28 research outputs found
Schwinger type processes via branes and their gravity duals
We consider Schwinger type processes involving the creation of the charge and
monopole pairs in the external fields and propose interpretation of these
processes via corresponding brane configurations in Type IIB string theory. We
suggest simple description of some new interesting nonperturbative processes
like monopole/dyon transitions in the electric field and W-boson decay in the
magnetic field using the brane language. Nonperturbative pair production in the
strong coupling regime using the AdS/CFT correspondence is studied. The
treatment of the similar processes in the noncommutative theories when
noncommutativity is traded for the background fields is presented and the
possible role of the critical magnetic field which is S-dual to the critical
electric field is discussed.Comment: 29pp, LaTeX; v3. reference adde
Phase Diagram of Bosonic Atoms in Two-Color Superlattices
We investigate the zero temperature phase diagram of a gas of bosonic atoms
in one- and two-color standing-wave lattices in the framework of the
Bose-Hubbard model. We first introduce some relevant physical quantities;
superfluid fraction, condensate fraction, quasimomentum distribution, and
matter-wave interference pattern. We then discuss the relationships between
them on the formal level and show that the superfluid fraction, which is the
relevant order parameter for the superfluid to Mott-insulator transition,
cannot be probed directly via the matter wave interference patterns. The formal
considerations are supported by exact numerical solutions of the Bose-Hubbard
model for uniform one-dimensional systems. We then map out the phase diagram of
bosons in non-uniform lattices. The emphasis is on optical two-color
superlattices which exhibit a sinusoidal modulation of the well depth and can
be easily realized experimentally. From the study of the superfluid fraction,
the energy gap, and other quantities we identify new zero-temperature phases,
including a localized and a quasi Bose-glass phase, and discuss prospects for
their experimental observation.Comment: 18 pages, 17 figures, using REVTEX
Euler Top Dynamics of Nambu-Goto P-Branes
We propose a method to obtain new exact solutions of spinning p-branes in
flat space-times for any p, which manifest themselves as higher dimensional
Euler Tops and minimize their energy functional. We provide concrete examples
for the case of spherical topology S^{2}, S^{3} and rotational symmetry
\prod_{i}SO(q_{i}). In the case of toroidal topology T^{2}, T^{3} the
rotational symmetry is \prod SU(q_{i}) and m target dimensions are compactified
on the torus T^{m} . By double dimensional reduction the Light Cone
Hamiltonians of T^{2}, T^{3} reduce to those of closed string S^{1} and T^{2}
membranes respectively. The solutions are interpreted as non-perturbative
spinning soliton states of type IIA-IIB superstrings.Comment: 33 pages, LATEX; more typos corrected; some equation numbering
correction
On Wilson loops and -potentials from the AdS/CFT relation at
We give a short introduction to and a partial review of the work on the
calculation of Wilson loops and -potentials via the conjectured
AdS/CFT duality. Included is a discussion of the relative weight of the stringy
correction to the target space background versus the correction by the quantum
fluctuations of the string world sheet.Comment: 7 pages, one figure (eps), Latex, uses lamuphys.sty and bibnorm.sty,
based on conference talks. a reference adde