Modern Physics Letters A

The possible existence of neutrinos with a mass of 17 keV would have profound consequences for particle physics, astrophysics, and cosmology. Although several recent investigations have found evidence that about 1% of neutrinos have a 17 keV mass, other investigations have given negative results. In this review we summarize the evidence both for, and against, the existence of such a neutrino.

The propagation of neutrinos in a strong gravitational field is determined within the WKB approximation. The result is used to study the modifications induced by gravity on the standard picture of neutrino oscillations. It is seen that, for sufficiently strong fields, the gravitationally induced left–right transitions are important, and will significantly modify the persistence probability for a neutrino to retain its original flavor and helicity. The inclusion of electromagnetic interactions is also briefly considered.

We discuss the quantum black holes and even more generally the problem of quantum horizons in string theory. A toy model for quantum horizon is the two-dimensional O(3) σ-model. Using the interpretation of time as zero mode of conformal factor of world-sheet metric (Liouville field) the possible equivalence between two-dimensional renormalization group equations and Hawking quantum evaporation formula is found. The infrared fixed points of two-dimensional renormalization group corresponds to final state of the quantum black hole. Using conjecture that such a fixed points are described by σ-models with θ=π we suggest the axionic black holes as possible candidates to final (meta)stable states of black holes. The corresponding renormalization group picture are similar to the quantum Hall effect.

1024 interactions caused by 4.5 A GeV/c ²⁸Si in emulsion are studied. Result on the mean free path is discussed and compared with the corresponding results obtained for the interactions initiated by other projectiles. Multiplicity distributions for Z=1,2 and fragments are also investigated.

This letter provides a simple reformulation of the standard electroweak theory of leptons with two generations as a generalized gauge theory. It is based on a discrete analogue of Kaluza–Klein theories, with the 'extra dimension' being the generations of the matter. Higgs fields appear as part of a generalized gauge field. Hypercharge quantization results from the use of a simple Lie superalgebra su(1|2) as the generalized gauge algebra.

By using the BRST invariance, we find the stochastic gauge-fixing function which corresponds to the ordinary gauge-fixing function for non-Abelian antisymmetric tensor fields as reducible gauge theories. Then the trial stochastic gauge-fixing function is obtained perturbatively.

We present a geometric interpretation for the torsion constraints in (2,0) supergravity using G-structures. This leads to a classification of the constraints as given by Ref. 1. We also present the essential torsion constraints for (p,q) geometry.

We show the existence of higher order conserved quantities of isospin 1 (with spin 0,2,4,6,…) and isospin 0,2 (with spin 1,3,5,7,…) for the k=2 SU(2) WZW theory perturbed by the singlet combination of the isospin 1 primary field. We also show the possible existence of conserved isospin 0 current with spin 3 in the k→∞ limit. We also analyze these theories for finite k(≥3) and show that at least by counting arguments there exist no higher conserved quantities in these cases.

We examine a model for massive vector mesons in four dimensions proposed by Freedman and Townsend, where the masses for non-Abelian vector gauge fields are generated without symmetry breaking through a gauge invariant coupling to anti-symmetric tensor fields. The model is quantized using the formalism of Batalin and Vilkovisky. While the Abelian version immediately gives a renormalizable model for massive vector fields, it is shown that in the non-Abelian case the addition of an extra gauge invariant term in the initial Lagrangian leads to an ultraviolet behavior consistent with power-counting renormalizability.

Graviton-dilaton background field equations in three space-time dimensions, following from the string effective action are solved when the metric has only time dependence. By taking one of the two space dimensions as compact, our solution reproduces a recently discovered charged black hole solution in two space-time dimensions. Solutions in the presence of non-vanishing three-dimensional background antisymmetric tensor field are also discussed.