OpenAI reports a reflexive midpoint-convexity counterexample

A separable reflexive real Banach space has an asymptotically midpoint uniformly convex given norm with averaged midpoint modulus at least √(1+t²/12)−1 for t>0, but admits no equivalent asymptotically uniformly convex norm; depth-k countably branching diamonds have distortion at least √(1+k/12) in it.

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OpenAI reports a reflexive midpoint-convexity counterexample

  • Mathematics

A separable reflexive real Banach space has an asymptotically midpoint uniformly convex given norm with averaged midpoint modulus at least √(1+t²/12)−1 for t>0, but admits no equivalent asymptotically uniformly convex norm; depth-k countably branching diamonds have distortion at least √(1+k/12) in it.

AI involvementAI-led
ImportanceNotable
Technical verificationFormal (Lean 4)
Human understandingFew

Understanding the problem

Read the background

A separable reflexive real Banach space has an asymptotically midpoint uniformly convex given norm with averaged midpoint modulus at least √(1+t²/12)−1 for t>0, but admits no equivalent asymptotically uniformly convex norm; depth-k countably branching diamonds have distortion at least √(1+k/12) in it.

Why it matters

If correct, strengthens the earlier negative result to a quantitative reflexive example and separates the corresponding metric diamond criterion.

What counts as progress

Can a reflexive midpoint-convex Banach space resist every asymptotically uniformly convex renorming?

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