Model-independent approach to effective sound speed in multi-field inflation
@article{Romano2020ModelindependentAT, title={Model-independent approach to effective sound speed in multi-field inflation}, author={Antonio Enea Romano and Krzysztof Turzyński and Sergio Andr{\'e}s Vallejo-Pe{\~n}a}, journal={The European Physical Journal C}, year={2020}, volume={82}, pages={1-16} }
For any physical system satisfying the Einstein’s equations, the comoving curvature perturbations satisfy an equation involving the momentum-dependent effective sound speed, valid for any system with a well defined energy-stress tensor, including multi-fields models of inflation. We derive a general model-independent formula for the effective sound speed of comoving adiabatic perturbations, valid for a generic field-space metric, without assuming any approximation to integrate out entropy…
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