Large Shell Model Calculations for Calcium Isotopes: Spectral Statistics and Chaos

We perform large shell model calculations for Calcium isotopes in the full fp shell by using the realistic Kuo-Brown interaction. The Calcium isotopes are especially interesting because the nearest-neighbour spacing distribution P(s) of low-lying energy levels shows significant deviations from the predictions of the Gaussian Orthogonal Ensemble of random--matrix theory. This contrasts with other neighbouring nuclei which show fully chaotic spectral distributions. We study the chaotic behaviour as a function of the excitation energy. In addition, a clear signature of chaos suppression is obtained when the single-particle spacings are increased. In our opinion the relatively weak strength of the neutron-neutron interaction is unable to destroy the regular single-particle mean-field motion completely. In the neighbouring nuclei with both protons and neutrons in valence orbits, on the other hand, the stronger proton-neutron interaction would appear to be sufficient to destroy the regular mean-field motion.Comment: Latex, 7 pages, 2 postscript figures, to be published in the Proceedings 'Highlights of Modern Nuclear Structure', S. Agata sui due Golfi (italy), Ed. A. Covello (World Scientific

Spectral Statistics in Large Shell Model Calculations

The spectral statistics of low--lying states of $fp$ shell nuclei are studied by performing large shell--model calculations with a realistic nuclear interaction. For $Ca$ isotopes, we find deviations from the predictions of the random--matrix theory which suggest that some spherical nuclei are not as chaotic in nature as the conventional view assumes.Comment: 9 pages, LaTex, 3 figures available upon request, to appear in Proceedings of the V International Spring Seminar on Nuclear Physics, Ed. by A. Covello (World Scientific

3He-rich SEP Events Observed by STEREO-A

Using the SIT (Suprathermal Ion Telescope) instrument on STEREO-A we have examined the abundance of the rare isotope 3He during the rising activity phase of solar cycle 24 between January 2010 and December 2011. We have identified six solar energetic particle (SEP) events with enormous abundance enhancements of 3He (3He/4He >1). The events were short lasting, typically ~0.5-1 day and most of them occurred in association with high-speed solar wind streams and corotating interaction regions. With one exception the events were not associated with ~100 keV solar electron intensity increases. The events showed also enhanced NeS/O and Fe/O ratios. The solar images indicate that the events were generally associated with the active regions located near a coronal hole.Comment: accepted for publication in AIP Conference Proceedings for 'Thirteenth International Solar Wind Conference

Molecular Realism in Default Models for Information Theories of Hydrophobic Effects

This letter considers several physical arguments about contributions to hydrophobic hydration of inert gases, constructs default models to test them within information theories, and gives information theory predictions using those default models with moment information drawn from simulation of liquid water. Tested physical features include: packing or steric effects, the role of attractive forces that lower the solvent pressure, and the roughly tetrahedral coordination of water molecules in liquid water. Packing effects (hard sphere default model) and packing effects plus attractive forces (Lennard-Jones default model) are ineffective in improving the prediction of hydrophobic hydration free energies of inert gases over the previously used Gibbs and flat default models. However, a conceptually simple cluster Poisson model that incorporates tetrahedral coordination structure in the default model is one of the better performers for these predictions. These results provide a partial rationalization of the remarkable performance of the flat default model with two moments in previous applications. The cluster Poisson default model thus will be the subject of further refinement.Comment: 5 pages including 3 figure

Black Hole Formation and Classicalization in Ultra-Planckian 2 -> N Scattering

We establish a connection between the ultra-Planckian scattering amplitudes in field and string theory and unitarization by black hole formation in these scattering processes. Using as a guideline an explicit microscopic theory in which the black hole represents a bound-state of many soft gravitons at the quantum critical point, we were able to identify and compute a set of perturbative amplitudes relevant for black hole formation. These are the tree-level N-graviton scattering S-matrix elements in a kinematical regime (called classicalization limit) where the two incoming ultra-Planckian gravitons produce a large number N of soft gravitons. We compute these amplitudes by using the Kawai-Lewellen-Tye relations, as well as scattering equations and string theory techniques. We discover that this limit reveals the key features of the microscopic corpuscular black hole N-portrait. In particular, the perturbative suppression factor of a N-graviton final state, derived from the amplitude, matches the non-perturbative black hole entropy when N reaches the quantum criticality value, whereas final states with different value of N are either suppressed or excluded by non-perturbative corpuscular physics. Thus we identify the microscopic reason behind the black hole dominance over other final states including non-black hole classical object. In the parameterization of the classicalization limit the scattering equations can be solved exactly allowing us to obtain closed expressions for the high-energy limit of the open and closed superstring tree-level scattering amplitudes for a generic number N of external legs. We demonstrate matching and complementarity between the string theory and field theory in different large-s and large-N regimes.Comment: 55 pages, 7 figures, LaTeX; v2: typos removed; final version to appear in Nucl. Phys.

