On the definition of affine maps

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I am studying the Geometry book by Michèle Audin, let me recall her definition of an affine space.




A set $mathcalE$ is endowed with the structure of an affine space by the data of a vector space $E$ and a mapping $Theta$ that associates a vector of $E$ with any ordered pair of points in $mathcalE$,
$$
mathcalEtimesmathcalEto E \
(A,B)mapsto overrightarrowAB
$$
such that:



  • for any point $A$ of $mathcalE$, the partial map $Theta_A:Bmapsto overrightarrowAB$ is a bijection from $mathcalE$ to $E$;

  • for all points $A,B$ and $C$ in $mathcalE$, we have $overrightarrowAB=overrightarrowAC+overrightarrowCB$ (Chasles' relation).



Now her definition of an affine map.




Let $mathcalE$ and $mathcalF$ be two affine spaces directed
respectively by $E$ and $F$. A mapping
$phi:mathcalEtomathcalF$ is said to be affine if there
exists a point $O$ in $mathcalE$ and a linear mapping $f:Eto F$
such that $$ forall MinmathcalE, qquad
f(overrightarrowOM)=overrightarrowphi(O)phi(M).
$$




My question is the following. Could it be possible to define an affine map as a map $phi:mathcalEtomathcalF$ such that there exists a point $OinmathcalE$ and a linear map $f:Eto F$, which has the following compatibility condition with the map $Theta$:
$$
f(Theta_O(M)) = Theta_phi(O)(phi(M)) qquad forall MinmathcalE
$$
?



edit: after some thinking, I would also rephrase my question as: is it true that a map $phi:mathcalEtomathcalF$ is affine if and only if there exists a linear map $f:Eto F$ such that the following diagram:
$$
requireAMScd
beginCD
E @>f>> F \
@ATheta_OAA @ATheta_phiOAA \
mathcalE @>phi>> mathcalF
endCD
$$
commutes?







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    up vote
    0
    down vote

    favorite












    I am studying the Geometry book by Michèle Audin, let me recall her definition of an affine space.




    A set $mathcalE$ is endowed with the structure of an affine space by the data of a vector space $E$ and a mapping $Theta$ that associates a vector of $E$ with any ordered pair of points in $mathcalE$,
    $$
    mathcalEtimesmathcalEto E \
    (A,B)mapsto overrightarrowAB
    $$
    such that:



    • for any point $A$ of $mathcalE$, the partial map $Theta_A:Bmapsto overrightarrowAB$ is a bijection from $mathcalE$ to $E$;

    • for all points $A,B$ and $C$ in $mathcalE$, we have $overrightarrowAB=overrightarrowAC+overrightarrowCB$ (Chasles' relation).



    Now her definition of an affine map.




    Let $mathcalE$ and $mathcalF$ be two affine spaces directed
    respectively by $E$ and $F$. A mapping
    $phi:mathcalEtomathcalF$ is said to be affine if there
    exists a point $O$ in $mathcalE$ and a linear mapping $f:Eto F$
    such that $$ forall MinmathcalE, qquad
    f(overrightarrowOM)=overrightarrowphi(O)phi(M).
    $$




    My question is the following. Could it be possible to define an affine map as a map $phi:mathcalEtomathcalF$ such that there exists a point $OinmathcalE$ and a linear map $f:Eto F$, which has the following compatibility condition with the map $Theta$:
    $$
    f(Theta_O(M)) = Theta_phi(O)(phi(M)) qquad forall MinmathcalE
    $$
    ?



    edit: after some thinking, I would also rephrase my question as: is it true that a map $phi:mathcalEtomathcalF$ is affine if and only if there exists a linear map $f:Eto F$ such that the following diagram:
    $$
    requireAMScd
    beginCD
    E @>f>> F \
    @ATheta_OAA @ATheta_phiOAA \
    mathcalE @>phi>> mathcalF
    endCD
    $$
    commutes?







    share|cite|improve this question
























      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      I am studying the Geometry book by Michèle Audin, let me recall her definition of an affine space.




