Fluctuation dominated phase ordering in coarse-grained depth models: domain wall structures, extreme values and coarsening

Models of particles driven by a one-dimensional fluctuating surface are known to exhibit fluctuation dominated phase ordering (FDPO), in which both the order and fluctuations appear on macroscopic scales. Highly dynamic and macroscopically broad interfacial regions, each composed of many domain walls, appear between macroscopically ordered regions and consequently the scaled correlation function violates the Porod law. We focus on two essential quantities which together quantify the unique characteristics of FDPO, namely the total number of domain walls and the length of the largest ordered domain. We present results in the context of coarse-grained depth (CD) models, both in steady state and while coarsening. Analytic arguments supported by numerical simulations show that even though domain wall number fluctuations are very strong, the associated variance remains constant in time during coarsening. Further, the length of the largest cluster grows as a power law with significant multiplicative logarithms which involve both the time and system size. In addition, we identify corrections to the leading power law scaling in several quantities in the coarsening regime. We also study a generalisation of the CD model in which the domain wall density is controlled by a fugacity and show that it maps on to the truncated inverse distance squared Ising model. The generalised model shows a mixed order phase transition, with the regular CD model (which exhibits FDPO) corresponding to the critical point.

Automated summary

Models of particles driven by a one-dimensional fluctuating surface exhibit fluctuation dominated phase ordering (FDPO), with macroscopic order and fluctuations appearing on large scales. Interfacial regions between ordered regions contain many domain walls, violating the Porod law. The total number of domain walls and the length of the largest ordered domain quantify the unique characteristics of FDPO. The study focuses on coarse-grained depth (CD) models and shows that domain wall number fluctuations remain constant during coarsening, while the length of the largest cluster grows with time and system size following a power law with logarithmic terms.