Abstract We investigate, within a generalized Vaidya anisotropic reconstruction, whether two finite-density QCD-inspired effective equations of state can generate the near-center stress-energy scaling required for a regular black-hole interior during spherical collapse. The Einstein equations for this geometry fix the radial principal pressure to P ∥ = - ρ . We therefore adopt the phenomenological anisotropic closure P ⊥ = p QCD , where P ⊥ = - M” / r is the transverse principal pressure. This identification should not be interpreted as an isotropic equilibrium description of QCD matter. The resulting identity rρ ' + 2( ρ + P ⊥ ) = 0 determines the radial temperature profile and allows the mass function to be reconstructed without assuming a regular profile a priori. For the chiral model, the conservation equation admits an exact Lambert- W solution, whose high-temperature branch gives T 2 ∝ r -296/159 and a non-integrable central density. For the finite-density mean-field QGP model, the exact implicit solution gives T 2 ∝ r -2 δ/γ and M-M 0 ∝ r 3-4 δ/γ , which is incompatible with the regularity condition M = 𝒪( r 3 ) throughout the physical parameter range of the adopted approximation. More generally, if P ⊥ / ρ → w 0 , then the generalized Vaidya identity gives M ∝ r 1-2 w 0 . Under the transverse null energy condition, a regular center requires the unique limiting behavior w 0 = -1. Neither effective QCD closure considered here approaches this vacuum-like limit. Our result is therefore a restricted no-go statement for the generalized Vaidya anisotropic reconstruction: finite quark chemical potential modifies the transition thermodynamics but does not by itself generate a self-regularizing core. We illustrate the additional short-distance physics required for regularization through a smooth compact-support matching to an inner vacuum-like component.
Abstract We demonstrate that induced gravitational waves (IGWs) can naturally emerge within well-motivated realizations of thermal leptogenesis, thereby providing a possible observational handle on this framework at remarkably high energy scales. To illustrate this principle, we put forth a simple leptogenesis model in which an early matter-dominated phase, connected to the leptogenesis scale, enhances the generation of gravitational waves induced by early structure formation. Leveraging recent N-body and lattice simulation results for IGW computations in the non-linear regime, we show that, within the assumptions of the model, the frequency and amplitude of these IGWs can be correlated with the thermal leptogenesis scale.
We present a methodological and observational study of indirect dark matter searches based on the two-body decay of dark matter particles into final states containing a photon, as predicted in many well-motivated models such as axion-like particles and sterile neutrinos. For instruments with an energy resolution of R equivalent to lambda/triangle lambda= O(103), the expected dark-matter signal from extragalactic targets generally consists of two narrow spectral lines: one from the target object and one from the Milky Way halo, separated by their relative velocities. We develop and apply a dedicated double narrow-line analysis that explicitly incorporates this two-component morphology. Using the latest XRISM observation of the Centaurus cluster as a case study, we perform a full spectral fit and derive new constraints on the dark-matter decay rate. The analysis demonstrates that the double-line framework provides a robust statistical discriminator against spurious single-line or background features, and can yield competitive limits in cluster observations. Our results establish this approach as a reliable and systematic technique for future high-resolution detector for the search of dark matter.
Abstract The sound horizon scale r s is a key source of information for measurements of H 0 from early-time data, and is therefore a common target of new physics proposed to solve the Hubble tension. We present a sub-2% measurement of the Hubble constant that is independent of this scale, using data from the first data release of the Dark Energy Spectroscopic Instrument (DESI DR1). Building on previous work, we remove dependency on the sound horizon size using a heuristic rescaling procedure at the power spectrum level. A key innovation is the inclusion of uncalibrated (agnostic to r s ) post-reconstruction BAO measurements from DESI DR1, as well as using the CMB acoustic scale θ * as a high-redshift anchor. Uncalibrated type-Ia supernovae are often included as an independent source of Ω m information; here we demonstrate the robustness of our results by additionally considering two supernova-independent alternative datasets. We find somewhat higher values of H 0 relative to our previous work: 69.2 +1.3 -1.4 , 70.3 +1.4 -1.2 , and 69.6 +1.3 -1.8 km s -1 Mpc -1 respectively when including measurements from i) Planck /ACT CMB lensing × unWISE galaxies, ii) the DES Year 3 6×2pt analysis, and iii) Planck /ACT CMB lensing + the DES Year 5 supernova analysis. These remarkably consistent constraints achieve better than 2% precision; they are among the most stringent sound horizon-independent measurements from LSS to date, and provide a powerful avenue for probing the origin of the Hubble tension.
