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Jul 19, 2020 at 20:40 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 20:38 comment added Boby @J. Basically your approach counts the number of zeros of $q(X)$. Since there are at most two zeros, the result follows. My question then is: This is essentially all we can do with these equations just count zeros? Or is there some inversion that is possible?
Jul 19, 2020 at 20:21 comment added Boby @J. Thanks. This is nice. Also, yes, less hands-on would be good. I want to use this optimization problem as an introductory example to convex optimization over p.d. spaces. Therefore, it would be good to use things that are less hands-on and easily generalize.
Jul 19, 2020 at 19:59 comment added Alf The second KKT condition implies that there exists a nontrivial quadratic function $q$ such that $q(X) = 0$ almost surely. Therefore $P_X$ is supported on at most 2 points, and by the first equation these must be 0 and 1. The second equation then yields that indeed he made must be balanced. Or are you looking for something less hands on than this?
Jul 19, 2020 at 16:10 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 13:13 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 13:13 comment added Boby @Dirk Yes, there should be an inequality outside of support. I will correct it. I would be very interested in looking at a dual approach, so if you have time please add some details or thoughts on how in.
Jul 19, 2020 at 12:34 comment added Dirk I think that duality may help here. The (pre-)dual should be a convex minimization problem on the space of continuous functions. But I didn't think any further than that... On a second thought: I think that optimality conditions should say a bit more, namely that you have equality only on the support (i.e. the inequality is strict outside the support).
Jul 19, 2020 at 11:35 history edited Rodrigo de Azevedo CC BY-SA 4.0
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Jul 19, 2020 at 11:24 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 11:24 comment added Boby @RodrigodeAzevedo It's in a bullet point 1). I will clarify this.
Jul 19, 2020 at 11:22 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 11:13 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 11:11 history edited Boby CC BY-SA 4.0
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Jul 19, 2020 at 7:01 review Close votes
Jul 24, 2020 at 9:44
Jul 19, 2020 at 1:46 history edited YCor CC BY-SA 4.0
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Jul 19, 2020 at 1:37 history edited Boby CC BY-SA 4.0
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S Jul 19, 2020 at 1:36 history suggested RobPratt CC BY-SA 4.0
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Jul 19, 2020 at 1:36 review Suggested edits
S Jul 19, 2020 at 1:36
Jul 19, 2020 at 1:29 history asked Boby CC BY-SA 4.0