Abstract
The primary aim of this paper is to investigate some general properties of a
Hamiltonian circle action under certain minimality condition. As main applications
of our techniques of this paper, we show the existence and also non-existence
theorems of a Hamiltonian circle action of pure type on a compact symplectic
manifold under the assumption that the fixed-point set has the smallest possible
number of components and satisfies a certain non-minimality condition. Those
theorems can be regarded as a first step towards the classification of higher dimensional
closed symplectic manifolds admitting a Hamiltonian circle action, and
provide some constraints to the existence of certain Hamiltonian circle actions.
Some new general formulas for the S1-equivariant Euler class of the negative normal
bundle of a fixed-point component which might be of independent interest
play a crucial role in obtaining main applications of this paper.