Equivariant Floer cohomology for contactomorphisms of quotient spaces
Pith reviewed 2026-05-21 12:49 UTC · model grok-4.3
The pith
Equivariant contact Floer cohomology shows that quotients of fillable contact manifolds are orderable.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central claim is that an equivariant formulation of contact Floer cohomology, equipped with its k[[x]]-module structure, yields a nonlinear Maslov index analogue in which mapping cones of continuation maps detect crossings with the discriminant; this detection, once lifted to an infinity-functor on a suitable infinity-categorification of the Eliashberg-Polterovich relation, establishes orderability for the contactomorphism groups of quotients of fillable contact manifolds such as RP^{2n-1}.
What carries the argument
The equivariant contact Floer cohomology as a k[[x]]-module whose mapping cones of continuation maps detect crossings of the discriminant.
If this is right
- The contactomorphism group of RP^{2n-1} is orderable for every n.
- Any contact manifold obtained as a quotient of a fillable manifold by a compatible finite group action is orderable.
- The nonlinear Maslov index analogue supplies a new algebraic invariant for paths of contactomorphisms on these quotients.
- Orderability follows whenever the module structure on equivariant Floer cohomology changes across the discriminant.
Where Pith is reading between the lines
- The same module-structure technique might apply to quotients by groups that are not finite if suitable compatibility conditions can be formulated.
- Explicit low-dimensional calculations of the index on RP^3 could provide an independent check on whether positive loops exist.
- The infinity-functor lift may connect to other chain-level constructions in symplectic geometry that handle non-canonical choices.
Load-bearing premise
The finite group actions on the contact manifold must be compatible with a symplectic filling in a way that permits a well-defined equivariant contact Floer cohomology theory and the associated k[[x]]-module structure.
What would settle it
A concrete computation for a loop in the contactomorphism group of RP^3 that crosses the discriminant yet produces a mapping cone whose k[[x]]-module structure fails to register the crossing would falsify the detection mechanism.
Figures
read the original abstract
This paper establishes the orderability of contact manifolds which are quotients of fillable contact manifolds under finite group actions compatible with the filling, the prototypical example being $\mathbb{R}P^{2n-1}$ as the quotient of $S^{2n-1}$. Our approach employs an equivariant formulation of the so-called contact Floer cohomology theory. This leads us to develop an analogue of Givental's nonlinear Maslov index using the $\mathbf{k}[[x]]$-module structure on an equivariant version of contact Floer cohomology. A key idea is that mapping cones of continuation maps detect crossings with the discriminant (recall that Givental's index is a continuous integer valued function on the complement of the discriminant). To properly handle the inherent non-canonicity in defining such mapping cones, we lift the structure of contact Floer cohomology to chain level by defining it as an $\infty$-functor on a suitable $\infty$-categorification of the Eliashberg-Polterovich orderability relation on the universal cover of the contactomorphism group.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. This paper establishes the orderability of contact manifolds which are quotients of fillable contact manifolds under finite group actions compatible with the filling, the prototypical example being RP^{2n-1} as the quotient of S^{2n-1}. It employs an equivariant formulation of contact Floer cohomology to develop an analogue of Givental's nonlinear Maslov index via the k[[x]]-module structure. Mapping cones of continuation maps detect crossings with the discriminant, with non-canonicity handled by lifting the structure to an ∞-functor on an ∞-categorification of the Eliashberg-Polterovich orderability relation on the universal cover of the contactomorphism group.
Significance. If the constructions are carried through rigorously, the result would be a meaningful advance in contact geometry by extending orderability to a new class of quotient manifolds and supplying a Floer-theoretic detection mechanism for the discriminant. The ∞-categorical handling of continuation-map cones addresses a recurring technical obstacle in the field and may prove reusable in other equivariant or non-canonical settings.
major comments (2)
- [§3] §3: The construction of the equivariant contact Floer cohomology on the quotient relies on the finite group action being compatible with a symplectic filling to ensure the theory descends; however, the argument that this compatibility produces well-defined, transverse equivariant moduli spaces is only outlined and requires a complete Fredholm and compactness analysis to support the subsequent claims.
