Reheating and Supersymmetric Flat-Direction Baryogenesis

We re-examine Affleck-Dine baryo/leptogenesis from the oscillation of condensates along flat directions of the supersymmetric standard model, which attained large vevs at the end of inflationary epoque. The key observation is that superpotential interactions couple the flat directions to other fields, which acquire masses induced by the flat-direction vev that may be sufficiently small for them to be kinematically accessible to inflaton decay. The resulting plasma of inflaton decay products then may act on the flat directions via these superpotential Yukawa couplings, inducing thermal masses and supersymmetry-breaking A terms. In such cases the flat directions start their oscillations at an earlier time than usually estimated. The oscillations are also terminated earlier, due to evaporation of the flat direction condensate produced by its interaction with the plasma of inflaton decay products. In these cases we find that estimates for the resulting baryon/lepton asymmetry of the universe are substantially altered. We identify scenarios for the Yukawa couplings to the flat directions, and the order and mass scale of higher-dimensional superpotential interactions that set the initial flat direction vev, that might lead to acceptable baryo/leptogenesis.Comment: 26 pages, 9 Table

New approach to nonlinear electrodynamics: dualities as symmetries of interaction

We elaborate on the duality-symmetric nonlinear electrodynamics in a new formulation with auxiliary tensor fields. The Maxwell field strength appears only in bilinear terms of the corresponding generic Lagrangian, while the self-interaction is presented by a function E depending on the auxiliary fields. Two types of dualities inherent in the nonlinear electrodynamics models admit a simple off-shell characterization in terms of this function. In the standard formulation, the continuous U(1) duality symmetry is nonlinearly realized on the Maxwell field strength. In the new setting, the same symmetry acts as linear U(1) transformations of the auxiliary field variables. The nonlinear U(1) duality condition proves to be equivalent to the linear U(1) invariance of the self-interaction E. The discrete self-duality (or self-duality by Legendre transformation) amounts to a weaker reflection symmetry of E. For a class of duality- symmetric Lagrangians we introduce an alternative representation with the auxiliary scalar field and find new explicit examples of such systems.Comment: Latex file, 21 page

Increased Proton Energies - Above the ~ 60 MeV Empirical Barrier, from High-Contrast High-Intensity Short-Pulse Laser-Interactions with Micro-Cone Targets

