Precision cosmology with voids: definition, methods, dynamics

We propose a new definition of cosmic voids based on methods of Lagrangian orbit reconstruction as well as an algorithm to find them in actual data called DIVA. Our technique is intended to yield results which can be modeled sufficiently accurately to create a new probe of precision cosmology. We then develop an analytical model of the ellipticity of voids found by our method based on Zel'dovich approximation. We measure in N-body simulation that this model is precise at the 0.1% level for the mean ellipticity of voids of size greater than ~4 Mpc/h. We estimate that at this scale, we are able to predict the ellipticity with an accuracy of 0.02. Finally, we compare the distribution of void shapes in N-body simulation for two different equations of state w of the dark energy. We conclude that our method is far more accurate than Eulerian methods and is therefore promising as a precision probe of dark energy phenomenology.