arXiv subjects

Renata Kallosh

Publications and source records attributed to Renata Kallosh.

At least 127 records · Page 7Linked to original sources

arXiv2013

Higher Order Corrections in Minimal Supergravity Models of Inflation

We study higher order corrections in new minimal supergravity models of a single scalar field inflation. The gauging in these models leads to a massive vector multiplet and the D-term potential for the inflaton field with a coupling g^{2} ~ 10^{-10}. In the de-Higgsed phase with vanishing g^2, the chiral and vector multiplets are non-interacting, and the potential vanishes. We present generic manifestly supersymmetric higher order corrections for these models. In particular, for a supersymmetric gravity model -R+ R^2 we derive manifestly supersymmetric corrections corresponding to R^n. The dual version corresponds to a standard supergravity model with a single scalar and a massive vector. It includes, in addition, higher Maxwell curvature/scalar interaction terms of the Born-Infeld type and a modified D-term scalar field potential. We use the dual version of the model to argue that higher order corrections do not affect the last 60 e-foldings of inflation; for example the ξR^4 correction is irrelevant as long as ξ< 10^{24}.

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arXiv2013

Superconformal Inflationary $α$-Attractors

Recently a broad class of superconformal inflationary models was found leading to a universal observational prediction $n_s=1-2/N$ and $r=12/N^2$. Here we generalize this class of models by introducing a parameter $α$ inversely proportional to the curvature of the inflaton Kahler manifold. In the small curvature (large $α$) limit, the observational predictions of this class of models coincide with the predictions of generic chaotic inflation models. However, for sufficiently large curvature (small $α$), the predictions converge to the universal attractor regime with $n_s=1-2/N$ and $r=12α/N^2$, which corresponds to the part of the $n_s-r$ plane favored by the Planck data.

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arXiv2013

Minimal Supergravity Models of Inflation

We present a superconformal master action for a class of supergravity models with one arbitrary function defining the Jordan frame. It leads to a gauge-invariant action for a real vector multiplet, which upon gauge fixing describes a massive vector multiplet, or to a dual formulation with a linear multiplet and a massive tensor field. In both cases the models have one real scalar, the inflaton, naturally suited for single-field inflation. Vectors and tensors required by supersymmetry to complement a single real scalar do not acquire vev's during inflation, so there is no need to stabilize the extra scalars which are always present in the theories with chiral matter multiplets. The new class of models can describe any inflaton potential which vanishes at its minimum and grows monotonically away from the minimum. In this class of supergravity models one can fit any desirable choice of inflationary parameters n_s and r.

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arXiv2013

On the Supersymmetric Completion of $R+R^2$ Gravity and Cosmology

We revisit and clarify the supersymmetric versions of $R+ R^2$ gravity, in view of the renewed interest to these models in cosmology. We emphasize that the content of the dual standard supergravity theory in the old minimal formulation necessarily includes two massive chiral multiplets, that we call the inflaton and the goldstino. We point out that the presence of these multiplets is model independent in the old minimal formulation and therefore any theory that contains a single chiral multiplet fails to be a supersymmetric generalization of the $R+R^2$ gravity. The supergravity interactions of the two chiral multiplets are encoded in a superpotential mass term and an arbitrary Kahler potential for the goldstino multiplet. The implication for cosmology of the supersymmetric $R+R^2$ gravity is also discussed.

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arXiv2013

Universality Class in Conformal Inflation

We develop a new class of chaotic inflation models with spontaneously broken conformal invariance. Observational consequences of a broad class of such models are stable with respect to strong deformations of the scalar potential. This universality is a critical phenomenon near the point of enhanced symmetry, SO(1,1), in case of conformal inflation. It appears because of the exponential stretching of the moduli space and the resulting exponential flattening of scalar potentials upon switching from the Jordan frame to the Einstein frame in this class of models. This result resembles stretching and flattening of inhomogeneities during inflationary expansion. It has a simple interpretation in terms of velocity versus rapidity near the Kahler cone in the moduli space, similar to the light cone of special theory of relativity. This effect makes inflation possible even in the models with very steep potentials. We describe conformal and superconformal versions of this cosmological attractor mechanism.

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arXiv2013

Non-minimal Inflationary Attractors

Recently we identified a new class of (super)conformally invariant theories which allow inflation even if the scalar potential is very steep in terms of the original conformal variables. Observational predictions of a broad class of such theories are nearly model-independent. In this paper we consider generalized versions of these models where the inflaton has a non-minimal coupling to gravity with ξ<0 different from its conformal value ξ= -1/6. We show that these models exhibit attractor behavior. With even a slight increase of |ξ| from |ξ| = 0, predictions of these models for n_s and r rapidly converge to their universal model-independent values corresponding to conformal coupling ξ= -1/6. These values of n_s and r practically coincide with the corresponding values in the limit of infinitely large negative ξ.

