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I just started physics research.

I am learning about stars. My research adviser told me that the potential should be positive for large r then goes to 0 at infinity so the stationary point at infinity is a minimum (then it is stable at empty space(infinity))

To be honest I've never encountered these potentials. I thought potentials are negative, and after the first stationary point ("equilibrium position", they are monotonically increasing to 0.

Anyone knows what is my research adviser is talking about?

Any help would be appreciated.

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  • $\begingroup$ What's this potential's behavior at small $r$? $\endgroup$
    – probably_someone
    Commented Jul 8, 2017 at 4:29
  • $\begingroup$ Have you tried asking your reseach adviser? He/she is the best person to know what he/she said. For us to try to interpret from your recollection what he/she meant is like a game of Chinese Whispers. ... It would be better if you told us what problem you are trying to solve, what you think, and why you doubt that your solution is correct. $\endgroup$
    – sammy gerbil
    Commented Jul 8, 2017 at 8:51

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First off, I assume that you are using the word "potential" to mean gravitational potential energy. The idea of "gravitational potential" is a viable concept as well, playing the same roll as voltage does in electrostatics. This trivia tidbit doesn't really affect the rest of this answer, however.

You are correct, gravitational potential energy is usually defined as negative, getting asymptotically closer to zero as you approach infinitely far away.

There are any number of reasons why you might define it the other way around, and change the direction that a force has to point in order to call it a positive force.

I realize that this is somewhat of a non-answer, but I thought that I would chime in to let you know that you are justified in your confusion.

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