219 research outputs found
Embedding Branes in Flat Two-time Spaces
We show how non-near horizon, non-dilatonic -brane theories can be
obtained from two embedding constraints in a flat higher dimensional space with
2 time directions. In particular this includes the construction of D3 branes
from a flat 12-dimensional action, and M2 and M5 branes from 13 dimensions. The
worldvolume actions are found in terms of fields defined in the embedding
space, with the constraints enforced by Lagrange multipliers.Comment: LaTex, 8 pages. Contribution to the TMR Conference on Quantum aspects
of gauge theories, supersymmetry and unification. Paris, 1-7 September 199
The Scherk-Schwarz mechanism as a flux compactification with internal torsion
The aim of this paper is to make progress in the understanding of the
Scherk-Schwarz dimensional reduction in terms of a compactification in the
presence of background fluxes and torsion. From the eleven dimensional
supergravity point of view, we find that a general E6(6) S-S phase may be
obtained by turning on an appropriate background torsion, together with
suitable fluxes, some of which can be directly identified with certain
components of the four-form field-strength. Furthermore, we introduce a novel
(four dimensional) approach to the study of dualities between flux/torsion
compactifications of Type II/M-theory. This approach defines the action that
duality should have on the background quantities, in order for the E7(7)
invariance of the field equations and Bianchi identities to be restored also in
the presence of fluxes/torsion. This analysis further implies the
interpretation of the torsion flux as the T-dual of the NS three-form flux.Comment: Version published on J. High Energy Phy
N=4 gauged supergravity and a IIB orientifold with fluxes
We analyze the properties of a spontaneously broken D=4, N=4 supergravity
without cosmological constant, obtained by gauging translational isometries of
its classical scalar manifold. This theory offers a suitable low energy
description of the super-Higgs phases of certain Type-IIB orientifold
compactifications with 3-form fluxes turned on. We study its N=3,2,1,0 phases
and their classical moduli spaces and we show that this theory is an example of
no-scale extended supergravity.Comment: Misprints corrected. Version appeared on NJP 4 (2002)7
Axion gauge symmetries and generalized Chern-Simons terms in N=1 supersymmetric theories
We compute the form of the Lagrangian of N=1 supersymmetric theories with
gauged axion symmetries. It turns out that there appear generalized
Chern-Simons terms that were not considered in previous superspace formulations
of general N=1 theories. Such gaugings appear in supergravities arising from
flux compactifications of superstrings, as well as from Scherk-Schwarz
generalized dimensional reduction in M-theory. We also present the dual
superspace formulation where axion chiral multiplets are dualized into linear
multiplets.Comment: References added and few misprints correcte
Black-Hole Attractors in N=1 Supergravity
We study the attractor mechanism for N=1 supergravity coupled to vector and
chiral multiplets and compute the attractor equations of these theories. These
equations may have solutions depending on the choice of the holomorphic
symmetric matrix f_{\Lambda\Sigma} which appears in the kinetic lagrangian of
the vector sector. Models with non trivial electric-magnetic duality group
which have or have not attractor behavior are exhibited. For a particular class
of models, based on an N=1 reduction of homogeneous special geometries, the
attractor equations are related to the theory of pure spinors.Comment: 25 pages, typos corrected, formulas adde
On Central Charges and Hamiltonians for 0-brane dynamics
We consider general properties of central charges of zero branes and
associated duality invariants, in view of their double role, on the bulk and on
the world volume (quantum-mechanical) theory. A detailed study of the BPS
condition for the mass spectrum arising from toroidal compactifications is
given for 1/2, 1/4 and 1/8 BPS states in any dimensions. As a byproduct, we
retreive the U-duality invariant conditions on the charge (zero mode) spectrum
and the orbit classification of BPS states preserving different fractions of
supersymmetry. The BPS condition for 0-branes in theories with 16
supersymmetries in any dimension is also discussed.Comment: 23 pages, latex fil
On twist-two operators in N=4 SYM
We propose a mechanism for calculating anomalous dimensions of higher-spin
twist-two operators in N=4 SYM. We consider the ratio of the two-point
functions of the operators and of their superconformal descendants or,
alternatively, of the three-point functions of the operators and of the
descendants with two protected half-BPS operators. These ratios are
proportional to the anomalous dimension and can be evaluated at n-1 loop in
order to determine the anomalous dimension at n loops. We illustrate the method
by reproducing the well-known one-loop result by doing only tree-level
calculations. We work out the complete form of the first-generation descendants
of the twist-two operators and the scalar sector of the second-generation
descendants.Comment: references added; typos correcte
Potential and mass-matrix in gauged N=4 supergravity
We discuss the potential and mass-matrix of gauged N=4 matter coupled
supergravity for the case of six matter multiplets, extending previous work by
considering the dependence on all scalars. We consider all semi-simple gauge
groups and analyse the potential and its first and second derivatives in the
origin of the scalar manifold. Although we find in a number of cases an
extremum with a positive cosmological constant, these are not stable under
fluctuations of all scalar fields.Comment: 28 pages, LaTe
Vector/tensor duality in the five dimensional supersymmetric Green-Schwarz mechanism
The five dimensional version of the Green-Schwarz mechanism can be invoked to
cancel U(1) anomalies on the boundaries of brane world models. In five
dimensions there are two dual descriptions that employ either a two-form tensor
field or a vector field. We present the supersymmetric extensions of these dual
theories using four dimensional N=1 superspace. For the supersymmetrization of
the five dimensional Chern-Simons three form this requires the introduction of
a new chiral Chern-Simons multiplet. We derive the supersymmetric vector/tensor
duality relations and show that not only is the usual one/two-form duality
modified, but that there is also an interesting duality relation between the
scalar components. Furthermore, the vector formulation always contains singular
boundary mass terms which are absent in the tensor formulation. This apparent
inconsistency is resolved by showing that in either formulation the four
dimensional anomalous U(1) mass spectrum is identical, with the lowest lying
Kaluza-Klein mode generically obtaining a finite nonzero mass.Comment: 1+35 pages, LaTeX, 1 figure, references added, typos correcte
N=4 Supergravity Lagrangian for Type IIB Orientifold on T^6/Z_2 in Presence of Fluxes and D3-Branes
We derive the Lagrangian and the transformation laws of N=4 gauged
supergravity coupled to matter multiplets whose sigma-model of the scalars is
SU(1,1)/U(1)x SO(6,6+n)/SO(6)xSO(6+n) and which corresponds to the effective
Lagrangian of the Type IIB string compactified on the T^6/Z_2 orientifold with
fluxes turned on and in presence of n D3-branes. The gauge group is T^12 x G
where G is the gauge group on the brane and T^12 is the gauge group on the bulk
corresponding to the gauged translations of the R-R scalars coming from the R-R
four--form. The N=4 bulk sector of this theory can be obtained as a truncation
of the Scherk-Schwarz spontaneously broken N=8 supergravity. Consequently the
full bulk spectrum satisfies quadratic and quartic mass sum rules, identical to
those encountered in Scherk-Schwarz reduction gauging a flat group. This theory
gives rise to a no scale supergravity extended with partial super-Higgs
mechanism.Comment: 49 pages, LaTex, 2 figures. Misprints corrected, more comments adde
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