Does there exist a connection between contractive completely positive map and surjective map

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If $psi:A rightarrow M_n(mathbbC)$ is a c.c.p map.What is the relationship between c.c.p maps and surjective maps?Can we deduce that $psi$ is a surjective map?If not,does there a close connection between a c.c.p map and a homomorphism?







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  • No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
    – Prahlad Vaidyanathan
    Aug 1 at 2:29














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If $psi:A rightarrow M_n(mathbbC)$ is a c.c.p map.What is the relationship between c.c.p maps and surjective maps?Can we deduce that $psi$ is a surjective map?If not,does there a close connection between a c.c.p map and a homomorphism?







share|cite|improve this question



















  • No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
    – Prahlad Vaidyanathan
    Aug 1 at 2:29












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up vote
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If $psi:A rightarrow M_n(mathbbC)$ is a c.c.p map.What is the relationship between c.c.p maps and surjective maps?Can we deduce that $psi$ is a surjective map?If not,does there a close connection between a c.c.p map and a homomorphism?







share|cite|improve this question











If $psi:A rightarrow M_n(mathbbC)$ is a c.c.p map.What is the relationship between c.c.p maps and surjective maps?Can we deduce that $psi$ is a surjective map?If not,does there a close connection between a c.c.p map and a homomorphism?









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asked Jul 31 at 16:29









mathrookie

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  • No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
    – Prahlad Vaidyanathan
    Aug 1 at 2:29
















  • No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
    – Prahlad Vaidyanathan
    Aug 1 at 2:29















No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
– Prahlad Vaidyanathan
Aug 1 at 2:29




No, as mentioned below. However, there is a useful correspondence between ccp maps into $M_n(mathbbC)$ and certain linear functionals on $M_n(A)$. Have a look at Chapter 6 of Vern Paulsen's book "Completely bounded maps and operator algebras".
– Prahlad Vaidyanathan
Aug 1 at 2:29










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No, not at all. Take any state $f$ on $A$, and then $alongmapsto f(a),I$ is ucp and it is as far from surjective as it can be (well, more properly, the zero map is also ccp; my example is unital, at least).



As for $*$-homomorphisms, they are all ccp (easy exercise, that should definitely be done if it is not obvious to you).






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    No, not at all. Take any state $f$ on $A$, and then $alongmapsto f(a),I$ is ucp and it is as far from surjective as it can be (well, more properly, the zero map is also ccp; my example is unital, at least).



    As for $*$-homomorphisms, they are all ccp (easy exercise, that should definitely be done if it is not obvious to you).






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      No, not at all. Take any state $f$ on $A$, and then $alongmapsto f(a),I$ is ucp and it is as far from surjective as it can be (well, more properly, the zero map is also ccp; my example is unital, at least).



      As for $*$-homomorphisms, they are all ccp (easy exercise, that should definitely be done if it is not obvious to you).






      share|cite|improve this answer























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        No, not at all. Take any state $f$ on $A$, and then $alongmapsto f(a),I$ is ucp and it is as far from surjective as it can be (well, more properly, the zero map is also ccp; my example is unital, at least).



        As for $*$-homomorphisms, they are all ccp (easy exercise, that should definitely be done if it is not obvious to you).






        share|cite|improve this answer













        No, not at all. Take any state $f$ on $A$, and then $alongmapsto f(a),I$ is ucp and it is as far from surjective as it can be (well, more properly, the zero map is also ccp; my example is unital, at least).



        As for $*$-homomorphisms, they are all ccp (easy exercise, that should definitely be done if it is not obvious to you).







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        answered Jul 31 at 23:34









        Martin Argerami

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