Geometric way to view affine connection and parallel transport.












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Given a parametrized curve $gamma$ on a manifold $M$ with metric $g$ and some affine connection on it, we can transport vectors of tangent spaces $T_{p} M$ and $T_{q}M$ to each other (when $p, q in gamma$). Then scalar product of vectors (w.r.t. $g$) is preserved under this transport and we can see it algebraically just because of Leibniz rule.



The question is: Can we see the fact that scalar product is preserved in a more geometric way?



Any notes on geodesics will also be appreciated.










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    $begingroup$


    Given a parametrized curve $gamma$ on a manifold $M$ with metric $g$ and some affine connection on it, we can transport vectors of tangent spaces $T_{p} M$ and $T_{q}M$ to each other (when $p, q in gamma$). Then scalar product of vectors (w.r.t. $g$) is preserved under this transport and we can see it algebraically just because of Leibniz rule.



    The question is: Can we see the fact that scalar product is preserved in a more geometric way?



    Any notes on geodesics will also be appreciated.










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      Given a parametrized curve $gamma$ on a manifold $M$ with metric $g$ and some affine connection on it, we can transport vectors of tangent spaces $T_{p} M$ and $T_{q}M$ to each other (when $p, q in gamma$). Then scalar product of vectors (w.r.t. $g$) is preserved under this transport and we can see it algebraically just because of Leibniz rule.



      The question is: Can we see the fact that scalar product is preserved in a more geometric way?



      Any notes on geodesics will also be appreciated.










      share|cite|improve this question









      $endgroup$




      Given a parametrized curve $gamma$ on a manifold $M$ with metric $g$ and some affine connection on it, we can transport vectors of tangent spaces $T_{p} M$ and $T_{q}M$ to each other (when $p, q in gamma$). Then scalar product of vectors (w.r.t. $g$) is preserved under this transport and we can see it algebraically just because of Leibniz rule.



      The question is: Can we see the fact that scalar product is preserved in a more geometric way?



      Any notes on geodesics will also be appreciated.







      riemannian-geometry smooth-manifolds curves connections






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      asked Jan 21 at 23:11









      Rybin DmitryRybin Dmitry

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          $begingroup$

          Not all connections preserve the scalar product (the "metric"). We need to impose this condition - if, furthermore, we also ask the connection to be torsion-free, then we get the Levi-Civita connection, which is likely the one you have in mind.



          One may consider $M$ as a submanifold in some ${mathbb R}^n$ and assume $X, Y$ are two vector fields on $M$. Then the Levi-Civita connection (at $xin M$) $nabla_XY$ is just taking the ordinary Euclidean directional derivative for $Y$ in the $X$ direction, then project to the tangent space $T_x M$. Euclidean derivative preserves the scalar product (by calculus), and this is still true after projecting to $T_x M$.






          share|cite|improve this answer









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            $begingroup$

            Not all connections preserve the scalar product (the "metric"). We need to impose this condition - if, furthermore, we also ask the connection to be torsion-free, then we get the Levi-Civita connection, which is likely the one you have in mind.



            One may consider $M$ as a submanifold in some ${mathbb R}^n$ and assume $X, Y$ are two vector fields on $M$. Then the Levi-Civita connection (at $xin M$) $nabla_XY$ is just taking the ordinary Euclidean directional derivative for $Y$ in the $X$ direction, then project to the tangent space $T_x M$. Euclidean derivative preserves the scalar product (by calculus), and this is still true after projecting to $T_x M$.






            share|cite|improve this answer









            $endgroup$


















              3












              $begingroup$

              Not all connections preserve the scalar product (the "metric"). We need to impose this condition - if, furthermore, we also ask the connection to be torsion-free, then we get the Levi-Civita connection, which is likely the one you have in mind.



              One may consider $M$ as a submanifold in some ${mathbb R}^n$ and assume $X, Y$ are two vector fields on $M$. Then the Levi-Civita connection (at $xin M$) $nabla_XY$ is just taking the ordinary Euclidean directional derivative for $Y$ in the $X$ direction, then project to the tangent space $T_x M$. Euclidean derivative preserves the scalar product (by calculus), and this is still true after projecting to $T_x M$.






              share|cite|improve this answer









              $endgroup$
















                3












                3








                3





                $begingroup$

                Not all connections preserve the scalar product (the "metric"). We need to impose this condition - if, furthermore, we also ask the connection to be torsion-free, then we get the Levi-Civita connection, which is likely the one you have in mind.



                One may consider $M$ as a submanifold in some ${mathbb R}^n$ and assume $X, Y$ are two vector fields on $M$. Then the Levi-Civita connection (at $xin M$) $nabla_XY$ is just taking the ordinary Euclidean directional derivative for $Y$ in the $X$ direction, then project to the tangent space $T_x M$. Euclidean derivative preserves the scalar product (by calculus), and this is still true after projecting to $T_x M$.






                share|cite|improve this answer









                $endgroup$



                Not all connections preserve the scalar product (the "metric"). We need to impose this condition - if, furthermore, we also ask the connection to be torsion-free, then we get the Levi-Civita connection, which is likely the one you have in mind.



                One may consider $M$ as a submanifold in some ${mathbb R}^n$ and assume $X, Y$ are two vector fields on $M$. Then the Levi-Civita connection (at $xin M$) $nabla_XY$ is just taking the ordinary Euclidean directional derivative for $Y$ in the $X$ direction, then project to the tangent space $T_x M$. Euclidean derivative preserves the scalar product (by calculus), and this is still true after projecting to $T_x M$.







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 24 at 17:26









                Yu DingYu Ding

                3435




                3435






























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