Limiting root-measure conjecture for random positive 3-braids

From papers

Let Br3\mathrm{Br}_3 be the 3-strand braid group, let Ω={σ1,σ2}N\Omega=\{\sigma_1,\sigma_2\}^{\mathbb{N}} with the product measure assigning probability 1/21/2 to each generator, and set wn=g1gnw_n=g_1\cdots g_n. For a braid ww, let ZwZ_w be the multiset of zeros of the Alexander polynomial of its closure and let

νw=1#ZwzZwδz.\nu_w=\frac{1}{\# Z_w}\sum_{z\in Z_w}\delta_z.

Limiting root-measure conjecture. There is a compactly supported measure ν\nu_\infty on C\mathbb{C} such that, for almost every sequence (gi)iNΩ(g_i)_{i\in\mathbb{N}}\in\Omega, νwn\nu_{w_n} converges weakly to ν\nu_\infty. Its support is contained in the union of the unit circle, a continuous curve from ζ3\zeta_3 to ζ3\overline{\zeta}_3, and the image of that curve under z1/zz\mapsto1/z; the curve crosses the real axis at about 0.78-0.78. Writing

AL={eiθ:θπ<π/3},AR={eiθ:θ<2π/3},\mathcal A_L=\{e^{i\theta}:|\theta-\pi|<\pi/3\},\qquad \mathcal A_R=\{e^{i\theta}:|\theta|<2\pi/3\},

exactly 2/32/3 of the mass lies on AR\mathcal A_R, where the measure is a multiple of Lebesgue measure; its mass on AL\mathcal A_L is (735)/120.024316(7-3\sqrt5)/12\approx0.024316, so the total mass on the unit circle is (55)/40.690983(5-\sqrt5)/4\approx0.690983. The measures along the curves joining ζ3\zeta_3 to ζ3\overline{\zeta}_3 are absolutely continuous with respect to Lebesgue measure. These predictions refine the experimentally observed concentration and equidistribution of roots; the convergence and the detailed support and density assertions remain conjectural.

Progress summary

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

Sources & referencesView supporting material

Primary source

Nathan M. Dunfield and Giulio Tiozzo, “Roots of Alexander polynomials of random positive 3-braids”, arXiv:2402.06771 (2025).

Solutions 0

No solutions have been posted yet.