31,774 research outputs found

### The Orbifolds of Permutation-Type as Physical String Systems at Multiples of $c=26$ III. The Spectra of $\hat{c}=52$ Strings

In the second paper of this series, I obtained the twisted BRST systems and
extended physical-state conditions of all twisted open and closed $\hat{c} =
52$ strings. In this paper, I supplement the extended physical-state conditions
with the explicit form of the extended (twisted) Virasoro generators of all
$\hat{c} = 52$ strings, which allows us to discuss the physical spectra of
these systems. Surprisingly, all the $\hat{c}=52$ spectra admit an equivalent
description in terms of generically-unconventional Virasoro generators at
$c=26$. This description strongly supports our prior conjecture that the
$\hat{c}=52$ strings are free of negative-norm states, and moreover shows that
the spectra of some of the simpler cases are equivalent to those of ordinary
untwisted open and closed $c=26$ strings.Comment: 23 page

### The Orbifold-String Theories of Permutation-Type: I. One Twisted BRST per Cycle per Sector

We resume our discussion of the new orbifold-string theories of
permutation-type, focusing in the present series on the algebraic formulation
of the general bosonic prototype and especially the target space-times of the
theories. In this first paper of the series, we construct one twisted BRST
system for each cycle $j$ in each twisted sector $\sigma$ of the general case,
verifying in particular the previously-conjectured algebra
$[Q_{i}(\sigma),Q_{j}(\sigma)]_{+} =0$ of the BRST charges. The BRST systems
then imply a set of extended physical-state conditions for the matter of each
cycle at cycle central charge $\hat{c}_{j}(\sigma)=26f_{j}(\sigma)$ where
$f_{j}(\sigma)$ is the length of cycle $j$.Comment: 31 page

### W3 Constructions on Affine Lie Algebras

We use an argument of Romans showing that every Virasoro construction leads
to realizations of $W_3$, to construct $W_3$ realizations on arbitrary affine
Lie algebras. Solutions are presented for generic values of the level as well
as for specific values of the level but with arbitrary parameters. We give a
detailed discussion of the \aff{su}(2)_\ell-case. Finally, we discuss
possible applications of these realizations to the construction of $W$-strings.Comment: 9 page

### On the Target-Space Geometry of Open-String Orientation-Orbifold Sectors

Including world-sheet orientation-reversing automorphisms in the orbifold
program, we recently reported the twisted operator algebra and twisted KZ
equations in each open-string sector of the general WZW orientation orbifold.
In this paper we work out the corresponding classical description of these
sectors, including the {\it WZW orientation-orbifold action} -- which is
naturally defined on the solid half cylinder -- and its associated WZW
orientation-orbifold branes. As a generalization, we also obtain the {\it
sigma-model orientation-orbifold action}, which describes a much larger class
of open-string orientation-orbifold sectors. As special cases, this class
includes twisted open-string {\it free boson} examples, the open-string WZW
sectors above and the open-string sectors of the {\it general coset orientation
orbifold}. Finally, we derive the {\it orientation- orbifold Einstein
equations}, in terms of twisted Einstein tensors -- which hold when the twisted
open-string sigma-model sectors are 1-loop conformal.Comment: 77 pages, typos correcte

### Conformal Models of Thirring Type and the Affine Virasoro Construction

We investigate a class of models in 1+1 dimensions with four fermion
interaction term. At each order of the perturbation expansion, the models are
ultraviolet finite and Lorentz non-invariant. We show that for certain
privileged values of the coupling constants, Lorentz symmetry is restored, and
indeed the model turns out to be conformally invariant. This phenomenon is both
quantum mechanical and non-perturbative.Comment: 14 pages, Latex. Some numerical errors have been correcte

### The Orbifold-String Theories of Permutation-Type: III. Lorentzian and Euclidean Space-Times in a Large Example

To illustrate the general results of the previous paper, we discuss here a
large concrete example of the orbifold-string theories of permutation-type. For
each of the many subexamples, we focus on evaluation of the \emph{target
space-time dimension} $\hat{D}_j(\sigma)$, the \emph{target space-time
signature} and the \emph{target space-time symmetry} of each cycle $j$ in each
twisted sector $\sigma$. We find in particular a gratifying \emph{space-time
symmetry enhancement} which naturally matches the space-time symmetry of each
cycle to its space-time dimension. Although the orbifolds of
$\Z_{2}$-permutation-type are naturally Lorentzian, we find that the target
space-times associated to larger permutation groups can be Lorentzian,
Euclidean and even null (\hat{D}_{j}(\sigma)=0), with varying space-time
dimensions, signature and symmetry in a single orbifold.Comment: 36 page

### Detection of an X-ray Pulsation for the Gamma-ray Pulsar Centered in CTA 1

We report the detection of X-ray pulsations with a period of ~315.87 ms from
the 2009 XMM-Newton observation for the radio-quiet gamma-ray pulsar, LAT PSR
J0007+7303, centered in the supernova remnant CTA 1. The detected pulsed period
is consistent with the gamma-ray periodicity at the same epoch found with the
Fermi Gamma-ray Space Telescope. The broader sinusoidal structure in the folded
light curve of the X-ray emission is dissimilar to that of the gamma-ray
emission, and the phase of the peak is about 0.5 shifting from the peak in the
gamma-ray bands, indicating that the main component of the X-rays originates
from different sites of the pulsar. We conclude that the main component of the
X-ray pulsation is contributed by the thermal emission from the neutron star.
Although with a significantly different characteristic age, PSR~J0007+7303 is
similar to Geminga in emission properties of X-rays and gamma-rays; this makes
PSR J0007+7303 the second radio-quiet gamma-ray pulsar with detected X-ray
pulsations after Geminga.Comment: 7 pages, 4 figures and 1 table; accepted by ApJ

### Nonsemisimple Sugawara Constructions

By a Sugawara construction we mean a generalized Virasoro construction in
which the currents are primary fields of conformal weight one. For simple Lie
algebras, this singles out the standard Sugawara construction out of all the
solutions to the Virasoro master equation. Examples of nonsemisimple Sugawara
constructions have appeared recently. They share the properties that the
Virasoro central charge is an integer equal to the dimension of the Lie algebra
and that they can be obtained by high-level contraction of reductive Sugawara
constructions: they thus correspond to free bosons. Exploiting a recent
structure theorem for Lie algebras with an invariant metric, we are able to
unify all the known constructions under the same formalism and, at the same
time, to prove several results about the Sugawara constructions. In particular,
we prove that all such constructions factorize into a standard (semisimple)
Sugawara construction and a nonsemisimple one (with integral central charge) of
a form which generalizes the nonsemisimple examples known so far.Comment: uuencoded compressed .dvi file (needs AMSFonts 2.1+), 13 document
pages but 7 physical page

### Energy Distribution of a Charged Black Hole with a Minimally Coupled Scalar Field

Using three different energy-momentum complexes, the Einstein,
Landau-Lifshitz, and Papapetrou prescriptions, we calculate the energy of an
electrically charged black hole exact solution with a self-interacting,
minimally-coupled scalar field and the asymptotic region locally an
Anti-deSitter spacetime. Writing the metric in Kerr-Schild Cartesian
coordinates, we demonstrate that this metric belongs to the Kerr-Schild class
of solutions. Applying each of the three energy-momentum prescriptions and
comparing the results, we find consistency among these complexes, suggesting
their utility as localized measures of energy.Comment: 11 pages; To appear in Astrophysics and Space Scienc

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