Algorithmic solution of extremal digraph problems
نویسندگان
چکیده
منابع مشابه
Algorithmic Solution of Extremal Digraph Problems1
For a given family JC of digraphs, we study the "extremal" digraphs on n vertices containing no member of JC, and having the maximum number of arcs, e\(n,^f). We resolve conjectures concerning the set {lim,, ^x (ex(n,JC )/n2)) as JC ranges over all possible families, and describe a "finite" algorithm that can determine, for any JC, all matrices A for which a sequence {A(n)} of "matrix digraphs"...
متن کاملAlgorithmic Solution of Extremal Digraph Problems’ by W. G. Brown, P. Erdos and M. Simonovits
For a grven familyY of digraphs, we study the “extremal” digraphs on n vertices containing no member of Y, and havmg the maximum number of arcs, ex( n, 9). We resolve conjectures concemmg the set {lim, _ DcI (ex( n 1 ,E”)/n2 )) as 2 ranges over all possible families. and describe a “finite” algorithm that can determine, for any Z’. all matrices A for which a sequence (A(n)} of “matrix digraphs”...
متن کاملDigraph related constructions and the complexity of digraph homomorphism problems
The role of polymorphisms in determining the complexity of constraint satisfaction problems is well established. In this context we study the stability of CSP complexity and polymorphism properties under some basic graph theoretic constructions. As applications we observe a collapse in the applicability of algorithms for CSPs over directed graphs with both a total source and a total sink: the c...
متن کاملAnalytic and algorithmic solution of random satisfiability problems.
We study the satisfiability of random Boolean expressions built from many clauses with K variables per clause (K-satisfiability). Expressions with a ratio alpha of clauses to variables less than a threshold alphac are almost always satisfiable, whereas those with a ratio above this threshold are almost always unsatisfiable. We show the existence of an intermediate phase below alphac, where the ...
متن کاملDichotomy for Digraph Homomorphism Problems
We consider the problem of finding a homomorphism from an input digraph G to a fixed digraph H. We show that if H admits a weak-near-unanimity polymorphism φ then deciding whether G admits a homomorphism to H (HOM(H)) is polynomial time solvable. This confirms the conjecture of Bulatov, Jeavons, and Krokhin [BJK05], in the form postulated by Maroti and McKenzie [MM08], and consequently implies ...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Transactions of the American Mathematical Society
سال: 1985
ISSN: 0002-9947
DOI: 10.1090/s0002-9947-1985-0808730-0