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Nuclear Theory·nucl-th

Wednesday·January 25, 2017

6 papers—2 primary·4 cross-listed

All6Primary2Cross-lists4
  1. 03

    Fast neutrino conversions: Ubiquitous in compact binary merger remnants

    Meng-Ru Wu🇩🇰 · Irene Tamborra🇩🇰

    The massive neutron star (NS) or black hole (BH) accretion disk resulting from NS--NS or NS--BH mergers is dense in neutrinos. We present the first study on the role of angular distributions in the neutrino flavor conversion above the remnant disk. In particular, we focus on "fast" pairwise conversions whose rate depends on the local angular intensity of the electron lepton number carried by neutrinos. Because of the emission geometry and the flux density of being larger than that of , fast conversions prove to be a generic phenomenon in NS--NS and NS--BH mergers for physically motivated disturbances in the mean field of flavor coherence. Our findings suggest that, differently from the core-collapse supernova case, fast flavor conversions seem to be unavoidable in compact mergers and could have major consequences for the jet dynamics and the synthesis of elements above the remnant disk.

    ↳ astro-ph.HEhep-phnucl-thPRD(2017)·147 citations
  2. 04

    Analytical Spectral Density of the Sachdev-Ye-Kitaev Model at finite N

    Antonio M. García-García🇬🇧 · Jacobus J. M. Verbaarschot🇺🇸

    We show analytically that the spectral density of the -body Sachdeev-Ye-Kitaev (SYK) model agrees with that of Q-Hermite polynomials with Q a non-trivial function of and the number of Majorana fermions . Numerical results, obtained by exact diagonalization, are in excellent agreement with the analytical spectral density even for relatively small . For and not close to the edge of the spectrum, we find the macroscopic spectral density simplifies to , where is the suppression factor of the contribution of intersecting Wick contractions relative to nested contractions. This spectral density reproduces the known result for the free energy in the large and limit. In the infrared region, where the SYK model is believed to have a gravity-dual, the spectral density is given by . It therefore has a square-root edge, as in random matrix ensembles, followed by an exponential growth, a distinctive feature of black holes and also of low energy nuclear excitations. Results for level-statistics in this region confirm the agreement with random matrix theory. Physically this is a signature that, for sufficiently long times, the SYK model and its gravity dual evolve to a fully ergodic state whose dynamics only depends on the global symmetry of the system. Our results strongly suggest that random matrix correlations are a universal feature of quantum black holes and that the SYK model, combined with holography, may be relevant to model certain aspects of the nuclear dynamics.

    ↳ hep-thcond-mat.str-elnucl-thPRD(2017)·193 citations
  3. 05

    Momentum anisotropy effects for quarkonium in a weakly-coupled quark-gluon plasma below the melting temperature

    Simone Biondini🇨🇭 · Nora Brambilla🇩🇪 · Miguel Angel Escobedo🇫🇮 · Antonio Vairo🇩🇪

    In the early stages of heavy-ion collisions, the hot QCD matter expands more longitudinally than transversely. This imbalance causes the system to become rapidly colder in the longitudinal direction and a local momentum anisotropy appears. In this paper, we study the heavy-quarkonium spectrum in the presence of a small plasma anisotropy. We work in the framework of pNRQCD at finite temperature. We inspect arrangements of non-relativistic and thermal scales complementary to those considered in the literature. In particular, we consider temperatures larger and Debye masses smaller than the binding energy, which is a temperature range relevant for presently running LHC experiments. In this setting we compute the leading thermal corrections to the binding energy and the thermal width induced by quarkonium gluo-dissociation.

    ↳ hep-phhep-thnucl-exnucl-thPRD(2017)·10 citations
  4. 06

    Impacts of nuclear-physics uncertainty in stellar temperatures on the s-process nucleosynthesis

    N. Nishimura · G. Cescutti · R. Hirschi · T. Rauscher · J. Den Hartogh · A. St. J. Murphy

    We evaluated the uncertainty relevant to s-process nucleosynthesis using a Monte-Carlo centred approach. We are based on a realistic and general prescription of temperature dependent uncertainty for the reactions. We considered massive stars for the weak s-process and AGB stars for the main s-process. We found that the adopted uncertainty for (n,) rates, tens of per cent on average, affect the production of s-process nuclei along the -stability line, while for -decay, for which contributions from excited states enhances the uncertainty, has the strongest impact on branching points.

    ↳ astro-ph.SRnucl-exnucl-thJPS Conf.Proc.(2017)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE