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  • $\begingroup$ Not really, because I have no idea what the argument of the Log is in general! If you know of a way of setting global assumptions on the argument of the Log function, that would certainly work. But I can't work out how to do this... $\endgroup$ Commented Jun 11, 2015 at 15:48
  • $\begingroup$ @EdwardHughes I'm not sure I understand. If at some point you have Log[-x^2] what would be a simplification? if x is imaginary the argument of Log is still positive $\endgroup$ Commented Jun 11, 2015 at 15:52
  • $\begingroup$ You simplification is exactly correct. It's just that I can't implement your strategy, because I don't actually know what will appear inside the Logs. It will involve some very complicated quantities in several variables coming from the expansion of hypergeometric functions. So I can't write an Assumption of z >0 because I don't know naively what form z will take! Maybe I could write Log[x_] > 0 as a pattern match assumption... I'll try that... $\endgroup$ Commented Jun 11, 2015 at 15:57
  • $\begingroup$ Yes, I got that. What would be the desired behavior for situation in my previous comment? Log[-x^2] $\endgroup$ Commented Jun 11, 2015 at 16:07
  • $\begingroup$ That's mathematically incorrect. $\endgroup$ Commented Jun 11, 2015 at 16:21