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The Khovanov to Floer spectral sequence

1 · Prerequisites

2 · Logical flowchart

3 · Definitions, theorems and proofs

LemmaStatement: Literature-sourcedProof: AI-adaptedverified 2026-10-22 (gpt-6.1-sol)Open item page →

Filtered convergence and the scope of the Ozsváth–Szabó construction

Statement

Let (C,d,F) be a filtered chain complex over a field with an increasing filtration 0=F−1C⊆F0C⊆⋯⊆FnC=C and d(FpC)⊆FpC. Its spectral sequence stabilizes and abuts to H(C) with the image filtration, without any uniform bound outside the finite range 0≤p≤n. If a particular filtered complex has been constructed from a fixed link diagram, this convergence assertion does not itself identify filtered complexes arising from different diagrams.

Facts & Assumptions

Given: A filtered chain complex (C,d,F) with F−1C=0 and FnC=C for some finite n.

[F1]

A filtered chain complex has d(FpC)⊆FpC (Filtered chain complex).

[F2]

A finite filtration yields a spectral sequence abutting to homology with the image filtration (Bounded filtered complex spectral sequence abuts to filtered homology).

Proof

1.1F1given

The filtration has only the levels 0,…,n, so it is finite, exhaustive and separated; [F1] says each level is a subcomplex.

2.1F2step 1.1

Apply [F2] to this bounded filtered complex. Its pages stabilize and the limiting page is the associated graded of H(C) with the filtration induced by the inclusions FpC↪C.

3.1F1F2step 2.1∎

This argument identifies the abutment for the fixed filtered complex only. No map between filtered complexes for two different link diagrams occurs in [F1] or [F2], so diagram-independent filtered quasi-isomorphism type is not a consequence of this convergence result.

LemmaStatement: Literature-sourcedProof: AI-adaptedverified 2026-10-22 (gpt-6.1-sol)Open item page →

The double branched cover of the trivial two-arc tangle is a solid torus

Statement

Assume the Axiom of Choice. Let B=D2×[0,1] be a three-ball and let A={a1,a2}×[0,1] be the trivial pair of vertical properly embedded arcs, with a1≠a2 in the interior of D2. The connected two-fold cover of B∖A whose meridians about both arcs have monodromy 1∈Z/2 extends across A as a simple branched cover, and its total space is a solid torus.

Facts & Assumptions

Given: AC, the disk with two marked branch points and its product with an interval.

[F1]

A connected two-fold cover of the punctured disk is determined by the homomorphism that sends each puncture meridian to 1 (Connected covering spaces are classified by conjugacy classes of fundamental-group subgroups).

[F2]

The simple branching convention is the local square map in an oriented normal disk (Double branched cover of an oriented link). That definition concerns links in S3; the disk and product extensions needed here are constructed below.

[F3]

Euler characteristic is the alternating count of cells in a finite CW structure (Euler characteristic of a finite CW complex); a compact connected boundaryless orientable surface with Euler characteristic 2 is S2 (Classification of compact connected surfaces).

[F4]

Under AC, two disjoint smoothly embedded circles on S2 cobound an annulus (Two disjoint circles in the two-sphere cobound an annulus).

Proof

1.1F1F2givenconstructalgebra

Regard D2 as the unit disk in C. On the Riemann sphere define q(w)=(a2w2+a1)/(w2+1), with its usual values at the poles and at infinity. This is a degree-two map branched precisely over a1,a2: q(w)−a1=(a2−a1)w2/(1+w2) near w=0, and q(1/v)−a2=(a1−a2)v2/(1+v2) near v=0. The nonzero factors have local square roots, giving exactly the square charts of [F2]. Thus S=q−1(D2) is a compact oriented surface with smooth boundary and a simple branched map to D2. Its punctured restriction is connected: lifting a meridian about either branch point interchanges the two sheets. By [F1] it is the prescribed disk cover, since the two puncture meridians generate its fundamental group. This constructs the extension rather than assuming it from a link-only definition.

2.1F1F3F4step 1.1givenalgebra

Triangulate the disk with both branch points as vertices. A fan triangulation of an m-gon has V=m, E=2m−3, F=m−2 and Euler characteristic 1; inserting interior vertices preserves this count. Each open cell lifts twice except the two branch vertices, which lift once. Consequently χ(S)=2⋅1−2=0. The boundary monodromy is 1+1=0, so there are two boundary circles. Capping gives a closed connected orientable surface with Euler characteristic 2, hence a sphere by [F3]. To apply [F4] with smooth circles in the standard sphere, use the explicit model of step 1.1: the closed exterior disk C^∖int⁡D2 contains no branch value and is simply connected, so its inverse image consists of two disks by [F1]. Their boundaries are disjoint smooth circles, because q is unramified over ∂D2. Thus S is exactly the closed region between these circles in the standard Riemann sphere, and [F4] identifies it as an annulus.

