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 Apr17 comment What is the determinant of the sum of a diagonal matrix and a matrix of ones? See math.stackexchange.com/questions/219731/… (The chosen answer handles your case, even though the question doesn't) Mar31 awarded Nice Question Mar5 comment Expected Value of an inefficient estimator of the $\beta$ parameter of a simple linear regression $E[\tilde\beta]=\beta$ means the estimator is unbiased, not the same thing as consistency. Feb27 comment Proof of Frobenous Coin Problem lower bounds (Chicken McNugget theorem) Feb20 awarded Good Answer Feb17 answered What is the size of $\{(x_1,\ldots,x_n)\in\mathbb{R}^n:x_1+\cdots+x_n0\}$? Feb15 comment Measure of the set of periodic points of a measure preserving map In the specific case I was looking at the maps are invertible. If that restriction makes the problem tractable, by all means use it. Feb7 comment Measure of the set of periodic points of a measure preserving map That is what I meant by a rubber sheet, you are just pulling the outer ring, and the annulus stretches. Feb7 comment Measure of the set of periodic points of a measure preserving map The region is convex, therefore connected, and the map is definitely continuous (piecewise linear for now, but the general continuous case is of interest). Feb7 comment Measure of the set of periodic points of a measure preserving map Yes, I was assuming that $D$ was connected (in fact the case that I am interested in has $D$ convex. I have edited the question (which now feels like cheating). Feb7 revised Measure of the set of periodic points of a measure preserving map Added restriction to convexity Feb5 revised Measure of the set of periodic points of a measure preserving map Added close but no cigar example Feb4 asked Measure of the set of periodic points of a measure preserving map Sep30 awarded Explainer Sep20 comment A Step in the proof of Rate of Convergence of Steepest Descent in Nocedal's Numerical Optimization You are missing a $\bigtriangledown$ in your expansion. Next compute the derivative. Then remember the definition of $\bigtriangledown f$ in the first paragraph. Sep16 comment The number of lattice points in d-dimensional ball I think you need $d\ge 4$. The statement is definitely false for $d=1$ and $d=2$. Sep11 reviewed Approve Verify that the sets B and S are spanning sets for $\mathbb{R}^3$. Sep9 comment Strange factorial identity @Erik Thanks. This is not implicit in my bijection, however, it should not be hard to modify the argument to get it, I think (Don't quote me on that). Aug29 comment SQRTSORT from Vazirani's book on algorithms You can do a bubble sort like operation on blocks of $\sqrt{n}/2$ to do it in $O(n)$ SQRTSORT calls. Aug22 comment About putting $n$ distinct balls into $n$ distinct boxes. If you want it exactly, I think that you will end up with a complicated summation. If you want something tractable you can use that fact that the number of balls in a bin is approximately Poisson distributed with mean 1.