Construction of vector valued wavelet packets on ℝ+ using Walsh-Fourier transform

In this paper, the concept of vector-valued wavelet packets in space L ²(?₊, ? ^N ) is introduced. Some properties of vector-valued wavelets packets are studied and orthogonality formulas of these wavelets packets are obtained. New orthonormal basis of L ²(?₊, ? ^N ) is obtained by constructing a series of subspaces of vector-valued wavelet packets.     

Quasiclassical localization of wave packets in nonlinear Schrödinger systems

We consider the nonlinear Schrödinger equation with several kinds of potentials. For studying the existence and stability of the wave packets that could support these systems, a certain functional is constructed, which in some manner possesses the properties of the Lyapunov functional for analyzing the existence and stability of solutions. The general case of potential is considered and the appearance of pulsons is shown. Then we propose three examples of nonlinear classical field theories with potentials that exhibit quartic, sextic and saturable nonlinearities. This method exhibits a criteria for determining quasiclassically the self-localization of wave packets in nonintegrable systems.     

Wave packets and the quadratic Monge–Kantorovich distance in quantum mechanics

In this paper, we extend the upper and lower bounds for the “pseudo-distance” on quantum densities analogous to the quadratic Monge–Kantorovich(–Vasershtein) distance introduced in [F. Golse, C. Mouhot, T. Paul, Commun. Math. Phys. 343 (2016) 165–205] to positive quantizations defined in terms of the family of phase space translates of a density operator, not necessarily of rank 1 as in the case of the Töplitz quantization. As a corollary, we prove that the uniform as $?\to 0$ convergence rate for the mean-field limit of the N-particle Heisenberg equation holds for a much wider class of initial data than in [F. Golse, C. Mouhot, T. Paul, Commun. Math. Phys. 343 (2016) 165–205]. We also discuss the relevance of the pseudo-distance compared to the Schatten norms for the purpose of metrizing the set of quantum density operators in the semiclassical regime.     

Time-dependent Schrödinger equation: Statistics of the distribution of Gaussian packets on a metric graph

We consider a time-dependent Schrödinger equation in which the spatial variable runs over a metric graph. The boundary conditions at the vertices of the graph imply the continuity of the function and the zero sum of the one-sided derivatives taken with some weights. In the semiclassical approximation, we describe a propagation of Gaussian packets on the graph that are localized at a point at the initial instant of time. The main focus is placed on the statistics of the behavior of asymptotic solutions as time increases. We show that the calculation of the number of quantum packets on a graph is related to the well-known number-theoretic problem of finding the number of integer points in an expanding simplex. We prove that the number of Gaussian packets on a finite compact graph grows polynomially. Several examples are considered. In a particular case, Gaussian packets are shown to be distributed on a graph uniformly with respect to the edge travel times.