Abstract The Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI) is the largest sample to date for small-scale Ly α forest cosmology, accessed through its one-dimensional power spectrum ( P 1D ). The Ly α forest P 1D is extracted from quasar spectra that are highly inhomogeneous (both in wavelength and between quasars) in noise properties due to intrinsic properties of the quasar, atmospheric and astrophysical contamination, and also sensitive to low-level details of the spectral extraction pipeline. We employ two estimators in DR1 analysis to measure P 1D : the optimal estimator and the fast Fourier transform (FFT) estimator. To ensure robustness of our DR1 measurements, we validate these two power spectrum and covariance matrix estimation methodologies against the challenging aspects of the data. First, using a set of 20 synthetic 1D realizations of DR1, we derive the masking bias corrections needed for the FFT estimator and the continuum fitting bias needed for both estimators. We demonstrate that both estimators, including their covariances, are unbiased with these corrections using the Kolmogorov-Smirnov test. Second, we substantially extend our previous suite of CCD image simulations to include 675,000 quasars, allowing us to accurately quantify the pipeline's performance. This set of simulations reveals biases at the highest k values, corresponding to a resolution error of a few percent. We base the resolution systematics error budget of DR1 P 1D on these values, but do not derive corrections from them since the simulation fidelity is insufficient for precise corrections.
In this paper, we study cosmological perturbations in a modified theory of loop quantum cosmologies, the so-called mLQC-I model. Our purposes are two-fold: First, using a method developed by Birrell and Davies, we identify an initial state in the remote contracting phase, which turns out to be stable, minimize particle creations and diagonalize the Hamiltonian, despite the fact that at this time some modes may be still outside of the Hubble horizon and not in their adiabatic states. Second, using the uniform asymptotic approximation method, we obtain the first-order approximate solutions of the mode function in terms of either the Airy functions, or the first or second kind of cylindrical functions, depending on the values of the wavenumber. In each case, the mode function contains two integration constants, which are uniquely determined by the initial state.
Abstract Recent late-Universe observations suggest an open Universe. If confirmed, such a departure from spatial flatness would carry profound implications for our understanding of cosmic inflation and the ultimate fate of the Universe. Motivated by this intriguing result and the release of new data, we revisit the question using baryon acoustic oscillation measurements from DESI DR2, multiple Type Ia supernova samples, refined strong gravitational lensing time-delay analyses, and the most up-to-date cosmic chronometer data. We find that within the Λ cold dark matter (ΛCDM) paradigm, the combined data still prefer an open Universe with Ω K = 0.049±0.037. However, this preference vanishes in extensions to ΛCDM, where the data instead favor a flat Universe. The model comparison shows that for ΛCDM, introducing new physics is preferred over merely allowing spatial curvature, and flat ΛCDM extensions perform better than their curved counterparts. We therefore argue that the mild open-Universe signal may be an artifact of limited model flexibility, rather than a genuine feature of late-Universe observations.
The one-dimensional flux power spectrum (P 1 D ) of the Lyman- α forest probes small-scale structure in the intergalactic medium (IGM) and is therefore sensitive to a variety of cosmological and astrophysical parameters. These include the amplitude and shape of the matter power spectrum, the thermal history of the IGM, the sum of neutrino masses, and potential small-scale fluctuations due to the nature of dark matter. However, P 1 D is also highly sensitive to observational and instrumental systematics, making accurate synthetic spectra essential for validating analyses and quantifying these effects, especially in high-volume surveys like the Dark Energy Spectroscopic Instrument (DESI). We present an efficient lognormal mock framework for generating one-dimensional Lyman- α forest spectra tailored for P 1 D analysis. Our method captures the redshift evolution of the mean transmitted flux and the scale-dependent shape and amplitude of the one-dimensional flux power spectrum by tuning Gaussian field correlations and transformation parameters. Across the DESI Early Data Release (EDR) redshift range (2.0 ≤ z ≤ 3.8), and a wide range of scales (10 -4 s km -1 ≤ k ≤ 1.0 s km -1 ), our mocks recover the mean flux evolution with redshift to sub-percent accuracy, and the P 1 D at the percent level. Additionally, we discuss potential extensions of this framework, such as the incorporation of astrophysical contaminants, continuum uncertainties, and instrumental effects. Such improvements would expand its utility in ongoing and upcoming surveys and enable a broader range of validation efforts and systematics studies for P 1 D inference and precision cosmology.
