272 research outputs found
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
Revisiting the proposed planetary system orbiting the eclipsing polar HU Aquarii
It has recently been proposed, on the basis of eclipse-timing data, that the
eclipsing polar cataclysmic variable HU Aquarii is host to at least two giant
planets. However, that result has been called into question based upon the
dynamical stability of the proposed planets. In this work, we present a
detailed re-analysis of all eclipse timing data available for the HU Aquarii
system, making use of standard techniques used to fit orbits to radial-velocity
data. We find that the eclipse timings can be used to obtain a two-planet
solution that does not require the presence of additional bodies within the
system. We then perform a highly detailed dynamical analysis of the proposed
planetary system. We show that the improved orbital parameters we have derived
correspond to planets that are dynamically unstable on unfeasibly short
timescales (of order 10^4 years or less). Given these results, we discuss
briefly how the observed signal might in fact be the result of the intrinsic
properties of the eclipsing polar, rather than being evidence of dynamically
improbable planets. Taken in concert, our results highlight the need for
caution in interpreting such timing variations as being planetary in nature.Comment: Accepted for publication in MNRA
N = 3 chiral supergravity compatible with the reality condition and higher N chiral Lagrangian density
We obtain N = 3 chiral supergravity (SUGRA) compatible with the reality
condition by applying the prescription of constructing the chiral Lagrangian
density from the usual SUGRA. The chiral Lagrangian density in
first-order form, which leads to the Ashtekar's canonical formulation, is
determined so that it reproduces the second-order Lagrangian density of the
usual SUGRA especially by adding appropriate four-fermion contact terms. We
show that the four-fermion contact terms added in the first-order chiral
Lagrangian density are the non-minimal terms required from the invariance under
first-order supersymmetry transformations. We also discuss the case of higher N
theories, especially for N = 4 and N = 8.Comment: 20 pages, Latex, some more discussions and new references added, some
typos corrected, accepted for publication in Physical Review
Anti-self-dual Maxwell solutions on hyperk\"ahler manifold and N=2 supersymmetric Ashtekar gravity
Anti-self-dual (ASD) Maxwell solutions on 4-dimensional hyperk\"ahler
manifolds are constructed. The N=2 supersymmetric half-flat equations are
derived in the context of the Ashtekar formulation of N=2 supergravity. These
equations show that the ASD Maxwell solutions have a direct connection with the
solutions of the reduced N=2 supersymmetric ASD Yang-Mills equations with a
special choice of gauge group. Two examples of the Maxwell solutions are
presented.Comment: 9 page
Noncommutative Topological Half-flat Gravity
We formulate a noncommutative description of topological half-flat gravity in
four dimensions. BRST symmetry of this topological gravity is deformed through
a twisting of the usual BRST quantization of noncommutative gauge theories.
