Orientation and line bundle











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I'm stuck on the following problem:




Given $X$ a manifold and $L$ a line bundle over $X$, considerer $Z$
the null-section and define $Or(L) := (L setminus Z) ,
/,mathbb{R}_+^*$
. Show that the trivialisation $L_{|U} simeq U times mathbb{R}$ induces a homeomorphism $pi^{-1}(U) simeq U
times Or(mathbb{R})$
(where $Or(mathbb{R})$ is nothing more that
${pm 1 }$), where $pi : L to X$ is the canonical
projection. Conclude that $Or(L)$ is given a unique smooth manifold
structure such that $eta : Or(L) to X$ is a local diffeomorphism.




Here, $eta$ is the continuous surjection induced by $pi$. Indeed, $pi$ is trivially constant over the fibers of the quotient map, so that it goes down continuously to the said quotient $Or(L)$.



Thanks for the help!










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  • Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
    – Ted Shifrin
    6 hours ago















up vote
0
down vote

favorite












I'm stuck on the following problem:




Given $X$ a manifold and $L$ a line bundle over $X$, considerer $Z$
the null-section and define $Or(L) := (L setminus Z) ,
/,mathbb{R}_+^*$
. Show that the trivialisation $L_{|U} simeq U times mathbb{R}$ induces a homeomorphism $pi^{-1}(U) simeq U
times Or(mathbb{R})$
(where $Or(mathbb{R})$ is nothing more that
${pm 1 }$), where $pi : L to X$ is the canonical
projection. Conclude that $Or(L)$ is given a unique smooth manifold
structure such that $eta : Or(L) to X$ is a local diffeomorphism.




Here, $eta$ is the continuous surjection induced by $pi$. Indeed, $pi$ is trivially constant over the fibers of the quotient map, so that it goes down continuously to the said quotient $Or(L)$.



Thanks for the help!










share|cite|improve this question
























  • Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
    – Ted Shifrin
    6 hours ago













up vote
0
down vote

favorite









up vote
0
down vote

favorite











I'm stuck on the following problem:




Given $X$ a manifold and $L$ a line bundle over $X$, considerer $Z$
the null-section and define $Or(L) := (L setminus Z) ,
/,mathbb{R}_+^*$
. Show that the trivialisation $L_{|U} simeq U times mathbb{R}$ induces a homeomorphism $pi^{-1}(U) simeq U
times Or(mathbb{R})$
(where $Or(mathbb{R})$ is nothing more that
${pm 1 }$), where $pi : L to X$ is the canonical
projection. Conclude that $Or(L)$ is given a unique smooth manifold
structure such that $eta : Or(L) to X$ is a local diffeomorphism.




Here, $eta$ is the continuous surjection induced by $pi$. Indeed, $pi$ is trivially constant over the fibers of the quotient map, so that it goes down continuously to the said quotient $Or(L)$.



Thanks for the help!










share|cite|improve this question















I'm stuck on the following problem:




Given $X$ a manifold and $L$ a line bundle over $X$, considerer $Z$
the null-section and define $Or(L) := (L setminus Z) ,
/,mathbb{R}_+^*$
. Show that the trivialisation $L_{|U} simeq U times mathbb{R}$ induces a homeomorphism $pi^{-1}(U) simeq U
times Or(mathbb{R})$
(where $Or(mathbb{R})$ is nothing more that
${pm 1 }$), where $pi : L to X$ is the canonical
projection. Conclude that $Or(L)$ is given a unique smooth manifold
structure such that $eta : Or(L) to X$ is a local diffeomorphism.




Here, $eta$ is the continuous surjection induced by $pi$. Indeed, $pi$ is trivially constant over the fibers of the quotient map, so that it goes down continuously to the said quotient $Or(L)$.



Thanks for the help!







differential-geometry






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edited 15 hours ago

























asked 17 hours ago









Hermès

1,799612




1,799612












  • Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
    – Ted Shifrin
    6 hours ago


















  • Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
    – Ted Shifrin
    6 hours ago
















Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
– Ted Shifrin
6 hours ago




Something's wrong in the statement here. You mean that $eta^{-1}(U)cong Utimes text{Or}(Bbb R)$?
– Ted Shifrin
6 hours ago















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