2,131 research outputs found
Detecting topology change via correlations and entanglement from gauge/gravity correspondence
We compute a momentum space version of the entanglement spectrum and
entanglement entropy of general Young tableau states, and one-point functions
on Young tableau states. These physical quantities are used to measure the
topology of the dual spacetime geometries in the context of gauge/gravity
correspondence. The idea that Young tableau states can be obtained by
superposing coherent states is explicitly verified. In this quantum
superposition, a topologically distinct geometry is produced by superposing
states dual to geometries with a trivial topology. Furthermore we have a
refined bound for the overlap between coherent states and the rectangular Young
tableau state, by using the techniques of symmetric groups and representations.
This bound is exponentially suppressed by the total edge length of the Young
tableau. It is also found that the norm squared of the overlaps is bounded
above by inverse powers of the exponential of the entanglement entropies. We
also compute the overlaps between Young tableau states and other states
including squeezed states and multi-mode entangled states which have
similarities with those appeared in quantum information theory.Comment: 48 pages. version in Journal of Mathematical Physic
Adding Logical Operators to Tree Pattern Queries on Graph-Structured Data
As data are increasingly modeled as graphs for expressing complex
relationships, the tree pattern query on graph-structured data becomes an
important type of queries in real-world applications. Most practical query
languages, such as XQuery and SPARQL, support logical expressions using
logical-AND/OR/NOT operators to define structural constraints of tree patterns.
In this paper, (1) we propose generalized tree pattern queries (GTPQs) over
graph-structured data, which fully support propositional logic of structural
constraints. (2) We make a thorough study of fundamental problems including
satisfiability, containment and minimization, and analyze the computational
complexity and the decision procedures of these problems. (3) We propose a
compact graph representation of intermediate results and a pruning approach to
reduce the size of intermediate results and the number of join operations --
two factors that often impair the efficiency of traditional algorithms for
evaluating tree pattern queries. (4) We present an efficient algorithm for
evaluating GTPQs using 3-hop as the underlying reachability index. (5)
Experiments on both real-life and synthetic data sets demonstrate the
effectiveness and efficiency of our algorithm, from several times to orders of
magnitude faster than state-of-the-art algorithms in terms of evaluation time,
even for traditional tree pattern queries with only conjunctive operations.Comment: 16 page
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