2,786 research outputs found
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
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
Massive Three-Dimensional Supergravity From R+R^2 Action in Six Dimensions
We obtain a three-parameter family of massive N=1 supergravities in three
dimensions from the 3-sphere reduction of an off-shell N=(1,0) six-dimensional
Poincare supergravity that includes a curvature squared invariant. The
three-dimensional theory contains an off-shell supergravity multiplet and an
on-shell scalar matter multiplet. We then generalise this in three dimensions
to an eight-parameter family of supergravities. We also find a duality
relationship between the six-dimensional theory and the N=(1,0) six-dimensional
theory obtained through a T^4 reduction of the heterotic string effective
action that includes the higher-order terms associated with the
supersymmetrisation of the anomaly-cancelling \tr(R\wedge R) term.Comment: Latex, 32 Pages, an equation is corrected, a few new equations and a
number of clarifying remarks are adde
Gauged Six-dimensional Supergravity from Massive Type IIA
We obtain the complete non-linear Kaluza-Klein ansatz for the reduction of
the bosonic sector of massive type IIA supergravity to the Romans F(4) gauged
supergravity in six dimensions. The latter arises as a consistent warped S^4
reduction.Comment: Latex, 7 page
Fibre Bundles and Generalised Dimensional Reduction
We study some geometrical and topological aspects of the generalised
dimensional reduction of supergravities in D=11 and D=10 dimensions, which give
rise to massive theories in lower dimensions. In these reductions, a global
symmetry is used in order to allow some of the fields to have a non-trivial
dependence on the compactifying coordinates. Global consistency in the internal
space imposes topological restrictions on the parameters of the
compactification as well as the structure of the space itself. Examples that we
consider include the generalised reduction of the type IIA and type IIB
theories on a circle, and also the massive ten-dimensional theory obtained by
the generalised reduction of D=11 supergravity.Comment: 23 pages, Late
Branching ratio and CP asymmetry of decays in the perturbative QCD approach
In this paper, we calculate the decay rate and CP asymmetry of the decay in perturbative QCD approach with Sudakov resummation. Since
none of the quarks in final states is the same as those of the initial
meson, this decay can occur only via annihilation diagrams in the standard
model. Besides the current-current operators, the contributions from the QCD
and electroweak penguin operators are also taken into account. We find that (a)
the branching ratio is about ; (b) the penguin diagrams
dominate the total contribution; and (c) the direct CP asymmetry is small in
size: no more than ; but the mixing-induced CP asymmetry can be as large
as ten percent testable in the near future LHC-b experiments.Comment: 12 pages, 4 figures included, RevTe
Coupled electron and phonon transport in one-dimensional atomic junctions
Employing the nonequilibrium Green's function method, we develop a fully
quantum mechanical model to study the coupled electron-phonon transport in
one-dimensional atomic junctions in the presence of a weak electron-phonon
interaction. This model enables us to study the electronic and phononic
transport on an equal footing. We derive the electrical and energy currents of
the coupled electron-phonon system and the energy exchange between them. As an
application, we study the heat dissipation in current carrying atomic junctions
within the self-consistent Born approximation, which guarantees energy current
conservation. We find that the inclusion of phonon transport is important in
determining the heat dissipation and temperature change of the atomic
junctions.Comment: 10 pages, 7 figure
f(R) Gravities, Killing Spinor Equations, "BPS" Domain Walls and Cosmology
We derive the condition on f(R) gravities that admit Killing spinor equations
and construct explicit such examples. The Killing spinor equations can be used
to reduce the fourth-order differential equations of motion to the first order
for both the domain wall and FLRW cosmological solutions. We obtain exact "BPS"
domain walls that describe the smooth Randall-Sundrum II, AdS wormholes and the
RG flow from IR to UV. We also obtain exact smooth cosmological solutions that
describe the evolution from an inflationary starting point with a larger
cosmological constant to an ever-expanding universe with a smaller cosmological
constant. In addition, We find exact smooth solutions of pre-big bang models,
bouncing or crunching universes. An important feature is that the scalar
curvature R of all these metrics is varying rather than a constant. Another
intriguing feature is that there are two different f(R) gravities that give
rise to the same "BPS" solution. We also study linearized f(R) gravities in
(A)dS vacua.Comment: 37 pages, discussion on gravity trapping in RSII modified, typos
corrected, further comments and references added; version to appear in JHE
Critical and Non-Critical Einstein-Weyl Supergravity
We construct N=1 supersymmetrisations of some recently-proposed theories of
critical gravity, conformal gravity, and extensions of critical gravity in four
dimensions. The total action consists of the sum of three separately off-shell
supersymmetric actions containing Einstein gravity, a cosmological term and the
square of the Weyl tensor. For generic choices of the coefficients for these
terms, the excitations of the resulting theory around an AdS_4 background
describe massive spin-2 and massless spin-2 modes coming from the metric;
massive spin-1 modes coming from a vector field in the theory; and massless and
massive spin-3/2 modes (with two unequal masses) coming from the gravitino.
These assemble into a massless and a massive N=1 spin-2 multiplet. In critical
supergravity, the coefficients are tuned so that the spin-2 mode in the massive
multiplet becomes massless. In the supersymmetrised extensions of critical
gravity, the coefficients are chosen so that the massive modes lie in a
"window" of lowest energies E_0 such that these ghostlike fields can be
truncated by imposing appropriate boundary conditions at infinity, thus leaving
just positive-norm massless supergravity modes.Comment: 29 page
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