52 research outputs found
P-term Potentials from 4-D Supergravity
P-term inflation arises in some models of brane inflation. Within N=2
supersymmetry the scalar potential contains a vector of Fayet-Iliopoulos (FI)
terms . Depending on the direction of this vector it is possible to get
D-term and F-term inflation or a mix of these models. In this paper we review
the problems of embedding the P-term model in supergravity and show how these
can be solved by considering the truncation from an N=2 theory to N=1. We show
that with a simple gauging the scalar potential can include F-term or D-term
parts but not both. The gauging can be altered so that both F-terms and D-terms
containing FI constants can be included. In all cases we display the
inflationary trajectory and, if it exists, the supersymmetric minimum.Comment: 21 pages, no figure
A note on the uniqueness of D=4 N=1 Supergravity
We investigate in 4 spacetime dimensions, all the consistent deformations of
the lagrangian , which is the sum of the
Pauli-Fierz lagrangian for a free massless spin 2 field and the
Rarita-Schwinger lagrangian for a free massless spin 3/2
field. Using BRST cohomogical techniques, we show, under the assumptions of
locality, Poincar\'e invariance, conservation of the number of gauge symmetries
and the number of derivatives on each fields, that N=1 D=4 supergravity is the
only consistent interaction between a massless spin 2 and a massless spin 3/2
field. We do not assume general covariance. This follows automatically, as does
supersymmetry invariance. Various cohomologies related to conservations laws
are also given.Comment: 22+1 pages, LaTeX. References adde
Half-BPS cosmic string in N=2 supergravity in the presence of a dilaton
We construct new half-BPS cosmic string solutions in D=4 N=2 supergravity
compatible with a consistent truncation to N=1 supergravity where they describe
D-term cosmic strings. The constant Fayet-Iliopoulos term in the N=1 D-term is
not put in by hand but is geometrically engineered by a gauging in the mother
N=2 supergravity theory. The coupling of the N=2 vector multiplets is
characterized by a cubic prepotential admitting an axion-dilaton field, a
common property of many compactifications of string theory. The axion-dilaton
field survives the truncation to N=1 supergravity. On the string configuration
the BPS equations constrain the dilaton to be an arbitrary constant. All the
cosmic string solutions with different values of the dilaton have the same
energy per unit length but different lenght scales.Comment: 52 pages; typos correcte
The unphysical nature of the SL(2,R) symmetry and its associated condensates in Yang-Mills theories
BRST cohomology methods are used to explain the origin of the SL(2,R)
symmetry in Yang-Mills theories. Clear evidence is provided for the unphysical
nature of this symmetry. This is obtained from the analysis of a local
functional of mass dimension two and constitutes a no-go statement for giving a
physical meaning to condensates associated with the symmetry breaking of
SL(2,R).Comment: 5 pages (revtex4), final version to appear in Phys. Rev.
Physical Unitarity for Massive Non-abelian Gauge Theories in the Landau Gauge: Stueckelberg and Higgs
We discuss the problem of unitarity for Yang-Mills theory in the Landau gauge
with a mass term a la Stueckelberg. We assume that the theory
(non-renormalizable) makes sense in some subtraction scheme (in particular the
Slavnov-Taylor identities should be respected!) and we devote the paper to the
study of the space of the unphysical modes. We find that the theory is unitary
only under the hypothesis that the 1-PI two-point function of the vector mesons
has no poles (at p^2=0). This normalization condition might be rather crucial
in the very definition of the theory. With all these provisos the theory is
unitary. The proof of unitarity is given both in a form that allows a direct
transcription in terms of Feynman amplitudes (cutting rules) and in the
operatorial form. The same arguments and conclusions apply verbatim to the case
of non-abelian gauge theories where the mass of the vector meson is generated
via Higgs mechanism. To the best of our knowledge, there is no mention in the
literature on the necessary condition implied by physical unitarity.Comment: References added. 22 pages. Final version to appear in the journa
D-term cosmic strings from N=2 Supergravity
We describe new half-BPS cosmic string solutions in N=2, d=4 supergravity
coupled to one vector multiplet and one hypermultiplet. They are closely
related to D-term strings in N=1 supergravity. Fields of the N=2 theory that
