Papers

What if dark energy is recurrent throughout cosmic history? In this picture, episodes of scalar-field dark energy become less surprising and more natural features of cosmic evolution. We construct a homogeneous multi-axion cosmology with a transient contribution during Big Bang nucleosynthesis, two early dark energy components before recombination, and a thawing field that supplies the present dark-energy density. As Hubble friction weakens, the fields begin to roll at successive epochs set by their potential-curvature scales. Their initial displacements affect the rolling delays and peak energy fractions. The transient fields have third-power cosine potentials, whose sextic minima allow faster-than-radiation dilution during rapid, small-amplitude oscillations. All four fields are evolved in a common Friedmann background, with their first roll and subsequent dynamics resolved numerically. With reference matter and radiation densities taken from Planck 2018, the benchmark has a nucleosynthesis-era peak fraction of approximately $0.99\%$ near $z=10^9$. The two early dark energy fields peak near $z=7.9\times10^3$ and $2.4\times10^3$, with individual fractions of $8.6\%$ and $7.8\%$; their combined fraction reaches $9.7\%$. The late-time field is normalized to supply a present fraction of approximately $0.685$, while the three transients leave a combined fraction of approximately $6.0\times10^{-7}$. An aligned two-axion example illustrates the enhanced field range available for an inflationary extension. We also outline how searches for transient contributions to the expansion rate at other epochs could constrain additional axion scales.

Primordial Black Holes (PBHs) with masses below $\mathcal{O}(10^9)$g occupy an interesting region of parameter space that is largely inaccessible to conventional observations. Despite evaporating before Big Bang Nucleosynthesis (BBN), these PBHs can naturally generate a period of early matter domination in the early Universe. A primordial gravitational-wave background (GWB) provides a window onto this otherwise inaccessible regime, since the modified expansion history leaves a characteristic spectral feature associated with the onset and end of PBH domination. The locations of these characteristic frequencies can be used to reconstruct the underlying PBH parameters, in particular the PBH mass. For a freely propagating GWB, the location of these frequencies additionally allow the initial PBH abundance to be determined. We derive simple numerical relations that map these characteristic frequencies directly onto the PBH mass and initial abundance. Future GW experiments span a vast frequency range, providing sensitivity to PBH masses from the BBN bound of $\mathcal{O}(10^9)\,\mathrm{g}$ down to the lower bound of $\mathcal{O}(10)\,\mathrm{g}$. We find that the nanohertz signal reported by NANOGrav, if primordial in origin, is already probing PBH masses in the range $4$–$90\,\mathrm{Mg}$. GW observations therefore offer access to a vast region of PBH parameter space that is otherwise beyond the reach of current experiments.

Naive estimates based on Einstein gravity with Lagrangian $\frac{1}{2}M_{pl}^{2}(R-2\Lambda)$ suggest that, if the radiation era extended back to the Big Bang (i.e., as far back as the classical spacetime background makes sense), this would result in an over-production of dark matter and a relic cosmic background of thermal gravitons. Here we revisit these conclusions in quadratic gravity, the minimal renormalizable completion of Einstein gravity, whose Lagrangian also includes the terms $\frac{1}{6}f_0^{-2}R^2-\frac{1}{2}f_{2}^{-2}C^{2}$. Assuming the radiation era does extend back to the bang, we find a novel relation between the coefficient $f_{2}$ and the dark matter mass $m_{dm}$, needed to obtain the correct dark matter abundance. This yields a new gravitational production mechanism for dark matter (e.g., stable right-handed neutrinos). Moreover, the presence or absence of the relic graviton background (detectable by forthcoming CMB experiments via its small imprint on $N_{{\rm eff}}$) will place new constraints on $f_{0}, f_{2}$.

The distribution of matter along the same line of sight but external to the main lens, quantified by $\kappa_\mathrm{ext}$, is a key source of uncertainty in time delay cosmography and other applications of strong lensing, and must be independently estimated to avoid biasing the inferred value of the Hubble constant ($H_0$). We present advancements and standardisations in the weighted number counts techniques used to constrain $\kappa_\mathrm{ext}$, in particular the use of the Euclid Flagship Simulation and a breakdown of the line-of-sight contributions between the observer, lens and source. As part of the TDCOSMO 2026 milestone analysis, we apply this updated method to the sample of 11 time delay lenses used in that study. Our estimates for certain systems are sensitive to these methodological changes, but are nonetheless consistent within $1\sigma$ for all but one of the systems which had been studied previously, with the median $\kappa_\mathrm{ext}$ across those systems changing from $-0.002$ to $-0.006$ following this new analysis. This work represents the first estimate of $\kappa_\mathrm{ext}$ values which includes the contribution of the observer-lens and lens-source terms, and largest standardised analysis of time delay lens environments to date.

