4,726 research outputs found
f(R) Theories of Supergravities and Pseudo-supergravities
We present f(R) theories of ten-dimensional supergravities, including the
fermionic sector up to the quadratic order in fermion fields. They are obtained
by performing the conformal scaling on the usual supergravities to the f(R)
frame in which the dilaton becomes an auxiliary field and can be integrated
out. The f(R) frame coincides with that of M-theory, D2-branes or NS-NS
5-branes. We study various BPS p-brane solutions and their near-horizon AdS
\times sphere geometries in the context of the f(R) theories. We find that new
solutions emerge with global structures that do not exist in the corresponding
solutions of the original supergravity description. In lower dimensions, We
construct the f(R) theory of N=2, D=5 gauged supergravity with a vector
multiplet, and that for the four-dimensional U(1)^4 gauged theory with three
vector fields set equal. We find that some previously-known BPS singular
"superstars" become wormholes in the f(R) theories. We also construct a large
class of f(R) (gauged) pseudo-supergravities. In addition we show that the
breathing mode in the Kaluza-Klein reduction of Gauss-Bonnet gravity on S^1 is
an auxiliary field and can be integrated out.Comment: Latex, 46 page
Multiplet Structures of BPS Solitons
There exist simple single-charge and multi-charge BPS p-brane solutions in
the D-dimensional maximal supergravities. From these, one can fill out orbits
in the charge vector space by acting with the global symmetry groups. We give a
classification of these orbits, and the associated cosets that parameterise
them.Comment: Latex, 34 pages, comments and reference adde
Consistent SO(6) Reduction Of Type IIB Supergravity on S^5
Type IIB supergravity can be consistently truncated to the metric and the
self-dual 5-form. We obtain the complete non-linear Kaluza-Klein S^5 reduction
Ansatz for this theory, giving rise to gravity coupled to the fifteen
Yang-Mills gauge fields of SO(6) and the twenty scalars of the coset
SL(6,R)/SO(6). This provides a consistent embedding of this subsector of N=8,
D=5 gauged supergravity in type IIB in D=10. We demonstrate that the
self-duality of the 5-form plays a crucial role in the consistency of the
reduction. We also discuss certain necessary conditions for a theory of gravity
and an antisymmetric tensor in an arbitrary dimension D to admit a consistent
sphere reduction, keeping all the massless fields. We find that it is only
possible for D=11, with a 4-form field, and D=10, with a 5-form. Furthermore,
in D=11 the full bosonic structure of eleven-dimensional supergravity is
required, while in D=10 the 5-form must be self-dual. It is remarkable that
just from the consistency requirement alone one would discover D=11 and type
IIB supergravities, and that D=11 is an upper bound on the dimension.Comment: Latex, 14 pages, typos corrected and comments adde
Cosmological Solutions in String Theories
We obtain a large class of cosmological solutions in the
toroidally-compactified low energy limits of string theories in dimensions.
