Adiabatic and isocurvature perturbations in extended theories with kinetic couplings

Understand

The scalar field sector in low--energy effective field theories motivated by string theory often contains several scalar fields, some of which possess non--standard kinetic terms.

• In this paper, we study theories with two scalar fields, in which one of the fields has a non--canonical kinetic term.
• The kinetic coupling is allowed to depend on both fields, going beyond the work in the literature, which usually considers the case of the coupling to depend on the other field only.
• Our aim is to study adiabatic and isocurvature perturbations in these extended theories.