3.1F1F2step 1.1step 2.1construct∎

Take q∣S×id[0,1]. Its local models along the two arcs, including their boundary endpoints, are (z,t)↦(z2,t) by step 1.1. Away from the arcs it is the connected product cover with the required meridians. Projection of the punctured product to its disk factor induces an isomorphism on fundamental groups, so [F1] identifies this restriction with the specified cover of B∖A. Transporting the constructed extension along that covering isomorphism proves the required extension. Its total space is S×[0,1]≅S1×[0,1]2, a solid torus after the usual rounding of product corners.

LemmaStatement: Literature-sourcedProof: AI-adaptedverified 2026-10-22 (gpt-6.1-sol)Open item page →

A two-strand half-twist lifts to an annular Dehn twist

Statement

Let τ be the positive half-twist mapping class of a disk interchanging two marked branch points and fixed near the disk boundary. Choose its standard supported half-turn representative in coordinates compatible with the local branched square charts, and take its unique smooth lift to the connected two-fold branched cover which fixes the annular boundary pointwise. Its smooth isotopy class relative to that boundary is the positive Dehn twist about the core when the half-twist orientation agrees with the annular orientation, and is the inverse twist when the orientation is reversed. A positive half-twist here is the usual supported rotation through +π in an oriented disk coordinate containing the two points, interpolated to the identity outside that coordinate disk; the assertion is independent of its cutoff representative.

Facts & Assumptions

Given: The disk with two branch points, its connected two-fold simple branched cover, and the supported positive half-twist. All calculations below are finite and use no choice axiom.

[F1]

Dehn twist on an oriented surface fixes the positive annular formula (θ,t)↦(θ+2πρ(t),t) for the product orientation dθ∧dt.

[F2]

Existence and uniqueness of path lifts through a covering map and Existence and uniqueness of homotopy lifts through a covering map give unique continuation and unique isotopy lifting once one sheet is specified. They apply to the ordinary cover away from the two branch points; the explicit local square coordinate fills those points below.

Proof

1.1givenconstructalgebra

An explicit oriented branched annulus. Fix c>0 and put A=(R/2πZ)×[−c,c], oriented by dθ∧dt. Its complex coordinate is z=e−t+iθ, whose complex orientation is this same orientation. The holomorphic map q(z)=z+z−1=(2cosh⁡tcos⁡θ,−2sinh⁡tsin⁡θ) identifies A with a two-fold branched cover of the closed ellipse Dc having semiaxes 2cosh⁡c,2sinh⁡c. Its deck map is ȷ(θ,t)=(−θ,−t), and its two fixed points map to 2,−2. To verify its image and degree, every point outside the real segment [−2,2] lies on a unique confocal ellipse: the expression x2/(4cosh⁡2t)+y2/(4sinh⁡2t) decreases strictly from a value greater than one to at most one as t increases from zero to c. Its two preimages have coordinates (θ,t) and (−θ,−t). Points inside that segment have the two preimages on t=0, except its endpoints. The derivative 1−z−2 vanishes precisely at z=±1; locally q(z)−2=(z−1)2/z and q(z)+2=(z+1)2/z, so each is a simple square branch in smooth complex coordinates. Both boundary components map diffeomorphically to the ellipse boundary.

2.1F1step 1.1constructalgebra

A commuting twist. Choose a smooth nondecreasing ρ:[−c,c]→[0,1], zero near −c, one near c, equal to 1/2 on [−ϵ,ϵ] for some 0<ϵ<c, and satisfying ρ(−t)=1−ρ(t). For example choose its upper half from a smooth step and reflect. Set T(θ,t)=(θ+2πρ(t),t). The symmetry makes Tȷ=ȷT modulo 2π, since 2πρ(−t)=2π−2πρ(t). It therefore descends to a smooth disk map h fixing the ellipse boundary. Near either branch it is q↦−q, because T adds π in the central strip, so descent is smooth there as well. In particular h interchanges the branch points, and T fixes both annular boundaries pointwise. By [F1], T is exactly a positive annular twist. It remains to prove the handedness of its quotient, rather than infer it merely from the interchange.

