arXiv subjects

Cara Giovanetti

Publications and source records attributed to Cara Giovanetti.

10 recordsLinked to original sources

arXiv2026

The Role of Big Bang Nucleosynthesis in Joint Cosmological Analyses

We perform joint Baryon Acoustic Oscillation (BAO) + Big Bang Nucleosynthesis (BBN) and BAO+BBN+Cosmic Microwave Background (CMB) analyses with Planck CMB and DESI DR2 BAO data, explicitly marginalizing over BBN nuisance parameters for the first time with these data combinations and paying particular attention to the impact of BBN on these results. We find in our fiducial analyses $h=0.6833^{+0.0048}_{-0.0053}$ ($Λ$CDM, BAO+BBN), $h=0.6823^{+0.0027}_{-0.0026}$ ($Λ$CDM, BAO+BBN+CMB), as well as $h=0.6791^{+0.0069}_{-0.0075},N_{\rm{eff}}=2.974^{+0.098}_{-0.099}$ ($Λ$CDM+$N_{\rm{eff}}$, BAO+BBN), and $h=0.6838^{+0.0052}_{-0.0054},N_{\rm{eff}}=3.065^{+0.078}_{-0.076}$ ($Λ$CDM+$N_{\rm{eff}}$, BAO+BBN+CMB). We demonstrate how investigator choices can impact results of joint analyses involving BBN. We provide recommendations for the treatment of BBN in light of recent work, and demonstrate a pipeline that accurately accounts for prediction uncertainties in BBN.

astro-ph.CO↗

arXiv2026

ABCMB: A Python+JAX Package for the Cosmic Microwave Background Power Spectrum

We present ABCMB, a differentiable Einstein-Boltzmann solver for the cosmic microwave background (CMB). ABCMB is an analysis-ready code package capturing important effects to linear order in $Λ$CDM cosmology. It computes the CMB power spectrum and includes effects like lensing, polarization, massive neutrinos, and a state-of-the-art treatment of Big Bang Nucleosynthesis and recombination. ABCMB has sub-percent-level agreement with CLASS and can be run on a GPU with competitive, and sometimes even faster, run times, owing to ABCMB's favorable run time scaling with maximum multipole moment. It is refactored compared to previous codes and takes advantage of object-oriented programming to improve extensibility, meaning new physics can be added to it without the need for modifying source files. ABCMB provides accurate and stable gradients to the user, making Fisher analyses straightforward, and enabling the use of efficient gradient-based sampling methods.

astro-ph.CO↗

arXiv2026

A generic $ω_b$ tension in early-time solutions to the Hubble tension

I show that early-time (pre-recombination) solutions to the Hubble tension are generically expected to increase the preferred baryon density $ω_b$. This puts these models in tension with Big Bang Nucleosynthesis (BBN), as measurements of primordial deuterium constrain $ω_b$ at percent level. I show that existing analyses are in tension with the BBN determination of $ω_b$, and that including a likelihood component for primordial deuterium deters two representative models from recovering a high $H_0$.

astro-ph.CO↗

arXiv2026

A data-driven prediction for the primordial deuterium abundance

We predict the primordial deuterium abundance using a novel, fully data-driven approach, where we use Gaussian process regression to fit experimental nuclear reaction data for $d$,($d$,$n$)$^3$He, $d$,($d$,$p$)$t$, and $d$($p$,$γ$)$^3$He, three reactions to which the primordial deuterium abundance is most sensitive. Using the Planck determination of the baryon density, we predict $10^5\times\mathrm{D/H} = 2.442\pm0.040$ in standard Big Bang Nucleosynthesis, $1.70σ$ below the Cooke et al. measurement. Our result is consistent with predictions relying on first principles calculations of the deuterium burning cross sections. With the inferred baryon density from a combined fit to Planck, ACT DR6, and SPT-3G D1, this discrepancy worsens to $1.98σ$. We validate our approach and confirm that Gaussian processes make unbiased D/H predictions with appropriately-sized uncertainties. We repeat our validation tests for low-degree polynomial fits, a technique used in previous analyses, and find that they systematically over-predict D/H. Our results highlight the need for improved measurements of the $d$,($d$,$n$)$^3$He and $d$,($d$,$p$)$t$ S-factors at energies between 0.1 and 0.6 MeV.

astro-ph.CO↗

arXiv2025

LINX: A Fast, Differentiable, and Extensible Big Bang Nucleosynthesis Package

We introduce LINX (Light Isotope Nucleosynthesis with JAX), a new differentiable public Big Bang Nucleosynthesis (BBN) code designed for fast parameter estimation. By leveraging JAX, LINX achieves both speed and differentiability, enabling the use of Bayesian inference, including gradient-based methods. We discuss the formalism used in LINX for rapid primordial elemental abundance predictions and give examples of how LINX can be used. When combined with differentiable Cosmic Microwave Background (CMB) power spectrum emulators, LINX can be used for joint CMB and BBN analyses without requiring extensive computational resources, including on personal hardware.

astro-ph.CO↗

arXiv2025

Cosmological Parameter Estimation with a Joint-Likelihood Analysis of the Cosmic Microwave Background and Big Bang Nucleosynthesis