We constrain the particle mass of the fuzzy dark matter model using globular cluster candidates in dwarf galaxies, from the Euclid Early Release Observations, within the Fornax and Perseus galaxy clusters. We model the orbital evolution of globular clusters by combining fuzzy dark matter density profiles with the corresponding dynamical friction formalism, and integrate their orbits using galpy. In the fuzzy dark matter framework, both the halo density profile and the dynamical friction force are modified by the wave-like nature of the ultra-light dark matter particle, whose mass is parameterized as $m_{22}=m_\chi/10^{-22},\mathrm{eV}$ and explored over the range $0.1 \leq m_{22} \leq 100$. This framework naturally alleviates the long-standing globular cluster timing problem originally identified in the Fornax dSph. We find that globular clusters no longer experience orbital decay toward the centers of their host galaxies for $m_{22}\leq1.46^{+0.51}_{-0.32}$ in the Fornax cluster and $m_{22}\leq1.09^{+0.14}_{-0.21}$ in the Perseus cluster. Future Euclid data releases, providing substantially larger samples of globular cluster candidates, will enable significantly tighter constraints on the dark matter particle mass within the fuzzy dark matter scenario.

Initial spatial clustering of primordial black holes (PBHs) induced by local-type non-Gaussianity (LNG) can substantially modify cosmological constraints on PBH abundance. Several inflationary scenarios that enhance curvature perturbations at small scales relevant to PBH formation predict LNG that is not necessarily perturbative. Therefore, it is crucial to establish a theoretical framework capable of investigating the initial clustering induced by arbitrary LNG. Here, we present a general analytical formulation for the PBH two-point correlation function applicable to arbitrary LNGs in the alternative approach. Under the assumptions that PBHs form only at the large peaks of perturbations, and that large-scale modes weakly modulate the local variance of small-scale perturbations, we derive an analytic expression for the PBH bias parameter, directly connecting initial clustering to the primordial trispectrum in the collapsed limit. We demonstrate the versatility of our formula by computing the bias parameters in the ultra-slow-roll inflation, curvaton, and modulated reheating scenarios. We also formally generalize the framework to broad power spectra to account for correlations across different PBH mass scales. Because our formulation does not rely on weak or perturbative non-Gaussianity assumptions, our result provides a universal theoretical basis for evaluating initial clustering impact on PBH observables.

We realize a nearly pure higgsino dark matter candidate with mass of about 1 TeV in the Minimal Supersymmetric Standard Model coupled to the Starobinsky supergravity. The recent LUX-ZEPLIN 248 keV nuclear-recoil event has renewed interest in higgsino dark matter. In this framework, the particle spectrum, including the Higgs boson mass, the higgsino mass and its splitting, is connected to cosmic inflation observables via gravitational mediation of supersymmetry breaking and subsequent renormalization group evolution. We show that the Higgs boson mass predicted by the model agrees with the measured value within the quoted uncertainties for a broad range of bino-induced mass splittings. Wino-induced splitting leads to a Higgs mass several GeV higher and is therefore excluded.

The aperture mass filter is a widely used tool in weak lensing studies. While previous surveys have typically relied on the flat-sky approximation, forthcoming Stage IV surveys such as Euclid will cover sufficiently large areas to require the construction of curved-sky aperture mass maps. In this paper, we extend the shear-based aperture mass formalism to the sphere and introduce a software package for a fast and precise computation of spherical aperture mass maps from the shear field, defined directly on the celestial sphere. Unlike existing approaches, our method does not rely on planar projections and does not require the reconstruction of convergence maps. The software provides four different implementations, all of which are independent of the choice of aperture mass filter function. Starting from the brute-force approach, whose computational cost renders it impractical for future surveys covering more than 10,000 deg2, we investigate alternative galaxy-grouping strategies to improve computational efficiency. We demonstrate speed-up factors of up to 40 at a resolution of NSIDE = 4096 while achieving significantly higher precision than existing state-of-the-art methods. In particular, we show that the spherical shear-based implementations using a pixel-based approach outperforms the existing methods in terms of both precision and computational time. Finally, we show that, for weak-lensing cluster detection, the cluster sample produced using the spherical shear-based aperture mass method consistently outperforms those obtained using projected shear-based approaches in the purity-completeness plane, while simplifying the resulting selection function. Our spherical mass aperture software, called SMART, is made available on GitHub.

