Antolín, Martino and Ventura's meta-conjecture on degree of commutativity

Let GG be a group, and let M=(μn)n=1M=(\mu_n)_{n=1}^\infty be a sequence of probability measures on GG. For a probability measure μ\mu on GG, define

dcμ(G)=(μ×μ)({(x,y)G×G:xy=yx}),\operatorname{dc}_\mu(G)=(\mu\times\mu)(\{(x,y)\in G\times G:xy=yx\}),

and define

dcM(G)=lim supndcμn(G).\operatorname{dc}_M(G)=\limsup_{n\to\infty}\operatorname{dc}_{\mu_n}(G).

Antolín, Martino and Ventura's meta-conjecture. For any “reasonable” sequence M=(μn)n=1M=(\mu_n)_{n=1}^\infty of probability measures on GG, we have dcM(G)>0\operatorname{dc}_M(G)>0 if and only if GG is virtually abelian.

This conjecture proposes a natural infinite-group analogue of the positive degree-of-commutativity result for finite groups. Its formulation depends on the meaning of “reasonable” for the sequence of measures; the source presents it as a meta-conjecture, and no resolution is supplied here.

Sources & referencesView supporting material

Primary source

Matthew Tointon, “Commuting probabilities of infinite groups”, arXiv:1707.05565 (2020).

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