In this paper we present semiclassical computations of the splitting of folded spinning strings in AdS_3, which may be of interest in the context of AdS/CFT duality. We start with a classical closed string and assume that it can split on two closed s
tring fragments, if at a given time two points on it coincide in target space and their velocities agree. First we consider the case of the folded string with large spin. Assuming the formal large-spin approximation of the folded string solution in AdS_3, we can completely describe the process of splitting: compute the full set of charges and obtain the string solutions describing the evolution of the final states. We find that, in this limit, the world surface does not change in the process and the final states are described by the solutions of the same type as the initial string, i.e. the formal large-spin approximation of the folded string in AdS_3. Then we consider the general case --- splitting of string given by the exact folded string solution. We find the expressions for the charges of the final fragments, the coordinate transformations diagonalizing them and, finally, their energies and spins. Due to the complexity of the initial string profile, we cannot find the solutions describing the evolution of the final fragments, but we can predict their qualitative behavior. We also generalize the results to include circular rotations and windings in S^5.
We discuss some new simple closed bosonic string solutions in AdS_5 x S^5 that may be of interest in the context of AdS/CFT duality. In the first part of this work we consider solutions with two spins (S_1, S_2) in AdS_5. Starting from the flat-space
solutions and using perturbation theory in the curvature of AdS_5 space, we construct leading terms in the small two-spin solution. We find corrections to the leading Regge term in the classical string energy and uncover a discontinuity in the spectrum for certain type of a solution. We then analyze the connection between small-spin and large-spin limits of string solutions in AdS_5. We show that the S_1 = S_2 solution in AdS_5 found in earlier papers admits both limits only in simplest cases of the folded and rigid circular strings. In the second part of the paper we construct a new class of chiral solutions in R_t x S^5 for which embedding coordinates of S^5 satisfy the linear Laplace equations. They generalize the previously studied rigid string solutions. We study in detail a simple nontrivial example.
Recently there has been a renewed interest in axionic generalization of electrodynamics due to its application to topological insulators. A low-energy electromagnetic response of these exotic materials was proposed to be described by an axionic term
in the Lagrangian. Motivated by this it is of interest to study various aspects of axionic electrodynamics and analyze the universal features of the axionic effects. Here we discuss the axionic modification of generalized electrodynamics with a Lagrangian being an arbitrary function of two electromagnetic invariants. Surprisingly, the qualitative characteristics of the major axionic effects known in the Maxwell theory happen to be independent of the exact type of the nonlinear Lagrangian and are uniquely fixed by the form of the axionic term.
The problem of neutrino spin rotation in dense matter and in strong electromagnetic fields is solved in accordance with the basic principles of quantum mechanics. We obtain a complete system of wave functions for a massive Dirac neutrino with an anom
alous magnetic moment which are the eigenfunctions of the kinetic momentum operator and have the form of nonspreading wave packets. These wave functions enable one to consider the states of neutrino with rotating spin as pure quantum states and can be used for calculating probabilities of various processes with the neutrino in the framework of the Furry picture.
