Reduced density fluctuations via antialigning in active matter

We highlight the importance of long-range correlations in active matter systems of self-propelling particles even in the absence of global order or steric interactions by demonstrating that long-range density fluctuations are reduced. We show this analytically for a one-dimensional lattice process employing a Poisson representation. Within this framework, we are able to derive the fluctuating hydrodynamics for the Poisson fields. The emergent imaginary noise indicates the non-Poissonian nature of the number fluctuations and manifests in a nontrivial structure factor S(k), which we are computing analytically. Numerically, we corroborate the relevance of these findings for off-lattice Vicsek-type models with antialigning interactions for which we observe apparent nonuniversal hyperuniformity, which we suggest to interpret as a reduction with integer power law to a finite value.