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 "title": "Floer homology",
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 "excerpt": "Floer homology is an infinite-dimensional analog of Morse homology introduced by Andreas Floer around 1986, giving invariants in symplectic topology and of 3-manifolds and knots.",
 "snippet": "Floer homology is an infinite-dimensional analog of Morse homology introduced by Andreas Floer around 1986, giving invariants in symplectic topology and of 3-manifolds and knots.",
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 "markdown": "# Floer homology\n\nFloer homology is an infinite-dimensional analog of [Morse homology](https://www.edgepedia.org/morse-homology) in which the chain groups are generated by critical points of an action functional and the differential counts solutions of a perturbed Cauchy–Riemann equation.<sup>[1](https://link.springer.com/book/10.1007/978-1-4471-5496-9)</sup> It yields rigorously defined invariants that can be viewed as homology groups of infinite-dimensional cycles<sup>[2](https://www.cambridge.org/core/books/floer-homology-groups-in-yangmills-theory/AC2BC9FE7B25EE8339E80C22335680F3)</sup>, and it is central to symplectic topology and low-dimensional topology: it gives lower bounds on periodic orbits (the Arnold conjecture)<sup>[1](https://link.springer.com/book/10.1007/978-1-4471-5496-9)</sup>, invariants of 3-manifolds and contact structures<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup>, and knot invariants that detect genus, fiberedness, and the unknot.<sup>[4](https://ar5iv.labs.arxiv.org/html/1401.7107)</sup>\n\n| Key fact | Detail |\n|---|---|\n| Type | Infinite-dimensional Morse homology; chains are critical points of an action functional, differential counts pseudoholomorphic curves<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup> |\n| Hamiltonian version | Under suitable assumptions HF\\*(M, ω, H) ≅ H\\*(M), proving that the number of 1-periodic orbits is at least the sum of Betti numbers<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> |\n| Instanton version | Chains generated by flat SU(2) connections on a homology sphere, relatively Z/8-graded; its Euler characteristic is the Casson invariant<sup>[6](https://scgp.stonybrook.edu/wp-content/uploads/2014/01/ruberman_simons-instanton-notes.pdf)</sup> |\n| Heegaard version | Lagrangian Floer homology of the tori \\( T_{\\alpha} \\) and \\( T_{\\beta} \\) in the symmetric product \\( \\mathrm{Sym}^{g}(\\Sigma) \\) of a Heegaard surface<sup>[7](https://annals.math.princeton.edu/wp-content/uploads/annals-v159-n3-p03.pdf)</sup> |\n| Equivalences | For closed 3-manifolds, Heegaard Floer, monopole Floer, and embedded contact homology agree: HF˚(Y) = HM˚(Y) = ECH(Y, α)<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> |\n| Computation | Grid-diagram complexes grow like n! in grid size; programs handle grid number up to 13, and representing the K3 surface needs a grid of size at least 88<sup>[8](https://web.stanford.edu/~cm5/proc_ecm.pdf)</sup> |\n\n## How it works\n\nThe Hamiltonian version starts from the symplectic action functional on the loop space of a symplectic manifold (M, ω): for a capping disc v,\n\n\\[ A_{H}(\\gamma) := -\\int_{D} v^{*}\\omega + \\int_{0}^{1} H_{t}(\\gamma(t))\\,dt, \\]\n\nwhich is well defined when \\( \\omega \\) vanishes on \\( \\pi_{2}(M) \\). A loop is a critical point of \\( A_{H} \\) exactly when it is a 1-periodic orbit of the Hamiltonian flow.