How can I protect my unpublished work that I've sent to others? I am a masters student from India applying for a PhD in the US. 

I emailed a potential adviser at Harvard University an unpublished paper I have been working on for some time.

The application in the end did not work out but the adviser was enthusiastic about the paper and said I wasn't admitted due to funding issues.

Now I am a bit worried he may publish part of my work without mentioning me, since the paper is not published.

How likely is this? What actions I can take to protect my work?
How likely is this? Have you ever heard a Professor of this caliber doing something like that?


This depends on the field -- in some fields people are more worried about being "scooped". It could be anywhere from "unlikely but possible" to "extremely unlikely". Overall it is not a serious concern that you should worry about, but it is a remote possibility that you could consider taking steps to prevent.

In response to some comments, let me add that blatant plagiarism (where they publish your writing as it is) is much less likely because that is academic misconduct that could get a professor in real trouble when you present the proof.

On the other hand, scooping is where you get the idea from the paper, and do it yourself. It is still academic misconduct, but more difficult to prove and it may go unpunished.


  What actions I can take to protect my work, assuming I need about 6
  months to have it ready for publication?


The best solution is to publish the draft online. This is common in many fields and becoming common in others. If you publish online, everyone will see that this is your work and you did it first; you have documented proof on the internet.

It could also help to document it in other ways: send the draft to others, and put together some proof that you wrote it, just in case.