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location Washington, DC
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visits member for 3 years, 9 months
seen Jan 22 at 1:37

I am a math professor at Georgetown University, with broad mathematical interests.

Check out the textbook "Mathematics and Climate" by Hans Kaper and me, published in October 2013 by SIAM.


Jan
20
reviewed Close Roots of permutations
Jan
20
reviewed Close Calculus exam question logic help?
Jan
20
comment Calculus exam question logic help?
Draw a picture (done), introduce variables, label the picture with variables as appropriate, write down relations between the variables using all the information given. Then write this down as "this is what I have done" and post your question. Even better, you may be able to solve it all on your own at that point.
Jan
20
reviewed Leave Open combination of stones on chess board $5\times 5$
Jan
20
reviewed Close Proof for Goldbach's Conjecture
Jan
20
reviewed Close Discrete Mathematics question dealing with partitions.
Jan
20
reviewed Leave Open Probability of Topological space
Jan
20
reviewed Close Must local ring have multiplicative identity?
Jan
20
reviewed Close Remainder of division
Jan
20
comment A complex Analysis proof
Try to prove that the squares are equal to each other, using the definition $|z|^2 = z \bar{z}$.
Jan
17
comment $f,g\in L^1(\mu)\implies fg\in L^1(\mu)$
This is in general not correct. Take the measure space $(0,1)$ with Lebesgue measure and $f=g$ defined as $f(x) = x^{-3/4}$.
Jan
17
reviewed Close To check differentiability of Multivariable function defined at rationals
Jan
17
reviewed Close Simplifying a hyperbolic trigonometric expression
Jan
17
reviewed Close Proof of the Greatest Denominator
Jan
17
reviewed Leave Open Create a Martingale out of a Markov Chain.
Jan
17
reviewed Leave Open Why is the “i” disappearing?
Jan
17
comment Implicit Differentiation: $(x/y)+(y/x) =1$
Welcome to math.stackexchange! Nice work explaining and typesetting your work. As to your question: You can cancel $y^2-x^2$ in your expression and then you are there.
Jan
17
comment How to generate $2\times 2$ matrix with integer entries and both eigenvalues inside unit disk
Welcome to math.stackexchange! It's good that you are indicating what you have attempted. Now to your question: Think about the determinant (product of eigenvalues) and the trace (sum of eigenvalues) of such a matrix. They must both be integers. That does not leave a lot of options.
Jan
17
comment How does additive noise change the SVD
See the discussion here: mathoverflow.net/questions/111827/…. A very thorough reference is R. J. Muirhead (1982) Aspects of Multivariate Statistical Theory. John Wiley & Sons Inc., New York.
Jan
17
reviewed Leave Open calculating $y$ from the equation $u^Tv=x^Ty$ (all vectors)