The origin of a number of proton-rich isotopes in the solar system has been a long-standing puzzle. A promising explanation is the νp -process, which is posited to operate in the neutrino-driven outflows that form inside core-collapse supernovae after shock revival. While recent studies have analyzed several relevant physical effects that influence the efficiency of this process, the impact of General Relativity (GR) on it remains unexplored. We perform a comparative analysis of the time-integrated νp -process yields in Newtonian and fully GR calculations, using detailed models of time-evolving outflow profiles. The GR effects are seen to suppress the production of seed nuclei, significantly boosting the resulting p-nuclide abundances. Our reference GR model, with an 18 M ⊙ progenitor, reproduces both the relative and absolute solar system abundances of the entire set of the p nuclides in the mass range 74 ≤ A ≤ 102. The yields are suboptimal in our 12.75 M ⊙ GR model, where the outflow transitions to the supersonic regime several seconds into the explosion, suppressing further p -nuclide production. In both models, most of the production of the crucial 92,94 Mo and 96,98 Ru p isotopes occurs relatively early, 1–3 seconds after shock revival. In contrast, a large fraction of the shielded isotope 92 Nb is produced in the subsequent ejecta. The impact of GR on this isotope is especially large, with its final abundance boosted by a factor of 25 compared to a Newtonian calculation. In summary, with the GR effects taken into account, the νp -process in a sufficiently massive progenitor can provide a unifying explanation for the origin of all p nuclei in the solar system up to 102 Pd.
The upcoming stage IV wide-field surveys will provide high precision measurements of the large-scale structure (LSS) of the universe. Their interpretation requires fast and accurate theoretical predictions including large scales. For this purpose, we introduce SwiftC ℓ , a fast, accurate and differentiable JAX -based pipeline for the computation of the angular power spectrum beyond the Limber approximation. It uses a new FFTLog-based method which can reach arbitrary precision and includes interpolation along k , allowing for k -dependent growth factor and biases. SwiftC ℓ includes a wide range of probes and effects such as galaxy clustering, including magnification bias, redshift-space distortions and primordial non-Gaussianity, weak lensing, including intrinsic alignment, cosmic microwave background (CMB) lensing and CMB integrated Sachs-Wolfe effect. We compare our pipeline to the other available beyond-Limber codes within the N5K challenge from the Rubin Observatory Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration. SwiftC ℓ computes the 120 different angular power spectra over 103 ℓ-multipoles in 5 ms on one GPU core while the computation of the gradient is approximately 4× slower. Using a pre-calculation, SwiftC ℓ is thus about 40× faster than the winner of the N5K challenge with comparable accuracy. Furthermore, all outputs are auto-differentiable, facilitating gradient-based sampling and robust and accurate Fisher forecasts. We showcase a Markov Chain Monte Carlo, a Hamiltonian Monte Carlo and a Fisher forecast on an LSST-like survey, illustrating SwiftC ℓ 's differentiability, speed and reliability in measuring cosmological parameters. The code is publicly available at https://cosmo-gitlab.phys.ethz.ch/cosmo_public/swiftcl .
