منابع مشابه
On the Restricted Burnside Problem
After many unsuccessful attempts to obtain a proof in the late 30s-early 40s the following weaker version of The Burnside Problem was studied: Is it true that there are only finitely many 7??-generated finite groups of exponent nl In other words the question is whether there exists a universal finite m-generated group of exponent n having all other finite m-generated groups of exponent n as hom...
متن کاملThe Product Homomorphism Problem and Applications
The product homomorphism problem (PHP) takes as input a finite collection of structures A1, . . . ,An and a structure B, and asks if there is a homomorphism from the direct product A1⊗· · ·⊗An to B. We pinpoint the computational complexity of this problem. Our motivation stems from the fact that PHP naturally arises in different areas of database theory. In particular, it is equivalent to the p...
متن کاملA note on the product homomorphism problem and CQ-definability
The product homomorphism problem (PHP) takes as input a finite collection of relational structures A1, . . . ,An and another relational structure B, all over the same schema, and asks whether there is a homomorphism from the direct product A1 × · · · × An to B. This problem is clearly solvable in non-deterministic exponential time. It follows from results in [1] that the problem is NExpTimecomp...
متن کاملExtensions of the Minimum Cost Homomorphism Problem
Assume D is a finite set and R is a finite set of functions from D to the natural numbers. An instance of the minimum R-cost homomorphism problem (MinHomR) is a set of variables V subject to specified constraints together with a positive weight cvr for each combination of v ∈ V and r ∈ R. The aim is to find a function f : V → D such that f satisfies all constraints and ∑
متن کاملLower Bounds for the Graph Homomorphism Problem
The graph homomorphism problem (HOM) asks whether the vertices of a given n-vertex graph G can be mapped to the vertices of a given h-vertex graph H such that each edge of G is mapped to an edge of H. The problem generalizes the graph coloring problem and at the same time can be viewed as a special case of the 2-CSP problem. In this paper, we prove several lower bounds for HOM under the Exponen...
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: Discrete Applied Mathematics
سال: 2008
ISSN: 0166-218X
DOI: 10.1016/j.dam.2007.03.028