I think that you should still go for it. When presenting your thesis or a presentation, you can say, "Before I start, I'd like to say that I'm a stutterer so if you see me having trouble saying a word, it's because of that. However, it will not affect my credibility as a candidate for a doctorate in physics." Something like that. The hope is that by telling these people, you'll feel less pressure that you can't stutter and the hope is that since you will feel more relaxed, you will be more fluent. And when you give your speech, the people evaluating you will see that the stutter doesn't effect your credibility as a candidate at all. Another thing you can do is you can get a couple friends, have them comeover, and practice performing in front of them. It'll get you more comfortable speaking in front of others and also, you can just imagine you're at home giving your presentation to your friends when you do the actual thing. If you want anymore tips, let me know and I'll be glad to give you more