Contacting potential advisers before deadlines I am applying to PhD programs in physics in US. Majority of the deadlines are in one week from now. My question is, does that help at all at this time to contact potential advisers and let them know that I am applying and am interested in their research? (At least one place requires me to indicate potential advisers in the online application form). 

If contacting can help my application at this point, what should I do if there are more than one potential advisers whose interests match my experience and interests in a given department? (For example in one case I am even asked for naming three potential advisers in the application form)
It is definitely helpful to contact potential advisers for many reasons.  In my experience, one important reason is that a professor for whom you would like to work may not have space or funding for you.  Sometimes those things can be overcome, and sometimes they can't.  If there is only one professor whose research interests you in a given department, and that professor isn't taking students for some reason, that could make your decision for you.  It's not a pleasant situation, but I have seen it happen several times.

You might also find that, after talking to a potential adviser, the focus in their research isn't quite what you thought it was.  Of course you can find that out by reading the recent publications, but a conversation can also be enlightening.  They might tell you about one or two specific projects you would likely be working on, and if those projects don't interest you, you might want to move on.

If things look like they could work out, it is still an excellent idea to stay in touch.  If someone on the admissions committee gets to know you somehow, that will really set your application apart.  The chair of the graduate admissions committee at my undergraduate institution even told me that, more than once, he has admitted a student simply because he or she was calling or emailing and expressing real interest and desire to become a student in the department.  Don't be annoying, but a couple of emails and/or a phone call or two never hurt anyone.

If there are several potential advisers in one department, that is great.  It likely means that department focuses on research that interests you.  Don't be afraid of getting in touch with more than one professor.  The more people that recognize your name, the better.  Just be sure to be polite and respectful and leave a good impression.

Good luck!