Pierre Binetruy

D term inflation

Abstract We show that inflation which is dominated by the D-term density avoids the ‘slow-roll’ problem of inflation in supergravity. Such an inflationary scenario can naturally emerge in theories with non-anomalous or anomalous U(1) gauge symmetry. In the latter case the scale of inflation is fixed by the Green-Schwarz mechanism of anomaly cancellation. The crucial point is that the (super) gravity-mediated curvature of all the scalar fields (and, in particular, of the inflaton), which in the standard F-dominated case is of the order of the Hubble parameter, is absent in the D-term inflation case. The curvature of moduli and of all other flat directions during such an inflation crucially depends on their gauge charges.

Yukawa textures with an anomalous horizontal abelian symmetry

The observed hierarchy of quark and lepton masses and mixings may be obtained by adding an abelian family symmetry to the Minimal Supersymmetric Model and coupling quarks and leptons to an electroweak singlet scalar field. In a large class of such models, this symmetry suffers from anomalies which must be compensated by the Green-Schwarz mechanism; this in turn fixes the electroweak mixing angle to be sin2θW = 38 at the string scale, without any assumed GUT structure. The analysis is extended to two distinct generalizations of the Standard Model: neutrino masses and mixings and R-parity violating interactions.

One Loop Soft Supersymmetry Breaking Terms in Superstring Effective Theories

We perform a systematic analysis of soft supersymmetry breaking terms at the one loop level in a large class of string effective field theories. This includes the so-called anomaly mediated contributions. We illustrate our results for several classes of orbifold models. In particular, we discuss a class of models where soft supersymmetry breaking terms are determined by quasi model independent anomaly mediated contributions, with possibly non-vanishing scalar masses at the one loop level. We show that the latter contribution depends on the detailed prescription of the regularization process which is assumed to represent the Planck scale physics of the underlying fundamental theory. The usual anomaly mediation case with vanishing scalar masses at one loop is not found to be generic. However gaugino masses and A-terms always vanish at tree level if supersymmetry breaking is moduli dominated with the moduli stabilized at self- dual points, whereas the vanishing of the B-term depends on the origin of the � -term in the underlying theory. We also discuss the supersymmetric spectrum of O-I and O-II models, as well as a model of gaugino condensation. For reference, explicit spectra corresponding to a Higgs mass of 114 GeV are given. Finally, we address general strategies for distinguishing among these models.

DILATON STABILIZATION IN THE CONTEXT OF DYNAMICAL SUPERSYMMETRY BREAKING THROUGH GAUGINO CONDENSATION

Abstract We study gaugino condensation in the context of superstring effective theories using the linear multiplet formulation for the dilaton superfield. Including non-perturbative corrections to the Kahler potential for the dilaton may naturally achieve dilaton stabilization, with supersymmetry breaking and gaugino condensation; these three issues are interrelated in a very simple way. In a toy model with a single static condensate, a dilaton vev is found within a phenomenologically interesting range. The effective theory differs significantly from condensate models studied previously in the chiral formulation.

A modular invariant formulation of gaugino condensation with a positive semi-definite potential

Abstract We reinterpret earlier results on gaugino condensation in supergravity by incorporating renormalization effects into the Kahler potential, rather than the superpotential, for the lightest chiral supermultiplet of the confined Yang-Mills sector. The two approaches are identical to leading in the loop expansion parameter b 0 , but differ at order b 2 0 . The present approach, which is supported by known effects of renormalization in supersymmetry and supergravity, allows us to maintain an effective supergravity theory of the no-scale type. We extend these results to the cases of three moduli and of more than one gaugino condensate.

Supersymmetry breaking in string models and a source of hierarchy (I)

Abstract In a certain class of superstring models, supersymmetry is broken in a hidden sector but remains globally conserved in the observable sector of quarks and gluons. We recently identified the symmetry responsible for this property, a noncompact symmetry closely connected with space-time duality. This symmetry is broken by chiral and conformal anomalies, which provides the source of supersymmetry breaking in the observable sector and a possibly large hierarchy of scales. We give here details on our analysis, focussing on the identification of the anomalous terms which provide a source of breaking.

Relating incomplete data and incomplete theory

Assuming string theorists will not soon provide a compelling case for the primary theory underlying particle physics, the field will proceed as it has historically: with data stimulating and testing ideas. Ideally the soft supersymmetry breaking Lagrangian will be measured and its patterns will point to the underlying theory. But there are two new problems. First a matter of principle: the theory may be simplest at distance scales and in numbers of dimensions where direct experiments are not possible. Second a practical problem: in the foreseeable future (with mainly hadron collider data) too few observables can be measured to lead to direct connections between experiment and theory. In this paper we discuss and study these issues and consider ways to circumvent the problems, studying models to test methods. We propose a semiquantitative method for focusing and sharpening thinking when trying to relate incomplete data to incomplete theory, as will probably be necessary.

An Exact Classical Symmetry of Effective Field Theories From Superstrings and an Anomalous Source of Observable Supersymmetry Breaking

Abstract The effective field theory suggested by the simplest superstring compactification has an exact classical nonlinear symmetry group that is likely to be present in a large class of realistic models obtained from superstrings. Certain group elements are closely related to duality transformations R → R −1 on the radius of compactification R . The symmetry is broken by chiral and conformal anomalies, which may provide the source of supersymmetry breaking in the observable sector. Modelling the effects of the anomalies, using an effective composite supermultiplet for the strongly interacting hidden SUSY Yang-Mills sector, we find that a gaugino mass is generated with an order of magnitude that is very plausibly compatible with the requirements of phenomenology.

S-duality constraints on effective potentials for gaugino condensation

We clarify the role of approximate S-duality in effective supergravity theories that are the low energy limits of string theories, and show how this partial symmetry may be used to constrain effective lagrangians for gaugino condensation.

Twenty-five questions for string theorists

In an effort to promote communication between the formal and phenomenological branches of the high-energy theory community, we provide a description of some important issues in supersymmetric and string phenomenology. We describe each within the context of string constructions, illustrating them with specific examples where applicable. Each topic culminates in a set of questions that we believe are amenable to direct consideration by string theorists, and whose answers we think could help connect string theory and phenomenology.