<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup> Negative gradient flow lines of \\( A_{H} \\) are solutions of\n\n\\[ \\frac{\\partial u}{\\partial s} + J_{t}(u)\\left(\\frac{\\partial u}{\\partial t} - X_{H_{t}}(u)\\right) = 0, \\]\n\na perturbed Cauchy–Riemann equation: with t-independent data it recovers Morse gradient flow, and for \\( H = 0 \\) and constant \\( J \\) it is the J-holomorphic curve equation.<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup> The grading of a non-degenerate 1-periodic orbit is its Conley–Zehnder index, an intersection number between the linearized path of symplectic matrices along the orbit and the cycle of matrices having 1 as an eigenvalue, with Ind(γ) := n − µ(Φ)<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup>; it is well defined modulo \\( 2N \\), where \\( N \\) is the minimal [Chern number](https://www.edgepedia.org/chern-number) of (M, ω).<sup>[9](https://people.math.ethz.ch/~salamon/PREPRINTS/lowdim.pdf)</sup>\n\nThe differential counts unparametrized flow lines between orbits of adjacent index, \\( \\partial_{k}(\\gamma) := \\sum_{\\mathrm{Ind}(\\eta)=k-1} n(\\gamma,\\eta)\\,\\eta \\), and the identity \\( \\partial^{2} = 0 \\) follows from Gromov's compactness theorem for J-holomorphic curves, which controls the limits of sequences of trajectories.<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup> Transversality of the moduli spaces holds for a [dense set](https://www.edgepedia.org/dense-set) of compatible almost complex structures by the Sard–Smale theorem.<sup>[10](https://www.numdam.org/item/10.5802/afst.1373.pdf)</sup> Invariance under changes of (H, J) comes from continuation maps: for two regular pairs joined by a regular asymptotically constant path, there is a chain map \\( \\Phi_{\\chi}: CF^{*}(H_{-}) \\to CF^{*}(H_{+}) \\) inducing an isomorphism on homology independent of the path.<sup>[11](https://math.ruhr-uni-bochum.de/fileadmin/content/Mathematik/Floer_Zentrum/reading_course_on_floer_homology__part_6_22.06.2023.pdf)</sup>\n\n## How it is done\n\nA Hamiltonian Floer complex is built in this order. First choose a non-degenerate Hamiltonian H and a compatible almost complex structure J; the chain group \\( CF^{*}(M, \\omega, H) \\) is the [free abelian group](https://www.edgepedia.org/free-abelian-group) generated by the 1-periodic orbits, graded by the Conley–Zehnder index when \\( c_{1} \\) vanishes on \\( \\pi_{2}(M) \\).<sup>[12](https://www.math.stonybrook.edu/~joa/PUBLICATIONS/TOPMETDYN-LEC.pdf)</sup> Second, define the differential by counting solutions of the Floer equation connecting orbits of index difference one.<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup> Third, prove compactness: for continuation cylinders an energy estimate \\( E(u) \\leq A_{H_{-}}(x_{-}) - A_{H_{+}}(x_{+}) + \\Delta(H^{s}) \\), where \\( \\Delta(H^{s}) \\) bounds the s-derivative of the Hamiltonian, requires the asymptotically constant condition, and broken configurations decompose the boundary of the compactified one-dimensional moduli space, which is what makes the continuation map a chain map.<sup>[11](https://math.ruhr-uni-bochum.de/fileadmin/content/Mathematik/Floer_Zentrum/reading_course_on_floer_homology__part_6_22.06.2023.pdf)</sup> Fourth, achieve transversality by perturbing J.<sup>[10](https://www.numdam.org/item/10.5802/afst.1373.pdf)</sup> Finally, prove invariance via the continuation isomorphism.<sup>[11](https://math.ruhr-uni-bochum.de/fileadmin/content/Mathematik/Floer_Zentrum/reading_course_on_floer_homology__part_6_22.06.2023.pdf)</sup> For a small time-independent Morse function the Floer complex is isomorphic to the Morse complex, so the homology computes the homology of the manifold.