Abstract
For a non-negative measure \(\mu\) with p atoms, we study the relation between the Square Root Problem of \(\mu\) and the problem of subnormality of \({{\tilde{W}}_\mu }\) the Aluthge transform of the associated unilateral weighted shift. We use an approach based on uniquely represented elements in the support of \(\mu *\mu\). We first show that if \({{\tilde{W}}_\mu }\) is subnormal, then \(2p-1\le card(supp(\mu *\mu ))\le [\frac{(p-1)^2+6}{2}]\). We rewrite several results known for finitely atomic measure having at most five atoms and give a complete solution for measures six atoms.
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Communicated by Hugo Woerdeman.
The authors are supported by the CeReMaR and the Hassan II Academy of Sciences. The last author is supported by African University of Sciences and Technology-Abuja. Nigeria .
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El Azhar, H., Hanine, A., Idrissi, K. et al. Square root problem and subnormal Aluthge transforms. Ann. Funct. Anal. 14, 8 (2023). https://doi.org/10.1007/s43034-022-00232-2
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DOI: https://doi.org/10.1007/s43034-022-00232-2
Keywords
- Finitely atomic measures
- Support of multiplicative convolution
- Subnormal Aluthge transform of weighted shifts
- The Square root problem for measure