Speaker
Description
The ΛCDM model, the current standard cosmological model, is capable of describing the geometric and structural evolution of the universe and has been supported by measurements of various cosmological observables, including the large-scale structure (LSS). However, the ΛCDM model requires the assumption of the existence of unknown matter (dark matter), which is the source of the gravitational force of celestial body formation, and unknown energy (cosmological constant, or more generally, dark energy), which is the source of accelerated expansion. In the ΛCDM model, gravitational interaction is described by General Relativity (GR). One possible solution to the above problem is an attempt to explain the universe's accelerated expansion without introducing dark energy by modifying the theory of gravity from GR on cosmological scales. This is called “the modified gravity theory”. Recent observations have improved the accuracy of LSS measurements, and some results suggest internal inconsistency of the ΛCDM model. Future surveys such as the Nancy Grace Roman Space Telescope (hereafter, Roman) are planned, and are expected to make it possible to test the modified gravity theory on cosmological scales. In particular, we will implement the Boltzmann code MGCAMB, which enables the calculation of the power spectrum with modified gravity models, in the cosmological analysis pipeline COCOA, which is being developed for Roman. Then we’ll analyze the final data from the Subaru HSC to test gravity first. MGCAMB can perform theoretical calculations dealing with phenomenological parameters (μ-Σ parameters) that modify the gravity felt by non-relativistic and relativistic matter, without using a specific modified gravity theory. In this presentation, we discuss the cosmological constraints predicted by COCOA with MGCAMB implemented.
