BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Maggie Miller (Massachusetts Institute of Technology) DTSTART:20210507T140000Z DTEND:20210507T150000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/1 DESCRIPTION:Title: Diagrams of immersed surfaces\nby Maggie Miller (Massachusetts In stitute of Technology) as part of Low dimensional topology and symplectic geometry weekend\n\n\nAbstract\nA surface embedded in a 4-manifold can be depicted via a banded unlink diagram\, which consists of decorated links i n S^3 with some bands attached. In 2002\, Swenton showed that diagrams of isotopic surfaces in S^4 are related by a short list of moves. In 2019\, H ughes\, Kim and I extended this to isotopic surfaces in a general 4-manifo ld. In this talk\, I will describe singular banded unlink diagrams of regu larly immersed surfaces in 4-manifolds\, and again show that there is a co mplete set of moves on these diagrams. These diagrams can be used to const ruct homotopies of surfaces and study the intersection sets\, which is use ful for computing certain surface invariants. This is joint work with Mark Hughes and Seungwon Kim.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/1/ END:VEVENT BEGIN:VEVENT SUMMARY:Jonathan Simone (University of Massachusetts Amherst) DTSTART:20210507T151500Z DTEND:20210507T161500Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/2 DESCRIPTION:Title: Chi-slice 3-braid links\nby Jonathan Simone (University of Massac husetts Amherst) as part of Low dimensional topology and symplectic geomet ry weekend\n\n\nAbstract\nA link L in the 3-sphere is called chi-slice if it bounds a properly embedded surface F in the 4-ball with Euler character istic 1. If L is a knot\, then this definition coincides with the usual de finition of sliceness. One feature of such a link L is that if the determi nant of L is nonzero\, then the double cover of the 3-sphere branched over L bounds a rational homology ball. In this talk\, we will explore the chi -sliceness of quasi-alternating 3-braid links. In particular\, we will con struct explicit families of chi-slice quasi-alternating 3-braids using ban d moves and we will obstruct the chi-sliceness of most other quasi-alterna ting 3-braid links by showing that their double branched covers do not bou nd rational homology 4-balls. This is a work in progress joint with Vitaly Brejevs.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Jason Joseph (Rice University) DTSTART:20210507T163000Z DTEND:20210507T170000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/3 DESCRIPTION:Title: Unknotting numbers of 2-spheres in the 4-sphere\nby Jason Joseph (Rice University) as part of Low dimensional topology and symplectic geome try weekend\n\n\nAbstract\nIn this talk I'll discuss two notions of an unk notting number for knotted 2-spheres in the 4-sphere\, with the goal of co mparing them. One is the minimal number of stabilizations needed to produc e an unknotted surface\, and the other is the minimal number of pairs of f inger and Whitney moves needed during a regular homotopy to the unknotted sphere. Most of the times that these numbers can be computed\, they are th e same\; however\, I'll present a general inequality between them and give a family of examples where they differ. This is joint work with Michael K lug\, Benjamin Ruppik\, and Hannah Schwartz.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Kevin Sackel (Stony Brook University / SCGP) DTSTART:20210508T140000Z DTEND:20210508T150000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/4 DESCRIPTION:Title: Quantitative Refinements of Non-Squeezing in Dimension 4\nby Kevi n Sackel (Stony Brook University / SCGP) as part of Low dimensional topolo gy and symplectic geometry weekend\n\n\nAbstract\nGromov's celebrated Non- Squeezing Theorem states that a ball of radius R cannot embed symplectical ly into a cylinder of radius 1 unless R ≤ 1. Nowadays\, there is an indu stry of understanding when symplectic embeddings exist between all sorts o f domains. We study a slightly different question -- how much do we need t o remove from the ball of radius R so that it squeezes into a cylinder of radius 1? In four dimensions\, we prove that the (lower) Minkowski dimensi on of the region removed must be at least 2\, and that this result is opti mal for R^2 ≤ 2. Time permitting\, we discuss a few related results and open problems. This work is joint with Antoine Song\, Umut Varolgunes\, an d Jonathan Zhu.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Cheuk Yu Mak (University of Edinburgh) DTSTART:20210508T151500Z DTEND:20210508T161500Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/5 DESCRIPTION:Title: Non-displaceable Lagrangian links in four-manifolds\nby Cheuk Yu Mak (University of Edinburgh) as part of Low dimensional topology and symp lectic geometry weekend\n\n\nAbstract\nOne of the earliest fundamental app lications of Lagrangian Floer theory is detecting the non-displaceablity o f a Lagrangian submanifold. Many progress and generalisations have been m ade since then but little is known when the Lagrangian submanifold is disc onnected. In this talk\, we describe a new idea to address this problem. Subsequently\, we explain how to use Fukaya-Oh-Ohta-Ono and Cho-Poddar th eory to show that for every S^2 \\times S^2 with a non-monotone product sy mplectic form\, there is a continuum of disconnected\, non-displaceable La grangian submanifolds such that each connected component is displaceable. This is a joint work with Ivan Smith.