Algebraically special, expanding and twisting gravitational fields with vanishing Newman–Unti–Tamburino parameter

Twisting, type-N vacuum gravitational fields with symmetries.

Neutrinos with mixing in twisting magnetic fields.

Transitions in a system of neutrinos with vacuum mixing and magnetic moments, propagating in matter and transverse magnetic field, are considered. It is shown that in the realistic case of magnetic field direction varying along the neutrino path qualitatively new phenomena become possible: permutation of neutrino conversion resonances, appearance of resonances in the neutrino-antineutrino (νlL ...

Diophantine Inequalities and Quasi-algebraically Closed Fields

Consider a form g(x1, . . . , xs) of degree d, having coefficients in the completion Fq((1/t)) of the field of fractions Fq(t) associated to the finite field Fq. We establish that whenever s > d, then the form g takes arbitrarily small values for non-zero arguments x ∈ Fq[t ]. We provide related results for problems involving distribution modulo Fq[t ], and analogous conclusions for quasi-algeb...

Moose models with vanishing S parameter

In the linear moose framework, which naturally emerges in deconstruction models, we show that there is a unique solution for the vanishing of the S parameter at the lowest order in the weak interactions. We consider an effective gauge theory based on K SU(2) gauge groups, K +1 chiral fields and electroweak groups SU(2)L and U(1)Y at the ends of the chain of the moose. S vanishes when a link in ...

Expanding impulsive gravitational waves

We explicitly demonstrate that the known solutions for expanding impulsive spherical gravitational waves that have been obtained by a “cut and paste” method may be considered to be impulsive limits of the Robinson–Trautman vacuum type N solutions. We extend these results to all the generically distinct subclasses of these solutions in Minkowski, de Sitter and anti-de Sitter backgrounds. For the...