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91.
A 0/±1 matrix is balanced if it does not contain a square submatrix with exactly two nonzero entries per row and per column
in which the sum of all entries is 2 modulo 4. A 0/1 matrix is balanceable if its nonzero entries can be signed ±1 so that
the resulting matrix is balanced. A signing algorithm due to Camion shows that the problems of recognizing balanced 0/±1 matrices
and balanceable 0/1 matrices are equivalent. Conforti, Cornuéjols, Kapoor and Vušković gave an algorithm to test if a 0/±1
matrix is balanced. Truemper has characterized balanceable 0/1 matrices in terms of forbidden submatrices. In this paper we
give an algorithm that explicitly finds one of these forbidden submatrices or shows that none exists.
Received: October 2004 相似文献
92.
Inclusive sum rules for non-abelian symmetry generators and in particular for isospin are studied. A compact formalism is introduced which allows to exaract in a simple way all the consequences of invaraince properties. 相似文献
93.
94.
Angelo Castiglioni und Giacomo Bionda 《Fresenius' Journal of Analytical Chemistry》1954,141(3):189-190
Ohne Zusammenfassung 相似文献
95.
96.
97.
Some aspects of the geometry of gauge theories are sketched in this review. We deal essentially with Yang-Mills theory, discussing the structure of the space of gauge orbits and the geometrical interpretation of ghosts and anomalies. Occasionally we deal also with classical gauge theories of gravitation and in particular we study the action of the group of diffeomorphisms on the space of linear connections. Finally we comment on the mathematical interpretation of anomalies in field theories. 相似文献
98.
Giacomo Bonanno 《Mathematical Logic Quarterly》1996,42(1):305-311
We investigate an axiomatization of the notion of common belief (knowledge) that makes use of no rules of inference (apart from Modus Ponens and Necessitation) and highlight the property of the set of accessibility relations that characterizes each axiom. Mathematics Subject Classification: 03B45, 68T25. 相似文献
99.
The classical SO (3)-invariant σ-model and its suitably generalized versions are studied from the geometrical point of view. Known mathematical results concerning harmonic and holomorphic maps of a Riemann surface into the n-dimensional complex projective space are briefly reviewed. These are used to give a classification of classical solutions (both instantons and a certain subclass of unstable solutions) of Pn models and to study the properties of their energy spectrum. 相似文献
100.
The representations of the Riemann and the Weyl tensors of a four-dimensional Riemannian manifold through covariant derivatives of third-order potentials are examined in detail. The Weyl tensor always admits a completely general representation whereas the Riemann tensor does not. Nevertheless there exists a class of Riemannian manifolds whose Riemann tensors may be calculated in terms of potentials; in this connection, specific examples are exhibited explicitly. The possibility of introducing gauges on the potentials is reexamined in connection with the previous result. New properties of the representations are also discussed. 相似文献