Modern Physics Letters A

In this review we demonstrate physics potential of a photon linear collider by studying the neutral Higgs–boson sector of the MSSM in which interesting CP-violating Higgs mixing could arise via radiative corrections.

Using the mechanism of spontaneous symmetry breaking of scale invariance obtained from the dynamics of maximal rank field strengths, it is possible to spontaneously generate confining behavior. Introducing a dilaton field, the study of nontrivial confining and de-confining transitions appears possible. This is manifest in two ways at least: One can consider bags which contain an unconfined phase in the internal region and a confined phase outside and also one obtains a simple model for deconfinement at high temperature from the finite temperature dynamics of the dilaton field.

The no-scalar-hair conjecture rules out the existence of asymptotically flat black holes with a scalar dressing for a large class of theories. No-scalar-hair theorems have been proved for the cases of neutral black holes and for charged black holes in the Maxwell electrodynamics. These theorems, however, do not apply in the case of nonlinear electrodynamics. In the present work numerical solutions describing charged black holes coupled to Euler–Heisenberg type nonlinear electrodynamics in scalar–tensor theories of gravity with massless scalar field are found. In comparison to the corresponding solution in General Relativity the presented solution has a simpler causal structure the reason for which is the presence of the scalar field. The present class of black holes has a single, nondegenerate horizon, i.e. its causal structure resembles that of the Schwarzschild black hole.

We construct a class of nuclear equations of state based on a schematic potential model, that originates from the work of Prakash et al.,¹ which reproduce the results of most microscopic calculations. The equations of state are used as input for solving the Tolman–Oppenheimer–Volkov equations for the corresponding neutron stars. The potential part contribution of the symmetry energy to the total energy is parametrized in a generalized form both for low and high values of the baryon density. Special attention is devoted to the construction of the symmetry energy in order to reproduce the results of most microscopic calculations of dense nuclear matter. The obtained nuclear equations of state are applied for the systematic study of the global properties of a neutron star (masses, radii and composition). The calculated masses and radii of the neutron stars are plotted as a function of the potential part parameters of the symmetry energy. A linear relation between these parameters, the radius and the maximum mass of the neutron star is obtained. In addition, a linear relation between the radius and the derivative of the symmetry energy near the saturation density is found. We also address the problem of the existence of correlation between the pressure near the saturation density and the radius.

We compute a Chern–Simons term induced by the fermions on noncommutative torus interacting with two U(1) gauge fields. For rational noncommutativity θ∝P/Q we find a new mixed term in the action which involves only those fields which are (2π)/Q periodic, like the fields in a crystal with Q² nodes.

The string inspired higher dimensional theories suggest modification of Newton's law at submillimeter length scales. Inter-particle distances in white dwarf and neutron stars are 10^-10 cms and 10^-13 cms respectively, and therefore, the effects of short distance corrections to gravity deserve investigation. We show, by carrying out explicit analytical many-body calculations that, in the presence of corrections, the normal state of these compact stars become metastable. The actual quantum mechanical ground state of the stars turns out to be unstable. However, the tunneling probability to the unstable ground state is so small that the stars may remain trapped in the metastable state practically forever.