Search

I review and discuss the possible implications for inflation resulting from considering new physics in light of the Hubble tension. My study is motivated by a simple argument that the constraints on inflationary parameters, most typically the spectral index $n_s$, depend to some extent on the cosmological framework. To avoid broadening the uncertainties resulting from marginalizing over additional parameters (typical in many alternative models), I first adopt the same alternative viewpoint of previous studies and analyze what happens if a physical theory can fix extra parameters to non-standard values. Focusing on the dark energy equation of state $w$ and the effective number of relativistic species $N_{\rm{eff}}$, I confirm that physical theories able to fix $w \approx -1.2$ or $N_{\rm{eff}} \approx 3.9$ produce values of $H_0$ from CMB and BAO in line with the local distance ladder estimate. While in the former case I do not find any relevant implications for inflation, in the latter scenarios, I observe a shift towards $n_s \approx 1$. From a model-selection perspective, both cases are strongly disfavored compared to $\Lambda$CDM. However, models with $N_{\rm{eff}} \approx 3.3 - 3.4$ could bring the $H_0$ tension down to $\sim 3\sigma$ while being moderately disfavored. Yet, this is enough to change the constraints on inflation so that the most accredited models (e.g., Starobinsky inflation) would no longer be favored by data. I then focus on Early Dark Energy (EDE), arguing that an EDE fraction $f_{\rm{EDE}}\sim 0.04 - 0.06$ (only able to mildly reduce the $H_0$-tension down to $\sim 3\sigma$) could already require a similar change in perspective on inflation. In fact, performing a full joint analysis of EDE and Starobinsky inflation, I find that the two models can hardly coexist for $f_{\rm{EDE}}\gtrsim 0.06$., Comment: 25 pages, 10 figures

The eROSITA will deliver an unprecedented volume of X-ray survey observations, 20-30 times more sensitive than ROSAT in the soft band (0.5-2 keV) and for the first time imaging in the hard band (2-10 keV) including galaxy clusters and groups along with obscured and unobscured AGNs. This calls for a powerful theoretical effort to control the systematics and biases that may affect the data analysis. We investigate the detection technique and selection effects in the galaxy group and AGN populations of a mock eROSITA survey at the depth of eRASS:4. We create a $30\times 30$ deg$^{2}$ mock observation based on the cosmological hydrodynamical simulation Magneticum Pathfinder within z=0-0.2. We combine a physical background extracted from the real eFEDS background analysis with realistic simulations of X-ray emission for the hot gas, AGNs and X-ray binaries. We apply a detection procedure equivalent to the reduction done on eRASS data and evaluate the completeness and contamination to reconstruct the luminosity functions of the extended and point sources in the catalogue. We assess the completeness of extended detections as a function of the input X-ray flux and halo. We achieve full recovery of the brightest (most massive) clusters and AGNs. However, a significant fraction of galaxy groups remains undetected. Examining the gas properties between the detected and undetected galaxy groups at fixed halo mass, we observe that the detected population exhibits, on average, higher X-ray brightness compared to the undetected ones. Moreover, we find that X-ray luminosity primarily correlates with the hot gas fraction, rather than temperature or metallicity. Our simulation suggests the presence of a systematic selection effect in current surveys, resulting in X-ray survey catalogues predominantly composed of the lowest-entropy, gas-richest, and highest surface brightness halos on galaxy group scales., Comment: 18 pages, 14 figures, submitted to A&A

Distinguishing a core and a cusp within dark matter halos is complexified by the existence of mass-anisotropy degeneracy, where various combinations of velocity anisotropy ($\beta$) and inner density slope ($\gamma$) yield similar observational signatures. We construct a dynamical model that incorporates the 4th-order velocity moments to alleviate this challenge. The inclusion of the 4th-order velocity moments enables stars' line-of-sight velocity distribution (LOSVD) to be flexible. This flexible LOSVD can cover from a thin-tailed to a heavy-tailed distribution that is inaccessible if only the 2nd-order moments are considered. We test our dynamical model using mock galaxies and find that a ratio of the global line-of-sight velocity dispersion of the mock galaxy to the velocity error measurement $\sigma_{\mathrm{los,global}} / \Delta v_{\mathrm{los}} \gtrsim 4$ is required to avoid obtaining systematically biased results. This bias arises from the strong dependency of the 4th-order moments on the LOSVD tails, and not even increasing the sample size to $10^4$ stars can mitigate this effect. In that velocity ratio, $\beta$ is recovered within $\sim 1 \sigma$ even when the sample size is only 500 stars, regardless of the recovery of the other parameters. However, the estimation of $\gamma$ varies, depending on the degree to which LOSVDs deviate from Gaussianity. Because of the more significant change in its LOSVDs, a cored dark halo is more likely to be identified than a cusp., Comment: 19 pages, 14 figures, submitted to ApJ

The violation of the null energy condition (NEC) may play a crucial role in enabling a scalar field to climb over high potential barriers, potentially significant in the very early universe. We propose a single-field model where the universe sequentially undergoes a first stage of slow-roll inflation, NEC violation, and a second stage of slow-roll inflation. Through the NEC violation, the scalar field climbs over high potential barriers, leaving unique characteristics on the primordial gravitational wave power spectrum, including a blue-tilted nature in the middle-frequency range and diminishing oscillation amplitudes at higher frequencies. Additionally, the power spectrum exhibits nearly scale-invariant behavior on both large and small scales., Comment: 25 pages, 18 figures

We analyze the model put forth by Ref. \cite{Oppenheim:2024rcp}, in which it is claimed that "post-quantum classical gravity" (PQCG), a stochastic theory of gravity, leads to modified Newtonian dynamics (MOND) behavior on galactic scales that reproduces galactic rotation curves. We show that this analysis has two basic problems: (i) the equations of PQCG do not lead to a new large scale force of the form claimed in the paper, and (ii) the form claimed is not of the MONDian form anyhow and so does not correspond to observed galactic dynamics. We also mention other potential problems that might arise from stochastic gravitational behavior., Comment: 3 pages in double column format

Embedded walls are domain wall solutions which are unstable in the vacuum but stabilized in a plasma of the early Universe. We show how embedded walls in which the electroweak symmetry is restored can lead to an efficient scenario of electroweak baryogenesis. We construct an extension of the Standard Model of particle physics in which embedded walls exist and are stabilized in an electromagnetic plasma., Comment: 13 pages

