EFTofLSS Trispectrum Model Validated on AbacusSummit Simulations Extends k_max to 0.12 h Mpc^{-1}

The analysis combined one-loop power spectrum, tree-level bispectrum and tree-level trispectrum measurements to test scale cuts and information gain. In a DESI-like volume the trispectrum improved omega_cdm constraints by up to 15 percent while allowing a maximum wavenumber of k_max = 0.12 h Mpc^{-1} once FoG counterterms were included. This constitutes the first end-to-end cosmological inference using the three-dimensional trispectrum in redshift space.

Prior EFTofLSS work stopped at the bispectrum; the new model closes that gap by deriving all necessary counterterms and covariance contributions for the four-point function. The large simulation volume permitted direct measurement of covariance and binning effects, revealing that stochasticity and Fingers-of-God terms dominate the error budget above k approximately 0.1 h Mpc^{-1}.

Because the study remains a preprint, the claimed 15 percent improvement must be confirmed on actual DESI data before it alters parameter pipelines. Future analyses should test the model on hydrodynamical simulations and include one-loop trispectrum corrections to push k_max higher.

Next steps include application to early DESI luminous red galaxy samples and extension to primordial non-Gaussianity templates that leave distinct trispectrum signatures.