are frozen in the solution contribute to the triplet moment map of the
quaternionic isometries and leave their trace in N=1 as a constant
Fayet-Iliopoulos term. The choice of U(1) gauging and of special geometry are
crucial. The construction gives rise to a non-minimal Kaehler potential and can
be generalized to higher dimensional quaternionic-Kaehler manifolds.Comment: 37 pages, LaTeX, v2: minor corrections, references added, version to
be published in JHE
Rational F-Theory GUTs without exotics
We construct F-theory GUT models without exotic matter, leading to the MSSM
matter spectrum with potential singlet extensions. The interplay of engineering
explicit geometric setups, absence of four-dimensional anomalies, and realistic
phenomenology of the couplings places severe constraints on the allowed local
models in a given geometry. In constructions based on the spectral cover we
find no model satisfying all these requirements. We then provide a survey of
models with additional U(1) symmetries arising from rational sections of the
elliptic fibration in toric constructions and obtain phenomenologically
appealing models based on SU(5) tops. Furthermore we perform a bottom-up
exploration beyond the toric section constructions discussed in the literature
so far and identify benchmark models passing all our criteria, which can serve
as a guideline for future geometric engineering.Comment: 27 Pages, 1 Figur
Tate Form and Weak Coupling Limits in F-theory
We consider the weak coupling limit of F-theory in the presence of
non-Abelian gauge groups implemented using the traditional ansatz coming from
Tate's algorithm. We classify the types of singularities that could appear in
the weak coupling limit and explain their resolution. In particular, the weak
coupling limit of SU(n) gauge groups leads to an orientifold theory which
suffers from conifold singulaties that do not admit a crepant resolution
compatible with the orientifold involution. We present a simple resolution to
this problem by introducing a new weak coupling regime that admits
singularities compatible with both a crepant resolution and an orientifold
symmetry. We also comment on possible applications of the new limit to model
building. We finally discuss other unexpected phenomena as for example the
existence of several non-equivalent directions to flow from strong to weak
coupling leading to different gauge groups.Comment: 34 page
D-brane Deconstructions in IIB Orientifolds
With model building applications in mind, we collect and develop basic
techniques to analyze the landscape of D7-branes in type IIB compact Calabi-Yau
orientifolds, in three different pictures: F-theory, the D7 worldvolume theory
and D9-anti-D9 tachyon condensation. A significant complication is that
consistent D7-branes in the presence of O7^- planes are generically singular,
with singularities locally modeled by the Whitney Umbrella. This invalidates
the standard formulae for charges, moduli space and flux lattice dimensions. We
infer the correct formulae by comparison to F-theory and derive them
independently and more generally from the tachyon picture, and relate these
numbers to the closed string massless spectrum of the orientifold
compactification in an interesting way. We furthermore give concrete recipes to
explicitly and systematically construct nontrivial D-brane worldvolume flux
vacua in arbitrary Calabi-Yau orientifolds, illustrate how to read off D-brane
flux content, enhanced gauge groups and charged matter spectra from tachyon
matrices, and demonstrate how brane recombination in general leads to flux
creation, as required by charge conservation and by equivalence of geometric
and gauge theory moduli spaces.Comment: 49 pages, v2: two references adde
Stability of warped AdS3 vacua of topologically massive gravity
AdS3 vacua of topologically massive gravity (TMG) have been shown to be
perturbatively unstable for all values of the coupling constant except the
chiral point \mu l=1. We study the possibility that the warped vacua of TMG,
which exist for all values of \mu, are stable under linearized perturbations.
In this paper, we show that spacelike warped AdS3 vacua with Compere-Detournay
boundary conditions are indeed stable in the range \mu l > 3. This is precisely
the range in which black hole solutions arise as discrete identifications of
the warped AdS3 vacuum. The situation somewhat resembles chiral gravity:
although negative energy modes do exist, they are all excluded by the boundary
conditions, and the perturbative spectrum solely consists of boundary (pure
large gauge) gravitons.Comment: 30 pages, 1 figur
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