Can I Find A Map from a Module M to the kernel of a map p from M to M?











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I have a module homomorphism $p:Mrightarrow M$. I would like to find another module homomorphism $phi:Mrightarrow ker(p)$. Finding such a thing seems to be very challenging however. Is this possible? Note also that $p^2=p$.










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    I have a module homomorphism $p:Mrightarrow M$. I would like to find another module homomorphism $phi:Mrightarrow ker(p)$. Finding such a thing seems to be very challenging however. Is this possible? Note also that $p^2=p$.










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      I have a module homomorphism $p:Mrightarrow M$. I would like to find another module homomorphism $phi:Mrightarrow ker(p)$. Finding such a thing seems to be very challenging however. Is this possible? Note also that $p^2=p$.










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      I have a module homomorphism $p:Mrightarrow M$. I would like to find another module homomorphism $phi:Mrightarrow ker(p)$. Finding such a thing seems to be very challenging however. Is this possible? Note also that $p^2=p$.







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      edited Nov 25 at 20:16









      Ashwin Trisal

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      asked Nov 25 at 20:09









      V. P. Sworski

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          Let $phi=1_M-p$. Then $pcirc phi=p(1_M-p)=p-p^2=p-p=0$, so $phi:Mtoker p$. But there are many such maps $phi$; taking $phi$ to be the $0$ map would also define a map from $M$ to $ker p$.






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          • Ah, I see what I'm missing. I need the map to be surjective as well.
            – V. P. Sworski
            Nov 25 at 20:25











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          Let $phi=1_M-p$. Then $pcirc phi=p(1_M-p)=p-p^2=p-p=0$, so $phi:Mtoker p$. But there are many such maps $phi$; taking $phi$ to be the $0$ map would also define a map from $M$ to $ker p$.






          share|cite|improve this answer





















          • Ah, I see what I'm missing. I need the map to be surjective as well.
            – V. P. Sworski
            Nov 25 at 20:25















          up vote
          0
          down vote













          Let $phi=1_M-p$. Then $pcirc phi=p(1_M-p)=p-p^2=p-p=0$, so $phi:Mtoker p$. But there are many such maps $phi$; taking $phi$ to be the $0$ map would also define a map from $M$ to $ker p$.






          share|cite|improve this answer





















          • Ah, I see what I'm missing. I need the map to be surjective as well.
            – V. P. Sworski
            Nov 25 at 20:25













          up vote
          0
          down vote










          up vote
          0
          down vote









          Let $phi=1_M-p$. Then $pcirc phi=p(1_M-p)=p-p^2=p-p=0$, so $phi:Mtoker p$. But there are many such maps $phi$; taking $phi$ to be the $0$ map would also define a map from $M$ to $ker p$.






          share|cite|improve this answer












          Let $phi=1_M-p$. Then $pcirc phi=p(1_M-p)=p-p^2=p-p=0$, so $phi:Mtoker p$. But there are many such maps $phi$; taking $phi$ to be the $0$ map would also define a map from $M$ to $ker p$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Nov 25 at 20:15









          Ashwin Trisal

          1,1071515




          1,1071515












          • Ah, I see what I'm missing. I need the map to be surjective as well.
            – V. P. Sworski
            Nov 25 at 20:25


















          • Ah, I see what I'm missing. I need the map to be surjective as well.
            – V. P. Sworski
            Nov 25 at 20:25
















          Ah, I see what I'm missing. I need the map to be surjective as well.
          – V. P. Sworski
          Nov 25 at 20:25




          Ah, I see what I'm missing. I need the map to be surjective as well.
          – V. P. Sworski
          Nov 25 at 20:25


















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