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Pierre Binetruy

Publications and source records attributed to Pierre Binetruy.

26 records · Page 2Linked to original sources
arXiv2000

Brane cosmological evolution in a bulk with cosmological constant

We consider the cosmology of a ``3-brane universe'' in a five dimensional (bulk) space-time with a cosmological constant. We show that Einstein's equations admit a first integral, analogous to the first Friedmann equation, which governs the evolution of the metric in the brane, whatever the time evolution of the metric along the fifth dimension. We thus obtain the cosmological evolution in the brane for any equation of state describing the matter in the brane, without needing the dependence of the metric on the fifth dimension. In the particular case $p = w ρ$, $(w = constant)$, we give explicit expressions for the time evolution of the brane scale factor, which show that standard cosmological evolution can be obtained (after an early non conventional phase) in a scenario à la Randall and Sundrum, where a brane tension compensates the bulk cosmological constant. We also show that a tiny deviation from exact compensation leads to an effective cosmological constant at late time. Moreover, when the metric along the fifth dimension is static, we are able to extend the solution found on the brane to the whole spacetime.

hep-th↗
arXiv1999

Non-conventional cosmology from a brane-universe

We consider ``brane-universes'', where matter is confined to four-dimensional hypersurfaces (three-branes) whereas one extra compact dimension is felt by gravity only. We show that the cosmology of such branes is definitely different from standard cosmology and identify the reasons behind this difference. We give a new class of exact solutions with a constant five-dimensional radius and cosmologically evolving brane. We discuss various consequences.

hep-th↗
arXiv1998

Models of dynamical supersymmetry breaking and quintessence

We study several models of relevance for the dynamical breaking of supersymmetry which could provide a scalar component with equation of state $p=wρ$, $-1<w<0$. Such models would provide a natural explanation for recent data on the cosmological parameters.

hep-ph↗
arXiv1997

Supersymmetry breaking and weakly vs. strongly coupled string theory

In the context of the field theory limit of superstrings, we consider an almost realistic model of supersymmetry breaking by gaugino condensation which includes, through nonperturbative corrections to the Kähler potential, dilaton stabilization at a value compatible with a weak coupling regime. Invariance under modular transformations is ensured through a Green-Schwarz term and string threshold corrections, which lead to moduli stabilization at the self-dual point. We are thus in a position to discuss several issues of physical relevance: gravitino, dilaton and moduli masses, axion, soft supersymmetry breaking parameters and gauge coupling unification.

hep-th↗
arXiv1996

Modular Invariant Formulation of Multi-Gaugino and Matter Condensation

Using the linear multiplet formulation for the dilaton superfield, we construct an effective lagrangian for hidden-sector gaugino condensation in string effective field theories with arbitrary gauge groups and matter. Nonperturbative string corrections to the Kähler potential are invoked to stabilize the dilaton at a supersymmetry breaking minimum of the potential. When the cosmological constant is tuned to zero the moduli are stabilized at their self-dual points, and the vev's of their F-component superpartners vanish. Numerical analyses of one- and two-condensate examples with massless chiral matter show considerable enhancement of the gauge hierarchy with respect to the E_8 case. The nonperturbative string effects required for dilaton stabilization may have implications for gauge coupling unification. As a comparison, we also consider a parallel approach based on the commonly used chiral formulation.

hep-th↗
arXiv1996

D-Term Inflation

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.

hep-ph↗
arXiv1994

Yukawa Textures and Anomalies

We augment the Minimal Supersymmetric Standard Model with a gauged family-dependent $U(1)$ to reproduce Yukawa textures compatible with experiment. In the simplest model with one extra chiral electroweak singlet field, acceptable textures require this $U(1)$ to be anomalous. The cancellation of its anomalies by a generic Green-Schwarz mechanism requires $\sin^2θ_w=3/8$ at the string scale, suggesting a superstring origin for the standard model.

hep-ph↗