Studying Parallel Evolutionary Algorithms: The cellular Programming Case

Parallel evolutionary algorithms, studied to some extent over the past few years, have proven empirically worthwhile—though there seems to be lacking a better understanding of their workings. In this paper we concentrate on cellular (fine-grained) models, presenting a number of statistical measures, both at the genotypic and phenotypic levels. We demonstrate the application and utility of these measures on a specific example, that of the cellular programming evolutionary algorithm, when used to evolve solutions to a hard problem in the cellular-automata domain, known as synchronization

Signatures of non-locality in the first-order coherence of the scattered light

The spatial coherence of an atomic wavepacket can be detected in the scattered photons, even when the center-of-mass motion is in the quantum coherent superposition of two distant, non-overlapping wave packets. Spatial coherence manifests itself in the power spectrum of the emitted photons, whose spectral components can exhibit interference fringes as a function of the emission angle. The contrast and the phase of this interference pattern provide information about the quantum state of the center of mass of the scattering atom.Comment: 5 pages, one figure, submitted to Laser Physics, special issue in memory of Herbert Walthe

A Method for Modeling Decoherence on a Quantum Information Processor

We develop and implement a method for modeling decoherence processes on an N-dimensional quantum system that requires only an $N^2$-dimensional quantum environment and random classical fields. This model offers the advantage that it may be implemented on small quantum information processors in order to explore the intermediate regime between semiclassical and fully quantum models. We consider in particular $\sigma_z\sigma_z$ system-environment couplings which induce coherence (phase) damping, though the model is directly extendable to other coupling Hamiltonians. Effective, irreversible phase-damping of the system is obtained by applying an additional stochastic Hamiltonian on the environment alone, periodically redressing it and thereby irreversibliy randomizing the system phase information that has leaked into the environment as a result of the coupling. This model is exactly solvable in the case of phase-damping, and we use this solution to describe the model's behavior in some limiting cases. In the limit of small stochastic phase kicks the system's coherence decays exponentially at a rate which increases linearly with the kick frequency. In the case of strong kicks we observe an effective decoupling of the system from the environment. We present a detailed implementation of the method on an nuclear magnetic resonance quantum information processor.Comment: 12 pages, 9 figure

Decoherence via Dynamical Casimir Effect

We derive a master equation for a mirror interacting with the vacuum field via radiation pressure. The dynamical Casimir effect leads to decoherence of a 'Schroedinger cat' state in a time scale that depends on the degree of 'macroscopicity' of the state components, and which may be much shorter than the relaxation time scale. Coherent states are selected by the interaction as pointer states.Comment: 4 pages, 2 figure

Decoherence, Chaos, and the Second Law

We investigate implications of decoherence for quantum systems which are classically chaotic. We show that, in open systems, the rate of von Neumann entropy production quickly reaches an asymptotic value which is: (i) independent of the system-environment coupling, (ii) dictated by the dynamics of the system, and (iii) dominated by the largest Lyapunov exponent. These results shed a new light on the correspondence between quantum and classical dynamics as well as on the origins of the ``arrow of time.''Comment: 13 Pages, 2 Figures available upon request, Preprint LA-UR-93-, The new version contains the text, the previous one had only the Macros: sorry

Subleading Jet Functions in Inclusive B Decays

The contribution of subleading jet functions to inclusive decay distributions of $B$ mesons are derived from a systematic two-step matching of QCD current correlators onto soft collinear and heavy quark effective theory. Focusing on the tree level matching of QCD onto soft collinear effective theory, the subleading jet functions are defined to all orders in $\alpha_s(\mu_i)$ (with $\mu_i^2\sim m_b\Lambda_{\rm QCD}$) and are calculated explicitly at first order in $\alpha_s(\mu_i)$. We present explicit expressions for the decay rates of $B\to X_u l \bar\nu$ and the $Q_{7\gamma}-Q_{7\gamma}$ contribution to $B\to X_s \gamma$, where the subleading jet functions are multiplied by a tree level hard function and appear in a convolution with the leading order shape function. Together with the recent two loop calculation of the leading order hard function for $B\to X_u l \bar\nu$, this paper will allow for a more precise description of inclusive B decays in the end point region.Comment: Minor changes: reference added, typos corrected, journal versio

Radiation Pressure as a Source of Decoherence

We consider the interaction of an harmonic oscillator with the quantum field via radiation pressure. We show that a `Schrodinger cat' state decoheres in a time scale that depends on the degree of `classicality' of the state components, and which may be much shorter than the relaxation time scale associated to the dynamical Casimir effect. We also show that decoherence is a consequence of the entanglement between the quantum states of the oscillator and field two-photon states. With the help of the fluctuation-dissipation theorem, we derive a relation between decoherence and damping rates valid for arbitrary values of the temperature of the field. Coherent states are selected by the interaction as pointer states.Comment: 14 pages, 3 figures, RevTex fil

Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10

Infrared observations from the Spitzer Space Telescope archive are used to study the dust component of the interstellar medium in the IC~10 irregular galaxy. Dust distribution in the galaxy is compared to the distributions of H$\alpha$ and [SII] emission, neutral hydrogen and CO clouds, and ionizing radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH) in the galaxy is shown to be highly non-uniform with the mass fraction of these particles in the total dust mass reaching 4%. PAHs tend to avoid bright HII regions and correlate well with atomic and molecular gas. This pattern suggests that PAHs form in the dense interstellar gas. We propose that the significant decrease of the PAH abundance at low metallicity is observed not only globally (at the level of entire galaxies), but also locally (at least, at the level of individual HII regions). We compare the distribution of the PAH mass fraction to the distribution of high-velocity features, that we have detected earlier in wings of H$\alpha$ and SII lines, over the entire available galaxy area. No conclusive evidence for shock destruction of PAHs in the IC~10 galaxy could be found.Comment: Accepted for publication in Astronomy Report

‘Clinics aren’t meant for men’: Sexual health care access and seeking behaviours among men in Gauteng province, South Africa

Men may be key players in the transmission of sexually transmitted infections (STI), and it is important that STI/HIV health services reach men. The objective of this study was to explore sexual health care access and seeking behaviours in men. This study used focus groups to examine sexual health care access and seeking behaviours in men 5 years after implementation of free antiretroviral therapy (ART) in the South African public sector. Six focus groups (N=58) were conducted with men ≥18 years in an urban area of Gauteng province. Men were recruited from various locations throughout the community. Men reported several barriers and facilitators to the use of public and private clinics for sexual health services including HIV testing, and many men reported seeking care from traditional healers. Men often viewed public clinics as a place for women and reported experiences with some female nurses who were rude or judgmental of the men. Additionally, some men reported that they sought sexual health care services at public clinics; however, they were not given physical examinations by health care providers to diagnose their STI syndrome. Most men lacked knowledge about ART and avoided HIV testing because of fear of death or being abandoned by their families or friends. Study findings suggest that men still require better access to high-quality, non-judgmental sexual health care services. Future research is needed to determine the most effective method to increase men’s access to sexual health care services.Keywords: sexual health care access, men.Les hommes peuvent être des responsables dans la transmission des infections sexuellement transmissibles (IST), et il est important que les services de santé des IST/VIH les sensibilisent (les hommes). Les objectifs de cette étude étaient d’examiner l’accès aux soins de santé et les comportements sexuels des hommes pendant 5 ans après la mise en oeuvre de la thérapie antirétrovirale (ART) gratuite dans le secteur public Sud-Africain. Six groups d’hommes âgés ≥18 ans (N=58) ont menés des discussions dans la zone urbaine de la province de Gauteng. Ces hommes sont recrutés dans divers endroits dans toute la communauté. Ils ont déclarés rencontrés des obstacles et facilitateurs à l’accès des cliniques publiques et privées des services de santé sexuelle, y compris le test du VIH, et beaucoup d’hommes déclarent être à la recherche de soins vers des guérisseurs traditionnels. Les hommes ont souvent vu les cliniques publiques comme des endroits pour les femmes et se sont souvent plaint des expériences qu’ils ont eues par rapport aux infirmières qui ont un mauvais jugement sur eux. Certains d’entre eux ont déclaré qu’ils cherchaient des soins de santé dans les cliniques publiques, mais qu’ils n’étaient pas soumis à des examens physiques pour diagnostiquer leurs syndrome d’IST. La plupart d’entre eux n’avaient pas de connaissances de l’ART et évitent le test du VIH parce qu’ils ont peur de la mort ou d’être abandonné par leurs familles ou leurs amis. Cette étude suggère que les hommes doivent exiger de meilleures qualités de soins, un non-jugement des services de santé sexuelle. Les recherches futures sont nécessaires pour déterminer la méthode la plus efficace d’accroitre l’accès des hommes aux services de santé sexuelle

Star formation in the nearby universe: the ultraviolet and infrared points of view

This work presents the main ultraviolet (UV) and far-infrared (FIR) properties of two samples of nearby galaxies selected from the GALEX ($\lambda = 2315$\AA, hereafter NUV) and IRAS ($\lambda = 60\mu$m) surveys respectively. They are built in order to get detection at both wavelengths for most of the galaxies. Star formation rate (SFR) estimators based on the UV and FIR emissions are compared. Systematic differences are found between the SFR estimators for individual galaxies based on the NUV fluxes corrected for dust attenuation and on the total IR luminosity. A combined estimator based on NUV and IR luminosities seems to be the best proxy over the whole range of values of SFR. Although both samples present similar average values of the birthrate parameter b, their star-formation-related properties are substantially different: NUV-selected galaxies tend to show larger values of $b$ for lower masses, SFRs and dust attenuations, supporting previous scenarios for the star formation history (SFH). Conversely, about 20% of the FIR-selected galaxies show high values of $b$, SFR and NUV attenuation. These galaxies, most of them being LIRGs and ULIRGs, break down the downsizing picture for the SFH, however their relative contribution per unit volume is small in the local Universe. Finally, the cosmic SFR density of the local Universe is estimated in a consistent way from the NUV and IR luminosities.Comment: 43 pages, 13 figures, accepted for publication in Astrophysical Journal Supplement Serie