The stream in which you would earn
your PhD degree is quite independent of my affiliation at Bose
Institute. As per University of Calcutta regulations, you can earn your PhD degree in the
stream of your choice which obviously includes the one in which you
completed your MSc. So, for example, if you have an
MSc in Applied Math or Physics, you may be awarded the PhD degree in Applied Math or Physics respectively,
upon successful completion of your research and on satisfying the
neccesary criteria of the University and the relevant Department.