Short time dynamics with initial correlations

The short-time dynamics of correlated systems is strongly influenced by initial correlations giving rise to an additional collision integral in the non-Markovian kinetic equation. Exact cancellation of the two integrals is found if the initial state is thermal equilibrium which is an important consistency criterion. Analytical results are given for the time evolution of the correlation energy which are confirmed by comparisons with molecular dynamics simulations (MD)

Some remarks on one-dimensional force-free Vlasov-Maxwell equilibria

The conditions for the existence of force-free non-relativistic translationally invariant one-dimensional (1D) Vlasov-Maxwell (VM) equilibria are investigated using general properties of the 1D VM equilibrium problem. As has been shown before, the 1D VM equilibrium equations are equivalent to the motion of a pseudo-particle in a conservative pseudo-potential, with the pseudo-potential being proportional to one of the diagonal components of the plasma pressure tensor. The basic equations are here derived in a different way to previous work. Based on this theoretical framework, a necessary condition on the pseudo-potential (plasma pressure) to allow for force-free 1D VM equilibria is formulated. It is shown that linear force-free 1D VM solutions, which so far are the only force-free 1D VM solutions known, correspond to the case where the pseudo-potential is an attractive central potential. A general class of distribution functions leading to central pseudo-potentials is discussed.Comment: Physics of Plasmas, accepte

Bulk rheology and microrheology of active fluids

We simulate macroscopic shear experiments in active nematics and compare them with microrheology simulations where a spherical probe particle is dragged through an active fluid. In both cases we define an effective viscosity: in the case of bulk shear simulations this is the ratio between shear stress and shear rate, whereas in the microrheology case it involves the ratio between the friction coefficient and the particle size. We show that this effective viscosity, rather than being solely a property of the active fluid, is affected by the way chosen to measure it, and strongly depends on details such as the anchoring conditions at the probe surface and on both the system size and the size of the probe particle.Comment: 12 pages, 10 figure

Giant Intrinsic Carrier Mobilities in Graphene and Its Bilayer

We have studied temperature dependences of electron transport in graphene and its bilayer and found extremely low electron-phonon scattering rates that set the fundamental limit on possible charge carrier mobilities at room temperature. Our measurements have shown that mobilities significantly higher than 200,000 cm2/Vs are achievable, if extrinsic disorder is eliminated. A sharp (threshold-like) increase in resistivity observed above approximately 200K is unexpected but can qualitatively be understood within a model of a rippled graphene sheet in which scattering occurs on intra-ripple flexural phonons

Replica field theories, Painleve transcendents, and exact correlation functions

Exact solvability is claimed for nonlinear replica sigma models derived in the context of random matrix theories. Contrary to other approaches reported in the literature, the framework outlined does not rely on traditional "replica symmetry breaking" but rests on a previously unnoticed exact relation between replica partition functions and Painleve transcendents. While expected to be applicable to matrix models of arbitrary symmetries, the method is used to treat fermionic replicas for the Gaussian unitary ensemble (GUE), chiral GUE (symmetry classes A and AIII in Cartan classification) and Ginibre's ensemble of complex non-Hermitean random matrices. Further applications are briefly discussed.Comment: published version, 4 pages, revtex

On the heavy quark mass expansion for the operator Qbar gamma_5 Q and the charm content of eta, eta'

Recently in the context of studies of the intrinsic charm content of the nucleon and of the eta' meson two groups have arrived at different results for the 1/m^3 term of the heavy quark expansion for operator $\bar Q\gamma_5Q$ differing by the factor of six. We show that the form of both results violates certain general conditions. Using the expression for the axial anomaly with the finite Pauli-Villars regularization we obtain a new expression for 1/m^3 term of the heavy quark expansion for $\bar Q\gamma_5 Q$. With this new result we obtain an estimate for the constant f_{\eta'}^{(c)}=-2 MeV.Comment: 4 page

Embedded monopoles in quark eigenmodes in SU(2) Yang-Mills Theory

We study the embedded QCD monopoles (``quark monopoles'') using low-lying eigenmodes of the overlap Dirac operator in zero- and finite-temperature SU(2) Yang-Mills theory on the lattice. These monopoles correspond to the gauge-invariant hedgehogs in the quark-antiquark condensates. The monopoles were suggested to be agents of the chiral symmetry restoration since their cores should suppress the chiral condensate. We study numerically the scalar, axial and chirally invariant definitions of the embedded monopoles and show that the monopole densities are in fact globally anti-correlated with the density of the Dirac eigenmodes. We observe, that the embedded monopoles corresponding to low-lying Dirac eigenvalues are dense in the chirally invariant (high temperature) phase and dilute in the chirally broken (low temperature) phase. We find that the scaling of the scalar and axial monopole densities towards the continuum limit is similar to the scaling of the string-like objects while the chirally invariant monopoles scale as membranes. The excess of gluon energy at monopole positions reveals that the embedded QCD monopole possesses a gluonic core, which is, however, empty at the very center of the monopole.Comment: 29 pages, 27 figures, RevTeX 4.0; revised to match the published version (clarifying remarks, references and acknowledgments are added