2.2step 1.1constructalgebra

An orientation-preserving disk coordinate. On the quotient of t≥ϵ write φ=−θ. Then q=(2cosh⁡tcos⁡φ,2sinh⁡tsin⁡φ). Choose r0∈(0,1) and a smooth increasing t(r) from ϵ to c on [r0,1]. Define a(r)=2cosh⁡t(r) and b(r)=2sinh⁡t(r) there. Extend a,b to [0,1] so a(0)=b(0)=0, both derivatives are strictly positive, and both are linear near zero. Here is a finite smooth construction: retain their positive derivative germs near r0, on an interval so short that each derivative integral is less than half its prescribed value at r0. Extend each derivative positively and constantly near zero, initially with total integral smaller than that value. Add a nonnegative bump in the intervening interval, with its unique scalar chosen to make the integral equal to that value. Integrating now matches every derivative and the value at r0. Thus F(r,φ)=(a(r)cos⁡φ,b(r)sin⁡φ) is a smooth odd diffeomorphism from the round disk to Dc. Smoothness and invertibility at zero follow from its positive diagonal linear formula there. Away from zero its Jacobian is a′bcos⁡2φ+ab′sin⁡2φ>0. The ellipses are strictly nested, so the equation x2/a(r)2+y2/b(r)2=1 proves global injectivity and surjectivity. Thus these are actual orientation-preserving disk coordinates, with both branch points inside r<r0.

3.1F1step 2.1step 2.2constructalgebra

The quotient is the positive half-twist, with its sign. On the central ellipse h(w)=−w, and oddness of F makes this the polar rotation φ↦φ+π. On an outer confocal ellipse, T changes φ by −2πρ(t), which modulo 2π is the angle 2π(1−ρ(t)). Consequently in the single disk coordinate of step 2.2, F−1hF(r,φ)=(r,φ+πχ(r)), where χ=1 for r≤r0 and χ(r)=2(1−ρ(t(r))) outside. This is smooth, one near the branch points, and zero near the boundary. The isotopy replacing the angle by sπχ(r) moves the two points counterclockwise through +π in an orientation-preserving coordinate. Thus it is the standard positive half-twist, not its inverse. This explicitly fixes the relative sign with the positive annular twist in [F1].

4.1F2step 1.1step 2.1step 3.1construct

Transport to the given cover and lift uniqueness. Apply the preceding model in an oriented coordinate disk supporting the given half-twist. Its branched cover is identified with the model without a covering-classification choice axiom: slit the disk along two disjoint intervals joining the branch points to its outer boundary. Over the resulting simply connected slit disk the two sheets are obtained by unique path lifting from one specified sheet point; endpoints are independent of path by homotopy lifting in [F2]. Crosswise gluing of the two slit banks is forced by the nontrivial monodromy of a small branch meridian, as the local square map shows. This is exactly the gluing of the model. The identifications are smooth locally. At the slit endpoints use the compatible base and source square charts of the chosen representative; the lifted identifications are then linear in the local square-root coordinates and fill smoothly. Outside the support disk its two exterior sheet collars are retained. The two possible lifts differ by ȷ; this deck map interchanges the two boundary components, while T fixes them. Thus precisely one lift fixes the annular boundary pointwise, and it is the transported T. Only one finite initial sheet choice was made.

5.1F1F2step 2.1step 3.1step 4.1constructalgebra∎

Representatives and orientations. Any change of smooth half-twist cutoff is an isotopy through the displayed angle functions, constant near the two points and the outer boundary. Lift it by [F2], using the boundary-fixed sheet. On the complement of the branch points, ordinary smooth local covering coordinates make the lift smooth. Near the branch points the isotopy is the fixed half-turn representative; it therefore extends in the square coordinates and is stationary there. More generally the same argument transports a supplied supported coordinate isotopy defining another standard representative of this half-twist class, chosen standard in the branch charts throughout. It gives a smooth relative-boundary isotopy of lifts. If the annular orientation is reversed, change θ to −θ while retaining t; the actual formula for T becomes (θ,t)↦(θ−2πρ(t),t). It is the inverse twist in the positively oriented annular convention. Conversely reversing the half-twist motion reverses this angle. These calculations prove the full orientation and standard-representative assertions and also explain why the other, boundary-swapping lift was excluded. The assertion concerns this smooth mapping-class lift; it does not assert that an arbitrary unnormalized smooth base germ has a smooth square-root lift.

LemmaStatement: Literature-sourcedProof: AI-generatedverified 2026-10-22 (gpt-6.1-sol)Open item page →

The genus-one hat Floer complex of an order-three lens space has rank three

Statement

Assume the ACω hat Floer disk-count theory for closed three-manifolds. For either orientation of L(3,1), the standard genus-one pointed Heegaard diagram has three intersection generators and its CF^ differential over F2 is zero. Consequently HF^(L(3,1);F2) has total rank three.

Facts & Assumptions

Given: The standard genus-one splitting and the stated filling-orientation convention, and Countable Choice.