The cosmological evolution of ultralight axions typically involves rapid oscillations on the timescale of the inverse mass, making it challenging to resolve the dynamics at both the background and perturbation levels. In this study, we numerically implement a novel approach to this problem based on an effective field theory (EFT) – that is, for the first time, capable of reconstructing the relativistic oscillations intrinsic to the axion field. Compared to other available techniques, the reconstruction of the rapid oscillations is unique to the EFT approach, which describes the axion effective field through a wavefunction representation with relativistic corrections, rather than through effective fluid variables. From a computational standpoint, our approach archives a high level of accuracy – up to a subpercent agreement with the exact solution – while remaining relatively fast compared to alternative methods. As such, it opens up new possibilities for high-precision predictions for axion searches with future cosmological experiments.

In this work, we present a formalism to model the relativistic behavior of axions. The relativistic behavior of axions is surprisingly difficult to model precisely, as it involves oscillations on timescales much shorter than the Hubble timescale. To overcome this challenge, one typically resorts to some form of effective treatment, focusing only on the time-averaged description of the exact oscillations. Salehian, Namjoo & Kaiser provide a systematic framework for such treatment, based on the effective field theory formalism. While the aforementioned study was formulated for axion perturbations in the Newtonian gauge with no anisotropic stress, we extend the formalism to the synchronous gauge that is more conventionally used for numerical implementation in a realistic cosmological setting. Unlike their work, however, we propose a fluid interpretation in which the axion field can be identified as a perfect fluid at all times, both in the exact and effective regimes. Moreover, we present the effective field theory for the Newtonian gauge with non-zero anisotropic stress, making the original formulation more general and useful for scenarios where the matter content of the universe is multi-component. These results lay the theoretical foundation for a companion paper where we discuss how the axion field should be incorporated alongside other species in common cosmological Boltzmann solvers.

We present a family of plateau-type inflationary potentials, eq.~\eqref{Vgeneral}, and analyze a two-parameter $\alpha\beta$-Starobinsky specialization that interpolates continuously between a maximal plateau ($V\!\to\!V_0$) and a submaximal plateau ($V\!\to\!V_\infty<V_0$), where $V_0$ is the overall scale of the potential. In the $\beta\!\to\!0$ limit our framework reproduces the $\alpha$-Starobinsky predictions $n_s\simeq 1-2/N_\star$ and $r\simeq 12\alpha/N_\star^2$. For $\beta>0$ with $x_\star\gg 1/\beta$ the slow-roll scaling laws change to $n_s\simeq 1-\frac{4}{3N_\star},\, r\simeq\mathcal{C}(\alpha,\beta)\,N_\star^{-4/3},$ with an explicit coefficient $\mathcal{C}(\alpha,\beta)$ set by the plateau truncation. This deformation lifts $n_s$ at fixed $N_\star$ while further suppressing $r$, reconciling the Planck~2018 constraint $n_s=0.9649\pm0.0042$ (68% CL) and BICEP/Keck18 data $r_{0.05}<0.036$ (95% CL), with the higher central values $n_s\sim0.97$–$0.98$ preferred by ACT+DESI~DR2 (BAO), within the theoretically motivated interval $N_\star\in(50,60)$ and without exotic reheating. We provide an exact identity for $V/V'$ enabling analytic control of $N_\star$, a practical crossover criterion $\beta\,x_\star\ll1$ vs.\ $\gg1$, and a transparent mapping between $(\alpha,\beta)$ and the observables $(n_s,r,N_\star)$. These yield sharp, testable signatures, particularly the softened $N_\star$-scaling of $r$, that distinguish a maximal from a submaximal plateau with upcoming CMB and LSS data.

Primordial black holes (PBHs) are a well-motivated dark matter candidate, and their cosmic abundance is constrained by a variety of observational probes. PBHs in the mass range $10^{15}\,\text{g}\,{-}\,10^{17}\,\text{g}$ are evaporating today via Hawking radiation, a process that can heat interstellar dust and modify its thermal emission. Recent studies have used this effect to place constraints on the abundance of non-spinning PBHs. We extend this approach by investigating the influence of PBH spin on dust-heating constraints. Furthermore, we account for secondary photons that originate not only from the decay of gauge bosons but also from the decay of hadrons produced via the fragmentation of primary quarks and gluons emitted through Hawking radiation. By comparing the dust heating rate induced by spinning PBHs with the maximum cooling rate of dust, considering both silicate and graphite grains, we derive new upper limits on the fraction of dark matter in the form of PBHs, $f_{\rm PBH}$. Our results show that the constraints depend on both PBH mass and spin. Smaller PBHs with higher spin yield stronger limits. For example, in the cases we investigated, the strongest constraint is $f_{\rm PBH} \sim 1.5 \times 10^{-4}$ for $M_{\rm PBH} = 10^{15}{\rm g}$ and spin parameter $a_{*} = 0.9999$. Although these limits are less stringent than existing constraints in the same mass range, they provide a distinct and complementary approach to constraining the abundance of PBHs.

