General-term conjecture for the short-time expansion of the KPZ generating function

Let gg be the function used to define Qt,β(σ)Q_{t,\beta}(\sigma), let Li\mathfrak{L}_i denote the corresponding coefficients, and let n=(n1,,nr+22q)\mathbf{n}=(n_1,\ldots,n_{r+2-2q}). If the distinct values among the njn_j have multiplicities m1,,mkm_1,\ldots,m_k, define the symmetry factor S(n)=m1!mk!S(\mathbf{n})=m_1!\cdots m_k!. For σ<1\sigma<1, the general-term conjecture. The short-time expansion of logQt,β(σ)\log Q_{t,\beta}(\sigma) has the form

logQt,β(σ)=1πt0+dxxg(σex)+14π20σduu[u+dpg(uep2)]2+r=1+q=0r2+12r+13q(2q+1)!tr/2r+2n1nr+22q0 1++nr+22q=r1+qcr,q(n)S(n)j=1r+22qLnj+1nj!.\begin{aligned} \log Q_{t,\beta}(\sigma)={}&\frac{1}{\pi \sqrt{t}}\int_{0}^{+\infty}\mathrm{d}x\sqrt{x}\,g(\sigma e^{-x})+\frac{1}{4\pi^2}\int_0^\sigma\mathrm{d}u\,u\left[\partial_u\int_{-\infty}^{+\infty}\mathrm{d}p\,g(u e^{-p^2})\right]^2\\\\ &+\sum_{r=1}^{+\infty}\sum_{q=0}^{\frac{r}{2}+1}\frac{2^{r+1-3q}}{(2q+1)!}t^{r/2}\sum_{\substack{r+2\geq n_1\geq\ldots\geq n_{r+2-2q}\geq0\\\ _1+\ldots+n_{r+2-2q}=r-1+q}}\frac{c_{r,q}(\mathbf{n})}{S(\mathbf{n})}\prod_{j=1}^{r+2-2q}\frac{\mathfrak{L}_{n_j+1}}{n_j!}. \end{aligned}

Here the coefficients cr,q(n)c_{r,q}(\mathbf{n}) are positive integers. The conjecture is motivated by the explicitly computed expansion through order t3t^3, but precise analytical expressions for arbitrary high orders were not obtained, so the general form remains open.

Sources & referencesView supporting material

Primary source

Alexandre Krajenbrink, Pierre Le Doussal and Sylvain Prolhac, “Systematic time expansion for the Kardar-Parisi-Zhang equation, linear statistics of the GUE at the edge and trapped fermions”, arXiv:1808.07710 (2018).

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