Models with spins of definite lengths Sarma, Hilhorst

2 Models with spins of definite lengths (Sarma, Hilhorst). 

The ferromagnetic models proposed by Sarma4 and Hilhorst5 correspond to self-avoiding polymers drawn on a lattice. 

In both models, the weight1W has the following fundamental property. For a given r (i.e. for a given site), the mean value of any product of components ri, ( ) vanish in the limit n - 0, except the quantities 

We shall see later on how these conditions can be realized in practice. 

The Green s function G(r. r2H Aj ), defined by (11.3.4) as a mean value calculated with the weight W, 

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