https://hal-cea.archives-ouvertes.fr/cea-01531897v2Gelis, FrançoisFrançoisGelisIPHT - Institut de Physique Théorique - UMR CNRS 3681 - CEA - Commissariat à l'énergie atomique et aux énergies alternatives - Université Paris-Saclay - CNRS - Centre National de la Recherche ScientifiqueTree-level correlations in the strong field regimeHAL CCSD2017[PHYS] Physics [physics]De Laborderie, Emmanuelle2017-06-02 10:06:312022-04-01 10:00:092017-06-06 09:31:52enPreprints, Working Papers, ...https://hal-cea.archives-ouvertes.fr/cea-01531897v1text/html; charset=utf-82We consider the correlation function of an arbitrary number of local observables in quantum field theory. We show that, at tree level in the strong field regime, these correlations arise solely from fluctuations in the initial state. We obtain the general expression of these correlation functions in terms of the classical solution of the field equation of motion and its derivatives with respect to its initial conditions, that can be arranged graphically as the sum of labeled trees where the nodes are the individual observables, and the links are pairs of derivatives acting on them. For 3-point (and higher) correlation functions, there are additional tree-level terms beyond from the strong field approximation, generated throughout the evolution of the system.