The random matrix strong convergence conjecture for tensor actions

From papers

Let rNr\in\mathbb{N}, let αC[Fr]C[Fr]\alpha\in\mathbb{C}[\mathbb{F}_r]\otimes\mathbb{C}[\mathbb{F}_r], and let uu be an rr-tuple of free Haar unitaries. For almost every sequence of Haar-random tuples U(N)U(MN(C)r)U^{(N)}\in\mathcal{U}(\mathbb{M}_N(\mathbb{C})^r), define (BC)#A=BACT(B\otimes C)\# A=BAC^T. The random matrix strong convergence conjecture. One has

supR>0infFC[Fr] finitelim supNsupAMN(C), AR, A21,PF, tr(AP(UN))=0α(U(N)1N,1N(U(N))t)#A2α(u1,1u1)Cλ(Fr)minCλ(Fr).\sup_{R>0}\inf_{F\subset\mathbb{C}[\mathbb{F}_r]\ \mathrm{finite}}\limsup_{N\to\infty}\sup_{\substack{A\in\mathbb{M}_N(\mathbb{C}),\ \|A\|\leq R,\ \|A\|_2\leq1,\forall P\in F,\ \operatorname{tr}(A^*P(U^N))=0}}\left\|\alpha(U^{(N)}\otimes1_N,1_N\otimes(U^{(N)})^t)\# A\right\|_2 \leq\left\|\alpha(u\otimes1,1\otimes u^{-1})\right\|_{C^*_{\lambda}(\mathbb{F}_r)\otimes_{\min}C^*_{\lambda}(\mathbb{F}_r)}.

The estimate asserts that, after removing finitely many polynomial directions, the random tensor action has the expected limiting norm. The source states that this conjecture has since been resolved by several authors, so its status is solved.

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Sources & referencesView supporting material

Primary source

Ben Hayes, David Jekel and Srivatsav Kunnawalkam Elayavalli, “Questions on the structure of random embeddings of L(F_2)”, arXiv:2606.02985 (2026).

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