We study the Barrow cosmological model, which proposes that quantum gravity effects create a complex, fractal structure for the universe's apparent horizon. We leverage the thermodynamics - gravity conjecture. By applying the Clausius relation to the apparent horizon of the Friedmann - Lema\^itre - Robertson - Walker universe within this framework, we derive modified field equations where the Barrow entropy is linked to the horizon. We assess the Barrow cosmology against current observations - cosmic microwave background , supernovae , and baryon acoustic oscillations data - and include projections for future Laser Interferometer Space Antenna (LISA) standard sirens (SS). Our numerical results suggest a modest improvement in the Hubble tension for Barrow cosmology with phantom dark energy behavior, compared to the standard cosmological model. Furthermore, incorporating simulated LISA SS data alongside existing observational constraints tightens the limitations on cosmological parameters, particularly the deformation exponent., Comment: 22 pages, 5 figures

Supposing the Laser Interferometer Space Antenna (LISA) gravitational wave (GW) detector, we exhibit the detectability of a hypothetical smooth crossover in the early universe beyond the Standard Model of particle physics through the scalar-induced gravitational wave (SIGW) in terms of the Fisher forecast. A crossover at $\sim100\,\mathrm{TeV}$ can leave a signal on the GW spectrum in the $\sim\mathrm{mHz}$ frequency range, the sweet spot of the LISA sensitivity. These possibilities are also interesting in the primordial black hole (PBH) context as the associated PBH mass $\sim10^{22}\,\mathrm{g}$ lies at the window to explain the whole dark matter. We found that the properties of the crossover can be well determined if the power spectrum of primordial scalar perturbations are as large as $\sim5\times10^{-4}$ on the corresponding scale $\sim10^{12}\,\mathrm{Mpc^{-1}}$., Comment: 8 pages, 6 figures

The attenuation of Ly$\alpha$ photons by neutral hydrogen in the intergalactic medium (IGM) at $z\gtrsim5$ continues to be a powerful probe for studying the epoch of reionisation. Given a framework to estimate the intrinsic (true) Ly$\alpha$ emission of high-$z$ sources, one can infer the ionisation state of the IGM during reionisation. In this work, we use the enlarged XQR-30 sample of 42 high-resolution and high-SNR QSO spectra between $5.8\lesssim\,z\lesssim\,6.6$ obtained with VLT/X-Shooter to place constraints on the IGM neutral fraction. This is achieved using our existing Bayesian QSO reconstruction framework which accounts for uncertainties such as the: (i) posterior distribution of predicted intrinsic Ly$\alpha$ emission profiles (obtained via covariance matrix reconstruction of the Ly$\alpha$ and N V emission lines from unattenuated high-ionisation emission line profiles; C IV, Si IV + O IV] and C III]) and (ii) distribution of ionised regions within the IGM using synthetic damping wing profiles drawn from a $1.6^3$ Gpc$^3$ reionisation simulation. Following careful quality control, we used 23 of the 42 available QSOs to obtain constraints/limits on the IGM neutral fraction during the tail-end of reionisation. Our median and 68th percentile constraints on the IGM neutral fraction are: $0.20\substack{+0.14\\-0.12}$ and $0.29\substack{+0.14\\-0.13}$ at $z = 6.15$~and 6.35. Further, we also report 68th percentile upper-limits of $\bar{x}_{\mathrm{H\,{\scriptscriptstyle I}}} < 0.21$, 0.20, 0.21 and 0.18 at $z = 5.8, 5.95, 6.05$~and 6.55. These results imply reionisation is still ongoing at $5.8\lesssim\,z\lesssim\,6.55$, consistent with previous results from XQR-30 (dark fraction and Ly$\alpha$ forest) along with other observational probes considered in the literature., Comment: 21 pages, 9 figures and 2 tables. Accepted for publication in MNRAS

Axions and axion-like particles are strongly motivated dark matter candidates that are the subject of many current ground based dark matter searches. We present first results from the Axion Dark-Matter Birefringent Cavity (ADBC) experiment, which is an optical bow-tie cavity probing the axion-induced birefringence of electromagnetic waves. Our experiment is the first optical axion detector that is tunable and quantum noise limited, making it sensitive to a wide range of axion masses. We have iteratively probed the axion mass range 40.9-43.3$\text{ neV/c}^2$, 49.3-50.6$\text{ neV/c}^2$, and 54.4-56.7$\text{ neV/c}^2$, and found no dark matter signal. On average, we constrain the ALP-photon coupling at the level $g_{a\gamma\gamma} \leq 1.9\times 10^{-8} \text{ GeV}^{-1}$. We also present prospects for future axion dark matter detection experiments using optical cavities., Comment: 9 pages, 8 figures

In this work, we study the luminosity that results from the conversion of QCD axion particles into photons in the magnetic field of the plasma accreting onto black holes (BHs). For the luminosities to be large two conditions need to be met: i) there are large numbers of axions in the PBH surroundings as a result of the so-called superradiant instability; ii) there exists a point inside the accreting region where the plasma and axion masses are similar and there is resonant axion-photon conversion. For BHs accreting from the interstellar medium in our galaxy, the above conditions require the black hole to have subsolar masses and we are therefore led to consider a population of primordial black holes (PBHs). In the conservative window, where we stay within the non-relativistic behavior of the plasma and neglect the possibility of non-linear enhancement via magnetic stimulation, the typical frequencies of the emitted photons lie on the low-radio band. We thus study the prospects for detection using the LOFAR telescope, assuming the PBH abundance to be close to the maximal allowed by observations. We find that for PBH and QCD axion with masses in the range $10^{-5}-10^{-4}\, M_\odot$ and $4 \times 10^{-8}$ and $4 \times 10^{-7}$ eV, respectively, the flux density emitted by the closest PBH, assuming it accretes from the warm ionized medium, can be detected at the LOFAR telescope. Coincidently, the PBH mass range coincides with the range that would explain the microlensing events found in OGLE. This might further motivate a dedicated search of these signals in the LOFAR data and other radio telescopes., Comment: 16 pages, 3 figures

