arXiv subjects

Duncan K. Adams

Publications and source records attributed to Duncan K. Adams.

4 recordsLinked to original sources

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

Semi-Analytic Predictions for Strong-Lensing Perturbers in Cold and Self-Interacting Dark Matter

Strong gravitational lensing is sensitive to the abundance and internal structure of dark matter halos, providing a probe of gravothermal evolution in self-interacting dark matter (SIDM). We combine semi-analytic cold dark matter (CDM) subhalo histories with a model for gravothermal evolution in SIDM to generate CDM and SIDM subhalo populations across SIDM parameter space. We predict their projected enclosed masses and deflection-based projected density slopes and compare them with three perturbers inferred through gravitational imaging in PJ011646, SDSS J0946+1006, and JVAS B1938+666. For SIDM model parameters $σ_0/m_χ=147.1$ cm$^2$/g and $w=120$ km/s, SIDM subhalos reproduce all three perturbers more often than CDM subhalos. For PJ011646, we find ~0.6 cored SIDM subhalos per host matching the perturber, compared with ~0.002 in CDM, while core-collapsed subhalos are too steep. For SDSS J0946+1006, we find ~3 core-collapsed and ~0.004 cored SIDM subhalos per host, compared with none in 900 CDM realizations, although baryons, neglected here, may matter for such massive subhalos. For "detection V" in JVAS B1938+666, we find ~220 core-collapsed and ~20 cored SIDM subhalos per host within the $2σ$ posterior region, compared with ~0.2 in CDM; the CDM candidates require exceptionally early accretion, at median redshift $z\sim13$. Simultaneously reproducing all three perturbers requires $w\gtrsim10^2$ km/s, so that the massive (~$5.6\times10^{10}M_\odot$) progenitors of SDSS J0946+1006 candidates can collapse, and is achieved for $σ_0/m_χ\gtrsim10^2$ cm$^2$/g in the parameter sets studied. Our results show how semi-analytic models can quantify how often subhalos reproduce individual perturbers in different dark matter models, and our modular framework can be readily updated as models of tidal stripping and late-stage gravothermal evolution in SIDM improve. (abridged)

astro-ph.CO↗

arXiv2026

Auditing anapole dark matter: the limits of model independence in dark matter effective field theory

Effective field theory is a powerful tool for studying the low-energy behavior of dark sector models without explicit dependence on the high-energy physics. However, bottom-up EFT analyses can miss important processes in UV completions that are relevant for dark matter production and detection. In this work we demonstrate explicitly that for Majorana dark matter coupled to the photon by the dimension-six anapole operator, different UV completions make qualitatively different predictions at high energy colliders, in the early universe, and in direct detection experiments. Additionally, we show that competitive, and in some cases, leading constraints on anapole dark matter can be derived by searching for signatures of additional particles in the UV completion rather than direct probes of the DM itself. We argue that the UV completions studied in this work have categorically different phenomenologies and that `model-independent' EFT constraints are not always applicable.

hep-ph↗

arXiv2026

Semi-Analytic Modeling of Dark Matter Subhalo Encounters with Thin Stellar Streams: Statistical Predictions for GD-1-like Streams in CDM

Stellar streams from disrupted globular clusters are dynamically cold structures that are sensitive to perturbations from dark matter subhalos, allowing them in principle to trace the dark matter substructure in the Milky Way. We model, within the context of $Λ$CDM, the likelihood of dark matter subhalos to produce a significant feature in a GD-1-like stream and analyze the properties of such subhalos. We generate many realizations of the subhalo population within a Milky Way mass host halo using the semi-analytic code SatGen, accounting for effects such as tidal stripping and dynamical friction. The subhalo distributions are combined with a GD-1-like stream model, and the impact of subhalos that pass close to the stream are modeled with Gala. We find that subhalos with masses in the range $2\times 10^6 M_{\odot} - 10^8 M_{\odot}$ at the time of the stream-subhalo encounter, corresponding to masses of about $2 \times 10^7 M_{\odot} - 10^9 M_{\odot}$ at the time of infall, are the likeliest to produce gaps in a GD-1-like stream. We find that gaps occur on average $\sim$3~times per realization of the host system. These gaps have typical widths of $\sim(5 - 27)$~deg and fractional underdensities of $\sim (10 - 30)\%$, with larger gaps being caused by heavier subhalos. The stream-subhalo encounters responsible for these have impact parameters $(0.1 - 1.5)$~kpc and relative velocities $\sim(200 - 410)$~km/s. We also investigate the effects of increasing the host-halo mass on the gap properties and formation rate.

astro-ph.GA↗