Separating the early universe from the late universe: Cosmological parameter estimation beyond the black box

Abstract

We present a method for measuring the cosmic matter budget without assumptions about speculative Early Universe physics, and for measuring the primordial power spectrum P * (k) nonparametrically, either by combining CMB and LSS information or by using CMB polarization. Our method complements currently fashionable "black box" cosmological parameter analysis, constraining cosmological models in a more physically intuitive fashion by mapping measurements of CMB, weak lensing and cluster abundance into k-space, where they can be directly compared with each other and with galaxy and Lyα forest clustering. Including the new CBI results, we find that CMB measurements of P (k) overlap with those from 2dF galaxy clustering by over an order of magnitude in scale, and even overlap with weak lensing measurements. We describe how our approach can be used to raise the ambition level beyond cosmological parameter fitting as data improves, testing rather than assuming the underlying physics.

Gravitational Fluctuations as an Alternative to Inflation II. CMB Angular Power Spectrum

“…Finally, it is possible to investigate the effect of varying the lattice quantum amplitude c 0 appearing in the running of G, as in Eqs. (4) and (6). From the investigation of P (k), the value of c 0 that best fits the large scale data at small k is 2 c 0 = 16.04/7 ≈ 2.29.…”

“…A third additional parameter here is the quantum amplitude c 0 , which governs the amplitude of quantum correction in the RG running of Newton's constant G as given in Eqs. (4) and (6). Of the three parameters, as shown above in Sec.…”

“…In cosmology we know that the Universe is not perfectly homogeneous and isotropic but rather comprises of fluctuations, in matter density and in temperature, which are congregated and correlated in a rather specific manner. Detailed measurements of these fluctuations can be characterized by correlation functions and power spectra [1][2][3][4][5][6][7][8][9][10]. The question of why these fluctuations are distributed the way they are is thus an important one in cosmology.…”

Matter power spectrum: from Ly α forest to CMB scales

“…2, we present the Lyα data and explain how we compute the 3D matter power spectrum from the published 1D flux power spectrum. These data are the ones whose treatment differs the most from the previous study of Croft et al (2002) used in Tegmark & Zaldarriaga (2002). In Sec.…”

Spontaneous baryogenesis from extremely light asymmetric dark matter

“…To estimate the constraint on the dark sector temperature imposed by these experiments, we require conservatively that the dark matter free-streaming length λ F S = dt(v DM (t)/a(t)) be smaller than the scale probed by the Lyman-α forest measurements, i.e. λ F S Mpc [49]. If the dark sector decouples when it is non-relativistic or is only reheated to nonrelativistic temperatures, the free-streaming length grows logarithmically until matter radiation equality:…”