The comparison of the properties of galaxy cluster samples selected using observations in different wavebands may shed light on potential biases of the way in which the samples are assembled. For this comparison, we introduce a new observable that does not require previous knowledge of the cluster mass: the X-ray mean surface brightness within the central 300 kpc. We found that clusters with low surface brightness, defined as those with a mean surface brightness below 43.35 \subr , are about one quarter of the whole cluster population in a sample of 32 clusters in the nearby Universe, selected independently of the intracluster medium properties. Almost no example of a low central surface brightness cluster exists instead in two X-ray selected samples, one sample based on XMM-Newton XXL-100 survey data and the other on full-depth eROSITA eFEDS data, although these clusters are known to exist in the range of redshift and mass as probed by these two surveys. Furthermore, the Sunayev-Zeldovich Atacama Cosmology Telescope cluster survey is even more selective than the previous two samples because it does not even include clusters with intermediate surface brightness, which are instead present in X-ray selected samples that explore the same volume of the Universe. Finally, a measure of the mean surface brightness, which is obtained without knowledge of the mass, proves to be effective in narrowing the number of clusters to be followed-up because it recognizes those with a low gas fraction or with a low X-ray luminosity for their mass. Identifying these would otherwise require knowledge of the mass for all clusters., Comment: A&A, in press

The phenomena of dark matter and the baryon asymmetry pose two of the most pressing questions in today's fundamental physics. Conversion-driven freeze-out has emerged as a successful mechanism to generate the observed dark matter relic density. It supports thermalization of dark matter despite its very weak couplings aligning with the null results from direct and indirect detection experiments. In this letter, we demonstrate that the departure from equilibrium of dark matter, induced by semi-efficient conversions, satisfies Sakharov's conditions, providing a novel explanation for both dark matter and the baryon asymmetry. Specifically, for a leptophilic model, we establish the mechanism of conversion-driven leptogenesis. The scenario predicts dark matter masses close to the electroweak scale offering testable predictions, such as soft displaced leptons at the LHC and future colliders., Comment: 5 pages + references, 4 figures

In the context of $f(R,T)$ gravity and other modified theories of gravity, the knowledge of the first order variation of the trace $T$ of the energy-momentum tensor with respect to the metric is essential for an accurate characterization of the gravitational field. In this paper, by considering a paradigmatic example of a perfect fluid whose dynamics is described by a pure k-essence matter Lagrangian in $f(R,T)=R+\mathcal F(T)$ gravity, we show that the first order variation of the trace of the energy-momentum tensor cannot in general be determined from the proper density, proper pressure and 4-velocity of the fluid alone, and that the sound speed of the fluid can directly influence the dynamics of gravity. We also confirm that the second variation of the matter Lagrangian with respect to the metric should not in general be neglected. These results can be particularly relevant for cosmological studies of $f(R,T)$ gravity in which some of the material content of the Universe is modeled as a perfect fluid., Comment: 4 pages

Measurements of the luminosity distance of propagating gravitational waves can provide invaluable information on the geometry and content of our Universe. Due to the clustering of cosmic structures, in realistic situations we need to average the luminosity distance of events coming from patches inside a volume. In this work we evaluate, in a gauge-invariant and fully-relativistic treatment, the impact of cosmological perturbations on such averaging process. We find that clustering, lensing and peculiar velocity effects impact estimates for future detectors such as Einstein Telescope, Cosmic Explorer, the Big Bang Observer and DECIGO. The signal-to-noise ratio of the angular power spectrum of the average luminosity distance over all the redshift bins is 17 in the case of binary black holes detected by Einstein Telescope and Cosmic Explorer. We also provide fitting formulas for the corrections to the average luminosity distance due to general relativistic effects., Comment: 23 pages, 7 figures (+ appendices)

Year 1 results of the Legacy Survey of Space and Time (LSST) will provide tighter constraints on small-scale cosmology, beyond the validity of linear perturbation theory. This heightens the demand for a computationally affordable prescription that can accurately capture nonlinearities in beyond-$\Lambda$CDM models. The COmoving Lagrangian Acceleration (COLA) method, a cost-effective \textit{N}-body technique, has been proposed as a viable alternative to high-resolution \textit{N}-body simulations for training emulators of the nonlinear matter power spectrum. In this study, we evaluate this approach by employing COLA emulators to conduct a cosmic shear analysis with LSST-Y1 simulated data across three different nonlinear scale cuts. We use the $w$CDM model, for which the \textsc{EuclidEmulator2} (\textsc{ee2}) exists as a benchmark, having been trained with high-resolution \textit{N}-body simulations. We primarily utilize COLA simulations with mass resolution $M_{\rm part}\approx 8 \times 10^{10} ~h^{-1} M_{\odot}$ and force resolution $\ell_{\rm force}=0.5 ~h^{-1}$Mpc, though we also test refined settings with $M_{\rm part}\approx 1 \times 10^{10} ~h^{-1}M_{\odot}$ and force resolution $\ell_{\rm force}=0.17 ~h^{-1}$Mpc. We find the performance of the COLA emulators is sensitive to the placement of high-resolution \textit{N}-body reference samples inside the prior, which only ensure agreement in their local vicinity. However, the COLA emulators pass stringent criteria in goodness-of-fit and parameter bias throughout the prior, when $\Lambda$CDM predictions of \textsc{ee2} are computed alongside every COLA emulator prediction, suggesting a promising approach for extended models., Comment: 18 pages, 14 figures, 8 tables

We propose a novel method (floZ), based on normalizing flows, for estimating the Bayesian evidence (and its numerical uncertainty) from a set of samples drawn from the unnormalized posterior distribution. We validate it on distributions whose evidence is known analytically, up to 15 parameter space dimensions, and compare with two state-of-the-art techniques for estimating the evidence: nested sampling (which computes the evidence as its main target) and a k-nearest-neighbors technique that produces evidence estimates from posterior samples. Provided representative samples from the target posterior are available, our method is more robust to posterior distributions with sharp features, especially in higher dimensions. It has wide applicability, e.g., to estimate the evidence from variational inference, Markov-chain Monte Carlo samples, or any other method that delivers samples from the unnormalized posterior density., Comment: 10 pages, 4 figures, 1 table

