Grid homology is a combinatorial version of knot Floer homology. In a previous thesis, the author established an unoriented skein exact triangle for grid homology, giving a combinatorial proof of Manolescu’s unoriented skein exact triangle for knot Floer homology, and extending Manolescu’s result from Z/2Z coefficients to coefficients in any commutative ring. In Part II of this dissertation, after recalling the combinatorial proof mentioned above, we track the delta-gradings of the maps involved in the skein exact triangle, and use them to establish the Floer-homological sigma-thinness of quasi-alternating links over any commutative ring. Tangle Floer homology is a combinatorial extension of knot Floer homology to tangles, introduced by Petkova–Vertesi; it assigns an A-infinity-(bi)module to each tangle, so that the knot Floer homology of a link L obtained by gluing together tangles T_1, ..., T_n can be recovered from a tensor product of the A-infinity-(bi)modules assigned to the tangles T_i. Currently, tangle Floer homology has only been defined over Z/2Z. Part III of this dissertation presents a joint result with Ina Petkova, establishing an analogous unoriented skein relation for tangle Floer homology over Z/2Z, and tracking the delta-gradings involved.

Thesis advisor: John Baldwin / Heegaard Floer homology is a family of invariants in low dimensional topology due originally to Ozsváth-Szabó. We discuss various aspects of Heegaard Floer homology and give several link detection results for versions of Heegaard Floer homology for links. In particular, we show that knot and link Floer homology detect various infinite families of cable links. We also give classification results for the Heegaard Floer theoretic invariants of a type of knot called an “almost L-space knot” and an infinite family of detection results for annular Khovanov homology. / Thesis (PhD) — Boston College, 2023. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

In this dissertation, we study the isotopy problem for a certain three-dimensional contactomorphism which is supported in a neighbourhood of an embedded 2-sphere with standard characteristic foliation. The diffeomorphism which underlies it is the Dehn twist on the sphere, and therefore its square becomes smoothly isotopic to the identity. The main result of this dissertation gives conditions under which any iterate of the Dehn twist along a non-trivial sphere is not contact isotopic to the identity. This provides the first examples of exotic contactomorphisms with infinite order in the contact mapping class group, as well as the first examples of exotic contactomorphisms of 3-manifolds with b_1 = 0. The proof crucially relies on the construction of an invariant for families of contact structures in monopole Floer homology which generalises the Kronheimer--Mrowka--Ozsváth--Szabó contact invariant, together with the nice interaction between this families invariant and the U map in Floer homology.

Thesis advisor: John A. Baldwin / Khovanov homology and Heegaard Floer homology have opened new horizons in knot theory and three-manifold topology, respectively. The two invariants have distinct origins, but the Khovanov homology of a link is related to the Heegaard Floer homology of its branched double cover by a spectral sequence constructed by Ozsváth and Szabó. In this thesis, we construct an equivalent spectral sequence with a much more transparent connection to Khovanov homology. This is the first step towards proving Seed and Szabó's conjecture that Szabó's geometric spectral sequence is isomorphic to Ozsváth and Szabó's spectral sequence. These spectral sequences connect information about contact structures contained in each invariant. We construct a braid conjugacy class invariant κ from Khovanov homology by adapting Floer-theoretic tools. There is a related transverse invariant which we conjecture to be effective. The conjugacy class invariant solves the word problem in the braid group among other applications. We have written a computer program to compute the invariant. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

Kwong, Kwok Kun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 105-109). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / Introduction --- p.1 / Chapter 1 --- Morse Theory --- p.4 / Chapter 1.1 --- Introduction --- p.4 / Chapter 1.2 --- Morse Homology --- p.11 / Chapter 2 --- Symplectic Fixed Points and Arnold Conjecture --- p.24 / Chapter 2.1 --- Introduction --- p.24 / Chapter 2.2 --- The Variational Approach --- p.29 / Chapter 2.3 --- Action Functional and Moduli Space --- p.30 / Chapter 2.4 --- Construction of Floer Homology --- p.42 / Chapter 3 --- Fredholm Theory --- p.46 / Chapter 3.1 --- Fredholm Operator --- p.47 / Chapter 3.2 --- The Linearized Operator --- p.48 / Chapter 3.3 --- Maslov Index --- p.50 / Chapter 3.4 --- Fredholm Index --- p.57 / Chapter 4 --- Floer Homology --- p.75 / Chapter 4.1 --- Transversality --- p.75 / Chapter 4.2 --- Compactness and Gluing --- p.76 / Chapter 4.3 --- Floer Homology --- p.88 / Chapter 4.4 --- Invariance of Floer Homology --- p.90 / Chapter 4.5 --- An Isomorphism Theorem --- p.98 / Chapter 4.6 --- Further Applications --- p.103 / Bibliography --- p.105

