1,396 research outputs found

    Towards a Conceptualization of Sociomaterial Entanglement

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    In knowledge representation, socio-technical systems can be modeled as multiagent systems in which the local knowledge of each individual agent can be seen as a context. In this paper we propose formal ontologies as a means to describe the assumptions driving the construction of contexts as local theories and to enable interoperability among them. In particular, we present two alternative conceptualizations of the notion of sociomateriality (and entanglement), which is central in the recent debates on socio-technical systems in the social sciences, namely critical and agential realism. We thus start by providing a model of entanglement according to the critical realist view, representing it as a property of objects that are essentially dependent on different modules of an already given ontology. We refine then our treatment by proposing a taxonomy of sociomaterial entanglements that distinguishes between ontological and epistemological entanglement. In the final section, we discuss the second perspective, which is more challenging form the point of view of knowledge representation, and we show that the very distinction of information into modules can be at least in principle built out of the assumption of an entangled reality

    Singularities of nn-fold integrals of the Ising class and the theory of elliptic curves

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    We introduce some multiple integrals that are expected to have the same singularities as the singularities of the n n-particle contributions χ(n)\chi^{(n)} to the susceptibility of the square lattice Ising model. We find the Fuchsian linear differential equation satisfied by these multiple integrals for n=1,2,3,4 n=1, 2, 3, 4 and only modulo some primes for n=5 n=5 and 6 6, thus providing a large set of (possible) new singularities of the χ(n)\chi^{(n)}. We discuss the singularity structure for these multiple integrals by solving the Landau conditions. We find that the singularities of the associated ODEs identify (up to n=6n= 6) with the leading pinch Landau singularities. The second remarkable obtained feature is that the singularities of the ODEs associated with the multiple integrals reduce to the singularities of the ODEs associated with a {\em finite number of one dimensional integrals}. Among the singularities found, we underline the fact that the quadratic polynomial condition 1+3w+4w2=0 1+3 w +4 w^2 = 0, that occurs in the linear differential equation of χ(3) \chi^{(3)}, actually corresponds to a remarkable property of selected elliptic curves, namely the occurrence of complex multiplication. The interpretation of complex multiplication for elliptic curves as complex fixed points of the selected generators of the renormalization group, namely isogenies of elliptic curves, is sketched. Most of the other singularities occurring in our multiple integrals are not related to complex multiplication situations, suggesting an interpretation in terms of (motivic) mathematical structures beyond the theory of elliptic curves.Comment: 39 pages, 7 figure

    Evidence for the Role of Instantons in Hadron Structure from Lattice QCD

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    Cooling is used as a filter on a set of gluon fields sampling the Wilson action to selectively remove essentially all fluctuations of the gluon field except for the instantons. The close agreement between quenched lattice QCD results with cooled and uncooled configurations for vacuum correlation functions of hadronic currents and for density-density correlation functions in hadronic bound states provides strong evidence for the dominant role of instantons in determining light hadron structure and quark propagation in the QCD vacuum.Comment: 26 pages in REVTeX, plus 10 figures, uuencoded. Submitted to Physical Review D. MIT-CTP-226

    Pion structure from improved lattice QCD: form factor and charge radius at low masses

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    The charge form factor of the pion is calculated in lattice QCD. The non-perturbatively improved Sheikholeslami-Wohlert action is used together with the O(a)\mathcal{O}(a) improved vector current. Other choices for the current are examined. The form factor is extracted for pion masses from 970 MeV down to 360 MeV and for momentum transfers Q22GeV2Q^2 \leq 2 \mathrm{GeV}^2. The mean square charge radius is extracted, compared to previous determinations and its extrapolation to lower masses discussed.Comment: 12 pages REVTeX, 15 figures. Designation of currents clarified. Details concerning extraction of parameters added. Version accepted by Phys. Rev.

    The Strongly Coupled 't Hooft Model on the Lattice

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    We study the strong coupling limit of the one-flavor and two-flavor massless 't Hooft models, largeNclarge-{\cal N}_c-color QCD2QCD_2, on a lattice. We use staggered fermions and the Hamiltonian approach to lattice gauge theories. We show that the one-flavor model is effectively described by the antiferromagnetic Ising model, whose ground state is the vacuum of the gauge model in the infinite coupling limit; expanding around this ground state we derive a strong coupling expansion and compute the lowest lying hadron masses as well as the chiral condensate of the gauge theory. Our lattice computation well reproduces the results of the continuum theory. Baryons are massless in the infinite coupling limit; they acquire a mass already at the second order in the strong coupling expansion in agreement with the Witten argument that baryons are the QCDQCD solitons. The spectrum and chiral condensate of the two-flavor model are effectively described in terms of observables of the quantum antiferromagnetic Heisenberg model. We explicitly write the lowest lying hadron masses and chiral condensate in terms of spin-spin correlators on the ground state of the spin model. We show that the planar limit (Nc{\cal N}_c\longrightarrow \infty) of the gauge model corresponds to the large spin limit (SS\longrightarrow \infty) of the antiferromagnet and compute the hadron mass spectrum in this limit finding that, also in this model, the pattern of chiral symmetry breaking of the continuum theory is well reproduced on the lattice.Comment: LaTex, 25 pages, no figure

    HAEMATOLOGICAL CHANGES INDUCED BY SHORT - TERM EXPOSURE TO COPPER IN THE INDIAN FRESHWATER FISH, NOTOPTERUS NOTOPTERUS (PALLAS)

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    The normal ranges of blood chemistry and the effect of copper sulfate was studied in Indian fresh water fish, Notopterus notopterus. The blood serum biochemical components like, hemoglobin, proteins, urea, urea nitrogen, cholesterol, and glucose levels were determined during the phase of reproductive cycle. Toxic level (LC50) of copper sulfate was found to be 30ppm. Under this concentration (30ppm) after exposure to 96hr the haematological parameters such as glucose, protein, urea, urea nitrogen, cholesterol, creatinine and haemoglobin content were estimated in the blood serum. A significant decrease (p < 0.001) in the biochemical profile such as protein, glucose, urea, urea nitrogen and creatinine were observed; where as haemoglobin (p < 0.001) and cholesterol (p < 0.01) levels in the blood of exposed group was significantly (p < 0.001) higher than that of the control group. The results suggest that the reduction in the above biochemical levels of blood serum may be because of stress due to copper concentration

    Bodies, technologies and action possibilities: when is an affordance?

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    Borrowed from ecological psychology, the concept of affordances is often said to offer the social study of technology a means of re-framing the question of what is, and what is not, ‘social’ about technological artefacts. The concept, many argue, enables us to chart a safe course between the perils of technological determinism and social constructivism. This article questions the sociological adequacy of the concept as conventionally deployed. Drawing on ethnographic work on the ways technological artefacts engage, and are engaged by, disabled bodies, we propose that the ‘affordances’ of technological objects are not reducible to their material constitution but are inextricably bound up with specific, historically situated modes of engagement and ways of life

    Image Classification using Textural Neural Networks

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    This paper presents backpropagation neural networks that utilize texture information to accurately classify photographic images. Training with minimum sets is shown to yield excellent results
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