Résumé
As humans, we interact both visually and sterically when densely surrounded by a crowd. While our steric interactions might be reciprocal, our visual perceptions are not, as they strongly depend on the orientation of our eyes. Inspired by this, we consider a minimal model where the sole effect of visual perception is to modulate the steric potential of particles. Because self-propulsion is absent, this creates backward-moving particles, as they feel more repelled by frontal neighbors than by those behind them. We further simplify by fixing the particle orientations, initially uniformly sampled, and we ignore thermal fluctuations, meaning the particle dynamics is fully deterministic. Despite the simplicity of the model, the emerging collective phenomena at high densities are rich, ranging from crowd-defeating independent backward gliders (at high non-reciprocity) to chaotic collective motion (at intermediate non-reciprocity) that finally terminates in an absorbing phase transition (at small non-reciprocity).