[F1]

In the actual flat torus coordinates the meridians α=(1,0) and β=(1,3ε), ε=±1, have exactly three intersections, no nonzero normalized periodic domain, no relative disk between different generators, and only the constant relative class at an equal generator. Its proof is the explicit compact-disk lift and affine contraction in the plane, independently of a holomorphic equation. (The straight three-intersection torus diagram has no nonconstant Whitney disks)

[F2]

The actual allowed hat data have nonnegative region degrees and energy bounded by a fixed positive linear combination of those degrees. Relative homotopies preserve these degrees, since their boundary stays on the attaching circles, away from each region test point. (Nearly symmetric polygons have positive domains and degree energy bounds, Analytic foundations for disk and polygon counts)

[F3]

The full hat complex and the proved actual move maps identify its homology with the full closed-manifold invariant. The filling convention identifies the unknot-exterior meridian with its preferred longitude λU, and the attached meridian for L(3,1) with λU+3μU. (Hat Heegaard Floer complex of a closed three-manifold, Hat Heegaard Floer homology is a closed three-manifold invariant, Lens spaces in the p/q filling orientation convention)

Proof

1.1F1F3givenconstructalgebra

Parametrize the splitting torus by R2/Z2 with λU=(1,0) and μU=(0,1). Thus the two compression meridians are (1,0) and (1,3) by [F3]. They give exactly the positive-sign diagram in [F1]. Reversing the oriented splitting gives the negative sign diagram; equivalently conjugate the surface coordinate, retaining the same attaching sets. Both signs have three intersections and zero normalized periodic lattice. They therefore satisfy the corrected full-all-sector admissibility condition, including every empty sector; admissibility is not being inferred from a finite set of realized generators.

2.1F1F2step 1.1constructalgebra

Take actual allowed generic hat data for either of these literal diagrams. This need not be the flat equation: its prescribed generator charts may be retained. A nonconstant strip would compactify to a relative disk. Distinct endpoints are impossible by [F1]. For equal endpoints the explicit plane contraction of [F1] is a boundary-preserving relative homotopy to the constant map. For each region point q its degree is invariant under this homotopy: the boundary never meets q, so the boundary winding of its small disk, or equivalently the pullback divisor degree, is constant. Every region degree is consequently zero. The ACTUAL positivity and energy inequality in [F2] force zero energy, hence a constant strip. Thus there is no index-one strip for any of these allowed data. At a constant generator its operator is the exact transverse operator of real index zero, as in [F1]; it does not enter the index-one count. This argument does not assume that merely seeing quadrilateral regions excludes arbitrary multiply covered disk domains.

3.1F1F2F3step 1.1step 2.1algebra∎

The generator module is therefore F23 with zero differential. Its homology has total rank three. The actual closed-manifold invariance in [F3] identifies this diagram computation with HF^(L(3,1);F2); the negative-sign calculation proves the same for its reversed orientation. No individual Spin-c grading, absolute normalization or correction term has been inferred from this total rank calculation.

LemmaStatement: Literature-sourcedProof: AI-adaptedverified 2026-10-22 (gpt-6.1-sol)Open item page →

The trefoil double branched cover is a lens space of order three

Statement

Assume the Axiom of Choice. Let T be either oriented trefoil in S3. Its double branched cover Σ(T) is diffeomorphic, up to orientation reversal, to the lens space L(3,1) in the convention in which L(p,q) is the p/q filling of the standard unknot exterior. In particular, π1(Σ(T)) is cyclic of order three.

Facts & Assumptions

Given: AC and the closure of the two-strand braid σ1k, k=3 or k=−3, with the given knot orientation; the cover conventions of the statement. Circle coordinates below are taken modulo 2π, and the page parameter u modulo one.

[F1]

Double branched cover of an oriented link and Existence and isotopy invariance of the double branched cover of a link give the meridian-character cover and its simple branched extension, and invariance under the chosen oriented link isotopies.

[F2]

The double branched cover of the trivial two-arc tangle is a solid torus supplies the annular cover of the disk with two branch points and its product extension over an interval.

[F3]

A two-strand half-twist lifts to an annular Dehn twist gives the unique boundary-fixed smooth mapping-class lift of a positive half-twist as the positive annular twist, with the inverse for its reverse. It includes the actual orientation/sign calculation.

[F4]

Lens spaces in the p/q filling orientation convention defines L(3,1) as the unknot-exterior filling with meridian slope 3μU+λU.

[F5]

Seifert–van Kampen identifies the fundamental group with a group pushout identifies the fundamental group of a two-solid-torus union as the pushout of its boundary inclusion maps. Thickening the two pieces by collars gives its required open connected cover.