We present the first joint-likelihood analysis of Big Bang Nucleosynthesis (BBN) and Cosmic Microwave Background (CMB) data. Bayesian inference is performed on the baryon abundance and the effective number of neutrino species, $N_{\rm eff}$, using a CMB Boltzmann solver in combination with LINX, a new flexible and efficient BBN code. We marginalize over Planck nuisance parameters and nuclear rates to find $N_{\rm{eff}} = 3.08_{-0.13}^{+0.13},\,2.94 _{-0.16}^{+0.16},$ or $2.98_{-0.13}^{+0.14}$, for three separate reaction networks. This framework enables robust testing of the Lambda Cold Dark Matter paradigm and its variants with CMB and BBN data.

astro-ph.CO↗

arXiv2025

Orbital Dynamics of the Solar Basin

We study the dynamics of the solar basin -- the accumulated population of weakly-interacting particles on bound orbits in the Solar System. We focus on particles starting off on Sun-crossing orbits, corresponding to initial conditions of production inside the Sun, and investigate their evolution over the age of the Solar System. A combination of analytic methods, secular perturbation theory, and direct numerical integration of orbits sheds light on the long- and short-term evolution of a population of test particles orbiting the Sun and perturbed by the planets. Our main results are that the effective lifetime of a solar basin at Earth's location is $τ_{\rm eff} = 1.20\pm 0.09 \,\mathrm{Gyr}$, and that there is annual (semi-annual) modulation of the basin density with known phase and amplitude at the fractional level of 6.5% (2.2%). These results have important implications for direct detection searches of solar basin particles, and the strong temporal modulation signature yields a robust discovery channel. Our simulations can also be interpreted in the context of gravitational capture of dark matter in the Solar System, with consequences for any dark-matter phenomenon that may occur below the local escape velocity.

hep-ph↗

arXiv2024

Neutrino-Dark Sector Equilibration and Primordial Element Abundances

After neutrinos decouple from the photon bath, they can populate a thermal dark sector. If this occurs at a temperature above ~100 keV, this can have measurable impacts on light element abundances. We calculate light element abundances in this scenario, studying the impact from rapid cooling of the Standard Model neutrinos, and from an increase in the number of relativistic degrees of freedom $N_{\rm{eff}}$, which can occur in the presence of a mass threshold. We incorporate these changes in the publicly available BBN code PRIMAT, using the reaction networks from PRIMAT and from the BBN code PArthENoPE, to calculate Y$_{\rm{P}}$ and D/H. We provide limits from the two different reaction networks as well as with expanded errors to include both results. If electron neutrinos significantly participate in the cooling, we find limits down to temperatures as low as 100 keV. If electron neutrinos are weakly participating (for instance if only the mass eigenstate $ν_3$ equilibrates), cooling places no limits. However, if the dark sector undergoes a "step" in $N_{\rm{eff}}$, there can be additional, $ω_b$-dependent constraints. These limits can vary from strong (for low values of $ω_b$) to a mild preference for new physics (for high values of $ω_b$). Future analyses including upcoming CMB data should improve these limits.

hep-ph↗

arXiv2022

Joint CMB and BBN Constraints on Light Dark Sectors with Dark Radiation

Dark sectors provide a compelling theoretical framework for thermally producing sub-GeV dark matter, and motivate an expansive new accelerator and direct-detection experimental program. We demonstrate the power of constraining such dark sectors using the measured effective number of neutrino species, $N_\text{eff}$, from the Cosmic Microwave Background (CMB) and primordial elemental abundances from Big Bang Nucleosynthesis (BBN). As a concrete example, we consider a dark matter particle of arbitrary spin that interacts with the Standard Model via a massive dark photon, accounting for an arbitrary number of light degrees of freedom in the dark sector. We exclude dark matter masses below $\sim$ 4 MeV at 95% confidence for all dark matter spins and dark photon masses. These bounds hold regardless of additional new light, inert degrees of freedom in the dark sector, and for dark matter-electron scattering cross sections many orders of magnitude below current experimental constraints. The strength of these constraints will only continue to improve with future CMB experiments.

hep-ph↗

arXiv2019

Dynamical Friction in a Fuzzy Dark Matter Universe

We present an in-depth exploration of the phenomenon of dynamical friction in a universe where the dark matter is composed entirely of so-called Fuzzy Dark Matter (FDM), ultralight bosons of mass $m\sim\mathcal{O}(10^{-22})\,$eV. We review the classical treatment of dynamical friction before presenting analytic results in the case of FDM for point masses, extended mass distributions, and FDM backgrounds with finite velocity dispersion. We then test these results against a large suite of fully non-linear simulations that allow us to assess the regime of applicability of the analytic results. We apply these results to a variety of astrophysical problems of interest, including infalling satellites in a galactic dark matter background, and determine that \emph{(1)}~for FDM masses $m\gtrsim 10^{-21}\, {\rm eV}\, c^{-2}$, the timing problem of the Fornax dwarf spheroidal's globular clusters is no longer solved and \emph{(2)}~the effects of FDM on the process of dynamical friction for satellites of total mass $M$ and relative velocity $v_{\rm rel}$ should require detailed numerical simulations for $\left(M/10^9~M_{\odot}\right) \left(m/10^{-22}~{\rm eV}\right)\left(100~{\rm km}~{\rm s}^{-1}/v_{\rm rel}\right) \sim 1$, parameters which would lie outside the validated range of applicability of any currently developed analytic theory, due to transient wave structures in the time-dependent regime.

astro-ph.CO↗