681 research outputs found
The Neveu-Schwarz Five-Brane and its Dual Geometries
In this paper we discuss two aspects of duality transformations on the
Neveu-Schwarz (NS) 5-brane solutions in type II and heterotic string theories.
First we demonstrate that the non-extremal NS 5-brane background is U-dual to
its CGHS limit, a two-dimensional black hole times ; an
intermediate step is provided by the near horizon geometry which is given by
the three-dimensional black hole (being closely related to )
times . In the second part of the paper we discuss the T-duality
between NS 5-branes and the Taub-NUT spaces respectively ALE spaces, which
are related to the resolution of the singularities of the non-compact
orbifold . In particular in the framework of N=1
supersymmetric gauge theories related to brane box constructions we give the
metric dual to two sets of intersecting NS 5-branes. In this way we get a
picture of a dual orbifold background which is fibered
together out of two N=2 models (). Finally
we also discuss the intersection of NS 5-branes with D branes, which can serve
as probes of the dual background spaces.Comment: 18pp, added reference
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The Principal Branching Direction Parameter in First Language Acquisition of Anaphora
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The 3D Study: Effects of Depth, Directionality, and Distance on Children\u27s Acquisition of Anaphora: An Initial Report
Thermodynamics of Asymptotically Flat Charged Black Holes in Third Order Lovelock Gravity
We present a new class of asymptotically flat charge static solutions in
third order Lovelock gravity. These solutions present black hole solutions with
two inner and outer event horizons, extreme black holes or naked singularities
provided the parameters of the solutions are chosen suitable. We find that the
uncharged asymptotically flat solutions can present black hole with two inner
and outer horizons. This kind of solution does not exist in Einstein or
Gauss-Bonnet gravity, and it is a special effect in third order Lovelock
gravity. We compute temperature, entropy, charge, electric potential and mass
of the black hole solutions, and find that these quantities satisfy the first
law of thermodynamics. We also perform a stability analysis by computing the
determinant of Hessian matrix of the mass with respect to its thermodynamic
variables in both the canonical and the grand-canonical ensembles, and show
that there exists only an intermediate stable phase.Comment: 16 pages, two figures, a few references, and one sections added. Some
properties of these new solutions which are different from Gauss-Bonnet
gravity have been highlighte
NUT-Charged Black Holes in Gauss-Bonnet Gravity
We investigate the existence of Taub-NUT/bolt solutions in Gauss-Bonnet
gravity and obtain the general form of these solutions in dimensions. We
find that for all non-extremal NUT solutions of Einstein gravity having no
curvature singularity at , there exist NUT solutions in Gauss-Bonnet
gravity that contain these solutions in the limit that the Gauss-Bonnet
parameter goes to zero. Furthermore there are no NUT solutions in
Gauss-Bonnet gravity that yield non-extremal NUT solutions to Einstein gravity
having a curvature singularity at in the limit . Indeed,
we have non-extreme NUT solutions in dimensions with non-trivial
fibration only when the -dimensional base space is chosen to be
. We also find that the Gauss-Bonnet gravity has extremal NUT
solutions whenever the base space is a product of 2-torii with at most a
2-dimensional factor space of positive curvature. Indeed, when the base space
has at most one positively curved two dimensional space as one of its factor
spaces, then Gauss-Bonnet gravity admits extreme NUT solutions, even though
there a curvature singularity exists at . We also find that one can have
bolt solutions in Gauss-Bonnet gravity with any base space with factor spaces
of zero or positive constant curvature. The only case for which one does not
have bolt solutions is in the absence of a cosmological term with zero
curvature base space.Comment: 20 pages, referrence added, a few typos correcte
Twisted Sectors and Chern-Simons Terms in M-Theory Orbifolds
It is shown that the twisted sector spectrum, as well as the associated
Chern-Simons interactions, can be determined on M-theory orbifold fixed planes
that do not admit gravitational anomalies. This is demonstrated for the
seven-planes arising within the context of an explicit orbifold, although the results are completely general. Local
anomaly cancellation in this context is shown to require fractional anomaly
data that can only arise from a twisted sector on the seven-planes, thus
determining the twisted spectrum up to a small ambiguity. These results open
the door to the construction of arbitrary M-theory orbifolds, including those
containing fixed four-planes which are of phenomenological interest.Comment: 21 pages, LaTe
Taub-NUT/Bolt Black Holes in Gauss-Bonnet-Maxwell Gravity
We present a class of higher dimensional solutions to Gauss-Bonnet-Maxwell
equations in dimensions with a U(1) fibration over a -dimensional
base space . These solutions depend on two extra parameters, other
than the mass and the NUT charge, which are the electric charge and the
electric potential at infinity . We find that the form of metric is
sensitive to geometry of the base space, while the form of electromagnetic
field is independent of . We investigate the existence of
Taub-NUT/bolt solutions and find that in addition to the two conditions of
uncharged NUT solutions, there exist two other conditions. These two extra
conditions come from the regularity of vector potential at and the fact
that the horizon at should be the outer horizon of the black hole. We
find that for all non-extremal NUT solutions of Einstein gravity having no
curvature singularity at , there exist NUT solutions in
Gauss-Bonnet-Maxwell gravity. Indeed, we have non-extreme NUT solutions in
dimensions only when the -dimensional base space is chosen to be
. We also find that the Gauss-Bonnet-Maxwell gravity has
extremal NUT solutions whenever the base space is a product of 2-torii with at
most a 2-dimensional factor space of positive curvature, even though there a
curvature singularity exists at . We also find that one can have bolt
solutions in Gauss-Bonnet-Maxwell gravity with any base space. The only case
for which one does not have black hole solutions is in the absence of a
cosmological term with zero curvature base space.Comment: 23 pages, 3 figures, typos fixed, a few references adde
An M-Theory Perspective on Heterotic K3 Orbifold Compactifications
We analyze the structure of heterotic M-theory on K3 orbifolds by presenting
a comprehensive sequence of M-theoretic models constructed on the basis of
local anomaly cancellation. This is facilitated by extending the technology
developed in our previous papers to allow one to determine "twisted" sector
states in non-prime orbifolds. These methods should naturally generalize to
four-dimensional models, which are of potential phenomenological interest.Comment: 58 pages, LaTe
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Continuity of the Principles of Universal Grammar in First Language Acquisition: The Issue of Functional Categories
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The Syntax of CP and V-2 in Early Child German (ECG) The Strong Continuity Hypothesis
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