Why the Hamiltonian is constant along the integral curves of the hamiltonian vector field?












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Let $H$ the Hamiltonian of a system and $gamma $ an integral curve of the Hamiltonian vector field, i.e. if $gamma (t)=(q(t),p(t))$ and $H(p,q)$ is the Hamiltonian, then $$begin{cases} dot p=-H_q\ dot q= H_pend{cases}.$$



In wikipedia the say that $H$ is constant along $gamma $. Why is this true ? i.e. why $H(gamma (t))$ is constant ?










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    1












    $begingroup$


    Let $H$ the Hamiltonian of a system and $gamma $ an integral curve of the Hamiltonian vector field, i.e. if $gamma (t)=(q(t),p(t))$ and $H(p,q)$ is the Hamiltonian, then $$begin{cases} dot p=-H_q\ dot q= H_pend{cases}.$$



    In wikipedia the say that $H$ is constant along $gamma $. Why is this true ? i.e. why $H(gamma (t))$ is constant ?










    share|cite|improve this question









    $endgroup$















      1












      1








      1





      $begingroup$


      Let $H$ the Hamiltonian of a system and $gamma $ an integral curve of the Hamiltonian vector field, i.e. if $gamma (t)=(q(t),p(t))$ and $H(p,q)$ is the Hamiltonian, then $$begin{cases} dot p=-H_q\ dot q= H_pend{cases}.$$



      In wikipedia the say that $H$ is constant along $gamma $. Why is this true ? i.e. why $H(gamma (t))$ is constant ?










      share|cite|improve this question









      $endgroup$




      Let $H$ the Hamiltonian of a system and $gamma $ an integral curve of the Hamiltonian vector field, i.e. if $gamma (t)=(q(t),p(t))$ and $H(p,q)$ is the Hamiltonian, then $$begin{cases} dot p=-H_q\ dot q= H_pend{cases}.$$



      In wikipedia the say that $H$ is constant along $gamma $. Why is this true ? i.e. why $H(gamma (t))$ is constant ?







      symplectic-geometry






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      asked Jan 11 at 15:53









      user623855user623855

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          1 Answer
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          2












          $begingroup$

          For $H(p,q,t) = H(p(t),q(t))$ think that



          $$
          frac{d}{dt}H(p(t),q(t)) = H_p dot p + H_q dot q
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
            $endgroup$
            – user623855
            Jan 11 at 16:03











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          1 Answer
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          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

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          2












          $begingroup$

          For $H(p,q,t) = H(p(t),q(t))$ think that



          $$
          frac{d}{dt}H(p(t),q(t)) = H_p dot p + H_q dot q
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
            $endgroup$
            – user623855
            Jan 11 at 16:03
















          2












          $begingroup$

          For $H(p,q,t) = H(p(t),q(t))$ think that



          $$
          frac{d}{dt}H(p(t),q(t)) = H_p dot p + H_q dot q
          $$






          share|cite|improve this answer











          $endgroup$













          • $begingroup$
            Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
            $endgroup$
            – user623855
            Jan 11 at 16:03














          2












          2








          2





          $begingroup$

          For $H(p,q,t) = H(p(t),q(t))$ think that



          $$
          frac{d}{dt}H(p(t),q(t)) = H_p dot p + H_q dot q
          $$






          share|cite|improve this answer











          $endgroup$



          For $H(p,q,t) = H(p(t),q(t))$ think that



          $$
          frac{d}{dt}H(p(t),q(t)) = H_p dot p + H_q dot q
          $$







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Jan 11 at 16:11

























          answered Jan 11 at 16:01









          CesareoCesareo

          8,6793516




          8,6793516












          • $begingroup$
            Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
            $endgroup$
            – user623855
            Jan 11 at 16:03


















          • $begingroup$
            Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
            $endgroup$
            – user623855
            Jan 11 at 16:03
















          $begingroup$
          Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
          $endgroup$
          – user623855
          Jan 11 at 16:03




          $begingroup$
          Indeed, it make sense :) But I'm confusion with wikipedia notation, what they mean by $<dH,dot gamma >=0$ ? Because $omega $ is not a scalar product (is not a riemann manifold)
          $endgroup$
          – user623855
          Jan 11 at 16:03


















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