Is a Caspian tiger a white tiger?

No,the Caspian tiger was an extinct subspecie of tigers that was almost in the Same size and Looks like the modern Siberian tiger,white tigers are a color morph Of any Subspecies of tigers(the Siberian tigers don't have this problem only if a Bengal tiger with a color morph and a Siberian will mate,so generally only a Bengal Tigers seem to have this mutant).

A white tiger's pale coloration is caused by the presence of a recessive gene (the Same thing that causing a dominant allele for the jaguars and recessive allele for The leopards to have black fur)