Proof

1.1F1F2F3givenconstruct

The covered disk pages and their binding fillings. Use the standard disk open book of S3 about the braid axis U: its complement of a small axis neighborhood is D2×S1, and the closed two-strand braid meets each disk in two points. This description is explicit in S3⊂C2: the axis is {z1=0} and the page parameter is u=arg⁡z1/(2π); the disk page is parametrized by z2, with z1 having the remaining modulus and chosen argument. Cut the page parameter at zero. The two moving points over the resulting interval are a braid isotopy of the twice-marked disk. Its double branched cover is the corresponding annular product by the same square-coordinate and sheet-gluing construction as [F2]. On gluing the ends, the annular monodromy is the boundary-fixed lift of the braid mapping class, hence Tk by [F3]. There is no extra deck map: the page-parameter loop near the axis bounds a small meridian disk in its neighborhood disjoint from the branch link, and has trivial meridian character. Moreover the axis itself links the two-strand braid twice, so its mod-two character is zero as well. Thus the cover of its solid-torus neighborhood consists of two ordinary copies, one for each annular boundary. In each copy the meridian is the loop u at a fixed boundary-page point. Consequently the whole branched cover is exactly the annular mapping torus with both boundary tori filled along these page-parameter meridians. The local branched models retain the smooth structures.

2.1F3step 1.1constructalgebra

Untwist the mapping torus, retaining both meridians. Write A=(R/2πZ)θ×[−1,1]t, with a positive twist T(θ,t)=(θ+2πρ(t),t), where ρ=0 near −1 and ρ=1 near 1. The mapping torus has the equivalence (θ,t,1)∼(θ+2πkρ(t),t,0). The function θ′=θ+2πkρ(t)u(mod2π) is well-defined across that equivalence and gives an actual diffeomorphism of the mapping torus with Sθ′1×[−1,1]t×Su1. Its inverse on the cut parameter interval is θ=θ′−2πkρ(t)u, with the same endpoint compatibility. At the lower boundary the filling meridian u↦(θ0,−1,u) has class (0,1) in the (θ′,u) basis. At the upper boundary the corresponding meridian has class (k,1). This computes their actual slopes, not only their intersection number.

3.1step 2.1constructalgebra

The two solid tori. Split the product at any fixed interior t. Fill its lower end along (0,1). This caps the u circle in the annulus [−1,t]×Su1 by a disk, so that piece is the solid torus V−=Sθ′1×D2. Its meridian on the common torus is m=(0,1) and its core longitude is l=(1,0). The upper filled piece is also a solid torus: the integral shear (θ′,u)↦(θ′−2πku,u) extends over its whole product collar, is single-valued because k is an integer, and takes its filling slope (k,1) to (0,1). After that shear it is the same disk-capped product as the lower piece. Before undoing the shear, its meridian on the common torus is precisely kl+m. Hence this is a genus-one gluing with that meridian slope.

4.1F1F4step 3.1constructalgebra

Identify the fixed unknot peripheral basis. Identify V− with the standard unknot exterior, using the same S3⊂C2 decomposition: EU={∣z1∣≥ε} for a small standard axis neighborhood {∣z1∣≤ε}. On its boundary the unknot meridian μU is the arg⁡z1 circle, which generates the core circle of EU, and the preferred longitude λU is the arg⁡z2 circle, which bounds its meridian disk. Thus take l=μU, m=λU by an actual product-coordinate identification. Up to the global orientation choice allowed in the statement, the other solid torus is attached with meridian kμU+λU. For k=3 this is exactly [F4]. For k=−3, the reflection (z1,z2)↦(z‾1,z2) reverses the orientation of S3, preserves the unknot, and sends μU to −μU and λU to λU. It carries the slope −3μU+λU to 3μU+λU and extends over the filled solid torus by the same meridian identification. Hence the other handedness has the same L(3,1) description up to orientation reversal. Reversing the orientation of the branch knot does not change its mod-two meridian character.

5.1F1F4F5step 1.1step 2.1step 3.1step 4.1constructalgebra∎

In EU the group is generated by μU and λU is trivial, by its product S1×D2 coordinates. Gluing the second solid torus kills the slope kμU+λU. By [F5] there are no further relations: a primitive complementary boundary longitude identifies the core generator of the attached solid torus with the corresponding word in the exterior generator, so that generator is eliminated from the pushout presentation. The group is therefore ⟨μU∣μUk=1⟩, cyclic of order ∣k∣=3. All new coordinate and slope calculations were finite; the only inherited choice use is the already declared cover and peripheral-convention branch. This proves both assertions for either oriented trefoil without replacing a meridian-slope calculation by the determinant alone.

LemmaStatement: Literature-sourcedProof: AI-adaptedverified 2026-10-22 (gpt-6.1-sol)Open item page →

The first surgery differential is the reduced Khovanov TQFT differential

Statement

Assume the ACω Heegaard Floer analytic package. Fix a finite regular diagram D of a nonempty oriented link L⊂S3, choose a basepoint p∈D away from the crossings, and choose an admissible pointed Heegaard multi-diagram subordinate to the branched-cover surgeries, with the compatible perturbation data and top-generator cycles of the link-surgery construction. Identify each first-page vertex group with the reduced state space of the corresponding crossingless resolution, based at the circle containing p. For every cube edge, the induced first differential is the mod-two map assigned by the saddle: multiplication when two resolution circles merge and comultiplication when one resolution circle splits, with the marked-circle quotient at p. Under these identifications the direct sum of edge maps is the reduced Khovanov differential of the mirror diagram D‾, based at the corresponding point, in the Ozsváth–Szabó smoothing convention.