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) is expected to significantly advance the study of Milky Way stellar streams. In particular, the deep, precise photometry from LSST should greatly increase the statistical sensitivity to density fluctuations in stellar streams, which can be used to probe the small-scale distribution of dark matter. However, current forecasts generally neglect the impact of observational systematics that will be imprinted on stream density measurements. In this study, we develop a realistic forward-modeling framework to inject stellar streams into LSST-like observations including photometric uncertainties, survey depth variations, background contamination, and imperfect star-galaxy classification. We develop a likelihood-ratio analysis to assess the detectability of gaps in stellar streams in the presence of these observational systematics. In the presence of realistic survey systematics, we find that after four years of operations, LSST will be sensitive to density reductions of $\sim50\%$ for gaps with widths of $5$ deg in streams with surface brightness of $\sim33$ mag arcsec$^{-2}$. Relative to the ideal case, this corresponds to a degradation in gap depth sensitivity by a factor of $\sim5$ due to the combined impact of background contamination and observational systematics. Assuming a simplified analytical mapping between gap depth and dark matter subhalo properties, these estimates correspond to a minimum detectable subhalo mass of $\sim1\times10^7$ M$_\odot$. Observational effects shift this accessible mass scale upward by a factor of $\sim16$, with background contamination contributing a factor of $\sim5$ and survey systematics a further factor of $\sim3$, dominated by star-galaxy classification.

We carry out a search for the relative baryon-cold dark matter (CDM) density and velocity modes in the DESI full-shape (FS) data, and investigate whether DESI's preference for evolving dark energy can be affected by these relative perturbations, which are a known contaminant of the baryon acoustic oscillations. For the first time, we use a holistic effective field theory (EFT) treatment of the power spectrum and bispectrum both for the standard terms (without relative perturbations), modeled in EFT to one-loop order, and for the relative perturbations. For the latter we implement an efficient computation of the one-loop power spectrum that allows us to scan over different cosmologies. We obtain robust constraints on the relative density and velocity bias parameters $b_{\delta_{bc}}$, and $b_{v^2_{bc}}$ for all the DESI DR1 tracers, finding e.g. $b_{\delta_{bc}}=5 \pm 6$, $b_{v^2_{bc}}=-0.031\pm 0.023$ (at 68% CL) for the LRG2 sample in a DESI FS-only analysis within $\Lambda$CDM, supplemented by CMB priors on the baryon density and spectral tilt. Assuming instead a $w_0w_a$CDM cosmological model, and combining DESI FS with the CMB primary anisotropies, CMB lensing, and Pantheon+ supernovae, our LRG2 constraints read $b_{\delta_{bc}}=2 \pm 5$, $b_{v^2_{bc}}=-0.032\pm 0.022$. Adding the relative velocity divergence biases we find $b_{\delta_{bc}}=-17_{-17}^{+19}$, $b_{\theta_{bc}}=-760_{-680}^{+700}$, $b_{v^2_{bc}}=-0.032\pm 0.024$ for the same sample. The constraints on the dark energy equation of state parameters are virtually unchanged when marginalizing over the baryon-CDM modes. We conclude that DESI's preference for evolving dark energy is robust with respect to the baryon-CDM relative perturbations.

Recent multiwavelength observations of galaxy group and cluster gas suggest stronger baryonic feedback than our best-calibrated hydrodynamical simulations produce, while modeling this feedback remains a primary source of uncertainty in Stage-IV weak-lensing (WL) analyses. We present a suite of ray-traced maps generated with BIND (Baryonic INpainting with Deep learning), a conditional flow-matching model that paints baryonic mass and gas thermodynamics onto the halos of dark-matter-only simulations, and which was developed in a companion paper. Applied to IllustrisTNG300-Dark and ray-traced, we generate convergence, optical depth, and Compton-$y$ maps at five source redshifts, each with $1000$ pseudo-independent realizations. We build lightcones across a 256-node Sobol sequence spanning the thirty-dimensional IllustrisTNG galaxy formation prior, with individual parameter variations and at the fiducial model. In validation, the maps match those built from the IllustrisTNG300 halos to within LSST-Y10-like precision for a range of WL statistics. Across the prior, the response to feedback exceeds Stage-IV statistical precision by more than an order of magnitude on small scales, and different statistics respond to different model sectors: galactic winds control the WL power spectrum and gas auto- and cross-spectra, while the stellar initial mass function slope and AGN parameters shape the morphological statistics (PDF, peaks, minima, and Minkowski functionals). Finally, we find that the response of statistics can be compressed into seven halo properties which linearly predict a range of WL and SZ statistics. We publicly release the maps, statistics, and model tables.