<sup>[5](https://www.ub.edu/topologia/seminars/Floer.pdf)</sup>\n\n## Origin\n\nThe geometric input is Gromov's theory of pseudo-holomorphic curves in symplectic manifolds, published in Inventiones mathematicae in 1985.<sup>[13](https://doi.org/10.1007/bf01388806)</sup> Andreas Floer combined this with new ideas about [Morse theory](https://www.edgepedia.org/morse-theory), gauge theory, and Casson's approach to homology 3-spheres.<sup>[6](https://scgp.stonybrook.edu/wp-content/uploads/2014/01/ruberman_simons-instanton-notes.pdf)</sup> Around 1986 Floer generalized Morse theory to prove the Arnold conjecture for monotone symplectic manifolds.<sup>[14](https://people.math.ethz.ch/~salamon/PREPRINTS/warwick.pdf)</sup> In instanton homology the chains are generated by irreducible SU(2)-representations of the fundamental group of a homology 3-sphere, the critical points of the Chern–Simons functional, and the gradient flow lines are self-dual Yang–Mills instantons on M × ℝ.<sup>[14](https://people.math.ethz.ch/~salamon/PREPRINTS/warwick.pdf)</sup> His founding papers are \"The unregularized gradient flow of the symplectic action\" (Communications on Pure and Applied Mathematics, 1988), which defines on a subset of the path space joining two Lagrangian submanifolds a flow whose trajectories solve the Cauchy–Riemann equation, with compactness and transversality results for bounded trajectories<sup>[15](https://doi.org/10.1002/cpa.3160410603)</sup>; \"An instanton-invariant for 3-manifolds\" (Communications in Mathematical Physics, 1988)<sup>[16](https://doi.org/10.1007/bf01218578)</sup>; and \"Symplectic fixed points and holomorphic spheres\" (Communications in Mathematical Physics, 1989).<sup>[17](https://doi.org/10.1007/bf01260388)</sup> Atiyah conjectured that this instanton homology is isomorphic to a Lagrangian Floer homology built from a [Heegaard splitting](https://www.edgepedia.org/heegaard-splitting)<sup>[14](https://people.math.ethz.ch/~salamon/PREPRINTS/warwick.pdf)</sup>; the mapping-cylinder case was proved by Dostoglou and Salamon in 1994.<sup>[18](https://doi.org/10.2307/2118573)</sup>\n\n## Variants\n\n**Hamiltonian Floer homology**, the first flavor, is defined by Floer; under suitable assumptions it is isomorphic to \\( H^{*}(M) \\).<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> **Lagrangian Floer homology** counts perturbed holomorphic strips between intersection points of a Lagrangian L with its image, with grading defined only modulo the minimal Maslov number \\( N_{L} \\).<sup>[19](https://arxiv.org/abs/math/0512037)</sup> **Instanton Floer homology** uses flat SU(2) connections and a Z/8 relative grading.<sup>[6](https://scgp.stonybrook.edu/wp-content/uploads/2014/01/ruberman_simons-instanton-notes.pdf)</sup> **Heegaard Floer homology** HF(Y, s), HF⁺, HF⁻, HF∞ for closed oriented 3-manifolds with Spin^c structure is the Lagrangian Floer homology of the tori \\( T_{\\alpha} \\) and \\( T_{\\beta} \\) in \\( \\mathrm{Sym}^{g}(\\Sigma) \\), with differential counting pseudo-holomorphic disks; the groups are invariants of Y independent of the Heegaard splitting, attaching circles, basepoint, and complex structures.<sup>[7](https://annals.math.princeton.edu/wp-content/uploads/annals-v159-n3-p03.pdf)</sup> **Knot Floer homology** refines the hat theory by a filtration indexed by a knot K; it is a bi-graded finitely generated group whose graded [Euler characteristic](https://www.edgepedia.org/euler-characteristic) is the Alexander–Conway polynomial<sup>[4](https://ar5iv.labs.arxiv.org/html/1401.7107)</sup>, and link, sutured, and bordered-style variants extend it to links, sutured manifolds, and manifolds with parameterized boundary.