On D-hyponormal operators
Abstract A Drazin invertible operator T on a Hilbert space is said to be of class [ D H ] $[DH] $ if T ∗ T D ≥ T D T ∗ $T^{*}T^{D}\geq T^{D}T^{*} $ . Our findings contribute to the deeper understanding of D-hyponormal operators by proving several key inequalities and generalizing fundamental results...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2025-05-01
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| Series: | Journal of Inequalities and Applications |
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| Online Access: | https://doi.org/10.1186/s13660-025-03309-3 |
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| _version_ | 1850154544006168576 |
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| author | Mansour Dana Fateme Kousari Ramesh Yousefi |
| author_facet | Mansour Dana Fateme Kousari Ramesh Yousefi |
| author_sort | Mansour Dana |
| collection | DOAJ |
| description | Abstract A Drazin invertible operator T on a Hilbert space is said to be of class [ D H ] $[DH] $ if T ∗ T D ≥ T D T ∗ $T^{*}T^{D}\geq T^{D}T^{*} $ . Our findings contribute to the deeper understanding of D-hyponormal operators by proving several key inequalities and generalizing fundamental results. We show that T has the Bishop’s property ( β ) $(\beta ) $ . We prove the Putnam’s inequality, Berger–Shaw’s inequality and Weyl’s theorem for D-hyponormal operators. Also, we prove a Fuglede–Putnam commutativity theorem for D-hyponormal operators. In the following, we extend Kaplansky’s well-known result on products of normal operators to D-hyponormal operators. Moreover, we characterize the quasinilpotent part H 0 ( T − λ ) $\mathcal{H}_{0} (T- \lambda ) $ of T both when T is D-hyponormal and when T is algebraically D-hyponormal. Finally, let λ be an isolated point of σ ( T ) $\sigma (T) $ and E be the Riesz idempotent for λ. We prove that (1) if λ ≠ 0 $\lambda \neq 0 $ , then E is self-adjoint and E H = N ( T − λ ) = N ( T − λ ) ∗ $E\mathcal{H} = \mathcal{N}(T - \lambda ) = \mathcal{N}{(T - \lambda )^{*}} $ ; (2) if λ = 0 $\lambda = 0 $ , then E H = N ( T ) k $E\mathcal{H}= \mathcal{N}(T)^{k} $ . |
| format | Article |
| id | doaj-art-7363845adea341e08569a7e57700ecd9 |
| institution | OA Journals |
| issn | 1029-242X |
| language | English |
| publishDate | 2025-05-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Journal of Inequalities and Applications |
| spelling | doaj-art-7363845adea341e08569a7e57700ecd92025-08-20T02:25:17ZengSpringerOpenJournal of Inequalities and Applications1029-242X2025-05-012025111910.1186/s13660-025-03309-3On D-hyponormal operatorsMansour Dana0Fateme Kousari1Ramesh Yousefi2Faculty of Mathematics, University of KurdistanFaculty of Mathematics, University of KurdistanFaculty of Mathematics, University of KurdistanAbstract A Drazin invertible operator T on a Hilbert space is said to be of class [ D H ] $[DH] $ if T ∗ T D ≥ T D T ∗ $T^{*}T^{D}\geq T^{D}T^{*} $ . Our findings contribute to the deeper understanding of D-hyponormal operators by proving several key inequalities and generalizing fundamental results. We show that T has the Bishop’s property ( β ) $(\beta ) $ . We prove the Putnam’s inequality, Berger–Shaw’s inequality and Weyl’s theorem for D-hyponormal operators. Also, we prove a Fuglede–Putnam commutativity theorem for D-hyponormal operators. In the following, we extend Kaplansky’s well-known result on products of normal operators to D-hyponormal operators. Moreover, we characterize the quasinilpotent part H 0 ( T − λ ) $\mathcal{H}_{0} (T- \lambda ) $ of T both when T is D-hyponormal and when T is algebraically D-hyponormal. Finally, let λ be an isolated point of σ ( T ) $\sigma (T) $ and E be the Riesz idempotent for λ. We prove that (1) if λ ≠ 0 $\lambda \neq 0 $ , then E is self-adjoint and E H = N ( T − λ ) = N ( T − λ ) ∗ $E\mathcal{H} = \mathcal{N}(T - \lambda ) = \mathcal{N}{(T - \lambda )^{*}} $ ; (2) if λ = 0 $\lambda = 0 $ , then E H = N ( T ) k $E\mathcal{H}= \mathcal{N}(T)^{k} $ .https://doi.org/10.1186/s13660-025-03309-3Drazin inverseD-hyponormal operatorFuglede–Putnam theoremBishop’s propertyRiesz idempotentQuasinilpotent part |
| spellingShingle | Mansour Dana Fateme Kousari Ramesh Yousefi On D-hyponormal operators Journal of Inequalities and Applications Drazin inverse D-hyponormal operator Fuglede–Putnam theorem Bishop’s property Riesz idempotent Quasinilpotent part |
| title | On D-hyponormal operators |
| title_full | On D-hyponormal operators |
| title_fullStr | On D-hyponormal operators |
| title_full_unstemmed | On D-hyponormal operators |
| title_short | On D-hyponormal operators |
| title_sort | on d hyponormal operators |
| topic | Drazin inverse D-hyponormal operator Fuglede–Putnam theorem Bishop’s property Riesz idempotent Quasinilpotent part |
| url | https://doi.org/10.1186/s13660-025-03309-3 |
| work_keys_str_mv | AT mansourdana ondhyponormaloperators AT fatemekousari ondhyponormaloperators AT rameshyousefi ondhyponormaloperators |