Ultra-high intensity lasers enable the investigation of extreme states of matter and the study of high energy density physics in the laboratory, as well as the creation of various intense radiation sources, i.e. electrons, X-rays, and ions. Of particular interest to this dissertation is the production of ion beams from solid targets. These ion beams are directly linked to the hot-electron production and transport inside the solid target (as simple as a metal or CH foil), which requires that electron heating and transport must be well understood in order to increase ion energies and laser-ion conversion efficiencies. Maximizing the energy and/or the conversion efficiency of these ion beams is of considerable interest for many applications, in particular radiation oncology, and inertial confinement fusion with fast ignition. Several approaches have been proposed to maximize the energy and/or the conversion efficiency of the ion beams: instead of using regular size flat-foil targets (i.e. ~ 10 µm thickness, ~ 2x2 mm^2 lateral dimensions), one can use ultrathin targets (thickness of the order of the µm or 100s of nm), very small targets, a.k.a. reduced-mass targets (RMTs) (i.e. lateral dimensions of ~ 100x100 µm^2), or structured targets (e.g. conical-shape targets). These more elaborate targets can increase the hot-electron temperature and/or the hot-electron density. In experiments performed in 2006 on the Trident laser at ~ 20 J, reported in [1], we found that microstructured flat-top cone (FTC) targets, made from Au, yielded an increase in proton energy from 19 MeV to > 30 MeV, and in laser-proton conversion efficiencies from 0.5 % to 2.5 %, as compared to flat-foil targets. These results were postulated to stem from improved laser guiding toward the cone tip, which would lead to higher laser intensities, increased laser absorption and hotter electrons. Improved electron production and transport were also hypothesized to lead to an increase in the hot-electron density and hot-electron temperature at the flat-top. Also postulated was the fact that a longer electron confinement time at the flat-top could lead to RMT-like effects such as resistive/confining edge fields and enhanced target (or flat-top) charge up. We also observed experimentally that, when the laser was misaligned and could not reach the cone tip, or from simulations that, when it was absorbed farther from the flat-top due to an excess in preplasma, the proton acceleration was neither as efficient nor as energetic.After these very promising 2006 results, we endeavored to determine whether this enhancement in proton energy and conversion efficiency would scale for higher laser energies. I participated in the design and the execution of the subsequent experiment, which was performed in 2008, after the Trident laser energy had been upgraded from ~ 20 J to ~ 80 J. This time, surprisingly, we found that the proton energies were in fact lower when FTC targets were used, as opposed to flat-foil targets [2]. To diagnose the laser absorption zone inside the FTC, Cu targets were used (instead of Au) for the purpose of Cu Ka 2-D imaging. I had taken part in an experiment on the LULI laser system earlier in 2008 to learn about Cu Ka imaging techniques; in this experiment, it was observed that, when a portion of the hot-electron population deposits its energy in the laser absorption zone, the emission of Cu Ka X-rays is a direct indication of where the electrons are created, and thus of how much preplasma is filling the cone neck [3]; preplasma is plasma from wall blow-off due to the low level of laser light entering the cone before the main high-intensity pulse, called laser "prepulse". Combining and correlating Cu Ka 2-D imaging with proton acceleration was one of my main goals for this dissertation. At an intrinsic 10^-8 laser contrast, unlike in the 20 J (and ~ 10^19 W/cm^2) case, at 80 J (and ~ 2x10^20 W/cm^2), after the Trident energy enhancement, as well as the addition of a deformable mirror resulting in a spot size decrease from ~ 14 µm down to ~ 7 µm FWHM (with 47 % of the energy in the spot), the amount of plasma prefill (preplasma) prevented the majority of the laser from being efficiently absorbed closer to the cone flat-top or tip [3,4]. The hot-electron population was thus generated away from the flat-top, as indicated by the Cu Ka emission from the cone walls [2], which negatively impacted the proton acceleration, especially in the case of thin FTC necks [1], as the electrons were also not efficiently transported to the flat-top to generate the sheath necessary for ion production. I was also responsible for the electron spectrometer diagnostic; electron spectroscopy confirmed that the temperature of the escaping electrons correlates in a linear fashion with proton energy. Because of the preplasma issues encountered in 2008 due to an insufficient laser contrast (10^-8), I proposed and was the principal investigator of the most recent experiment (2009), which was performed on Trident at ~ 