Yakov Sinai is a mathematician whose work has revolutionised the fields of dynamical systems, statistical mechanics, probability theory and statistical physics. He is renowned for his work in ergodic theory — the study how mathematical and physical systems tend to ‘visit’ all of their available states over time. Yakov’s research has important applications in topics as diverse as planetary motion, ocean currents, population dynamics and electrical networks.

His work on order and chaos was groundbreaking. He showed that chaos can appear in deterministic systems, which do not experience randomness when moving from one state to another. In turn, definite predictions can arise from the statistical analysis of chaotic systems.

The fundamental importance of Yakov’s work can be seen in the many results bearing his name. These include Kolmogorov–Sinai entropy, Sinai’s billiards, Sinai’s random walk and Pirogov–Sinai theory. His achievements have been further recognised with many awards, including the Frederic Esser Nemmers Prize in Mathematics, the Wolf Prize in Mathematics, the and Abel Prize.