Ken Wilson’s life-time achievements in fundamental theoretical physics are well known and are well documented in this memorial volume. Therefore, there is no purpose in my adding yet another appreciation of his seminal work. Rather, I shall describe Ken and some of his activities at the beginning of his career, when he was junior faculty at Cornell and I was his student — one of two in the firs...

Ken Thompson recently communicated some results mined from his set of 64 6-man endgame tables. These list some positions of interest, namely, mutual zugzwangs and those of maximum depth. The results have been analysed by the authors and found to be identical or compatible with the available or published findings of Karrer, Nalimov, Stiller and Wirth.

Barendregt’s Lemma in its original form is a statement on Combinatory Logic that holds also for the lambda calculus and gives important insight into the syntactic interplay between substitution and reduction. Its origin lies in undefinablity proofs, but there are other applications as well. It is connected to the so-called Square Brackets Lemma, introduced by van Daalen in proofs of strong norm...

In a sequence of papers (Krivine 2001; Krivine 2003; Krivine 2009) J.-L. Krivine has introduced his notion of Classical Realizability for classical second order logic and Zermelo-Fraenkel set theory. Moreover, in more recent work (Krivine 2008) he has considered forcing constructions on top of it with the ultimate aim of providing a realizability interpretation for the axiom of choice. The aim ...

In this paper, we highlight a new computational aspect of Nonstandard Analysis relating to higher-order computability theory. In particular, we prove that the Gandy-Hyland functional equals a primitive recursive functional involving nonstandard numbers inside Nelson’s internal set theory. From this classical and ineffective proof in Nonstandard Analysis, a term from Gödel’s system T can be extr...

Many of the relationships described in this special issue, put together to honour work Ken Plummer, focus on Essex connections, intergenerational friendships, or particular intellectual concerns such as symbolic interactionism citizenship.

1 Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube-shi, Yamaguchi-ken, 755-8611, Japan 2 Research Organization for Information Science & Technology, 2-32-3 Kita-shinagawa, Shinagawa-ku, Tokyo-to, 140-0001, Japan Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-kouen, Kasuga-shi, Fukuoka-ken, 816-8580, Japan Naka Fusion Institute, Jap...