80 J using an enhanced contrast, i.e. this time > 10^-10. In this case, the proton energies were enhanced to 67.5 MeV [5] from 50 MeV when using FTC Cu targets as opposed to flat-foil targets. These results set a new record in laser-accelerated protons. The previous petawatt laser record was 58 MeV with ~ 400 J [6]. Electron spectroscopy in the enhanced contrast case shows an even better correlation with proton energy, due to a cleaner interaction caused by a lower preplasma level. Besides diagnosing the laser alignment or misalignment, I show in this dissertation via Cu Ka imaging, that not only is it crucial to obtain laser absorption at the tip (note that tip heating is dependent on laser contrast and laser intensity [3]), but it is even more important to find the optimum balance [5] between the amount of cone wall emission (CWE) versus top emission (TE) of Cu Ka X-rays. Interestingly, at enhanced contrast, the best results for proton acceleration are obtained when the target-laser interaction is asymmetric: i.e. when the laser interacts with the cone-tip and one sidewall more so than the opposing side. These experimental results directly led to simulations of these asymmetric interactions using a particle-in-cell (PIC) code capable of simulating ultra-intense laser-matter interactions. These simulations results significantly broadened our understanding of this interaction, and explain why the best performing target has a very large neck (i.e. 160 µm), implying that laser light guiding resulting from the cone geometry is not essential, but rather that the grazing of the laser light on as much cone wall surface area as possible (increasing the area where the laser can interact with the wall with a slight angle) is the reason for the observed proton energy enhancement. The knowledge obtained from these series of experiments, supported by the numerical simulations, will help us understand the fundamental laser-cone interaction, and develop new, more efficient targets, hopefully yielding even higher proton energy. __________________________________________________[1] K. A. Flippo, E. d'Humières, S. A. Gaillard, J. Rassuchine, D. C. Gautier, M. Schollmeier, F. Nürnberg, J. L. Kline, J. Adams, B. Albright, M. Bakeman, K. Harres, R. P. Johnson, G. Korgan, S. Letzring, S. Malekos, N. Renard-Le Galloudec, Y. Sentoku, T. Shimada, M. Roth, T. E. Cowan, J. C. Fernández, and B. M. Hegelich, Increased Efficiency of Short-Pulse Laser Generated Proton Beams from Novel Flat-Top Cone Targets, Physics of Plasmas (Invited) 15, 5 (2008).[2] S. A. Gaillard, K. A. Flippo, M. E. Lowenstern, J. E. Mucino, J. M. Rassuchine, D. C. Gautier, J. Workman, and T. E. Cowan, Proton acceleration from ultra high-intensity short-pulse laser-matter interactions with Cu micro-cone targets at the intrinsic ~10-8 contrast, submitted to Journal of Physics Conference Series (JPCS) (2009).[3] J. Rassuchine, E. d'Humières, S. D. Baton, P. Guillou, M. Koenig, M. Chahid, F. Pérez, J. Fuchs, P. Audebert, R. Kodama, M. Nakatsutsumi, N. Ozaki, D. Batani, A. Morace, R. Redaelli, L. Grémillet, C. Rousseaux, F. Dorchies, C. Fourment, J. J. Santos, J. Adams, G. Korgan, S. Malekos, S. B. Hansen, R. Shepherd, K. Flippo, S. Gaillard, Y. Sentoku, and T. E. Cowan, Enhanced hot electron localization and heating in high-contrast ultra-intense laser irradiation of sharp micro-cone targets, Physical Review E 79, 0364408 (2009).[4] S. D. Baton, M. Koenig, J. Fuchs, A. Benuzzi-Mounaix, P. Guillou, B. Loupias, T. Vinci, L. Grémillet, C. Rousseaux, M. Drouin, E. Lefebvre, F. Dorchies, C. Fourment, J. J. Santos, D. Batani, A. Morace, R. Redaelli, M. Nakatsutsumi, R. Kodama, A. Nishida, N. Ozaki, T. Norimatsu, Y. Aglitskiy, S. Atzeni, and A. Schiavi, Inhibition of fast electron energy deposition due to preplasma filling of cone-attached targets, Physics of Plasmas 15, 042706 (2008).[5] S. A. Gaillard, T. Kluge, K. A. Flippo, B. Gall, T. Lockard, M. Schollmeier, M. Geissel, D. T. Offermann, J. M. Rassuchine, D. C. Gautier, E. d'Humières, M. Bussmann, Y. Sentoku, and T. E. Cowan, Increased proton energies up to 67.5 MeV from high-contrast high-intensity short-pulse laser-interactions with micro-cone targets, in preparation (2010).[6] (a) R. Snavely, M. Key, S. Hatchett, T. Cowan, M. Roth, T. Phillips, M. Stoyer, E. Henry, T. Sangser, M. Signh, S. Wilks, A. Mackinnon, A. Offenberger, D. Pennington, K. Yasuike, A. Langdon, B. Lasinski, J. Johnson, M. Perry, and E. Campbell, Intense high-energy proton beams from petawatt-laser irradiation of solids, Physical Review Letters 85, 2945 (2000).(b) S. P. Hatchett, C. G. Brown, T. E. Cowan, E. A. Henry, J. S. Johnson, M. H. Key, J. A. Koch, A. B. Langdon, B. F. Lasinski, R. W. Lee, A. J. Mackinnon, D. M. Pennington, M. D. Perry, T. W. Phillips, M. Roth, T. C. Sangster, M. S. Singh, R. A. Snavely, M. A. Stoyer, S. C. Wilks, and K. Yasuike, Electron, photon, and ion beams from the relativistic interaction of petawatt laser pulses with solid targets, Physics of Plasmas 7, 2076 (2000)

