Damien A. Easson

Entropic Accelerating Universe

Abstract To accommodate the observed accelerated expansion of the universe, one popular idea is to invoke a driving term in the Friedmann–Lemaitre equation of dark energy which must then comprise 70% of the present cosmological energy density. We propose an alternative interpretation which takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there. Dark energy is thereby obviated and the acceleration is due to an entropic force naturally arising from the information storage on the horizon surface screen. We consider an additional quantitative approach inspired by surface terms in general relativity and show that this leads to the entropic accelerating universe.

Reheating predictions in single field inflation

Reheating is a transition era after the end of inflation, during which the inflaton is converted into the particles that populate the Universe at later times. No direct cosmological observables are normally traceable to this period of reheating. Indirect bounds can however be derived. One possibility is to consider cosmological evolution for observable CMB scales from the time of Hubble crossing to the present time. Depending upon the model, the duration and final temperature after reheating, as well as its equation of state, may be directly linked to inflationary observables. For single-field inflationary models, if we approximate reheating by a constant equation of state, one can derive relations between the reheating duration (or final temperature), its equation of state parameter, and the scalar power spectrum amplitude and spectral index. While this is a simple approximation, by restricting the equation of state to lie within a broad physically allowed range, one can in turn bracket an allowed range of

Cosmological constraints from CMB distortion

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When matter matters

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Warm Dirac-Born-Infeld inflation

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Black holes in an asymptotically safe gravity theory with higher derivatives

for these models. The added constraints can help break degeneracies between inflation models that otherwise overlap in their predictions for

Asymptotically safe gravity as a scalar-tensor theory and its cosmological implications

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Circumventing the eta problem in building an inflationary model in string theory

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Observational signatures of gravitational couplings in DBI inflation

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Searching for a matter bounce cosmology with low redshift observations

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