Future data provided by the \Euclid mission will allow us to better understand the cosmic history of the Universe. A metric of its performance is the figure-of-merit (FoM) of dark energy, usually estimated with Fisher forecasts. The expected FoM has previously been estimated taking into account the two main probes of \Euclid, namely the three-dimensional clustering of the spectroscopic galaxy sample, and the so-called 3$\times$2\,pt signal from the photometric sample (i.e., the weak lensing signal, the galaxy clustering, and their cross-correlation). So far, these two probes have been treated as independent. In this paper, we introduce a new observable given by the ratio of the (angular) two-point correlation function of galaxies from the two surveys. For identical (normalised) selection functions, this observable is unaffected by sampling noise, and its variance is solely controlled by Poisson noise. We present forecasts for \Euclid where this multi-tracer method is applied and is particularly relevant because the two surveys will cover the same area of the sky. This method allows for the exploitation of the combination of the spectroscopic and photometric samples. When the correlation between this new observable and the other probes is not taken into account, a significant gain is obtained in the FoM, as well as in the constraints on other cosmological parameters. The benefit is more pronounced for a commonly investigated modified gravity model, namely the $\gamma$ parametrisation of the growth factor. However, the correlation between the different probes is found to be significant and hence the actual gain is uncertain. We present various strategies for circumventing this issue and still extract useful information from the new observable., Comment: 16 pages, 7 figures, submitted to A&A

We employ Hubble data and Gaussian Processes in order to reconstruct the dynamical connection function in $f(Q)$ cosmology beyond the coincident gauge. In particular, there exist three branches of connections that satisfy the torsionless and curvatureless conditions, parameterized by a new dynamical function $\gamma$. We express the redshift dependence of $\gamma$ in terms of the $H(z)$ function and the $f(Q)$ form and parameters, and then we reconstruct it using 55 $H(z)$ observation data. Firstly, we investigate the case where ordinary conservation law holds, and we reconstruct the $f(Q)$ function, which is very well described by a quadratic correction on top of Symmetric Teleparallel Equivalent of General Relativity. Proceeding to the general case, we consider two of the most studied $f(Q)$ models of the literature, namely the square-root and the exponential one. In both cases we reconstruct $\gamma(z)$, and we show that according to AIC and BIC information criteria its inclusion is favoured compared to both $\Lambda$CDM paradigm, as well as to the same $f(Q)$ models under the coincident gauge. This feature acts as an indication that $f(Q)$ cosmology should be studied beyond the coincident gauge., Comment: 19 pages, 5 figures

Forty years ago, Witten suggested that dark matter could be composed of macroscopic clusters of strange quark matter. This idea was very popular for several years, but it dropped out of fashion once lattice QCD calculations indicated that the confinement/deconfinement transition, at small baryonic chemical potential, is not first order, which seemed to be a crucial requirement in order to produce large clusters of quarks. Here we revisit both the conditions under which strangelets can be produced in the Early Universe and the many phenomenological implications of their existence. Most of the paper discusses the limits on their mass distribution and a possible and simple scheme for their production. Finally, we discuss the most promising techniques to detect this type of objects., Comment: 12 pages, 12 figures

$f(R)$ gravity is one of the serious alternatives of general relativity having large range of astronomical consequences. In this work, we study Big Bang Nucleosynthesis (BBN) in $f(R)$ gravity theory. We consider modification to gravity due to the existence of primordial black holes in the radiation era which introduce additional degrees of freedom known as scalarons. We calculate the light element abundances by using the BBN code PArthENoPE. It is found that for a range of scalaron mass $(2.2-3.5) \times 10^4$ eV, the abundance of lithium is lowered by $3-4$ times the value predicted by general relativistic BBN which is a level desired to address the cosmological lithium problem. For the above scalaron mass range helium abundance is within observed bound. However, deuterium abundance is found to be increased by $3-6$ times the observed primordial abundance which calls for high efficiency of stellar formation and evolution processes for destruction of the same. A novel relation between scalaron mass and black hole mass has been used to estimate that the above scalaron mass range corresponds to primordial black holes of sub-planetary mass ($\sim 10^{19}$ g) serving as one of the potential non-baryonic dark matter candidates. We infer Big Bang equivalence of power law $f(R)$ gravity with primordial black holes., Comment: 14 pages, 1 figure, 2 subfigures, Comments are welcomed

We investigate the impact of the Dark Energy Spectroscopic Instrument (DESI) 2024 data on dark energy scenarios. We thus analyze three typologies of models, the first in which the cosmic speed up is related to thermodynamics, the second associated with Taylor expansions of the barotropic factor, whereas the third based on \emph{ad hoc} dark energy parameterizations. In this respect, we perform Monte Carlo Markov chain analyses, adopting the Metropolis-Hastings algorithm, of 12 models. To do so, we first work at the background, inferring \emph{a posteriori} kinematic quantities associated with each model. Afterwards, we obtain early time predictions, computing departures on the growth evolution with respect to the model that better fits DESI data. We find that the best model to fit data \emph{is not} the Chevallier-Polarski-Linder (CPL) parametrization, but rather a more complicated log-corrected dark energy contribution. To check the goodness of our findings, we further directly fit the product, $r_d h_0$, concluding that $r_d h_0$ is anticorrelated with the mass. This treatment is worked out by removing a precise data point placed at $z=0.51$. Surprisingly, in this case the results again align with the $\Lambda$CDM model, \emph{indicating that the possible tension between the concordance paradigm and the CPL model can be severely alleviated}. We conclude that future data points will be essential to clarify whether dynamical dark energy is really in tension with the $\Lambda$CDM model., Comment: 23 pages, 3 figures, 8 tables

We have developed a set of four fully coupled Boltzmann equations to precisely determine the relic density and temperature of dark matter by including three distinct sectors: dark matter, light scalar, and standard model sectors. The intricacies of heat transfer between DM and the SM sector through a light scalar particle are explored, inspired by stringent experimental constraints on the scalar-Higgs mixing angle and the DM-scalar coupling. Three distinct sectors emerge prior to DM freeze-out, requiring fully coupled Boltzmann equations to accurately compute relic density. Investigation of forbidden, resonance, and secluded DM scenarios demonstrates significant deviations between established methods and the novel approach with fully coupled Boltzmann equations. Despite increased computational demands, this emphasizes the need for improved precision in relic density calculations, underlining the importance of incorporating these equations in comprehensive analyses., Comment: 38 pages, 10 figures

