## Graded commutative algebra and related structures in Singular with applications

• This thesis is devoted to constructive module theory of polynomial graded commutative algebras over a field. It treats the theory of Groebner bases (GB), standard bases (SB) and syzygies as well as algorithms and their implementations. Graded commutative algebras naturally unify exterior and commutative polynomial algebras. They are graded non-commutative, associative unital algebras over fields and may contain zero-divisors. In this thesis we try to make the most use out of _a priori_ knowledge about their characteristic (super-commutative) structure in developing direct symbolic methods, algorithms and implementations, which are intrinsic to graded commutative algebras and practically efficient. For our symbolic treatment we represent them as polynomial algebras and redefine the product rule in order to allow super-commutative structures and, in particular, to allow zero-divisors. Using this representation we give a nice characterization of a GB and an algorithm for its computation. We can also tackle central localizations of graded commutative algebras by allowing commutative variables to be _local_, generalizing Mora algorithm (in a similar fashion as G.M.Greuel and G.Pfister by allowing local or mixed monomial orderings) and working with SBs. In this general setting we prove a generalized Buchberger's criterion, which shows that syzygies of leading terms play the utmost important role in SB and syzygy module computations. Furthermore, we develop a variation of the La Scala-Stillman free resolution algorithm, which we can formulate particularly close to our implementation. On the implementation side we have further developed the Singular non-commutative subsystem Plural in order to allow polynomial arithmetic and more involved non-commutative basic Computer Algebra computations (e.g. S-polynomial, GB) to be easily implementable for specific algebras. At the moment graded commutative algebra-related algorithms are implemented in this framework. Benchmarks show that our new algorithms and implementation are practically efficient. The developed framework has a lot of applications in various branches of mathematics and theoretical physics. They include computation of sheaf cohomology, coordinate-free verification of affine geometry theorems and computation of cohomology rings of p-groups, which are partially described in this thesis.

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Verfasserangaben: Oleksandr Motsak urn:nbn:de:hbz:386-kluedo-26479 Gert-Martin Greuel Dissertation Englisch 19.06.2011 2011 Technische Universität Kaiserslautern Technische Universität Kaiserslautern 07.02.2010 20.06.2011 Fachbereich Mathematik 5 Naturwissenschaften und Mathematik / 510 Mathematik 13-XX COMMUTATIVE RINGS AND ALGEBRAS / 13Pxx Computational aspects and applications [See also 14Qxx, 68W30] / 13P10 Gröbner bases; other bases for ideals and modules (e.g., Janet and border bases) 16-XX ASSOCIATIVE RINGS AND ALGEBRAS (For the commutative case, see 13-XX) / 16Wxx Rings and algebras with additional structure / 16W55 "Super" (or "skew") structure [See also 17A70, 17Bxx, 17C70] (For exterior algebras, see 15A75; for Clifford algebras, see 11E88, 15A66) 16-XX ASSOCIATIVE RINGS AND ALGEBRAS (For the commutative case, see 13-XX) / 16Zxx Computational aspects of associative rings / 16Z05 Computational aspects of associative rings [See also 68W30] 68-XX COMPUTER SCIENCE (For papers involving machine computations and programs in a specific mathematical area, see Section {04 in that areag 68-00 General reference works (handbooks, dictionaries, bibliographies, etc.) / 68Wxx Algorithms (For numerical algorithms, see 65-XX; for combinatorics and graph theory, see 05C85, 68Rxx) / 68W30 Symbolic computation and algebraic computation [See also 11Yxx, 12Y05, 13Pxx, 14Qxx, 16Z05, 17-08, 33F10] Standard gemäß KLUEDO-Leitlinien vom 27.05.2011

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