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Meir Lewkowicz

Publications and source records attributed to Meir Lewkowicz.

5 recordsLinked to original sources
arXiv2022

Chiral Magnetic Effect out of equilibrium

We consider relativistic fermionic systems in lattice regularization out of equilibrium. The chiral magnetic conductivity $\sigma_{CME}$ is calculated in spatially infinite system for the case when the chiral chemical potential depends on time while the system initially was in thermal equilibrium at small but nonzero temperature. We find that the frequency dependent $\sigma_{CME}(\omega)$ for any nonzero $\omega$ both in the limits $\omega \ll T$ and $\omega \gg T$ is equal to its conventional value $1$ when the lattice model approaches continuum limit. Notice that $\sigma_{CME} = 0$ for the case when the chiral chemical potential does not depend on time at all. We therefore confirm that the limit of vanishing $\omega$ is not regular for the spatially infinite systems of massless fermions.

hep-ph↗
arXiv2022

Measurement of Magnetic Susceptibility of Diamagnetic Liquids Exploiting the Moses Effect

A novel comparative technique enabling measurement of the magnetic susceptibility of diamagnetic liquids with the "Moses effect" is presented. The technique is based on the experimental establishment of the deformation of the liquid/vapor interface by a steady magnetic field. The deformation of the liquid surface by a modest magnetic field $(B\sim 0.60T)$ is measured with an optical technique. The surface tension of the liquid is taken into account. The magnetic susceptibilities of the investigated liquids (Ethanol and Glycerol) were calculated from the maximal slope of the liquid/air interface. The suggested approach yields an accuracy on the order of about $0.4-0.6\%$ and hence is superior to previous methods which used the \textquotedblleft Moses effect\textquotedblright\ for the same purpose.

physics.app-ph↗
arXiv2017

Entropy measures as geometrical tools in the study of cosmology

Classical chaos is often characterized as exponential divergence of nearby trajectories. In many interesting cases these trajectories can be identified with geodesic curves. We define here the entropy by $S = \ln χ(x)$ with $χ(x)$ being the distance between two nearby geodesics. We derive an equation for the entropy which by transformation to a Ricatti-type equation becomes similar to the Jacobi equation. We further show that the geodesic equation for a null geodesic in a double warped space time leads to the same entropy equation. By applying a Robertson-Walker metric for a flat three-dimensional Euclidian space expanding as a function of time, we again reach the entropy equation stressing the connection between the chosen entropy measure and time. We finally turn to the Raychaudhuri equation for expansion, which also is a Ricatti equation similar to the transformed entropy equation. Those Ricatti-type equations have solutions of the same form as the Jacobi equation. The Raychaudhuri equation can be transformed to a harmonic oscillator equation, and it has been shown that the geodesic deviation equation of Jacobi is essentially equivalent to that of a harmonic oscillator. The Raychaudhuri equations are strong geometrical tools in the study of General Relativity and Cosmology. We suggest a refined entropy measure applicable in Cosmology and defined by the average deviation of the geodesics in a congruence.

gr-qc↗
arXiv2007

On the geometry of Hamiltonian chaos

We show that Gutzwiller's characterization of chaotic Hamiltonian systems in terms of the curvature associated with a Riemannian metric tensor in the structure of the Hamiltonian can be extended to a wide class of potential models of standard form through definition of a conformal metric. The geodesic equations reproduce the Hamilton equations of the original potential model when a transition is made to the dual manifold, and the geodesics in the dual space coincide with the orbits of the Hamiltonian potential model. We therefore find a direct geometrical description of the time development of a Hamiltonian potential model. The second covariant derivative of the geodesic deviation in this dual manifold generates a dynamical curvature, resulting in (energy dependent) criteria for unstable behavior different from the usual Lyapunov criteria. We discuss some examples of unstable Hamiltonian systems in two dimensions giving, in particular, detailed results for a potential obtained from a fifth order expansion of a Toda lattice Hamiltonian.

physics.class-ph↗