|Born||10 February 1944
Kalinovo, Nevyansky District, Sverdlovsk Oblast
|Alma mater||Ural State University|
|Doctoral advisor||Lev Shevrin|
|Known for||solving the road coloring problem|
Avraham Trahtman (Trakhtman) (Russian: Абрам Наумович Трахтман; b. 1944, USSR) 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.
Road coloring problem posed and solved
Trahtman's solution to the road coloring problem was accepted in 2007 and published in 2009 by the Israel Journal of Mathematics. The problem arose in the subfield of symbolic dynamics, an abstract part of the field of dynamical systems. The road coloring problem was raised by R. L. Adler and L. W. Goodwyn from the United States, and the Israeli mathematician B. Weiss. The proof used results from earlier work.
The problem of estimating the length of synchronizing word has a long history and was posed independently by several authors, but it is commonly known as the Černý conjecture. In 1964 Jan Černý conjectured that (n-1)2 is the upper bound for the length of the shortest synchronizing word for any n-state complete DFA (a DFA with complete state transition graph). If this is true, it would be tight: in his 1964 paper, Černý exhibited a class of automata (indexed by the number n of states) for which the shortest reset words have this length. In 2011 Trakhtman published  a proof of upper bound n(7n2+6n-16)/48, but later the proof turned out to be erroneous. The conjecture holds in many partial cases, see for instance
The problem of the finite basis question for semigroups of order less than six in the theory of semigroups was posed by Alfred Tarski in 1966, and repeated immediately by Anatoly Maltsev and Shevrin. The problem was solved by Trahtman 17 years later in 1983.
In the theory of varieties of semigroups and universal algebras the problem of existence of covering elements in the lattice of varieties was posed by Evans in 1971. The positive solution of the problem was found by Trahtman. He also found a six-element semigroup that generates a variety with a continuum of subvarieties, and varieties of semigroups having no irreducible base of identities.
The theory of locally testable automata can be based on the theory of varieties of locally testable semigroups. Trahtman found the precise estimation on the order of local testability of finite automata.
- J.E. Pin. On two combinatorial problems arising from automata theory. Annals of Discrete Math., 17, 535-548, 1983.
- Avraham N. Trahtman: The Road Coloring Problem. Israel Journal of Mathematics, Vol. 172, 51–60, 2009
- R.L. Adler, B. Weiss. Similarity of automorphisms of the torus, Memoirs of the Amer. Math. Soc. 98, Providence, RI, 1970
- R.L. Adler, L.W. Goodwyn, B. Weiss. Equivalence of topological Markov shifts, Israel J. of Math. 27, 49-63, 1977
- K. Culik II, J. Karhumaki, J. Kari. A note on synchronized automata and Road Coloring Problem. Developments in Language Theory (5th Int. Conf., Vienna, 2001), Lecture Notes in Computer Science, 2295, 175-185, 2002
- J. Friedman. On the road coloring problem. Proc. of the Amer. Math. Soc. 110, 1133-1135, 1990
- A.N. Trahtman. An Algorithm for Road Coloring. Lect. Notes in Comp. Sci, 7056 (2011), Springer, 349--360
- J. Černý, Poznamka k homogenym eksperimentom s konechnymi automatami, Math.-Fyz. Čas., 14(1964) 208--215.
- A.N. Trahtman. Modifying the Upper Bound on the Length of Minimal Synchronizing Word. Lect. Notes in Comp. Sci, 6914(2011) Springer, 173-180
- J. Kari. Synchronizing finite automata on Eulerian digraphs. Springer, Lect. Notes in Comp. Sci., 2136, 432-438, 2001.
- A.N. Trahtman. The Černý Conjecture for Aperiodic Automata. Discr. Math. & Theor. Comput. Sci. v. 9, 2(2007), 3-10
- A. Tarski. Equational logic and equational theories of algebras. Contrib. to math. Logic. Hannover, 1966, (Amst. 1968), 275-288.
- A. N. Trahtman. The finite basis question for semigroups of order less than six. Semigroup Forum, NY, 27(1983), 387-389.
- A.N. Trahtman. Finiteness of a basis of identities of 5-element semigroups. Polugruppy i ih gomomorphismy, Ross. Gos. ped. Univ., Leningrad, 1991, 76-98.
- T. Evans. The lattice of semigroup varieties. Semigroup Forum. 2, 1(1971), 1-43.
- A.N. Trahtman. Covering elements in the lattice of varieties of universal algebras. Mat. Zametky, Moscow, 15(1974), 307-312.
- A.N. Trahtman. A sixelement semigroup that generates a variety with a continuum of subvarieties. Ural Gos. Univ. Mat. zap., Alg. syst. i ih mnogoobr., Sverdlovsk, 14(1988), no. 3, 138-143.
- A. N. Trahtman. A variety of semigroups without an irreducible basis of identities. Math. Zametky, Moscow, 21(1977), 865-871.
- A. N. Trahtman. Identities of locally testable semigroups. Comm. Algebra, 27(1999), no. 11, 5405-5412.
- A. N. Trahtman. Optimal estimation on the order of local testability of finite automata. Theoret. Comput. Sci., 231(2000), 59-74.
- S.A. Kazak, G.G. Kozhushko, A.N. Trahtman. Calculation of load in discrete chains. Teorija mashin i met. gorn. ob. Sverdlovsk, rel. 1, 1978, 39-51.
- B Kogan., A.N. Trahtman. The Moisture from the Air as Water Resource in Arid Region: Hopes, Doubts and Facts. J of Arid Env., London, 2, 53(2003), 231-240.
- F. Pearce. Pyramids of dew. "New Scientist". 16 April 2005. 52-53.
- Avraham Trahtman at the Mathematics Genealogy Project
- Trahtman's page at Bar-Ilan University's Website
- Trahtman's Curriculum Vitae
- Trahtman's paper (in PDF format)
- "63-year-old solves riddle from 1970" on MSNBC
- "Encyclopedia - Britannica Online Encyclopedia", article: Avraham Trahtman
- "MacTutor History of Mathematics. Trahtman biography"
- "Israeli Mathematicians, Adi Shamir, Giulio Racah, Saharon Shelah, Zlil Sela, Robert Aumann, Michael O. Rabin, Oded Schramm, Avraham Trahtman, Llc Books, 2010"
- "A Mathematical Medley Fifty Easy Pieces on Mathematics. George G. Szpiro"