Persistence of mean-field features in the energy spectrum of small arrays of Bose-Einstein condensates

The Bose-Hubbard Hamiltonian capturing the essential physics of the arrays of interacting Bose-Einstein condensates is addressed, focusing on arrays consisting of two (dimer) and three (trimer) sites. In the former case, some results concerning the persistence of mean-field features in the energy spectrum of the symmetric dimer are extended to the asymmetric version of the system, where the two sites are characterized by different on-site energies. Based on a previous systematic study of the mean-field limit of the trimer, where the dynamics is exhaustively described in terms of its fixed points for every choice of the significant parameters, an interesting mapping between the dimer and the trimer is emphasized and used as a guide in investigating the persistence of mean-field features in the rather complex energy spectrum of the trimer. These results form the basis for the systematic investigation of the purely quantum trimer extending and completing the existing mean-field analysis. In this respect we recall that, similar to larger arrays, the trimer is characterized by a non-integrable mean-field dynamics featuring chaotic trajectories. Hence, the correspondence between mean-field fixed points and quantum energy levels emphasized in the present work may provide a key to investigate the quantum counterpart of classical instability.Comment: 12 pages, 6 figures, to appear on Journal of Physics B (Special Issue: Levico BEC workshop). Publication status update

Spectral Statistics of the Triaxial Rigid Rotator: Semiclassical Origin of their Pathological Behavior

In this paper we investigate the local and global spectral properties of the triaxial rigid rotator. We demonstrate that, for a fixed value of the total angular momentum, the energy spectrum can be divided into two sets of energy levels, whose classical analog are librational and rotational motions. By using diagonalization, semiclassical and algebric methods, we show that the energy levels follow the anomalous spectral statistics of the one-dimensional harmonic oscillator.Comment: 14 pages with 5 figures, to be published in Int. J. Mod. Phys.

Long Range Anticorrelations and Non-Gaussian Behavior of a Leaky Faucet

We find that intervals between successive drops from a leaky faucet display scale-invariant, long-range anticorrelations characterized by the same exponents of heart beat-to-beat intervals of healthy subjects. This behavior is also confirmed by numerical simulations on lattice and it is faucet-width- and flow-rate-independent. The histogram for the drop intervals is also well described by a L\'evy distribution with the same index for both histograms of healthy and diseased subjects. This additional result corroborates the evidence for similarities between leaky faucets and healthy hearts underlying dynamics.Comment: Self-extracting uuencoded postscript file. Phys.Rev.E (Rap.Comm.). Related papers can be found at http://www.if.uff.br/~tjpp/tjppe.htm

Topology-induced confined superfluidity in inhomogeneous arrays

We report the first study of the zero-temperature phase diagram of the Bose-Hubbard model on topologically inhomogeneous arrays. We show that the usual Mott-insulator and superfluid domains, in the paradigmatic case of the comb lattice, are separated by regions where the superfluid behaviour of the bosonic system is confined along the comb backbone. The existence of such {\it confined superfluidity}, arising from topological inhomogeneity, is proved by different analytical and numerical techniques which we extend to the case of inhomogeneous arrays. We also discuss the relevance of our results to real system exhibiting macroscopic phase coherence, such as coupled Bose condensates and Josephson arrays.Comment: 6 pages, 4 figures, final versio

Near-infrared photoluminescence of erbium tris(8-hydroxyquinoline) spin-coated thin films induced by low coherence light sources

Copyright 2007 AIP Publishing LLC. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Applied Physics Letters [91, 021106 (2007)] and may be found at

The co-evolution of societal issues, technologies and industry regimes: three case studies of the American automobile industry

This thesis contributes to closing a gap in the field of science, technology and innovation (STI) policy research: despite many theoretical advances in the field, we still do not know why some urgent societal issues (or ‘challenges’) remain unaddressed, notwithstanding the technological advances that could potentially address them. In particular, radical technological innovations – innovations that depart from the established technological trajectory – would offer greatest potential to address societal challenges. While the source of radical innovations is often new entrepreneurial firms, established firms (‘incumbents’) are likely to play an important role in developing them because of the vast resources and complementary assets they possess. Incumbents however, face few immediate incentives to develop radical innovations in response to societal challenges. The analytical puzzle of this thesis is thus to explain how, when, and why industries change (or not) their strategies (in particular, their technological strategy) in order to address a societal problem. This puzzle is disentangled into interrelated research questions: A) How do societal issue­‐related pressures (on the incumbent industry) from different domains (namely, civil society, science, political arena, economy) evolve? B) How does the incumbent industry respond to changing pressures around societal issues, in terms of technological, political, cultural and economic strategies? C) In particular, when and why do industry actors decide to develop substantive technological responses? To answer these questions, the thesis develops a new analytical perspective that combines insights from (a) issue life­‐cycle and issue attention cycle theories (from the Business & Society field) with (b) the so­‐called ‘Triple Embeddedness Framework’ and (c) concepts from business strategies, innovation management, corporate political strategies, and technology policy. This novel perspective represents an ideal­‐typical model of issue evolution (‘issue life ­‐cycle’). The model, which I call the Dialectic Issue Life­‐Cycle (DILC) model, is applied to three case studies of the American automobile industry’s responses to various societal problems (local air pollution, auto and highway safety, and climate change). Combining qualitative and quantitative research methods in an original way, the case studies aim not only to investigate the validity of the framework, which also provides conceptual answers to the research questions, but also to further refine it and nuance the conceptual answers. By explaining how incumbent industry actors respond to societal challenges, this thesis ultimately contributes to the practical policy debate of how incumbents can be stimulated to develop radical innovations that help address societal challenges