Baryonic feedback is a dominant source of systematic uncertainty for upcoming weak-lensing surveys, but current tools for modeling its effect rely on spherical approximations and density profiles calibrated almost entirely on two-point statistics. We introduce BIND (Baryonic INpainting with Deep learning), a conditional flow-matching model that learns a field-level mapping from dark-matter-only halos to their hydrodynamical counterparts. BIND is trained on halos from the 1024 paired hydrodynamical and dark-matter-only simulations of the CAMELS $50\,h^{-1}\,\mathrm{Mpc}$ SB35 suite and samples dark matter, gas, and stellar mass fields over redshift across the full 35-dimensional $\Lambda$CDM and IllustrisTNG galaxy formation parameter space. BIND recovers dark matter, gas, and stellar masses at the percent level, reproduces azimuthally averaged profiles to $\lesssim10\%$ at all radii, and matches halo shape distributions with high fidelity. The learned parameter dependence captures the rank correlations between the generated fields and the subgrid parameters, and the field-level response to individual parameter variations is recovered in both sign and morphology. Halo mass is never supplied as conditioning, yet the baryon fraction, stellar-to-halo mass relation, inter-component scaling relations, and the joint covariance of their residuals are all reproduced. We finally show that, applied halo-by-halo to a $(50\,h^{-1}\,\mathrm{Mpc})^3$ $N$-body volume with $512^3$ particles, BIND reproduces the projected matter power spectrum suppression to the accuracy ceiling set by pasting in the hydrodynamical halos themselves, in minutes on one GPU. We release the trained BIND models and all generated halos as open-source tools. A companion paper extends BIND to thermodynamic fields and non-Gaussian weak-lensing statistics.

We investigate the internal structure of two galaxies from the LEWIS sample: the ultra-diffuse galaxy UDG-1 and the extended dwarf LSB-6. Both show coherent stellar rotation combined with a non-negligible fraction of random motion, with no signs of ongoing disturbance. This is the first attempt to constrain the dynamics and dark matter physics of rotation-supported UDGs through integral-field stellar kinematics. We model the galaxies as stellar spheroids with typical dwarf-like thickness embedded in spherical dark matter halos, deriving two-dimensional velocity fields that we compare with the observations in a Bayesian framework. Besides cold dark matter, we test fuzzy, self-interacting, and non-minimally coupled dark matter. The data prefer a cuspy halo in UDG-1 and a cuspless one in LSB-6. All the alternative models remain viable, although current data cannot conclusively discriminate among them. For fuzzy dark matter we obtain mutually consistent boson masses, $m_\alpha = 4.7^{+1.8}_{-1.1} \times 10^{-22}$ eV for UDG-1 and $m_\alpha = 6.3^{+0.4}_{-0.4} \times 10^{-22}$ eV for LSB-6. For self-interacting dark matter, LSB-6 yields a robust constraint on the velocity-weighted cross section, $\langle \sigma v\rangle/m = 14.3^{+2.0}_{-1.9}$ cm$^2$ km g$^{-1}$ s$^{-1}$. For non-minimally coupled dark matter we derive upper bounds on the coupling length, implying marginal deviations from $\Lambda$CDM. Regardless of the model, both galaxies exhibit a dark matter content comparable with halos of typical dwarf galaxies with similar stellar masses. Together with stellar population analyses and globular cluster information, these results support a scenario in which UDG-1 and LSB-6 originate from puffed-up dwarfs. This work is the first in a series exploiting kinematic data of extremely low-surface-brightness galaxies to test fundamental physics, from dark matter to modified theories of gravity.

The growth of primordial black holes through the absorption of the surrounding plasma has recently been shown to exhibit a critical behavior during radiation domination. We extend this analysis to the reheating era and derive analytical solutions for general reheating histories. We show that reheating modifies the critical condition for runaway absorption, making it dependent on both the reheating dynamics and the black-hole formation time. We identify two distinct regimes: runaway growth occurring during reheating, or being triggered after the onset of radiation domination by the mass accumulated during reheating. More generally, we derive a simple composition law describing how independent mass- growth mechanisms combine across successive cosmological eras. Applying it to radiation absorption and inflaton accretion, we obtain analytical results in excellent agreement with the full numerical evolution.

