Dynamical mass generation for the gravitino in N = 1 supergravity

The Volkov-Akulov field is coupled to supergravity and it is gauged away through a field redefinition, remaining with a negative cosmological constant plus N = 1 supergravity lagrangian. Then the gravitino sector is quantized and a positive cosmological constant is obtained along with a mass-like term for the gravitino. Imposing the effective cosmological constant to be zero, consequently a genuine mass term for the gravitino is obtained. The corresponding energy-gap equation shows that this mass turns out to be of the order of the Planck mass.     

Super-higgs effect in supergravity with general scalar interactions

Using the recently established tensor calculus for supergravity, we construct the most general action for the scalar multiplet coupling. We discuss under which conditions supersymmetry is broken spontaneously and show explicitly that the gravitino acquires a mass by absorbing the Goldstone fermion. Parity violation as well as a cosmological constant can be avoided.     

Supersymmetry breaking with vanishing F-terms in supergravity theories

In conventional supergravity theories, supersymmetry is broken by a non-zero F-term, and the cosmological constant is fine tuned to zero by a constant in the superpotential W. We discuss a class of supergravity theories with vanishing F-terms but W ≠ 0 being generated dynamically. The cosmological constant is assumed to be cancelled by a non-zero D-term. In this scenario the gravity-mediated soft masses depend only on a single parameter, the gravitino mass. They are automatically universal, independently of the Kähler metric, and real. Thus, dangerous flavor or CP violating interactions are suppressed. Unlike in conventional supergravity models, the Polonyi problem does not arise.     

Vacuum fluctuations of the supersymmetric field in curved background

We study a supersymmetric model in curved background spacetime. We calculate the effective action and the vacuum expectation value of the energy momentum tensor using a covariant regularization procedure. A soft supersymmetry breaking induces a nonzero contribution to the vacuum energy density and pressure. Assuming the presence of a cosmic fluid in addition to the vacuum fluctuations of the supersymmetric field an effective equation of state is derived in a self-consistent approach at one loop order. The net effect of the vacuum fluctuations of the supersymmetric fields in the leading adiabatic order is a renormalization of the Newton and cosmological constants.     

Semi-local cosmic strings and the cosmological constant problem

We study the cosmological constant problem in a three-dimensional N = 2 supergravity theory with gauge groupSU (2)_global × U(1)_local. The model we consider is known to admit string-like configurations, the so-called semi-local cosmic strings. We show that the stability of these solitonic solutions is provided by supersymmetry through the existence of a lower bound for the energy, even though the manifold of the Higgs vacuum does not contain non-contractible loops. Charged Killing spinors do exist over configurations that saturate the Bogomol'nyi bound, as a consequence of an Aharonov-Bohm-like effect. Nevertheless, there are no physical fermionic zero modes on these backgrounds. The exact vanishing of the cosmological constant does not imply, then, Bose-Fermi degeneracy. This provides a non-trivial example of the recent claim made by Witten on the vanishing of the cosmological constant in three dimensions without unphysical degeneracies.     

Supersymmetron

We consider a supersymmetric model of dark energy coupled to cold dark matter: the supersymmetron. In the absence of cold dark matter, the supersymmetron converges to a supersymmetric minimum with a vanishing cosmological constant. When cold dark matter is present, the supersymmetron evolves to a matter dependent minimum where its energy density does not vanish. In the early Universe until the recent past of the Universe, the energy density of the supersymmetron is negligible compared to the cold dark matter energy density. Away from the supersymmetric minimum, the equation of state of the supersymmetron is constant and negative. When the supersymmetron reaches the neighbourhood of the supersymmetric minimum, its equation of state vanishes rapidly. This leads to an acceleration of the Universe which is transient unless supersymmetry breaking induces a pure cosmological constant and acceleration of the Universe does not end. Moreover, we find that the mass of supersymmetron is always greater than the gravitino mass. As a result, the supersymmetron generates a short ranged fifth force which evades gravitational tests. On the other hand, we find that the supersymmetron may lead to relevant effects on large scale structures.     