Finally it is argued that resulting moduli space of instantons is characterized
by the solutions of a noncommutative version of the Plebanski's heavenly
equation.Comment: 12+1 pages, revtex4, no figure
Holographic Formulation of Quantum Supergravity
We show that supergravity with a cosmological constant can be
expressed as constrained topological field theory based on the supergroup
. The theory is then extended to include timelike boundaries with
finite spatial area. Consistent boundary conditions are found which induce a
boundary theory based on a supersymmetric Chern-Simons theory. The boundary
state space is constructed from states of the boundary supersymmetric
Chern-Simons theory on the punctured two sphere and naturally satisfies the
Bekenstein bound, where area is measured by the area operator of quantum
supergravity.Comment: 30 pages, no figur
Integrability of Type II Superstrings on Ramond-Ramond Backgrounds in Various Dimensions
We consider type II superstrings on AdS backgrounds with Ramond-Ramond flux
in various dimensions. We realize the backgrounds as supercosets and analyze
explicitly two classes of models: non-critical superstrings on AdS_{2d} and
critical superstrings on AdS_p\times S^p\times CY. We work both in the
Green--Schwarz and in the pure spinor formalisms. We construct a one-parameter
family of flat currents (a Lax connection) leading to an infinite number of
conserved non-local charges, which imply the classical integrability of both
sigma-models. In the pure spinor formulation, we use the BRST symmetry to prove
the quantum integrability of the sigma-model. We discuss how classical
\kappa-symmetry implies one-loop conformal invariance. We consider the addition
of space-filling D-branes to the pure spinor formalism.Comment: LaTeX2e, 56 pages, 1 figure, JHEP style; v2: references added, typos
fixed in some equations; v3: typos fixed to match the published versio
BRST Analysis of Physical States in Two-Dimensional Black Hole
We study the BRST cohomology for coset model, which describes
an exact string black hole solution. It is shown that the physical spectrum
could contain not only the extra discrete states corresponding to those in
two-dimensional gravity but also many additional new states with ghost
number . We also discuss characters for nonunitary
representations and the relation of our results to other approaches.Comment: 44 pages, OS-GE 28-93, OU-HET 17
Diagnosing FUor-like Sources: The Parameter Space of Viscously Heated Disks in the Optical and Near-IR
FU Ori type objects (FUors) are decades-long outbursts of accretion onto
young stars that are strong enough to viscously heat disks so that the disk
outshines the central star. We construct models for FUor objects by calculating
emission components from a steady-state viscous accretion disk, a
passively-heated dusty disk, magnetospheric accretion columns, and the stellar
photosphere. We explore the parameter space of the accretion rate and stellar
mass to investigate implications on the optical and near-infrared spectral
energy distribution and spectral lines. The models are validated by fitting to
multi-wavelength photometry of three confirmed FUor objects, FU Ori, V883 Ori
and HBC 722 and then comparing the predicted spectrum to observed optical and
infrared spectra. The brightness ratio between the viscous disk and the stellar
photosphere, , provides an important guide for identifying viscous
accretion disks, with ("transition line") and ("sufficient
dominance line") marking turning points in diagnostics, evaluated here in the
near-infrared. These turning points indicate the emergence and complete
development of FUor-characteristic strong CO absorption, weak metallic
absorption, the triangular spectral continuum shape in the -band, and
location in color-magnitude diagrams. Lower stellar mass and higher
accretion rate lead to larger ; for ,
corresponds to yr and
to yr. The sufficient dominance line
also coincides with the expected accretion rate where accreting material
directly reaches the star. We discuss implications of the models on extinction
diagnostics, FUor brightening timescales, viscous disks during initial
protostellar growth, and eruptive young stellar objects (YSO) associated with
FUors.Comment: 32 pages, 23 figures, accepted for publication in Ap
A candidate for a background independent formulation of M theory
A class of background independent membrane field theories are studied, and
several properties are discovered which suggest that they may play a role in a
background independent form of M theory. The bulk kinematics of these theories
are described in terms of the conformal blocks of an algebra G on all oriented,
finite genus, two-surfaces. The bulk dynamics is described in terms of causal
histories in which time evolution is specified by giving amplitudes to certain
local changes of the states. Holographic observables are defined which live in
finite dimensional states spaces associated with boundaries in spacetime. We
show here that the natural observables in these boundary state spaces are, when
G is chosen to be Spin(D) or a supersymmetric extension of it, generalizations
of matrix model coordinates in D dimensions. In certain cases the bulk dynamics
can be chosen so the matrix model dynamics is recoverd for the boundary
observables. The bosonic and supersymmetric cases in D=3 and D=9 are studied,
and it is shown that the latter is, in a certain limit, related to the matrix
model formulation of M theory. This correspondence gives rise to a conjecture
concerning a background independent form of M theory in terms of which
excitations of the background independent membrane field theory that correspond
to strings and D0 branes are identified.Comment: Latex 46 pages, 21 figures, new results included which lead to a
modification of the statement of the basic conjecture. Presentation improve
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