A Non-Perturbative Superpotential With E8E_8 Symmetry

We compute the non-perturbative superpotential in $F$-theory compactification to four dimensions on a complex three-fold $\P^1\times S$, where $S$ is a rational elliptic surface. In contrast to examples considered previously, the superpotential in this case has interesting modular properties; it is essentially an $E_8$ theta function.Comment: Additional references and clarifications. Latex, 10 page

NeXSPheRIO results on elliptic flow at RHIC and connection with thermalization

Elliptic flow at RHIC is computed event-by-event with NeXSPheRIO. Reasonable agreement with experimental results on $v_2(\eta)$ is obtained. Various effects are studied as well: reconstruction of impact parameter direction, freeze out temperature, equation of state (with or without crossover), emission mecanism.Comment: Contribution to the Proceedings of the Quark-Gluon Plasma Thermalization workshop. Content slightly increase

Super Quantum Mechanics in the Integral Form Formalism

We reformulate Super Quantum Mechanics in the context of integral forms. This framework allows to interpolate between different actions for the same theory, connected by different choices of Picture Changing Operators (PCO). In this way we retrieve component and superspace actions, and prove their equivalence. The PCO are closed integral forms, and can be interpreted as super Poincar\'e duals of bosonic submanifolds embedded into a supermanifold.. We use them to construct Lagrangians that are top integral forms, and therefore can be integrated on the whole supermanifold. The $D=1, ~N=1$ and the $D=1,~ N=2$ cases are studied, in a flat and in a curved supermanifold. In this formalism we also consider coupling with gauge fields, Hilbert space of quantum states and observables.Comment: 41 pages, no figures. Use birkjour.cls. Minor misprints, moved appendix A and B in the main text. Version to be published in Annales H. Poincar\'

The Geometry of Supermanifolds and New Supersymmetric Actions

We construct the Hodge dual for supermanifolds by means of the Grassmannian Fourier transform of superforms. In the case of supermanifolds it is known that the superforms are not sufficient to construct a consistent integration theory and that the integral forms are needed. They are distribution-like forms which can be integrated on supermanifolds as a top form can be integrated on a conventional manifold. In our construction of the Hodge dual of superforms they arise naturally. The compatibility between Hodge duality and supersymmetry is exploited and applied to several examples. We define the irreducible representations of supersymmetry in terms of integral and superforms in a new way which can be easily generalised to several models in different dimensions. The construction of supersymmetric actions based on the Hodge duality is presented and new supersymmetric actions with higher derivative terms are found. These terms are required by the invertibility of the Hodge operator.Comment: LateX2e, 51 pages. Corrected some further misprint

The formation of the primitive star SDSS J102915+172927: effect of the dust mass and the grain-size distribution

Understanding the formation of the extremely metal poor star SDSS-J102915+172927 is of fundamental importance to improve our knowledge on the transition between the first and second generation of stars in the Universe. In this paper, we perform three-dimensional cosmological hydrodynamical simulations of dust-enriched halos during the early stages of the collapse process including a detailed treatment of the dust physics. We employ the astrochemistry package \krome coupled with the hydrodynamical code \textsc{enzo} assuming grain size distributions produced by the explosion of core-collapse supernovae of 20 and 35 M$_\odot$ primordial stars which are suitable to reproduce the chemical pattern of the SDSS-J102915+172927 star. We find that the dust mass yield produced from Population III supernovae explosions is the most important factor which drives the thermal evolution and the dynamical properties of the halos. Hence, for the specific distributions relevant in this context, the composition, the dust optical properties, and the size-range have only minor effects on the results due to similar cooling functions. We also show that the critical dust mass to enable fragmentation provided by semi-analytical models should be revised, as we obtain values one order of magnitude larger. This determines the transition from disk fragmentation to a more filamentary fragmentation mode, and suggests that likely more than one single supernova event or efficient dust growth should be invoked to get such a high dust content.Comment: Accepted on Ap

Primordial star formation: relative impact of H2 three-body rates and initial conditions

Population III stars are the first stars in the Universe to form at z=20-30 out of a pure hydrogen and helium gas in minihalos of 10^5-10^6 M$_\odot$ . Cooling and fragmentation is thus regulated via molecular hydrogen. At densities above 10^8 cm$^{-3}$, the three-body H2 formation rates are particularly important for making the gas fully molecular. These rates were considered to be uncertain by at least a few orders of magnitude. We explore the impact of new accurate three-body H2 formation rates derived by Forrey (2013) for three different minihalos, and compare to the results obtained with three-body rates employed in previous studies. The calculations are performed with the cosmological hydrodynamics code ENZO (release 2.2) coupled with the chemistry package KROME (including a network for primordial chemistry), which was previously shown to be accurate in high resolution simulations. While the new rates can shift the point where the gas becomes fully molecular, leading to a different thermal evolution, there is no trivial trend in how this occurs. While one might naively expect the results to be inbetween the calculations based on Palla et al. (1983) and Abel et al. (2002), the behavior can be close to the former or the latter depending on the dark matter halo that is explored. We conclude that employing the correct three-body rates is about as equally important as the use of appropriate initial conditions, and that the resulting thermal evolution needs to be calculated for every halo individually.Comment: 10 pages, 9 figures, A&A, 561, A13 (2014