Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2611.03761

De-lensing cosmic birefringence with joint reconstruction

Sebastian Belkner·Julien Carron
View original source ↗Read source document ↗Export metadata ↓

Abstract

Reconstruction of anisotropic cosmic birefringence from the CMB is limited by lensing $B$-mode sample variance and partially degenerate with the lensing curl. We study the joint reconstruction of lensing (gradient and curl) and birefringence at the maximum-a-posteriori point, whose spectra are near-optimal statistics. We predict the joint response and noise analytically, validate them on simulations, and show unbiased inference of its amplitude. Errors will shrink $5$-fold relative to quadratic estimators at SPT-3G+ depths, promising much tighter constraints on parity-violating new physics, owing to the removal of the lensing $B$-polarization sample variance.

Explore related subjects

astro-ph.CO

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Sebastian Belkner, Julien Carron. 2026-11-02. De-lensing cosmic birefringence with joint reconstruction. https://arxiv.org/abs/2611.03761

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Universality of Primordial Anisotropies in Gravitational Wave Background

We investigate the general structure of primordial anisotropies in the stochastic gravitational-wave background (SGWB). Many mechanisms generating primordial SGWB anisotropies, including fossil and propagation effects, exhibit similar multipole dependences despite their distinct physical origins, implying the presence of a common underlying structure. To characterize this structure, we introduce a model-independent framework, the Cosmological Form Factor (CFF), that describes how long-wavelength perturbations modulate short-scale SGWB statistics. Within this broad class of mechanisms, we show that the allowed angular and polarization structures of SGWB anisotropies are universally determined by general principles, including statistical isotropy, locality, and the basic properties of long-wavelength perturbations. In contrast to these universal structures, observables such as amplitudes and frequency dependence retain information about the origin. Our results provide a unified and effective description of primordial SGWB anisotropies, clarifying which aspects are universal and which are model dependent, and therefore offer a theoretical foundation for interpreting future gravitational-wave observations.

astro-ph.CO↗
arXiv2026

CMB Spectral Distortions from Resonant Conversions in Atomic Dark Sectors

Dark sectors consisting of atomic constituents (electrons, protons, and photons) offer a well-motivated extension to the Standard Model while providing multiple avenues for phenomenological study. In this work, we explore the impact of conversions between the dark and Standard Model photons in the primordial CMB spectral distortion epoch ($10^3 \lesssim z \lesssim 10^6$). These conversions are resonantly enhanced when the induced thermal masses of both photonic species are equal, thus leading to the possibility that sizeable distortions can be produced. To this end, we solve the Boltzmann equation at early times to determine the (irreducible) freeze-in or freeze-out abundance of dark photons. This procedure also allows us to update the limits on generic milli-charged dark sectors using the ACT DR6 bound on the number of effective radiative degrees of freedom ($N_{\rm eff}$). By then modeling the evolution of the thermal masses in both sectors, we compute the primordial CMB distortion using the Landau-Zener formalism. We find that when the dark electron and proton are roughly similar in mass (the positronium limit), current spectral distortion data from the COBE/FIRAS instrument is able to rule out novel regions of parameter space. We also forecast bounds from the proposed FOSSIL satellite, finding that spectral distortions can also be used to probe the ultra-low dark electric charge regions of parameter space, which are difficult to investigate by other means.

astro-ph.CO↗
arXiv2026

Cosmology of Inelastic Self-Interacting Dark Matter: Linear Evolution and Observational Constraints

We study the linear cosmological evolution of inelastic self-interacting dark matter in a two-component dark sector with a small mass splitting, assuming thermal initial conditions for the two species. We derive the coupled background and perturbation equations for inelastic conversion between the two species, considering both power-law and low-velocity saturation cross sections. Exothermic conversion injects kinetic energy into the light component, generating pressure support that suppresses small-scale structure and produces dark acoustic oscillations in the matter power spectrum. The resulting cutoff at scale $k > 1\,h\,\mathrm{Mpc}^{-1}$ depends on the normalization and velocity dependence of the cross section, the dark matter mass and the mass splitting. Using linear power spectra computed with a modified Boltzmann solver, we apply recast constraints from Lyman-$α$ forest data and high-redshift UV luminosity functions, finding non-monotonic but closed exclusion regions driven by the competition between efficient conversion and rapid depletion of the heavy component. These results show that the internal thermodynamics of a secluded multi-component dark sector can leave observable imprints on structure formation, providing a complementary probe of secluded dark matter.

astro-ph.CO↗