injectivity radius of hyperbolic surface Given a positive real number $l$. Does there exist a closed hyperbolic surface $X$ so that injectivity radius not less than $l$?
 A: Let $Y$ be a compact hyperbolic surface.  There are only finitely many closed geodesics in $Y$ whose lengths are less that $\ell$.  Since $\pi_1(Y)$ is residually finite, there is a normal subgroup of finite index in $\pi_1(Y)$ that does not contain anything in the conjugacy classes corresponding to these geodesics. The corresponding finite covering space $X$ of $Y$ has no closed geodesics of length less than $\ell$.
A: Buser in 1992 gives a lower bound on the Bers constant for surfaces of genus $g$, and it goes to infinity as $g$ goes to infinity.  So this means there's compact hyperbolic surfaces whose injectivity radius is arbitrarily large, but you have to go to high genus to realize them. 
P. Buser. Geometry and spectra of compact Riemann surfaces Prog. Math. Vol 106. (1992)
The genus needs to grow like the square of the injectivity radius.  Probably a good way to find this surface would be to use Fenchel-Nielsen coordinates, where the pants correspond to points on a planar square lattice and you want to connect the vertices in some (likely non-planar) tri-valent graph configuration, so that it represents pants. Then you want to connect the edges in a way so that there's no short closed loops in the resulting graph.  So I'm describing a surface that's less the gluing-together of pants, but more the gluing together of quadratically-many "short shorts". 
