The DMPK limiting-density conjecture for ballistic initial conditions

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Let n→∞n\to\infty with fixed M\mathbb{M}. Let ρ~(λ~;M)\tilde{\rho}(\tilde{\lambda};\mathbb{M}) be the limiting empirical probability density of the solution of the DMPK equation with ballistic initial condition, and set λ~=sinh⁡2x\tilde{\lambda}=\sinh^2 x. Define the resulting density by

ρ(x;M)=sinh⁡(2x)ρ~(sinh⁡2x;M).\rho(x;\mathbb{M})=\sinh(2x)\tilde{\rho}(\sinh^2x;\mathbb{M}).

DMPK limiting-density conjecture. The density ρ(x;M)\rho(x;\mathbb{M}) is related to ψ(x)\psi(x) by

ρ(x;M)=2xψ(x2),\rho(x;\mathbb{M})=2x\psi(x^2),

where ψ(x)\psi(x) is the function given by the paper's equation defining ψ\psi in the linear-potential case, with V(x)=x/MV(x)=x/\mathbb{M}.

The claim is motivated by identifying the transform U(ζ;M)=ζG~(ζ2)=I2(ζ2)U(\zeta;\mathbb{M})=\zeta\tilde{G}(\zeta^2)=\sqrt{\mathbf{I}_2(\zeta^2)} with the solution of the functional equation derived from the DMPK evolution. The assumption that the limiting empirical density exists and equals ρ~\tilde{\rho} is explicitly described as physically convincing but mathematically unproved, so the asserted relation remains open.

References

Primary source

Dong Wang and Dong Yao, “Biorthogonal polynomials related to quantum transport theory of disordered wires”, arXiv:2307.03720 (2025).

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