<sup>[20](https://ar5iv.labs.arxiv.org/html/1310.3418)</sup> **Monopole Floer homology** is built from the Chern–Simons–Dirac functional and the Seiberg–Witten monopole equations, with the same three flavors and formal properties as [Heegaard Floer homology](https://www.edgepedia.org/heegaard-floer-homology).<sup>[21](https://www.gokovagt.org/proceedings/2012/ggt12-kutluhan.pdf)</sup> **Embedded contact homology** counts Reeb orbits in a contact 3-manifold.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> **Rabinowitz–Floer homology** RFH(Σ, V) is defined by Cieliebak, Frauenfelder, and Oancea (2010) using the Rabinowitz action functional with a [Lagrange multiplier](https://www.edgepedia.org/lagrange-multiplier).<sup>[22](https://doi.org/10.24033/asens.2137)</sup>\n\n## Applications\n\nThe Arnold conjecture asserts that the number of 1-periodic trajectories of a non-degenerate Hamiltonian system is bounded below by the dimension of the homology of the underlying manifold.<sup>[1](https://link.springer.com/book/10.1007/978-1-4471-5496-9)</sup> Conley and Zehnder proved it for the 2n-torus; Floer proved it for monotone symplectic manifolds.<sup>[9](https://people.math.ethz.ch/~salamon/PREPRINTS/lowdim.pdf)</sup> Hofer and Salamon, in \"Floer homology and Novikov rings\" (1995), proved it for compact symplectic manifolds assuming either that c₁ vanishes on π₂(M) or that the minimal Chern number is at least half the dimension, including Calabi–Yau manifolds; for weakly monotone manifolds the Floer groups agree with cohomology with Novikov ring coefficients.<sup>[23](https://doi.org/10.1007/978-3-0348-9217-9_20)</sup> The general case was proved by Fukaya–Ono (Topology 38, 1999), Liu–Tian (Journal of Differential Geometry 49, 1998), and Ruan.<sup>[24](https://www.math.stonybrook.edu/Courses/MAT645/200001/MAT645S00.pdf)</sup>\n\nIn dimension three, Taubes used embedded contact homology to prove the Weinstein conjecture: every closed contact 3-manifold has at least one closed Reeb orbit.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> Monopole Floer homology underlies Manolescu's 2016 result that for every \\( n \\geq 5 \\) there is a non-triangulable topological manifold of dimension n.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> Knot Floer homology detects the Seifert genus: in the hat version, \\(g(K) = \\max\\{a \\mid \\widehat{HFK}(K, a) \\neq 0\\}\\), so it distinguishes every non-trivial knot from the unknot<sup>[25](https://users.math.msu.edu/users/heddenma/Introduction%20to%20Heegaard%20FLoer%20homology.pdf)</sup><sup> • </sup><sup>[32](https://androma.org/theorems/13913)</sup>, and it encodes slice genus and fiberedness.<sup>[4](https://ar5iv.labs.arxiv.org/html/1401.7107)</sup> The concordance invariant τ(K) ∈ ℤ is extracted from the knot filtration, and Hom used the full complex to show the smooth concordance group of topologically slice knots admits a ℤ^∞ summand.<sup>[4](https://ar5iv.labs.arxiv.org/html/1401.7107)</sup> The three gauge-theoretic and symplectic theories agree: HF˚(Y) = HM˚(Y) = ECH(Y, α), proved by Taubes, Kutluhan–Lee–Taubes, and Colin–Ghiggini–Honda.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup>\n\nIn 2025, Colin, Ghiggini, and Honda proved the equivalence of the sutured versions of Heegaard Floer homology, monopole Floer homology, and embedded contact homology; as applications, the knot versions of Heegaard Floer and embedded contact homology are equivalent, and product sutured manifolds are characterized by carrying an adapted [Reeb vector field](https://www.edgepedia.org/reeb-vector-field) without periodic orbits.