I am starting a PHD in Europe at a top institution very soon. In the time since I have accepted the offer I have developed the feeling that I am more interested in working with a different supervisor on a different research area. They are both in the same subfield, but the nature of the research is very different. I would like to enquire if it is possible to switch. If that is not possible I am very happy to continue as is. I am very anxious about making this enquiry. I would be very grateful for any advice.