Facts & Assumptions

Given: The ACω Heegaard Floer analytic package and a fixed finite regular diagram of a nonempty oriented link L⊂S3, a basepoint on the diagram away from the crossings, its surgery cube, and the mod-two Heegaard Floer groups and edge maps for every crossingless resolution.

[F1]

The surgery complex has the vertex groups and edge filtration described in Ozsváth–Szabó link-surgery filtered complex and exact triangle.

[F2]

The unlink vertex groups and all marked/unmarked saddle maps are identified, in simultaneous state bases, as the reduced Frobenius TQFT (Unlink resolution covers and the Heegaard Floer TQFT).

[F3]

The reduced Khovanov complex uses precisely the marked-circle quotient and merge/split maps in Reduced Khovanov cohomology of a based link over F2.

[F4]

External input — local surgery/mirror smoothing identification. Ozsváth–Szabó, arXiv:math/0309170v1, Section2 Proposition2.1 and following paragraph, pp.6–7, together with Figure1 p.2 and Theorem6.3 pp.34–35, identifies the three branched fillings with crossing/0/1 resolutions and the immediate surgery edge with the saddle. In its displayed chart the over-strand is northwest–southeast, the 0-resolution joins the left pair and the right pair, and the 1-resolution joins the top pair and bottom pair. After switching over/under to form the mirror, this is exactly A then B in the library source chart. Thus the surgery bits agree with the mirror Khovanov 0/1 bits. Only the fixed-diagram mod-two assertion is imported.

Proof

1.1F1givenalgebra

On the associated graded cube the diagonal differential is the ordinary vertex differential. Therefore its homology is the direct sum of the resolution Floer groups. The next differential is induced by the components changing one coordinate: higher polygon components lower the increasing filtration by at least two and cannot contribute to this first differential. Each surviving component is the actual surgery triangle map of that edge.

2.1F2F3step 1.1algebra

Use the SAME vertex state identification simultaneously for all incident edges. By the exact Floer supplier [F2], an unmarked merge has table 1⊗1↦1, 1⊗X,X⊗1↦X, X⊗X↦0; an unmarked split has 1↦1⊗X+X⊗1 and X↦X⊗X. Marked merge kills the input with the other circle labelled X and sends its 1 input to 1marked. Marked split sends 1marked to 1marked⊗Xnew, with the tensor order determined by which child contains the point. These last two formulas are obtained by quotienting the marked factor, not by keeping an extra unreduced factor. Tensor the identity on every untouched circle. These are exactly the reduced Frobenius saddle maps of [F3].

3.1F3F4step 2.1algebra

For an explicit grading binding, let n+(D),n−(D) be the signed crossing counts. By [F4] the surgery bit vector I is the 0/1 vector of D‾, so the normalized cochain degrees are i=∣I∣−n+(D),j~=∑c≠pdeg⁡q(ac)+∣I∣+n−(D)−2n+(D), where ac∈{1,X}, with degrees 1,−1, and the marked surviving label has reduced degree zero. Every saddle table in step 2.1 lowers the sum of label degrees by one, including marked merge and split. Increasing ∣I∣ by one therefore raises i by one and preserves j~. The spectral-sequence filtration index p=n−∣I∣ satisfies i=n−(D)−p; it is not an independent Floer cochain grading.

4.1F1F2F3F4step 1.1step 2.1step 3.1∎

The finite direct sum of the simultaneously compatible vertex identifications in [F2] is consequently an isomorphism with the normalized reduced Khovanov cube of the mirror. The actual surgery-to-mirror chart correspondence is [F4]; the grading shifts follow independently from the library cochain definition in step 3.1, rather than from an unconverted homological index in the source. No arbitrary separate edgewise changes of basis are used. This proves the direct-sum first-differential assertion for the fixed diagram, without a diagram-independence claim.

LemmaStatement: Literature-sourcedProof: AI-adaptedjudge pass (gpt-6-luna)verified 2026-10-22 (gpt-6.1-sol)Open item page →

Reduced Khovanov homology over F2 is independent of the chosen link component

Statement

Let D be a finite regular diagram of an oriented link and let p,q be any two points of D away from crossings, possibly on different link components. Over F2, the reduced Khovanov cohomology groups defined using p and q are isomorphic as bigraded vector spaces. The isomorphism need not be canonical; no diagram-change invariance is asserted here.

Facts & Assumptions

Given: The finite Khovanov cube C(D;F2) and two basepoints p,q away from its crossings.

