Talk detail

Participant	Maeda, Kei-ichi
Institution	Waseda University - Okubo 3-4-1, Shinjuku - Tokyo - - Japan

Session	BS2	Accepted		Order	Time
Talk	Oral abstract	Title	The origin of scalar fields and their roles in cosmology
Coauthors
Abstract	In cosmology, we assume the existence of many scalar fields, but in the standard model of particle physics, we know only the Higgs scalar field. In this talk, we survey the origin of scalar fields, which may appear effectively from fundamental theories of gravitation and will play important roles in cosmology. We mainly discuss scalar-tensor gravity theory, higher-dimensional unified theories such as superstring, and higher-curvature theories of gravitation such as f(R) gravity theory.
Pdf file

Session	AT4	Accepted		Order	Time
Talk	Oral abstract	Title	Dark energy and dark matter in the ghost-free bigravity theory
Coauthors
Abstract	We study dynamics of Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime based on the ghost-free bigravity theory. We find two stable attractors for spacetime with gtwinh dust matter fields: One is de Sitter accelerating universe and the other is matter dominated universe. A considerable number of initial data leads to de Sitter universe, although we also find matter dominated universe or spacetime with a future singularity for some initial data. The cosmic no-hair conjecture does not exactly hold, but the Lambda-CDM model is found naturally as an attractor. We also analyze the possibility for the twin matter fluid to be dark matter in gour world". Dark matter appears as the galactic missing mass, is required in the cosmic structure formation and is found in the cosmic pie (the content of the Universe). We show the bigravity theory can also explain those facts by twin matter fluid when the Compton wavelength of the massive graviton is shorter than a galactic scale.
Pdf file