Quantitative symplectic geometry

Symplectic capacities were introduced in 1990 by I. Ekeland and H. Hofer [19, 20] (although the first capacity was in fact constructed by M. Gromov [40]). Since then, lots of new capacities have been defined [16, 30, 32, 44, 49, 59, 60, 90, 99] and they were further studied in [1, 2, 8, 9, 17, 26, 21, 28, 31, 35, 37, 38, 41, 42, 43, 46, 48, 50, 52, 56, 57, 58, 61, 62, 63, 64, 65, 66, 68, 74, 75, 76, 88, 89, 91, 92, 94, 97, 98]. Surveys on symplectic capacities are [45, 50, 55, 69, 97]. Different capacities are defined in different ways, and so relations between capacities often lead to surprising relations between different aspects of symplectic geometry and Hamiltonian dynamics. This is illustrated in § 2, where we discuss some examples of symplectic capacities and describe a few consequences of their existence. In § 3 we present an attempt to better understand the space of all symplectic capacities, and discuss some further general properties of symplectic capacities. In § 4, we describe several new relations between certain symplectic capacities on ellipsoids and polydiscs. Throughout the discussion we mention many open problems.