Search

Over the next decade, cosmological measurements of the large-scale structure of the Universe will be sensitive to the combined effects of dynamical dark energy and massive neutrinos. The matter power spectrum is a key repository of this information. We extend higher-order perturbative methods for computing the power spectrum to investigate these effects over quasilinear scales. Through comparison with N-body simulations, we establish the regime of validity of a time-renormalization group perturbative treatment that includes dynamical dark energy and massive neutrinos. We also quantify the accuracy of standard, renormalized and Lagrangian resummation (LPT) perturbation theories without massive neutrinos. We find that an approximation that neglects neutrino clustering as a source for nonlinear matter clustering predicts the baryon acoustic oscillation (BAO) peak position to 0.25% accuracy for redshifts 1 ≤ z ≤ 3, justifying the use of LPT for BAO reconstruction in upcoming surveys. We release a modified version of the public Copter code which includes the additional physics discussed in the paper. [ABSTRACT FROM AUTHOR]

The chameleon scalar field is a matter-coupled dark energy candidate whose nonlinear self-interaction partially screens its fifth force at laboratory scales. Nevertheless, small-scale experiments such as the torsion pendulum can provide powerful constraints on chameleon models. Here we develop a simple approximation for computing chameleon fifth forces in torsion pendulum experiments such as Eôt-Wash. We show that our approximation agrees well with published constraints on the quartic chameleon, and we use it to extend these constraints to a much wider range of models. Finally, we forecast the constraints which will result from the next-generation Eöt-Wash experiment, and show that this experiment will exclude a wide range of quantum-stable models [ABSTRACT FROM AUTHOR]

Chameleon fields, which are scalar field dark energy candidates, can evade fifth force constraints by becoming massive in high-density regions. However, this property allows chameleon particles to be trapped inside a vacuum chamber with dense walls. Afterglow experiments constrain photon-coupled chameleon fields by attempting to produce and trap chameleon particles inside such a vacuum chamber, from which they will emit an afterglow as they regenerate photons. Here we discuss several theoretical and systematic effects underlying the design and analysis of the GammeV and CHASE afterglow experiments. We consider chameleon particle interactions with photons, Fermions, and other chameleon particles, as well as with macroscopic magnetic fields and matter. The afterglow signal in each experiment is predicted, and its sensitivity to various properties of the experimental apparatus is studied. Finally, we use CHASE data to exclude a wide range of photon-coupled chameleon dark energy models. [ABSTRACT FROM AUTHOR]

It is known that if the Peccei-Quinn symmetry-breaking field is displaced from its minimum during inflation, the axion isocurvature spectrum is generically strongly blue tilted with a break transition to a flat spectrum. We fit this spectrum (incorporated into the "vanilla" Λ-CDM cosmological model) to the Planck and BOSS DR11 data to assess how much the existing data can accommodate the presence of axionic blue-tilted isocurvature perturbations. We find that the preferred parameter region is consistent with all of the dark matter being composed of QCD axions in the context of inflationary cosmology with an expansion rate of order 108 GeV, the axion decay constant of order 1013 GeV, and the initial misalignment angle of order unity. The data are consistent with there being no isocurvature perturbations at the level of just above one sigma. Intriguingly, isocurvature with a spectral break may at least partially explain the low-ℓ vs high-ℓ anomalies seen in the CMB data. [ABSTRACT FROM AUTHOR]

Blue axion isocurvature perturbations are both theoretically well motivated and interesting from a detectability perspective. These power spectra generically have a break from the blue region to a flat region. Previous investigations of the power spectra were analytic, which left a gap in the predicted spectrum in the break region due to the nonapplicability of the used analytic techniques. We therefore compute the isocurvature spectrum numerically for an explicit supersymmetric axion model. We find a bump that enhances the isocurvature signal for this class of scenarios. A fitting function of three parameters is constructed that fits the spectrum well for the particular axion model we study. This fitting function should be useful for blue isocurvature signal hunting in data and making experimental sensitivity forecasts. [ABSTRACT FROM AUTHOR]