Department of Mathematics, Hokkaido University,

Sapporo 060-0810, JAPAN

E-mail: arai@math.sci.hokudai.ac.jp

**Enhanced binding in quantum field models**

**Abstract:**

We consider a general model of an arbitrary quantum system coupled to a multi-component Bose field with a coupling parameter g, where it is not assumed that the system with g = 0 (the unperturbed system) has a ground state. We say that the enhanced binding occurs or exists in the model if the coupled system (the system with g ¹ 0) has a ground state for a range of g. We formulate conditions under which the enhanced binding occurs.

**References:**

- A. Arai, Enhanced binding in models of nonrelativistic quantum field theory, in ``Garden of Quanta'' (Edited by J. Arafune, A. Arai et al), World Scientific, to appear in 2003.
- A. Arai and H. Kawano, Enhanced binding in a general class of quantum field models, ESI preprint series 1251, 2002 or mp_arc 02-508, 2002, to be published in Rev. Math. Phys.