Abstract

We study the application of a supersymmetric model with two constrained supermultiplets to inflationary cosmology. The first superfield S is a stabilizer chiral superfield satisfying a nilpotency condition of degree 2, S^2=0. The second superfield Phi is the inflaton chiral superfield, which can be combined into a real superfield B=(Phi-Phi*)/2i. The real superfield B is orthogonal to S, S B=0, and satisfies a nilpotency condition of degree 3, B^3=0. We show that these constraints remove from the spectrum the complex scalar sgoldstino, the real scalar inflaton partner (i.e. the "sinflaton"), and the fermionic inflatino. The corresponding supergravity model with de Sitter vacua describes a graviton, a massive gravitino, and one real scalar inflaton, with both the goldstino and inflatino being absent in unitary gauge. We also discuss relaxed superfield constraints where S^2=0 and S Phi* is chiral, which removes the sgoldstino and inflatino, but leaves the sinflaton in the spectrum. The cosmological model building in both of these inflatino-less models offers some advantages over existing constructions.

Highlights

  • De Sitter space plays a crucial role in our current understanding of cosmological observations [1]

  • 0, and satisfies a nilpotency condition of degree 3, B3 1⁄4 0. We show that these constraints remove from the spectrum the complex scalar sgoldstino, the real scalar inflaton partner, and the fermionic inflatino

  • If supersymmetry is realized in nature, it must be spontaneously broken during any de Sitter phase

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Summary

INTRODUCTION

De Sitter space plays a crucial role in our current understanding of cosmological observations [1]. In the case of a supergravity version of the Starobinsky model, one can use a linear realization of supersymmetry [10] and stabilize the sgoldstino via a Kähler potential term −cðSS Þ2 [11]. The minimal case of local supersymmetry coupled just to S leads to a nonlinear realization of pure de Sitter supergravity without low energy scalars [23,24]. In cosmological models with two unconstrained superfields, one has to work hard to stabilize three of the scalars—ReðSÞ, ImðSÞ, and b—since cosmological data favors a single scalar field inflaton φ. Supergravity models based on orthogonal nilpotent superfields have no inflatino in unitary gauge and no gravitino-inflatino mixing.

Structure in global superspace
Constructing an action
FROM GLOBAL TO LOCAL SUPERSYMMETRY
Importance of unitary gauge
Imposing the constraints
Simplification in unitary gauge
A nonstandard potential
Derivation from the off-shell action
SUPERGRAVITY POTENTIAL WITH CONSTRAINED SUPERFIELDS
INFLATINO-LESS MODELS WITH ORTHOGONAL NILPOTENT MULTIPLETS
Action in unitary gauge
ALTERNATIVE INFLATINO-LESS CONSTRUCTIONS
Linear S terms in the Kähler potential
Relaxed constraints
DISCUSSION
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