There exist several different proposals for a measure in Quantum Gravity theories. Although sometimes being labelled as non covariant, the measure derived in [7] for GR has the particularity that, in the extremal, the volume divergences proportional to delta 4(0) cancel out. The analogous for Quadratic Gravity [1]-[2] was considered in [48]-[49]. However, as far as the author's knows, the issue of volume divergences was not considered for this last measure. The present work fills this gap and presents an analysis showing that, in the extremal, these divergences cancel as well. This is up to some subtleties related to superdeterminants. The possibility of employing non invariant measures may be accepted if the anomaly in the measure is compensated by counter term redefinitions of the model under analysis. This makes difficult to disprove, at the present times, some choices of measures. Quadratic Gravity [1]-[2], is known to be renormalizable in flat space, and there are a finite number of counter terms needed in order to renormalize its effective action. However, around a curved space this is not known, and this complicates considerably the analysis. These issues are reviewed in the text, together with an analysis of covariant measures. In particular, it is shown how these measures [51, 52]-[54] can be found if one condition in [7] is relaxed.
Recent observations of large-scale statistical isotropy violations have prompted the adoption of anisotropic cosmological models that account for inherent directional curvature. Studies of these anisotropic spacetimes have shown how they can explain the evolutionary dynamics and light propagation in the universe. Here, we consider one such interesting set of spacetimes that preserve homogeneity but place no constraint on isotropy during the inflationary epoch, to examine whether we can address the possibility of anisotropic inflation in the universe. Researchers have proposed inflationary models in which a vector field coupled to the inflaton is found to violate the cosmic no-hair theorem for the anisotropic Bianchi type I spacetime, due to the existence of a stable anisotropically inflationary fixed point. Lately, this study has been extended to axisymmetric spacetimes of Bianchi type II, III, and the Kantowski-Sachs metric, and it has been inferred that the entire family of spacetimes is attracted to the anisotropic Bianchi I fixed point. By constructing inflationary models where the spatial slices are anisotropic Thurston 3-geometries, we demonstrate that the intrinsic eccentricity of the background geometry induces an isotropy-violating vector field. This field, through its coupling to the inflaton, triggers a secondary phase of anisotropic inflation. We perform dynamical stability and phase-space analyses to assess the feasibility of anisotropic inflation. The results for the considered set of Thurston geometries showed the presence of a unique, stable inflationary fixed point that converges, similar to those in Bianchi spacetimes, thereby indicating the cosmological viability of inflation with anisotropic hair.
We investigate the imaging and polarization properties of Kerr-MOG black holes surrounded by geometrically thick accretion flows. The MOG parameter alpha introduces deviations from the Kerr metric, providing a means to test modified gravity in the strong field regime. Two representative accretion models are considered: the phenomenological radiatively inefficient accretion flow (RIAF) and the analytical ballistic approximation accretion flow (BAAF). Using general relativistic radiative transfer, we compute synchrotron emission and polarization maps under different spins, MOG parameters, inclinations, and observing frequencies. In both models, the photon ring and central dark region expand with increasing alpha, whereas frame dragging produces pronounced brightness asymmetry. The BAAF model predicts a narrower bright ring and distinct polarization morphology near the event horizon. By introducing the net polarization angle chi net and the second Fourier mode angle beta 2, we quantify inclination-and frame-dragging-induced polarization features. Our results reveal that both alpha and spin significantly influence the near-horizon polarization patterns, suggesting that high-resolution polarimetric imaging could serve as a promising probe of modified gravity in the strong field regime.
The observations of the redshifted 21-cm signal from neutral hydrogen are a promising probe for understanding the Cosmic Dawn and the Epoch of Reionisation (EoR). One of the primary obstacles to the statistical detection of the Cosmological signal is the presence of residual foreground arising from gain calibration errors. Previous studies have shown that gain calibration errors as small as 0.01% can lead to a biased interpretation of the observed signal power spectrum estimation, by nearly an order of magnitude. A recent study further highlights that to accurately retrieve astrophysical parameters, the threshold gain calibration error should be below 0.01%. This work investigates the impact of residual extragalactic foregrounds arising from gain calibration errors on the efficacy of foreground mitigation strategies. We use an end-to-end pipeline 21CME2E to simulate a realistic sky model and telescope configuration within the 138-146 MHz frequency range and perform a detailed power spectrum analysis across several threshold levels of the gain calibration error. We introduce a hybrid mitigation technique that combines the foreground removal techniques, Gaussian process regression and principal component analysis, with foreground avoidance. Our results indicate that recovery of the HI signal within 2 sigma is possible for calibration gain error of <= 1% with minimal loss of power spectrum sensitivity over the scale range 0.05 <= k <= 0.5 Mpc(-1). We find that gain calibration errors beyond this threshold lead to signal suppression on large scales due to the loss of spectral smoothness of the residual foreground. In effect, this work offers a comparative assessment of three foreground mitigation strategies, removal, avoidance, and a hybrid approach, in the context of future SKA1-Low AA* observations.