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arXiv2013

Multi-field Conformal Cosmological Attractors

We describe a broad class of multi-field inflationary models with spontaneously broken conformal invariance. It generalizes the recently discovered class of cosmological attractors with a single inflaton field. In the new multi-field theories, just as in the previously studied single-field models, the moduli space has a boundary (Kahler cone) in terms of the original homogeneous conformal variables. Upon spontaneous breaking of the conformal invariance and switching to the Einstein frame, this boundary moves to infinity in terms of the canonically normalized inflaton field. This results in the exponential stretching and flattening of scalar potentials in the vicinity of the boundary of the moduli space, which makes even very steep potentials perfectly suitable for the slow-roll inflation. These theories, just like their single-field versions, typically lead to inflationary perturbations with n_s =1-2/N and r = 12/N^2, where N is the number of e-foldings.

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arXiv2013

Superconformal Generalization of the Chaotic Inflation Model λϕ^4/4 - ξ/ 2 ϕ^2 R

A model of chaotic inflation based on the theory of a scalar field with potential λϕ^4 perfectly matches the observational data if one adds to it a tiny non-minimal coupling to gravity -ξ/2 ϕ^2 R with ξ> 0.002. We describe embedding of this model into the superconformal theory with spontaneous breaking of superconformal symmetry, and into supergravity. A model with small ξis technically natural: setting the small parameter ξto zero leads to a point of enhanced symmetry in the underlying superconformal theory.

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arXiv2013

Superconformal generalizations of the Starobinsky model

We find a way to represent the Starobinsky model in terms of a simple conformally invariant theory with spontaneous symmetry breaking. We also present a superconformal theory, which, upon spontaneous breaking of the superconformal symmetry, provides a consistent supergravity generalization of the Starobinsky model.

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arXiv2013

Dirac-Born-Infeld-Volkov-Akulov and Deformation of Supersymmetry

We deform the action and the supersymmetry transformations of the d=10 and d=4 Maxwell supermultiplets so that at each order of the deformation the theory has 16 Maxwell multiplet deformed supersymmetries as well as 16 Volkov-Akulov type non-linear supersymmetries. The result agrees with the expansion in the string tension of the explicit action of the Dirac-Born-Infeld model and its supersymmetries, extracted from D9 and D3 superbranes, respectively. The half-maximal Dirac-Born-Infeld models with 8 Maxwell supermultiplet deformed supersymmetries and 8 Volkov-Akulov type supersymmetries are described by a new class of d=6 vector branes related to chiral (2,0) supergravity, which we denote as `Vp-branes'. We use a space-filling V5 superbrane for the d=6 model and a V3 superbrane for the d=4 half-maximal Dirac-Born-Infeld (DBI) models. In this way we present a completion to all orders of the deformation of the Maxwell supermultiplets with maximal 16+16 supersymmetries in d=10 and 4, and half-maximal 8+8 supersymmetries in d=6 and 4.

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arXiv2013

Hidden Supersymmetry May Imply Duality Invariance

We provide evidence that a particular hidden supersymmetry, when combined with half-maximal deformed global supersymmetry, implies that the theory is invariant under duality rotations of the vector and spinor fields. Based on a complete 8+8 supersymmetric model constructed recently, we argue that this hidden supersymmetry happens if and only if there is a Born-Infeld dependence on the Maxwell field strength and a Volkov-Akulov dependence on the Goldstino, up to local non-linear field redefinitions. We have tested our proposal for the N=2 superfield action with manifest N=2 supersymmetry and hidden N=2 supersymmetry at the level W^{10}, the highest level of deformation known for this model. We have established that it is N=2 self-dual, although the self-duality was not required in the original construction of this model. Highlighting the utility of considering duality-conserving sources of deformation, we can verify this invariance directly in an alternate construction of this very same action.

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arXiv2013

Obstruction to E_{7(7)} Deformation in N=8 Supergravity

Candidate counterterms break Noether-Gaillard-Zumino E_{7(7)} current conservation in N=8 supergravity in four dimensions. Bossard and Nicolai proposed a scheme for deforming the subsector involving vector fields in a Lorentz covariant manner, so as to restore duality. They argued that there must exist an extension of this deformation to the full theory that preserves supersymmetry. We show that it is not possible to deform the maximal supergravity to restore E_{7(7)} duality, while maintaining both general covariance and N=8 supersymmetry, as was proposed. Deformation of N=8 supergravity requires higher spins and multiple gravitons, which presents a concrete obstacle to this proposal.

