3,984 research outputs found

    Diversity of graphs with highly variable connectivity

    Get PDF
    A popular approach for describing the structure of many complex networks focuses on graph theoretic properties that characterize their large-scale connectivity. While it is generally recognized that such descriptions based on aggregate statistics do not uniquely characterize a particular graph and also that many such statistical features are interdependent, the relationship between competing descriptions is not entirely understood. This paper lends perspective on this problem by showing how the degree sequence and other constraints (e.g., connectedness, no self-loops or parallel edges) on a particular graph play a primary role in dictating many features, including its correlation structure. Building on recent work, we show how a simple structural metric characterizes key differences between graphs having the same degree sequence. More broadly, we show how the (often implicit) choice of a background set against which to measure graph features has serious implications for the interpretation and comparability of graph theoretic descriptions

    Alternative Route to Strong Interaction: Narrow Feshbach Resonance

    Full text link
    We show that a narrow resonance produces strong interaction effects far beyond its width on the side of the resonance where the bound state has not been formed. This is due to a resonance structure of its phase shift, which shifts the phase of a large number of scattering states by π\pi before the bound state emerges. As a result, the magnitude of the interaction energy when approaching the resonance on the "upper" and "lower" branch from different side of the resonance is highly asymmetric, unlike their counter part in wide resonances. Measurements of these effects are experimentally feasible.Comment: 4 pages, 5 figure

    Implications of 3-step swimming patterns in bacterial chemotaxis

    Full text link
    We recently found that marine bacteria Vibrio alginolyticus execute a cyclic 3-step (run- reverse-flick) motility pattern that is distinctively different from the 2-step (run-tumble) pattern of Escherichia coli. How this novel swimming pattern is regulated by cells of V. alginolyticus is not currently known, but its significance for bacterial chemotaxis is self- evident and will be delineated herein. Using an approach introduced by de Gennes, we calculated the migration speed of a cell executing the 3-step pattern in a linear chemical gradient, and found that a biphasic chemotactic response arises naturally. The implication of such a response for the cells to adapt to ocean environments and its possible connection to E. coli 's response are also discussed.Comment: 18 pages, 4 figures, submitted to biophysical journa

    The Unremarkable Things Matter: A Book Review of David Silverman\u27s A Very Short, Fairly Interesting and Reasonably Cheap Book about Qualitative Research (2nd ed.)

    Get PDF
    In this review of the book, A Very Short, Fairly Interesting and Reasonably Cheap Book about Qualitative Research by David Silverman, I write from the perspectives following Silverman’s arguments about “unremarkable things matter” in qualitative research. Based on his inspiring thoughts on modern qualitative research, I also express my reflective ideas as a doctoral student

    Bose Gases Near Unitarity

    Full text link
    We study the properties of strongly interacting Bose gases at the density and temperature regime when the three-body recombination rate is substantially reduced. In this regime, one can have a Bose gas with all particles in scattering states (i.e. the "upper branch") with little loss even at unitarity over the duration of the experiment. We show that because of bosonic enhancement, pair formation is shifted to the atomic side of the original resonance (where scattering length as<0a_s<0), opposite to the fermionic case. In a trap, a repulsive Bose gas remains mechanically stable when brought across resonance to the atomic side until it reaches a critical scattering length as<0a_{s}^{\ast}<0. For as<asa_s<a_{s}^{\ast}, the density consists of a core of upper branch bosons surrounded by an outer layer of equilibrium phase. The conditions of low three-body recombination requires that the particle number N<α(T/ω)5/2N<\alpha (T/\omega)^{5/2} in a harmonic trap with frequency ω\omega, where α\alpha is a constant.Comment: 4 pages, 4 figure
    corecore