Exact numerical methods for a many-body Wannier Stark system

We present exact methods for the numerical integration of the Wannier-Stark system in a many-body scenario including two Bloch bands. Our ab initio approaches allow for the treatment of a few-body problem with bosonic statistics and strong interparticle interaction. The numerical implementation is based on the Lanczos algorithm for the diagonalization of large, but sparse symmetric Floquet matrices. We analyze the scheme efficiency in terms of the computational time, which is shown to scale polynomially with the size of the system. The numerically computed eigensystem is applied to the analysis of the Floquet Hamiltonian describing our problem. We show that this allows, for instance, for the efficient detection and characterization of avoided crossings and their statistical analysis. We finally compare the efficiency of our Lanczos diagonalization for computing the temporal evolution of our many-body system with an explicit fourth order Runge-Kutta integration. Both implementations heavily exploit efficient matrix-vector multiplication schemes. Our results should permit an extrapolation of the applicability of exact methods to increasing sizes of generic many-body quantum problems with bosonic statistics

Resonance-assisted decay of nondispersive wave packets

We present a quantitative semiclassical theory for the decay of nondispersive electronic wave packets in driven, ionizing Rydberg systems. Statistically robust quantities are extracted combining resonance assisted tunneling with subsequent transport across chaotic phase space and a final ionization step.Comment: 4 pages, 2 figure

Estudio Arqueometalúrgico de una escoria metalúrgica aparecida en el yacimiento de Begastri

Se trata de una escoria encontrada en la segunda campaña de la excavación, en el corte A-111-80, Estrato 11, recogida el 12 de diciembre de 1980, habiéndole sido asignado el número de inventario 149. Estaba envuelta en tierra como corresponde a un objeto que ha permanecido largo tiempo enterrado. Dado el nulo valor museable de la pieza, parece rentable arriesgarse a su destrucción en un estudio que determine el tipo de horno en el que fue generada, lo cual puede servir de orientación en la futura continuación de la excavación, en la actualidad apenas comenzada, ya que la aparición de un trozo aislado enterrado de escoria puede sugerir la posibilidad de que los hornos no estén muy lejos

Collapse and revival in inter-band oscillations of a two-band Bose-Hubbard model

We study the effect of a many-body interaction on inter-band oscillations in a two-band Bose-Hubbard model with external Stark force. Weak and strong inter-band oscillations are observed, where the latter arise from a resonant coupling of the bands. These oscillations collapse and revive due to a weak two-body interaction between the atoms. Effective models for oscillations in and out of resonance are introduced that provide predictions for the system's behaviour, particularly for the time-scales for the collapse and revival of the resonant inter-band oscillations.Comment: 10 pages, 5 figure

Estudio Arqueometalúrgico de una escoria metalúrgica aparecida en el yacimiento de Begastri

Se trata de una escoria encontrada en la segunda campaña de la excavación, en el corte A-111-80, Estrato 11, recogida el 12 de diciembre de 1980, habiéndole sido asignado el número de inventario 149. Estaba envuelta en tierra como corresponde a un objeto que ha permanecido largo tiempo enterrado. Dado el nulo valor museable de la pieza, parece rentable arriesgarse a su destrucción en un estudio que determine el tipo de horno en el que fue generada, lo cual puede servir de orientación en la futura continuación de la excavación, en la actualidad apenas comenzada, ya que la aparición de un trozo aislado enterrado de escoria puede sugerir la posibilidad de que los hornos no estén muy lejos

Confident methods for the evaluation of the hydrogen content in nanoporous carbon microfibers

Abstract Nanoporous carbon microfibers were grown by chemical vapor deposition in the vapor-liquid solid mode using different fluid hydrocarbons as precursors in different proportions. The as-grown samples were further treated in argon and hydrogen atmospheres at different pressure conditions and annealed at several temperatures in order to deduce the best conditions for the incorporation and re-incorporation of hydrogen into the microfibers through the nanopores. Since there are some discrepancies in the results on the hydrogen content obtained under vacuum conditions, in this work, we have measured the hydrogen content in the microfibers using several analytical methods in ambient conditions: surface tension, mass density, and Raman measurements. A discussion on the validity of the results obtained through the correlation between them is the purpose of the present work.Peer Reviewe

A two-band Bose-Hubbard model for many-body resonant tunneling in the Wannier-Stark system

We study an experimentally realizable paradigm of complex many-body quantum systems, a two-band Wannier-Stark model, for which diffusion in Hilbert space as well as many-body Landau-Zener processes can be engineered. A cross-over between regular to quantum chaotic spectra is found within the many-body avoided crossings at resonant tunneling conditions. The spectral properties are shown to determine the evolution of states across a cascade of Landau-Zener events. We apply the obtained spectral information to study the non-equilibrium dynamics of our many-body system in different parameter regimes.Comment: much extended and improved version (13 pages, 10 figures); comments are very welcome