54 research outputs found
Inflation, Leptogenesis, and Yukawa Quasi-Unification within a Supersymmetric Left-Right Model
A simple extension of the minimal left-right symmetric supersymmetric grand
unified theory model is constructed by adding two pairs of superfields. This
naturally violates the partial Yukawa unification predicted by the minimal
model. After including supergravity corrections, we find that this extended
model naturally supports hilltop F-term hybrid inflation along its trivial
inflationary path with only a very mild tuning of the initial conditions. With
a convenient choice of signs of the terms in the Kahler potential, we can
reconcile the inflationary scale with the supersymmetric grand unified theory
scale. All the current data on the inflationary observables are readily
reproduced. Inflation is followed by non-thermal leptogenesis via the decay of
the right-handed neutrinos emerging from the decay of the inflaton and any
possible washout of the lepton asymmetry is avoided thanks to the violation of
partial Yukawa unification. The extra superfields also assist us in reducing
the reheat temperature so as to satisfy the gravitino constraint. The observed
baryon asymmetry of the universe is naturally reproduced consistently with the
neutrino oscillation parameters.Comment: 20 pages including 4 figure
Anomalous U(1) Models in Four and Five Dimensions and their Anomaly Poles
We analyze the role played by anomaly poles in an anomalous gauge theory by
discussing their signature in the corresponding off-shell effective action. The
origin of these contributions, in the most general kinematical case, is
elucidated by performing a complete analysis of the anomaly vertex at
perturbative level. We use two independent (but equivalent) representations:
the Rosenberg representation and the longitudinal/transverse (L/T)
parameterization, used in recent studies of of the muon and in the proof
of non-renormalization theorems of the anomaly vertex. The poles extracted from
the L/T parameterization do not couple in the infrared for generic anomalous
vertices, as in Rosenberg, but we show that they are responsible for the
violations of unitarity in the UV region, using a class of pole-dominated
amplitudes. We conclude that consistent formulations of anomalous models
require necessarily the cancellation of these polar contributions. Establishing
the UV significance of these terms provides a natural bridge between the
anomalous effective action and its completion by a nonlocal theory. Some
additional difficulties with unitarity of the mechanism of inflow in extra
dimensional models with an anomalous theory on the brane, due to the presence
of anomaly poles, are also pointed out.Comment: Revised final version, to appear on JHE
Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model
We discuss the main features of dilaton interactions for fundamental and
effective dilaton fields. In particular, we elaborate on the various ways in
which dilatons can couple to the Standard Model and on the role played by the
conformal anomaly as a way to characterize their interactions. In the case of a
dilaton derived from a metric compactification (graviscalar), we present the
structure of the radiative corrections to its decay into two photons, a photon
and a , two gauge bosons and two gluons, together with their
renormalization properties. We prove that, in the electroweak sector, the
renormalization of the theory is guaranteed only if the Higgs is conformally
coupled. For such a dilaton, its coupling to the trace anomaly is quite
general, and determines, for instance, an enhancement of its decay rates into
two photons and two gluons. We then turn our attention to theories containing a
non-gravitational (effective) dilaton, which, in our perturbative analysis,
manifests as a pseudo-Nambu Goldstone mode of the dilatation current ().
The infrared coupling of such a state to the two-photons and to the two-gluons
sector, and the corresponding anomaly enhancements of its decay rates in these
channels, is critically analyzed.Comment: Revised version, 42 pages, 5 figure
Comments on Anomaly Cancellations by Pole Subtractions and Ghost Instabilities with Gravity
We investigate some aspects of anomaly cancellation realized by the
subtraction of an anomaly pole, stressing on some of its properties in
superspace. In a local formulation these subtractions can be described in terms
of a physical scalar, an axion and related ghosts. They appear to be necessary
for the unitarization of the theory in the ultraviolet, but they may generate
an infrared instability of the corresponding effective action, signalled by
ghost condensation. In particular the subtraction of the superanomaly multiplet
by a pole in superspace is of dubious significance, due to the different nature
of the chiral and conformal anomalies. In turn, this may set more stringent
constraints on the coupling of supersymmetric theories to gravity.Comment: 18 pages. Revised version. To appear in "Classical and Quantum
Gravity
Cosmological Properties of a Gauged Axion
We analyze the most salient cosmological features of axions in extensions of
the Standard Model with a gauged anomalous extra U(1) symmetry. The model is
built by imposing the constraint of gauge invariance in the anomalous effective
action, which is extended with Wess-Zumino counterterms. These generate
axion-like interactions of the axions to the gauge fields and a gauged shift
symmetry. The scalar sector is assumed to acquire a non-perturbative potential
after inflation, at the electroweak phase transition, which induces a mixing of
the Stuckelberg field of the model with the scalars of the electroweak sector,
and at the QCD phase transition. We discuss the possible mechanisms of
sequential misalignments which could affect the axions of these models, and
generated, in this case, at both transitions. We compute the contribution of
these particles to dark matter, quantifying their relic densities as a function
of the Stuckelberg mass. We also show that models with a single anomalous U(1)
in general do not account for the dark energy, due to the presence of mixed
U(1)-SU(3) anomalies.Comment: 29 pages, 5 figures. Revised version, accepted by Phys. Rev.
