An Arthur parameter supplements a Langlands parameter by an algebraic 
factor commuting with a weight-zero part. For a split group over a global function
field 
,
one form of this datum consists of homomorphisms 
and 
. The homomorphism 
is algebraic, and 
is a continuous 
-adic homomorphism, with 
, defined over a finite extension of 
, unramified at almost all places, and pure of weight zero
in every algebraic representation of 
. Parameters are considered up to simultaneous conjugation
by 
.
The algebraic factor accounts for nonzero weights. Diagonal specialization recovers
a Weil parameter by
 |
where 
and the degree group homomorphism is normalized
to send the Frobenius at a closed point of degree
to 
.
