825 research outputs found
Conformal Field Theory for the Superstring in a Ramond-Ramond Plane Wave Background
A quantizable worldsheet action is constructed for the superstring in a
supersymmetric plane wave background with Ramond-Ramond flux. The action is
manifestly invariant under all isometries of the background and is an exact
worldsheet conformal field theory.Comment: 13 pages harvma
Interacting Strings in Matrix String Theory
It is here explained how the Green-Schwarz superstring theory arises from
Matrix String Theory. This is obtained as the strong YM-coupling limit of the
theory expanded around its BPS instantonic configurations, via the
identification of the interacting string diagram with the spectral curve of the
relevant configuration. Both the GS action and the perturbative weight
, where is the Euler characteristic of the world-sheet
surface and the string coupling, are obtained.Comment: 11 pages, no figures, two references adde
Light-cone Gauge NSR Strings in Noncritical Dimensions
Light-cone gauge NSR string theory in noncritical dimensions should
correspond to a string theory with a nonstandard longitudinal part.
Supersymmetrizing the bosonic case [arXiv:0909.4675], we formulate a
superconformal worldsheet theory for the longitudinal variables X^{\pm},
\psi^{\pm}. We show that with the transverse variables and the ghosts combined,
it is possible to construct a nilpotent BRST charge.Comment: 22 pages, 1 figur
Comparison of quantum field perturbation theory for the light front with the theory in lorentz coordinates
The relationship between the perturbation theory in light-front coordinates
and Lorentz-covariant perturbation theory is investigated. A method for finding
the difference between separate terms of the corresponding series without their
explicit evaluation is proposed. A procedure of constructing additional
counter-terms to the canonical Hamiltonian that compensate this difference at
any finite order is proposed. For the Yukawa model, the light-front Hamiltonian
with all of these counter-terms is obtained in a closed form. Possible
application of this approach to gauge theories is discussed.Comment: LaTex 2.09, 20 pages, 5 figure
Electrons as quasi-bosons in magnetic white dwarfs
A white dwarf star achieves its equilibrium from the balancing of the
gravitational compression against the Fermi degeneracy pressure of the electron
gas. In field theory there are examples (e.g. the monopole-charge system) where
a strong magnetic field can transform a boson into a fermion or a fermion into
a boson. In some condensed matter systems (e.g. fractional quantum Hall
systems) a strong magnetic field can transform electrons into effective
fermions, or effective anyons. Based on these examples we investigate the
possibility that the strong magnetic fields of some white dwarfs may transform
some fraction of the electrons into effective bosons. This could have
consequences for the structure of highly magnetized white dwarfs. It would
alter the mass-radius relationship, and in certain instances one could envision
a scenario where a white dwarf below the Chandrasekhar limit could nevertheless
collapse into a neutron star due to a weakening of the electron degeneracy
pressure. In addition the transformation of electrons into effective bosons
could result in the electrons Bose condensing, which could speed up the cooling
rate of white dwarfs.Comment: 10 pages. To be published IJMP
Shear and bulk viscosities for pure glue matter
Shear and bulk viscosities are calculated in a quasiparticle
model within a relaxation time approximation for pure gluon matter. Below
the confined sector is described within a quasiparticle glueball model.
Particular attention is paid to behavior of the shear and bulk viscosities near
. The constructed equation of state reproduces the first-order phase
transition for the glue matter. It is shown that with this equation of state it
is possible to describe the temperature dependence of the shear viscosity to
entropy ratio and the bulk viscosity to entropy ratio in
reasonable agreement with available lattice data but absolute values of the
ratio underestimate the upper limits of this ratio in the lattice
measurements typically by an order of magnitude.Comment: 8 pages, 4 figures; the published versio
Factorization effects in a model of unstable particles
The effects of factorization are considered within the framework of the model
of unstable particles with a smeared mass. It is shown that two-particle cross
section and three-particle decay width can be described by the universal
factorized formulae for an unstable particles of an arbitrary spin in an
intermediate state. The exact factorization is caused by the specific structure
of the model unstable-particle propagators. This result is generalized to
complicated scattering and decay-chain processes with unstable particles in
intermediate states. We analyze applicability of the method and evaluate its
accuracy.Comment: 13 pages, 7 figure
Light-cone Gauge NSR Strings in Noncritical Dimensions II -- Ramond Sector
Light-cone gauge superstring theory in noncritical dimensions corresponds to
a worldsheet theory with nonstandard longitudinal part in the conformal gauge.
The longitudinal part of the worldsheet theory is a superconformal field theory
called X^{\pm} CFT. We show that the X^{\pm} CFT combined with the
super-reparametrization ghost system can be described by free variables. It is
possible to express the correlation functions in terms of these free variables.
Bosonizing the free variables, we construct the spin fields and BRST invariant
vertex operators for the Ramond sector in the conformal gauge formulation. By
using these vertex operators, we can rewrite the tree amplitudes of the
noncritical light-cone gauge string field theory, with external lines in the
(R,R) sector as well as those in the (NS,NS) sector, in a BRST invariant way.Comment: 33 pages; v2: minor modification
Analytic Approach to Perturbative QCD
The two-loop invariant (running) coupling of QCD is written in terms of the
Lambert W function. The analyticity structure of the coupling in the complex
Q^2-plane is established. The corresponding analytic coupling is reconstructed
via a dispersion relation. We also consider some other approximations to the
QCD beta-function, when the corresponding couplings are solved in terms of the
Lambert function. The Landau gauge gluon propagator has been considered in the
renormalization group invariant analytic approach (IAA). It is shown that there
is a nonperturbative ambiguity in determination of the anomalous dimension
function of the gluon field. Several analytic solutions for the propagator at
the one-loop order are constructed. Properties of the obtained analytical
solutions are discussed.Comment: Latex-file, 19 pages, 2 tables, 51 references, to be published in
Int. J. Mod. Phys.
Fleming's bound for the decay of mixed states
Fleming's inequality is generalized to the decay function of mixed states. We
show that for any symmetric hamiltonian and for any density operator
on a finite dimensional Hilbert space with the orthogonal projection onto
the range of there holds the estimate \Tr(\Pi \rme^{-\rmi ht}\rho
\rme^{\rmi ht}) \geq\cos^{2}((\Delta h)_{\rho}t) for all real with
We show that equality either holds for all
or it does not hold for a single with All the density operators saturating the bound for
all i.e. the mixed intelligent states, are determined.Comment: 12 page
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