A Light Supersymmetric Axion in an Anomalous Abelian Extension of the Standard Model
We present a supersymmetric extension of the Standard Model (USSM-A) with an
anomalous U(1) and Stueckelberg axions for anomaly cancellation, generalizing
similar non-supersymmetric constructions. The model, built by a bottom-up
approach, is expected to capture the low-energy supersymmetric description of
axionic symmetries in theories with gauged anomalous abelian interactions,
previously explored in the non-supersymmetric case for scenarios with
intersecting branes. The choice of a USSM-like superpotential, with one extra
singlet superfield and an extra abelian symmetry, allows a physical axion-like
particle in the spectrum. We describe some general features of this
construction and in particular the modification of the dark-matter sector which
involves both the axion and several neutralinos with an axino component. The
axion is expected to be very light in the absence of phases in the
superpotential but could acquire a mass which can also be in the few GeV range
or larger. In particular, the gauging of the anomalous symmetry allows
independent mass/coupling interaction to the gauge fields of this particle, a
feature which is absent in traditional (invisible) axion models. We comment on
the general implications of our study for the signature of moduli from string
theory due to the presence of these anomalous symmetries.Comment: 46 pages, 28 figures. Revised version, accepted for a publication on
Phys.Rev.
Graviton Vertices and the Mapping of Anomalous Correlators to Momentum Space for a General Conformal Field Theory
We investigate the mapping of conformal correlators and of their anomalies
from configuration to momentum space for general dimensions, focusing on the
anomalous correlators , - involving the energy-momentum tensor
with a vector or a scalar operator () - and the 3-graviton vertex
. We compute the , and one-loop vertex functions in
dimensional regularization for free field theories involving conformal scalar,
fermion and vector fields. Since there are only one or two independent tensor
structures solving all the conformal Ward identities for the or
vertex functions respectively, and three independent tensor structures for the
vertex, and the coefficients of these tensors are known for free fields,
it is possible to identify the corresponding tensors in momentum space from the
computation of the correlators for free fields. This works in general
dimensions for and correlators, but only in 4 dimensions for ,
since vector fields are conformal only in . In this way the general
solution of the Ward identities including anomalous ones for these correlators
in (Euclidean) position space, found by Osborn and Petkou is mapped to the
ordinary diagrammatic one in momentum space. We give simplified expressions of
all these correlators in configuration space which are explicitly Fourier
integrable and provide a diagrammatic interpretation of all the contact terms
arising when two or more of the points coincide. We discuss how the anomalies
arise in each approach [...]Comment: 57 pages, 7 figures. Refs adde
Photon-Graviton Amplitudes from the Effective Action
We report on the status of an ongoing effort to calculate the complete
one-loop low-energy effective actions in Einstein-Maxwell theory with a massive
scalar or spinor loop, and to use them for obtaining the explicit form of the
corresponding M-graviton/N-photon amplitudes. We present explicit results for
the effective actions at the one-graviton four-photon level, and for the
amplitudes at the one-graviton two-photon level. As expected on general
grounds, these amplitudes relate in a simple way to the corresponding
four-photon amplitudes. We also derive the gravitational Ward identity for the
1PI one-graviton -- N photon amplitude.Comment: 9 pages, 2 figures, talk given by C. Schubert at "Supersymmetries and
Quantum Symmetries - SQS`2011", JINR Dubna, July 18 - 23, 2011 (to appear in
the Proceedings
Electric/magnetic duality for chiral gauge theories with anomaly cancellation
We show that 4D gauge theories with Green-Schwarz anomaly cancellation and
possible generalized Chern-Simons terms admit a formulation that is manifestly
covariant with respect to electric/magnetic duality transformations. This
generalizes previous work on the symplectically covariant formulation of
anomaly-free gauge theories as they typically occur in extended supergravity,
and now also includes general theories with (pseudo-)anomalous gauge
interactions as they may occur in global or local N=1 supersymmetry. This
generalization is achieved by relaxing the linear constraint on the embedding
tensor so as to allow for a symmetric 3-tensor related to electric and/or
magnetic quantum anomalies in these theories. Apart from electric and magnetic
gauge fields, the resulting Lagrangians also feature two-form fields and can
accommodate various unusual duality frames as they often appear, e.g., in
string compactifications with background fluxes.Comment: 37 pages; v2: typos corrected and 1 reference adde
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