Circular Kardar-Parisi-Zhang interfaces evolving out of the plane

Abstract

Circular KPZ interfaces spreading radially in the plane have GUE Tracy-Widom (TW) height distribution (HD) and Airy$_2$ spatial covariance, but what are their statistics if they evolve on the surface of a different background space, such as a bowl, a cup, or any surface of revolution? To give an answer to this, we report here extensive numerical analyses of several one-dimensional KPZ models on substrates whose size enlarges as $\langle L(t) \rangle = L_0+ωt^γ$, while their mean height $\langle h \rangle$ increases as usual [$\langle h \rangle\sim t$]. We show that the competition between the $L$ enlargement and the correlation length ($ξ\simeq c t^{1/z}$) plays a key role in the asymptotic statistics of the interfaces. While systems with $γ>1/z$ have HDs given by GUE and the interface width increasing as $w \sim t^β$, for $γ<1/z$ the HDs are Gaussian, in a correlated regime where $w \sim t^{αγ}$. For the special case $γ=1/z$, a continuous class of distributions exists, which interpolate between Gaussian (for small $ω/c$) and GUE (for $ω/c \gg 1$). Interestingly, the HD seems to agree with the Gaussian symplectic ensemble (GSE) TW distribution for $ω/c \approx 10$. Despite the GUE HDs for $γ>1/z$, the spatial covariances present a strong dependence on the parameters $ω$ and $γ$, agreeing with Airy$_2$ only for $ω\gg 1$, for a given $γ$, or when $γ=1$, for a fixed $ω$. These results considerably generalize our knowledge on the 1D KPZ systems, unveiling the importance of the background space in their statistics.