Answer

I don’t think it is forbidden. The basic principle is that one should be dressed respectably, but that depends on your usual habits and on the place where you are studying. In a study hall, one certainly should not sit wearing a sleeveless undershirt. As for shorts—it depends on the local custom there.
Similarly, some have the practice of reciting blessings over food and Grace after Meals at the beach while wearing a bathing suit. Everything depends on the place and the reasonable local practice.