Avraham_Trahtman Avraham Trahtman (Trakhtman) (b. 1944, Ph.D. (1973) and former degree (1967) at Ural State University, Sverdlovsk) is a mathematician at Bar-Ilan University (Israel). In 2007, Trahtman solved a problem in combinatorics that had been open for 37 years, the Road Coloring Conjecture posed in 1970.