Elementary differences between the (2p)-C. E. and the (2p +1)-c. e. enumeration degrees
ISKANDER SH. KALIMULLIN · Journal of Symbolic Logic · 2007
Abstract It is proved that the (2p)-c. e. e-degrees are not elementarily equivalent to the (2p + 1)-c. e. e-degrees for each nonzero p ∈ ω. It follows that m-c. e. e-degrees are not elementarily equivalent to the n-c e. e-degrees if 1 <m < n.