Shadow–flux lower-bound conjecture for Lagrangian cobordisms

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Let L0L_0 and L1L_1 be Lagrangian isotopic submanifolds, and let K:L1⇝L0K:L_1\rightsquigarrow L_0 be a Lagrangian cobordism. Let d(L0,L1)d(L_0,L_1) denote the minimal flux distance, defined by

d(L0,L1):=inf⁡it∈I(L0,L1)B∈B∑c∈B∣Flux⁡it(c)∣,d(L_0,L_1):=\inf_{\substack{i_t\in\mathcal I(L_0,L_1)\\ B\in\mathcal B}}\sum_{c\in B}|\operatorname{Flux}_{i_t}(c)|,

where I(L0,L1)\mathcal I(L_0,L_1) is the set of Lagrangian homotopies between L0L_0 and L1L_1, B\mathcal B is the set of bases of H1(L,Z)H_1(L,\mathbb Z), and b‾1(K)\underline b_1(K) is the first Betti number of the cobordism. Shadow–flux lower-bound conjecture. There exists a constant AA such that, for every such pair and cobordism,

Area⁡(K)>A⋅d(L0,L1)b‾1(K).\operatorname{Area}(K)>\frac{A\cdot d(L_0,L_1)}{\underline b_1(K)}.

This conjecture proposes a quantitative trade-off between the shadow area and topological complexity of a Lagrangian cobordism. The surrounding discussion explains that cobordisms with smaller shadow can be constructed at the cost of increasing their first Betti number; whether the stated universal lower bound holds remains open.

References

Primary source

Jeff Hicks and Cheuk Yu Mak, “Some cute applications of Lagrangian cobordisms towards examples in quantitative symplectic geometry”, arXiv:2208.14498 (2026).

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