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f(R) Dual Theories of Quintessence : Expansion-Collapse Duality

arXiv:2105.10521    [ pdf ,  other ]    gr-qc   astro-ph.CO   hep-th f ( R )  Dual Theories of Quintessence : Expansion-Collapse Duality Authors:   Dipayan Mukherjee ,  H. K. Jassal ,  Kinjalk Lochan Abstract :  The accelerated expansion of the universe demands presence of an exotic matter, namely the dark energy. Though the cosmological constant fits this role very well, a scalar field minimally coupled to gravity, or quintessence, can also be considered as a viable alternative for the cosmological constant. We study  f ( R )  gravity models which can lead to an effective description of dark energy implemented by quintessence fields in Einstein gravity, using the Einstein frame-Jordan frame duality. For a family of viable quintessence models, the reconstruction of the  f ( R )  function in the Jordan frame consists of two parts. We first obtain a perturbative solution of  f ( R )  in the Jordan fr...
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Consistency tests of ΛCDM from the early ISW effect: implications for early-time new physics and the Hubble tension

  arXiv:2105.10425    [ pdf ,  other ]    astro-ph.CO   gr-qc   hep-ph Consistency tests of  Λ CDM from the early ISW effect: implications for early-time new physics and the Hubble tension Authors:   Sunny Vagnozzi Abstract :  New physics increasing the expansion rate just prior to recombination is among the least unlikely solutions to the Hubble tension, and would be expected to leave an important signature in the early Integrated Sachs-Wolfe (eISW) effect, a source of Cosmic Microwave Background (CMB) anisotropies arising from the time-variation of gravitational potentials when the Universe was not completely matter dominated. Why, then, is there no clear evidence for new physics from the CMB alone, and why does the  Λ CDM model fit CMB data so well? These questions and the vastness of the Hubble tension theory model space motivate general consistency tests of  Λ CDM. I perform an eISW-based consistency test of  Λ C...
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A short mean free path at z=6 favors late and rapid reionization by faint galaxies

  arXiv:2105.10511    [ pdf ,  other ]    astro-ph.CO A short mean free path at  z = 6  favors late and rapid reionization by faint galaxies Authors:   Christopher Cain ,  Anson D'Aloisio ,  Nakul Gangolli ,  George D. Becker Abstract :  Recent measurements of the ionizing photon mean free path ( λ m f p 912 ) at  5 < z < 6  suggest that the IGM was rapidly evolving at those times. We use radiative transfer simulations to explore the implications for reionization, with a focus on the short value of  λ m f p 912 = 3.57 + 3.09 − 2.14  cMpc/ h  at  z = 6 . We introduce a model for sub-resolution ionizing photon sinks based on radiative hydrodynamics simulations of small-scale IGM clumping. We argue that the rapid evolution in  λ m f p 912  at  z = 5 − 6 , together with constraints on the metagalactic ionizing background, favors a late reionization process in which the neutral...
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