Trying to read this so-called "Note" by Nick Katz and cannot get over some of his notation. The fundamental group stuff is fine, but then he...seems to define some notation with the same notation in the definition in the first paragraph of page 2. Letting $U_0/\mathbb{F}_q$ be an affine, smooth, geommetrically connected curve, we let
$R^i:= R^if_\star\mathbb{Q}_\ell$
for every morphism $f:\chi\rightarrow U_0$. I'm guessing that the $f_\star$ is the same as $f_*$, a pushforward by $f$ of $\mathbb{Q}_\ell$ to the $i$th cohomology group of $U_0$, but I don't know what this $R^i$ is supposed to be when it's defined by itself...
Anyone care to clarify and help me understand what Nick Katz might be meaning by $R^i$?
(Here's a copy of the note itself: https://web.math.princeton.edu/~nmk/baby16.pdf )