434 research outputs found
No-scale N=4 supergravity coupled to Yang-Mills: the scalar potential and super-Higgs effect
We derive the scalar potential of the effective theory of type
IIB orientifold with 3-form fluxes turned on in presence of non abelian brane
coordinates. N=4 supergravity predicts a positive semidefinite potential with
vanishing cosmological constant in the vacuum of commuting coordinates, with a
classical moduli space given by three radial moduli and three RR scalars which
complete three copies of the coset (U(1,1+n)/U(1)\otimes U(1+n)), together with
6n D3-branes coordinates, n being the rank of the gauge group G. Implications
for the super Higgs mechanism are also discussed.Comment: misprints correcte
Spinor Algebras
We consider supersymmetry algebras in space-times with arbitrary signature
and minimal number of spinor generators. The interrelation between super
Poincar\'e and super conformal algebras is elucidated. Minimal super conformal
algebras are seen to have as bosonic part a classical semimisimple algebra
naturally associated to the spin group. This algebra, the Spin-algebra,
depends both on the dimension and on the signature of space time. We also
consider maximal super conformal algebras, which are classified by the
orthosymplectic algebras.Comment: References added, misprints corrected. Version to appear in the
Journal of Geometry and Physic
Holography of the N=1 Higher-Spin Theory on AdS4
We argue that the N=1 higher-spin theory on AdS4 is holographically dual to
the N=1 supersymmetric critical O(N) vector model in three dimensions. This
appears to be a special form of the AdS/CFT correspondence in which both
regular and irregular bulk modes have similar roles and their interplay leads
simultaneously to both the free and the interacting phases of the boundary
theory. We study various boundary conditions that correspond to boundary
deformations connecting, for large-N, the free and interacting boundary
theories. We point out the importance of parity in this holography and
elucidate the Higgs mechanism responsible for the breaking of higher-spin
symmetry for subleading N.Comment: 19 page
The Enhancon, Black Holes, and the Second Law
We revisit the physics of five-dimensional black holes constructed from D5-
and D1-branes and momentum modes in type IIB string theory compactified on K3.
Since these black holes incorporate D5-branes wrapped on K3, an enhancon locus
appears in the spacetime geometry. With a `small' number of D1-branes, the
entropy of a black hole is maximised by including precisely half as many
D5-branes as there are D1-branes in the black hole. Any attempts to introduce
more D5-branes, and so reduce the entropy, are thwarted by the appearance of
the enhancon locus above the horizon, which then prevents their approach. The
enhancon mechanism thereby acts to uphold the Second Law of Thermodynamics.
This result generalises: For each type of bound state object which can be made
of both types of brane, we show that a new type of enhancon exists at
successively smaller radii in the geometry, again acting to prevent any
reduction of the entropy just when needed. We briefly explore the appearance of
the enhancon in the black hole interior.Comment: 22 pages, 2 figures, latex, epsfig (v2: Fixed trivial typos.
Hermitian versus holomorphic complex and quaternionic generalized supersymmetries of the M-theory. A classification
Relying upon the division-algebra classification of Clifford algebras and
spinors, a classification of generalized supersymmetries (or, with a slight
abuse of language,"generalized supertranslations") is provided. In each given
space-time the maximal, saturated, generalized supersymmetry, compatible with
the division-algebra constraint that can be consistently imposed on spinors and
on superalgebra generators, is furnished. Constraining the superalgebra
generators in both the complex and the quaternionic cases gives rise to the two
classes of constrained hermitian and holomorphic generalized supersymmetries.
In the complex case these two classes of generalized supersymmetries can be
regarded as complementary. The quaternionic holomorphic supersymmetry only
exists in certain space-time dimensions and can admit at most a single bosonic
scalar central charge.
The results here presented pave the way for a better understanding of the
various algebra-type of structures which can be introduced in different
space-time signatures and in association with different division algebras, as
well as their mutual relations. In a previous work, e.g., the introduction of a
complex holomorphic generalized supersymmetry was shown to be necessary in
order to perform the analytic continuation of the standard -theory to the
11-dimensional Euclidean space. As an application of the present results, it is
shown that the above algebra also admits a 12-dimensional, Euclidean,
-algebra presentation.Comment: 25 pages, LaTe
Brane-induced supersymmetry breaking
We study spontaneous supersymmetry breaking induced by brane-localized
dynamics in five-dimensional supergravity compactified on S^1/Z_2. We consider
a model with gravity in the bulk and matter localized on tensionless branes at
the orbifold fixed points. We assume that the brane dynamics give rise to
effective brane superpotentials that trigger the supersymmetry breaking. We
analyze in detail the super-Higgs effect. We compute the full spectrum and show
that the symmetry breaking is spontaneous but nonlocal in the fifth dimension.
We demonstrate that the model can be interpreted as a new, non-trivial
implementation of a coordinate-dependent Scherk-Schwarz compactification.Comment: 15 pages. v2: improved treatment of brane actions, relation with
conventional Scherk-Schwarz mechanism clarified, version to be published in
JHE
Evaluation du rôle des vecteurs potentiels dans la circulation du virus Amaril, en 1987 au Sénégal et dans le sud de la République Islamique de Mauritanie
Ce rapport consigne le déroulement de trois enquêtes réalisées sur suspicion de cas humains de fièvre jaune. La première s'est déroulée dans la région de Kaolack, la seconde dans la région de St Louis et la troisième dans celle de Rosso (R.I.M
Dynamics of Higher Spin Fields and Tensorial Space
The structure and the dynamics of massless higher spin fields in various
dimensions are reviewed with an emphasis on conformally invariant higher spin
fields. We show that in D=3,4,6 and 10 dimensional space-time the conformal
higher spin fields constitute the quantum spectrum of a twistor-like particle
propagating in tensorial spaces of corresponding dimensions. We give a detailed
analysis of the field equations of the model and establish their relation with
known formulations of free higher spin field theory.Comment: JHEP3 style, 40 pages; v2 typos corrected, comments and references
added; v3 published versio
Instantons and Matter in N=1/2 Supersymmetric Gauge Theory
We extend the instanton calculus for N=1/2 U(2) supersymmetric gauge theory
by including one massless flavor. We write the equations of motion at leading
order in the coupling constant and we solve them exactly in the
non(anti)commutativity parameter C. The profile of the matter superfield is
deformed through linear and quadratic corrections in C. Higher order
corrections are absent because of the fermionic nature of the back-reaction.
The instanton effective action, in addition to the usual 't Hooft term,
includes a contribution of order C^2 and is N=1/2 invariant. We argue that the
N=1 result for the gluino condensate is not modified by the presence of the new
term in the effective action.Comment: 33 pages, harvmac; v2: minor changes, added references; v3: added
analysis of the instanton measure in section
Duality and Spontaneously Broken Supergravity in Flat Backgrounds
It is shown that the super Higgs mechanism that occurs in a wide class of
models with vanishing cosmological constant (at the classical level) is
obtained by the gauging of a flat group which must be an electric subgroup of
the duality group. If the residual massive gravitinos which occur in the
partial supersymmetry breaking are BPS saturated, then the flat group is non
abelian. This is so for all the models obtained by a Scherk-Schwarz
supersymmetry breaking mechanism. If gravitinos occur in long multiplets, then
the flat groups may be abelian. This is the case of supersymmetry breaking by
string compactifications on an orientifold T^6/Z_2 with non trivial brane
fluxes.Comment: Version to appear on Nuclear Physics
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