The strength of some combinatorial principles related to Ramsey’s theorem
(with Denis R. Hirschfeldt, Carl G. Jockusch, Steffen Lempp, and Theodore A. Slaman.) Computational Prospects of Infinity. Part II: Presented Talks, Lecture Notes Series, Institute of Mathematical Sciences, National University of Singapore, vol. 15, World Scientific Publishing, Hackensack, NJ, 2008, pp. 143—162.
This paper established that Stable Ramsey’s Theorem for pairs implies DNR, which is a weak form of WKL.
It was later shown by Liu in 2011 that Ramsey’s theorem for pairs does not imply WKL (which is what we really wanted to know!).
This paper was written while all authors were participating in the Computational Prospects of Infinity workshop in Singapore in 2005.
On a conjecture of Dobrinen and Simpson concerning almost everywhere domination (with Stephen Binns, Manuel Lerman, and Reed Solomon). Journal of Symbolic Logic 71 (2006), no. 1, 119—136.
This paper was concerned with the difference between highness and almost everywhere domination in the Turing degrees. This was taken further in later papers.
Lowness for the class of Schnorr random reals (with André Nies and Frank Stephan).SIAM Journal on Computing 35 (2005), no. 3, 647—657 (electronic).
In this paper the idea of mixed lowness notions seems to have been born (?). This idea actually occurred to me while unlocking my bicycle in Heidelberg.
Comparing DNR and WWKL (with Klaus Ambos-Spies, Steffen Lempp, and Theodore A. Slaman).
Journal of Symbolic Logic 69 (2004), no. 4, 1089—1104.
This paper (which is mentioned in Wikipedia under Reverse Mathematics) separated DNR from WWKL. It was mostly written while all four authors were in Heidelberg during 2002-2003.
Local initial segments of the Turing degrees
Bulletin of Symbolic Logic
9 (2003), no. 1, 26—36.
This paper described the results of my doctoral dissertation “Lattice initial segments of the Turing degrees”.