m at h . SG ] 1 9 O ct 1 99 8 A limit of toric symplectic forms that has no periodic Hamiltonians
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چکیده
We calculate the Riemann-Roch number of some of the pentagon spaces defined in [Kl, KM, HK1]. Using this, we show that while the regular pentagon space is diffeomorphic to a toric variety, even symplectomorphic to one under arbitrarily small perturbations of its symplectic structure, it does not admit a symplectic circle action. In particular, within the cohomology classes of symplectic structures, the subset admitting a circle action is not closed.
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تاریخ انتشار 2008