Descent
Revision as of 20:14, 6 August 2009 by JBL (talk | contribs) (Created page with 'Given a permutation <math>w = w_1 w_2 \cdots w_n)</math> of <math>\{1, 2, \ldots, n\}</math>, <math>w</math> is said to have a '''descent''' at position <math>i</math> if and…')
Given a permutation 
of 
, 
is said to have a descent at position 
if and only if 
. For example, the permutation 
has descents at positions 2 (since 
) and 4 (since 
).
The set of descents of a permutation is called its descent set. If is a permutation of then its descent set is some subset of 
.
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