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Abstract
Three approximation problems in Krein spaces are studied, namely the indefinite weighted least squares problem and the related problems of indefinite abstract splines and smoothing. In each case, we analyse the existence of a linear and continuous operator that maps each data point to its solution and when the associated operator problem considering the J-trace has a solution.
Acknowledgments
M. Contino was supported by CONICET PIP 11220200102127CO, by María Zambrano Postdoctoral Grant CT33/21 at Universidad Complutense de Madrid financed by the Ministry of Universities with Next Generation EU funds and by Grant CEX2019-000904-S funded by MCIN/AEI/10.13039/501100011033.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Additional information
Funding
This work was supported by CONICET PIP 11220200102127CO, María Zambrano Post-doctoral Grant CT33/21 at Universidad Complutense de Madrid financed by the Ministry of Universities with Next Generation EU funds and Grant CEX2019-000904-S funded by MCIN/AEI/10.13039/501100011033.