484 research outputs found

    On the vanishing of negative K-groups

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    Let k be an infinite perfect field of positive characteristic p and assume that strong resolution of singularities holds over k. We prove that, if X is a d-dimensional noetherian scheme whose underlying reduced scheme is essentially of finite type over the field k, then the negative K-group K_q(X) vanishes for every q < -d. This partially affirms a conjecture of Weibel.Comment: Math. Ann. (to appear

    Cohomological Hasse principle and motivic cohomology for arithmetic schemes

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    In 1985 Kazuya Kato formulated a fascinating framework of conjectures which generalizes the Hasse principle for the Brauer group of a global field to the so-called cohomological Hasse principle for an arithmetic scheme. In this paper we prove the prime-to-characteristic part of the cohomological Hasse principle. We also explain its implications on finiteness of motivic cohomology and special values of zeta functions.Comment: 47 pages, final versio

    Effective and Efficient Similarity Index for Link Prediction of Complex Networks

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    Predictions of missing links of incomplete networks like protein-protein interaction networks or very likely but not yet existent links in evolutionary networks like friendship networks in web society can be considered as a guideline for further experiments or valuable information for web users. In this paper, we introduce a local path index to estimate the likelihood of the existence of a link between two nodes. We propose a network model with controllable density and noise strength in generating links, as well as collect data of six real networks. Extensive numerical simulations on both modeled networks and real networks demonstrated the high effectiveness and efficiency of the local path index compared with two well-known and widely used indices, the common neighbors and the Katz index. Indeed, the local path index provides competitively accurate predictions as the Katz index while requires much less CPU time and memory space, which is therefore a strong candidate for potential practical applications in data mining of huge-size networks.Comment: 8 pages, 5 figures, 3 table

    On the Whitehead spectrum of the circle

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    The seminal work of Waldhausen, Farrell and Jones, Igusa, and Weiss and Williams shows that the homotopy groups in low degrees of the space of homeomorphisms of a closed Riemannian manifold of negative sectional curvature can be expressed as a functor of the fundamental group of the manifold. To determine this functor, however, it remains to determine the homotopy groups of the topological Whitehead spectrum of the circle. The cyclotomic trace of B okstedt, Hsiang, and Madsen and a theorem of Dundas, in turn, lead to an expression for these homotopy groups in terms of the equivariant homotopy groups of the homotopy fiber of the map from the topological Hochschild T-spectrum of the sphere spectrum to that of the ring of integers induced by the Hurewicz map. We evaluate the latter homotopy groups, and hence, the homotopy groups of the topological Whitehead spectrum of the circle in low degrees. The result extends earlier work by Anderson and Hsiang and by Igusa and complements recent work by Grunewald, Klein, and Macko.Comment: 52 page

    Psychoneuroendocrine evaluation of an acceptance and commitment based stress management training

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    Acceptance and Commitment Therapy (ACT), a behavioral therapy that targets psychological flexibility (PF), has been shown to be efficacious across a wide range of problems, including chronic work-related stress and perceived stress. ACT's effect on the multiple levels of the acute stress response (i.e., subjective and biological) is less well understood. The aim of the current study was to test whether ACT, by working toward PF, would reduce both the endocrine and subjective evaluations of participants' acute stress response.; Participants (n = 35) were randomized to an ACT condition or waitlist (WL). Participants in the ACT condition received a two-day ACT workshop on how to flexibly deal with stress. All participants completed a standardized laboratory stress test.; The ACT and WL groups did not differ on main comparisons of the endocrine response (i.e., cortisol) or subjective evaluation. Baseline levels of PF moderated some outcomes. Avoidant participants had a stronger endocrine stress reaction if they received the ACT intervention.; The control condition was a WL and not an active intervention comparison.; ACT is not useful in reducing the acute stress response and may even be iatrogenic, at least during tasks with little real-world impact for their personal values
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