We explore compactifications of the form of three tori and one circle in the framework of 11D supergravity. By imposing suitable gauge conditions and boundary conditions, we find that the four-dimensional FRW universe emerges as a solution representing cosmological D3-branes in the eleven-dimensional bulk. These specific compactification methods can produce cosmological inflation that aligns with the observational constraints set by the 2021 BICEP/Keck and Planck 2018 results. In the cosmological inflation models we construct, the inflaton can be interpreted as the conformal vibrations of extra dimensions with a size around 10^5 times the reduced Planck length. Additionally, we offer the theoretical predictions for the mass of the inflaton, and the tree-level Newton's gravity law between two massive point particles surrounded by a spherically symmetric distribution of the inflaton, which can reproduce the Tully-Fisher relation and explain the flat rotation curves of galaxies., Comment: 27 pages, 7 figures

The presence of an abundant population of low frequency photons at high redshifts (such as a radio background) can source leading order effects on the evolution of the matter and spin temperatures through rapid free-free absorptions. This effect, known as soft photon heating, can have a dramatic impact on the differential brightness temperature, $\Delta T_{\rm b}$, a central observable in $21$cm cosmology. Here, we introduce a semi-analytic framework to describe the dynamics of soft photon heating, providing a simplified set of evolution equations and a useful numerical scheme which can be used to study this generic effect. We also perform quasi-instantaneous and continuous soft photon injections to elucidate the different regimes in which soft photon heating is expected to impart a significant contribution to the global $21$cm signal and its fluctuations. We find that soft photon backgrounds produced after recombination with spectral index $\gamma > 3.0$ undergo significant free-free absorption, and therefore this heating effect cannot be neglected. The effect becomes stronger with steeper spectral index, and in some cases the injection of a synchrotron-like spectrum ($\gamma = 3.6$) can suppress the amplitude of $\Delta T_{\rm b}$ relative to the standard model prediction, making the global $21$cm signal even more difficult to detect in these scenarios., Comment: 19 pages, 10 figures, comments welcome! The accompanying soft photon heating code can be found at https://github.com/Bryce-Cyr/Soft_Photon_Heating

The redshifted 21-cm signal from the epoch of reionization (EoR) directly probes the ionization and thermal states of the intergalactic medium during that period. In particular, the distribution of the ionized regions around the radiating sources during EoR introduces scale-dependent features in the spherically-averaged EoR 21-cm signal power spectrum. The goal is to study these scale-dependent features at different stages of reionization using numerical simulations and build a source model-independent framework to probe the properties of the intergalactic medium using EoR 21-cm signal power spectrum measurements. Under the assumption of high spin temperature, we modelled the redshift evolution of the ratio of EoR 21-cm brightness temperature power spectrum and the corresponding density power spectrum using an ansatz consisting of a set of redshift and scale-independent parameters. This set of eight parameters probes the redshift evolution of the average ionization fraction and the quantities related to the morphology of the ionized regions. We have tested this ansatz on different reionization scenarios generated using different simulation algorithms and found that it is able to recover the redshift evolution of the average neutral fraction within an absolute deviation $\lesssim 0.1$. Our framework allows us to interpret 21-cm signal power spectra in terms of parameters related to the state of the IGM. This source model-independent framework can efficiently constrain reionization scenarios using multi-redshift power spectrum measurements with ongoing and future radio telescopes such as LOFAR, MWA, HERA, and SKA. This will add independent information regarding the EoR IGM properties., Comment: 16 pages, 13 figures, 2 tables, Accepted for publication in Astronomy and Astrophysics

We present a sample of over 100 highly X-ray luminous galaxy clusters at $z\sim$ 0.5-0.9, discovered by the extended Massive Cluster Survey (eMACS) in ROSAT All-Sky Survey (RASS) data. Follow-up observations of a subset at higher resolution and greater depth with the Chandra X-ray Observatory are used to map the gaseous intra-cluster medium, while strong-gravitational-lensing features identified in Hubble Space Telescope imaging allow us to constrain the total mass distribution. We present evidence of the exceptional gravitational-lensing power of these massive systems, search for substructure along the line of sight by mapping the radial velocities of cluster members obtained through extensive ground-based spectroscopy, and identify dramatic cases of galaxy evolution in high-density cluster environments. The available observations of the eMACS sample presented here provide a wealth of insights into the properties of very massive clusters ($\gtrsim 10^{15} M_\odot$) at $z > 0.5$, which act as powerful lenses to study galaxies in the very distant Universe. We also discuss the evolutionary state, galaxy population, and large-scale environment of eMACS clusters and release to the community all data and science products to further the understanding of the first generation of truly massive clusters to have formed in the Universe., Comment: Submitted to MNRAS, comments welcome! A version including the complete appendices is available at http://www.astro.dur.ac.uk/~ace/eMACS.pdf

JWST is discovering a large population of $z>4$ supermassive black holes (SMBHs) that are overmassive with respect to the stellar content of their hosts. A previous study developed a physical model to interpret this overmassive population as the result of quasar feedback acting on a compact host galaxy. In this Note, we apply this model to JADES GN 1146115, a dormant supermassive black hole at $z=6.7$ whose mass is $\sim40\%$ of the host's mass in stars and accreting at $\sim2\%$ of the Eddington limit. The host has been forming stars at the low rate of $\sim 1 \, \rm M_\odot \,yr^{-1}$ for the past $\sim 100$ Myr. Our model suggests that this galactic system is on the verge of a resurgence of global star formation activity. This transition comes after a period of domination by the effect of its overmassive black hole, whose duration is comparable to typical quasar lifetimes., Comment: Accepted on Research Notes of the AAS. This is a concise note (3 pages, 1 figure) regarding the direct application of the model described in arXiv:2401.04159 to the source presented in arXiv:2403.03872