The Sommerfeld enhancement (SE) from long-range interactions, and the related bound state formation rate, can be important non-perturbative inputs to dark matter (DM) annihilation signals. In the presence of singular interaction potentials, the conventional boundary conditions of the Schrödinger equation fail, obfuscating the computation of SE, its physical origin, and its relation to bound states in such potentials. In this work, we clarify the origin of SE in singular potentials in a two-fold manner: using the framework of velocity power counting in non-relativistic effective field theory (NREFT), and via position-space regularization of singular potentials at short distances to compute SE and bound states. We illustrate our findings through the case of pseudoscalar mediators interacting with massive Dirac DM. We find that when such a system arises from a UV-complete theory at weak coupling, no SE is generated. However, in the case of a derivatively coupled pseudoscalar, where the interaction is described by a higher-dimension operator in an effective theory, SE (and bound states) can occur for weak couplings if there is a large hierarchy between the cutoff scale of the effective theory and the dark matter mass. This SE is sensitive to the choice of the UV completion of the potential at short distances, but a non-negligible SE can persist even when the UV physics alone would not generate any SE; we elucidate the interplay of UV and IR physics in this case.

An eV-scale QCD axion comprising the observed dark matter (DM) abundance is expected to generate a photon line at infrared energies that would be observable or near-observable in data collected by the James Webb Space Telescope (JWST), as might more general axion-like particles (ALPs) over a broader range of masses and couplings. This has motivated a number of efforts to either forecast JWST sensitivities to a QCD axion or realize them through analyses of publicly available datasets. At present, no consensus exists; leading analyses disagree by as much as an order of magnitude in terms of axion-coupling sensitivity, implying an orders-of-magnitude discrepancy in raw flux density sensitivity, and consistency between the analyses and prior forecasts is unclear. We address these outstanding discrepancies with a bespoke data reduction and flexible nonparametric inference procedure that lead to well-controlled and robust limits on the decay of eV-scale axion DM, consistent with previously forecasted sensitivities. We further demonstrate that the strongest previously claimed sensitivities exceed those attainable by any analysis of the datasets from which they were derived. We exclude QCD axion DM for masses between $500\,\mathrm{meV}$ and $2.5\,\mathrm{eV}$ using NIRSpec data, while setting limits on ALP DM complementary to other astrophysical constraints at masses between $100\,\mathrm{meV}$ and $500\,\mathrm{meV}$. However, we find the sensitivities to be systematically limited, and therefore unlikely to be improved upon by ongoing data collection or re-analysis unless instrumental modeling and data reduction pipelines improve considerably.

In a broad class of inflationary models, the leading non-Gaussian bispectrum arises from one-loop rather than tree-level processes. However, realistic one-loop contributions remain largely unexplored for phenomenologically relevant masses beyond the simplest bubble diagrams. This is insufficient for observational purposes because, for generic masses and couplings, triangle contributions need not be suppressed relative to their bubble counterparts. We present a numerical method for evaluating scalar one-loop in-in diagrams contributing to the inflationary bispectrum at fully general external momenta and masses. First, the Witten-Feynman parameterization reduces de Sitter loop integrals to generalized Euler-Mellin integrals governed by Symanzik graph polynomials. Unfortunately, the exponents of the polynomials in the integrand become complex for sufficiently heavy masses, leading to sign problems when evaluating the integral using standard numerical techniques. To remedy this problem, we introduce the reduced Schwinger method, which evaluates a highly oscillatory subintegral analytically to obtain a Gauss hypergeometric kernel, leaving the remaining integrals to standard numerical quadrature. We validate the algorithm by reproducing known analytic results for the tree-level bispectrum in terms of ${}_3F_2$ functions, and then apply it to the one-loop bubble and triangle contributions at general kinematics. This yields the first direct numerical evaluation of the complete one-loop bispectrum, valid across the full kinematic range. Using these numerical results, we construct bispectrum templates and compare them with CMB data.

