We study observational consequences of the model for dark energy proposed in<br />
[1] (Aoki et al., Phys.Rev. D97 (2018) no.4, 043517). We assume our universe<br />
has been created by bubble nucleation, and consider quantum fluctuations of an<br />
ultralight scalar field. Residual effects of fluctuations generated in an<br />
ancestor vacuum (de Sitter space in which the bubble was formed) is interpreted<br />
as dark energy. Its equation of state parameter w(z) has a characteristic form,<br />
approaching -1 in the future, but -1/3 in the past. A novel feature of our<br />
model is that dark energy effectively increases the magnitude of the negative<br />
spatial curvature in the evolution of the Hubble parameter, though it does not<br />
alter the definition of the angular diameter distance. We perform Fisher<br />
analysis and forecast the constraints for our model from future galaxy surveys<br />
by Square Kilometre Array and Euclid. Due to degeneracy between dark energy and<br />
the spatial curvature, galaxy surveys alone can determine these parameters only<br />
for optimistic choices of their values, but combination with other independent<br />
observations, such as CMB, will greatly improve the chance of determining them.