COMBINATORICS
2006
13 years 4 months ago
2006
We give a parity reversing involution on noncrossing trees that leads to a combinatorial interpretation of a formula on noncrossing trees and symmetric ternary trees in answer to a...
COMBINATORICS
2006
13 years 4 months ago
2006
Sommerville [8] and Davies [2] classified the spherical triangles that can tile the sphere in an edge-to-edge fashion. Relaxing this condition yields other triangles, which tile t...
COMBINATORICS
2006
13 years 4 months ago
2006
The linear complexity of a matrix is a measure of the number of additions, subtractions, and scalar multiplications required to multiply that matrix and an arbitrary vector. In th...
COMBINATORICS
2006
13 years 4 months ago
2006
Consider the symmetric group Sn equipped with the Hamming metric dH . Packing and covering problems in the finite metric space (Sn, dH ) are surveyed, including a combination of b...
COMBINATORICS
2006
13 years 4 months ago
2006
An H-factor of a graph G is a spanning subgraph of G whose connected components are isomorphic to H. Given a properly edge-colored graph G, a rainbow H-subgraph of G is an H-subgr...
COMBINATORICS
2006
13 years 4 months ago
2006
We present both probabilistic and constructive lower bounds on the maximum size of a set of points S Rd such that every angle determined by three points in S is acute, considerin...
COMBINATORICS
2006
13 years 4 months ago
2006
We introduce a permutation analogue of the celebrated Szemer
COMBINATORICS
2006
13 years 4 months ago
2006
COMBINATORICS
2006
13 years 4 months ago
2006
A differential poset is a partially ordered set with raising and lowering operators U and D which satisfy the commutation relation DU-UD = rI for some constant r. This notion may ...
COMBINATORICS
2006
13 years 4 months ago
2006
A set of vertices S is a determining set for a graph G if every automorphism of G is uniquely determined by its action on S. The determining number of a graph is the size of a sma...