Universality of the unfiltered crossover scaling curve

Determine whether the scaling curve for spatiotemporal coherence in one-dimensional photon condensate arrays with intermediary density fluctuations, obtained without spectral filtering, possesses a universal character.

Background

The paper studies Kardar–Parisi–Zhang (KPZ) scaling in one-dimensional arrays of photon condensates described by a stochastic classical-field model coupled to molecular rate equations. In the grand-canonical regime, where density fluctuations are large, the simulated spatiotemporal coherence collapses onto the universal KPZ scaling curve without filtering. In the crossover toward the canonical regime, however, the unfiltered scaling collapse deviates markedly from that universal curve, although filtering out high-energy modes restores a good KPZ collapse.

The authors explicitly leave unresolved whether the unfiltered crossover-regime scaling curve is itself universal rather than merely a nonuniversal consequence of the excited-state and finite-momentum contributions present in that regime.