Modern Physics Letters A

Certain exact solutions of the Einstein field equations over nonsimply-connected manifolds are reviewed. These solutions are spherically symmetric and have no curvature singularity. They provide a regularization of the standard Schwarzschild solution with a curvature singularity at the center. Spherically symmetric collapse of matter in ℝ⁴ may result in these nonsingular black-hole solutions, if quantum-gravity effects allow for topology change near the center or if nontrivial topology is already present as a remnant from a quantum spacetime foam.

We employ the simple analytic method and the variational method of the Strum–Liouville (S–L) eigenvalue problem to analytically study the holographic superconductor phase transition in Gauss–Bonnet gravity with Born–Infeld (BI) electrodynamics in the probe limit, respectively. We find that the scalar hair formation at low temperatures is indeed affected by the Gauss–Bonnet as well as the BI coupling parameters, but also by the scalar field mass and the spacetime dimensional. Our analytic result has been found in agreement with the numerical results.

We study the interaction of Λ-hyperon with proton and neutron inside a nucleus within the framework of relativistic mean field (RMF) formalism. The single-particle energy levels for some of the specific proton and neutron orbits are analyzed with the addition of Λ-successively. The neutron energy level is more deeper, because of decrease in symmetry energy due to substitution of neutron by Λ-hyperon.

We study the two-dimensional harmonic oscillator on a noncommutative plane. We show that by introducing appropriate Bopp shifts, one can obtain the Hamiltonian of a two-dimensional harmonic oscillator on a sphere according to the Higgs model. By calculating the commutation relations, we show that this noncommutativity is strictly dependent on the curvature of the background space. In other words, we introduce a kind of duality between noncommutativity and curvature by introducing noncommutativity parameters as functions of curvature. Also, it is shown that the physical realization of such model is a charged harmonic oscillator in the presence of electromagnetic field.

We compute the one-loop threshold corrections to hard supersymmetric relations involving gauge and gaugino couplings for the case of a Split-SUSY-like spectrum with moderate splitting. We show that these contributions are small, however in principle they will typically have to be taken into account if the heavy scalar sector is below 100 TeV and if one reaches, at future linear colliders, the precision that is necessary to perform this kind of measurements.

Two new low-lying ⁶He levels at excitation energies of about 2.4 MeV and 2.9 MeV were observed in the experimental investigation of the p-α coincidence spectra obtained by the ³H(⁴He, pα)2n four-body reaction at E_⁴He beam energy of 27.2 MeV. The relevant E* peak energy and Γ energy width spectroscopic parameters for such ⁶He* excited states decaying into the α+n+n channel were obtained by analyzing the bidimensional (E_p, E_α) energy spectra. The present new result of two low-lying ⁶He* excited states above the ⁴He+2n threshold energy of 0.974 MeV is important for the investigation of the nuclear structure of neutron-rich light nuclei and also as a basic test for theoretical models in the study of the three-cluster resonance feature of ⁶He.