Almost isometric constants for partial unconditionality
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- by R. M. Causey and S. J. Dilworth PDF
- Proc. Amer. Math. Soc. 144 (2016), 3397-3404 Request permission
Abstract:
We discuss optimal constants of certain projections on subsequences of weakly null sequences. Positive results yield constants arbitrarily close to $1$ for Schreier type projections, and arbitrarily close to $1$ for Elton type projections under the assumption that the weakly null sequence admits no subsequence generating a $c_0$ spreading model. As an application, we prove that a weakly null sequence admitting a spreading model not equivalent to the $c_0$ basis has a quasi-greedy subsequence with quasi-greedy constant arbitrarily close to $1$.References
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Additional Information
- R. M. Causey
- Affiliation: Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208
- MR Author ID: 923618
- Email: causey@math.sc.edu
- S. J. Dilworth
- Affiliation: Department of Mathematics, University of South Carolina, Columbia, South Carolina 29208
- MR Author ID: 58105
- Email: dilworth@math.sc.edu
- Received by editor(s): September 21, 2015
- Published electronically: March 25, 2016
- Additional Notes: The second author was supported by the National Science Foundation under Grant Number DMS-1361461
- Communicated by: Thomas Schlumprecht
- © Copyright 2016 American Mathematical Society
- Journal: Proc. Amer. Math. Soc. 144 (2016), 3397-3404
- MSC (2010): Primary 46B15, 41A65
- DOI: https://doi.org/10.1090/proc/13004
- MathSciNet review: 3503707