suggested model for the case K = ±1. It is shown that the model covers the whole observed ranges for the Hubble's constant, the age of the universe and the density parameter.

Methods are described in the framework of light-cone expansion which allow one to determine the Cabibbo–Kobayashi–Maskawa matrix elements |V_ub| and |V_cb| from measurements of the differential decay rates as a function of the scaling variables in the inclusive semileptonic decays of B mesons. By these model-independent methods the dominant hadronic uncertainties can be avoided and the B→ X_uℓν decay can be very efficiently differentiated from the B→ X_cℓν decay, which may lead to precise determinations of |V_ub| and |V_cb|.

The production of string charge during a crossing of certain oriented D-branes is studied. We compute the string charge in the system of a probe D2-brane and a background D6-brane by using the equations of motion in ten dimensions. We confirm the creation of string charge as inflow from the background D6-brane.

The production of electron–positron pairs in a time-dependent magnetic field is estimated in the hypotheses that the magnetic field is uniform over large distances with respect to the pair localization and it is so strong that the spacing of the Landau levels is larger than the rest mass of the particles. This calculation is presented since it has been suggested that extremely intense and varying magnetic fields may be found around some astrophysical objects.

A nonlocal gauge symmetry of a complex scalar field, which can be trivially extended to spinor fields, was demonstrated in a recent paper (Mod. Phys. Lett.A13, 1265 (1998), hep-th/9902020). The corresponding covariant Lagrangian density yielded a new, nonlocal quantum electrodynamics. In this letter we show that as a consequence of this new QED, a black body radiation viewed through gaseous matter appears to show a slight deviation from the Planck formula, and propose an experimental test to check this effect. We also show that a non-uniformity in this gaseous matter distribution leads to an (apparent) spatial anisotropy of the black body radiation.

When neutrinos travel through a normal matter medium, the electron neutrinos couple differently to gravity compared to the other neutrinos, due to the presence of electrons in the medium and the absence of the other charged leptons. The matter-induced gravitational couplings of the neutrinos under such conditions are calculated and their contribution to the neutrino index of refraction in the presence of a gravitational potential is determined.

In this work we have constructed the most general action for a set of complex homogeneous scalar supermultiplets interacting with the scale factor in the supersymmetric FRW model. It is shown that the local conformal time supersymmetry leads to a scalar field potential defined in terms of the Kähler potential and superpotential in the same combination as in supergravity (or effective superstring) theories. This scalar field potential depends on an arbitrary parameter α which is not fixed by conformal time supersymmetry and induces the spontaneous breaking of supersymmetry in supergravity theories.

Starting from determinants at finite temperature obeying an intermediate boundary condition between the periodic (bosonic) and antiperiodic (fermionic) cases, we find results which can be mapped onto those obtained from anyons for the second virial coefficient. Using this approach, we calculate the corresponding higher virial coefficients and compare them with the results in the literature.