Construction of Simulation Wavefunctions for Aqueous Species: D3O+

This paper investigates Monte Carlo techniques for construction of compact wavefunctions for the internal atomic motion of the D3O+ ion. The polarization force field models of Stillinger, et al and of Ojamae, et al. were used. Initial pair product wavefunctions were obtained from the asymptotic high temperature many-body density matrix after contraction to atom pairs using Metropolis Monte Carlo. Subsequent characterization shows these pair product wavefunctions to be well optimized for atom pair correlations despite that fact that the predicted zero point energies are too high. The pair product wavefunctions are suitable to use within variational Monte Carlo, including excited states, and density matrix Monte Carlo calculations. Together with the pair product wavefunctions, the traditional variational theorem permits identification of wavefunction features with significant potential for further optimization. The most important explicit correlation variable found for the D3O+ ion was the vector triple product {\bf r}$_{OD1}\cdot$({\bf r}$_{OD2}\times${\bf r}$_{OD3}$). Variational Monte Carlo with 9 of such explicitly correlated functions yielded a ground state wavefunction with an error of 5-6% in the zero point energy.Comment: 17 pages including 6 figures, typos correcte

Tracing out the Northern Tidal Stream of the Sagittarius Dwarf Spheoridal Galaxy

The main aim of this paper is to report two new detections of tidal debris in the northern stream of the Sagittarius dwarf galaxy located at 45 arcdeg and 55 arcdeg from the center of galaxy. Our observational approach is based on deep color-magnitude diagrams, that provides accurate distances, surface brightness and the properties of stellar population of the studied region of this tidal stream. The derived distances for these tidal debris wraps are 45 kpc and 54 kpc respectively.We also confirm these detections with numerical simulations of the Sagittarius dwarf plus the Milky Way. The model reproduces the present position and velocity of the Sagittarius main body and presents a long tidal stream formed by tidal interaction with the Milky Way potential. This model is also in good agreement with the available observations of the Sagittarius tidal stream. We also present a method for estimating the shape of the Milky Way halo potential using numerical simulations. From our simulations we obtain an oblateness of the Milky Way dark halo potential of 0.85, using the current database of distances and radial velocities of the Sagittarius tidal stream. The color-magnitude diagram of the apocenter of Sagittarius shows that this region of the stream shares the complex star formation history observed in the main body of the galaxy. We present the first evidence for a gradient in the stellar population along the stream, possibly correlated with its different pericenter passages. (abridged)Comment: 43 pages (including 15 figures; for high resolution color figures, please contact [email protected]). Submitted to Ap

Multi-Spacecraft Observations of Recurrent 3He-Rich Solar Energetic Particles

We study the origin of 3He-rich solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) solar regions with long-lasting conditions for 3He acceleration and 2) solar energetic 3He that is temporary confined/re-accelerated in interplanetary space.Comment: accepted for publication in The Astrophysical Journa

Maximum power, ecological function and efficiency of an irreversible Carnot cycle. A cost and effectiveness optimization

In this work we include, for the Carnot cycle, irreversibilities of linear finite rate of heat transferences between the heat engine and its reservoirs, heat leak between the reservoirs and internal dissipations of the working fluid. A first optimization of the power output, the efficiency and ecological function of an irreversible Carnot cycle, with respect to: internal temperature ratio, time ratio for the heat exchange and the allocation ratio of the heat exchangers; is performed. For the second and third optimizations, the optimum values for the time ratio and internal temperature ratio are substituted into the equation of power and, then, the optimizations with respect to the cost and effectiveness ratio of the heat exchangers are performed. Finally, a criterion of partial optimization for the class of irreversible Carnot engines is herein presented.Comment: 17 pages, 4 figures. Submitted to Energy Convers. Manag

Ultra-High Energy Probes of Classicalization

Classicalizing theories are characterized by a rapid growth of the scattering cross section. This growth converts these sort of theories in interesting probes for ultra-high energy experiments even at relatively low luminosity, such as cosmic rays or Plasma Wakefield accelerators. The microscopic reason behind this growth is the production of N-particle states, classicalons, that represent self-sustained lumps of soft Bosons. For spin-2 theories this is the quantum portrait of what in the classical limit are known as black holes. We emphasize the importance of this quantum picture which liberates us from the artifacts of the classical geometric limit and allows to scan a much wider landscape of experimentally-interesting quantum theories. We identify a phenomenologically-viable class of spin-2 theories for which the growth of classicalon production cross section can be as efficient as to compete with QCD cross section already at 100 TeV energy, signaling production of quantum black holes with graviton occupation number of order 10^4.Comment: 23 pages, late