Axion and axion-like particles (ALPs) are a prominent candidate for physics beyond the Standard Model, and can play an important role in cosmology, serving as dark matter or dark energy, or both, drawing motivation in part from the string theory axiverse. Axion-like particles (ALPs) can also arise as composite degrees of freedom following chiral symmetry breaking in a dark confining gauge theory, analogous to the Standard Model (SM) pion. A dark sector with arbitrary $N_f$ flavors of dark quarks leads to $N_f^2-1$ axion-like states, effectively a field theory axiverse (or '$\pi$-axiverse'). A portal to the visible sector can be achieved through the standard kinetic mixing between the dark photon and SM photon, generating millicharges for the dark quarks and consequently couplings, both parity-even and parity-odd, between the SM and the dark pions. This scenario has been studied for the $N_f=2$ case and more recently for a dark Standard Model with $N_f=6$. In this work, we study the spectrum of this field theory axiverse for an arbitrary number of flavors, and apply this to the example $N_f=10$. We calculate the couplings to the SM photon analogous to the conventional axion-photon coupling, including the $N_f$ and $N_c$ dependence, and compute the present and future constraints on the $N_f=10$, $N_c=3$, $\pi$-axiverse. We elucidate the accompanying 'bary-verse' of superheavy dark baryons, namely an ensemble of charged and neutral dark baryons with a mass set by the dark pion decay constant.

The power spectrum and voxel intensity distribution (VID) are two summary statistics that can be applied to condense the information encoded in line-intensity maps. The information contained in both summary statistics is highly complementary, and their combination allows for a major increase in precision of parameter estimation from line-intensity mapping (LIM) surveys. Until recently, combination of these statistics required simulation-based estimations of their covariance. In this work we leverage an analytical model of covariance between these observables to run a joint Fisher forecast focusing on the CO(1-0) rotational line targeted by the COMAP survey and a wider, shallower hypothetical iteration. We consider a generalized phenomenological non-CDM model, models with axion dark matter, and local primordial non-Gaussianity, to highlight where a combined analysis of the power spectrum and VID can be most useful. Our results demonstrate improvements in sensitivity to beyond-$\Lambda$CDM physics over analyses using either the power spectrum or VID on their own, by factors ranging from 2 to 50, showcasing the potential of joint analyses in unlocking new insights into fundamental physics with LIM surveys., Comment: 18 pages, 10 figures; comments welcome

Data from the James Webb Space Telescope have revealed an intriguing population of bright galaxies at high redshifts. In this work, we use extreme-value statistics to calculate the distribution (in UV magnitude) of the brightest galaxies in the redshift range $9 \lesssim z \lesssim 16$. We combine the Generalised Extreme Value (GEV) approach with modelling of the galaxy luminosity function. We obtain predictions of the brightest galaxies for a suite of luminosity functions, including the Schechter and double power law functions, as well as a model parametrised by the stellar formation efficiency $f_*$. We find that the \textit{JWST} data is broadly consistent with $f_*$ of $5\%-10\%$, and that the brightest galaxy at $z\sim16$ will have $M_{\rm UV}\approx -23.5^{0.8}_{0.4}$. If $f_*$ is dependent on halo mass, we predict $M_{\rm UV}\approx -22.5^{0.5}_{1.5}$ for such an object. We show that extreme-value statistics not only predicts the magnitude of the brightest galaxies at high redshifts, but may also be able to distinguish between models of star formation in high-redshift galaxies., Comment: 10 pages, 8 figures, submitted to MNRAS

The formation and growth of black holes can strongly influence the distribution of dark matter around them. I discuss here the different types of dark matter overdensities around black holes, including dark matter cusps, spikes, mounds, crests, and gravitational atoms. I then review recent results on the evolution of a black holes binary in presence of dark matter, focusing on the energy transfer between binary and dark matter induced by dynamical friction. Finally, I present the prospects for studying dark matter with gravitational wave observations, and argue that future interferometers might be able to detect and characterise dark matter overdensities around black holes., Comment: 12 pages, 3 figures. Review article, to appear in the proceedings of the 182nd Nobel Symposium

We forecast constraints on minimal model-independent parametrisations of several Modified Gravity theories using mock Stage-IV cosmic shear data. We include nonlinear effects and screening, which ensures recovery of General Relativity on small scales. We introduce a power spectrum emulator to accelerate our analysis and evaluate the robustness of the growth index parametrisation with respect to two cosmologies: $\Lambda$CDM and the normal branch of the DGP model. We forecast the uncertainties on the growth index $\gamma$ to be of the order $\sim 10\%$. We find that our halo-model based screening approach demonstrates excellent performance, meeting the precision requirements of Stage-IV surveys. However, neglecting the screening transition results in biased predictions for cosmological parameters. We find that the screening transition shows significant degeneracy with baryonic feedback, requiring a much better understanding of baryonic physics for its detection. Massive neutrinos effects are less prominent and challenging to detect solely with cosmic shear data., Comment: 22 pages, 16 figures, 2 tables plus Appendices. Our power spectrum boost emulators for extended cosmologies are publicly available at https://github.com/nebblu/ReACT-emus/tree/main/emulators

The distribution of masses of neutron stars, particularly the maximum mass value, is considered a probe of their formation, evolution and internal physics (i.e., equation of state). This mass distribution could in principle be inferred from the detection of gravitational waves from binary neutron star mergers. Using mock catalogues of $10^5$ dark sirens events, expected to be detected by Einstein Telescope over an operational period of $\sim1\, \rm year$ , we show how the biased luminosity distance measurement induced by gravitational lensing affects the inferred redshift and mass of the merger. This results in higher observed masses than expected. Up to $2\%$ of the events are predicted to fall above the maximum allowed neutron star mass depending on the intrinsic mass distribution and signal-to-noise ratio threshold adopted. The underlying true mass distribution and maximum mass could still be approximately recovered in the case of bright standard sirens., Comment: 9 pages, 5 figures, 1 table

