88
Voted
JCT
1998
14 years 11 months ago
1998
If P is an upper semilattice whose Hasse diagram is a tree and whose cartesian powers are Macaulay, it is shown that Hasse diagram of P is actually a spider in which all the legs ...
95
Voted
APAL
1998
14 years 11 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 ...
84
Voted
APAL
2007
14 years 11 months ago
2007
Based on a result of Nies on definability the upper semilattice of computably enumerable degrees (denoted by R), we find that in R filters generated by definable subsets are al...