REVIEW 2 minor 52 references
An isomorphism equates the Z_d-equivariant Rabinowitz Floer homology of a Legendrian lift to the quantum homology of its Lagrangian base.
Reviewed by Pith at T0; open to challenge. T0 means a machine referee read the full paper against a public rubric. the ladder, T0–T4 →
T0 review · grok-4.3
2026-07-01 02:06 UTC pith:HCSUSAGO
load-bearing objection The paper defines Rabinowitz Floer homology for Legendrian lifts in prequantization bundles and proves an isomorphism to the quantum homology of the base Lagrangian, with explicit ring computations as the main payoff.
Rabinowitz Floer homology for Legendrian submanifolds in prequantization bundles
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Under the assumption that the minimal Maslov number N_L exceeds 2, the Z_d-equivariant Rabinowitz Floer homology of the Legendrian lift L is isomorphic to the quantum homology of the base Lagrangian L; when N_L is larger still, the isomorphism preserves the ring structures. The construction relies on the prequantization bundle structure and the monotonicity of L to set up the chain complexes and the covering action.
What carries the argument
The Z_d-equivariant Rabinowitz Floer homology of the Legendrian lift, built from the action functional on the covering space and filtered by the covering degree d.
Load-bearing premise
The minimal Maslov number of the Lagrangian must exceed 2 (plus monotonicity) both to define the Rabinowitz Floer homology and to obtain the isomorphism.
What would settle it
An explicit computation, for any single monotone Lagrangian sphere in a quadric with N_L greater than 2, showing that the rank or ring structure of its Z_d-equivariant Rabinowitz Floer homology differs from the known quantum homology of the sphere.
If this is right
- The quantum homology ring of Lagrangian spheres in quadrics is computed explicitly via the isomorphism.
- The quantum homology ring of Lagrangian spheres in two-step flag manifolds is computed explicitly via the isomorphism.
- Quantum invertibility of the symplectic form implies vanishing of the quantum homology of L.
- The isomorphism yields obstructions to the existence of topologically simple fillings of the Legendrian L.
- When the base admits a polarization and L is disjoint from the Lagrangian trace, the quantum homology of L vanishes.
Where Pith is reading between the lines
- The same isomorphism technique might extend to other contact manifolds that are not necessarily prequantization bundles, provided an analogous covering action can be defined.
- Computations of quantum homology via this route could be checked against independent algebraic geometry methods for additional classes of monotone Lagrangians.
- Vanishing results might translate into new constraints on the existence of Lagrangian fillings in higher-dimensional contact manifolds.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper defines Rabinowitz Floer homology for a Legendrian lift ℒ of a closed monotone Lagrangian L in a prequantization bundle Y o (Σ,ω), assuming minimal Maslov number N_L > 2. It establishes an isomorphism between the ℤ_d-equivariant Rabinowitz Floer homology of ℒ and the quantum homology of L (with d the degree of the covering ℒ o L), which is a ring isomorphism under a stricter condition on N_L. The isomorphism is applied to compute the quantum homology ring of Lagrangian spheres in quadrics and two-step flag manifolds, and to obtain vanishing results for quantum homology when (Σ,ω) admits a polarization and L is disjoint from the Lagrangian trace, together with implications for fillings of ℒ.
Significance. If the isomorphism holds, the work supplies a concrete bridge between Rabinowitz Floer homology in the contact setting and quantum homology, permitting explicit computations in both directions and yielding vanishing theorems and filling obstructions as direct consequences. The applications to quadrics and flag manifolds constitute verifiable output that strengthens the result.
minor comments (2)
- [Abstract] Abstract: the phrase 'under a more restrictive condition on N_L' is left unspecified; stating the precise numerical threshold would improve immediate readability without altering the theorem statements.
- The manuscript would benefit from an explicit comparison table or diagram relating the chain complexes, differentials, and operations used in the Rabinowitz Floer side versus the quantum homology side, to make the isomorphism construction more transparent at a glance.
Simulated Author's Rebuttal
We thank the referee for their positive summary, significance assessment, and recommendation of minor revision. No major comments were provided in the report.
Circularity Check
No significant circularity
full rationale
The paper defines Rabinowitz Floer homology of the Legendrian lift under the explicit standing hypotheses of monotonicity and N_L > 2 (standard to control disk bubbling), then constructs an isomorphism to the independently studied quantum homology of the base Lagrangian L. No central step reduces by construction to a fitted parameter, self-citation chain, or renamed input; the isomorphism and its ring version under stricter N_L are presented as new results whose consequences (computations on quadrics, vanishing theorems) are derived afterward. The derivation chain is self-contained against external benchmarks in symplectic geometry.
Axiom & Free-Parameter Ledger
axioms (2)
- standard math Standard properties of Floer homology and quantum homology hold in this setting.
- domain assumption L is closed monotone Lagrangian with N_L > 2.
read the original abstract
Let $Y$ be a prequantization bundle over an integral symplectic manifold $(\Sigma,\omega)$. Let $L$ be a closed monotone Lagrangian submanifold that admits a Legendrian lift $\mathcal{L}$ in $Y$. Under the assumption that the minimal Maslov number $N_L$ of $L$ is greater than 2, we define the Rabinowitz Floer homology of $\mathcal{L}$. We then establish an isomorphism between the $\mathbb{Z}_d$-equivariant Rabinowitz Floer homology of $\mathcal{L}$ and the quantum homology of $L$, where $d$ is the degree of the covering map $\mathcal{L}\to L$. Under a more restrictive condition on $N_L$, we show that this map is a ring isomorphism. Using this isomorphism, we compute the quantum homology ring of Lagrangian spheres in quadrics and two-step flag manifolds. Furthermore, we investigate the implications of the quantum invertibility of $\omega$ for the vanishing of the quantum homology of $L$ and the obstructions to topologically simple fillings of $\mathcal{L}$. We also show that if $(\Sigma,\omega)$ admits a polarization and $L$ is disjoint from the Lagrangian trace, the quantum homology of $L$ vanishes.
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discussion (0)
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