I edited my previous reply to trace(Y) from Y in the 2nd sentence.
Given the context you have now provided, your problem does appear to be non-convex, as you have apparently determined. SCA is an option for dealing with that, although no guarantees it will work well, or at all. Perhaps you’re already sort of doing this, but to move the odds of success more in your favor, given constraint (c), the penultimate paragraph of this post by Prof Stephen Boyd (his one and only post on this forum) might be the most pertinent, when suitably adapted to your problem. How to handle nonlinear equality constraints? - #5 by stephen_boyd for implementing the constraint in your 2nd post by SCA.