  A quark-antiquark effective model is studied in a toroidal topology at finite
temperature. The model is described by a Schr\"odinger equation with linear
potential which is embedded in a torus. The following aspects are analysed: (i)
the nonclassicality structure using the Wigner function formalism; (ii) finite
temperature and size-effects are studied by a generalization of Thermofield
Dynamics written in phase space; (iii) in order to include the spin of the
quark, Pauli-like Schr\"odinger equation is used; (iv) analysis of the
size-effect is considered to observe the fluctuation in the ground state. The
size effect goes to zero at zero, finite and high temperatures. The results
emphasize that the spin is a central aspect for this quark-antiquark effective
model.

High Energy Physics - Theory