De Rham cohomology of $mathbb{RP^n}$











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I have to calculate the De Rham cohomology of $mathbb{RP^n}$ using the Mayer-Vietoris sequence.



I first started by considering $mathbb{RP^n}=S^n/sim $ where $sim$ is the antipodal identification. Then I wrote $mathbb{RP^n}$ as the union of the sets



$U=S^n- {(0,...0,1)}$



and



$V=S^n- {(1,0,...,0)}$



But when I start using Mayer-Vietoris sequence I don't know how to proceed. Do I need to calculate it by induction on the order of the cohomology? Have you any hints or references in which it is solved?



Thank you.










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  • 1




    Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
    – DKS
    Nov 16 at 18:20










  • @DKS These are precisely the steps I can't do. Is there a place where it's explained?
    – Phi_24
    Nov 17 at 13:28















up vote
1
down vote

favorite












I have to calculate the De Rham cohomology of $mathbb{RP^n}$ using the Mayer-Vietoris sequence.



I first started by considering $mathbb{RP^n}=S^n/sim $ where $sim$ is the antipodal identification. Then I wrote $mathbb{RP^n}$ as the union of the sets



$U=S^n- {(0,...0,1)}$



and



$V=S^n- {(1,0,...,0)}$



But when I start using Mayer-Vietoris sequence I don't know how to proceed. Do I need to calculate it by induction on the order of the cohomology? Have you any hints or references in which it is solved?



Thank you.










share|cite|improve this question




















  • 1




    Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
    – DKS
    Nov 16 at 18:20










  • @DKS These are precisely the steps I can't do. Is there a place where it's explained?
    – Phi_24
    Nov 17 at 13:28













up vote
1
down vote

favorite









up vote
1
down vote

favorite











I have to calculate the De Rham cohomology of $mathbb{RP^n}$ using the Mayer-Vietoris sequence.



I first started by considering $mathbb{RP^n}=S^n/sim $ where $sim$ is the antipodal identification. Then I wrote $mathbb{RP^n}$ as the union of the sets



$U=S^n- {(0,...0,1)}$



and



$V=S^n- {(1,0,...,0)}$



But when I start using Mayer-Vietoris sequence I don't know how to proceed. Do I need to calculate it by induction on the order of the cohomology? Have you any hints or references in which it is solved?



Thank you.










share|cite|improve this question















I have to calculate the De Rham cohomology of $mathbb{RP^n}$ using the Mayer-Vietoris sequence.



I first started by considering $mathbb{RP^n}=S^n/sim $ where $sim$ is the antipodal identification. Then I wrote $mathbb{RP^n}$ as the union of the sets



$U=S^n- {(0,...0,1)}$



and



$V=S^n- {(1,0,...,0)}$



But when I start using Mayer-Vietoris sequence I don't know how to proceed. Do I need to calculate it by induction on the order of the cohomology? Have you any hints or references in which it is solved?



Thank you.







algebraic-topology projective-space de-rham-cohomology






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Nov 16 at 19:38









KReiser

9,08711335




9,08711335










asked Nov 16 at 17:44









Phi_24

1248




1248








  • 1




    Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
    – DKS
    Nov 16 at 18:20










  • @DKS These are precisely the steps I can't do. Is there a place where it's explained?
    – Phi_24
    Nov 17 at 13:28














  • 1




    Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
    – DKS
    Nov 16 at 18:20










  • @DKS These are precisely the steps I can't do. Is there a place where it's explained?
    – Phi_24
    Nov 17 at 13:28








1




1




Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
– DKS
Nov 16 at 18:20




Well you should try to first figure out the cohomology of $U$, $V$, and $U cap V$. Then you should try to figure out what the induced maps on cohomology are. Then you can hope that can exactness will help to figure out the cohomology groups.
– DKS
Nov 16 at 18:20












@DKS These are precisely the steps I can't do. Is there a place where it's explained?
– Phi_24
Nov 17 at 13:28




@DKS These are precisely the steps I can't do. Is there a place where it's explained?
– Phi_24
Nov 17 at 13:28















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