Higgs inflation: consistency and generalisations

We analyse the self-consistency of inflation in the Standard Model, where the Higgs field has a large non-minimal coupling to gravity. We determine the domain of energies in which this model represents a valid effective field theory as a function of the background Higgs field. This domain is bounded above by the cutoff scale which is found to be higher than the relevant dynamical scales throughout the whole history of the Universe, including the inflationary epoch and reheating. We present a systematic scheme to take into account quantum loop corrections to the inflationary calculations within the framework of effective field theory. We discuss the additional assumptions that must be satisfied by the ultra-violet completion of the theory to allow connection between the parameters of the inflationary effective theory and those describing the low-energy physics relevant for the collider experiments. A class of generalisations of inflationary theories with similar properties is constructed.Comment: 25 pages, 1 figur

Hyperon production asymmetries in 500 GeV/c pion nucleus interactions

We present a preliminary study from Fermilab experiment E791 of Lambda^0 / Lambda^0 bar, Xi^- / Xi^+ and Omega^- /Omega^+ production asymmetries from pi^- nucleus interactions at 500 Gev/c. The production asymmetries for these particles are studied as a function of x_F and pt^2. We observed an asymmetry in the target fragmentation region for Lambda^0's larger than that for Xi's, suggesting diquark effects. The asymmetry for Omega's is significatively smaller than for the other two hyperons consistent with the fact that Omega's do not share valence quarks with either the pion or the target particle. In the beam fragmentation region, the asymmetry tends to 0.1 for both Lambda^0's and Xi's. The asymmetries vs pt^2 are approximately constant for the three strange baryons under study.Comment: Typos correcte

The Charm of the Proton and the Λc+\Lambda _c^{+} Production

We propose a two component model for charmed baryon production in $pp$ collisions consisting of the conventional parton fusion mechanism and fragmentation plus quarks recombination in which a $ud$ valence diquark from the proton recombines with a $c$-sea quark to produce a $\Lambda_c^+$. Our two-component model is compared with the intrinsic charm two-component model and experimental data.Comment: 6 pages, LaTex, 2 figures included, aipproc.sty included. Talk presented at Simposio Latino Americano de Fisica de Altas Energias, Merida, Mexico, November 199

The Λ0\Lambda_0 Polarization and the Recombination Mechanism

We use the recombination and the Thomas Precession Model to obtain a prediction for the $\Lambda _0$ polarization in the $p+p \to \Lambda_0+X$ reaction. We study the effect of the recombination function on the $\Lambda_0$ polarization.Comment: 4 pages, LaTex, 1 figures included, aipproc.sty included. Talk presented at Simposio Latino Americano de Fisica de Altas Energias, Merida, Mexico, November 199

Asymmetry studies in Lambda 0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+ production

We present a study on hyperon/anti-hyperon production asymmetries in the framework of the recombination model. The production asymmetries for Lambda 0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+ are studied as a function of x_F. Predictions of the model are compared to preliminary data on hyperon/anti-hyperon production asymmetries in 500 GeV/c pi- p interactions from the Fermilab E791 experiment. The model predicts a growing asymmetry with the number of valence quarks shared by the target and the produced hyperons in the x_F < 0 region. In the positive x_F region, the model predicts constant asymmetries for Lambda 0/Lambda 0-bar and Omega-/Omega+ production and a growing asymmetry with x_F for Xi-/Xi+. We found a qualitatively good agreement between the model predictions and data, showing that recombination is a competitive mechanism in the hadronization process.Comment: One reference correcte

Heisenberg-limited eavesdropping on the continuous-variable quantum cryptographic protocol with no basis switching is impossible

The Gaussian quantum key distribution protocol based on coherent states and heterodyne detection [Phys. Rev. Lett. 93, 170504 (2004)] has the advantage that no active random basis switching is needed on the receiver's side. Its security is, however, not very satisfyingly understood today because the bounds on the secret key rate that have been derived from Heisenberg relations are not attained by any known scheme. Here, we address the problem of the optimal Gaussian individual attack against this protocol, and derive tight upper bounds on the information accessible to an eavesdropper. The optical scheme achieving this bound is also exhibited, which concludes the security analysis of this protocol.Comment: 10 pages, 6 figure

Introduction to 2D and 3D tomographic methods based on straight line propagation: X-ray, emission and ultrasonic tomography

This paper presents the basic principles of computerized tomography (CT), and its evolution towards three dimensional (3D ) imaging . Since the modelisation of CT reconstruction relies on the Radon transform, its definition and major properties are firs t recalled. After a brief summary on conventional 2D methods, we present the imaging principles for two modalities appropriate d to this modelisation : X-Ray and emission tomography. We describe the evolution of the instrumentation for these two techniques , and emphasize the approximations introduced by a modelisation using the Radon transform taking into account the physics o f the problem . We also describe the principles of ultrasonic tomography systems, and their major differences with the two previou s technics . At last, we formulate the general problematic of 3D image reconstruction from 2D projections . We consider four classe s of reconstruction methods corresponding to the classification chosen for the synthetic presentation of methods, accompanying thi s paper.Cet article présente les principes de base de la tomographie assistée par ordinateur, ainsi que son évolution vers le tridimen - sionnel (3D) . La modélisation mathématique du problème de reconstruction tomographique s'appuie sur la transformatio n de Radon dont la définition et quelques propriétés sont rappelées . Après un bref résumé sur les méthodes conventionnelle s 2D, nous présentons les principes physiques pour deux modalités bien appropriées à cette modélisation : la tomographie de transmission par rayons X et la tomographie d'émission par rayons ,y . Nous nous attachons à décrire l'évolution de l'instru - mentation dans ces deux techniques, ainsi que les approximations introduites par une modélisation de type Transformée de Radon par rapport à la physique du problème . Nous décrivons également les principes des systèmes de tomographie ultrasonore, et leurs différences majeures par rapport aux deux techniques précédentes . Enfin, nous reprenons la problématiqu e générale des méthodes de reconstruction 3D à partir de projections 2D . Nous faisons apparaître quatre classes correspondan t au découpage choisi pour la présentation des fiches techniques accompagnant cet article