Borsari I, Graffi S., Unguendoli M.
Ground states for a class of deterministic spin models with glassy behaviour
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ABSTRACT.  We consider the deterministic model with glassy behaviour, recently introduced by
Marinari, Parisi and Ritort, with \ha\ $H=\sum_{i,j=1}^N J_{i,j}\sigma_i\sigma_j$, where
$J$ is the discrete sine Fourier transform. The ground state found by these authors for
$N$ odd and $2N+1$ prime is shown to become asymptotically dege\-ne\-ra\-te when $2N+1$
is a product of odd primes, and to disappear for $N$ even. This last result is based on
the explicit construction of a set of eigenvectors for $J$, obtained through its formal
identity with the imaginary part of the propagator of the quantized unit symplectic
matrix over the $2$-torus.