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Jun
22
answered Brun's algorithm
Feb
17
comment Spectrum of primitive nonnegative integer matrices
Right now the best I can do is to enumerate all the matrices (using the trace constraint) and test them one by one... Can anyone think of a less stupid approach?
Feb
17
comment Spectrum of primitive nonnegative integer matrices
Gerry, I haven't looked at it for hours but it doesn't seem to be obvious even for $2\times2$ matrices.
Feb
17
comment Spectrum of primitive nonnegative integer matrices
David, unfortunately I would like to avoid the additional zero eigenvalues. Is this question open even without the primitivity assumption? Thanks for the very interesting articles!
Feb
16
asked Spectrum of primitive nonnegative integer matrices
Feb
17
comment What are the most attractive Turing undecidable problems in mathematics?
Note the recent preprint arxiv.org/abs/1312.6700 which improves these results. Undecidability now holds for five 3*3 matrices or two 15*15 matrices.
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Apr
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answered Equivalent subshifts
Apr
18
revised What's the difference between 2 and 3?
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Apr
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answered What's the difference between 2 and 3?
Mar
22
comment Importance of Poincaré recurrence theorem? Any example?
The ergodic theorems can be seen as improvements of the Poincaré recurrence theorem, because they relate the time average with the space average. However, the Poincaré theorem is treated first because it is not hard to prove and it is very nice.
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3
answered Computational software in Algebraic Topology?
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5
answered More open problems
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