On a special class of simplicial toric varieties

We show that for all n 3 and all primes p there are infinitely many simplicial toric varieties of codimension n in the 2n-dimensional affine space whose minimum number of defining equations is equal to n in characteristic p, and lies between 2n−2 and 2n in all other characteristics. In particular, these are new examples of varieties which are set-theoretic complete intersections only in one positive characteristic. Moreover, we show that the minimum number of binomial equations which define these varieties in all characteristics is 4 for n=3 and whenever n 4.