Structure conjecture for small quotient sets in groups

Let AA be a finite subset of a group GG, and let nn be a positive integer. Write N(H)N(H) for the normalizer of a subgroup HH in GG. A subset A0A_0 is contained in a single left N(H)N(H)-coset if there is some ginGgin G such that A0gN(H)A_0\subseteq gN(H).

Structure conjecture. If

A1A<(21n+1)A,|A^{-1}A|<\left(2-\frac{1}{n+1}\right)|A|,

then there are a finite subgroup HGH\le G and a subset A0AA_0\subseteq A of size A0n|A_0|\le n contained in a single left N(H)N(H)-coset such that

AA0H,A0H=A0H,A\subseteq A_0H,\qquad |A_0H|=|A_0||H|,

and

A>(21n+1)1(2A01)H.|A|>\left(2-\frac{1}{n+1}\right)^{-1}(2|A_0|-1)|H|.

Moreover,

A1A=A01A0HA^{-1}A=A_0^{-1}A_0H

and

A1A=(2A01)H.|A^{-1}A|=(2|A_0|-1)|H|.

This conjecture proposes a structural description of finite subsets with quotient set smaller than the stated threshold. The supplied text gives no resolution status or further evidence beyond presenting it as a conjecture, so its status remains open.

Sources & referencesView supporting material

Primary source

Vsevolod F. Lev, “Quotient sets in nonabelian groups”, arXiv:2404.06887 (2024).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.