CORR
2010
Springer
13 years 8 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 10 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 11 months ago
2006
Abstract. We show that the identity bounded Turing degrees of computably enumerable sets are not dense.