[F1]

The circle algebra and all edge maps are the Frobenius multiplication and comultiplication specified in Khovanov Frobenius algebra and cube of resolutions and Khovanov chain complex from a diagram.

[F3]

The based reduced complex is the quotient by im⁡Xp with the stated one-degree shift (Reduced Khovanov cohomology of a based link over F2).

Proof

1.1F1F2givenalgebra

On A=F2{1,X} define N(1)=0 and N(X)=1, and on a state tensor define N as the sum of this operation over its circle factors. For multiplication, direct evaluation on (1,1),(1,X),(X,1),(X,X) gives Nm=m(N⊗id+id⊗N). For comultiplication, evaluation at 1 gives (N⊗id+id⊗N)Δ(1)=0=ΔN(1), and evaluation at X gives (N⊗id+id⊗N)Δ(X)=1⊗X+X⊗1=ΔN(X). Thus N commutes with each saddle map and hence with d. Also N2=0: applying N twice to one circle gives zero, and every pair of distinct circles occurs twice, hence cancels over F2.

2.1F1step 1.1algebra

For a basepoint p, multiplication Xp is a chain map and Xp2=0. The local operators on the circle containing p satisfy NXp+XpN=id on that factor; terms of N on all other circles commute with Xp and occur twice in the sum, so the identity holds on every state tensor.

3.1step 1.1step 2.1algebra

Put P=XpN and Q=NXp. The identity in step 2.1 and Xp2=N2=0 imply P+Q=id, P2=P, Q2=Q, and PQ=QP=0. Both maps commute with d by step 1.1. Moreover im⁡P=im⁡Xp: one inclusion follows from P=XpN, and PXp=XpNXp=Xp gives the reverse inclusion. Hence the chain module splits as im⁡Xp⊕im⁡Q.

4.1F3step 3.1algebra

The quotient map identifies C/im⁡Xp with im⁡Q. The restriction Xp:im⁡Q→im⁡P is an isomorphism with inverse N, since NXp is the identity on im⁡Q and XpN is the identity on im⁡P. The map Xp lowers raw quantum degree by two, while [F3] lowers the quotient grading by one. Thus, for each cohomological degree i, if hi,j is the dimension of unreduced cohomology in raw degree j and ri,j(p) the dimension of reduced cohomology in reduced degree j, then hi,j=ri,j−1(p)+ri,j+1(p).

5.1F2step 4.1algebra∎

The diagram has finitely many cube generators, so the sequences j↦hi,j and j↦ri,j(p) have finite support. Rewrite step 4.1 as ri,k(p)=hi,k+1−ri,k+2(p). For each parity of k, start above the largest supported reduced degree, where the latter term is zero, and recurse downward by two; this uniquely determines all reduced dimensions from the unreduced dimensions. Therefore ri,j(p)=ri,j(q) in every bidegree. Finite-dimensional vector spaces with equal dimensions are isomorphic in each bidegree; only finitely many bidegrees occur, so these isomorphisms assemble without an infinite choice principle.

LemmaStatement: Literature-sourcedProof: AI-adaptedjudge pass (gpt-6-luna)verified 2026-10-22 (gpt-6.1-sol)Open item page →

The reduced Khovanov homology of a trefoil has rank three

Statement

Let D be the oriented closure of the two-strand braid σ13, with both strands directed downward and the positive generator drawn with its southwest-to-northeast strand over its northwest-to-southeast strand. Mark a point away from the three crossings, use the A-smoothing (zero-resolution) as the through pairing, and use the B-smoothing (one-resolution) as the cap-cup pairing. The normalized reduced Khovanov cohomology of D over F2 has total rank 3. The normalized cohomological and quantum grading shifts do not change this total rank.

Facts & Assumptions

Given: The three-crossing two-strand braid closure, a basepoint, and its reduced cube over F2.

[F1]

The based reduced state space removes the marked-circle factor, and a split of that circle maps its surviving label 1 to X on the unmarked output. The supplier proof verifies that the marked action commutes with every edge map, so the quotient is a cochain complex (Reduced Khovanov cohomology of a based link over F2).

[F2]

The circle algebra has X2=0, multiplication m, and comultiplication Δ(1)=1⊗X+X⊗1, Δ(X)=X⊗X (Khovanov Frobenius algebra and cube of resolutions).

[F3]

The signed Khovanov differential squares to zero, and the finite diagram procedure outputs a finite cochain complex (The Khovanov cube differential squares to zero, The Khovanov diagram procedure terminates and returns a finite cochain complex).

[F4]

The diagram procedure enumerates all smoothing states and assigns the merge or split edge map at each crossing change (Khovanov chain complex from a diagram).

