arXiv subjects

Olguta Buse

Publications and source records attributed to Olguta Buse.

8 recordsLinked to original sources

arXiv2022

Chambers in the symplectic cone and stability of symplectomorphism group for ruled surface

We continue our previous work to prove that for any non-minimal ruled surface $(M,ω)$, the stability under symplectic deformations of $π_0, π_1$ of $Symp(M,ω)$ is guided by embedded $J$-holomorphic curves. Further, we prove that for any fixed sizes blowups, when the area ratio $μ$ between the section and fiber goes to infinity, there is a topological colimit of $Symp(M,ω_μ).$ Moreover, when the blowup sizes are all equal to half the area of the fiber class, we give a topological model of the colimit which induces non-trivial symplectic mapping classes in $Symp(M,ω) \cap \rm Diff_0(M),$ where $\rm Diff_0(M)$ is the identity component of the diffeomorphism group. These mapping classes are not Dehn twists along Lagrangian spheres.

math.SG↗

arXiv2020

Symplectic isotopy on non-minimal ruled surfaces

We prove the stability of $Symp(X,\omega)\cap Diff_0(X)$ for a one-point blow-up of irrational ruled surfaces and study their topological colimit. Non-trivial generators of $\pi_0[Symp(X,\omega)\cap Diff_0(X)]$ that differ from Lagrangian Dehn twists are detected.

math.SG↗

arXiv2014

Packing stability for symplectic $4$-manifolds

We show that all closed symplectic 4-manifolds have the packing stability property: there are no obstructions beyond volume to embedding a collection of sufficiently small balls. This generalizes a theorem of Biran which gives the same result under the assumption that the symplectic form lies in a rational cohomology class.

math.SG↗

arXiv2011

Symplectic embeddings of ellipsoids in dimension greater than four

We study symplectic embeddings of ellipsoids into balls. In the main construction, we show that a given embedding of 2m-dimensional ellipsoids can be suspended to embeddings of ellipsoids in any higher dimension. In dimension 6,s if the ratio of the areas of any two axes is sufficiently large then the ellipsoid is flexible in the sense that it fully fills a ball. We also show that the same property holds in all dimensions for sufficiently thin ellipsoids E(1,..., a). A consequence of our study is that in arbitrary dimension a ball can be fully filled by any sufficiently large number of identical smaller balls, thus generalizing a result of Biran valid in dimension 4.

math.SG↗

arXiv2011

Ellipsoid embeddings and symplectic packing stability

We prove packing stability for any closed symplectic manifold with rational cohomology class. This will rely on a general symplectic embedding result for ellipsoids which assumes only that there is no volume obstruction and that the domain is sufficiently thin relative to the target. We also obtain easily computable bounds for the Embedded Contact Homology capacities which are sufficient to imply the existence of some volume preserving embeddings in dimension 4.

math.SG↗

arXiv2011

Packing numbers of rational ruled 4-manifolds

We completely solve the symplectic packing problem with equally sized balls for any rational, ruled, symplectic 4-manifolds. We give explicit formulae for the packing numbers, the generalized Gromov widths, the stability numbers, and the corresponding obstructing exceptional classes. As a corollary, we give explicit values for when an ellipsoid of type $E(a, b)$, with $\frac{b}{a} \in \N$, embeds in a polydisc $P(s,t)$. Under this integrality assumption, we also give an alternative proof of a recent result of M. Hutchings showing that the ECH capacities give sharp inequalities for embedding ellipsoids into polydisks.

math.SG↗

arXiv2004

Whitehead products in symplectomorphism groups and Gromov-Witten invariants

Consider any symplectic ruled surface $(M^g_λ,ω_λ)$ given by $(Σ_g \times S^2, λσ_{Σ_g} \oplus σ_{S^2})$. We compute all natural equivariant Gromov-Witten invariants $EGW_{g,0}(M^g_λ;H_k, A-kF)$ for all hamiltonian circle actions $H_k$ on $M^g_λ$, where $A=[Σ_g \times pt]$ and $F= [pt \times S^2]$. We use these invariants to show the nontriviality of certain higher order Whitehead products that live in the homotopy groups of the symplectomorphism groups $G_λ^g$, $g \geq 0$. Our results are sharper when $g=0,1$ and enable us to answer a question posed by D.McDuff in the case $g=1$ and provide a new interpretation of the multiplicative structure in the ring $H^*(BG^0_λ ;\Q)$ found by Abreu-McDuff.

math.SG↗

arXiv2001

Relative family Gromov-Witten invariants and symplectomorphisms

We study the symplectomorphism groups $G_λ=Symp_0(M,ω_λ)$ of an arbitrary closed manifold M equipped with a 1-parameter family of symplectic forms $ω_λ$ with variable cohomology class. We show that the existence of nontrivial elements in $π_*({\cal A},{\cal A}')$, where $({\cal A},{\cal A}')$ is a suitable pair of spaces of almost complex structures, implies the exiarxiv.org stence of families of nontrivial elements in $π_{*-i}G_λ$, for $i=1$ or 2. Suitable parametric Gromov Witten invariants detect nontrivial elements in $π_*({\cal A},{\cal A}')$. By looking at certain resolutions of quotient singularities we investigate the situation $(M,ω_λ)= (S^2 \times S^2 \times X,σ_F \oplus λσ_B \oplus ω_{st})$, with $(X,ω_{st})$ an arbitrary symplectic manifold. We find families of nontrivial elements in $π_k(G_λ^X)$, for countably many $k$ and different values of $λ$. In particular we show that the fragile elements $w_{\ell}$ found by Abreu-McDuff in $π_{4 \ell}(G_{\ell+1}^{pt})$ do not disappear when we consider them in $S^2 \times S^2 \times X$.

math.SG↗