542,977 research outputs found
Simplifying and Extending the AdS_5xS^5 Pure Spinor Formalism
Although the AdS_5xS^5 worldsheet action is not quadratic, some features of
the pure spinor formalism are simpler in an AdS_5xS^5 background than in a flat
background. The BRST operator acts geometrically, the left and right-moving
pure spinor ghosts can be treated as complex conjugates, the zero mode measure
factor is trivial, and the b ghost does not require non-minimal fields.
Furthermore, a topological version of the AdS_5xS^5 action with the same
worldsheet variables and BRST operator can be constructed by gauge-fixing a G/G
principal chiral model where G=PSU(2,2|4). This topological model is argued to
describe the zero radius limit that is dual to free N=4 super-Yang-Mills and
can also be interpreted as an "unbroken phase" of superstring theory.Comment: 39 pages harvma
Distilling entanglement from cascades with partial "Which Path" ambiguity
We develop a framework to calculate the density matrix of a pair of photons
emitted in a decay cascade with partial "which path" ambiguity. We describe an
appropriate entanglement distillation scheme which works also for certain
random cascades. The qualitative features of the distilled entanglement are
presented in a two dimensional "phase diagram". The theory is applied to the
quantum tomography of the decay cascade of a biexciton in a semiconductor
quantum dot. Agreement with experiment is obtained
Viscoelastic model for the dynamic structure of binary systems
This paper presents the viscoelastic model for the Ashcroft-Langreth dynamic
structure factors of liquid binary mixtures. We also provide expressions for
the Bhatia-Thornton dynamic structure factors and, within these expressions,
show how the model reproduces both the dynamic and the self-dynamic structure
factors corresponding to a one-component system in the appropriate limits
(pseudobinary system or zero concentration of one component). In particular we
analyze the behavior of the concentration-concentration dynamic structure
factor and longitudinal current, and their corresponding counterparts in the
one-component limit, namely, the self dynamic structure factor and self
longitudinal current. The results for several lithium alloys with different
ordering tendencies are compared with computer simulations data, leading to a
good qualitative agreement, and showing the natural appearance in the model of
the fast sound phenomenon.Comment: 20 pages, 19 figures, submitted to PR
Ultrashort pulses and short-pulse equations in dimensions
In this paper, we derive and study two versions of the short pulse equation
(SPE) in dimensions. Using Maxwell's equations as a starting point, and
suitable Kramers-Kronig formulas for the permittivity and permeability of the
medium, which are relevant, e.g., to left-handed metamaterials and dielectric
slab waveguides, we employ a multiple scales technique to obtain the relevant
models. General properties of the resulting -dimensional SPEs, including
fundamental conservation laws, as well as the Lagrangian and Hamiltonian
structure and numerical simulations for one- and two-dimensional initial data,
are presented. Ultrashort 1D breathers appear to be fairly robust, while rather
general two-dimensional localized initial conditions are transformed into
quasi-one-dimensional dispersing waveforms
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