64,296 research outputs found

    The Simplest Evaluation Measures for XML Information Retrieval that Could Possibly Work

    Get PDF
    This paper reviews several evaluation measures developed for evaluating XML information retrieval (IR) systems. We argue that these measures, some of which are currently in use by the INitiative for the Evaluation of XML Retrieval (INEX), are complicated, hard to understand, and hard to explain to users of XML IR systems. To show the value of keeping things simple, we report alternative evaluation results of official evaluation runs submitted to INEX 2004 using simple metrics, and show its value for INEX

    A Nine Month Report on Progress Towards a Framework for Evaluating Advanced Search Interfaces considering Information Retrieval and Human Computer Interaction

    No full text
    This is a nine month progress report detailing my research into supporting users in their search for information, where the questions, results or even thei

    FRW cosmologies and hyperscaling-violating geometries: higher curvature corrections, ultrametricity, Q-space/QFT duality, and a little string theory

    Full text link
    We analyze flat FRW cosmologies and hyperscaling-violating geometries by emphasizing the analytic continuation between them and their scale covariance. We exhibit two main calculations where this point of view is useful. First, based on the scale covariance, we show that the structure of higher curvature corrections to Einstein's equation is very simple. Second, in the context of accelerated FRW cosmologies, also known as Q-space, we begin by calculating the Bunch-Davies wavefunctional for a massless scalar field and considering its interpretation as a generating functional of correlation functions of a holographic dual. We use this to conjecture a Q-space/QFT duality, a natural extension of dS/CFT, and argue that the Euclidean dual theory violates hyperscaling. This proposal, when extended to epochs in our own cosmological history like matter or radiation domination, suggests a holographically dual description via RG phases which violate hyperscaling. We further use the wavefunctional to compute Anninos-Denef overlaps and show that the ultrametric structure discovered for de Sitter becomes sharper in accelerated FRW cosmologies as the acceleration slows. The substitution dāˆ’āˆ’>deff=dāˆ’Īød --> d_{eff}=d-\theta permeates and illuminates the discussion of wavefunctionals and overlaps in FRW cosmologies, allowing one to predict the sharpened structure. We try to find an alternate manifestation of this ultrametric structure by studying the connection of the Īøāˆ’āˆ’>āˆ’āˆž\theta --> -\infty background to little string theory.Comment: 31 pages plus an appendix; v2 references added; v3 discussion of generalized extreme value distributions added and typos correcte

    Topological M-theory as Unification of Form Theories of Gravity

    Get PDF
    We introduce a notion of topological M-theory and argue that it provides a unification of form theories of gravity in various dimensions. Its classical solutions involve G_2 holonomy metrics on 7-manifolds, obtained from a topological action for a 3-form gauge field introduced by Hitchin. We show that by reductions of this 7-dimensional theory one can classically obtain 6-dimensional topological A and B models, the self-dual sector of loop quantum gravity in 4 dimensions, and Chern-Simons gravity in 3 dimensions. We also find that the 7-dimensional M-theory perspective sheds some light on the fact that the topological string partition function is a wavefunction, as well as on S-duality between the A and B models. The degrees of freedom of the A and B models appear as conjugate variables in the 7-dimensional theory. Finally, from the topological M-theory perspective we find hints of an intriguing holographic link between non-supersymmetric Yang-Mills in 4 dimensions and A model topological strings on twistor space.Comment: 65 pages, 2 figures, harvmac; v2: references added, small corrections/clarification

    Entropy-Area Relations in Field Theory

    Get PDF
    We consider the contribution to the entropy from fields in the background of a curved time-independent metric. To account for the curvature of space, we postulate a position-dependent UV cutoff. We argue that a UV cutoff on energy naturally implies an IR cutoff on distance. With this procedure, we calculate the scalar contribution in a background anti-de Sitter space, the exterior of a black hole, and de Sitter space. In all cases, we find results that can be simply interpreted in terms of local energy and proper volume, yielding insight into the apparent reduced dimensionality of systems with gravity.Comment: 20 pages, 1 figur
    • ā€¦
    corecore