Stathis Zachos

Stathis K. Zachos (Greek: Στάθης (Ευστάθιος) Ζάχος; born 1947, Athens) is a mathematician, logician and theoretical computer scientist.

Zachos received his PhD from the ETHZ (Swiss Federal Institute of Technology Zurich) in Mathematics (and Computer Science), 1978. He has held the posts of professor in Computer Science at UCSB, CUNY and NTUA and Adjunct professor at ETHZ. He has worked as a researcher at MIT, Brown-Boveri.

Stathis has published research papers in several areas of Computer Science. His work on Randomized Complexity Classes,, and Interactive Proof Systems has been very influential in proving important theorems and is cited in main textbooks of computational complexity. One of his important contributions, using Interactive Proof Systems and Probabilistic Quantifiers, is that the Graph isomorphism Problem is not likely to be NP-complete (joint with R. Boppana, J. Hastad). Graph Isomorphism is one of the very few celebrated problems in NP that have not been shown yet to be either NP-Complete or in P. Zachos's most influential work was introducing and proving properties of the class Parity-P (with Christos Papadimitriou). He also introduced Probabilistic Quantifiers and Alternations of Probabilistic Quantifiers to uniformly describe various Complexity Classes as well as Interactive Proof Systems and Probabilistic Games.

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