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Feb 25, 2016 at 7:28 comment added Dima Pasechnik speaking about complexity, for SDPs in general is it not known, and so one has to tread carefully here.
Feb 25, 2016 at 3:39 comment added Noah Stein Interesting, I hadn't realized the two-variable case was tractable. I was referring to e.g. the fact that for the degree four case with $n$ variables, checking membership in the cone of nonnegative polynomials is NP-hard.
Feb 24, 2016 at 20:14 comment added Dima Pasechnik well, it what sense are they intractable? E.g. if you fix the number of variables, things are not as bad (e.g. for 2 variables things can be done in polynomial time, as we showed long time ago; dx.doi.org/10.1016/j.ejor.2003.08.014)
Feb 23, 2016 at 19:31 comment added Noah Stein Ok, well cones of nonnegative polynomials are more general than SDP cones, but unfortunately computationally intractable.
Feb 23, 2016 at 10:23 history edited Dima Pasechnik CC BY-SA 3.0
generalised more...
Feb 23, 2016 at 10:21 comment added Dima Pasechnik OK, it's not quite true what I just wrote. I meant cones of nonnegative polynomials.
Feb 23, 2016 at 10:20 comment added Dima Pasechnik this is only true asymptotically --- and then, you know, every nice function on a compact is asymptotically a polynomial, so why bother :-)
Feb 22, 2016 at 22:55 comment added Noah Stein But you can rewrite these sum of squares cones as projections of appropriate linear sections of larger positive semidefinite cones, so from a strict representability perspective you don't get anything new here.
Feb 22, 2016 at 21:54 history answered Dima Pasechnik CC BY-SA 3.0