<sup>[26](https://doi.org/10.4171/jems/1719)</sup> Also in 2025, Beliakova, Putyra, Robert, and Wagner proved a suitably updated version of the 2005 Dunfield–Gukov–Rasmussen conjecture, relating reduced triply graded Khovanov–Rozansky homology to knot Floer homology by two spectral sequences, the new one of Bockstein type; the intermediate homology and the reduced triply graded Khovanov–Rozansky homology detect the unknot, the two trefoils, the figure eight knot, and the cinquefoil.<sup>[27](https://doi.org/10.4171/jems/1626)</sup> In August 2026, Bai, Shelukhin, Wang, and Xu announced a proof of the Arnold–Givental conjecture in full generality, \\( \\#(\\varphi(L) \\cap L) \\geq \\dim_{\\mathbb{F}_{2}} H_{*}(L; \\mathbb{F}_{2}) \\) for a Hamiltonian diffeomorphism φ such that φ(L) intersects L transversely, where L is the fixed-point set of an anti-symplectic involution, combining integral Floer theory with a ℤ/2-equivariant localization idea.<sup>[28](https://doi.org/10.48550/arxiv.2608.27242)</sup>\n\n## Limitations and alternatives\n\n**Bubbling and transversality.** Holomorphic spheres in (M, ω) obstruct the Hamiltonian construction, and both spheres and disks with boundary on L obstruct the Lagrangian one; in the Lagrangian case the multiply-covered versus somewhere-injective dichotomy fails because there exist holomorphic disks that are neither.<sup>[19](https://arxiv.org/abs/math/0512037)</sup> For the general Arnold conjecture, when pseudoholomorphic spheres of negative Chern number are present, geometric perturbations may not yield regular moduli spaces, and abstract regularization is required: polyfold theory describes the compact moduli space as the zero set of an sc-Fredholm section, and with sphere bubbles of nontrivial isotropy the perturbations are multi-valued, yielding rational counts.<sup>[29](https://link.springer.com/article/10.1007/s00029-021-00680-z)</sup>\n\n**Grading and definability.** The Conley–Zehnder grading is only modulo 2N<sup>[9](https://people.math.ethz.ch/~salamon/PREPRINTS/lowdim.pdf)</sup> and the Lagrangian grading only modulo the minimal Maslov number \\( N_{L} \\)<sup>[19](https://arxiv.org/abs/math/0512037)</sup>; instanton Floer homology is graded modulo 8, and its compactness requires excluding bubbling of instantons on \\( S^{4} \\).<sup>[30](https://math.berkeley.edu/~katrin/papers/survey.pdf)</sup> Lagrangian Floer homology is not isomorphic to the singular homology of L in general and can vanish completely for displaceable Lagrangians.<sup>[19](https://arxiv.org/abs/math/0512037)</sup> In the Atiyah–Floer setting the relevant symplectic moduli space \\( R_{\\Sigma} \\) of flat SU(2)-connections is singular, so the symplectic Floer homology is not strictly defined there<sup>[30](https://math.berkeley.edu/~katrin/papers/survey.pdf)</sup>; the Atiyah–Floer conjecture had been partially proved by Daemi, Fukaya, and Lipyanskiy in 2021.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup>\n\n**Computation and comparison.** Heegaard Floer theory was developed as a more computable alternative to [Seiberg–Witten theory](https://www.edgepedia.org/seiberg-witten-theory), replacing gauge theory with pseudo-holomorphic curve counts.<sup>[8](https://web.stanford.edu/~cm5/proc_ecm.pdf)</sup> Sarkar and Wang gave an algorithm computing \\( HF(Y) \\) for any closed oriented 3-manifold, and all flavors of HF are algorithmically computable, but the known algorithms are far from polynomial time.