We present SBi3PCF, a simulation-based inference (SBI) framework for analysing a higher-order weak lensing statistic, the integrated 3-point correlation function (i3PCF). Our approach forward-models the cosmic shear field using the CosmoGridV1 suite of Nbody simulations, including a comprehensive set of systematic effects such as intrinsic alignment, baryonic feedback, photometric redshift uncertainty, shear calibration bias, and shape noise. Using this, we have produced a set of DES Y3-like synthetic measurements for 2-point shear correlation functions xi +/- (2PCFs) and i3PCFs zeta +/- across 6 cosmological and 11 systematic parameters. Having validated these measurements against theoretical predictions and thoroughly examined for potential systematic biases, we have found that the impact of source galaxy clustering and reduced shear on the i3PCF is negligible for Stage-III surveys. Furthermore, we have tested the Gaussianity assumption for the likelihood of our data vector and found that while the sampling distribution of the 2PCF can be well approximated by a Gaussian function, the likelihood of the combined 2PCF + i3PCF data vector including filter sizes of 90 ' and larger can deviate from this assumption. Our SBI pipeline employs masked autoregressive flows to perform neural likelihood estimation and is validated to give statistically accurate posterior estimates. On mock data, we find that including the i3PCF yields a substantial 63.8% median improvement in the figure of merit for ohm m-sigma 8-w0. These findings are consistent with previous works on the i3PCF and demonstrate that our SBI framework can achieve the accuracy and realism needed to analyse the i3PCF in wide-area weak lensing surveys.
The cosmic dipole tension - the discrepancy between the Cosmic Microwave Background kinematic dipole and the matter dipole inferred from all-sky surveys poses a significant challenge to the Cosmological Principle, which dictates that the universe is homogeneous and isotropic at the largest scales. Traditional measurement of the matter dipole requires selecting an appropriate limiting flux and calculating the dipolar modulation using sources brighter than the flux. This approach, however, ignores the shape of the source luminosity function (LF) and deprives the analysis of this crucial information. In this study, we present a new approach to calculate the matter dipole by integrating the source flux distribution into the analysis. We achieve this by dividing the catalogue into disjoint flux bins and simultaneously fitting the matter dipole across them. For non-power-law LFs, this method gives a higher Bayes factor - and hence a better description of the matter dipole - as compared to the traditional approach. The method works best when the flux cuts are selected in regions where the LF's shape changes significantly. We discuss the feasibility of this method for upcoming cosmological surveys and show that it has the potential to yield decisive results at both radio and infrared wavelengths.
The origin of primordial magnetic fields and the nature of dark matter remain open problems in cosmology, largely due to the absence of direct observational probes of early-Universe magnetogenesis. Primordial black holes (PBHs) provide a potential link between these two issues, as their formation is sensitive to small-scale energy-density fluctuations. In this work, we investigate PBH formation sourced by primordial magnetic fields generated in the early Universe. We consider a magnetogenesis scenario that can account for the observed large-scale magnetic fields while also allowing PBH formation in a mass range consistent with PBHs constituting a significant fraction of the cold dark matter. We further analyze the stochastic gravitational-wave background produced by magnetic-field-induced anisotropic stresses and show that, for certain regions of parameter space, the resulting signal lies within the projected sensitivity of future gravitational-wave observatories such as LISA, DECIGO, BBO, and SKA. By comparing the parameter dependence of the PBH abundance and the gravitational-wave spectrum, we demonstrate that these observables provide complementary constraints on the underlying magnetogenesis model. Our results illustrate how combining PBH and gravitational-wave observations can improve our ability to test magnetogenesis scenarios and probe early-Universe dynamics.