Within the Hot Big Bang picture, as usually interpreted in the standard LCDM framework and its hierarchical scenario for elliptical galaxy assembly, the cosmic microwave background (CMB) is associated with photon decoupling near z = 1100, and the Planck angular power spectra are taken to constrain primordial 10^{-5}-level fluctuations that seeded later structure formation. We show that, in addition to the LCDM model, two cosmological models based on Milgromian gravitation are also consistent with the Planck CMB power spectra, such that the spectra do not uniquely favor dark matter. We then argue that the published CMB spectra are not direct observables, but reconstructed quantities obtained after foreground subtraction and corrections for weak lensing, photon-electron scattering, and gravitational energy redshifts along the line of sight. Because these steps depend on the assumed growth history of structure, the resulting spectra depend on the cosmological model adopted in the data reduction. We also note that the reported correlation between the hemispherical CMB asymmetry and the excess on-sky distribution of elliptical galaxies may point to matter inhomogeneities spanning large portions of the observable universe. Motivated by observational tensions in the hierarchical assembly of elliptical galaxies, we review the consequences of elliptical-galaxy formation on a downsizing timescale, which implies a significant extragalactic foreground released at 15< z < 20. Under conservative assumptions, this foreground contributes at least 1.4 percent of the observed CMB energy density and has not been included in CMB analyses. It follows that the reported 10^{-5}-level fluctuations is introduced by overly aggressive foreground cleaning.

Ultralight dark matter could be an axial vector field, a simple possibility which motivates new experiments. Couplings to fermions, through an axial vector current or a dark electric dipole moment operator, lead to enhanced spin torques compared to axion dark matter. An axial vector also has an analogue of the axion-photon coupling, though its consistent realization requires a photon mass. Under this "axial-photon" coupling, the effect of a background magnetic field is suppressed, and the strongest experimental probes involve polarimetry, electric fields in superconducting cavities, and the cosmic microwave background. Since a massive axial vector is dual to a massive two-form, our results also apply to "Kalb-Ramond" dark matter motivated by string theory.

We present an emulator of the halo mass function (HMF) based on Gaussian-process regression, that exploits the evolution mapping framework. This framework splits cosmological parameters into shape parameters ($\mathbf{\Theta}_\mathrm{s}$), which set the shape of the linear power spectrum, and evolution parameters ($\mathbf{\Theta}_\mathrm{e}$), which only rescale its amplitude, with their net effect entirely captured by the clustering amplitude, $\sigma_{12}$. The emulation acts in two steps: first, an emulator predicts the overall shape of the HMF given $\mathbf{\Theta}_\mathrm{s}$ and $\sigma_{12}$; then, a second emulator applies a small correction accounting for the residual dependence on the integrated growth history of density fluctuations. The emulator is trained on a suite of 100 simulations of flat $\Lambda$CDM cosmologies but, owing to evolution mapping, can be applied to predict the abundance of haloes in cosmologies with any extended space of $\mathbf{\Theta}_\mathrm{e}$, such as curvature, quintessence and dynamical dark energy. We test the emulator against independent $\Lambda$CDM runs and on an additional validation suite of dynamical dark energy simulations, achieving per cent-level accuracy over a wide range of masses and redshifts, with the performance only slightly degrading at early times, where the training data points are fewer. Compared to other state-of-the-art HMF emulators, its accuracy is higher in nearly all tested cases. Our results demonstrate the broad applicability of the evolution mapping framework to build very accurate emulators of statistics of the density field. The emulator is publicly available as part of the Aletheia emulator suite.

The recent 248-keV nuclear recoil candidate reported by LUX-ZEPLIN has renewed interest in endothermic inelastic dark matter, motivating us to examine its capture in primordial dark stars. Relative to the conventional elastic-capture picture in dark star evolution, endothermic capture adds two qualitative features. First, it opens only after the growing star crosses a compactness threshold, expressed as a kinematic radius $R_{\rm kin}\propto\mu_{\chi}M_\star/\delta$ set by the stellar mass, the dark-matter–nucleus reduced mass and the mass splitting. The accreting growth carries the star through the threshold, and the capture rate turns on quadratically above it. Second, although newly captured particles generically begin on nonthermal bound orbits, endothermic kinematics can keep this normally transient population spatially extended, turning it into a persistent reservoir rather than an intermediate step toward a thermal core. Following complete chains of state-changing collisions, we find that the reservoir compacts sharply and then stalls, because a ground state particle below a compactness-dependent orbital energy has no allowed up-scatter anywhere in the star. A percent-level radius contraction reopens the relaxation. These kinematic results do not depend on whether the excited state decays promptly or is long-lived. As a result, inelastic capture does not replenish a thermal annihilation core. The captured population forms an evolving orbital distribution that sets up the co-evolutionary dynamics between the star and the dark matter in the core and the reservoir, which we develop in a companion paper.

