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GNS-like representations of a quasi *-algebra in Krein spaces
Abstract
In this paper unbounded representations of quasi *-algebras on an indefinite inner product space are introduced and studied. After introducing the partial *-algebra of unbounded closable operators sharing a common dense domain in a Krein space, the appropriate notion of *-representation in this setting is developed, and a GNS-type construction for quasi *-algebras based on α-positive sesquilinear forms is established. Furthermore, the notion of abstract conditional expectation is generalized to quasi *-algebras and how \emph{admissible} abstract conditional expectations P give rise to representable P-forms is shown. The relation between α-positive forms and P-forms is also clarified. Several examples are provided.
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BibTeX
@misc{bellomonte2026gnslike,
title = {{GNS-like representations of a quasi *-algebra in Krein spaces}},
author = {Giorgia Bellomonte},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.08329},
eprint = {2611.08329},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.08329},
}
RIS
TY - UNPB
TI - GNS-like representations of a quasi *-algebra in Krein spaces
AU - Giorgia Bellomonte
PY - 2026
DA - 2026/11/05
PB - arXiv
DO - 10.48550/arxiv.2611.08329
UR - https://arxiv.org/abs/2611.08329
AB - In this paper unbounded representations of quasi *-algebras on an indefinite inner product space are introduced and studied. After introducing the partial *-algebra of unbounded closable operators sharing a common dense domain in a Krein space, the appropriate notion of *-representation in this setting is developed, and a GNS-type construction for quasi *-algebras based on α-positive sesquilinear forms is established. Furthermore, the notion of abstract conditional expectation is generalized to quasi *-algebras and how \emph{admissible} abstract conditional expectations P give rise to representable P-forms is shown. The relation between α-positive forms and P-forms is also clarified. Several examples are provided.
ER -