Heights
Consider line bundles
with admissible adelic metrics. Let be a subvariety
of of dimension and
invertible meromorphic sections of
whose divisors hace no common intersection point on .
For any , we have recalled in Sections 1.2,
1.2 and 1.3
the definitions of the local height pairing
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where the index indicates the corresponding place of .
The global height is the sum, over all , of these
local heights :
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It inherits from the local heights their multilinear symmetric character.
Let us replace by another invertible meromorphic section .
Then,
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In particular, if is a point , then
is the Dirac mass at and
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Let us observe that it is independent
on the choice of the chosen meromorphic section ,
provided it is regular at .
Any other section has the form , for some invertible
meromorphic function on . Then,
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since, by the product formula, the second term vanishes.
By induction on the dimension of , and using the commutativity
of the local height pairings, it follows that
the global height only depends on the metrized line bundles,
and not on the actual chosen sections .
We denote it by
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Again, it is multilinear symmetric in the metrized line bundles . By the same argument, it only depends on their
isomorphism classes in .
It satisfies a projection formula : for any morphism
and any -dimensional subvariety of ,
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where the cycle is defined as
if and have the same dimension,
so that is generically finite,
of some degree . If and
don’t have the same dimension, one sets .