The general Maxwellian long-time asymptotics conjecture for collision-dominated homoenergetic flows

Let BB be a collision cross-section satisfying condition, and let γ\gamma denote its homogeneity. Let Q(t)Q(t) and L0L_0 be the matrix-valued quantities appearing in the homoenergetic Boltzmann equation, let μ(t)\mu(t) be its time-dependent coefficient, and let β(t)\beta(t) be the temperature scale. Let L\mathbb{L} be the linearized collision operator on the weighted space L2(R3;eξ2dξ)L^2(\mathbb{R}^3;e^{-\lvert\xi\rvert^2}d\xi). General Maxwellian asymptotics conjecture. Under suitable assumptions on γ\gamma and μ(t)\mu(t), there exists a weak solution gg in the stated measure-valued solution class and a function β(t)\beta(t) such that

β(t)32g(t,ξβ(t))π32eξ2\beta(t)^{-\frac32}g\left(t,\frac{\xi}{\sqrt{\beta(t)}}\right)\longrightarrow \pi^{-\frac32}e^{-\lvert\xi\rvert^2}

in L2(R3;eξ2dξ)L^2(\mathbb{R}^3;e^{-\lvert\xi\rvert^2}d\xi) as tt\to\infty. In case 1, if Q(t)=L0+O(t1δ)Q(t)=L_0+O(t^{-1-\delta}), δ>0\delta>0, Tr(L0)0\operatorname{Tr}(L_0)\ne0, a=23Tr(L0)a=\frac23\operatorname{Tr}(L_0), and μ(t)eγat/2t1+δ\mu(t)e^{-\gamma at/2}\gg t^{1+\delta}, then β(t)=Ceat(1+o(1))\beta(t)=Ce^{at}(1+o(1)). In case 2, if γ>0\gamma>0, Tr(Q(t))=0\operatorname{Tr}(Q(t))=0, Q(t)=L0+o(1)Q(t)=L_0+o(1) with L00L_0\ne0, λ(t)=0tds/μ(s)\lambda(t)=\int_0^t ds/\mu(s)\to\infty, λ(t)/λ(t)0\lambda'(t)/\lambda(t)\to0, and b=ξL0ξ,(L)1[ξL0ξ]w>0b=\langle \xi\cdot L_0\xi,(-\mathbb{L})^{-1}[\xi\cdot L_0\xi]\rangle_w>0, then β(t)=((4/3)γbλ(t))2/γ(1+o(1))\beta(t)=((4/3)\gamma b\lambda(t))^{-2/\gamma}(1+o(1)). These asymptotic existence and Maxwellian claims are proposed as the main general collision-dominated result; the paper supplies heuristic support through the Hilbert-expansion strategy, but no proof or resolution is given.

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Primary source

Richard D. James, Alessia Nota and Juan J. L. Velázquez, “Long time asymptotics for homoenergetic solutions of the Boltzmann equation. Collision-dominated case”, arXiv:1808.06941 (2018).

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