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Nuclear Theory·nucl-th

Thursday·January 25, 2018

8 papers—3 primary·5 cross-listed

All8Primary3Cross-lists5
  1. 04

    [Submitted on 23 Jan 2018] (cross-list from hep-ph)

    Parametrized Equation of State for QCD from 3D Ising Model

    Paolo Parotto🇺🇸

    The only first principle knowledge of the QCD equation of state at finite baryonic density is given from Lattice QCD as a Taylor expansion around . The coefficients of such an expansion are currently available up to order . The expected critical behavior of QCD is in the same static universality class as the 3D Ising model. By means of a suitable parametrization for the scaling equation of state of 3D Ising and a parametrized map to connect to QCD, we present an equation of state matching first principle Lattice QCD calculations, which spans the values of baryonic densities explored in the BES-II program, and includes the correct scaling behavior in the proximity of the critical point. This EoS can serve as an important ingredient for the fluid dynamical simulations of heavy ion collisions at BES energies needed as a basis for the calculation of observables. Future comparisons between such calculations and BES-II data can constrain the parameters in the EoS -- including the parameters that describe the location of the critical point. This contribution reports on work done within the Fluctuations/Equation of State working group of the BEST Collaboration.

    Comments:
    9 pages, 5 figures, conference proceeding for the Critical Point and Onset of Deconfinement - CPOD2017
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1801.07801 [pdf]
    PoS(2018)·9 citations
  2. 05

    [Submitted on 24 Jan 2018] (cross-list from astro-ph.HE)

    Matter-neutrino resonance in a multi-angle neutrino bulb model

    A. Vlasenko🇺🇸 · G. C. McLaughlin🇺🇸

    Simulations of neutrino flavor evolution in compact merger environments have shown that neutrino flavor, and hence nucleosynthesis, can be strongly affected by the presence of matter-neutrino resonances (MNRs), where there is a cancelation between the matter and the neutrino potential. Simulations performed thus far follow flavor evolution along a single neutrino trajectory, but self-consistency requires all trajectories to be treated simultaneously, and it has not been known whether MNR phenomena would still occur in multi-angle models. In this paper, we present the first fully multi-angle calculations of MNR. We find that familiar MNR phenomena, where neutrinos transform to a greater extent than anti-neutrinos and a feedback mechanism maintains the cancellation between the matter and neutrino potential, still occurs for a subset of angular bins, although the flavor transformation is not as efficient as in the single-angle case. In addition, we find other types of flavor transformation that are not seen in single-angle simulations. These flavor transformation phenomena appear to be robust and are present for a wide range of model parameters, as long as an MNR is present. Although computational constraints currently limit us to models with spherical symmetry, our results suggest that the presence of an MNR generally leads to large-scale neutrino flavor evolution in multi-angle systems.

    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1801.07813 [pdf]
    PRD(2018)·31 citations
  3. 06

    [Submitted on 24 Jan 2018] (cross-list from cond-mat.quant-gas)

    From few to many body degrees of freedom

    Manuel Valiente

    Here, I focus on the use of microscopic, few-body techniques that are relevant in the many-body problem. These methods can be divided into indirect and direct. In particular, indirect methods are concerned with the simplification of the many-body problem by substituting the full, microscopic interactions by pseudopotentials which are designed to reproduce collisional information at specified energies, or binding energies in the few-body sector. These simplified interactions yield more tractable theories of the many-body problem, and are equivalent to effective field theory of interactions. Direct methods, which so far are most useful in one spatial dimension, have the goal of attacking the many-body problem at once by using few-body information only. Here, I will present non-perturbative direct methods to study one-dimensional fermionic and bosonic gases in one dimension.

    Comments:
    22 pages, 0 figures. Lecture notes presented at Critical Stability of Quantum Few-Body Systems, Dresden, 9-16 October 2017, plus some new results on the subject
    Subjects:
    Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1801.07955 [pdf]
    Few Body Syst.(2018)·1 citation
  4. 07

    [Submitted on 23 Jan 2018] (cross-list from astro-ph.CO)

    Precision big bang nucleosynthesis with improved Helium-4 predictions

    Cyril Pitrou🇫🇷 · Alain Coc🇫🇷 · Jean-Philippe Uzan🇫🇷 · Elisabeth Vangioni🇫🇷

    Primordial nucleosynthesis is one of the three historical evidences for the big bang model, together with the expansion of the universe and the cosmic microwave background. Now that the number of neutrino families and the baryonic densities have been fixed by laboratory measurements or CMB observations, the model has no free parameter and its predictions are rigid. Departure from its predictions could provide hints or constraints on new physics or astrophysics in the early universe. Precision on primordial abundances deduced from observations have recently been drastically improved and reach the percent level for both deuterium and helium-4. Accordingly, the BBN predictions should reach the same level of precision. For most isotopes, the dominant sources of uncertainty come from those on the laboratory thermonuclear reactions. This article focuses on helium-4 whose predicted primordial abundance depends essentially on weak interactions which control the neutron-proton ratio. The rates of the various weak interaction processes depend on the experimentally measured neutron lifetime, but also includes numerous corrections that we thoroughly investigate here. They are the radiative, zero-temperature, corrections, finite nucleon mass corrections, finite temperature radiative corrections, weak-magnetism, and QED plasma effects, which are for the first time all included and calculated in a self consistent way, allowing to take into account the correlations between them, and verifying that all satisfy detailed balance. The helium-4 predicted mass fraction is . In addition, we provide a Mathematica code (PRIMAT) that incorporates, not only these corrections but also a full network of reactions, using the best available thermonuclear reaction rates, allowing the predictions of primordial abundances up to the CNO region.

    Comments:
    56 pages, 31 figures
    Subjects:
    Cosmology and Nongalactic Astrophysics (astro-ph.CO); Nuclear Theory (nucl-th)
    arXiv:
    1801.08023 [pdf]
    Phys.Rept.(2018)·500 citations
  5. 08

    [Submitted on 24 Jan 2018] (cross-list from cond-mat.quant-gas)

    Virial expansion for the Tan contact and Beth-Uhlenbeck formula from 2D SO(2,1) anomalies

    Wilder S. Daza🇺🇸 · Joaquín E. Drut🇺🇸 · Chris L. Lin🇺🇸 · Carlos R. Ordóñez🇺🇸

    The relationship between 2D conformal anomalies in nonrelativistic systems and the virial expansion is explored using recently developed path-integral methods. In the process, the Beth-Uhlenbeck formula for the shift of the second virial coefficient is obtained, as well as a virial expansion for the Tan contact. A possible extension of these techniques for higher orders in the virial expansion is discussed.

    Comments:
    9 pages, 2 figures
    Subjects:
    Quantum Gases (cond-mat.quant-gas); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    1801.08086 [pdf]
    PRA(2018)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE