Modern Physics Letters A

This review deals with the recent resurgence of interest in adding a second scalar doublet (η⁺, η⁰) to the Standard Model of particle interactions. In most studies, it is taken for granted that η⁰ should have a nonzero vacuum expectation value, even if it may be very small. What if there is an exactly conserved symmetry which ensures 〈η⁰ 〉 = 0? The phenomenological ramifications of this idea include dark matter, radiative neutrino mass, leptogenesis, and grand unification.

We consider κ-deformed relativistic symmetries described algebraically by modified Majid–Ruegg bi-cross-product basis and investigate the quantization of field oscillators for the κ-deformed free scalar fields on κ-Minkowski space. By modification of standard multiplication rule, we postulate the κ-deformed algebra of bosonic creation and annihilation operators. Our algebra permits one to define the n-particle states with classical addition law for the four-momentum in a way which is not in contradiction with the nonsymmetric quantum four-momentum co-product. We introduce κ-deformed Fock space generated by our κ-deformed oscillators which satisfy the standard algebraic relations with modified κ-multiplication rule. We show that such a κ-deformed bosonic Fock space is endowed with the conventional bosonic symmetry properties. Finally we discuss the role of κ-deformed algebra of oscillators in field-theoretic noncommutative framework.

We discuss the phase transition between non-extremal and extremal Reissner–Nordström black holes. This transition is considered as the T → 0 limit of the transition between the non-extremal and near-extremal black holes. We show that an evaporating process from non-extremal black hole to extremal one is possible to occur, but its reverse process is not possible because of the presence of the maximum temperature. Furthermore, it is shown that the Hawking–Page phase transition between small and large black holes is unlikely to occur in the AdS Reissner–Nordström black holes.

A second rank antisymmetric tensor field is proposed as an alternative to the Higgs scalar. No mass term is allowed by the symmetries. At the scale where the asymptotically free chiral couplings of the fermions grow large, condensates of top–antitop and bottom–antibottom may induce the spontaneous breaking of the electroweak gauge symmetry. This would solve the gauge hierarchy problem by dimensional transmutation, similar to QCD.

An FRW brane model embedded in a conformally flat bulk is considered to study gravitational collapse for matter cloud in non-interacting combination of dark matter and dark energy. The form of dark energy is chosen as the decaying vacuum energy. Both expanding and contracting model of the universe are found for different time intervals with a time interval in between, which is a forbidden region.

We discuss the correspondence between the DGP brane cosmology and 5D Ricci-flat cosmology by letting their metrics equal each other. By this correspondence, a specific geometrical property of the arbitrary integral constant I in DGP metric is given and it is related to the curvature of 5D bulk. At the same time, the relation of arbitrary functions μ and ν in a class of Ricci-flat solutions is obtained from DGP brane metric.

We investigate the J^p = 1/2^- baryons in the octets based on flavor SU(3) symmetry. Since baryons with same quantum numbers can mix with each other, we consider the mixing between two octets before their mixing with the singlet. Most predicted decay widths are consistent with the experimental data, and meanwhile we predict two possible Ξ mass ranges of the two octets.