title: Critical phenomena in active matter.
abstract: We investigate the effect of self-propulsion on a mean-field order-disorder transition. Starting from a φ^{4} scalar field theory subject to an exponentially correlated noise, we exploit the unified colored-noise approximation to map the nonequilibrium active dynamics onto an effective equilibrium one. This allows us to follow the evolution of the second-order critical point as a function of the noise parameters: the correlation time τ and the noise strength D. Our results suggest that the universality class of the model remains unchanged. We also estimate the effect of Gaussian fluctuations on the mean-field approximation finding an Ornstein-Zernike-like expression for the static structure factor at long wavelengths. Finally, to assess the validity of our predictions, we compare the mean-field theoretical results with numerical simulations of active Lennard-Jones particles in two and three dimensions, finding good qualitative agreement at small τ values.
authors.affiliation: Department of Physics, Syracuse University, Syracuse, New York 13244, USA.
authors.forename: M
authors.initials: M
authors.lastname: Paoluzzi
authors.affiliation: NANOTEC-CNR, Institute of Nanotechnology, Soft and Living Matter Laboratory, Piazzale A. Moro 2, I-00185, Roma, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Maggi
authors.affiliation: Scuola di Scienze e Tecnologie, Università di Camerino, Via Madonna delle Carceri, 62032 Camerino, Italy and INFN, Sezione di Perugia, Via A. Pascoli, 06123 Perugia, Italy.
authors.forename: U
authors.initials: U
authors.lastname: Marini Bettolo Marconi
authors.affiliation: CNR, ISC, UOS Sapienza, Piazzale Aldo Moro 2, 00185 Roma, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Gnan