Weak isomorphic reverse isoperimetry conjecture

Let K⊆RmK\subseteq\mathbb R^m be an origin-symmetric convex body, meaning that x∈Kx\in K if and only if −x∈K-x\in K. Let SLm(R)\mathsf{SL}_m(\mathbb R) denote the group of volume-preserving linear transformations, and let iq(L)\mathrm{iq}(L) denote the isoperimetric quotient of a convex body LL. Weak isomorphic reverse isoperimetry conjecture. There exist S∈SLm(R)S\in\mathsf{SL}_m(\mathbb R) and an origin-symmetric convex body L⊆SKL\subseteq SK such that

volm(L)1/m≳volm(BX)1/myetiq(L)≲m.\mathrm{vol}_m(L)^{1/m}\gtrsim \mathrm{vol}_m(B_\mathsf{X})^{1/m}\qquad\mathrm{yet}\qquad \mathrm{iq}(L)\lesssim\sqrt m.

Here BXB_\mathsf{X} is the unit ball of the unitarily invariant normed space under consideration. The conjecture asserts that, after a volume-preserving linear position, every origin-symmetric convex body contains a comparably large body whose isoperimetric quotient is within a universal factor of the Euclidean optimum. The paper establishes the corresponding statement for unit balls of unitarily invariant matrix norms.

References

Primary source

Mustafa Alper Gunes and Assaf Naor, “The separation modulus of unitarily invariant matrix norms”, arXiv:2508.03853 (2025).

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