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Jun 7, 2019 at 21:41 history edited Piotr Hajlasz CC BY-SA 4.0
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Jul 23, 2018 at 4:17 history edited Piotr Hajlasz CC BY-SA 4.0
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Jun 5, 2018 at 19:45 comment added Piotr Hajlasz @MarkLewko Do you have a reference to the paper of Littlewood? I googled your quote and found it in notes of Tarry Tao, but there was no reference to a particular result to Littlewood.
Jun 5, 2018 at 19:29 comment added Mark Lewko I believe this predates Hormander. I've seen this attributed to Littlewood as the "the higher exponents are always on the left" principle.
Apr 23, 2018 at 19:11 history edited Piotr Hajlasz CC BY-SA 3.0
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Apr 7, 2018 at 21:57 history edited Suvrit CC BY-SA 3.0
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Apr 3, 2018 at 11:45 history edited Martin Sleziak CC BY-SA 3.0
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Mar 27, 2018 at 18:05 comment added paul garrett @JohannesHahn, your terminological objection certainly makes sense, but/and, depending on notation, the visibly reasonable terminology can vary. E.g., from the viewpoint of your comment, $T\circ \tau =\tau\circ T$ makes $T$ look $\tau$ equivariant, indeed. But/and if we declare that the action of $\tau$ is by $\tau\circ T\circ \tau^{-1}$, then $T$ "becomes" $\tau$ invariant. In my own experience this comes up a lot, and I use "equivariant" and "invariant" indiscriminantly, in part because of the inevitable ambiguity. (Esp., e.g., on ${\mathrm Hom}(X,Y)$ spaces with bimodules...)
Mar 27, 2018 at 16:02 history made wiki Post Made Community Wiki by Todd Trimble
Mar 27, 2018 at 15:30 history edited Piotr Hajlasz CC BY-SA 3.0
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Mar 27, 2018 at 15:11 comment added Piotr Hajlasz In harmonic analysis such operators are called translation-invariant, see reference [1] and many other books in harmonic analysis.
Mar 27, 2018 at 15:07 comment added Johannes Hahn Are those operators really called translation invariant ? Shouldn't they be called equivariant ? "invariant" to me suggests an condition of the form $T\circ\tau_a = T$.
Mar 27, 2018 at 14:58 history edited Piotr Hajlasz CC BY-SA 3.0
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Mar 27, 2018 at 14:26 history answered Piotr Hajlasz CC BY-SA 3.0