Safe Haskell | None |
---|---|

Language | Haskell2010 |

We compute the `GL2`

-equivariant open and closed CSM classes recursively,
starting from smallest strata.

The idea is that we have a smooth resolution of the *closure* of the strata `X_mu`

,
namely, the set of `n=length(mu)`

ordered points: `Q^n = P^1 x ... x P^1`

We can pushforward this to `Q^m`

, and get a linear combination of the strata of
the CSM-s we want to compute. Since the smallest strata is actually closed,
we know that, and can work upward from that.

This is rather slow, however as it's a very different algorithm copmared to the direct approach, it's useful for checking if the two agrees.

# CSM calculation

upperClass :: ChernBase base => SetPartition -> ZMod (Eta base) Source #

This is just the pushforward along `Delta_nu`

of the tangent Chern class.

As `Delta`

is injective, the resulting class is just the CSM class of the
closed *ordered* strata corresponding to one of the set partitions which
matches the given partition

lowerClass :: ChernBase base => Partition -> ZMod (Gam base) Source #

pushforward of `upperCSM`

to the space of unordered points