In 1992, Xiao-Song Lin constructed an invariant h of knots in the 3-sphere via a signed count of the conjugacy classes of irreducible SU(2)-representations of the fundamental group of the knot exterior with trace-free meridians. Lin showed that h equals one-half times the knot signature. Using methods similar to Lin's, we construct an invariant of two-component links in the 3-sphere. Our invariant is a signed count of conjugacy classes of projective SU(2)-representations of the fundamental group of the link exterior with a fixed 2-cocycle and corresponding non-trivial second Stiefel--Whitney class. We show that our invariant is, up to a sign, the linking number. We further construct, for a two-component link in an integral homology sphere, an instanton Floer homology whose Euler characteristic is, up to sign, the linking number between the components of the link. We relate this Floer homology to the Kronheimer-Mrowka instanton Floer homology of knots. We also show that, for two-component links in the 3-sphere, the Floer homology does not vanish unless the link is split.

This thesis proposes an improved notion of coefficient system for Lagrangian Floer Homology which allows one to produce nontrivial invariants away from characteristic 2, even when coherent orientations of moduli spaces of Floer trajectories do not exist. This explains a suggestion of Witten. The invariant can be computed in examples, and the method explained below should be extensible to other Floer-theoretic invariants. The basic idea is that the moduli spaces of curves admit fundamental classes in homology with coefficients in the orientation lines of the moduli spaces, and the usual construction of coherent orientations actually shows that these fundamental classes naturally map to spaces of paths twisted with appropriate coefficient systems. These twisted path spaces admit enough algebraic structure to make sense of Floer homology with coefficients in these path spaces.

Thesis advisor: John A. Baldwin / Contact geometry has played a central role in many recent advances in low-dimensional topology; e.g. in showing that knot Floer homology detects the genus of a knot and whether a knot is fibered. It has also been used to show that the unknot, trefoil, and figure eight knot are determined by their Dehn surgeries. An important problem in 3-dimensional contact geometry is the classification of Legendrian and transverse knots. Such knots come equipped with some classical invariants. New invariants from knot Floer homology have been effective in distinguishing Legendrian and transverse knots with identical classical invariants, a notoriously difficult task. The Giroux correspondence allows contact structures to be studied via purely topological constructs called open book decompositions. Transverse links are then braids about these open books, which in turn may be thought of as mapping tori of diffeomorphisms of compact surfaces with boundary having marked points, which we refer to as pointed monodromies. In the first part of this thesis, we investigate properties of the transverse invariant in knot Floer homology, in particular its behavior for transverse closures of pointed monodromies possessing certain dynamical properties. The binding of an open book sits naturally as a transverse link in the supported contact manifold. We prove that the transverse link invariant in knot Floer homology of the binding union any braid about the open book is non-zero. As an application, we show that any pointed monodromy with fractional Dehn twist coefficient greater than one has non-zero transverse invariant, generalizing a result of Plamenevskaya for braids about the unknot. In the second part of this thesis, we define invariants of Legendrian and transverse links in universally tight lens spaces using grid diagrams, generalizing those defined by Ozsvath, Szabo and Thurston. We show that our invariants are equivalent to those defined by Lisca, Ozsvath, Szabo and Stipsicz for Legendrian and transverse links in arbitrary contact 3-manifolds. Our argument involves considering braids about rational open book decompositions and filtrations on knot Floer complexes. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Mathematics.

In this thesis we present a slight generalisation of the Pearl complex or relative quantum homology to some non monotone Lagrangian submanifolds. First we develop the theory for the so called almost monotone Lagrangian submanifolds, We apply it to uniruling problems as well as estimates for the relative Gromov width. In the second part we develop the theory for toric fiber in toric Fano manifolds, recovering previous computaional results of Floer homology .

This thesis provides a partial classification of all 3-stranded pretzel knots K=P(p,q,r) with unknotting number one. Scharlemann-Thompson, and independently Kobayashi, have completely classified those knots with unknotting number one when p, q, and r are all odd. In the case where p=2m, we use the signature obstruction to greatly limit the number of 3-stranded pretzel knots which may have unknotting number one. In Chapter 3 we use Greene's strengthening of Donaldson's Diagonalization theorem to determine precisely which pretzel knots of the form P(2m,k,-k-2) have unknotting number one, where m is an integer, m>0, and k>0, k odd. In Chapter 4 we use Donaldson's Diagonalization theorem as well as an unknotting obstruction due to Ozsv\'ath and Szab\'o to partially classify which pretzel knots P(2,k,-k) have unknotting number one, where k>0, odd. The Ozsv\'ath-Szab\'o obstruction is a consequence of Heegaard Floer homology. Finally in Chapter 5 we explain why the techniques used in this paper cannot be used on the remaining cases. / text