Cosmological Parameter Estimation from the Two-Dimensional Genus
  Topology -- Measuring the Expansion History using the Genus Amplitude as a
  Standard Ruler
  We measure the genus of the galaxy distribution in two-dimensional slices of
the SDSS-III BOSS catalog to constrain the cosmological parameters governing
the expansion history of the Universe. The BOSS catalogs are divided into
twelve concentric shells over the redshift range $0.25 < z < 0.6$ and we
repeatedly measure the genus from the two-dimensional galaxy density fields,
each time varying the cosmological parameters used to infer the
distance-redshift relation to the shells. We also indirectly reconstruct the
two-dimensional genus amplitude using the three-dimensional genus measured from
SDSS Main Galaxy Sample with galaxies at low redshift $z < 0.12$. We combine
the low- and high-redshift measurements, finding the cosmological model which
minimizes the redshift evolution of the genus amplitude, using the fact that
this quantity should be conserved. Being a distance measure, the test is
sensitive to the matter density parameter ($\Omega_{\rm m}$) and equation of
state of dark energy ($w_{\rm de}$). We find a constraint of $w_{\rm de} =
-1.05^{+0.13}_{-0.12}$, $\Omega_{\rm m} = 0.303 \pm 0.036$ after combining the
high- and low-redshift measurements and combining with Planck CMB data. Higher
redshift data and combining data sets at low redshift will allow for stronger
constraints.