      A set $mathcalE$ is endowed with the structure of an affine space by the data of a vector space $E$ and a mapping $Theta$ that associates a vector of $E$ with any ordered pair of points in $mathcalE$,
      $$
      mathcalEtimesmathcalEto E \
      (A,B)mapsto overrightarrowAB
      $$
      such that:



      • for any point $A$ of $mathcalE$, the partial map $Theta_A:Bmapsto overrightarrowAB$ is a bijection from $mathcalE$ to $E$;

      • for all points $A,B$ and $C$ in $mathcalE$, we have $overrightarrowAB=overrightarrowAC+overrightarrowCB$ (Chasles' relation).



      Now her definition of an affine map.




      Let $mathcalE$ and $mathcalF$ be two affine spaces directed
      respectively by $E$ and $F$. A mapping
      $phi:mathcalEtomathcalF$ is said to be affine if there
      exists a point $O$ in $mathcalE$ and a linear mapping $f:Eto F$
      such that $$ forall MinmathcalE, qquad
      f(overrightarrowOM)=overrightarrowphi(O)phi(M).
      $$




      My question is the following. Could it be possible to define an affine map as a map $phi:mathcalEtomathcalF$ such that there exists a point $OinmathcalE$ and a linear map $f:Eto F$, which has the following compatibility condition with the map $Theta$:
      $$
      f(Theta_O(M)) = Theta_phi(O)(phi(M)) qquad forall MinmathcalE
      $$
      ?



      edit: after some thinking, I would also rephrase my question as: is it true that a map $phi:mathcalEtomathcalF$ is affine if and only if there exists a linear map $f:Eto F$ such that the following diagram:
      $$
      requireAMScd
      beginCD
      E @>f>> F \
      @ATheta_OAA @ATheta_phiOAA \
      mathcalE @>phi>> mathcalF
      endCD
      $$
      commutes?







      share|cite|improve this question














      I am studying the Geometry book by Michèle Audin, let me recall her definition of an affine space.




      A set $mathcalE$ is endowed with the structure of an affine space by the data of a vector space $E$ and a mapping $Theta$ that associates a vector of $E$ with any ordered pair of points in $mathcalE$,
      $$
      mathcalEtimesmathcalEto E \
      (A,B)mapsto overrightarrowAB
      $$
      such that:



      • for any point $A$ of $mathcalE$, the partial map $Theta_A:Bmapsto overrightarrowAB$ is a bijection from $mathcalE$ to $E$;

      • for all points $A,B$ and $C$ in $mathcalE$, we have $overrightarrowAB=overrightarrowAC+overrightarrowCB$ (Chasles' relation).



      Now her definition of an affine map.




      Let $mathcalE$ and $mathcalF$ be two affine spaces directed
      respectively by $E$ and $F$. A mapping
      $phi:mathcalEtomathcalF$ is said to be affine if there
      exists a point $O$ in $mathcalE$ and a linear mapping $f:Eto F$
      such that $$ forall MinmathcalE, qquad
      f(overrightarrowOM)=overrightarrowphi(O)phi(M).
      $$




      My question is the following. Could it be possible to define an affine map as a map $phi:mathcalEtomathcalF$ such that there exists a point $OinmathcalE$ and a linear map $f:Eto F$, which has the following compatibility condition with the map $Theta$:
      $$
      f(Theta_O(M)) = Theta_phi(O)(phi(M)) qquad forall MinmathcalE
      $$
      ?



      edit: after some thinking, I would also rephrase my question as: is it true that a map $phi:mathcalEtomathcalF$ is affine if and only if there exists a linear map $f:Eto F$ such that the following diagram:
      $$
      requireAMScd
      beginCD
      E @>f>> F \
      @ATheta_OAA @ATheta_phiOAA \
      mathcalE @>phi>> mathcalF
      endCD
      $$
      commutes?









      share|cite|improve this question













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      edited Aug 21 at 10:31

























      asked Aug 21 at 10:11









      J. D.

      1858




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