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Nonlinear objectives, nonlinear constraints, non-convex objective, non-convex feasible region.

1 vote
Accepted

A unit vector that maximizes variance in a discrete probability distribution

Define the $n\times n$ symmetric matrix $M$ with elements $$M_{ij}=\pi_i \delta_{ij}-\pi_i\pi_j.$$ We seek to maximise the quadratic form $$f(v)=\sum_{ij} v_i M_{ij} v_j$$ where $v$ is a vector on the …
Carlo Beenakker's user avatar
1 vote

How to determine the damping factor in Levenberg-Marquardt?

The damping factor is expressed in terms of the objective function that one seeks to minimise, as described in A new approach for determining damping factors in Levenberg-Marquardt algorithm for solvi …
Carlo Beenakker's user avatar
2 votes

Why is the Ekeland variational principle called a principle?

In this particular case the word "principle" most likely became attached to Ekeland's variational theorem because of the title of the paper where he derived it:
Carlo Beenakker's user avatar
2 votes

How to calculate the maximum dimensions of a rectangle inside two concentric circles?

If $(x,y)$ is the coordinate of the upper right corner of the rectangle, with the origin at the center of the circles (inner radius $r_1$, outer radius $r_2$), then the area of the rectangle is $A=2x( …
Carlo Beenakker's user avatar
2 votes
Accepted

equality between the ratio trace and the determinant ratio

The equality of the arg max of the trace of the ratio and the ratio of determinants follows from the fact that each of these two maximisation problems has the same solution, given by the matrix $S$ co …
Carlo Beenakker's user avatar
3 votes

How to find the minimum of the integral?

Set $x(0)=x_0$ and $x(T)=x_T$, with $x_0,x_T\in[m,M]$. I will first allow for excursions outside of this interval, and then later add the constraint that $m\leq x(t)\leq M$ for all $0\leq t\leq T$. M …
Carlo Beenakker's user avatar
1 vote

Understanding an argument involving the Sherrington-Kirkpatrick spin glass model

I would argue as follows: unitary invariance means you are free to choose a basis. Let me choose the basis where $\tilde\phi=\{1,0,0,\ldots,0,0\}$, then $H_J(\sigma)-\tilde\lambda\langle\tilde\phi|\si …
Carlo Beenakker's user avatar
1 vote

Integrals can sometimes be computed through their saddle points. Are there examples of conve...

This is not an answer, but continuing the discussion in the comment box is a bit cumbersome. The point I want to make is to see if this would work for a simple test case, $f(t)=ix\sin\pi t$, with sadd …
Carlo Beenakker's user avatar
4 votes

About optimization with Renyi divergence

For the requested examples see Rényi Divergence and Kullback-Leibler Divergence (2012). • Two continuous distributions: Equation 10 gives the Rényi divergence between two Gaussian distributions (mean …
Carlo Beenakker's user avatar