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Nuclear Theory·nucl-th

Friday·June 19, 2015

9 papers—5 primary·4 cross-listed

All9Primary5Cross-lists4
  1. 06

    Unitary fermions and Luscher's formula on a crystal

    Manuel Valiente · Nikolaj Thomas Zinner

    We consider the low-energy particle-particle scattering properties in a periodic simple cubic crystal. In particular, we investigate the relation between the two-body scattering length and the energy shift experienced by the lowest-lying unbound state when this is placed in a periodic finite box. We introduce a continuum model for s-wave contact interactions that respects the symmetry of the Brillouin zone in its regularisation and renormalisation procedures, and corresponds to the naïve continuum limit of the Hubbard model. The energy shifts are found to be identical to those obtained in the usual spherically symmetric renormalisation scheme upon resolving an important subtlety regarding the cutoff procedure. We then particularize to the Hubbard model, and find that for large finite lattices the results are identical to those obtained in the continuum limit. The results reported here are valid in the weak, intermediate and unitary limits, and can be used for the extraction of scattering information ,via exact diagonalisation or Monte Carlo methods, of two-body systems in realistic periodic lattices.

    ↳ cond-mat.quant-gasnucl-thquant-phSCPMA(2016)·5 citations
  2. 07

    Kinetic theory of a longitudinally expanding system of scalar particles

    Thomas Epelbaum🇨🇦 · Francois Gelis🇫🇷 · Sangyong Jeon🇨🇦 · Guy Moore🇩🇪 · Bin Wu🇫🇷

    A simple kinematical argument suggests that the classical approximation may be inadequate to describe the evolution of a system with an anisotropic particle distribution. In order to verify this quantitatively, we study the Boltzmann equation for a longitudinally expanding system of scalar particles interacting with a coupling, that mimics the kinematics of a heavy ion collision at very high energy. We consider only elastic scatterings, and we allow the formation of a Bose-Einstein condensate in overpopulated situations by solving the coupled equations for the particle distribution and the particle density in the zero mode. For generic CGC-like initial conditions with a large occupation number and a moderate coupling, the solutions of the full Boltzmann equation do not follow a classical attractor behavior.

    ↳ hep-phnucl-thJHEP(2015)·24 citations
  3. 08

    New analysis of the low-energy differential cross sections of the CHAOS Collaboration

    Evangelos Matsinos🇨🇭 · Günther Rasche🇨🇭

    In a previous paper, we reported the results of a partial-wave analysis of the pion-nucleon () differential cross sections (DCSs) of the CHAOS Collaboration and came to the conclusion that the angular distribution of their data sets is incompatible with the rest of the modern (meson-factory) database. The present work, re-addressing this issue, has been instigated by a number of recent improvements in our analysis, namely regarding the inclusion of the theoretical uncertainties when investigating the reproduction of experimental data sets on the basis of a given `theoretical' solution, modifications in the parameterisation of the form factors of the proton and of the pion entering the electromagnetic part of the amplitude, and the inclusion of the effects of the variation of the -meson mass when fitting the ETH model of the interaction to the experimental data. The new analysis of the CHAOS DCSs confirms our earlier conclusions and casts doubt on the value for the term, which Stahov, Clement, and Wagner have extracted from these data.

    ↳ hep-phnucl-thIJMPE(2015)·5 citations
  4. 09

    The pion quasiparticle in the low-temperature phase of QCD

    Bastian B. Brandt🇩🇪 · Anthony Francis🇨🇦 · Harvey B. Meyer🇩🇪 · Daniel Robaina🇩🇪

    We investigate the properties of the pion quasiparticle in the low-temperature phase of two-flavor QCD on the lattice with support from chiral effective theory. We find that the pion quasiparticle mass is significantly reduced compared to its value in the vacuum, by contrast with the static screening mass, which increases with temperature. By a simple argument, near the chiral limit the two masses are expected to determine the quasiparticle dispersion relation. Analyzing two-point functions of the axial charge density at non-vanishing spatial momentum, we find that the predicted dispersion relation and the residue of the pion pole are simultaneously consistent with the lattice data at low momentum. The test, based on fits to the correlation functions, is confirmed by a second analysis using the Backus-Gilbert method.

    ↳ hep-lathep-phnucl-thPRD(2015)·69 citations

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first authorsco-authorsvia INSPIRE