Nuclear Theory·nucl-th

Tuesday·June 23, 2015

14 papers—8 primary·6 cross-listed

09
On thermalization of a boost-invariant non Abelian plasma
L. Bellantuono🇮🇹 · P. Colangelo🇮🇹 · F. De Fazio🇮🇹 · F. Giannuzzi🇮🇹
Using a holographic method, we further investigate the relaxation towards the hydrodynamic regime of a boost-invariant non-Abelian plasma taken out-of-equilibrium. In the dual description, the system is driven out-of-equilibrium by boundary sourcing, a deformation of the boundary metric, as proposed by Chesler and Yaffe. The effects of several deformation profiles on the bulk geometry are investigated by the analysis of the corresponding solutions of the Einstein equations. The time of restoration of the hydrodynamic regime is investigated: setting the effective temperature of the system at the end of the boundary quenching to $T_{e f f} (τ^{*}) = 500$ MeV, the hydrodynamic regime is reached after a lapse of time of $O$ (1 fm/c).
↳ hep-phhep-thnucl-thJHEP(2015)·27 citations
10
Quasi-power laws in multiparticle production processes
Grzegorz Wilk🇵🇱 · Zbigniew Włodarczyk🇵🇱
We review the ubiquitous presence in multiparticle production processes of quasi-power law distributions (i.e., distributions following pure power laws for large values of the argument but remaining finite, usually exponential, for small values). Special emphasis is placed on the conjecture that this reflects the presence in the produced hadronic systems of some intrinsic fluctuations. If described by parameter q they form, together with the scale parameter $T$ ("temperature"), basis of Tsallis distribution, $f (X) \sim [1 - (1 - q) X / T]^{1/ (1 - q)}$ , frequently used to describe the relevant distributions (the X being usually a transverse momentum). We discuss the origin of such quasi-power law behavior based on our experience with the description of multiparticle production processes. In particular, we discuss Tsallis distribution with complex nonextensivity parameter q and argue that it is needed to describe log-oscillations as apparently observed in recent data on large momentum distributions in very high energy p-p collisions.
↳ hep-phcond-mat.stat-mechnucl-thChaos Solitons Fractals(2015)·14 citations
11
Quantum scalar fields in de Sitter space from the nonperturbative renormalization group
Maxime Guilleux🇫🇷 · Julien Serreau🇫🇷
We investigate scalar field theories in de Sitter space by means of nonperturbative renormalization group techniques. We compute the functional flow equation for the effective potential of O(N) theories in the local potential approximation and we study the onset of curvature-induced effects as quantum fluctuations are progressively integrated out from subhorizon to superhorizon scales. This results in a dimensional reduction of the original action to an effective zero-dimensional Euclidean theory. We show that the latter is equivalent both to the late-time equilibrium state of the stochastic approach of Starobinsky and Yokoyama and to the effective theory for the zero mode on Euclidean de Sitter space. We investigate the immediate consequences of this dimensional reduction: symmetry restoration and dynamical mass generation.
↳ hep-thgr-qchep-phnucl-thPRD(2015)·66 citations
12
Neutrino Quantum Kinetic Equations
Cristina Volpe🇫🇷
Neutrinos propagate in astrophysical and cosmological environments modifying their flavor in intriguing ways. The study of neutrino propagation in media is based on the mean-field, extended mean-field and Boltzmann equations. We summarise salient features of these evolution equations and the methods employed so far to derive them. We emphasize applications to situations of observational interest.
↳ astro-ph.SRhep-phnucl-thIJMPE(2015)·96 citations
13
Iso-vector and Iso-scalar Tensor Charges of the Nucleon from Lattice QCD
Tanmoy Bhattacharya🇺🇸 · Vincenzo Cirigliano🇺🇸 · Saul Cohen🇺🇸 · Rajan Gupta🇺🇸 · Anosh Joseph🇩🇪 · Huey-Wen Lin🇺🇸 · Boram Yoon🇺🇸
We present results for the iso-vector and flavor diagonal tensor charges $g_{T}^{u - d}$ , $g_{T}^{u}$ , $g_{T}^{d}$ , and $g_{T}^{s}$ needed to probe novel tensor interactions at the TeV scale in neutron and nuclear $β$ -decays and the contribution of the quark electric dipole moment (EDM) to the neutron EDM. The lattice QCD calculations were done using nine ensembles of gauge configurations generated by the MILC collaboration using the HISQ action with 2+1+1 dynamical flavors. These ensembles span three lattice spacings $a \approx 0.06, 0.09$ and $0.12$ fm and three quark masses corresponding to the pion masses $M_{π} \approx 130, 220$ and $310$ MeV. Using estimates from these ensembles, we quantify all systematic uncertainties and perform a simultaneous extrapolation in the lattice spacing, volume and light quark masses for the connected contributions. The final estimates of the connected nucleon (proton) tensor charge for the iso-vector combination is $g_{T}^{u - d} = 1.020 (76)$ in the $MS ˉ$ scheme at $2$ GeV. The additional disconnected quark loop contributions needed for the flavor-diagonal matrix elements are calculated using a stochastic estimator employing the truncated solver method with the all-mode-averaging technique. We find that the size of the disconnected contribution is smaller than the statistical error in the connected contribution. This allows us to bound the disconnected contribution and include it as an additional uncertainty in the flavor-diagonal charges. After a continuum extrapolation, we find $g_{T}^{u} = 0.774 (66)$ , $g_{T}^{d} = - 0.233 (28)$ and $g_{T}^{u + d} = 0.541 (67)$ . The strangeness tensor charge, that can make a significant contribution to the neutron EDM due to the large ratio $m_{s} / m_{u, d}$ , is $g_{T}^{s} = 0.008 (9)$ in the continuum limit.
↳ hep-lathep-phnucl-thPRD(2015)·169 citations
14
Isotropization and hydrodynamization in weakly coupled heavy-ion collisions
Aleksi Kurkela🇨🇭 · Yan Zhu🇪🇸
We numerically solve 2+1D effective kinetic theory of weak coupling QCD under longitudinal expansion relevant for early stages of heavy-ion collisions. We find agreement with viscous hydrodynamics and classical Yang-Mills simulations in the regimes where they are applicable. By choosing initial conditions that are motivated by color-glass-condensate framework we find that for Q=2GeV and $α_{s}$ =0.3 the system is approximately described by viscous hydrodynamics well before $τ ≲ 1.0$ fm/c.
↳ hep-phnucl-thPRL(2015)·314 citations

Affiliations

first authorsco-authorsvia INSPIRE

On thermalization of a boost-invariant non Abelian plasma

Quasi-power laws in multiparticle production processes

Quantum scalar fields in de Sitter space from the nonperturbative renormalization group

Neutrino Quantum Kinetic Equations

Iso-vector and Iso-scalar Tensor Charges of the Nucleon from Lattice QCD

Isotropization and hydrodynamization in weakly coupled heavy-ion collisions

Affiliations