Betrand

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Name Betrand
Member for 11 months
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Location Leningrad
Age
May
7
comment Literature on Exponential of a Quadratic Form
As each summand is concave, so f is concave. A relevant problem is when a product of quadratic form is convex. A reference comes to me is the paper "Lin, Sinnamon, A condition for convexity of a product of positive definite quadratic forms, SIAM J. Matrix Anal. Appl. 32 (2011) 457-462."
May
6
comment A spectral radius inequality
such that ?? in the first paragraph?
Apr
19
asked Schur product, partial order
Apr
9
comment Noncommutative arithmetic mean geometric mean inequality and symmetric polynomials
What do you mean by "The two matrix version of the my conjecture follows immediately from a stronger conjecture of Bhatia and Kittaneh that was actually recently resolved"?
Feb
6
comment Generalizations of Oppenheim’s inequality
This would be a big conjecture. I don't know the answer. Would you post it as a new problem.
Dec
28
comment a monotone relation for s-numbers
Thanks, but how do you define determinant? If $A, B$ are positive definite matrices, we have $|\det(2A+iB)|\ge |\det(A+iB)|$; see Lemma 5 of Kh. D. Ikramov, Determinantal inequalities for accretive-dissipative matrices, J. Math. Sci. (N. Y.), 121(2004) 2458-2464.
Dec
28
comment Optimization version of the Sylvester equation
You are welcome.
Dec
27
comment a monotone relation for s-numbers
A motivation is from the scalar case, as in this article math.pku.edu.cn/teachers/yaoy/Fall2011/…
Dec
27
comment a monotone relation for s-numbers
What if $A, B$ are positive definite?
Dec
27
revised When is a Schur complement an $M$-matrix?
added 1 characters in body
Dec
27
comment a monotone relation for s-numbers
they are self-ajoint
Dec
27
asked a monotone relation for s-numbers
Dec
26
answered Optimization version of the Sylvester equation
Dec
21
comment Proof of Tracenorm Equality
不 客 气。 互 相 帮 忙。^_^
Dec
20
accepted Proof of Tracenorm Equality
Dec
20
revised A curious inequality
edited tags
Dec
20
revised Proof of Tracenorm Equality
added 354 characters in body; deleted 1 characters in body
Dec
20
answered Proof of Tracenorm Equality
Dec
20
comment Proof of Tracenorm Equality
I think you should have put "the RHS is larger than or equal to the LHS".
Dec
20
comment is there any relationship between the eigenvector of sum(AA'+BB') and sum(A’A+B’B) ?
I guess $A′$ means the transpose. Steven shows the eigenvectors are generally different. However, there is an interesting relation between the eigenvalues, under a mild assumption. See Corollary 2.2. of Lin & Wolkowicz, An eigenvalue majorization inequality for positive semidefinite block matrices, Linear Multilinear Algebra, 60 (2012), 1365-1368.
Dec
7
comment A curious inequality
Here it is. Proposition 8 in Linear Algebra and its Applications 428 (2008) 305–315.
Dec
7
asked A curious inequality
Dec
6
comment How to calculate the inverse of the sum of two eigen-decomposed matrices
is $x$ given? Are $U, V$ unitary matrices?