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Jan 5, 2018 at 22:36 comment added user90189 Did you notice that in $\mathbb{R}^2$, the distribution $\langle T,\phi\rangle = \int \phi(x,0)\,dx+\int\phi(0,y)\,dy$ is an eigenvalue? There are other similar examples.
Dec 20, 2017 at 7:17 review Close votes
Dec 20, 2017 at 8:45
Dec 20, 2017 at 7:01 comment added Nemo Possible duplicate of What are fixed points of the Fourier Transform
Apr 13, 2017 at 12:58 history edited CommunityBot
replaced http://mathoverflow.net/ with https://mathoverflow.net/
May 11, 2016 at 13:25 history edited Denis Serre CC BY-SA 3.0
added 6 characters in body
May 11, 2016 at 12:39 comment added Gro-Tsen Not claiming to answer your question, but in $L^2(\mathbb{R})$, an orthonormal basis that diagonalizes the Fourier transform is given by the Hermite functions $H_n(x)\,e^{-x^2/2}$. The closed span of those for $n$ multiple of $4$ gives a convenient description of $L^2$ functions equal to their Fourier transform.
May 11, 2016 at 12:38 comment added Jochen Wengenroth The answer in your edit has almost nothing to do with Fourier transformation and uses only linearity and the periodicity. Are you really satisfied by this characterization?
May 11, 2016 at 12:15 history edited Bazin CC BY-SA 3.0
I found the answer, thanks to your answers and to the reference: http://mathoverflow.net/questions/12045/what-are-fixed-points-of-the-fourier-transform?lq=1
May 10, 2016 at 17:24 comment added Bazin I am most grateful for all the answers below. However I am looking for all the tempered distributions solutions $T$ such that $\mathcal F T=T$.
May 10, 2016 at 13:42 answer added Alexandre Eremenko timeline score: 9
May 10, 2016 at 13:05 answer added Igor Rivin timeline score: 10
May 10, 2016 at 13:03 answer added Carlo Beenakker timeline score: 24
May 10, 2016 at 12:47 history asked Bazin CC BY-SA 3.0