For its third session (after 2005 and 2008), the ``FORUM de la THEORIE au CEA'' (The Theory Forum at CEA) is intended to give an overview of the theoretical activity and achievements in the CEA laboratories, putting forward their quality and diversity of approaches. \ par The talks will show the key progresses in a pedagogical form which should make them understandable by all the members of the CEA having interest in the recent scientific developments. They will concern different sectors of the CEA. If, naturally, the subjects chosen for the FORUM are focussed on theoretical physics, they will include domains having strong links with it, such as mathematics, biology, computing, nanosciences and others. The FORUM speakers will come from Institut de Physique Théorique and different sectors of activity in the CEA. \ par The FORUM will take place in the Claude Bloch Auditorium, on Wednesday the 3rd and Thursday the 4th of April 2013, in the CEA center situated in ``l'Orme des Merisiers'', Saclay. \ \ http://ipht.cea.fr/Meetings/ForumTheory2013/