<sup>[20](https://ar5iv.labs.arxiv.org/html/1310.3418)</sup> Grid complexes grow like n!, programs handle grid number up to 13, and the [K3 surface](https://www.edgepedia.org/k3-surface) needs a grid of size at least 88; whether the unknotting problem can be solved in polynomial time remains open.<sup>[8](https://web.stanford.edu/~cm5/proc_ecm.pdf)</sup> Knot Floer homology categorifies (upgrades a polynomial invariant to richer algebraic structure) the [Alexander polynomial](https://www.edgepedia.org/alexander-polynomial) just as Khovanov homology categorifies the Jones polynomial, and a conjecture of Rasmussen relates the two<sup>[20](https://ar5iv.labs.arxiv.org/html/1310.3418)</sup>; symplectic Khovanov homology, defined as Lagrangian Floer homology of a Lagrangian in a Hilbert scheme, coincides with ordinary Khovanov homology over ℚ by work of Abouzaid and Smith.<sup>[3](https://web.stanford.edu/~cm5/286.pdf)</sup> A graph TQFT for the minus flavor of Heegaard Floer homology, extending the Ozsváth–Szabó TQFT to cobordisms with disconnected ends, records that a proof extending the \\( HF = HM = ECH \\) isomorphisms to the level of 4-manifold invariants has not yet appeared.<sup>[31](https://msp.org/gt/2026/30-2/gt-v30-n2-p01-p.pdf)</sup>\n\n## References\n\n1. [Morse Theory and Floer Homology (Audin & Damian, Universitext, Springer, 2014)](https://link.springer.com/book/10.1007/978-1-4471-5496-9)\n2. [Floer Homology Groups in Yang-Mills Theory (S. K. Donaldson, Cambridge Tracts in Mathematics 147, 2009)](https://www.cambridge.org/core/books/floer-homology-groups-in-yangmills-theory/AC2BC9FE7B25EE8339E80C22335680F3)\n3. [An Overview of Floer Homologies (Stanford lecture notes)](https://web.stanford.edu/~cm5/286.pdf)\n4. [An introduction to knot Floer homology](https://ar5iv.labs.arxiv.org/html/1401.7107)\n5. [Introduction to Floer Homology (seminar notes, Universitat de Barcelona)](https://www.ub.edu/topologia/seminars/Floer.pdf)\n6. [An Introduction to Floer Homology (lecture notes, Daniel Ruberman)](https://scgp.stonybrook.edu/wp-content/uploads/2014/01/ruberman_simons-instanton-notes.pdf)\n7. [Holomorphic disks and topological invariants for closed three-manifolds (Ozsváth–Szabó, Annals of Mathematics 159(3))](https://annals.math.princeton.edu/wp-content/uploads/annals-v159-n3-p03.pdf)\n8. [Combinatorial Heegaard Floer homology (Manolescu, ECM survey)](https://web.stanford.edu/~cm5/proc_ecm.pdf)\n9. [Floer homology and Novikov rings (Hofer–Salamon)](https://people.math.ethz.ch/~salamon/PREPRINTS/lowdim.pdf)\n10. [Introduction to the basics of Heegaard Floer homology (Annals of the Fourier Institute)](https://www.numdam.org/item/10.5802/afst.1373.pdf)\n11. [Reading course on Floer homology, part 6: Continuation and computation (Ruhr-Universität Bochum, 2023)](https://math.ruhr-uni-bochum.de/fileadmin/content/Mathematik/Floer_Zentrum/reading_course_on_floer_homology__part_6_22.06.2023.pdf)\n12. [Topological Methods in the Quest for Periodic Orbits (Joa Weber, lecture notes)](https://www.math.stonybrook.edu/~joa/PUBLICATIONS/TOPMETDYN-LEC.pdf)\n13. [M. Gromov (1985). Pseudo holomorphic curves in symplectic manifolds. Inventiones mathematicae.](https://doi.org/10.1007/bf01388806)\n14. [Instanton homology and symplectic fixed points (Dostoglou–Salamon)](https://people.math.ethz.ch/~salamon/PREPRINTS/warwick.pdf)\n15. [Andreas Floer (1988). The unregularized gradient flow of the symplectic action. Communications on Pure and Applied Mathematics.](https://doi.org/10.1002/cpa.3160410603)\n16. [Andreas Floer (1988). An instanton-invariant for 3-manifolds. Communications in Mathematical