# Brian Borchers

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## Registered User

 Name Brian Borchers Member for 2 years Seen 2 days ago Website Location Socorro, NM Age 49
I'm a professor of mathematics at New Mexico Tech, in Socorro, NM. My mathematical interests are primarily in optimization and applications of optimization to parameter estimation and inverse problems, particularly in the earth sciences.
 Mar26 accepted minimization of a function when the feasible set is an unbounded cone Mar24 answered minimization of a function when the feasible set is an unbounded cone Mar5 comment Proof that polynomial evaluated at roots of unity is DFTYour notation seems a bit confused (and perhaps suggests why you're unable to establish this result.) You haven't explained what $a_{0}$, $a_{1}$, $...$ are. Feb3 comment Robust optimization in matlab using fminconThe poster has also put this same question up on scicomp.stackexchange.com, where she's somewhat more likely to get a useful answer, provided that she can clarify the question. Dec26 answered Projection and Positive matrices Dec26 revised Relating the angle between two vectors to max and min eigenvaluesdeleted 5 characters in body Dec26 comment Relating the angle between two vectors to max and min eigenvaluesYou can think of the $x_{i}^{2}$ as nonnegative weights that sum to one. This opens up the whole world of the generalized mean inequality. Dec26 answered Relating the angle between two vectors to max and min eigenvalues Dec16 comment How to solve a system of linear equations without storing the matrix?If the matrix isn't sparse, and the cost of getting individual matrix entries is large compared to the cost of accessing an element of a matrix stored in conventional dense matrix form, then iterative methods are going to be horribly slow in practice. Dec16 comment How to solve a system of linear equations without storing the matrix?Let me clarify what I meant here- "being able to get an arbitrary element M(i,j) at little cost" isn't very useful. If you don't know where the nonzero elements are in the matrix, then you have to check every single one to find the nonzeros. If you do happen to know where the nonzero elements are, and you can compute them quickly, then you could use this as a way to do matrix vector multiplications in an iterative method. Dec7 answered How to solve a system of linear equations without storing the matrix?