Supergravity,R invariance and spontaneous supersymmetry breaking

We show that in order for a U(1) gauge theory with a Fayet-Illiopoulos term to be consistently coupled to supergravity, preserving gauge invariance, the superpotential must be R invariant. A supersymmetric cosmological term and therefore an explicit mass-like term for the gravitino is forbidden by gauge invariance. This result severely constrains the possible models for non-gravitational interactions. We comment on possible mass term the gauginos induced by gravitational effects.     

Weak scale supersymmetry without weak scale supergravity

It is generally believed that weak scale supersymmetry implies weak scale supergravity, in the sense that the masses of the gravitino and gravitationally coupled moduli have masses below 100 TeV. This Letter presents a realistic framework for supersymmetry breaking in which these masses can be much larger. This solves the cosmological problems of hidden sector models. Supersymmetry breaking is communicated to the visible sector by anomaly-mediated supersymmetry breaking. The framework is compatible with perturbative gauge coupling unification and can be realized either in models of "warped" extra dimensions or in strongly coupled four-dimensional conformal field theories.     

Vanishing scalar masses in no-scale supergravity

Radiative corrections to the effective scalar potential are studied in no-scale supergravity models with local supersymmetry spontaneously broken by a gravitino mass. A simple proof is given that gauge non-singlet scalar fields acquire no supersymmetry breaking masses at the one-loop level, and a general argument is given extending this result to all orders of perturbation theory in the effective low-energy theory, proving also that no trilinear soft supersymmetry breaking terms in the effective potential are generated. These results are applicable to the four-dimensional no-scale supergravity theory obtained from the superstring after compactification, and support suggestions that the dominant source of global supersymmetry breaking in this theory may be the gaugino mass.     

Modified weak energy condition for the energy momentum tensor in quantum field theory

The weak energy condition is known to fail in general when applied to expectation values of the energy momentum tensor in flat space quantum field theory. It is shown how the usual counter arguments against its validity are no longer applicable if the states |ψ〉 for which the expectation value is considered are restricted to a suitably defined subspace. A possible natural restriction on |ψ〉 is suggested and illustrated by two quantum mechanical examples based on a simple perturbed harmonic oscillator Hamiltonian. The proposed alternative quantum weak energy condition is applied to states formed by the action of the scalar, vector and the energy momentum tensor operators on the vacuum. We assume conformal invariance in order to determine almost uniquely three-point functions involving the energy momentum tensor in terms of a few parameters. The positivity conditions lead to non-trivial inequalities for these parameters. They are satisfied in free field theories, except in one case for dimensions close to two. Further restrictions on |ψ〉 are suggested which remove this problem. The inequalities which follow from considering the state formed by applying the energy momentum tensor to the vacuum are shown to imply that the coefficient of the topological term in the expectation value of the trace of the energy momentum tensor in an arbitrary curved space background is positive, in accord with calculations in free field theories.     

A possible role of gravitino condensates in superstring compactification

By restricting the energy to a region below the Planck mass and the string compactification scale, but above the scale of gauge interactions, it is shown that gravitino pair condensation may induce local supersymmetry breaking in the coupled supergravity-super-Yang-Mills effective theory originated from Green-Schwarz superstrings. The problem of cosmological constant generation is also considered and it is shown that it may actually vanish under certain assumptions on the fermion bilinears, without, however, the need of fine-tuning the parameters of the theory.     

Effective potential in N = 1, D = 4 supergravity coupled to the volkov-akulov field

The one-loop effective potential is calculated for the N = 1, D = 4 supergravity theory coupled to the Volkov-Akulov field. It is then shown that after an adjustment of some of the parameters, local supersymmetry is broken and as a consequence the gravitino acquires mass through a dynamical effect.     

On the Casimir energy for a massive quantum scalar field and the cosmological constant

We present a rigorous, regularization-independent local quantum field theoretic treatment of the Casimir effect for a quantum scalar field of mass μ≠0 which yields closed form expressions for the energy density and pressure. As an application we show that there exist special states of the quantum field in which the expectation value of the renormalized energy–momentum tensor is, for any fixed time, independent of the space coordinate and of the perfect fluid form g_μ,νρ with ρ>0, thus providing a concrete quantum field theoretic model of the cosmological constant. This ρ represents the energy density associated to a state consisting of the vacuum and a certain number of excitations of zero momentum, i.e., the constituents correspond to lowest energy and pressure p0.     