Physics.](https://doi.org/10.1007/bf01218578)\n17. [Andreas Floer (1989). Symplectic fixed points and holomorphic spheres. Communications in Mathematical Physics.](https://doi.org/10.1007/bf01260388)\n18. [Stamatis Dostoglou, Dietmar A. Salamon (1994). Self-Dual Instantons and Holomorphic Curves. Annals of Mathematics.](https://doi.org/10.2307/2118573)\n19. [A Lagrangian Piunikhin-Salamon-Schwarz morphism and two comparison homomorphisms in Floer homology](https://arxiv.org/abs/math/0512037)\n20. [A survey of Heegaard Floer homology](https://ar5iv.labs.arxiv.org/html/1310.3418)\n21. [Lectures on the equivalence of Heegaard Floer and Seiberg–Witten Floer homologies (Kutluhan et al.)](https://www.gokovagt.org/proceedings/2012/ggt12-kutluhan.pdf)\n22. [Kai Cieliebak, Urs Frauenfelder, Alexandru Oancea (2010). Rabinowitz Floer homology and symplectic homology. Annales Scientifiques de l École Normale Supérieure.](https://doi.org/10.24033/asens.2137)\n23. [Helmut Hofer, Dietmar A. Salamon (1995). Floer homology and Novikov rings. Birkhäuser Basel eBooks.](https://doi.org/10.1007/978-3-0348-9217-9_20)\n24. [MAT 645 Introduction to Floer theory syllabus (Joa Weber, Stony Brook, Spring 2000)](https://www.math.stonybrook.edu/Courses/MAT645/200001/MAT645S00.pdf)\n25. [An introduction to Heegaard Floer homology (Hedden notes)](https://users.math.msu.edu/users/heddenma/Introduction%20to%20Heegaard%20FLoer%20homology.pdf)\n26. [Vincent Colin, Paolo Ghiggini, Ko Honda (2025). Sutured Heegaard Floer and embedded contact homologies are isomorphic. Journal of the European Mathematical Society.](https://doi.org/10.4171/jems/1719)\n27. [Anna Beliakova and colleagues (2025). A proof of Dunfield–Gukov–Rasmussen conjecture. Journal of the European Mathematical Society.](https://doi.org/10.4171/jems/1626)\n28. [Bai, Shaoyun and colleagues (2026). A proof of the Arnold-Givental conjecture. arXiv (Cornell University).](https://doi.org/10.48550/arxiv.2608.27242)\n29. [A polyfold proof of the Arnold conjecture (Selecta Mathematica)](https://link.springer.com/article/10.1007/s00029-021-00680-z)\n30. [An approach to the Atiyah-Floer conjecture via instanton Floer homology with Lagrangian boundary conditions (Wehrheim–Woodward survey)](https://math.berkeley.edu/~katrin/papers/survey.pdf)\n31. [Graph cobordisms and Heegaard Floer homology (Zemke, Geometry & Topology 30(2), 2026)](https://msp.org/gt/2026/30-2/gt-v30-n2-p01-p.pdf)\n32. [androma.org](https://androma.org/theorems/13913)\n\n---\n*Topic: Encyclopedia › Physical world and mathematics › Mathematics and statistics › Geometry and topology › Geometric topology and low-dimensional topology*\n\n*Initially written Sep 29, 2026 · Reviewed: Sep 30, 2026 · Edited: Sep 30, 2026; Oct 15, 2026 · Last review: Sep 30, 2026*\n\n*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*\n\nLicense: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license\n",
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 "credit": "\"Floer homology\", Edgepedia (EdgeChat), https://www.edgepedia.org/floer-homology. Edgepedia Community License 1.0.",
 "credit_md": "\"[Floer homology](https://www.edgepedia.org/floer-homology)\", Edgepedia (EdgeChat), [https://www.edgepedia.org/floer-homology](https://www.edgepedia.org/floer-homology). [Edgepedia Community License 1.0](https://www.edgepedia.org/edgepedia/license).",
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 "speakable": "Floer homology is an infinite-dimensional analog of Morse homology introduced by Andreas Floer around 1986, giving invariants in symplectic topology and of 3-manifolds and knots."
}