CORR
2010
Springer
13 years 2 months ago
2010
Springer
We study here slopes of periodicity of tilings. A tiling is of slope if it is periodic along direction but has no other direction of periodicity. We characterize in this paper th...
APAL
1998
13 years 4 months ago
1998
We consider the computably enumerable sets under the relation of Qreducibility. We first give several results comparing the upper semilattice of c.e. Q-degrees, RQ, ≤Q , under ...
APAL
2006
13 years 4 months ago
2006
Abstract. We show that the identity bounded Turing degrees of computably enumerable sets are not dense.