We consider solutions where a -dimensional subset of the spatial
coordinates, parameterising a flat space, a sphere, or an hyperboloid,
describes the spatial sections of the physically-observed universe. The
equations of motion reduce to Liouville or Toda equations, which
are exactly solvable. We study some of the cases in detail, and find that under
suitable conditions they can describe four-dimensional expanding universes. We
discuss also how the solutions in dimensions behave upon oxidation back to
the string theory or M-theory.Comment: Latex, 21 pages, a reference adjuste
Interacting Intersections
Intersecting p-branes can be viewed as higher-dimensional interpretations of
multi-charge extremal p-branes, where some of the individual p-branes undergo
diagonal dimensional oxidation, while the others oxidise vertically. Although
the naive vertical oxidation of a single p-brane gives a continuum of p-branes,
a more natural description arises if one considers a periodic array of p-branes
in the higher dimension, implying a dependence on the compactification
coordinates. This still reduces to the single lower-dimensional p-brane when
viewed at distances large compared with the period. Applying the same logic to
the multi-charge solutions, we are led to consider more general classes of
intersecting p-brane solutions, again depending on the compactification
coordinates, which turn out to be described by interacting functions rather
than independent harmonic functions. These new solutions also provide a more
satisfactory interpretation for the lower-dimensional multi-charge p-branes,
which otherwise appear to be nothing more than the improbable coincidence of
charge-centres of individual constituents with zero binding energy.Comment: 20 pages, Latex, references adde
Non-zero transversity distribution of the pion in a quark-spectator-antiquark model
We calculate the non-zero (na\"{i}ve) T-odd transverse momentum dependent
transversity distribution h_1^{\perp}(x,\kp^2) of the pion in a
quark-spectator-antiquark model. The final-state interaction is modelled by the
approximation of one gluon exchange between the quark and the antiquark
spectator. Using our model result we estimate the unsuppressed cos2
azimuthal asymmetry in unpolarized Drell-Yan process. We find that the
transverse momentum dependence of h_1^{\perp}(x,\kp^2) of the pion is the
same as that of h_1^{\perp}(x,\kp^2) of the proton calculated from the
quark-scalar-diquark model, although the dependencies of them are different
from each other. This suggests a connection between cos2 asymmetries in
Drell-Yan processes with different initial hadrons.Comment: 6 LaTex Pages in Revtex format, 5 figures. Version to appear in PR
A Killing tensor for higher dimensional Kerr-AdS black holes with NUT charge
In this paper, we study the recently discovered family of higher dimensional
Kerr-AdS black holes with an extra NUT-like parameter. We show that the inverse
metric is additively separable after multiplication by a simple function. This
allows us to separate the Hamilton-Jacobi equation, showing that geodesic
motion is integrable on this background. The separation of the Hamilton-Jacobi
equation is intimately linked to the existence of an irreducible Killing
tensor, which provides an extra constant of motion. We also demonstrate that
the Klein-Gordon equation for this background is separable.Comment: LaTeX, 14 pages. v2: Typo corrected and equation added. v3: Reference
added, introduction expanded, published versio
General Kerr-NUT-AdS Metrics in All Dimensions
The Kerr-AdS metric in dimension D has cohomogeneity [D/2]; the metric
components depend on the radial coordinate r and [D/2] latitude variables \mu_i
that are subject to the constraint \sum_i \mu_i^2=1. We find a coordinate
reparameterisation in which the \mu_i variables are replaced by [D/2]-1
unconstrained coordinates y_\alpha, and having the remarkable property that the
Kerr-AdS metric becomes diagonal in the coordinate differentials dy_\alpha. The
coordinates r and y_\alpha now appear in a very symmetrical way in the metric,
leading to an immediate generalisation in which we can introduce [D/2]-1 NUT
parameters. We find that (D-5)/2 are non-trivial in odd dimensions, whilst
(D-2)/2 are non-trivial in even dimensions. This gives the most general
Kerr-NUT-AdS metric in dimensions. We find that in all dimensions D\ge4
there exist discrete symmetries that involve inverting a rotation parameter
through the AdS radius. These symmetries imply that Kerr-NUT-AdS metrics with
over-rotating parameters are equivalent to under-rotating metrics. We also
consider the BPS limit of the Kerr-NUT-AdS metrics, and thereby obtain, in odd
dimensions and after Euclideanisation, new families of Einstein-Sasaki metrics.Comment: Latex, 24 pages, minor typos correcte
Killing Spinors for the Bosonic String
We obtain the effective action for the bosonic string with arbitrary
Yang-Mills fields, up to the \alpha' order, in general dimensions. The form of
the action is determined by the requirement that the action admit well-defined
Killing spinor equations, whose projected integrability conditions give rise to
the full set of equations of motion. The success of the construction suggests
that the hidden "pseudo-supersymmetry" associated with the Killing spinor
equations may be a property of the bosonic string itself.Comment: 9 page
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