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147
Antisymmetric Flows and Strong Oriented Coloring of Planar Graphs
, 2002
"... In [NR] Nesetril and Raspaud defined antisymmetric flow, which is a variant of nowhere zero flow, and the dual notion to strong oriented coloring. We give an upper bound on the number of colors needed to a strong oriented coloring of a planar graph, and hereby we find a small antisymmetric ow for an ..."
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Cited by 3 (0 self)
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In [NR] Nesetril and Raspaud defined antisymmetric flow, which is a variant of nowhere zero flow, and the dual notion to strong oriented coloring. We give an upper bound on the number of colors needed to a strong oriented coloring of a planar graph, and hereby we find a small antisymmetric ow
Generalized DavenportSchinzel Sequences
, 1993
"... The extremal function Ex(u; n) (introduced in the theory of DavenportSchinzel sequences in other notation) denotes for a fixed finite alternating sequence u = ababa : : : the maximum length of a finite sequence v over n symbols with no immediate repetition which does not contain u. Here (following ..."
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Cited by 23 (4 self)
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the idea of J. Nesetril) we generalize this concept for arbitrary sequence u. We summarize the already known properties of Ex(u; n) and we present also two new theorems which give good upper bounds on Ex(u; n) for u consisting of (two) smaller subsequences u i provided we have good upper bounds on Ex(u i
Constraint Satisfaction with Countable Homogeneous Templates
 IN PROCEEDINGS OF CSL’03
, 2003
"... For a fixed countable homogeneous structure we study the computational problem whether a given finite structure of the same relational signature homomorphically maps to . This problem is known as the constraint satisfaction problem CSP( ) for and was intensively studied for finite . We show that ..."
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Cited by 42 (19 self)
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For a fixed countable homogeneous structure we study the computational problem whether a given finite structure of the same relational signature homomorphically maps to . This problem is known as the constraint satisfaction problem CSP( ) for and was intensively studied for finite . We show that  as in the case of finite  the computational complexity of CSP( ) for countable homogeneous is determinded by the clone of polymorphisms of . To this end we prove the following theorem which is of independent interest: The primitive positive definable relations over an !categorical structure are precisely the relations that are invariant under the polymorphisms of .
A COMBINATORIAL CONSTRAINT SATISFACTION PROBLEM DICHOTOMY CLASSIFICATION CONJECTURE
"... We further generalise a construction – the fibre construction – that was developed in an earlier paper of the first two authors. The extension in this paper gives a polynomialtime reduction of CSP(H) for any relational system H to CSP(P) for any relational system P that meets a certain technical pa ..."
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Cited by 3 (0 self)
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, we reduce the FederHellHuang conjecture to the CSP dichotomy classification conjecture, and we prove the KostochkaNesetrilSmolíková conjecture. Although these results were proved independently by Jonsson et. al. and Kun respectively, we give different, shorter, proofs.
The complexity of Hcolouring of bounded degree graphs
 DISCRETE MATH
, 1998
"... We investigate the complexity of the hcolouring problem, and, more generally, of the Hcolouring problem, restricted to graphs of bounded degree. While the general problems are almost always NPcomplete, we present some surprising polynomial algorithms for several of these restricted colouring prob ..."
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Cited by 12 (5 self)
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We investigate the complexity of the hcolouring problem, and, more generally, of the Hcolouring problem, restricted to graphs of bounded degree. While the general problems are almost always NPcomplete, we present some surprising polynomial algorithms for several of these restricted colouring problems. We also give a number of NPcompleteness results, and pose some open problems. One of these may be viewed as the complement of an algorithmic version of the theorem of Brooks.
INDEPENDENT SET and CLIQUE problems intersectiondefined classes of graphs
 COMMENTATIONES MATHEMATICAE UNIVERSITATIS CAROLINAE
, 1990
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Antisymmetric Flows in Matroids
 EUROPEAN JOURNAL OF COMBINATORICS
, 2006
"... We present a seemingly new definition of flows and flow numbers in oriented matroids and prove that the flow number and the antisymmetric flow number are bounded with the rank. In particular we show that any orientable matroid has an antisymmetric 3 # #r(E)+1 flow. ..."
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Cited by 3 (2 self)
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We present a seemingly new definition of flows and flow numbers in oriented matroids and prove that the flow number and the antisymmetric flow number are bounded with the rank. In particular we show that any orientable matroid has an antisymmetric 3 # #r(E)+1 flow.
Results 1  10
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147