Weak lensing effects in the measurement of the dark energy equation of
  state with LISA
  The Laser Interferometer Space Antenna's (LISA's) observation of supermassive
binary black holes (SMBBH) could provide a new tool for precision cosmography.
Inclusion of sub-dominant signal harmonics in the inspiral signal allows for
high-accuracy sky localization, dramatically improving the chances of finding
the host galaxy and obtaining its redshift. A SMBBH merger can potentially have
component masses from a wide range ($10^5 - 10^8\,\Ms$) over which parameter
accuracies vary considerably. We perform an in-depth study in order to
understand (i) what fraction of possible SMBBH mergers allow for sky
localization, depending on the parameters of the source, and (ii) how
accurately $w$ can be measured when the host galaxy can be identified. We also
investigate how accuracies on all parameters improve when a knowledge of the
sky position can be folded into the estimation of errors. We find that $w$ can
be measured to within a few percent in most cases, if the only error in
measuring the luminosity distance is due to LISA's instrumental noise and the
confusion background from Galactic binaries. However, weak lensing-induced
errors will severely degrade the accuracy with which $w$ can be obtained,
emphasizing that methods to mitigate weak lensing effects would be required to
take advantage of LISA's full potential.
