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# ch -- Chern character of the Hodge bundle

- Usage:
    `ch_a`
- Inputs:
  - a, an integer
- Outputs:
  - a ring element

## Description

This is an element in the ring created by hodgeRing. It is the $a$-th graded part of the Chern character of the Hodge bundle on ${\bar M}_{g,n}$.

## Examples

Here is a simple example which calculates $\int_{{\bar M}_{1,1}} ch_1$.

    i1 : R = hodgeRing (1, 1);

    i2 : ch_1

    o2 = ch
           1

    o2 : R

    i3 : integral(1, 1, ch_1)
    warning: clearing value of symbol tempCh to allow access to subscripted variables based on it
           : debug with expression   debug 1257   or with command line option   --debug 1257

          1
    o3 = --
         24

    o3 : R

## See also

- HodgeIntegrals -- Hodge integrals on the moduli space of curves
- hodgeRing -- create a ring containing algebraic classes on moduli spaces of curves
- integral -- evaluate Hodge integrals

## For the programmer

The object ch is an indexed variable table.

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/HodgeIntegrals.m2:708:0.