7,032 research outputs found
Avoided intersections of nodal lines
We consider real eigen-functions of the Schr\"odinger operator in 2-d. The
nodal lines of separable systems form a regular grid, and the number of nodal
crossings equals the number of nodal domains. In contrast, for wave functions
of non integrable systems nodal intersections are rare, and for random waves,
the expected number of intersections in any finite area vanishes. However,
nodal lines display characteristic avoided crossings which we study in the
present work. We define a measure for the avoidance range and compute its
distribution for the random waves ensemble. We show that the avoidance range
distribution of wave functions of chaotic systems follow the expected random
wave distributions, whereas for wave functions of classically integrable but
quantum non-separable wave functions, the distribution is quite different.
Thus, the study of the avoidance distribution provides more support to the
conjecture that nodal structures of chaotic systems are reproduced by the
predictions of the random waves ensemble.Comment: 12 pages, 4 figure
Quasielastic Charged Current Neutrino-nucleus Scattering
We provide integrated cross sections for quasielastic charged-current
neutrino-nucleus scattering. Results evaluated using the phenomenological
scaling function extracted from the analysis of experimental data are
compared with those obtained within the framework of the relativistic impulse
approximation. We show that very reasonable agreement is reached when a
description of final-state interactions based on the relativistic mean field is
included. This is consistent with previous studies of differential cross
sections which are in accord with the universality property of the superscaling
function.Comment: 5 pages, 3 figures, to be published in Phys. Rev. Let
Breathers on quantized superfluid vortices
We consider the propagation of breathers along a quantized superfluid vortex. Using the correspondence between the local induction approximation (LIA) and the nonlinear Schrödinger equation, we identify a set of initial conditions corresponding to breather solutions of vortex motion governed by the LIA. These initial conditions, which give rise to a long-wavelength modulational instability, result in the emergence of large amplitude perturbations that are localized in both space and time. The emergent structures on the vortex filament are analogous to loop solitons but arise from the dual action of bending and twisting of the vortex. Although the breather solutions we study are exact solutions of the LIA equations, we demonstrate through full numerical simulations that their key emergent attributes carry over to vortex dynamics governed by the Biot-Savart law and to quantized vortices described by the Gross-Pitaevskii equation. The breather excitations can lead to self-reconnections, a mechanism that can play an important role within the crossover range of scales in superfluid turbulence. Moreover, the observation of breather solutions on vortices in a field model suggests that these solutions are expected to arise in a wide range of other physical contexts from classical vortices to cosmological strings
Superscaling and neutral current quasielastic neutrino-nucleus scattering
The superscaling approach is applied to studies of neutral current neutrino
reactions in the quasielastic regime. Using input from scaling analyses of
electron scattering data, predictions for high-energy neutrino and antineutrino
cross sections are given and compared with results obtained using the
relativistic Fermi gas model. The influence of strangeness content inside the
nucleons in the nucleus is also explored.Comment: 28 pages, 8 figures, accepted for publication in Phys.Rev.
Relativistic Models for Quasi-Elastic Neutrino-Nucleus Scattering
Two relativistic approaches to charged-current quasielastic neutrino-nucleus
scattering are illustrated and compared: one is phenomenological and based on
the superscaling behavior of electron scattering data and the other relies on
the microscopic description of nuclear dynamics in relativistic mean field
theory. The role of meson exchange currents in the two-particle two-hole sector
is explored. The predictions of the models for differential and total cross
sections are presented and compared with the MiniBooNE data.Comment: 3 pages, 3 figures, Proceedings of PANIC 2011, MIT, Cambridge, MA,
July 201
Pionic correlations and meson-exchange currents in two-particle emission induced by electron scattering
Two-particle two-hole contributions to electromagnetic response functions are
computed in a fully relativistic Fermi gas model. All one-pion exchange
diagrams that contribute to the scattering amplitude in perturbation theory are
considered, including terms for pionic correlations and meson-exchange currents
(MEC). The pionic correlation terms diverge in an infinite system and thus are
regularized by modification of the nucleon propagator in the medium to take
into account the finite size of the nucleus. The pionic correlation
contributions are found to be of the same order of magnitude as the MEC.Comment: 14 pages, 15 figure
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