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Nick Castro (University of Arkansas) DTSTART:20210508T163000Z DTEND:20210508T170000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/6 DESCRIPTION:Title: Relative Group Trisections\nby Nick Castro (University of Arkansa s) as part of Low dimensional topology and symplectic geometry weekend\n\n \nAbstract\nA trisection of a smooth\, compact\, 4–manifold is a decompo sition into three diffeomorphic pieces\, where the complexity of the 4–m anifold lies in how these pieces are attached to one another. In the case of a manifold with boundary\, a relative trisection induces a structure on the boundary known as an open book decomposition. In this talk\, we will provide a correspondence between relative trisections of 4–manifolds wit h boundary and commutative cubes of groups\, known as relative group trise ctions. The interesting feature of a (relative) group trisection is that i t encodes all of the smooth topology of the 4–manifold\, including the i nduced boundary data. This extends group trisections of closed 4–manifol ds\, due to work of Abrams\, Gay\, and Kirby\, to the relative setting. Th is work is joint with Jason Joseph and Patrick McFaddin.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Anubhav Mukherjee (Georgia Institute of Technology) DTSTART:20210509T140000Z DTEND:20210509T150000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/7 DESCRIPTION:Title: Obstructions to embeddings in 4-manifolds using Bauer-Furuta type inv ariant\nby Anubhav Mukherjee (Georgia Institute of Technology) as part of Low dimensional topology and symplectic geometry weekend\n\n\nAbstract \nIn this talk I will discuss some new properties of an invariant for 4-ma nifold with boundary which was originally defined by Nobuo Iida. As one of the applications of this new invariant I will demonstrate how one can obs truct a knot from being h-slice (i.e bound a homologically trivial disk) i n 4-manifolds. Also\, this invariant can be useful to detect exotic smooth structures of 4-manifolds. This a joint work with Nobuo Iida and Masaki T aniguchi.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/7/ END:VEVENT BEGIN:VEVENT SUMMARY:Jun Li (University of Michigan-Ann Arbor) DTSTART:20210509T151500Z DTEND:20210509T161500Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/8 DESCRIPTION:Title: Symplectic mapping class groups in dimension 4\nby Jun Li (Univer sity of Michigan-Ann Arbor) as part of Low dimensional topology and symple ctic geometry weekend\n\n\nAbstract\nSymplectic manifolds arise naturally in abstract formulations of classical mechanics\, and symplectic geometry is an interesting mixture of the “soft” and the “rigid.” In this talk\, we will focus on symplectic rigidity phenomena. In particular\, we will discuss recent developments for the Symplectic mapping class group s of 4-dimensional symplectic manifolds\, and how these root in dynamics and topology in dimension 2. Those are based on joint works with T-J Li\, Weiwei Wu\, and with Olga Buse. Time permitting\, we'll outline some open problems for the informal discussion session.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/8/ END:VEVENT BEGIN:VEVENT SUMMARY:Biji Wong (Max Planck Institute for Mathematics) DTSTART:20210509T163000Z DTEND:20210509T170000Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/9 DESCRIPTION:Title: d-invariants of double branched covers of links\nby Biji Wong (Ma x Planck Institute for Mathematics) as part of Low dimensional topology an d symplectic geometry weekend\n\n\nAbstract\nUsing Heegaard Floer homology \, one can associate to a rational homology 3-sphere Y\, equipped with a s pinc-structure s\, a rational number\, commonly referred to as the d-invar iant of (Y\, s). d-invariants have been useful in answering a range of que stions in low-dimensional topology. A nice source of rational homology 3-s pheres comes from considering double branched covers Sigma_2(K) of knots K . If \\Sigma_2(K) is an L-space\, then the d-invariant of \\Sigma_2(K)\, a t the unique spin-structure s_0\, is well-understood: it's a multiple of t he signature of K. In this talk\, we'll discuss what happens when we pass to double branched covers of multi-component links. This is work in progre ss with M. Marengon.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/9/ END:VEVENT BEGIN:VEVENT SUMMARY:Angela Wu (University College London) DTSTART:20210509T171500Z DTEND:20210509T174500Z DTSTAMP:20260417T043016Z UID:LDTSGweekend/10 DESCRIPTION:Title: Obstructing Lagrangian concordance for 3-braids\nby Angela Wu (U niversity College London) as part of Low dimensional topology and symplect ic geometry weekend\n\n\nAbstract\nTwo knots are said to be concordant if they jointly form the boundary of a cylinder in four-dimensional Euclidean space. In the symplectic setting\, we say they are Lagrangian concordant if the knots are Legendrian and the cylinder is Lagrangian. In this talk I 'll show that no Legendrian knot which is both concordant to and from the unstabilized Legendrian unknot can be the closure of an index 3 braid exce pt the unknot itself.\n LOCATION:https://researchseminars.org/talk/LDTSGweekend/10/ END:VEVENT END:VCALENDAR