COMBINATORICS
2006
13 years 11 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 11 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 11 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 11 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 11 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 11 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 11 months ago
2006
We introduce a permutation analogue of the celebrated Szemer
COMBINATORICS
2006
13 years 11 months ago
2006
COMBINATORICS
2006
13 years 11 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 11 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...