29 research outputs found
Supertwistors as Quarks of SU(2,2|4)
The GS superstring on AdS_5 x S^5 has a nonlinearly realized, spontaneously
broken SU(2,2|4) symmetry. Here we introduce a two-dimensional model in which
the unbroken SU(2,2|4) symmetry is linearly realized. The basic variables are
supertwistors, which transform in the fundamental representation of this
supergroup.
The quantization of this supertwistor model leads to the complete oscillator
construction of the unitary irreducible representations of the centrally
extended SU(2,2|4). They include the states of d=4 SYM theory, massless and KK
states of AdS_5 supergravity, and the descendants on AdS_5 of the standard
massive string states, which form intermediate and long supermultiplets. We
present examples of such multiplets and discuss possible states of solitonic
and (p,q) strings.Comment: 12 pages, LaTeX, 1 EPS figur
Quantization of Superstrings in Ramond-Ramond Backgrounds
We present a perturbative study of Ramond-Ramond backgrounds in the NSR
formalism. We show how to perform sigma-model computations and discuss in
detail the structure of the BRST charge and picture-changing operators. Contact
terms play a vital role in the analysis. We also give evidence for a two loop
non-renormalization theorem for the background beta functions.Comment: 29 pages, 1 figure; uses LaTeX, epsf, hyperref packages; references
adde
AdS and pp-wave D-particle superalgebras
We derive anticommutators of supercharges with a brane charge for a
D-particle in AdS(2) x S(2) and pp-wave backgrounds. A coset GL(2|2)/(GL(1))^4
and its Penrose limit are used with the supermatrix-valued coordinates for the
AdS and the pp-wave spaces respectively. The brane charges have position
dependence, and can be absorbed into bosonic generators by shift of momenta
which results in closure of the superalgebras.Comment: 15 page
Dimensional reduction of 4d heterotic string black holes
We perform the spherical symmetric dimensional reduction of
heterotic string theory. We find a class of two-dimensional (2d) dilaton
gravity models that gives a general description of the near-horizon,
near-extremal behavior of four-dimensional (4d) heterotic string black holes.
We show that the duality group of the 4d theory is realized in two dimensions
in terms of Weyl transformations of the metric. We use the 2d dilaton gravity
theory to compute the statistical entropy of the near-extremal 4d,
, black hole.Comment: 12 pages, LaTex fil
Maximal Temperature in Flux Compactifications
Thermal corrections have an important effect on moduli stabilization leading
to the existence of a maximal temperature, beyond which the compact dimensions
decompactify. In this note, we discuss generality of our earlier analysis and
apply it to the case of flux compactifications. The maximal temperature is
again found to be controlled by the supersymmetry breaking scale, T_{crit} \sim
\sqrt{m_{3/2} M_P}.Comment: 10 pages, 10 figures. v2:comment and references adde
Nondegenerate Super-Anti-de Sitter Algebra and a Superstring Action
We construct an Anti-de Sitter(AdS) algebra in a nondegenerate superspace.
Based on this algebra we construct a covariant kappa-symmetric superstring
action, and we examine its dynamics: Although this action reduces to the usual
Green-Schwarz superstring action in flat limit, the auxiliary fermionic
coordinates of the nondegenerate superspace becomes dynamical in the AdS
background.Comment: Latex, 12 pages, explanations added, version to be published in Phys.
Rev.
Strings on Semisymmetric Superspaces
Several string backgrounds which arise in the AdS/CFT correspondence are
described by integrable sigma-models. Their target space is always a Z(4)
supercoset (a semi-symmetric superspace). Here we list all semi-symmetric
cosets which have zero beta function and central charge c<=26 at one loop in
perturbation theory.Comment: 25 pages, 1 figur
Accidental Inflation in String Theory
We show that inflation in type IIB string theory driven by the volume modulus
can be realized in the context of the racetrack-based Kallosh-Linde model (KL)
of moduli stabilization. Inflation here arises through the volume modulus
slow-rolling down from a flat hill-top or inflection point of the scalar
potential. This situation can be quite generic in the landscape, where by
uplifting one of the two adjacent minima one can turn the barrier either to a
flat saddle point or to an inflection point supporting eternal inflation. The
resulting spectral index is tunable in the range of 0.93 < n_s < 1, and there
is only negligible production of primordial gravitational waves r < 10^{-6}.
The flatness of the potential in this scenario requires fine-tuning, which may
be justified taking into account the exponential reward by volume factors
preferring the regions of the universe with the maximal amount of slow-roll
inflation. This consideration leads to a tentative prediction of the spectral
index or depending on whether the
potential has a symmetry phi -> - phi or not.Comment: 15 pages, 6 figures, LaTeX, uses RevTex
Four Dimensional Conformal Supergravity From AdS Space
Exploring the role of conformal theories of gravity in string theory, we show
that the minimal (N=2) gauged supergravities in five dimensions induce the
multiplets and transformations of N=1 four dimensional conformal supergravity
on the spacetime boundary. N=1 Poincare supergravity can be induced by
explicitly breaking the conformal invariance via a radial cutoff in the 5d
space. The AdS/CFT correspondence relates the maximal gauged supergravity in
five dimensions to N=4 super Yang-Mills on the 4d spacetime boundary. In this
context we show that the conformal anomaly of the gauge theory induces
conformal gravity on the boundary of the space and that this theory, via the
renormalization group, encapsulates the gravitational dynamics of the skin of
asymptotically AdS spacetimes. Our results have several applications to the
AdS/CFT correspondence and the Randall-Sundrum scenario.Comment: 20 pages, LaTeX. v3. references and minor comments adde
Matrix Norms, BPS Bounds and Marginal Stability in N=8 Supergravity
We study the conditions of marginal stability for two-center extremal black
holes in N-extended supergravity in four dimensions, with particular emphasis
on the N=8 case. This is achieved by exploiting triangle inequalities satisfied
by matrix norms. Using different norms and relative bounds among them, we
establish the existence of marginal stability and split attractor flows both
for BPS and some non-BPS solutions. Our results are in agreement with previous
analysis based on explicit construction of multi-center solutions.Comment: 1+15 pages; v2: some new formulas added and misprints corrected; v3:
typos fixed, various refinements, Sec. 2.4 rewritten; to appear on JHE