We prove that a computably enumerable set A is effectively speedable (effectively levelable) if and only if there exists a splitting (A0,A1) of A such that both A0 and A1 are effectively speedable (effectively levelable). These results answer two questions raised by J. B. Remmel.
"Splittings of effectively speedable sets and effectively levelable sets." J. Symbolic Logic 69 (1) 143 - 158, March 2004. https://doi.org/10.2178/jsl/1080938833