51 research outputs found
N=3 Warped Compactifications
Orientifolds with three-form flux provide some of the simplest string
examples of warped compactification. In this paper we show that some models of
this type have the unusual feature of D=4, N=3 spacetime supersymmetry. We
discuss their construction and low energy physics. Although the local form of
the moduli space is fully determined by supersymmetry, to find its global form
requires a careful study of the BPS spectrum.Comment: 27 pages, v2: 32pp., RevTeX4, fixed factors, slightly improved
sections 3D and 4B, v3: added referenc
Schwinger model on a half-line
We study the Schwinger model on a half-line in this paper. In particular, we
investigate the behavior of the chiral condensate near the edge of the line.
The effect of the chosen boundary condition is emphasized. The extension to the
finite temperature case is straightforward in our approach.Comment: 4 pages, no figure. Final version to be published on Phys. Rev.
A class of non-supersymmetric orientifolds
We study type IIB orientifolds on T^{2d}/Z_N with supersymmetry broken by the
compactification. We determine tadpole cancellation conditions including
anti-branes and considering different actions for the parity Omega. Using these
conditions we then obtain the spectrum of tachyons and massless states. Various
examples with N even correspond to type 0B orientifolds.Comment: 49 pages, Late
Dyons in Nonabelian Born-Infeld Theory
We analyze a nonabelian extension of Born--Infeld action for the SU(2) group.
In the class of spherically symmetric solutions we find that, besides the
Gal'tsov--Kerner glueballs, only the analytic dyons have finite energy. The
presented analytic and numerical investigation excludes the existence of pure
magnetic monopoles of 't Hooft--Polyakov type.Comment: 12 pages, 3 figure
Non-relativistic limit of Randall-Sundrum model: solutions, applications and constraints
In the Randall-Sundrum model with one brane, we found the approximate and
exact solutions for gravitational potentials and accelerations of test bodies
in these potentials for different geometrical configurations. We applied these
formulas for calculation of the gravitational interaction between two spheres
and found the approximate and exact expressions for the relative force
corrections to the Newton's gravitational force. We demonstrated that the
difference between relative force corrections for the approximate and exact
cases increases with the parameter (for the fixed distance between
centers of the spheres). On the other hand, this difference increases with
decreasing of the distance between the centers of the spheres (for the fixed
curvature scale parameter ). We got the upper limit for the curvature scale
parameter m. For these values of , the difference
between the approximate and exact solutions is negligible.Comment: LaTex 11 pages, 3 figure
Noncommutative geometry, Quantum effects and DBI-scaling in the collapse of D0-D2 bound states
We study fluctuations of time-dependent fuzzy two-sphere solutions of the
non-abelian DBI action of D0-branes, describing a bound state of a spherical
D2-brane with N D0-branes. The quadratic action for small fluctuations is shown
to be identical to that obtained from the dual abelian D2-brane DBI action,
using the non-commutative geometry of the fuzzy two-sphere. For some of the
fields, the linearized equations take the form of solvable Lam\'e equations. We
define a large-N DBI-scaling limit, with vanishing string coupling and string
length, and where the gauge theory coupling remains finite. In this limit, the
non-linearities of the DBI action survive in both the classical and the quantum
context, while massive open string modes and closed strings decouple. We
describe a critical radius where strong gauge coupling effects become
important. The size of the bound quantum ground state of multiple D0-branes
makes an intriguing appearance as the radius of the fuzzy sphere, where the
maximal angular momentum quanta become strongly coupled.Comment: 34 pages, Latex; v2: Minor correction in conformal transformation of
couplings, references adde
Aspects of Large N Gauge Theory Dynamics as Seen by String Theory
In this paper we explore some of the features of large N supersymmetric and
nonsupersymmetric gauge theories using Maldacena's duality conjectures. We
shall show that the resulting strong coupling behavior of the gauge theories is
consistent with our qualitative expectations of these theories. Some of these
consistency checks are highly nontrivial and give additional evidence for the
validity of the proposed dualities.Comment: 31 pages, LaTeX, 11 eps figures, typos correcte
New D=4 gauged supergravities from N=4 orientifolds with fluxes
We consider classes of T_6 orientifolds, where the orientifold projection
contains an inversion I_{9-p} on 9-p coordinates, transverse to a Dp-brane. In
absence of fluxes, the massless sector of these models corresponds to diverse
forms of N=4 supergravity, with six bulk vector multiplets coupled to N=4
Yang--Mills theory on the branes. They all differ in the choice of the duality
symmetry corresponding to different embeddings of SU(1,1)\times SO(6,6+n) in
Sp(24+2n,R), the latter being the full group of duality rotations. Hence, these
Lagrangians are not related by local field redefinitions. When fluxes are
turned on one can construct new gaugings of N=4 supergravity, where the twelve
bulk vectors gauge some nilpotent algebra which, in turn, depends on the choice
of fluxes.Comment: 51 pages, 1 figure. Latex. Reference added. Typos corrected.
Discussion on gaugings expande
Introduction to M Theory and AdS/CFT Duality
An introductory survey of some of the developments that have taken place in
superstring theory in the past few years is presented. The main focus is on
three particular dualities. The first one is the appearance of an 11th
dimension in the strong coupling limit of the type IIA theory, which give rise
to M theory. The second one is the duality between the type IIB theory
compactified on a circle and M theory on a two-torus. The final topic is an
introduction to the recently proposed duality between superstring theory or M
theory on certain anti de Sitter space backgrounds and conformally invariant
quantum field theories.Comment: 26 pages; To be published in the Proceedings of a conference held in
Corfu, Greece in September 1998. v2: reference adde
Non-BPS Dyons and Branes in the Dirac-Born-Infeld Theory
Non-BPS dyon solutions to D3-brane actions are constructed when one or more
scalar fields describing transverse fluctuations of the brane, are considered.
The picture emerging from such non-BPS configurations is analysed, in
particular the response of the D-brane-string system to small perturbations.Comment: 16 pages, 4 figures, Revtex fil
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