1,721,021 research outputs found
Interaction induced destruction of resonant tunneling in the nonlinear Wannier-Stark problem
No full textBose-Einstein condensates loaded into periodic optical lattices can be subjected to a controlled dynamical evolution, determined by the shape and time-dependence of the potentials. We propose a scheme to measure the temporal decay rates arising from many successive Landau-Zener events. We show that from a measurement of the atomic densities or from a combined density and phase measurement, we can compute the time-dependent survival or recurrence probability of the condensate, respectively. The tunneling of the condensate in a tilted optical lattice is resonantly enhanced for a suitable choice of the static Stark field (or the relative acceleration of two counter-propagating standing waves). Resonantly enhanced tunneling by more than an order of magnitude is predicted for essentially non-interacting atoms. Small mean-field interactions, as readily realized in state-of-the-art experiments, systematically tend to wash out the resonant tunneling peaks. Hence, even in a parameter regime far away from any dynamical instability in the condensate, i.e., where the kinetic and the potential energy usually dominate the dynamics, the atom-atom interactions eventually lead to a destruction of the very sensitive resonant tunneling. This example of the dynamical interplay between coherent single-particle tunneling and nonlinear mean-field interactions opens new perspectives for the study of complex quantum transport with ultracold atoms
Dynamics and thermodynamics of systems with long-range interactions
No full textProperties of systems with long range interactions are still poorly understood despite being of importance in most areas of physics. The present volume introduces and reviews the effort of constructing a coherent thermodynamic treatment of such systems by combining tools from statistical mechanics with concepts and methods from dynamical systems. Analogies and differences between various systems are examined by considering a large range of applications, with emphasis on Bose--Einstein condensates. Written as a set of tutorial reviews, the book will be useful for both the experienced researcher as well as the nonexpert scientist or postgraduate student
Ettore Majorana, Scientific Papers: Festschrift for his 100th Birthday
No full textWith this volume the Italian Physical Society presents a collection of Ettore Majorana's scientific papers (note scientifiche) in the original language and, for the first time - with three exceptions - translated into English. Each paper is then followed by a comment (in English) of an expert in the scientific field. Contributors to the comments are Ennio Arimondo, Nicola Cabibbo, Massimo Inguscio, Luciano Maiani, Rosario Nunzio Mantegna, Francesco Minardi, Luigi Radicati di Brozolo and Antonio Sasso. A century after his birth Ettore Majorana is rightfully considered one of the greatest physicists of the first half of the last century. This volume will be of interest to the specialists of the History of Science and to the physicists concerned with problems related to Majorana's contributionsWith this volume the Italian Physical Society presents a collection of Ettore Majorana's scientific papers (note scientifiche) in the original language and, for the first time - with three exceptions - translated into English. Each paper is then followed by a comment (in English) of an expert in the scientific field. Contributors to the comments are Ennio Arimondo, Nicola Cabibbo, Massimo Inguscio, Luciano Maiani, Rosario Nunzio Mantegna, Francesco Minardi, Luigi Radicati di Brozolo and Antonio Sasso. A century after his birth Ettore Majorana is rightfully considered one of the greatest physicists of the first half of the last century. This volume will be of interest to the specialists of the History of Science and to the physicists concerned with problems related to Majorana's contributions
Angular momentum detection of non-linear phenomena in paramagnetic resonance
No full textThe angular momentum detection of magnetic resonance is examined. Its features are compared to the Einsteinde Haas experiment and its sensitivity is considered with respect to the conventional techniques of the magnetic resonance. Experimental apparatus is presented in detail. Magnetic resonance is examined theoretically and experimentally when low static and strong r. f. fields are applied. Modified Bloch equations are solved at different ordens of approximation to obtain Bloch-Siegert shift, many-photon transitions and superposition effects of resonances at positive and negative static fields. Many-photon transitions by irradiating the sample with two r. f. fields of different frequencies are examined. These transitions are studied theoretically by the Schrodinger equation solution and by the Bloch equations. The appearance of a transversal static magnetization in the magnetic resonance is considered in detail; this non-linear phenomenon is explained solving the modified Bloch equations and by simmetry considerations. Experiments performed on DPPH by the angular momentum detection technique show an excellent agreement with the theoretical results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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