Shadow–flux lower-bound conjecture for Lagrangian cobordisms

Let L0L_0 and L1L_1 be Lagrangian isotopic submanifolds, and let K:L1L0K: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):=infitI(L0,L1)BBcBFluxit(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 b1(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)>Ad(L0,L1)b1(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.

Sources & referencesView supporting material

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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