Modern Physics Letters A

Gamma-ray Bursts (GRBs) are the most energetic and most relativistic phenomenon in the Universe. Understanding the nature of their progenitors is among the primary efforts of current research in high energy astrophysics, and their unmatched luminosity and other properties makes them ideal cosmological probes. This review summarizes the observational effects resulting from the interaction between the longer-wavelength radiation accompanying GRBs and their close environment. In particular, it discusses signatures that, in addition to providing powerful clues on the GRB progenitors, can also shed light on the physical characteristics, such as metallicity and dust content, of the GRB host galaxies. The last part of the article reviews the long-term signatures imprinted in the medium after a GRB explosion, particularly focusing on how we can identify GRB remnants in our own and nearby galaxies, and what we can learn from their identification.

We review the effective Lagrangian of the Higgs penguin in the Standard Model and its minimal supersymmetric extension (MSSM). As a master application of the Higgs penguin, we discuss in some detail the B-meson decays into a lepton–antilepton pair. Furthermore, we explain how this can probe the Higgs sector of the MSSM provided that some of these decays are seen at Tevatron Run II and B-factories. Finally, we present a complete list of observables where the Higgs penguin could be strongly involved.

Though a global Chern–Simons (2k-1)-form is not gauge-invariant, this form seen as a Lagrangian of higher-dimensional gauge theory leads to the conservation law of a modified Noether current.

In this paper it is shown that the gauge fixing term is not only gauge fixing term in D dimensions, but also the mass term for gauge field in (D+2)-dimensional superspace [or (D-2)-dimensional space], more importantly the kinetic term for the gauge modes g(x) is the so-called (D-2)-dimensional SU(N)×SU(N) principal chiral model. The results conform Migdal's scheme about the connection between four-dimensional gauge field and two-dimensional chiral system. And the recursion relation can be generalized to D dimensions gauge theories with chiral models in D-2 dimensions. With the new local order parameter for Yang–Mills field <g>|_D-2, the results are consistent with lattice results qualitatively: there is no phase transition in low dimensions (D≤4), while in higher dimensions first-order phase transition appears between strong coupling region and weak coupling region.

Little groups for preon branes (i.e. configurations of branes with maximal (n-1)/n fraction of survived supersymmetry) for dimensions d=2,3,…,11 are calculated for all massless, and partially for massive orbits. For massless orbits little groups are semidirect product of d-2 translational group T_d-2 on a subgroup of (SO(d-2) × R-invariance) group. E.g. at d=9 the subgroup is exceptional G₂ group. It is also argued, that 11D Majorana spinor invariants, which distinguish orbits, are actually invariant under d=2+10 Lorentz group. Possible applications of these results include construction of field theories in generalized spacetimes with brane charges coordinates, different problems of group's representations decompositions, spin-statistics issues.

We consider global properties of gravitomagnetism by investigating the gravitomagnetic field of a rotating cosmic string. We show that although the gravitomagnetic field produced by such a configuration of matter vanishes locally, it can be detected globally. In this context we discuss the gravitational analogue of the Aharonov–Bohm effect.