arXiv subjects

Peter B. Weichman

Publications and source records attributed to Peter B. Weichman.

25 records · Page 2Linked to original sources

arXiv2007

Revisiting the dynamical exponent equality $z=d$ for the dirty boson problem

It is shown that previous arguments leading to the equality $z=d$ ($d$ being the spatial dimensionality) for the dynamical exponent describing the Bose glass to superfluid transition may break down, as apparently seen in recent simulations (Ref. \cite{Baranger}). The key observation is that the major contribution to the compressibility, which remains finite through the transition and was predicted to scale as $κ\sim |δ|^{(d-z)ν}$ (where $δ$ is the deviation from criticality and $ν$ is the correlation length exponent) comes from the analytic part, not the singular part of the free energy, and therefore is not restricted by any conventional scaling hypothesis.

cond-mat.dis-nn↗

arXiv2006

Second sound spectroscopy of a nonequilibrium superfluid-normal interface

An experiment is proposed to test a previously developed theory of the hydrodynamics of a nonequilibrium heat current-induced superfluid-normal interface. It is shown that the interfacial ``trapped'' second sound mode predicted by the theory leads to a sharp resonant dip in the reflected signal from an external second sound pulse propagated towards the interface when its horizontal phase speed matches that of the interface mode. The influence of the interface on thermal fluctuations in the bulk superfluid is shown to lead to slow power dependence of the order parameter, and other quantities, on distance from it.

cond-mat.other↗

arXiv2005

Rossby wave equilibria and zonal jets

The problem of coherent vortex and zonal jet formation in a system of nonlinear Rossby waves is considered from the point of view of the late time steady state achieved by free decay of a given initial state. Statistical equilibrium equations respecting all conservation laws are constructed, generalizing those derived previously for 2D inviscid Euler flow. Jet-like solutions are ubiquitous, with large coherent vortices existing only when there is uniform background flow with the precise velocity to cancel the beta effect.

cond-mat.stat-mech↗

arXiv2004

Surface modes and multi-power law structure in the early-time response of magnetic targets

It was recently demonstrated [P. B. Weichman, Phys. Rev. Lett. {\bf 91}, 143908 (2003)] that the scattered electric field from highly conducting targets following a rapidly terminated electromagnetic pulse displays a universal $t^{-1/2}$ power law divergence at early time. It is now shown that for strongly permeable targets, $μ_c/μ_b \gg 1$, where $μ_b$ is the background magnetic permeability, the early time regime separates into two distinct power law regimes, with the early-early time $t^{-1/2}$ behavior crossing over to $t^{-3/2}$ at late-early time, reflecting a spectrum of magnetic surface modes. The latter is confirmed by data from ferrous targets where $μ_c/μ_b = {\cal O}(10^2)$, and for which the early-early time regime is invisibly narrow.

math-ph↗

arXiv2003

Universal early-time response in high-contrast electromagnetic scattering

The time-domain response of highly conducting targets following a rapidly terminated electromagnetic pulse displays three distinct regimes: early, intermediate and late time. The intermediate and late times are characterized by a superposition of exponentially decaying eigenmodes. At early time an ever increasing number of rapidly decaying modes contribute, with the result that the scattered electric field displays a universal $t^{-1/2}$ power law which emerges from the diffusive decay of a pattern of surface currents induced by the pulse. The power law amplitude reflects the surface geometry of the target, a property that may prove useful in buried target classification in geophysical remote sensing applications.

math-ph↗

arXiv2000

Equilibrium solutions of the shallow water equations

A statistical method for calculating equilibrium solutions of the shallow water equations, a model of essentially 2-d fluid flow with a free surface, is described. The model contains a competing acoustic turbulent {\it direct} energy cascade, and a 2-d turbulent {\it inverse} energy cascade. It is shown, nonetheless that, just as in the corresponding theory of the inviscid Euler equation, the infinite number of conserved quantities constrain the flow sufficiently to produce nontrivial large-scale vortex structures which are solutions to a set of explicitly derived coupled nonlinear partial differential equations.

physics.flu-dyn↗

arXiv2000

Criticality and Superfluidity in liquid He-4 under Nonequilibrium Conditions

We review a striking array of recent experiments, and their theoretical interpretations, on the superfluid transition in $^4$He in the presence of a heat flux, $Q$. We define and evaluate a new set of critical point exponents. The statics and dynamics of the superfluid-normal interface are discussed, with special attention to the role of gravity. If $Q$ is in the same direction as gravity, a self-organized state can arise, in which the entire sample has a uniform reduced temperature, on either the normal or superfluid side of the transition. Finally, we review recent theory and experiment regarding the heat capacity at constant $Q$. The excitement that surrounds this field arises from the fact that advanced thermometry and the future availability of a microgravity experimental platform aboard the International Space Station will soon open to experimental exploration decades of reduced temperature that were previously inaccessible.

cond-mat.stat-mech↗