Smooth structures on noncompact 6-manifolds











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Does a noncompact, simply connected 6-manifold have a unique smooth structure? Maybe with more assumptions like having torsion-free homology and being spin?



Note that in the compact case C.T.C. Wall showed that this is true. Can counterexamples be constructed with exotic $mathbb{R}^4$s, e.g. $Xtimes S^2$ with $X$ an exotic $mathbb{R}^4$?



Any related references would be appreciated.










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  • For compact part Wall proved that if torsion vanish then it is true
    – Anubhav Mukherjee
    Nov 15 at 16:54






  • 1




    He also assumed the manifold is spin, as I stated above.
    – srp
    Nov 15 at 18:10










  • Yeah and $w_2=0$.
    – Anubhav Mukherjee
    Nov 15 at 18:18










  • @AnubhavMukherjee That is what spin means.
    – Mike Miller
    Nov 15 at 18:30










  • @MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
    – Anubhav Mukherjee
    Nov 15 at 18:31















up vote
4
down vote

favorite
1












Does a noncompact, simply connected 6-manifold have a unique smooth structure? Maybe with more assumptions like having torsion-free homology and being spin?



Note that in the compact case C.T.C. Wall showed that this is true. Can counterexamples be constructed with exotic $mathbb{R}^4$s, e.g. $Xtimes S^2$ with $X$ an exotic $mathbb{R}^4$?



Any related references would be appreciated.










share|cite|improve this question
























  • For compact part Wall proved that if torsion vanish then it is true
    – Anubhav Mukherjee
    Nov 15 at 16:54






  • 1




    He also assumed the manifold is spin, as I stated above.
    – srp
    Nov 15 at 18:10










  • Yeah and $w_2=0$.
    – Anubhav Mukherjee
    Nov 15 at 18:18










  • @AnubhavMukherjee That is what spin means.
    – Mike Miller
    Nov 15 at 18:30










  • @MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
    – Anubhav Mukherjee
    Nov 15 at 18:31













up vote
4
down vote

favorite
1









up vote
4
down vote

favorite
1






1





Does a noncompact, simply connected 6-manifold have a unique smooth structure? Maybe with more assumptions like having torsion-free homology and being spin?



Note that in the compact case C.T.C. Wall showed that this is true. Can counterexamples be constructed with exotic $mathbb{R}^4$s, e.g. $Xtimes S^2$ with $X$ an exotic $mathbb{R}^4$?



Any related references would be appreciated.










share|cite|improve this question















Does a noncompact, simply connected 6-manifold have a unique smooth structure? Maybe with more assumptions like having torsion-free homology and being spin?



Note that in the compact case C.T.C. Wall showed that this is true. Can counterexamples be constructed with exotic $mathbb{R}^4$s, e.g. $Xtimes S^2$ with $X$ an exotic $mathbb{R}^4$?



Any related references would be appreciated.







differential-geometry algebraic-topology differential-topology






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share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 15 at 3:10

























asked Nov 15 at 2:59









srp

1827




1827












  • For compact part Wall proved that if torsion vanish then it is true
    – Anubhav Mukherjee
    Nov 15 at 16:54






  • 1




    He also assumed the manifold is spin, as I stated above.
    – srp
    Nov 15 at 18:10










  • Yeah and $w_2=0$.
    – Anubhav Mukherjee
    Nov 15 at 18:18










  • @AnubhavMukherjee That is what spin means.
    – Mike Miller
    Nov 15 at 18:30










  • @MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
    – Anubhav Mukherjee
    Nov 15 at 18:31


















  • For compact part Wall proved that if torsion vanish then it is true
    – Anubhav Mukherjee
    Nov 15 at 16:54






  • 1




    He also assumed the manifold is spin, as I stated above.
    – srp
    Nov 15 at 18:10










  • Yeah and $w_2=0$.
    – Anubhav Mukherjee
    Nov 15 at 18:18










  • @AnubhavMukherjee That is what spin means.
    – Mike Miller
    Nov 15 at 18:30










  • @MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
    – Anubhav Mukherjee
    Nov 15 at 18:31
















For compact part Wall proved that if torsion vanish then it is true
– Anubhav Mukherjee
Nov 15 at 16:54




For compact part Wall proved that if torsion vanish then it is true
– Anubhav Mukherjee
Nov 15 at 16:54




1




1




He also assumed the manifold is spin, as I stated above.
– srp
Nov 15 at 18:10




He also assumed the manifold is spin, as I stated above.
– srp
Nov 15 at 18:10












Yeah and $w_2=0$.
– Anubhav Mukherjee
Nov 15 at 18:18




Yeah and $w_2=0$.
– Anubhav Mukherjee
Nov 15 at 18:18












@AnubhavMukherjee That is what spin means.
– Mike Miller
Nov 15 at 18:30




@AnubhavMukherjee That is what spin means.
– Mike Miller
Nov 15 at 18:30












@MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
– Anubhav Mukherjee
Nov 15 at 18:31




@MikeMiller In my first comment I forgot to mention $w_2$...and I know that it is the meaning of spin :P
– Anubhav Mukherjee
Nov 15 at 18:31















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