  The infinite U Hubbard model, with exclusion of double occupancy of sites,
can be considered as a free orthofermion Hamiltonian which is exactly soluble.
It is found that the orthofermion distribution function is similar to the mean
number of trapped electrons in an impurity in a semiconductor where the double
occupancy of the impurity is forbidden and similar to the distribution function
of the usual fermions. In one dimension, the thermodynamics of free
orthofermions gives the known exact results of the infinite U Hubbard model.
Thus it shows that at least in one dimension the fermions with exclusion of
double occupancy of sites behave as free orthofermions. Since free
orthofermions Hamiltonian is exactly soluble in any dimension, it can be
employed to ascertain the accuracy of the approximate solutions of the Hubbard
model, frequently used for the strongly correlated electron systems like high
temperature superconductors.
