For fall entry, we start inviting students for a visit and interview in January. We start making offers in February and continue until our positions are filled, which is usually in April (we enter about 25 students each fall). To be considered for fellowships, all of your application materials should arrive by December 27th. Applications that are completed later might still be considered for admission, but will be ineligible for consideration for certain fellowships.
For spring entry, we consider domestic applicants till the end of November and foreign applicants till the end of September (it takes at least three months to process visas, etc.)
There are a variety of fellowships available for domestic students. The deadline for some of these is quite early (e.g., some are as early as Jan. 10th) and they are competitive across the College of Natural Science and the University. We will submit your application for these fellowships as soon as it is complete and provided it is sufficiently strong (e.g., 3.5 or better GPA from a strong school, 650 or better Physics GRE, strong letters indicating research potential). Applicants to the Physics/Astronomy program are typically offered about 7 of these fellowships each year.