Dynamiques familiales

L'examen de l'évolution des modèles familiaux en France et en Suède fait ressortir de nombreuses tendances parallèles : accroissement du taux de divorce, baisse des taux de nuptialité et de fécondité, réduction de la taille moyenne des familles, augmentation du nombre de familles monoparentales, diversité des familles recomposées, etc. Les auteurs s'attachent cependant à marquer à quel point le contexte historique et idéologique de cette évolution est très différent d'un pays à l'autre. Tandis que les nouveaux modèles conjugaux se diffusent rapidement en Suède sans y susciter de réactions de rejet, une certaine idéologie française prône un idéal de stabilité conjugale et réclame une politique ouvertement nataliste. La contraception et l'avortement apparaissent naturels à la population suédoise quand ils font toujours l'objet de débats passionnés en France. L'attitude envers l'enfant est très différente entre les deux pays. Pourtant dans l'un et l'autre cas l'évolution des liens familiaux, quoiqu'elle présente un aspect encore expérimental, semble suffisamment radicale pour obliger bientôt à repenser la nature du lien social en général. La procréation artificielle, la confrontation de logiques familiales différentes à travers l'immigration peuvent aussi, dans les années qui viennent, infléchir le sens des dynamiques familiales. (Résumé d'auteur

Three-way electrical gating characteristics of metallic Y-junction carbon nanotubes

Y-junction based carbon nanotube (CNT) transistors exhibit interesting switching behaviors, and have the structural advantage that the electrical gate for current modulation can be formed by any of the three constituent branches. In this letter, we report on the gating characteristics of metallic Y-CNT morphologies. By measuring the output conductance and transconductance we conclude that the efficiency and gain depend on the branch diameter and is electric field controlled. Based on these principles, we propose a design for a Y-junction based CNT switching device, with tunable electrical properties

One-loop Regularization of Supergravity II: The Dilaton and the Superfield Formulation

The on-shell regularization of the one-loop divergences of supergravity theories is generalized to include a dilaton of the type occurring in effective field theories derived from superstring theory, and the superfield structure of the one-loop corrections is given. Field theory anomalies and quantum contributions to soft supersymmetry breaking are discussed. The latter are sensitive to the precise choice of couplings that generate Pauli-Villars masses, which in turn reflect the details of the underlying theory above the scale of the effective cut-off. With a view to the implementation the Green-Schwarz and other mechanisms for canceling field theory anomalies under a U(1) gauge transformation and under the T-duality group of modular transformations, we show that the K\"ahler potential renormalization for the untwisted sector of orbifold compactification can be made invariant under these groups.Comment: 46 pages, full postscript also available from http://phyweb.lbl.gov/theorygroup/papers/43259.p

D-Meson Mixing in Broken SU(3)

A fit of amplitudes to the experimental branching ratios to two mesons is used to construct a new estimate of neutral $D$ mixing which includes $SU(3)$ breaking. The result is dominated by the experimental uncertainties. This suggests that the charm sector may not be as sensitive to new physics as previously thought and that long-distance calculations may not be useful.Comment: 12 pages, LaTeX, no figure

On the Interacting Chiral Gauge Field Theory in D=6 and the Off-Shell Equivalence of Dual Born-Infeld-Like Actions

A canonical action describing the interaction of chiral gauge fields in D=6 Minkowski space-time is constructed. In a particular partial gauge fixing it reduces to the action found by Perry and Schwarz. The additional gauge symmetries are used to show the off-shell equivalence of the dimensional reduction to D=5 Minkowski space-time of the chiral gauge field canonical action and the Born-Infeld canonical action describing an interacting D=5 Abelian vector field. Its extension to improve the on-shell equivalence arguments of dual D-brane actions to off-shell ones is discussed.Comment: 18 page

Gaugino Condensation with S-Duality and Field-Theoretical Threshold Corrections

We study gaugino condensation in the presence of an intermediate mass scale in the hidden sector. S-duality is imposed as an approximate symmetry of the effective supergravity theory. Furthermore, we include in the K\"ahler potential the renormalization of the gauge coupling and the one-loop threshold corrections at the intermediate scale. It is shown that confinement is indeed achieved. Furthermore, a new running behaviour of the dilaton arises which we attribute to S-duality. We also discuss the effects of the intermediate scale, and possible phenomenological implications of this model.Comment: 19 pages, LaTeX, 3 postscript figures include