1,404 research outputs found
Off-Diagonal Long-Range Order, Restricted Gauge Transformations, and Aharonov-Bohm Effect in Conductors
The Hamiltonian describing a conductor surrounding an external magnetic field
contains a nonvanishing vector potential in the volume accessible to the
electrons and nuclei of which the conductor is made. That vector potential
cannot be removed by a gauge transformation. Nevertheless, a macroscopic normal
conductor can experience no Aharonov-Bohm effect. That is proved by assuming
only that a normal conductor lacks off-diagonal long-range order (ODLRO). Then
by restricting the Hilbert space to density matrices which lack ODLRO, it is
possible to introduce a restricted gauge transformation that removes the
interaction of the conductor with the vector potential.Comment: Editing errors are corrected. One was slightly misleadin
Structure induction by lossless graph compression
This work is motivated by the necessity to automate the discovery of
structure in vast and evergrowing collection of relational data commonly
represented as graphs, for example genomic networks. A novel algorithm, dubbed
Graphitour, for structure induction by lossless graph compression is presented
and illustrated by a clear and broadly known case of nested structure in a DNA
molecule. This work extends to graphs some well established approaches to
grammatical inference previously applied only to strings. The bottom-up graph
compression problem is related to the maximum cardinality (non-bipartite)
maximum cardinality matching problem. The algorithm accepts a variety of graph
types including directed graphs and graphs with labeled nodes and arcs. The
resulting structure could be used for representation and classification of
graphs.Comment: 10 pages, 7 figures, 2 tables published in Proceedings of the Data
Compression Conference, 200
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