Is there a matrix norm induced by vector norm for 0<p<1?











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A matrix norm induced by vector norm defined here is $||A||_p$ with $pgeq 1$.
But how is matrix norm defined for $p<1$ ?



Edit:
I am asking this because in the second half of below theorem(in the image), where $r_sigma (A)$ represents spectral radius of A, $epsilon >0$ may be between 0 and 1. How is matrix norm defined then ?



enter image description here










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    The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
    – user1551
    Nov 18 at 14:27

















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1
down vote

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A matrix norm induced by vector norm defined here is $||A||_p$ with $pgeq 1$.
But how is matrix norm defined for $p<1$ ?



Edit:
I am asking this because in the second half of below theorem(in the image), where $r_sigma (A)$ represents spectral radius of A, $epsilon >0$ may be between 0 and 1. How is matrix norm defined then ?



enter image description here










share|cite|improve this question




















  • 1




    The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
    – user1551
    Nov 18 at 14:27















up vote
1
down vote

favorite









up vote
1
down vote

favorite











A matrix norm induced by vector norm defined here is $||A||_p$ with $pgeq 1$.
But how is matrix norm defined for $p<1$ ?



Edit:
I am asking this because in the second half of below theorem(in the image), where $r_sigma (A)$ represents spectral radius of A, $epsilon >0$ may be between 0 and 1. How is matrix norm defined then ?



enter image description here










share|cite|improve this question















A matrix norm induced by vector norm defined here is $||A||_p$ with $pgeq 1$.
But how is matrix norm defined for $p<1$ ?



Edit:
I am asking this because in the second half of below theorem(in the image), where $r_sigma (A)$ represents spectral radius of A, $epsilon >0$ may be between 0 and 1. How is matrix norm defined then ?



enter image description here







linear-algebra






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edited Nov 18 at 12:30

























asked Nov 18 at 11:34









Ganesh Gani

307




307








  • 1




    The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
    – user1551
    Nov 18 at 14:27
















  • 1




    The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
    – user1551
    Nov 18 at 14:27










1




1




The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
– user1551
Nov 18 at 14:27






The author probably doesn't mean that $|cdot|_epsilon$ is induced from $left(sum_{k=1}^n |x_k|^epsilonright)^{1/epsilon}$. What he/she means are most likely that (a) $|cdot|_epsilon$ is induced from some vector norm, and (b) for the given $A$, the inequality (7.3.24) holds. The $epsilon$ in $|cdot|_epsilon$ here is just a subscript. It doesn't indicate what vector norm the matrix norm is induced from. I don't know the context of the quoted passage, but it looks like a prelude to Gelfand's formula.
– user1551
Nov 18 at 14:27












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For vectors $x in mathbb{K}^n$ (with $mathbb{K}in {mathbb{R},mathbb{C}}$) the $p$-Norm $lVert cdot rVert_p$ is as well only defined for $p geq 1$.



The reason is, that for $p<1$ the usual definition $$lVert x rVert_p := left(sum_{k=1}^n |x_k|^pright)^{1/p}$$ doesn't result in a norm.






share|cite|improve this answer





















  • I have added few more things in question.
    – Ganesh Gani
    Nov 18 at 12:34










  • What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
    – Ganesh Gani
    Nov 18 at 12:36










  • Is there given a proof to the theorem?
    – bruderjakob17
    Nov 18 at 12:40










  • No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
    – Ganesh Gani
    Nov 18 at 13:47











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1 Answer
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up vote
0
down vote













For vectors $x in mathbb{K}^n$ (with $mathbb{K}in {mathbb{R},mathbb{C}}$) the $p$-Norm $lVert cdot rVert_p$ is as well only defined for $p geq 1$.



The reason is, that for $p<1$ the usual definition $$lVert x rVert_p := left(sum_{k=1}^n |x_k|^pright)^{1/p}$$ doesn't result in a norm.






share|cite|improve this answer





















  • I have added few more things in question.
    – Ganesh Gani
    Nov 18 at 12:34










  • What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
    – Ganesh Gani
    Nov 18 at 12:36










  • Is there given a proof to the theorem?
    – bruderjakob17
    Nov 18 at 12:40










  • No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
    – Ganesh Gani
    Nov 18 at 13:47















up vote
0
down vote













For vectors $x in mathbb{K}^n$ (with $mathbb{K}in {mathbb{R},mathbb{C}}$) the $p$-Norm $lVert cdot rVert_p$ is as well only defined for $p geq 1$.



The reason is, that for $p<1$ the usual definition $$lVert x rVert_p := left(sum_{k=1}^n |x_k|^pright)^{1/p}$$ doesn't result in a norm.






share|cite|improve this answer





















  • I have added few more things in question.
    – Ganesh Gani
    Nov 18 at 12:34










  • What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
    – Ganesh Gani
    Nov 18 at 12:36










  • Is there given a proof to the theorem?
    – bruderjakob17
    Nov 18 at 12:40










  • No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
    – Ganesh Gani
    Nov 18 at 13:47













up vote
0
down vote










up vote
0
down vote









For vectors $x in mathbb{K}^n$ (with $mathbb{K}in {mathbb{R},mathbb{C}}$) the $p$-Norm $lVert cdot rVert_p$ is as well only defined for $p geq 1$.



The reason is, that for $p<1$ the usual definition $$lVert x rVert_p := left(sum_{k=1}^n |x_k|^pright)^{1/p}$$ doesn't result in a norm.






share|cite|improve this answer












For vectors $x in mathbb{K}^n$ (with $mathbb{K}in {mathbb{R},mathbb{C}}$) the $p$-Norm $lVert cdot rVert_p$ is as well only defined for $p geq 1$.



The reason is, that for $p<1$ the usual definition $$lVert x rVert_p := left(sum_{k=1}^n |x_k|^pright)^{1/p}$$ doesn't result in a norm.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Nov 18 at 11:46









bruderjakob17

1286




1286












  • I have added few more things in question.
    – Ganesh Gani
    Nov 18 at 12:34










  • What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
    – Ganesh Gani
    Nov 18 at 12:36










  • Is there given a proof to the theorem?
    – bruderjakob17
    Nov 18 at 12:40










  • No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
    – Ganesh Gani
    Nov 18 at 13:47


















  • I have added few more things in question.
    – Ganesh Gani
    Nov 18 at 12:34










  • What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
    – Ganesh Gani
    Nov 18 at 12:36










  • Is there given a proof to the theorem?
    – bruderjakob17
    Nov 18 at 12:40










  • No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
    – Ganesh Gani
    Nov 18 at 13:47
















I have added few more things in question.
– Ganesh Gani
Nov 18 at 12:34




I have added few more things in question.
– Ganesh Gani
Nov 18 at 12:34












What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
– Ganesh Gani
Nov 18 at 12:36




What does matrix norm $||A||_epsilon$ represent when $0<epsilon <1$ ?
– Ganesh Gani
Nov 18 at 12:36












Is there given a proof to the theorem?
– bruderjakob17
Nov 18 at 12:40




Is there given a proof to the theorem?
– bruderjakob17
Nov 18 at 12:40












No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
– Ganesh Gani
Nov 18 at 13:47




No. Not given in that material. Its proof is a nontrivial construction, and a proof of it is given in Isaacson and Keller (1966, p. 12)
– Ganesh Gani
Nov 18 at 13:47


















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