1) I am interested in many many things, and would not like to commit myself to a very specific research group.
2) I have never done any work that is closely related to anything that I see. Therefore, to comment wisely on a research group and why I would like to join it, will require A LOT of studying on my part. All I can do right now is say something silly that shows my lack of understanding, such as, "I am very interested in joining this group due to their research in 'X' which I find to be compelling and to align well with my research interests."
Do I have to be a *** expert in any field imaginable to write a decent SOP? Did anyone get accepted by plainly saying "I am interested in condensed matter theory and experiment," or something of that sort?
