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Register a new userDark Photon Oscillations in Our Inhomogeneous Universe
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A dark photon may kinetically mix with the ordinary photon, inducing oscillations with observable imprints on cosmology. Oscillations are resonantly enhanced if the dark photon mass equals the ordinary photon plasma mass, which tracks the free electron number density. Previous studies have assumed a homogeneous Universe; in this Letter, we introduce for the first time an analytic formalism for treating resonant oscillations in the presence of inhomogeneities of the photon plasma mass. We apply our formalism to determine constraints from Cosmic Microwave Background photons oscillating into dark photons, and from heating of the primordial plasma due to dark photon dark matter converting into low-energy photons. Including the effect of inhomogeneities demonstrates that prior homogeneous constraints are not conservative, and simultaneously extends current experimental limits into a vast new parameter space.
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A dark photon may kinetically mix with the Standard Model photon, leading to observable cosmological signatures. The mixing is resonantly enhanced when the dark photon mass matches the primordial plasma frequency, which depends sensitively on the underlying spatial distribution of electrons. Crucially, inhomogeneities in this distribution can have a significant impact on the nature of resonant
Coupled cosmologies can predict values for the cosmological parameters at low redshifts which may differ substantially from the parameters values within non-interacting cosmologies. Therefore, low redshift probes, as the growth of structure and the dark matter distribution via galaxy and weak lensing surveys constitute a unique tool to constrain interacting dark sector models. We focus here on weak lensing forecasts from future Euclid and LSST-like surveys combined with the ongoing Planck cosmic microwave background experiment. We find that these future data could constrain the dimensionless coupling to be smaller than a few $times 10^{-2}$. The coupling parameter $xi$ is strongly degenerate with the cold dark matter energy density $Omega_{c}h^2$ and the Hubble constant $H_0$.These degeneracies may cause important biases in the cosmological parameter values if in the universe there exists an interaction among the dark matter and dark energy sectors.
Dark Energy models are numerous and distinguishing between them is becoming difficult. However, using distinct observational probes can ease this quest and gives better assessment to the nature of Dark energy. To this end, the plausibility of neutrino oscillations to be a probe of Dark Energy models is investigated. First, a generalized formalism of neutrino (spinor field) interaction with a classical scalar field in curved space-time is presented. This formalism is then applied to two classes of Dark Energy models in a flat Friedman-Lema^itre-Robertson-Walker metric: a Cosmological Constant and scalar field Dark Energy coupled to neutrinos. By looking at the neutrino oscillation probabilitys evolution with redshift, these models can be distinguished, for certain neutrino and scalar field coupling properties. This evolution could be traced by neutrino flux in future underground, terrestrial or extraterrestrial neutrino telescopes, which would assess probing Dark Energy models with this technique.
We perform calculations of dark photon production and decay in the early universe for ranges of dark photon masses and vacuum coupling with standard model photons. Simultaneously and self-consistently with dark photon production and decay, our calculations include a complete treatment of weak decoupling and big bang nucleosynthesis (BBN) physics. These calculations incorporate all relevant weak, electromagnetic, and strong nuclear reactions, including charge-changing (isospin-changing) lepton capture and decay processes. They reveal a rich interplay of dark photon production, decay, and associated out-of-equilibrium transport of entropy into the decoupling neutrino seas. Most importantly, the self-consistent nature of our simulations allows us to capture the magnitude and phasing of entropy injection and dilution. Entropy injection-induced alteration of the time-temperature-scale factor relation during weak decoupling and BBN leads to changes in the light element abundance yields and the total radiation content (as parametrized by $N_{rm eff}$). These changes suggest ways to extend previous dark photon BBN constraints. However, our calculations also identify ranges of dark photon mass and couplings not yet constrained, but perhaps accessible and probable, in future Stage-4 cosmic microwave background experiments and future high precision primordial deuterium abundance measurements.
We investigate the effect of the accelerated expansion of the Universe due to a cosmological constant, $Lambda$, on the cosmic star formation rate. We utilise hydrodynamical simulations from the EAGLE suite, comparing a $Lambda$CDM Universe to an Einstein-de Sitter model with $Lambda=0$. Despite the differences in the rate of growth of structure, we find that dark energy, at its observed value, has negligible impact on star formation in the Universe. We study these effects beyond the present day by allowing the simulations to run forward into the future ($t>13.8$ Gyr). We show that the impact of $Lambda$ becomes significant only when the Universe has already produced most of its stellar mass, only decreasing the total co-moving density of stars ever formed by ${approx}15%$. We develop a simple analytic model for the cosmic star formation rate that captures the suppression due to a cosmological constant. The main reason for the similarity between the models is that feedback from accreting black holes dramatically reduces the cosmic star formation at late times. Interestingly, simulations without feedback from accreting black holes predict an upturn in the cosmic star formation rate for $t>15$ Gyr due to the rejuvenation of massive ($ > 10^{11} mathrm{M}_{odot}$) galaxies. We briefly discuss the implication of the weak dependence of the cosmic star formation on $Lambda$ in the context of the anthropic principle.
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