Alexandru Oancea

  1. On the topology of fillings of contact manifolds and applications.

    Authors: Alexandru Oancea, Claude Viterbo
    Subjects: Symplectic Geometry
    Abstract

    The aim of this paper is to address the following question: given a contact
    manifold $(\Sigma, \xi)$, what can be said about the aspherical symplectic
    manifolds $(W, \omega)$ bounded by $(\Sigma, \xi)$ ? We first extend a theorem
    of Eliashberg, Floer and McDuff to prove that under suitable assumptions the
    map from $H_{*}(\Sigma)$ to $H_{*}(W)$ induced by inclusion is surjective. We
    then apply this method in the case of contact manifolds having a contact
    embedding in $ {\mathbb R}^{2n}$ or in a subcritical Stein manifold.

  2. The Gysin exact sequence for $S^1$-equivariant symplectic homology.

    Authors: Frédéric Bourgeois, Alexandru Oancea
    Subjects: Symplectic Geometry
    Abstract

    We define $S^1$-equivariant symplectic homology for symplectically aspherical
    manifolds with contact boundary, using a Floer-type construction first proposed
    by Viterbo. We show that it is related to the usual symplectic homology by a
    Gysin exact sequence. As an important ingredient of the proof, we define a
    parametrized version of symplectic homology, corresponding to families of
    Hamiltonian functions indexed by a finite dimensional smooth parameter space.
    We define a parametrized version of the Robbin-Salamon index, which gives the
    grading for these new versions of symplectic homology.

  3. Fredholm theory and transversality for the parametrized and $S^1$-invariant symplectic action.

    Authors: Frédéric Bourgeois, Alexandru Oancea
    Subjects: Symplectic Geometry
    Abstract

    We study the parametrized Hamiltonian action functional for
    finite-dimensional families of Hamiltonians. We show that the linearized
    operator for the $L^2$-gradient lines is Fredholm and surjective, for a generic
    choice of Hamiltonian and almost complex structure. We also establish the
    Fredholm property and transversality for generic $S^1$-invariant families of
    Hamiltonians and almost complex structures, parametrized by odd-dimensional
    spheres. This is a foundational result used to define $S^1$-equivariant Floer
    homology.

  4. Fredholm theory and transversality for the parametrized and $S^1$-invariant symplectic action.

    Authors: Frédéric Bourgeois, Alexandru Oancea
    Subjects: Symplectic Geometry
    Abstract

    We study the parametrized Hamiltonian action functional for
    finite-dimensional families of Hamiltonians. We show that the linearized
    operator for the $L^2$-gradient lines is Fredholm and surjective, for a generic
    choice of Hamiltonian and almost complex structure. We also establish the
    Fredholm property and transversality for generic $S^1$-invariant families of
    Hamiltonians and almost complex structures, parametrized by odd-dimensional
    spheres. This is a foundational result used to define $S^1$-equivariant Floer
    homology.

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