Nuclear Theory·nucl-th

Monday·December 22, 2014

11 papers—5 primary·6 cross-listed

06
Vector spectral functions and transport properties in quenched QCD
Heng-Tong Ding🇨🇳 · Olaf Kaczmarek🇩🇪 · Florian Meyer🇩🇪
We present new results on the reconstruction of mesonic spectral functions for three temperatures $1.1 T_{c}$ , $1.2 T_{c}$ and $1.4 T_{c}$ in quenched QCD. Making use of non-perturbatively improved clover Wilson valence quarks allows for a clean extrapolation of correlator data to the continuum limit. For the case of vanishing momentum the spectral function is obtained by fitting the data to a well motivated ansatz, using the full covariance matrix of the continuum extrapolated data in the fit. We found that vector correlation function is almost temperature independent in the current temperature window. The electrical conductivity of the hot medium, related to the origin of the vector spectral function at zero momentum, is computed from the resulting parameters at all three temperatures, leading to an estimate of $0.2 C_{e m} ≲ σ / T ≲ 0.4 C_{e m}$ . The dilepton rates resulting from the obtained spectral functions show no significant temperature dependence.
↳ hep-lathep-phnucl-thPoS(2015)·17 citations
07
Universality of plasmon excitations in Dirac semimetals
Dmitri E. Kharzeev🇺🇸 · Robert D. Pisarski🇺🇸 · Ho-Ung Yee🇺🇸
The recent experimental discovery of $C d_{3} A s_{2}$ and $N a_{3} Bi$ Dirac semimetals enables the study of the properties of chiral quasi-particles in three spatial dimensions. As demonstrated by photoemission, Dirac semimetals are characterized by a linear dispersion relation for fermion quasi-particles, and thus represent three dimensional analogs of graphene. While the distinctive behavior of chiral fermions (e.g. Klein tunneling) is already evident in two dimensional graphene, the physics of chirality in three dimensions opens a number of new possibilities. In this paper we investigate the properties of the collective plasmon excitations in Dirac semimetals by using the methods of relativistic field theory. We find a strong and narrow plasmon excitation whose frequency is in the terahertz (THz) range which may be important for practical applications. The properties of the plasmon appear universal for all Dirac semimetals, due to the large degeneracy of the quasi-particles and the small Fermi velocity, $v_{F} ≪ c$ . This universality is closely analogous to the phenomenon of "dimensional transmutation", that is responsible for the emergence of dimensionful scales in relativistic field theories such as Quantum Chromodynamics, the modern theory of nuclear physics.
↳ cond-mat.mes-hallhep-phnucl-thPRL(2015)·14 citations
08
Multiplicity fluctuations at the quark-hadron phase transition from a fluid dynamical model
Christoph Herold🇹🇭 · Marlene Nahrgang🇺🇸 · Yupeng Yan🇹🇭 · Chinorat Kobdaj🇹🇭
The region of large net-baryon densities in the QCD phase diagram is expected to exhibit a first-order phase transition. Experimentally, its study will be one of the primaryobjectives for the upcoming FAIR accelerator. We model the transition between quarks and hadrons in a heavy-ion collision using a fluid which is coupled to the explicit dynamics of the chiral order parameter and a dilaton field. This allows us to investigate signals stemming from the nonequilibrium evolution during the expansion of the hot plasma. Special emphasis is put on an event-by-event analysis of baryon number fluctuations which have long since been claimed to be sensitive to a critical point.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2015)·1 citation
09
Classicalization of Quantum Variables and Quantum-Classical Hybrids
T. Koide🇧🇷
The extraction of classical degrees of freedom in quantum mechanics is studied in the stochastic variational method. By using this classicalization, a hybrid model constructed from quantum and classical variables (quantum-classical hybrids) is derived. In this procedure, conservation laws such as energy are maintained, and Ehrenfest's theorem is still satisfied with modification. The criterion for the applicability of quantum-classical hybrids is also discussed.
↳ quant-phgr-qchep-thnucl-thPLA(2015)·10 citations
10
Electrical conductivity and charge diffusion in thermal QCD from the lattice
Gert Aarts🇬🇧 · Chris Allton🇬🇧 · Alessandro Amato🇬🇧 · Pietro Giudice🇩🇪 · Simon Hands🇬🇧 · Jon-Ivar Skullerud🇮🇪
We present a lattice QCD calculation of the charge diffusion coefficient, the electrical conductivity and various susceptibilities of conserved charges, for a range of temperatures below and above the deconfinement crossover. The calculations include the contributions from up, down and strange quarks. We find that the diffusion coefficient is of the order of 1/(2\pi T) and has a dip around the crossover temperature. Our results are obtained with lattice simulations containing 2+1 dynamical flavours on anisotropic lattices. The Maximum Entropy Method is used to construct spectral functions from correlators of the conserved vector current.
↳ hep-latnucl-thJHEP(2015)·263 citations
11
Variational Principle of Hydrodynamics and Quantization by Stochastic Process
T. Kodama🇧🇷 · T. Koide🇧🇷
The well-known hydrodynamical representation of the Schrödinger equation is reformulated by extending the idea of Nelson-Yasue's stochastic variational method. The fluid flow is composed by the two stochastic processes from the past and the future, which are unified naturally by the principle of maximum entropy. We show that this formulation is easily applicable to the quantization of scalar fields.
↳ quant-phgr-qchep-thnucl-th6 citations

Affiliations

first authorsco-authorsvia INSPIRE

Vector spectral functions and transport properties in quenched QCD

Universality of plasmon excitations in Dirac semimetals

Multiplicity fluctuations at the quark-hadron phase transition from a fluid dynamical model

Classicalization of Quantum Variables and Quantum-Classical Hybrids

Electrical conductivity and charge diffusion in thermal QCD from the lattice

Variational Principle of Hydrodynamics and Quantization by Stochastic Process

Affiliations