Studying large-scale structure probes of modified gravity with COLA

We study the effect of two Modified Gravity (MG) theories, $f(R)$ and nDGP, on three probes large-scale structure, real space power spectrum estimator $Q_0$, bispectrum voids, validate fast approximate COLA simulations against full $N$-body for prediction these probes. find that using first even multipoles redshift to estimate $Q_0$ is enough reproduce MG boost factors both halo galaxy catalogues. By analysing reduced Dark Matter (DM), we show strong signal present in DM mainly due enhanced spectrum. warn about adopting screening approximations as this neglects non-linear contributions can source a significant component at level, but argue not problem galaxies where dominated by bias. Finally, perform void-finding our mock catalogues ZOBOV watershed algorithm. To apply linear model Redshift-Space Distortion (RSD) void-galaxy cross-correlation function, examine effects void profiles entering into RSD model. relevant signals integrated-density, velocity dispersion radial nDGP theory. Fitting growth rate, recover theory an model, which larger than $\Lambda$CDM $3 \sigma$ level. In cannot naively compare results fit with scale-dependent, obtain are consistent prediction.