10 research outputs found
Comments on D-brane Dynamics Near NS5-Branes
We study the properties of a D-brane in the presence of NS5 branes. The
Dirac-Born-Infeld action describing the dynamics of this D-brane is very
similar to that of a non-BPS D-brane in ten dimensions. As the D-brane
approaches the fivebranes, its equation of state approaches that of a
pressureless fluid. In non-BPS D-brane case this is considered as an evidence
for the decay of the D-brane into ``tachyon matter''. We show that in our case
similar behavior is the consequence of the motion of the D-brane. In particular
in the rest frame of the moving D-brane the equation of state is that of a
usual D-brane, for which the pressure is equal to the energy density. We also
compute the total cross-section for the decay of the D-brane into closed string
modes and show that the emitted energy has a power like divergence for ,
and branes, while converges for higher dimensional D-branes. We also
speculate on the possibility that the infalling D-brane describes a decaying
defect in six dimensional Little String Theory.Comment: 18 pages, latex, references added, minor change
Spinflation from Geometric Tachyon
We study the assisted inflation scenario from the rolling of BPS D3-brane
into the NS5-branes, on a transverse geometry of , coupled to
four dimensional gravity. We assume that the branes are distributed along
and the probe D3-branes spin along plane. Qualitatively this process is
similar to that of N-tachyon assisted inflation on unstable D-branes. We
further study the spinflation scenario numerically and analyze its effect.Comment: 18pages, 9 figures, added clarifications, to appear in JHE
A Note on D-brane - Anti-D-brane Interactions in Plane Wave Backgrounds
We study aspects of the interaction between a D-brane and an anti-D-brane in
the maximally supersymmetric plane wave background of type IIB superstring
theory, which is equipped with a mass parameter mu. An early such study in flat
spacetime (mu=0) served to sharpen intuition about D-brane interactions,
showing in particular the key role of the ``stringy halo'' that surrounds a
D-brane. The halo marks the edge of the region within which tachyon
condensation occurs, opening a gateway to new non-trivial vacua of the theory.
It seems pertinent to study the fate of the halo for non--zero mu. We focus on
the simplest cases of a Lorentzian brane with p=1 and an Euclidean brane with
p=-1, the D--instanton. For the Lorentzian brane, we observe that the halo is
unaffected by the presence of non--zero mu. This most likely extends to other
(Lorentzian) p. For the Euclidean brane, we find that the halo is affected by
non-zero mu. As this is related to subtleties in defining the exchange
amplitude between Euclidean branes in the open string sector, we expect this to
extend to all Euclidean branes in this background.Comment: 14 pages, LaTeX, 2 eps figures. v2: a reference and some clarifying
remarks added; v3: Considerably revised version; halo unaffected by plane
wave background for Lorentzian branes, but Euclidean branes' halo is modifie
Intersecting D-branes in Type IIB Plane Wave Background
We study intersecting D-branes in a type IIB plane wave background using
Green-Schwarz worldsheet formulation. We consider all possible -branes
intersecting at angles in the plane wave background and identify their residual
supersymmetries. We find, in particular, that brane
intersections preserve no supersymmetry. We also present the explicit
worldsheet expressions of conserved supercharges and their supersymmetry
algebras.Comment: 32 pages, 2 tables; Corrected typos, to appear in Phys. Rev.
Supersymmetric Intersections of M-branes and pp-waves
We study supersymmetric intersections of M2 and M5 branes with different
pp-waves of M-theory. We consider first M-brane probes in the background of
pp-waves and determine under which conditions the embedding is supersymmetric.
We particularize our formalism to the case of pp-waves with 32, 24 and 20
supersymmetries. We also construct supergravity solutions for the brane-wave
system. Generically these solutions are delocalised along some directions
transverse to the brane and preserve the same number of supersymmetries as in
the brane probe approach.Comment: 41 pages, LaTeX; v2 references adde
D-branes in PP-wave light cone string field theory
The cubic interaction vertex and the dynamical supercharges are constructed
for open strings ending on D7-branes, in light-cone superstring field theory in
PP-wave background. In this context, we write down the symmetry generators in
terms of the relevant group structure: SU(2) x SU(2) x SO(2) x SO(2),
originating from the eight transverse directions in the PP-wave background and
use the expressions to explicitly construct the vertex at the level of stringy
zero modes. The results are further generalized to include all the stringy
excitations as well.Comment: 30 pages, correction in eqn. (4.28), few equations (appendix),
Comments (p.17-18) and a reference (no. 58) added, typo is corrected in eqn.
(4.5
STU/QCD Correspondence
In this review article we consider a special case of ,
supergravity called the STU model. We apply the gauge/gravity correspondence to
the STU model to gain insight into properties of the quark-gluon plasma. Given
that the quark-gluon plasma is in reality described by QCD, therefore we call
our study STU/QCD correspondence. First, we investigate the thermodynamics and
hydrodynamics of the STU background. Then we use dual picture of the theory,
which is type IIB string theory, to obtain the drag force and jet-quenching
parameter of an external probe quark.Comment: 56 pages, 20 figures. The paper is review of previous papers
arXiv:0905.1466, arXiv:1005.1368, arXiv:1011.2291 and arXiv:1011.2291.
Published versio
Aspects of urinary tract infections and antimicrobial resistance in hospitalized urology patients in Asia: 10-Year results of the Global Prevalence Study of Infections in Urology (GPIU)
10.1016/j.jiac.2017.11.013Journal of Infection and Chemotherapy244278-283JICH