100 research outputs found

### On realizing the bosonic string as a noncritical W3-string

We discuss a realization of the bosonic string as a noncritical $W_3$-string.
The relevant noncritical $W_3$-string is characterized by a Liouville sector
which is restricted to a (non-unitary) $(3,2)$ $W_3$ minimal model with central
charge contribution $c_l = - 2$. Furthermore, the matter sector of this
$W_3$-string contains $26$ free scalars which realize a critical bosonic
string. The BRST operator for this $W_3$-string can be written as the sum of
two, mutually anticommuting, nilpotent BRST operators: $Q = Q_0 + Q_1$ in such
a way that the scalars which realize the bosonic string appear only in $Q_0$
while the central charge contribution of the fields present in $Q_1$ equals
zero. We argue that, in the simplest case that the Liouville sector is given by
the identity operator only, the $Q_1$-cohomology is given by a particular
(non-unitary) $(3,2)$ Virasoro minimal model at $c=0$.Comment: 12 pages, UG-7/9

### Generalized Conformal Quantum Mechanics of D0-brane

We study the generalized conformal quantum mechanics of the probe D0-brane in
the near horizon background of the bound state of source D0-branes. We
elaborate on the relationship of such model to the M theory in the light cone
frame.Comment: 14 pages, RevTeX, revised version with added references to appear in
Phys. Rev.

### The holographic RG flow in a field theory on a curved background

As shown by Freedman, Gubser, Pilch and Warner, the RG flow in ${\cal N}=4$
super-Yang-Mills theory broken to an ${\cal N}=1$ theory by the addition of a
mass term can be described in terms of a supersymmetric domain wall solution in
five-dimensional ${\cal N}=8$ gauged supergravity. The FGPW flow is an example
of a holographic RG flow in a field theory on a flat background. Here we put
the field theory studied by Freedman, Gubser, Pilch and Warner on a curved
$AdS_4$ background, and we construct the supersymmetric domain wall solution
which describes the RG flow in this field theory. This solution is a curved
(non Ricci flat) domain wall solution. This example demonstrates that
holographic RG flows in supersymmetric field theories on a curved $AdS_4$
background can be described in terms of curved supersymmetric domain wall
solutions.Comment: 14 pages, LaTe

### Comment on Counting Black Hole Microstates Using String Dualities

We discuss a previous attempt at a microscopic counting of the entropy of
asymptotically flat non-extremal black-holes. This method used string dualities
to relate 4 and 5 dimensional black holes to the BTZ black hole. We show how
the dualities can be justified in a certain limit, equivalent to a near horizon
limit, but the resulting spacetime is no longer asymptotically flat.Comment: 10 pages, harvmac. v(2) typo correcte

### Hydrodynamics from the Dp-brane

We complete the computation of viscous transport coefficients in the near
horizon geometries that arise from a stack of black Dp-branes for p=2,...,6 in
the decoupling limit. The main new result is the obtention of the bulk
viscosity which, for all p, is found to be related to the speed of sound by the
simple relation \zeta/\eta = -2(v_s^2-1/p). For completeness the shear
viscosity is rederived from gravitational perturbations in the shear and scalar
channels. We comment on technical issues like the counterterms needed, or the
possible dependence on the conformal frame.Comment: 15 page

### Scalar fields, bent branes, and RG flow

This work deals with braneworld scenarios driven by real scalar fields with
standard dynamics. We show how the first-order formalism which exists in the
case of four dimensional Minkowski space-time can be extended to de Sitter or
anti-de Sitter geometry in the presence of several real scalar fields. We
illustrate the results with some examples, and we take advantage of our
findings to investigate renormalization group flow. We have found symmetric
brane solutions with four-dimensional anti-de Sitter geometry whose
holographically dual field theory exhibits a weakly coupled regime at high
energy.Comment: 22 pages, 7 figure

### Non-extremal D-instantons

We construct the most general non-extremal deformation of the D-instanton
solution with maximal rotational symmetry. The general non-supersymmetric
solution carries electric charges of the SL(2,R) symmetry, which correspond to
each of the three conjugacy classes of SL(2,R). Our calculations naturally
generalise to arbitrary dimensions and arbitrary dilaton couplings.
We show that for specific values of the dilaton coupling parameter, the
non-extremal instanton solutions can be viewed as wormholes of non-extremal
Reissner-Nordstr\"om black holes in one higher dimension. We extend this result
by showing that for other values of the dilaton coupling parameter, the
non-extremal instanton solutions can be uplifted to non-extremal non-dilatonic
p-branes in p+1 dimensions higher.
Finally, we attempt to consider the solutions as instantons of (compactified)
type IIB superstring theory. In particular, we derive an elegant formula for
the instanton action. We conjecture that the non-extremal D-instantons can
contribute to the R^8-terms in the type IIB string effective action.Comment: 31 pages, 4 figures. v3: minor correction and reference adde

### Duality symmetry in four-dimensional string actions

We reduce the dual version of $D=10$, $N=1$ supergravity coupled to $n$
vector fields to four dimensions, and derive the $SL(2,R)\times O(6,6+n)$
transformations which leave the equations of motion invariant. For $n=0$
$SL(2,R)$ is also a symmetry of the action, but for $n>0$ only those $SL(2,R)$
transformations which act linearly on all fields leave the action invariant.
The resulting four-dimensional theory is related to the bosonic part of the
usual formulation of $N=4$ supergravity coupled to matter by a duality
transformation.Comment: 9 pages, Latex fil

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