Question regarding the image of the unity $e$ of the ring $R$.












1














I was reading Ring Homomorphism .



$phi : R to R'$ is a ring homomorphism and $e , e'$ are the unities of $R $ and $R'$ respectively.



I understood that $phi (e) $ may not be unity of $R'$.



I think the following statements are true.



( 1 ) $phi (e) $ is always unity of $phi (R) $ .



(2) If $phi $ is on to then $phi (e) = e'$



(3) If $phi $ is non trivial and $R'$ is a field then $phi (e) = e'$.



Can someone check if there is any mistake in my understanding?










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  • $phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
    – cmi
    Dec 11 '18 at 4:47












  • Did you understand or not?@BadamBaplan
    – cmi
    Dec 11 '18 at 4:56










  • $phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
    – cmi
    Dec 11 '18 at 5:08










  • No no unity@BadamBaplan
    – cmi
    Dec 11 '18 at 5:09










  • Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
    – Badam Baplan
    Dec 11 '18 at 5:31
















1














I was reading Ring Homomorphism .



$phi : R to R'$ is a ring homomorphism and $e , e'$ are the unities of $R $ and $R'$ respectively.



I understood that $phi (e) $ may not be unity of $R'$.



I think the following statements are true.



( 1 ) $phi (e) $ is always unity of $phi (R) $ .



(2) If $phi $ is on to then $phi (e) = e'$



(3) If $phi $ is non trivial and $R'$ is a field then $phi (e) = e'$.



Can someone check if there is any mistake in my understanding?










share|cite|improve this question
























  • $phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
    – cmi
    Dec 11 '18 at 4:47












  • Did you understand or not?@BadamBaplan
    – cmi
    Dec 11 '18 at 4:56










  • $phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
    – cmi
    Dec 11 '18 at 5:08










  • No no unity@BadamBaplan
    – cmi
    Dec 11 '18 at 5:09










  • Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
    – Badam Baplan
    Dec 11 '18 at 5:31














1












1








1


2





I was reading Ring Homomorphism .



$phi : R to R'$ is a ring homomorphism and $e , e'$ are the unities of $R $ and $R'$ respectively.



I understood that $phi (e) $ may not be unity of $R'$.



I think the following statements are true.



( 1 ) $phi (e) $ is always unity of $phi (R) $ .



(2) If $phi $ is on to then $phi (e) = e'$



(3) If $phi $ is non trivial and $R'$ is a field then $phi (e) = e'$.



Can someone check if there is any mistake in my understanding?










share|cite|improve this question















I was reading Ring Homomorphism .



$phi : R to R'$ is a ring homomorphism and $e , e'$ are the unities of $R $ and $R'$ respectively.



I understood that $phi (e) $ may not be unity of $R'$.



I think the following statements are true.



( 1 ) $phi (e) $ is always unity of $phi (R) $ .



(2) If $phi $ is on to then $phi (e) = e'$



(3) If $phi $ is non trivial and $R'$ is a field then $phi (e) = e'$.



Can someone check if there is any mistake in my understanding?







abstract-algebra ring-theory field-theory






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share|cite|improve this question













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edited Dec 11 '18 at 4:41

























asked Dec 11 '18 at 4:24









cmi

1,003212




1,003212












  • $phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
    – cmi
    Dec 11 '18 at 4:47












  • Did you understand or not?@BadamBaplan
    – cmi
    Dec 11 '18 at 4:56










  • $phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
    – cmi
    Dec 11 '18 at 5:08










  • No no unity@BadamBaplan
    – cmi
    Dec 11 '18 at 5:09










  • Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
    – Badam Baplan
    Dec 11 '18 at 5:31


















  • $phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
    – cmi
    Dec 11 '18 at 4:47












  • Did you understand or not?@BadamBaplan
    – cmi
    Dec 11 '18 at 4:56










  • $phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
    – cmi
    Dec 11 '18 at 5:08










  • No no unity@BadamBaplan
    – cmi
    Dec 11 '18 at 5:09










  • Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
    – Badam Baplan
    Dec 11 '18 at 5:31
















$phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
– cmi
Dec 11 '18 at 4:47






$phi (R) $ is a ring with unity $phi (e)$@BadamBaplan
– cmi
Dec 11 '18 at 4:47














Did you understand or not?@BadamBaplan
– cmi
Dec 11 '18 at 4:56




Did you understand or not?@BadamBaplan
– cmi
Dec 11 '18 at 4:56












$phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
– cmi
Dec 11 '18 at 5:08




$phi (R)$ is always a subring and $phi(e)$ may not be the unity of $R'$. Proof or the first statement is very easy and see this math.stackexchange.com/questions/179842/… for the scond one.@BadamBaplan
– cmi
Dec 11 '18 at 5:08












No no unity@BadamBaplan
– cmi
Dec 11 '18 at 5:09




No no unity@BadamBaplan
– cmi
Dec 11 '18 at 5:09












Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
– Badam Baplan
Dec 11 '18 at 5:31




Yes $phi(R)$ is always a ring contained in $R$ with unit $phi(e)$. You seem to understand all of these things fine, so I'm not sure what you're looking for. Usually we require 'subrings' to contain the unity of their parent rings. I was just pointing out the connection that $phi(R)$ is a subring in that sense iff $phi(e) = e'$
– Badam Baplan
Dec 11 '18 at 5:31










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Yes your 3 statements are true and easy to prove ,I assume you can prove them .






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    Yes your 3 statements are true and easy to prove ,I assume you can prove them .






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      Yes your 3 statements are true and easy to prove ,I assume you can prove them .






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        Yes your 3 statements are true and easy to prove ,I assume you can prove them .






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        Yes your 3 statements are true and easy to prove ,I assume you can prove them .







        share|cite|improve this answer












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        answered Dec 11 '18 at 5:24









        StuartMN

        1,406410




        1,406410






























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