Forecast for cosmological parameter estimation with gravitational-wave
  standard sirens from the LISA-Taiji network
  LISA and Taiji are expected to form a space-based gravitational-wave (GW)
detection network in the future. In this work, we make a forecast for the
cosmological parameter estimation with the standard siren observation from the
LISA-Taiji network. We simulate the standard siren data based on a scenario
with configuration angle of $40^{\circ}$ between LISA and Taiji. Three models
for the population of massive black hole binary (MBHB), i.e., pop III, Q3d, and
Q3nod, are considered to predict the events of MBHB mergers. We find that,
based on the LISA-Taiji network, the number of electromagnetic (EM)
counterparts detected is almost doubled compared with the case of single Taiji
mission. Therefore, the LISA-Taiji network's standard siren observation could
provide much tighter constraints on cosmological parameters. For example,
solely using the standard sirens from the LISA-Taiji network, the constraint
precision of $H_0$ could reach $1.3\%$. Moreover, combined with the CMB data,
the GW-EM observation based on the LISA-Taiji network could also tightly
constrain the equation of state of dark energy, e.g., the constraint precision
of $w$ reaches about $4\%$, which is comparable with the result of CMB+BAO+SN.
It is concluded that the GW standard sirens from the LISA-Taiji network will
become a useful cosmological probe in understanding the nature of dark energy
in the future.
