  One of the most spectacular experimental findings in the fractional quantum
Hall effect is evidence for an emergent Fermi surface when the electron density
is nearly half the density of magnetic flux quanta ($\nu = 1/2$). The seminal
work of Halperin, Lee, and Read (HLR) first predicted that at $\nu = 1/2$
composite fermions--bound states of an electron and a pair of
vortices--experience zero net magnetic field and can form a "composite Fermi
liquid" with an emergent Fermi surface. In this paper we use infinite cylinder
DMRG to provide compelling numerical evidence for the existence of a Fermi sea
of composite fermions for realistic interactions between electrons at $\nu =
1/2$. Moreover, we show that the state is particle-hole symmetric, in contrast
to the construction of HLR. Instead, our findings are consistent if the
composite fermions are massless Dirac particles, at finite density, similar to
the surface state of a 3D topological insulator. Exploiting this analogy we
devise a numerical test and successfully observe the suppression of $2k_F$
backscattering characteristic of Dirac particles.