- [§5.2] §5.2, around the definition of the mapping cone: the assertion that the cone of the lifted continuation map is non-trivial precisely when the path crosses the discriminant is central to the nonlinear Maslov index analogue, yet the precise chain-level or ∞-categorical mechanism that guarantees this detection property for the quotient case is not fully derived from the Eliashberg-Polterovich relation.
minor comments (3)
- [§4] The notation for the ∞-categorification of the Eliashberg-Polterovich relation would benefit from an explicit description of the objects, 1-morphisms, and higher cells, perhaps accompanied by a diagram.
- [Introduction] Several references to prior work on equivariant Floer cohomology and ∞-categorical symplectic geometry appear to be missing or outdated; a brief comparison paragraph situating the present lift against existing approaches would improve readability.
- [Theorem 1.1] In the statement of the main theorem, the precise range of dimensions n for which the RP^{2n-1} example holds should be stated explicitly rather than left implicit.
Simulated Author's Rebuttal
We thank the referee for their positive assessment and constructive feedback on our manuscript. The comments identify areas where additional detail will strengthen the exposition, and we address each point below with plans for revision.
read point-by-point responses
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Referee: [§3] §3: The construction of the equivariant contact Floer cohomology on the quotient relies on the finite group action being compatible with a symplectic filling to ensure the theory descends; however, the argument that this compatibility produces well-defined, transverse equivariant moduli spaces is only outlined and requires a complete Fredholm and compactness analysis to support the subsequent claims.
Authors: We agree that the current outline in §3 would benefit from a more self-contained Fredholm and compactness argument. In the revised version we will expand this section to include a complete analysis: we will verify that the finite group action, being compatible with the symplectic filling, induces equivariant almost complex structures for which the linearized operators are Fredholm with the expected index, and that the standard SFT-style compactness arguments carry over to the equivariant setting by controlling the energy and using the group-equivariance to rule out bubbling. This will explicitly confirm that the resulting moduli spaces are transverse and that the descended theory on the quotient is well-defined. revision: yes
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Referee: [§5.2] §5.2, around the definition of the mapping cone: the assertion that the cone of the lifted continuation map is non-trivial precisely when the path crosses the discriminant is central to the nonlinear Maslov index analogue, yet the precise chain-level or ∞-categorical mechanism that guarantees this detection property for the quotient case is not fully derived from the Eliashberg-Polterovich relation.
Authors: We appreciate this observation. The manuscript already lifts the continuation maps to an ∞-functor on the ∞-categorification of the Eliashberg-Polterovich relation and uses the k[[x]]-module structure to detect non-triviality of cones. However, the explicit chain-level identification of when the cone becomes non-trivial in the quotient setting can be made more transparent. In the revision we will insert a short subsection deriving this detection property directly from the ∞-categorical data, showing that a crossing of the discriminant corresponds to a non-trivial homotopy class in the cone via the equivariant action and the module structure, thereby completing the derivation from the underlying orderability relation. revision: yes
Circularity Check
No significant circularity detected in derivation chain
full rationale
The paper constructs an equivariant contact Floer cohomology theory for quotients under compatible finite group actions, then develops an analogue of Givental's nonlinear Maslov index via the k[[x]]-module structure and mapping cones of continuation maps. These are lifted to an ∞-functor on an ∞-categorification of the Eliashberg-Polterovich orderability relation to address non-canonicity. No quoted equations or steps in the abstract reduce the target orderability result to a self-definition, fitted parameter, or load-bearing self-citation by construction. The approach builds on established external frameworks in symplectic geometry (Floer theory, ∞-categories, prior orderability relations) without the central claim collapsing into its inputs. This is a standard non-circular technical development.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Existence of symplectic fillings and transversality for holomorphic curves in the equivariant setting.
- domain assumption The Eliashberg-Polterovich orderability relation on the universal cover of the contactomorphism group admits an infinity-categorification.
Reference graph
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