# On the defect spectrum of an extension of a Banach space operator

Czechoslovak Mathematical Journal (1998)

- Volume: 48, Issue: 4, page 609-616
- ISSN: 0011-4642

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topKordula, Vladimír. "On the defect spectrum of an extension of a Banach space operator." Czechoslovak Mathematical Journal 48.4 (1998): 609-616. <http://eudml.org/doc/30441>.

@article{Kordula1998,

abstract = {Let $T$ be an operator acting on a Banach space $X$. We show that between extensions of $T$ to some Banach space $Y\supset X$ which do not increase the defect spectrum (or the spectrum) it is possible to find an extension with the minimal possible defect spectrum.},

author = {Kordula, Vladimír},

journal = {Czechoslovak Mathematical Journal},

keywords = {extensions of operators; approximate point spectrum; defect spectrum},

language = {eng},

number = {4},

pages = {609-616},

publisher = {Institute of Mathematics, Academy of Sciences of the Czech Republic},

title = {On the defect spectrum of an extension of a Banach space operator},

url = {http://eudml.org/doc/30441},

volume = {48},

year = {1998},

}

TY - JOUR

AU - Kordula, Vladimír

TI - On the defect spectrum of an extension of a Banach space operator

JO - Czechoslovak Mathematical Journal

PY - 1998

PB - Institute of Mathematics, Academy of Sciences of the Czech Republic

VL - 48

IS - 4

SP - 609

EP - 616

AB - Let $T$ be an operator acting on a Banach space $X$. We show that between extensions of $T$ to some Banach space $Y\supset X$ which do not increase the defect spectrum (or the spectrum) it is possible to find an extension with the minimal possible defect spectrum.

LA - eng

KW - extensions of operators; approximate point spectrum; defect spectrum

UR - http://eudml.org/doc/30441

ER -

## References

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- To what extent can the spectrum of an operator be diminished under an extension, in: Linear and Complex Analysis Problem Book, V. P. Havin, S. V. Hruščev and N. K. Nikol’skij (eds.), Lecture Notes in Math. 1043, Springer, Berlin 1984, 210, .
- Adjoint inverses to noncommutative Banach algebras and extensions of operator, Studia Math. 91 (1988), 73–77. (1988) MR0957286
- On the joint essential spectrum of commuting operators, Acta Sci. Math. Szeged 57 (1993), 199–205. (1993) MR1243277
- 10.1090/S0002-9947-1988-0946450-5, Trans. Amer. Math. Soc. 308 (1988), 413–429. (1988) MR0946450DOI10.1090/S0002-9947-1988-0946450-5
- On the joint spectra of commuting families of operators, Studia Math. 50 (1974), 127–148. (1974) MR0346555
- On a problem concerning joint approximate point spectra, Studia Math. 45 (1973), 239–240. (1973) Zbl0256.47002MR0336382

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