Abstract
We study positive semicharacters of generating Lie subsemigroup \(S\) of a connected Lie group \(G\). These semicharacters are important for positive representations of \(S\) in Hilbert space and for completely monotonic functions in \(S\). We describe the tangent map for a positive semicharacter and then obtain a necessary and sufficient condition for nontriviality of the wedge \(S_1^*\) consisting of all bounded positive semicharacters of \(S\). In particular \(S_1^*\) is nontrivial for a solvable simply connected \(G\) and invariant \(S\) without nontrivial subgroups, but it is trivial for a semisimple \(G\).
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Mirotin, A. Positive Semicharacters of Lie Semigroups. Positivity 3, 23–31 (1999). https://doi.org/10.1023/A:1009703125617
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DOI: https://doi.org/10.1023/A:1009703125617