Neutrino mass bounds from confronting an effective model with BOSS Lyman-α data

Abstract

We present an effective model for the one-dimensional Lyman-α flux power spectrum far above the baryonic Jeans scale. The main new ingredient is constituted by a set of two parameters that encode the impact of small, highly non-linear scales on the one-dimensional power spectrum on large scales, where it is measured by BOSS. We show that, by marginalizing over the model parameters that capture the impact of the intergalactic medium, the flux power spectrum from both simulations and observations can be described with high precision. The model displays a degeneracy between the neutrino masses and the (unknown, in our formalism) normalization of the flux power spectrum. This degeneracy can be lifted by calibrating one of the model parameters with simulation data, and using input from Planck CMB data. We demonstrate that this approach can be used to extract bounds on the sum of neutrino masses with comparably low numerical effort, while allowing for a conservative treatment of uncertainties from the dynamics of the intergalactic medium. An explorative analysis yields an upper bound of 0.16eV at 95% C.L. when applied to BOSS data at 3 ≤ z ≤ 4.2. We also forecast that if the systematic and statistical errors will be reduced by a factor two the upper bound will become 0.1eV at 95% C.L, and 0.056eV when assuming a 1% error.

Non-linearities in the Lyman-$α$ forest and in its cross-correlation with dark matter halos

“…Recently, [50] presented an analysis of the 1D correlations in the Lyα forest using a model inspired by perturbation theory and effective field theory of large-scale structure. Instead of relying on free parameters to describe the non-linear growth of structure on mildly non-linear scales, the authors used a model (first presented in [49]) that captures non-linearities by using matter and velocity power spectra computed with perturbation theory at one-loop:…”

“…where P 1−loop δδ , P 1−loop δθ , and P 1−loop θθ are the matter-matter, matter-velocity divergence, and velocity divergence-velocity divergence power spectra computed up to 1-loop in perturbation theory (they are equal at tree level), and D IGM is a small-scale correction that only models IGM physics. 5 Even though the authors of [50] only proposed this model for analyses of the 1D power spectrum, here we discuss the interesting idea of using perturbation theory at one-loop to model the mildly non-linear regime of the 3D flux power spectrum.…”

“…In [50], the impact of non-linearities on the 1D flux power spectrum is captured by adding a counterterm that parameterizes the impact of strong small-scale non-linearities, along the lines of effective field theory (EFT) methods. For the 3D spectrum, the counterterm from [50] is not sufficient, since it describes the influence of non-linear corrections on the integrated 1D spectrum only, by construction. Instead, a more detailed EFT model would be required for the 3D spectrum, along the lines of [67].…”

“…From there, one may proceed down a "pure perturbation theory" path or take a "fitting function" path. To proceed down the former, one adds higher-order terms consistent with symmetries of the forest to the linear flux fluctuation field [49][50][51][52] and autocorrelates the result. Bias coefficients are found by fitting the model to simulation outputs.…”

Gravitational waves from a holographic phase transition

“…The generation of bubbles and whether conditions are right for them to proliferate is described by four main JHEP04(2021)100 parameters: transition strength α, transition rate β, nucleation temperature T N , and the wall speed v w . Recently, it has also been pointed out that the sound speed, controlled by the stiffness ∂p/∂e is also important [55,65].…”