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Chern Character


The Chern character of a complex vector bundle is the rational cohomology class obtained by summing the exponentials of its formal Chern roots x_j,

 ch(E)=sum_(j)e^(x_j).

The degree-zero component is the rank, and the next components are ch_1=c_1, ch_2=(c_1^2-2c_2)/2, and ch_3=(c_1^3-3c_1c_2+3c_3)/6. It is additive on exact sequences and multiplicative on tensor products. On a smooth projective variety it also applies to coherent sheaves and derived-category objects through their Grothendieck classes. A real divisor twist uses ch^B(E)=e^(-B)ch(E).

These components enter the central charges of large-volume stability conditions. Unlike a Chern class, the full Chern character is additive under direct sum.


See also

Chern Class, Coherent Sheaf, Grothendieck Group, Large-Volume Stability Condition, Todd Class, Vector Bundle

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References

May, J. P. A Concise Course in Algebraic Topology. Chicago, IL: University of Chicago Press, 1999.

Cite this as:

Weisstein, Eric W. "Chern Character." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ChernCharacter.html

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