Ledoux-Convection in Protoneutron Stars --- a Clue to Supernova Nucleosynthesis?

Two-dimensional hydrodynamical simulations of the deleptonization of a newly formed neutron star were performed. Driven by negative lepton fraction and entropy gradients, convection starts near the neutrinosphere about 20-30 ms after core bounce, but moves deeper into the protoneutron star, and after about one second the whole protoneutron star is convective. The deleptonization of the star proceeds much faster than in the corresponding spherically symmetrical model because the lepton flux and the neutrino luminosities increase by up to a factor of two. The convection below the neutrinosphere raises the neutrinospheric temperatures and mean energies of the emitted neutrinos by 10-20%. This can have important implications for the supernova explosion mechanism and changes the detectable neutrino signal from the Kelvin-Helmholtz cooling of the protoneutron star. In particular, the enhanced electron neutrino flux relative to the electron antineutrino flux during the early post-bounce evolution might solve the overproduction problem of certain elements in the neutrino-heated ejecta in models of type-II supernova explosions.Comment: 17 pages, LaTeX, 8 postscript figures, uses epsf.sty. To appear in ApJ 473 (Letters), 1996 December 1

Comparison of lunar rocks and meteorites: Implications to histories of the moon and parent meteorite bodies

A number of similarities between lunar and meteoritic rocks are reported and suggest that the comparison is essential for a clear understanding of meteorites as probes of the early history of the solar systems: (1) Monomict and polymict breccias occur in lunar rocks, as well as in achondritic and chondritic meteorites, having resulted from complex and repeated impact processes. (2) Chondrules are present in lunar, as well as in a few achondritic and most chondritic meteorites. It is pointed out that because chondrules may form in several different ways and in different environments, a distinction between the different modes of origin and an estimate of their relative abundance is important if their significance as sources of information on the early history of the solar system is to be clearly understood. (3) Lithic fragments are very useful in attempts to understand the pre- and post-impact history of lunar and meteoritic breccias. They vary from little modified (relative to the apparent original texture), to partly or completely melted and recrystallized lithic fragments

Strangeness in Compact Stars and Signal of Deconfinement

Phase transitions in compact stars are discussed including hyperonization, deconfinement and crystalline phases. Reasons why kaon condensation is unlikely is reviewed. Particular emphasis is placed on the evolution of internal structure with spin-down of pulsars. A signature of a first order phase transition in the timing structure of pulsars which is strong and easy to measure, is identified.Comment: 17 pages, 15 figures, Latex. (Invited Talk at the International Symposium on ``Strangeness In Quark Matter 1997'', Thera (Santorini), Hellas, April 14-18, 1997, To be published in Journal of Physics G (Organizers: A Panagiotou and J. Madsen

Role of isospin physics in supernova matter and neutron stars

We investigate the liquid-gas phase transition of hot protoneutron stars shortly after their birth following supernova explosion and the composition and structure of hyperon-rich (proto)neutron stars within a relativistic mean-field model where the nuclear symmetry energy has been constrained from the measured neutron skin thickness of finite nuclei. Light clusters are abundantly formed with increasing temperature well inside the neutrino-sphere for an uniform supernova matter. Liquid-gas phase transition is found to suppress the cluster yield within the coexistence phase as well as decrease considerably the neutron-proton asymmetry over a wide density range. We find symmetry energy has a modest effect on the boundaries and the critical temperature for the liquid-gas phase transition, and the composition depends more sensitively on the number of trapped neutrinos and temperature of the protoneutron star. The influence of hyperons in the dense interior of stars makes the overall equation of state soft. However, neutrino trapping distinctly delays the appearance of hyperons due to abundance of electrons. We also find that a softer symmetry energy further makes the onset of hyperon less favorable. The resulting structures of the (proto)neutron stars with hyperons and with liquid-gas phase transition are discussed.Comment: 11 pages, 7 figures, RevTe

Dynamics and neutrino signal of black hole formation in non-rotating failed supernovae. II. progenitor dependence

