Timeline for Characterisation of positive elements in l¹(Z)
Current License: CC BY-SA 2.5
4 events
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| Sep 4, 2010 at 21:25 | comment | added | Andreas Thom | That is true. What is meant is that the positive square-root (which exists in $C(S^1)$) does not lie in $\ell^1 {\mathbb Z}$. Otherwise, I think that Riesz proved that every non-negative Laurent polynomial is a hermitian square (or maybe sum of such squares). | |
| Sep 4, 2010 at 13:58 | comment | added | Rasmus | @Andreas: Regarding 4): Isn't $2-z-z^{-1}=(1-z^{-1})(1-z)=(1-z)^*(1-z)$? | |
| Sep 2, 2010 at 19:14 | history | edited | Andreas Thom | CC BY-SA 2.5 |
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| Sep 2, 2010 at 6:30 | history | answered | Andreas Thom | CC BY-SA 2.5 |