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921.
To overcome known disadvantages in the use of singly-implicit methods in the solution of stiff differential equations, two
generalizations have been recently introduced. These are the use of additional diagonally-implicit stages and the use of effective
order as a weakening of the conditions on the method. In this paper, these two generalizations are combined into a unified
scheme. The resulting DESIRE methods are very promising alternatives to standard methods for solving stiff problems.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
922.
Venkata Balaji Thiruvalloor Eesanaipaadi 《Journal of Pure and Applied Algebra》2007,208(1):237-259
We study degenerations of rank 3 quadratic forms and of rank 4 Azumaya algebras, and extend what is known for good forms and Azumaya algebras. By considering line-bundle-valued forms, we extend the theorem of Max-Albert Knus that the Witt-invariant—the even Clifford algebra of a form—suffices for classification. An algebra Zariski-locally the even Clifford algebra of a ternary form is so globally up to twisting by square roots of line bundles. The general, usual and special orthogonal groups of a form are determined in terms of automorphism groups of its Witt-invariant. Martin Kneser’s characteristic-free notion of semiregular form is used. 相似文献
923.
Kyusik Hong 《Journal of Pure and Applied Algebra》2007,208(1):361-369
We study when double covers of P3 ramified along nodal surfaces are not Q-factorial. In particular, we describe all the Q-factorial double covers of P3 ramified along quartic surfaces with at most seven simple double points and sextic surfaces with at most 16 simple double points. 相似文献
924.
We study the potential density of rational points on double solids ramified along singular reduced sextic surfaces. Also, we investigate elliptic fibration structures on nonsingular sextic double solids defined over a perfect field of characteristic 5. 相似文献
925.
The first author was supported in part by CNPq 相似文献
926.
We prove the conjecture of Falikman-Friedland-Loewy on the parity of the degrees of projective varieties of n×n complex symmetric matrices of rank at most k. We also characterize the parity of the degrees of projective varieties of n×n complex skew symmetric matrices of rank at most 2p. We give recursive relations which determine the parity of the degrees of projective varieties of m×n complex matrices of rank at most k. In the case the degrees of these varieties are odd, we characterize the minimal dimensions of subspaces of n×n skew symmetric real matrices and of m×n real matrices containing a nonzero matrix of rank at most k. The parity questions studied here are also of combinatorial interest since they concern the parity of the number of plane partitions contained in a given box, on the one hand, and the parity of the number of symplectic tableaux of rectangular shape, on the other hand. 相似文献
927.
928.
Olivier Piltant 《Mathematische Annalen》1995,303(1):435-456
Sans résumé
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929.
930.