To fully exploit the data from next generation surveys, we need an accurate modelling of the matter power spectrum up to non-linear scales. Therefore in this work we present the halo model reaction framework for the Generalized Cubic Covariant Galileon (GCCG) model, a modified gravity model within the Horndeski class of theories which extends the cubic covariant Galileon (G3) by including power laws of the derivatives of the scalar field in the K-essence and cubic terms. We modify the publicly available software ReACT for the GCCG in order to obtain an accurate prediction of the non-linear power spectrum. In the limit of the G3 model we compare the modified ReACT code to $N$-body simulations and we find agreement within 5\% for a wide range of scales and redshifts. We then study the relevant effects of the modifications introduced by the GCCG on the non-linear matter power spectrum. Finally, we provide forecasts from spectroscopic and photometric primary probes by next generation surveys using a Fisher matrix method. We show that future data will be able to constrain at 1$\sigma$ the two additional parameters of the model at the percent level and that considering non-linear corrections to the matter power spectrum beyond the linear regime is crucial to obtain this result., Comment: 17 pages, 7 figures, code available at https://github.com/nebblu/ACTio-ReACTio

We examine the thin accretion disk behaviors surrounding black holes embedded in cold dark matter halos and scalar field dark matter halos. We first calculate the event horizons and derive the equations of motion and effective potential in black hole geometries with different dark matter halos. We then compute the specific energy, specific angular momentum, and angular velocity of particles moving along circular orbits. We also derive the effective potentials to find the locations of the innermost stable circular orbit (ISCO) and compare them to the Schwarzschild and Kerr black holes without the dark matter haloes. We also use the observed ISCO of the supermassive black hole at the Galactic Center of the Milky Way, Sagittarius A*, to constrain the dark matter halos and discuss the astrophysical Gamma-ray bursts (GRBs) generation from systems.

Gravitational clustering in our cosmic vicinity is expected to lead to an enhancement of the local density of relic neutrinos. We derive expressions for the neutrino density, using a perturbative approach to kinetic field theory and perturbative solutions of the Vlasov equation up to second order. Our work reveals that both formalisms give exactly the same results and can thus be considered equivalent. Numerical evaluation of the local relic neutrino density at first and second order provides some fundamental insights into the frequently applied approach of linear response to neutrino clustering (also known as the Gilbert equation). Against the naive expectation, including the second-order contribution does not lead to an improvement of the prediction for the local relic neutrino density but to a dramatic overestimation. This is because perturbation theory breaks down in a momentum-dependent fashion and in particular for densities well below unity., Comment: 34 pages, 7 figures

We use continuous wavelet transform techniques to construct the global and environment-dependent wavelet statistics, such as energy spectrum and kurtosis, to study the fluctuation and intermittency of the turbulent motion in the cosmic fluid velocity field with the IllustrisTNG simulation data. We find that the peak scales of the energy spectrum and the spectral ratio define two characteristic scales, which can be regarded as the integral scale and the dissipation scale of turbulence, respectively, so that the energy spectrum can be divided into the energy-containing range, the inertial range and the dissipation range of turbulence. The wavelet kurtosis is an increasing function of the wavenumber $k$, first grows rapidly then slowly with $k$, indicating that the cosmic fluid becomes increasingly intermittent with $k$. In the energy-containing range, the energy spectrum increases significantly from $z = 2$ to $1$, but remains almost unchanged from $z = 1$ to $0$. We find that both the environment-dependent spectrum and kurtosis are similar to the global ones, and the magnitude of the spectrum is smallest in the lowest-density and largest in the highest-density environment, suggesting that the cosmic fluid is more turbulent in a high-density than in a low-density environment. In the inertial range, the exponent of the energy spectrum is steeper than not only the Kolmogorov but also the Burgers exponent, suggesting that there may be more complex mechanisms for energy transfer than Kolmogorov and Burgers turbulence., Comment: 15 pages, 9 figures, 1 table, comments welcome

Density profiles are important tools in galaxy cluster research, offering insights into clusters dynamical states and their relationship with the broader Universe. While these profiles provide valuable information about the matter content of the Universe, their utility in understanding its dark energy component has remained limited due a lack of tools allowing us to study the transition from cluster portions that are relaxed and infalling, to those that are merging with the Hubble flow. In this work we investigate signatures of this transition in stacked density profiles of simulated cluster-sized halos at different redshifts. To highlight the Hubble flow around clusters we use their turnaround radius to normalize stacked simulated density profiles and calculate their logarithmic slope. Then, we complement our analysis by modeling the outer portions of these profiles assuming Gaussian early Universe statistics and spherical collapse without shell-crossing. We find the logarithmic slope of median cluster density profiles beyond the turnaround radius - where the Hubble flow dominates - to be Universal and well described by our model. Importantly, we find the slope of the profiles to diverge from the SCM prediction from within the turnaround radius where the actual profiles exhibit caustics which give rise to the splashback feature. We suggest utilizing this divergence from the spherical collapse model as a method to identify the turnaround radius in stacked cluster density profiles, offering a new perspective on understanding cluster dynamics and their cosmological implications., Comment: 8 pages, 5 figures, submitted to A&A

We present model-marginalized limits on the six standard $\Lambda$CDM cosmological parameters ($\Omega_{\rm c} h^2$, $\Omega_{\rm b} h^2$, $\theta_{\rm MC}$, $\tau_{\rm reio}$, $n_s$ and $A_s$), as well as on selected derived quantities ($H_0$, $\Omega_{\rm m}$, $\sigma_8$, $S_8$ and $r_{\rm drag}$), obtained by considering three independent Cosmic Microwave Background (CMB) experiments: the Planck satellite, the Atacama Cosmology Telescope, and South Pole Telescope. We also consider low redshift observations in the form of Baryon Acoustic Oscillation (BAO) data from the SDSS-IV eBOSS survey and Supernovae (SN) distance moduli measurements from the Pantheon-Plus catalog. The marginalized errors are stable against the different fiducial cosmologies explored in this study. The largest impact on the parameter accuracy is produced by varying the effective number of relativistic degrees of freedom ($N_{\rm eff}$) or the lensing amplitude ($A_{\rm lens}$). Nevertheless the marginalized errors on some derived parameters such as $H_0$ or $\Omega_{\rm m}$ can be up to two orders of magnitude larger than in the canonical $\Lambda$CDM scenario when considering only CMB data. In these cases, low redshift measurements are crucial for restoring the stability of the marginalized cosmological errors computed here. Overall, our results underscore remarkable stability in the mean values and precision of the main cosmological parameters, making irrelevant the choice of different possible cosmological scenarios once both high and low redshift probes are fully accounted for. The very same results should be understood as a tool to test exotic cosmological scenarios, as the marginalized values should be used in numerical analyses due to their robustness and slightly larger errors, providing a more realistic and conservative approach., Comment: 18 pages, 11 figures, 12 tables. Prepared for submission to PRD

