In the reaction between chlorine and HBr transformation of HBr into Br_2 takes place. Can this transformation be called oxidation? Which is the oxidant that brings about this oxidation?

Explanation

Yes, this transformation can be called oxidation. In the reaction between HBr and chlorine `(Cl_2)`, HBr is oxidized to `Br_2` and `Cl_2` is reduced to HCl. Hence `Cl_2` is the oxidant in the reaction.
`underset"Hydrogen bromide"(HBr) + underset"Chlorine"(Cl_2) to underset"Bromine"(Br_2) + underset"Hydrogen chloride"(HCl)`