We extend the Dark Matter-Baryon Separability Condition to show that the same framework developed for dark matter deficient galaxies naturally admits a conjugate branch describing preferential baryonic depletion. Using the recently discovered almost-dark galaxy TTT J1237327+143535 as a worked example, we derive a family of dynamical consistency relations parameterized by the unknown progenitor ratio $\mu_i$, including thresholds for $\sigma_{\rm los}$, $M_{\rm dyn}$, the enclosed baryonic fraction and the dynamical mass to light ratio. We further connect the separability framework to the expected globular cluster population, providing an independent consistency test of the inferred halo mass. We also provide some bounds on the baryon ratio using the tidal properties of Virgo Cluster. Future measurements of stellar kinematics, gas content and globular clusters can therefore determine whether this galaxy occupies the positive separability branch and also test whether dark matter deficient and baryon depleted systems can be described within a common framework.

Violations of Bell's inequalities offer a definitive signal of non-classical (quantum) behavior in local deterministic systems. Yet, in many physical settings where quantum mechanics is expected to play an important role, one cannot construct a Bell-type test using the available observables. Cosmology offers one concrete example, where cosmic structure may have originated from quantum vacuum fluctuations yet all observations are effectively classical. Nevertheless, recent work suggests that quantum and classical time evolution may still be differentiated by the pattern of statistical correlations of these observables. In this paper, we explore and generalize the use of correlations as Bell-type test of the nature of time evolution. We show that quantum vacuum fluctuations of closed systems undergoing Hamiltonian evolution produce unique correlations that are not mimicked by classical Hamiltonian systems. Correlations in the quantum vacuum are generally time-independent and are controlled by the energy gap between the ground and exited states. Classical systems exhibit apparent poles at physical frequencies that do not arise in the quantum vacuum. As one approaches the poles, the evolution becomes dominated by a resonant Hamiltonian giving rise to time dependent correlations that eventually decay through dephasing. Finally, we show that this behavior is distinct from other signals of quantum evolution, including applications to quantum optics, quantum walks, and quantum search.

Papers claiming that convolutional neural networks outperform the matched filter are now common in astronomy. Since that filter is the best linear unbiased estimator (BLUE) for any noise of given covariance, and the minimum-variance unbiased estimator under Gaussian noise, such a claim requires that the noise covariance varies from image to image or the noise is non-Gaussian. We introduce the advantage ceiling eta >= 1, which quantifies both cases: the Fisher information for the amplitude in units of the matched filter's, computable from noise-only simulations before any network is trained, and a bound on the variance of any estimator unbiased at each true amplitude. We compute eta for a suite of millimeter/submillimeter survey noise models and for compact and extended source templates, using a variational score-matching ladder whose rungs are estimator classes of increasing statistical order, from linear to convolutional. With an instrumental white-noise floor, Gaussian noise returns eta = 0.94-1.06 (+-0.04); covariance mixtures give exact ceilings of 10.2 (spectral tilt, extended source), 2.1 (leaked components) and 1.1-1.8 otherwise; residual artifacts give eta <= 1.09. Source confusion gives the largest advantage, eta >= 3.8 (extended) and >= 2.4 (compact). Three unmodelled channels - a zeroed DC mode, a missing white floor and floating-point rounding - can manufacture spurious advantages of up to two orders of magnitude. A ResNet regressor is 6-15% less efficient than the matched filter on Gaussian noise once prior shrinkage is divided out, and realizes a factor 1.8 of the 10.2 available on the spectral-tilt mixture; a companion paper tests such regressors against these ceilings.

This work concerns a procedure for removing gauge dependence from graviton corrections to the effective field equations for a massless, minimally coupled scalar on de Sitter background. The procedure involves combining diagrams in the same way as the scattering amplitude for the $t$-channel exchange of the massless scalar between two massive particles, but without taking the asymptotic limits which are problematic in cosmology. Implementing this at 1-loop on flat space background requires five classes of diagrams, in addition to the naive exchange, and the combination of those diagrams does eliminate dependence on the graviton gauge fixing functional. When those same diagrams are generalized to de Sitter background, their combination cancels the most important (“nonlocal”) secular gauge dependence, but it leaves (“local”) secular gauge dependence that is associated with external legs. Local secular gauge dependence can be removed by adding two additional classes of diagrams, and making secular corrections to the external wavefunctions. The purpose of this paper is to include these additional corrections on de Sitter background in order to derive fully gauge independent effective field equations at 1-loop order.

For the first time, we establish a direct connection between inflationary dynamics and the subsequent magnetohydrodynamic evolution. Starting from vacuum fluctuations, we self-consistently evolve the coupled inflaton-plasma system through inflation, reheating, and into the radiation-dominated era. We find an inflaton-driven inverse cascade followed by freely decaying turbulence, with kinetic energy dominating over magnetic energy and driving dynamo amplification. The inflaton-driven turbulence causes steeper magnetic energy decay than helical turbulence and should therefore be accounted for subsequent evolution of primordial fields and their present-day observables.