We study the progenitor dependence of the black hole formation and its associated neutrino signals from the gravitational collapse of non-rotating massive stars, following the preceding study on the single progenitor model in Sumiyoshi et al. (2007). We aim to clarify whether the dynamical evolution toward the black hole formation occurs in the same manner for different progenitors and to examine whether the characteristic of neutrino bursts is general having the short duration and the rapidly increasing average energies. We perform the numerical simulations by general relativistic neutrino-radiation hydrodynamics to follow the dynamical evolution from the collapse of pre-supernova models of 40Msun and 50Msun toward the black hole formation via contracting proto-neutron stars. For the three progenitor models studied in this paper, we found that the black hole formation occurs in ~0.4-1.5 s after core bounce through the increase of proto-neutron star mass together with the short and energetic neutrino burst. We found that density profile of progenitor is important to determine the accretion rate onto the proto-neutron star and, therefore, the duration of neutrino burst. We compare the neutrino bursts of black hole forming events from different progenitors and discuss whether we can probe clearly the progenitor and/or the dense matter.Comment: 30 pages, 11 figures, accepted for publication in Ap

Dynamics and neutrino signal of black hole formation in non-rotating failed supernovae. I. EOS dependence

We study the black hole formation and the neutrino signal from the gravitational collapse of a non-rotating massive star of 40 Msun. Adopting two different sets of realistic equation of state (EOS) of dense matter, we perform the numerical simulations of general relativistic neutrino-radiation hydrodynamics under the spherical symmetry. We make comparisons of the core bounce, the shock propagation, the evolution of nascent proto-neutron star and the resulting re-collapse to black hole to reveal the influence of EOS. We also explore the influence of EOS on the neutrino emission during the evolution toward the black hole formation. We find that the speed of contraction of the nascent proto-neutron star, whose mass increases fast due to the intense accretion, is different depending on the EOS and the resulting profiles of density and temperature differ significantly. The black hole formation occurs at 0.6-1.3 sec after bounce when the proto-neutron star exceeds its maximum mass, which is crucially determined by the EOS. We find that the average energies of neutrinos increase after bounce because of rapid temperature increase, but at different speeds depending on the EOS. The duration of neutrino emission up to the black hole formation is found different according to the different timing of re-collapse. These characteristics of neutrino signatures are distinguishable from those for ordinary proto-neutron stars in successful core-collapse supernovae. We discuss that a future detection of neutrinos from black-hole-forming collapse will contribute to reveal the black hole formation and to constrain the EOS at high density and temperature.Comment: 32 pages, 33 figures, accepted for publication in Ap

Long-Range Temporal Correlations in Resting State Beta Oscillations are Reduced in Schizophrenia

Symptoms of schizophrenia (SCZ) are likely to be generated by genetically mediated synaptic dysfunction, which contribute to large-scale functional neural dysconnectivity. Recent electrophysiological studies suggest that this dysconnectivity is present not only at a spatial level but also at a temporal level, operationalized as long-range temporal correlations (LRTCs). Previous research suggests that alpha and beta frequency bands have weaker temporal stability in people with SCZ. This study sought to replicate these findings with high-density electroencephalography (EEG), enabling a spatially more accurate analysis of LRTC differences, and to test associations with characteristic SCZ symptoms and cognitive deficits. A 128-channel EEG was used to record eyes-open resting state brain activity of 23 people with SCZ and 24 matched healthy controls (HCs). LRTCs were derived for alpha (8–12 Hz) and beta (13–25 Hz) frequency bands. As an exploratory analysis, LRTC was source projected using sLoreta. People with SCZ showed an area of significantly reduced beta-band LRTC compared with HCs over bilateral posterior regions. There were no between-group differences in alpha-band activity. Individual symptoms of SCZ were not related to LRTC values nor were cognitive deficits. The study confirms that people with SCZ have reduced temporal stability in the beta frequency band. The absence of group differences in the alpha band may be attributed to the fact that people had, in contrast to previous studies, their eyes open in the current study. Taken together, our study confirms the utility of LRTC as a marker of network instability in people with SCZ and provides a novel empirical perspective for future examinations of network dysfunction salience in SCZ research

Linear beam-beam resonance due to coherent dipole motion

We study the transverse motion of the barycentres of bunches in two beams, which circulate in opposite direction in a storage ring, and are coupled by the beam-beam effect. the motion is described by a linear system of escillators, and represented by a matrix. We distinguish between perfect machines in which the bunch parameters and the arc and interaction point parameters are all equal, and machines with errors in which at least one of these conditions is not satisfied. We determine the regions in tune space where the motion is unstable, analytically for perfect machines, and numerically for machines with errors. We identify these regions as resonances related to the tunes of one of the two beams or to their sum. We establish what resonances are excited under given conditions. We find that more resonances occur in machines with errors than in perfect machines. by multi-particle tracking, we study the instability at finite amplitudes