For ultra-light PBHs with extended mass distributions, new CMB-derived 95% exclusion bounds on f_PBH are obtained by jointly varying ΛCDM parameters, yielding f_PBH < 1.6 × 10^{-5} for a uniform distribution between 10^{15} and 10^{17} g.
A New Calculation of the Recombination Epoch
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abstract
We have developed an improved recombination calculation of H, HeI, and HeII in the early Universe which involves a line-by-line treatment of each atomic level. We find two major differences compared with previous calculations. Firstly, the ionization fraction x_e is approximately 10% smaller for redshifts <~800, due to non-equilibrium processes in the excited states of H. Secondly, HeI recombination is much slower than previously thought, and is delayed until just before H recombines. We describe the basic physics behind the new results and present a simple way to reproduce our calculation. This should enable fast computation of the ionization history (and quantities such as the power spectrum of CMB anisotropies which depend on it) for arbitrary cosmologies, without the need to consider the hundreds of atomic levels used in our complete model.
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The thesis presents a new 3-to-2 freezeout mechanism, bound-state effects on searches, a new axion interferometric search, reionization assessments, 21-cm constraints, and the DarkHistory code for ionization and thermal histories.
Upper bounds on the dark matter fraction in MACHOs of 10^3 to 10^7 solar masses are derived from limits on distortions to the global 21-cm signal at z~17, z~89, and z>300.
In an f(R, L_m) gravity model constrained by distance modulus data via chi-squared and MCMC, the authors report earlier nonlinear structure formation and higher matter-radiation equality redshift than Lambda CDM, with matching recombination redshift.
citing papers explorer
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CMB constraints on ultra-light primordial black holes with extended mass distributions
For ultra-light PBHs with extended mass distributions, new CMB-derived 95% exclusion bounds on f_PBH are obtained by jointly varying ΛCDM parameters, yielding f_PBH < 1.6 × 10^{-5} for a uniform distribution between 10^{15} and 10^{17} g.
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Dark Matter Energy Deposition and Production from the Table-Top to the Cosmos
The thesis presents a new 3-to-2 freezeout mechanism, bound-state effects on searches, a new axion interferometric search, reionization assessments, 21-cm constraints, and the DarkHistory code for ionization and thermal histories.
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Dark ages bounds on non-accreting massive compact halo objects
Upper bounds on the dark matter fraction in MACHOs of 10^3 to 10^7 solar masses are derived from limits on distortions to the global 21-cm signal at z~17, z~89, and z>300.
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Comparative Study of Early-Universe Epochs in an $f(R,L_m)$ Gravity Model with Effective Curvature--Matter Interaction and $\Lambda$CDM Cosmology
In an f(R, L_m) gravity model constrained by distance modulus data via chi-squared and MCMC, the authors report earlier nonlinear structure formation and higher matter-radiation equality redshift than Lambda CDM, with matching recombination redshift.