Double.
Congrats on a very well written, surreal and thought provoking short script.
I know your self producing, so I won't rant about formatting issues I have, but I will briefly point out a few things for those who are looking to sell their scripts rather than self produce.
I would ever so briefly describe your characters when first intro'd. Ages, types, etc. I don't care if they are tall, short or have brown hair, but give me a feel for them and who they are.
Is Danniele O.S. in the first scene. If so, add it.
I wouldn't use (CONT'D) in Characters when the speak again. I would only use them for when a character's line bleeds onto the next page.
The same for Time of Day in your sluglines. Continuous, Moments later, and such are implied and not needed. Use only when a clear, definate shift in time happens.
You mention names of books but not that it is a book. You say she's taking notes, but on what? Paper, laptop? There are other times in the script where things are not as clear as they could be. Not many, but a few.
For your one paragraph scenes, I would break them up a bit for emphasis and directing the audience. It is an effective way of not only creating white space which makes it easier to read, but it is also a subtle way of implying a close up or actions that the audience should pay attention too. Be careful not to do it too much though, because it will look like padding if not done right. Just a thought.
I would speckle in Sid earlier but make it very subtle so the audience may not even notice it.
Structurally, it works well as well as your dialog, but I would consider moving up the scene with the professor in his office a little. It is the first scene that really drives home the questions Nolan faces. In many ways this one of the most important scene for me. It tells me what the movie is really about but a hit over the head. Great job on that one.
At the end I would have liked a slightly clearer sense of which was each scene film-- Dream or Reality. The end should be IMHO a reveal so that the audience can see where each shift was in the film, but not during the film while watching it. In other words, I would have liked if the lines between dreams and reality blended even more to the bizarre so that only at the end can the audience see where the true lines where.
I am put to mind stylistically and thematically to Donna Darko, Jacobs Ladder and even Carnival of Souls. which is all good. You may want to look at those films more to see how you can make the blending of reality and dream even more obscure and surreal.
Don't get me wrong, I think you have a top notch short here. My comments are meant more for little tweaks to make a great script even better...