A Nonsmooth Continuous Unitary Representation of a Banach-Lie Group
Journal of Lie Theory, Volume 18 (2008) no. 4, pp. 933-936
We show that the representation of the additive group of the Hilbert space $L^2([0,1],{\mathbb R})$ on $L^2([0,1], {\mathbb C})$ given by the multiplication operators $\pi(f) := e^{if}$ is continuous but its space of smooth vectors is trivial. This example shows that a continuous unitary representation of an infinite dimensional Lie group need not be smooth.
DOI: 10.5802/jolt.534
Classification: 22E65, 22E45
Keywords: Infinite-dimensional Lie group, unitary representation, smooth vector
@article{JOLT_2008_18_4_a11,
     author = {D. Beltita and K.-H. Neeb},
     title = {A {Nonsmooth} {Continuous} {Unitary} {Representation} of a {Banach-Lie} {Group}},
     journal = {Journal of Lie Theory},
     pages = {933--936},
     year = {2008},
     volume = {18},
     number = {4},
     doi = {10.5802/jolt.534},
     zbl = {1203.22013},
     url = {https://jolt.centre-mersenne.org/articles/10.5802/jolt.534/}
}
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D. Beltita; K.-H. Neeb. A Nonsmooth Continuous Unitary Representation of a Banach-Lie Group. Journal of Lie Theory, Volume 18 (2008) no. 4, pp. 933-936. doi: 10.5802/jolt.534

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