AN INTRODUCTION TO YANGIAN SYMMETRIES

14 pages, SPTh-92-134, (The Tex has been corrected)International audienceWe review some aspects of the quantum Yangians as symmetry algebras of two-dimensional quantum field theories. The plan of these notes is the following: 1 — The classical Heisenberg model: •Non-Abelian symmetries; •The generators of the symmetries and the semi-classical Yangians; •An alternative presentation of the semi-classical Yangians; (Digression on Poisson-Lie groups. 2 — The quantum Heisenberg chain: •Non-Abelian symmetries and the quantum Yangians; •The transfer matrix and an alternative presentation of the Yangians