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arXiv2013

Conjecture on Hidden Superconformal Symmetry of N=4 Supergravity

We argue that the observed UV finiteness of the 3-loop extended supergravities may be a manifestation of a hidden local superconformal symmetry of supergravity. We focus on the SU(2,2|4) dimensionless superconformal model. In Poincare gauge where the compensators are fixed to phi^2= 6 M_P^2 this model becomes a pure classical N=4 Einstein supergravity. We argue that in N=4 the higher-derivative superconformal invariants like phi^{-4}W^2 \bar W^2 and the consistent local anomaly delta (ln phi W^2) are not available. This conjecture on hidden local N=4 superconformal symmetry of Poincare supergravity may be supported by subsequent loop computations.

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arXiv2012

Degeneration of Groups of Type E7 and Minimal Coupling in Supergravity

We study properties of D = 4, N >1 extended supergravities (and related compactifications of superstring theory) and their consistent truncation to the phenomenologically interesting models of N = 1 supergravity. This involves a detailed classification of the "degenerations" of the duality groups of type E7, when the corresponding quartic invariant polynomial built from the symplectic irreducible representation of G4 "degenerates" into a perfect square. With regard to cosmological applications, we conclude that the consistent truncation to N = 1 from higher-dimensional or higher-N theory gives a zero measure minimal coupling of vectors. A non-minimal coupling involving vectors coupled to scalars and axions is generic. These features of supergravity, following from the electric-magnetic duality, may be useful in other applications, like stabilization of moduli, and in studies of non-perturbative black-hole solutions of supergravity/string theory.

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arXiv2012

New E77 invariants and amplitudes

We construct a new class of manifest E77 duality invariants, which generalize the Cartan quartic invariant, familiar from studies of the black hole entropy. The new ones, being four-linear, are designed for studies of the four-vector amplitudes and to be used, upon supersymmetrization, as initial sources of deformation for the non-linear higher-derivative generalizations of the linear twisted self-duality condition. We show, however, that the new invariants are inconsistent with the expected UV divergent amplitudes in extended supergravities with non-degenerate duality groups of type E7. When E77 degenerates into U(1) the new invariants reproduce the recently discovered source of deformation for the Born-Infeld duality invariant model with higher derivatives relevant to UV divergences of the D3 brane action. These facts may explain the UV properties of perturbative supergravity.

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arXiv2012

Covariant procedures for perturbative non-linear deformation of duality-invariant theories

We analyze a recent conjecture regarding the perturbative construction of non-linear deformations of all classically duality invariant theories, including N=8 supergravity. Starting with an initial quartic deformation, we engineer a procedure that generates a particular non-linear deformation (Born-Infeld) of the Maxwell theory. This procedure requires the introduction of an infinite number of modifications to a constraint which eliminates degrees of freedom consistent with the duality and field content of the system. We discuss the extension of this procedure to N=1 and N=2 supersymmetric theories, and comment on its potential to either construct new supergravity theories with non-linear Born-Infeld type duality, or to constrain the finiteness of N=8 supergravity.

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arXiv2012

On Absence of 3-loop Divergence in N=4 Supergravity

We argue that N=4 supergravity is 3-loop UV finite because the relevant supersymmetric candidate counterterm is known to be SL(2, R)x SO(6) invariant, which violates the Noether-Gaillard-Zumino current conservation. Analogous arguments, based on the universality properties of groups of type E7, also apply to N=5,6,8 in 4,5,7 loops, respectively, since the 1/N BPS invariants break duality symmetry between Bianchi identities and quantum corrected vector field equations.

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arXiv2012

N=2 Supersymmetry and U(1)-Duality

Understanding the consequences of the E_{7(7)} duality on the UV properties of N=8 supergravity requires unravelling when and how duality-covariant actions can be constructed so as to accommodate duality-invariant counter-terms. For non-supersymmetric abelian gauge theories exhibiting U(1)-duality, with and without derivative couplings, it was shown that such a covariant construction is always possible. In this paper we describe a similar procedure for the construction of covariant non-linear deformations of U(1)-duality invariant theories in the presence of rigid N=2 supersymmetry. This is a concrete step towards studying the interplay of duality and extended supersymmetry.

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