620 research outputs found
Spin dependent D-brane interactions and scattering amplitudes in matrix theory
Spin interactions beteween two moving Dp-branes are analyzed using the
Green-Schwarz formalism of boundary states. This approach turns out to be
extremely efficient to compute all the spin effects related by supersymmetry to
the leading v^4/r^7-p term. All these terms are shown to be scale invariant,
supporting a matrix model description of supergravity interactions. By
employing the LSZ reduction formula for matrix theory and the mentioned
supersymmetric effective potential for D0-branes, we compute the t-pole of
graviton-graviton and three form-three form scattering in matrix theory. The
results are found to be in complete agreement with tree level supergravity in
the corresponding kinematical regime and provide, moreover, an explicit map
between these degrees of freedom in both theories.Comment: 8 pages, no figures, talk presented at the conference "Quantum
aspects of gauge theories, supergravity and unification", Corfu, Greece, to
appear in the proceeding
Interpolating from AdS_(D-2) X S^2 to AdS_D
We investigate a large class of supersymmetric magnetic brane solutions
supported by U(1) gauge fields in AdS gauged supergravities. We obtain
first-order equations in terms of a superpotential. In particular, we find
systems which interpolate between AdS_{D-2}\times \Omega^2 (where \Omega^2=S^2
or H^2) in the horizon and AdS_D-type geometry in the asymptotic region, for
4\le D\le 7. The boundary geometry of the AdS_D-type metric is
Minkowski_{D-3}\times \Omega^2. This provides smooth supergravity solutions for
which the boundary of the AdS spacetime compactifies spontaneously. These
solutions indicate the existence of a large class of superconformal field
theories in diverse dimensions whose renormalization group flow runs from the
UV to the IR fixed point. We show that the same set of first-order equations
also admits solutions which are asymptotically AdS_{D-2}\times \Omega^2 but
singular at small distance. This implies that the stationary AdS_{D-2}\times
\Omega^2 solutions typically lie on the inflection points of the modulus space.Comment: Latex three times, 49 pages, 9 figure
Measurement schemes for the spin quadratures on an ensemble of atoms
We consider how to measure collective spin states of an atomic ensemble based
on the recent multi-pass approaches for quantum interface between light and
atoms. We find that a scheme with two passages of a light pulse through the
atomic ensemble is efficient to implement the homodyne tomography of the spin
state. Thereby, we propose to utilize optical pulses as a phase-shifter that
rotates the quadrature of the spins. This method substantially simplifies the
geometry of experimental schemes.Comment: 4pages 2 figure
Charged Higgs production from SUSY particle cascade decays at the LHC
We analyze the cascade decays of the scalar quarks and gluinos of the Minimal
Supersymmetric extension of the Standard Model, which are abundantly produced
at the Large Hadron Collider, into heavier charginos and neutralinos which then
decay into the lighter ones and charged Higgs particles, and show that they can
have substantial branching fractions. The production rates of these Higgs
bosons can be much larger than those from the direct production mechanisms, in
particular for intermediate values of the parameter , and could
therefore allow for the detection of these particles. We also discuss charged
Higgs boson production from direct two-body top and bottom squark decays as
well as from two- and three-body gluino decays.Comment: 30 pages with 10 figures, latex. Uses axodraw.sty and epsfig.st
Stretched Horizon and Entropy of Superstars
Amongst the class of supergravity solutions found by Lin, Lunin and
Maldacena, we consider pure and mixed state configurations generated by phase
space densities in the dual fermionic picture. A one-to-one map is constructed
between the phase space densities and piecewise monotonic curves, which
generalize the Young diagrams corresponding to pure states. Within the
fermionic phase space picture, a microscopic formula for the entropy of mixed
states is proposed. Considering thermal ensembles, agreement is found between
the thermodynamic and the proposed microscopic entropies. Furthermore, we study
fluctuations in thermodynamic ensembles for the superstar and compare the
entropy of these ensembles with the area of stretched horizons predicted by the
mean fluctuation size.Comment: 21 pages, 3 figures, 2 references adde
Localized modes at a D-brane--O-plane intersection and heterotic Alice strings
We study a system of -branes intersecting -branes and
-planes in 1+1-dimensions. We use anomaly cancellation and string dualities
to argue that there must be chiral fermion zero-modes on the -branes which
are localized near the -planes. Away from the orientifold limit we verify
this by using index theory as well as explicit construction of the zero-modes.
This system is related to F-theory on K3 and heterotic matrix string theory,
and the heterotic strings are related to Alice string defects in
Super-Yang-Mills. In the limit of large we find an
dual of the heterotic matrix string CFT.Comment: 44 pages, typos corrected, version published in JHE
Entropy Functions with 5D Chern-Simons terms
In this note we reconsider Sen's entropy function analysis for 5D
supergravity actions containing Chern-Simons terms. The apparent lack of gauge
invariance is usually tackled via a 4D reduction. Here we motivate how a
systematic 5D procedure also works. In doing so, it becomes important to
identify the correct 5D charges. In particular, we perform explicit
calculations for the black ring and 5D black hole. In the black ring analysis,
we find Chern-Simons induced spectral flow shifts emerging out of Sen's
formalism. We find that the entropy function nevertheless remains gauge
invariant and the resulting electric charges are identified as Page charges.
For the black hole too, 5D gauge invariance is confirmed. Our 5D analysis
enables us to fix a mismatch that arose in the electric charges of Goldstein
and Jena's 4D-reduced calculation. Finally we provide an interpretation for the
e^0 - p^0 exchange in the entropy function as an interpolation between black
hole and black ring geometries in Taub-NUT.Comment: 27 page
Non-supersymmetric Attractors in Born-Infeld Black Holes with a Cosmological Constant
We investigate the attractor mechanism for spherically symmetric extremal
black holes in Einstein-Born-Infeld-dilaton theory of gravity in
four-dimensions, in the presence of a cosmological constant. We look for
solutions analytic near the horizon by using perturbation method. It is shown
that the values of the scalar fields at the horizon are only dependent on the
charges carried by the black hole and are irrelevant in their asymptotic
values. This analysis supports the validity of non-supersymmetric attractors in
the presence of higher derivative interactions in the gauge fields part and in
non-asymptotically flat spacetime.Comment: 18 pages, no figu
On Entropy Function for Supersymmetric Black Rings
The entropy function for five-dimensional supersymmetric black rings, which
are solutions of minimal supergravity, is calculated via both
on-shell and off-shell formalism. We find that at the tree level, the entropy
function obtained from both perspectives can reproduce the Bekenstein-Hawking
entropy. We also compute the higher order corrections to the entropy arising
form five-dimensional Gauss-Bonnet term as well as supersymmetric
completion respectively and compare the results with previous microscopic
calculations.Comment: 17 pages, no figure, JHEP3 style, to appear in JHEP
One entropy function to rule them all
We study the entropy of extremal four dimensional black holes and five
dimensional black holes and black rings is a unified framework using Sen's
entropy function and dimensional reduction. The five dimensional black holes
and black rings we consider project down to either static or stationary black
holes in four dimensions. The analysis is done in the context of two derivative
gravity coupled to abelian gauge fields and neutral scalar fields. We apply
this formalism to various examples including minimal supergravity.Comment: 29 pages, 2 figures, revised version for publication, details adde
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