From 8b9bb9346c217874670b0f1798ab6f1cb28fdb83 Mon Sep 17 00:00:00 2001 From: Justin Gassner Date: Tue, 20 Feb 2024 12:01:07 +0100 Subject: Update --- pages/spectral-theory/test/basic.md | 55 ++++++++++++++++++------------------- 1 file changed, 27 insertions(+), 28 deletions(-) (limited to 'pages/spectral-theory') diff --git a/pages/spectral-theory/test/basic.md b/pages/spectral-theory/test/basic.md index b1015d1..9fa409b 100644 --- a/pages/spectral-theory/test/basic.md +++ b/pages/spectral-theory/test/basic.md @@ -7,34 +7,33 @@ nav_order: 2 # {{ page.title }} -{: .definition-title } -> Definition (resolvent operator, regular value, resolvent set, spectrum, spectral value) -> -> Let $T : \dom{T} \to X$ be an operator in a complex normed space $X$. -> We write -> -> $$ -> T_{\lambda} = T - \lambda = T - \lambda I, -> $$ -> -> where $\lambda$ is a complex number and -> $I$ is the identical operator on the domain of $T$. -> If the operator $T_{\lambda}$ is injective, -> that is, it has an inverse $T_{\lambda}^{-1}$ -> (with domain $\ran{T_{\lambda}}$), -> then we call -> -> $$ -> R_{\lambda}(T) = T_{\lambda}^{-1} = (T - \lambda)^{-1} = (T - \lambda I)^{-1} -> $$ -> -> the *resolvent operator* of $T$ for $\lambda$. -> A *regular value* of $T$ is a complex number $\lambda$ for which the resolvent $R_{\lambda}(T)$ exists, -> has dense domain and is bounded. -> The set of all regular values of $T$ is called the *resolvent set* of $T$ and denoted $\rho(T)$. -> The complement of the resolvent set in the complex plane -> is called the *spectrum* of $T$ and denoted $\sigma(T)$. -> The elements of the spectrum of $T$ are called the *spectral values* of $T$. +{% definition %} +Let $T : \dom{T} \to X$ be an operator in a complex normed space $X$. +We write + +$$ +T_{\lambda} = T - \lambda = T - \lambda I, +$$ + +where $\lambda$ is a complex number and +$I$ is the identical operator on the domain of $T$. +If the operator $T_{\lambda}$ is injective, +that is, it has an inverse $T_{\lambda}^{-1}$ +(with domain $\ran{T_{\lambda}}$), +then we call + +$$ +R_{\lambda}(T) = T_{\lambda}^{-1} = (T - \lambda)^{-1} = (T - \lambda I)^{-1} +$$ + +the *resolvent operator* of $T$ for $\lambda$. +A *regular value* of $T$ is a complex number $\lambda$ for which the resolvent $R_{\lambda}(T)$ exists, +has dense domain and is bounded. +The set of all regular values of $T$ is called the *resolvent set* of $T$ and denoted $\rho(T)$. +The complement of the resolvent set in the complex plane +is called the *spectrum* of $T$ and denoted $\sigma(T)$. +The elements of the spectrum of $T$ are called the *spectral values* of $T$. +{% enddefinition %} {% definition Point Spectrum, Residual Spectrum, Continuous Spectrum %} Let $T : \dom{T} \to X$ be an operator in a complex normed space $X$. -- cgit v1.2.3-54-g00ecf