Particle Production near an AdS Crunch

We numerically study the dual field theory evolution of five-dimensional asymptotically anti-de Sitter solutions of supergravity that develop cosmological singularities. The dual theory is an unstable deformation of the N = 4 gauge theory on R $\times$ S3, and the big crunch singularity in the bulk occurs when a boundary scalar field runs to infinity. Consistent quantum evolution requires one imposes boundary conditions at infinity. Modeling these by a steep regularization of the scalar potential, we find that when an initially nearly homogeneous wavepacket rolls down the potential, most of the potential energy of the initial configuration is converted into gradient energy during the first oscillation of the field. This indicates there is no transition from a big crunch to a big bang in the bulk for dual boundary conditions of this kind.Comment: 20 pages, 6 figure

Black hole production in tachyonic preheating

We present fully non-linear simulations of a self-interacting scalar field in the early universe undergoing tachyonic preheating. We find that density perturbations on sub-horizon scales which are amplified by tachyonic instability maintain long range correlations even during the succeeding parametric resonance, in contrast to the standard models of preheating dominated by parametric resonance. As a result the final spectrum exhibits memory and is not universal in shape. We find that throughout the subsequent era of parametric resonance the equation of state of the universe is almost dust-like, hence the Jeans wavelength is much smaller than the horizon scale. If our 2D simulations are accurate reflections of the situation in 3D, then there are wide regions of parameter space ruled out by over-production of black holes. It is likely however that realistic parameter values, consistent with COBE/WMAP normalisation, are safetly outside this black hole over-production region.Comment: 6pages, 7figures, figures correcte

Asymmetric Kelvin-Helmholtz Instability at Jupiter's Magnetopause Boundary: Implications for Corotation-Dominated Systems

©2018. American Geophysical Union. The multifluid Lyon-Fedder-Mobarry (MFLFM) global magnetosphere model is used to study the interactions between solar wind and rapidly rotating, internally driven Jupiter magnetosphere. The MFLFM model is the first global simulation of Jupiter magnetosphere that captures the Kelvin-Helmholtz instability (KHI) in the critically important subsolar region. Observations indicate that Kelvin-Helmholtz vortices are found predominantly in the dusk sector. Our simulations explain that this distribution is driven by the growth of KHI modes in the prenoon and subsolar region (e.g., > 10 local time) that are advected by magnetospheric flows to the dusk sector. The period of density fluctuations at the dusk terminator flank (18 magnetic local time, MLT) is roughly 1.4 h compared with 7.2 h at the dawn flank (6 MLT). Although the simulations are only performed using parameters of the Jupiter's magnetosphere, the results may also have implications for solar wind-magnetosphere interactions at other corotation-dominated systems such as Saturn. For instance, the simulated average azimuthal speed of magnetosheath flows exhibit significant dawn-dusk asymmetry, consistent with recent observations at Saturn. The results are particularly relevant for the ongoing Juno mission and the analysis of dawnside magnetopause boundary crossings for other planetary missions.Link_to_subscribed_fulltex

Flux transfer event observation at Saturn's dayside magnetopause by the Cassini spacecraft

We present the first observation of a flux rope at Saturn's dayside magnetopause. This is an important result because it shows that the Saturnian magnetopause is conducive to multiple X-line reconnection and flux rope generation. Minimum variance analysis shows that the magnetic signature is consistent with a flux rope. The magnetic observations were well fitted to a constant-α force-free flux rope model. The radius and magnetic flux content of the rope are estimated to be 4600–8300 km and 0.2–0.8 MWb, respectively. Cassini also observed five traveling compression regions (remote signatures of flux ropes), in the adjacent magnetosphere. The magnetic flux content is compared to other estimates of flux opening via reconnection at Saturn

Preheating in New Inflation

During the last ten years a detailed investigation of preheating was performed for chaotic inflation and for hybrid inflation. However, nonperturbative effects during reheating in the new inflation scenario remained practically unexplored. We do a full analysis of preheating in new inflation, using a combination of analytical and numerical methods. We find that the decay of the homogeneous component of the inflaton field and the resulting process of spontaneous symmetry breaking in the simplest models of new inflation usually occurs almost instantly: for the new inflation on the GUT scale it takes only about 5 oscillations of the field distribution. The decay of the homogeneous inflaton field is so efficient because of a combined effect of tachyonic preheating and parametric resonance. At that stage, the homogeneous oscillating inflaton field decays into a collection of waves of the inflaton field, with a typical wavelength of the order of the inverse inflaton mass. This stage usually is followed by a long stage of decay of the inflaton field into other particles, which can be described by the perturbative approach to reheating after inflation. The resulting reheating temperature typically is rather low