Sökning: "Jan Snellman"

Visar resultat 1 - 5 av 9 avhandlingar innehållade orden Jan Snellman.

1. 1. A graded subring of an inverse limit of polynomial rings

   Författare :Jan Snellman; Jörgen Backelin; Guillermo Moreno Socias; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Gröbner bases; generic forms; inverse limit; Algebra and geometry; Algebra och geometri;

   Sammanfattning : We study the power series ring R= K[[x1,x2,x3,...]]on countably infinitely many variables, over a field K, and two particular K-subalgebras of it: the ring S, which is isomorphic to an inverse limit of the polynomial rings in finitely many variables over K, and the ring R', which is the largest graded subalgebra of R. LÄS MER

3. 2. Centra of Quiver Algebras

   Författare :Elin Gawell; Christian Gottlieb; Qimh Xantcha; Jan Snellman; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; quiver; algebra; commutativity ideal; anti-commutativity ideal; non-commutative; partly commutative; partly anti-commutative; center; Koszul algebra; finitely generated; graded center; Hochschild cohomology; support variety; associative algebra; Mathematics; matematik;

   Sammanfattning : A partly (anti-)commutative quiver algebra is a quiver algebra bound by an (anti-)commutativity ideal, that is, a quadratic ideal generated by monomials and (anti-)commutativity relations. We give a combinatorial description of the ideals and the associated generator graphs, from which one can quickly determine if the ideal is admissible or not. LÄS MER

4. 3. The k-assignment polytope, phylogenetic trees, and permutation patterns

   Författare :Jonna Gill; Jan Snellman; Axel Hultman; Bruce Sagan; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : In this thesis three combinatorial problems are studied in four papers.In Paper 1 we study the structure of the k-assignment polytope, whose vertices are the mxn (0,1)-matrices with exactly k 1:s and at most one 1 in each row and each column. LÄS MER

5. 4. Combinatorics and topology related to involutions in Coxeter groups

   Författare :Mikael Hansson; Axel Hultman; Jan Snellman; Nathan Reading; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : This dissertation consists of three papers in combinatorial Coxeter group theory.A Coxeter group is a group W generated by a set S, where all relations can be derived from the relations s2 = e for all s ? S, and (ss′)m(s,s′) = e for some pairs of generators s ≠ s′ in S, where e ? W is the identity element and m(s, s′) is an integer satisfying that m(s, s′) = m(s′, s) ≥ 2. LÄS MER

7. 5. Generalised Ramsey numbers and Bruhat order on involutions

   Författare :Mikael Hansson; Axel Hultman; Jan Snellman; Jonas Sjöstrand; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

   Sammanfattning : This thesis consists of two papers within two different areas of  combinatorics.Ramsey theory is a classic topic in graph theory, and Paper A deals with two of its most fundamental problems: to compute Ramsey numbers and to characterise critical graphs. More precisely, we study generalised Ramsey numbers for two sets Γ1 and Γ2 of cycles. LÄS MER