Abstract:The discrepancy between the values of the Hubble constant H 0 derived from the local distance ladder and the Cosmic Microwave Background provides a tantalising hint of new physics. We explore a potential resolution involving screened fifth forces in the local Universe, which alter the Cepheid calibration of supernova distances. In particular, if the Cepheids with direct distance measurements from parallax or water masers are screened but a significant fraction of those in other galaxies are not, neglecting the… Show more
“…Modified gravity theories are able to simultaneously drive the acceleration of the cosmic expansion (dark energy) while remaining compatible with solar system tests of gravity [44][45][46][47]. They are also leading candidates for explaining the Hubble tension [48][49][50]. Their success is due to screening mechanisms, which suppress fifth forces in high density environments.…”
The LIGO/Virgo collaboration has recently announced the detection of a heavy binary black hole merger, with component masses that cannot be explained by standard stellar structure theory. In this letter we propose several explanations based on models of new physics, including new light particle losses, modified gravity, large extra dimensions, and a small magnetic moment of the neutrino. Each of these affect the physics of the pair-instability differently, leading to novel mechanisms for forming black holes inside the mass gap.
“…Modified gravity theories are able to simultaneously drive the acceleration of the cosmic expansion (dark energy) while remaining compatible with solar system tests of gravity [44][45][46][47]. They are also leading candidates for explaining the Hubble tension [48][49][50]. Their success is due to screening mechanisms, which suppress fifth forces in high density environments.…”
The LIGO/Virgo collaboration has recently announced the detection of a heavy binary black hole merger, with component masses that cannot be explained by standard stellar structure theory. In this letter we propose several explanations based on models of new physics, including new light particle losses, modified gravity, large extra dimensions, and a small magnetic moment of the neutrino. Each of these affect the physics of the pair-instability differently, leading to novel mechanisms for forming black holes inside the mass gap.
“…Note that there exist other categories of model aimed at solving the Hubble tension with very different ingredients and no enhancement of N eff (see e.g. [25,26] and references therein).…”
Many attempts to solve the Hubble tension with extended cosmological models combine an enhanced relic radiation density, acting at the level of background cosmology, with new physical ingredients affecting the evolution of cosmological perturbations. Several authors have pointed out the ability of combined Baryon Acoustic Oscillation (BAO) and Big Bang Nucleosynthesis (BBN) data to probe the background cosmological history independently of both CMB maps and supernovae data. Using state-of-the-art assumptions on BBN, we confirm that combined BAO, deuterium, and helium data are in tension with the SH0ES measurements under the ΛCDM assumption at the 3.2σ level, while being in close agreement with the CMB value. We subsequently show that floating the radiation density parameter N eff only reduces the tension down to the 2.6σ level. This conclusion, totally independent of any CMB data, shows that a high N eff accounting for extra relics (either free-streaming or self-interacting) does not provide an obvious solution to the crisis, not even at the level of background cosmology. To circumvent this strong bound, (i) the extra radiation has to be generated after BBN to avoid helium bounds, and (ii) additional ingredients have to be invoked at the level of perturbations to reconcile this extra radiation with CMB and LSS data.
“…Refs. [113][114][115][116][117][118][119][120][121][122][123][124][125][126][127]). It can also be used to constrain model-independent expansion histories of the Universe [128][129][130] at the few-percent level.…”
Line-intensity mapping (LIM) provides a promising way to probe cosmology, reionization and galaxy evolution. However, its sensitivity to cosmology and astrophysics at the same time is also a nuisance. Here we develop a comprehensive framework for modelling the LIM power spectrum, which includes redshift space distortions and the Alcock-Paczynski effect. We then identify and isolate degeneracies with astrophysics so that they can be marginalized over. We study the gains of using the multipole expansion of the anisotropic power spectrum, providing an accurate analytic expression for their covariance, and find a 10%-60% increase in the precision of the baryon acoustic oscillation scale measurements when including the hexadecapole in the analysis. We discuss different observational strategies when targeting other cosmological parameters, such as the sum of neutrino masses or primordial non-Gaussianity, finding that fewer and wider bins are typically more optimal. Overall, our formalism facilitates an optimal extraction of cosmological constraints robust to astrophysics.PACS numbers:
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