36,597 research outputs found

    Infinite primitive and distance transitive directed graphs of finite out-valency

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    We give certain properties which are satisfied by the descendant set of a vertex in an infinite, primitive, distance transitive digraph of finite out-valency and provide a strong structure theory for digraphs satisfying these properties. In particular, we show that there are only countably many possibilities for the isomorphism type of such a descendant set, thereby confirming a conjecture of the first Author. As a partial converse, we show that certain related conditions on a countable digraph are sufficient for it to occur as the descendant set of a primitive, distance transitive digraph

    Classification of some countable descendant-homogeneous digraphs

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    For finite q, we classify the countable, descendant-homogeneous digraphs in which the descendant set of any vertex is a q-valent tree. We also give conditions on a rooted digraph G which allow us to construct a countable descendant-homogeneous digraph in which the descendant set of any vertex is isomorphic to G.Comment: 16 page

    Theodora Skipitares’s textual bodies

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    Theodora Skipitares’s textual bodies

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    Accepted manuscrip

    Here comes the sun: the promise of solar energy

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    George Harrison, the youngest Beatle, wrote the classic “Here Comes the Sun” in 1969 after spending a glorious day walking around his friend Eric Clapton’s garden. Today, Harrison’s refrain, “And I say, ‘It’s All right’,” accords well with a solar power industry that has grown more than 30 percent in the past six years and received tax-favorable legislative approval in 2006

    Antiquities Theft: The Role of the Museum in Modern Symbolic Violence

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    Humans have been collecting artifacts for centuries, whether it is for their aesthetic value or for the acquisition of knowledge. However, these artifacts have, in most cases, been taken without permission from the countries of origin. Today, museums are struggling with the issue of repatriation and many refuse to return their priceless possessions. Western museums and their supporters are arguing that repatriation will put the artifacts in danger and hurt the chances for humanity to learn from them. The arguments of these museums are an attempt of symbolic violence on non-Western nations, who are seen as unfit or unable to care for their own history

    Optimality in Goal-Dependent Analysis of Sharing

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    We face the problems of correctness, optimality and precision for the static analysis of logic programs, using the theory of abstract interpretation. We propose a framework with a denotational, goal-dependent semantics equipped with two unification operators for forward unification (calling a procedure) and backward unification (returning from a procedure). The latter is implemented through a matching operation. Our proposal clarifies and unifies many different frameworks and ideas on static analysis of logic programming in a single, formal setting. On the abstract side, we focus on the domain Sharing by Jacobs and Langen and provide the best correct approximation of all the primitive semantic operators, namely, projection, renaming, forward and backward unification. We show that the abstract unification operators are strictly more precise than those in the literature defined over the same abstract domain. In some cases, our operators are more precise than those developed for more complex domains involving linearity and freeness. To appear in Theory and Practice of Logic Programming (TPLP
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