Why are Stein manifolds/spaces the analog of affine varieties/schemes in algebraic geometry?Stein Manifolds...



Why are Stein manifolds/spaces the analog of affine varieties/schemes in algebraic geometry?


Stein Manifolds and Affine VarietiesAre all parametrizations via polynomials algebraic varieties?Are all manifolds affine?Why can I divide an affine variety by the action of the general linear group?Chern classes of ideal sheaf of an analytic subsetAlgebraic varieties in “mixed” affine spacesAlgebraic spaces which are automatically schemes“Affine” algebraic spacesKahler manifolds and algebraic varietiesThe cone of curves of complex projective manifolds with an algebraic torus action













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I presume this is a GAGA-style result, but I cannot find a reference.










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    9












    $begingroup$


    I presume this is a GAGA-style result, but I cannot find a reference.










    share|cite|improve this question









    $endgroup$















      9












      9








      9





      $begingroup$


      I presume this is a GAGA-style result, but I cannot find a reference.










      share|cite|improve this question









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      I presume this is a GAGA-style result, but I cannot find a reference.







      ag.algebraic-geometry reference-request complex-geometry






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      asked 10 hours ago









      John RachedJohn Rached

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          $begingroup$

          Also like affine varieties, we have:




          Theorem. A complex manifold is Stein if and only if it embeds into some $mathbb{C}^N$ as a closed complex submanifold.




          For the "only if" direction, see Hörmander, An Introduction to Complex Analysis in Several variables, Theorem 5.3.9. For the converse, use Cartan B mentioned above. (Added: I don't mean to be too pedantic, but Cartan says that $X$ is Stein iff sheaf cohomology vanishes for coherent analytic coefficients; it is certainly not true otherwise.)






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            12












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            I believe the reason for this is Cartan's 'Theorem B': for a Stein manifold $mathrm{X}$ sheaf cohomology vanishes, $mathrm{H}^n(mathrm{X},-)=0$ for $ngeqslant 1$, and this property characterises Stein manifolds among complex manifolds. In the same way affine schemes are characterised among (nice) schemes by cohomology vanishing (this is a theorem of Serre). This comes up in the proof of the cohomological comparison result which is part of GAGA, see for example SGA 1, Exposé XII.






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              2 Answers
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              14












              $begingroup$

              Also like affine varieties, we have:




              Theorem. A complex manifold is Stein if and only if it embeds into some $mathbb{C}^N$ as a closed complex submanifold.




              For the "only if" direction, see Hörmander, An Introduction to Complex Analysis in Several variables, Theorem 5.3.9. For the converse, use Cartan B mentioned above. (Added: I don't mean to be too pedantic, but Cartan says that $X$ is Stein iff sheaf cohomology vanishes for coherent analytic coefficients; it is certainly not true otherwise.)






              share|cite|improve this answer











              $endgroup$


















                14












                $begingroup$

                Also like affine varieties, we have:




                Theorem. A complex manifold is Stein if and only if it embeds into some $mathbb{C}^N$ as a closed complex submanifold.




                For the "only if" direction, see Hörmander, An Introduction to Complex Analysis in Several variables, Theorem 5.3.9. For the converse, use Cartan B mentioned above. (Added: I don't mean to be too pedantic, but Cartan says that $X$ is Stein iff sheaf cohomology vanishes for coherent analytic coefficients; it is certainly not true otherwise.)






                share|cite|improve this answer











                $endgroup$
















                  14












                  14








                  14





                  $begingroup$

                  Also like affine varieties, we have:




                  Theorem. A complex manifold is Stein if and only if it embeds into some $mathbb{C}^N$ as a closed complex submanifold.




                  For the "only if" direction, see Hörmander, An Introduction to Complex Analysis in Several variables, Theorem 5.3.9. For the converse, use Cartan B mentioned above. (Added: I don't mean to be too pedantic, but Cartan says that $X$ is Stein iff sheaf cohomology vanishes for coherent analytic coefficients; it is certainly not true otherwise.)






                  share|cite|improve this answer











                  $endgroup$



                  Also like affine varieties, we have:




                  Theorem. A complex manifold is Stein if and only if it embeds into some $mathbb{C}^N$ as a closed complex submanifold.




                  For the "only if" direction, see Hörmander, An Introduction to Complex Analysis in Several variables, Theorem 5.3.9. For the converse, use Cartan B mentioned above. (Added: I don't mean to be too pedantic, but Cartan says that $X$ is Stein iff sheaf cohomology vanishes for coherent analytic coefficients; it is certainly not true otherwise.)







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited 7 hours ago

























                  answered 9 hours ago









                  Donu ArapuraDonu Arapura

                  25.8k268128




                  25.8k268128























                      12












                      $begingroup$

                      I believe the reason for this is Cartan's 'Theorem B': for a Stein manifold $mathrm{X}$ sheaf cohomology vanishes, $mathrm{H}^n(mathrm{X},-)=0$ for $ngeqslant 1$, and this property characterises Stein manifolds among complex manifolds. In the same way affine schemes are characterised among (nice) schemes by cohomology vanishing (this is a theorem of Serre). This comes up in the proof of the cohomological comparison result which is part of GAGA, see for example SGA 1, Exposé XII.






                      share|cite|improve this answer









                      $endgroup$


















                        12












                        $begingroup$

                        I believe the reason for this is Cartan's 'Theorem B': for a Stein manifold $mathrm{X}$ sheaf cohomology vanishes, $mathrm{H}^n(mathrm{X},-)=0$ for $ngeqslant 1$, and this property characterises Stein manifolds among complex manifolds. In the same way affine schemes are characterised among (nice) schemes by cohomology vanishing (this is a theorem of Serre). This comes up in the proof of the cohomological comparison result which is part of GAGA, see for example SGA 1, Exposé XII.






                        share|cite|improve this answer









                        $endgroup$
















                          12












                          12








                          12





                          $begingroup$

                          I believe the reason for this is Cartan's 'Theorem B': for a Stein manifold $mathrm{X}$ sheaf cohomology vanishes, $mathrm{H}^n(mathrm{X},-)=0$ for $ngeqslant 1$, and this property characterises Stein manifolds among complex manifolds. In the same way affine schemes are characterised among (nice) schemes by cohomology vanishing (this is a theorem of Serre). This comes up in the proof of the cohomological comparison result which is part of GAGA, see for example SGA 1, Exposé XII.






                          share|cite|improve this answer









                          $endgroup$



                          I believe the reason for this is Cartan's 'Theorem B': for a Stein manifold $mathrm{X}$ sheaf cohomology vanishes, $mathrm{H}^n(mathrm{X},-)=0$ for $ngeqslant 1$, and this property characterises Stein manifolds among complex manifolds. In the same way affine schemes are characterised among (nice) schemes by cohomology vanishing (this is a theorem of Serre). This comes up in the proof of the cohomological comparison result which is part of GAGA, see for example SGA 1, Exposé XII.







                          share|cite|improve this answer












                          share|cite|improve this answer



                          share|cite|improve this answer










                          answered 10 hours ago









                          Mere ScribeMere Scribe

                          1,0362820




                          1,0362820






























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