get_class.html

FUNCTION: get_class - conversion from "tub_enc" to K₀ X

CALLING SEQUENCE:
get_class([q,i,s,l])

PARAMETERS:
q - the "slope" (a rational, or infinity)
i - number of an exceptional tube (i=1,..,t)
s - socle index (an integer, which is taken modulo p_i
l - the quasi-length (height in corresponding tube)

SYNOPSIS:

Computes the K₀ X -class from a given dataset of type "tub_enc" which encodes an indecomposable sheaf by a set of data relating to its position within the tubular family. (Cf. help page for type/tub_enc.)
is only defined for one of the tubular weight-sequences, i.e. (2,3,6), (3,3,3), (2,2,2,2) and (2,4,4).
get_class([q,i,s,l]) returns the Grothendieck-class of the coherent sheaf corresponding to the given data. The "inverse" procedure to get_class is get_tub.

EXAMPLES:

> with(tubular):

> read_in(3,3,3);

> get_class([7/4,1,2,5]); show(%);

> read_in(2,3,6);

> get_class([-41/3,3,0,4]); show(%);

BACK TO: start page of the crep online manual, tubular