Modern Physics Letters A

Lovelock theory is a natural extension of Einstein theory of gravity to higher dimensions, and it is of great interest in theoretical physics as it describes a wide class of models. In particular, it describes string theory inspired ultraviolet corrections to Einstein–Hilbert action, while admits the Einstein general relativity and the so-called Chern–Simons theories of gravity as particular cases. Here, we give an introduction to the black hole solutions of Lovelock theory and analyze their most important properties. These solutions can be regarded as generalizations of the Boulware–Deser solution of Einstein–Gauss–Bonnet gravity, which we discuss in detail here. We briefly discuss some recent progress in understanding these and other solutions, like topological black holes that represent black branes of the theory, and vacuum thin-shell wormhole-like geometries that connect two different asymptotically de Sitter spaces. We also make some comments on solutions with time-like naked singularities.

The spectroscopy of S-wave heavy-baryons containing one, two or three heavy quarks is investigated in a constituent quark model. We solve the Schrödinger equation for three particles exactly by means of a Gaussian expansion method. The calculated results of heavy-baryon spectra with a single heavy quark are consistent with the experimental data.

A new technique for constructing the relativistic wave equation for the two-body system composed of the spin-1/2 and spin-0 particles is proposed. The method is based on the extension of the SL(2, C) group to the Sp(4, C) one. The obtained equation includes the interaction potentials, having both the Lorentz-vector and Lorentz-tensor structure, exactly describes the relativistic kinematics and possesses the correct one-particle limits. The comparison with results of other approaches to this problem is discussed.

We discuss the moduli space singularities that are generally present in five-dimensional vector-coupled supergravity on a spacetime of the form ℝ⁴ × S¹/ℤ₂, with vector fields surviving on the ℤ₂ fixed planes. The framework of supergravity is necessarily ambiguous when it comes to the non-singular embedding theory, so we focus on those models coming from Calabi–Yau threefold with wrapped membranes.

Considering that gravitational force might deviate from Newton's inverse-square law and become much stronger in small scale, we present a method to detect the possible existence of extra dimensions in the ADD model. By making use of an effective variational wave function, we obtain the nonrelativistic ground energy of a helium atom and its isoelectronic sequence. Based on these results, we calculate gravity correction of the ADD model. Our calculation may provide a rough estimation about the magnitude of the corresponding frequencies which could be measured in later experiments.

Axions are the possible candidates for the non-baryonic dark matter in the Universe. Numerical calculation suggest that, these axions clumped together to form denser objects like miniclusters and axion boson stars. We have calculated the damping of cosmic rays mainly electrons propagating in the dark halo of our own galaxy, which suppose to contains the axionic dark matter as miniclusters. Our calculation shows that almost all the high energy cosmic rays will penetrate through these objects without losing energy.

In this paper, we propose a free energy for general non-supersymmetric black hole attractors (with vanishing D0-brane charge) arising in type IIA(B) superstrings on 3-fold Calabi–Yau, in the supergravity limit. This, by definition, differs from its counterpart BPS free energy by a factor of 4. Correspondingly, a mixed ensemble for these black holes is proposed.