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djalil.chafai.net | ||
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nhigham.com
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| | | | | In linear algebra terms, a correlation matrix is a symmetric positive semidefinite matrix with unit diagonal. In other words, it is a symmetric matrix with ones on the diagonal whose eigenvalues are all nonnegative. The term comes from statistics. If $latex x_1, x_2, \dots, x_n$ are column vectors with $latex m$ elements, each vector containing... | |
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nickhar.wordpress.com
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| | | | | 1. Low-rank approximation of matrices Let $latex {A}&fg=000000$ be an arbitrary $latex {n \times m}&fg=000000$ matrix. We assume $latex {n \leq m}&fg=000000$. We consider the problem of approximating $latex {A}&fg=000000$ by a low-rank matrix. For example, we could seek to find a rank $latex {s}&fg=000000$ matrix $latex {B}&fg=000000$ minimizing $latex { \lVert A - B... | |
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mycqstate.wordpress.com
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| | | | | Today I'd like to sketch a question that's been pushing me in a lot of different directions over the past few years --- some sane, others less so; few fruitful, but all instructive. The question is motivated by the problem of placing upper bounds on the amount of entanglement needed to play a two-player non-local... | |
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entangledlogs.com
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| | | To visualize quaternions in the fanciest way, visit Ben eater, Quaternion. Euler angles suffer from a problem of gimbal lock. When rotating around a 3-perpendicular axis in euclidean space, if either two of these axes align i.e becomes parallel, it causes gimbal lock. Once the object is locked, the object will lose one degree of freedom for rotation. This video provides an intuitive explanation of the problem. Pitfalls When converting the Euler angle to a quaternion, it will lose some information. | ||