Proof

1.1F1F4givenconstruct

Let r be the number of one-resolutions. The all-through closure has two circles; for r≥1, the first cap-cup gives one circle and each additional cap-cup contributes one closed circle. Thus the eight state circle counts in lexicographic order are 2,1,1,2,1,2,2,3. Removing the marked circle gives reduced state dimensions 2,1,1,2,1,2,2,4, so the cube cochain dimensions are 2,3,6,4.

2.1F1F2F4step 1.1constructalgebra

Order states within each cohomological degree lexicographically and order free circle factors by their first encounter in a fixed diagram scan, with 1 before X. The quotient by the marked-circle action in [F1], the Frobenius maps in [F2], and the edge procedure in [F4] give d0=(101010), d1=(000110000101000011), and d2=(000000101000001010010101). In d0 each merge sends 1↦1 and X↦0. In d1 each target gets two marked-circle splits 1↦X. For d2, on target basis (1⊗1,1⊗X,X⊗1,X⊗X) the three source-state maps are 011:(1↦1⊗X, X↦X⊗X), 101:(1↦1⊗X+X⊗1, X↦X⊗X), and 110:(1↦X⊗1, X↦X⊗X). These are exactly the marked quotient split maps and the ordinary Frobenius split map, in the stated basis order.

3.1F1F3step 1.1step 2.1algebra∎

The matrix d0 has rank 1. In d1, the first two columns are independent and their sum is the third, so rank⁡d1=2. The last matrix has three independent nonzero rows, so rank⁡d2=3. By [F1] the quotient is a cochain complex, and [F3] gives its finite support; hence its cohomology dimensions are 2−1=1, 3−1−2=0, 6−2−3=1, and 4−3=1. The total rank is therefore 3, and grading shifts preserve total dimension.

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The Khovanov to branched-cover Heegaard Floer spectral sequence

Statement

Assume AC and ACω. For every nonempty oriented link L⊂S3, there is a spectral sequence over F2 whose E2 page is the reduced Khovanov cohomology Kh~∗,∗(L‾;F2) of the mirror link and whose abutment is HF^(Σ(L);F2) with its image filtration. The page identification is an isomorphism of bigraded vector spaces; this statement does not claim a diagram-independent filtered quasi-isomorphism type for the chain-level spectral sequence.

Facts & Assumptions

Given: AC, ACω, and a nonempty oriented link L.

[F0]

Every nonempty oriented link in S3 has a finite regular diagram: move it off ∞ using the link definition's ambient-isotopy convention, then choose a regular projection direction. Every component has a point away from the finite crossing set for the basepoint (Oriented links in the three-sphere and ambient isotopy, Existence of regular projections).

[F1]

The branched cover is well-defined up to oriented diffeomorphism (Existence and isotopy invariance of the double branched cover of a link).

[F2]

For a fixed diagram, the surgery construction has E2 equal to based reduced Khovanov cohomology and converges to the branched-cover Floer group (The Ozsváth–Szabó spectral sequence for a fixed link diagram).

[F3]

Over ACω, the reduced Khovanov group is independent of the chosen diagram and marked component up to bigraded isomorphism (Reduced Khovanov homology over F2 is an oriented link invariant).

[A1]

AC is used by the link-complement and covering-space construction; ACω is separately used by the Reidemeister-move and generic Floer analytic branches (The Axiom of Choice, The Axiom of Countable Choice (ACω)).

Proof

1.1F0F1F2A1givenchoose

By [F0], choose an ambient-isotopic representative L′ with a finite regular diagram D and a point on its mirror away from crossings. Apply [F2] to D; this gives a spectral sequence with E2 equal to the based reduced Khovanov group of the mirror diagram and abutment HF^(Σ(L′);F2). By [F1], HF^(Σ(L′);F2)≅HF^(Σ(L);F2).

2.1F1F2F3step 1.1

Apply [F3] to identify that page, up to bigraded isomorphism, with Kh~(L‾;F2) independently of the selected diagram and component. The convergence in [F2] and target invariance in [F1] give the stated invariant endpoints, with no diagram-independent filtered chain claim.

3.1F2F3step 1.1step 2.1∎

The two deductions above are exactly the stated endpoint construction relative to [F2] and [F3]. They preserve the fixed-diagram scope of the filtered construction and use only the invariant isomorphism classes of its endpoints. Thus the formal assembly is complete relative to these two exact supplier interfaces.

External-input boundary

The fixed-diagram supplier uses the explicitly labelled external Ozsváth–Szabó surgery and unlink-map inputs, with exact locators and reading limits recorded in those suppliers and the run source receipt. The reduced link-invariance supplier supplies the independent based-link passage. This proof assembles those results; it does not reconstruct their imported parts or claim a diagram-independent filtered chain type. AC for the branched cover and ACω for the analytic/Reidemeister branches remain the separate assumptions of the Statement.

4 · Examples, counterexamples and false statements

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