Hidden geometries in nonlinear theories: a novel aspect of analogue gravity

We show that non-linear dynamics of a scalar field {\phi} may be described as a mod- ification of the spacetime geometry. Thus, the self-interaction is interpreted as a coupling of the scalar field with an effective gravitational metric that is constructed with {\phi} itself. We prove that this process is universal, that is, it is valid for arbi- trary Lagrangian. Our results are compared to usual analogue models of gravitation, where the emergence of a metric appears as a consequence of linear perturbation.