What’s an imperfect nash equilibrium?
A search of google with that phrase turns up nothing useful–only documents that use the term without explaining it.
From here. Now with 50% more explanations and examples!
Thanks for the quick reply and the definition for the nash equilibrium, but what I’m looking for is imperfect nash equilibrium. Apparently, there’s a difference between an imperfect one its regular counterpart. 
An imperfect nash equilibrium is one that is reached as a result of at least one player using an incredible strategy. ie a strategy that the other player(s) should not believe.
Give me a minute and I’ll come up with an example for you (off the top of my head the one that I can think of is mutually assured destruction in nuclear war - both sides don’t really believe that the other will push to the point of total worldwide destruction but do believe that there could be other outcomes that are suboptimal so the result of the game is not to initiate a nuclear war - you get the same outcome even though the strategies are false).
Hmmm…
In your example of mutual assured destruction, I assume that the scenario in which both countries launch nukes is suboptimal and stable (nash equilibrium), while the scenario in which neither country launches nukes is optimal and unstable. Are you saying that in the case where nukes are launched, the absolute costs are so great that the countries would NOT reach their nash equilibrium, but would hold back on launching nukes? Does that mean a scenario in which nukes are not used is the imperfect nash equilibrium?
“Shooting the moon” in hearts. A similar principle. (Did I get the lingo right?)