Spacetime supersymmetry breaking in heterotic string theory

A simple mechanism for spacetime supersymmetry breaking in the ten-dimensional heterotic string theory is proposed. We present a heterotic string model with a hidden two-dimensional sigma-model sector which can induce desirably small supersymmetry breaking, without upsetting the zero value of the cosmological constant, through a topological instanton effect due to an abelian gauge field on the string world sheet. We find that the consistency condition of the gravitino field equation is satisfied for some configurations even after supersymmetry breaking.     

Spontaneous breaking of supersymmetry and gauge invariance in supergravity

Using the new minimal auxiliary fields of N = 1 supergravity it is found possible to construct a model of local supersymmetry which spontaneously breaks both supersymmetry and gauge invariance. The status of the cosmological constant resulting from this breaking is discussed.     

Stability in gauged extended supergravity

Extended supergravity theories with gauged SO(N) internal symmetry have, for N ≥ 4, scalar field potentials which are unbounded below. Nevertheless, it is argued that the theories have ground states with anti-de Sitter background geometry which are stable against fluctuations which vanish sufficiently fast at spatial infinity. Stability is implied because the appropriate conserved energy functional is positive for such fluctuations. Anti-de Sitter space is not globally hyperbolic, but the boundary conditions required for positive energy are also shown to give free field theories with well-defined Cauchy problem. New information on the particle representations of OSp(1, 4) supersymmetry is presented as part of the argument. Supersymmetry requires boundary conditions for spin 0 fields such that only the improved stress tensor leads to a conserved energy functional. Although the stability arguments support the view that gauged supergravity theories are acceptable quantum field theories, the problem of a large cosmological term in the Ads phase of the theories is still unsolved.     

Anomaly-induced inflaton decay and gravitino-overproduction problem

We point out that the inflaton spontaneously decays into any gauge bosons and gauginos via the super-Weyl, Kähler and sigma-model anomalies in supergravity, once the inflaton acquires a non-vanishing vacuum expectation value. In particular, in the dynamical supersymmetry breaking scenarios, the inflaton necessarily decays into the supersymmetry breaking sector, if the inflaton mass is larger than the dynamical scale. This generically causes the overproduction of the gravitinos, which severely constrains the inflation models.     

Scale invariance and spontaneous symmetry breaking

Spontaneous breaking of gauge symmetries is studied in theories with nonlinearly realized scale invariance. The classically sliding vacuum expectation values are fixed through quantum corrections. The anomaly of the dilatation current determines the vacuum energy density as well as the dilaton mass. The coupling of gravity to matter is modified in such a way that the cosmological constant vanishes.     

Gauged N = 4 supergravities in five dimensions and their magnetovac backgrounds

Gauged N = 4 supergravity theories with Yang-Mills symmetry SU(2) × U(1) are constructed in five dimensions. As in four dimensions, the presence of a nonsimple gauge group leads to the existence of three distinct theories, depending (in five dimensions) on the values of the SU(2) and U(1) coupling constants. Two of the theories are distinguished by the relative sign of the coupling constants; one of these has a vacuum state exhibiting the full N = 4 anti-de Sitter supersymmetry SU(2,2|2), while the other has a scalar potential with no critical points. The third theory, in which the SU(2) coupling constant is taken to be zero, has vanishing scalar potential. This leads to vacua with spontaneously broken supersymmetry and zero cosmological constant, admitting compactification to four dimensions. All three theories possess “magnetovac” ground states with residual supersymmetry and hence presumably stable. Several of these may be interpreted as four-dimensional cosmological models.     

Properties of supersymmetry breaking via gravitino condensation

We study the implications of a recently proposed mechanism to break local supersymmetry through gravtino condensation. We find that gravitino condensates destabilize the Minkowski background and generate a large cosmological constant.