Phase-resolved scalar distance bounds are derived for ekpyrotic, bouncing, and cyclic cosmologies, yielding a master condition that lower-bounds ε_ek from remaining distance after conversion and bounce.
Non-singular bounce scenarios in loop quantum cosmology and the effective field description
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abstract
A non-singular bouncing cosmology is generically obtained in loop quantum cosmology due to non-perturbative quantum gravity effects. A similar picture can be achieved in standard general relativity in the presence of a scalar field with a non-standard kinetic term such that at high energy densities the field evolves into a ghost condensate and causes a non-singular bounce. During the bouncing phase, the perturbations can be stabilized by introducing a Horndeski operator. Taking the matter content to be a dust field and an ekpyrotic scalar field, we compare the dynamics in loop quantum cosmology and in a non-singular bouncing effective field model with a non-standard kinetic term at both the background and perturbative levels. We find that these two settings share many important properties, including the result that they both generate scale-invariant scalar perturbations. This shows that some quantum gravity effects of the very early universe may be mimicked by effective field models.
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A quasi-dust ekpyrotic two-field model in Loop Quantum Cosmology produces viable primordial power spectra via coupled scalar and tensor perturbations.
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Phase-resolved field-space distance bounds in ekpyrotic, bouncing and cyclic cosmologies
Phase-resolved scalar distance bounds are derived for ekpyrotic, bouncing, and cyclic cosmologies, yielding a master condition that lower-bounds ε_ek from remaining distance after conversion and bounce.
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Quasi-dust ekpyrotic scenario in Loop Quantum Cosmology
A quasi-dust ekpyrotic two-field model in Loop Quantum Cosmology produces viable primordial power spectra via coupled scalar and tensor perturbations.
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Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution
Modified gravity theories supply viable mathematical frameworks for inflation, bounces, and dark energy eras that match observational data.