Modern Physics Letters A

The dynamics of the accretion flow onto a black hole driven by Poynting flux is discussed in a simplified model of a two-dimensional accretion disk on equatorial plane. In an axisymmetric, stationary and force-free magnetosphere, the accretion flow is described by the three accretion equations obtained from the conservation of stress–energy tensor and one stream equation for a force-free magnetosphere. It is found that the angular velocity of the magnetic surface can be obtained by the dynamics of the accreting matter, . The effect of the magnetic field on the accretion flow is discussed in detail using the paraboloidal type configuration suggested by Blandford in 1976. In numerical analysis, it is demonstrated that the angular velocity of the disk, Ω_D, deviates from the Keplerian angular velocity and the dynamics of the accretion disk is found to depend strongly on the ratio of the accretion rate to the magnetic field strength.

In a model-independent manner, we explore the local implications of a single neutrino oscillation measurement which cannot be reconciled within a three-neutrino theory. We examine this inconsistency for a single region of baseline to neutrino energy L/E. Assuming that sterile neutrinos account for the anomaly, we find that the local demands of this datum can require the addition to the theory of one to three sterile neutrinos. We examine the constraints which can be used to determine when more than one neutrino would be required. The results apply only to a given region of L/E. The question of the adequacy of the sterile neutrinos to satisfy a global analysis is not addressed here. Finally, using the results of a 3+2 analysis, we indicate values for unknown mixing matrix elements which would require two sterile neutrinos due to local demands only.

We consider dominant three-, four- and five-loop contributions to λ, the quartic scalar coupling-constant's β-function in the Standard Model. We find that these terms accelerate the evolution of λ to nonperturbative values, thereby lowering the unification bound for which scalar-couplings are still perturbative. We also find that these higher order contributions imply a substantial lowering of λ itself before the anticipated onset of nonperturbative physics in the Higgs sector.

The cosmological constant on a D-brane is analyzed. This D-brane is in the background produced by the p-brane solutions. The energy–momentum tensor in this model has been found and the form of the cosmological constant has been derived. This energy–momentum tensor is interpreted as an energy–momentum tensor for a perfect fluid on the D-brane. The energy density and the pressure for this fluid have been derived. As it turned out the pressure is negative but the speed of sound is real.

In this paper, we study the possibility of building two-field models of dark energy with equation of state across -1. Specifically we will consider two classes of models: one consists of two scalar fields (quintessence + phantom) and another includes one scalar (phantom) and one spinor field (neutrino). Our studies indicate to some extent that two-field models give rise to a simple realization of the dynamical dark energy model with the equation of state across w=-1.

We study the explicit CP violation of the Higgs sector in the next-to-minimal supersymmetric model with a gauge singlet Higgs field. Our numerical predictions show that electric dipole moment of electron lies around the present experimental upper limits. The mass of the lightest Higgs boson is quite sensitive to the CP violating phases in the theory. It is observed that as the vacuum expectation value of the singlet gets higher values, CP violation increases.

In this work we deal with the extension of the Kaluza–Klein approach to a non-Abelian gauge theory; we show how we need to consider the link between the n-dimensional model and a four-dimensional observer physics, in order to reproduce field equations and gauge transformations in the four-dimensional picture. More precisely, in field equations any dependence on extra coordinates is canceled out by an integration, as consequence of the unobservability of extra dimensions. Thus, by virtue of this extra dimension unobservability, we are able to recast the multidimensional Einstein equations into the four-dimensional Einstein–Yang–Mills ones, as well as all the right gauge transformations of fields are induced. The same analysis is performed for the Dirac equation describing the dynamics of the matter fields and, again, the gauge coupling with Yang–Mills fields are inferred from the multidimensional free fields theory, together with the proper spinors transformations.

The mass of Z′ boson is considered in a flavor-independent phenomenological potential model. We have used the low energy parameters and the estimated value so obtained is accessible to experiments at low energies.