We calculate the abundance of UV-bright galaxies in the presence of ultralight axion dark matter (DM), finding that axions suppress their formation but with a non-trivial dependence on redshift and luminosity. We thus set the first limits on axion DM using a combination of Planck cosmic microwave background (CMB) and UV luminosity function (UVLF) data. We exclude a single axion as all the DM for m_{ax} < 10^{-21.6} eV and limit axions with -26 < log(m_{ax}/eV) < -23 to be less than 22% of the DM (both limits at 95% credibility). These limits use UVLF measurements from 24,000 sources from the Hubble Space Telescope (HST) that probe small-scale structure at redshifts 4 < z < 10 inaccessible to other cosmological observables. We marginalize over a parametric model that connects halo mass and UV luminosity that has been shown to fit the results of hydrodynamical simulations. Our results bridge a window in axion mass and DM fraction previously unconstrained by cosmological data, between large-scale CMB and galaxy clustering and the small-scale Lyman-alpha forest. These high-z measurements provide a powerful consistency check of low-z tests of axion DM, which include the recent hint for a sub-dominant ULA DM fraction in Lyman-alpha forest data. We also consider a sample of 25 spectroscopically-confirmed high-z (z > 10) galaxies from the James Webb Space Telescope (JWST). We find that these data are consistent with the HST UVLF assuming LambdaCDM and our flexible parametric model of UV luminosity. Combining HST and JWST UVLF data does not improve our constraints beyond HST alone, but future JWST measurements have the potential to improve these results significantly. We also find an excess of low-mass halos (< 10^9 M_\odot) at z < 3, which could be probed by sub-galactic structure probes (e.g., stellar streams, satellite galaxies and strong lensing)., Comment: 23 pages, 20 figures

We study the prospects for measuring the cosmological distribution and abundance of ionized electrons in the intergalactic medium using galaxy surveys. Optical light from distant galaxies is subject to Thomson screening by intervening electrons which distorts the observed galaxy number density, similar to the effect of weak gravitational lensing magnification. We construct an estimator for the optical-depth fluctuations from the statistical anisotropies of galaxy number counts induced by the spatially-varying optical-depth field. We find near-future galaxy surveys can detect this signal at signal-to-noise above $\sim10$ depending on galaxy survey specifications. We highlight various science cases for the measurement of optical-depth fluctuations., Comment: 8+9 pages, 11 figures, comments welcome

Deep JWST imaging of the giant galaxy cluster Abell 2744, at redshift $z=0.308$, is used to explore the features of its rich population of globular clusters (GCs), building on our initial survey of the system (Harris & Reina-Campos 2023). We use the photometry of more than $10,000$ GCs over a three-magnitude range to construct the GC luminosity function (GCLF) and color distribution (CDF). These results now specifically account for photometric incompleteness as a function of location relative to the five giant galaxies that dominate the gravitational potential of A2744. The total GC population in A2744 is estimated at $N_{\rm GC} \geq 1.1 \times 10^5$, consistent with its high total mass. We also directly compare the observed distributions with theoretical predictions for GC populations drawn from the recent EMP-Pathfinder simulations (Reina-Campos et al. 2022), viewed at the same 3.5 Gyr lookback time as the cluster. The simulations match the observations well, with the only notable disagreement being that the simulations predict larger numbers of GCs at high metallicity formed after $z\simeq2$ than are seen in the data., Comment: 15 pages, 9 figures; submitted to ApJ

The James Webb Space Telescope (JWST) is revolutionizing our understanding of black holes formation and growth in the early Universe. However, JWST has also revealed that some of the classical diagnostics, such as the BPT diagrams and X-ray emission, often fail to identify narrow line TypeII active galactic nuclei (AGN) at high redshift. Here we present three new rest-frame optical diagnostic diagrams leveraging the [OIII]$\lambda4363$ auroral line, which has been detected in several JWST spectra. Specifically, we show that high values of the [OIII]$\lambda4363/$H$\gamma$ ratio provide a sufficient (but not necessary) condition to identify the presence of an AGN, both based on empirical calibrations (using local and high-redshift sources) and a broad range of photoionization models. These diagnostics are able to separate much of the AGN population from Star Forming Galaxies (SFGs). This is because the average energy of AGN's ionizing photons is higher than that of young stars in SFGs, hence AGN can more efficiently heat the gas, therefore boosting the [OIII]$\lambda4363$ line. We also found independent indications of AGN activity in some high-redshift sources that were not previously identified as AGN with the traditional diagnostics diagrams, but that are placed in the AGN region of the diagnostics presented in this work. We note that, conversely, low values of [OIII]$\lambda4363/$H$\gamma$ can be associated either with SFGs or AGN excitation. We note that the fact that strong auroral lines are often associated with AGN does not imply that they cannot be used for direct metallicity measurements (provided that proper ionization corrections are applied), but it does affect the calibration of strong line metallicity diagnostics., Comment: Submitted to A&A. 16 pages, 7 figures. Comments are welcome

We explore the impact of corrections to the propagation on the waveforms of gravitationally lensed gravitational waves under the geometrical optics approximation, focusing on both uniform cosmological modifications and local modifications localized around lensing objects. By adopting a model-independent phenomenological approach, we systematically investigate the effects of these modifications in strong lensing scenarios, where detection of multiple images is expected. Our analysis reveals that cosmological modifications can yield corrections to the time delay that remain to be minor compared with the effects that accumulate over the whole propagation process, which are present also in the unlensed waveform. By contrast, local modifications around lensing objects can alter the image position and also the magnification factor, which is potentially polarization-selective and frequency-dependent. In some case we can have image disappearance as well as signal amplification. Furthermore, we demonstrate that such modifications can cause degradation of waveform match with the templates based on general relativity. This study highlights the importance of considering waveform modifications to search for the signature of modified propagation or the existence of extra polarization modes, and proposes potential observational targets., Comment: 18 pages, 11 figures

Almost 50% of galaxies in the local Universe are in clusters or groups coexisting with both hot and cold gas components. In the present study, we observationally probed the cold-gas content of X-ray-selected massive galaxy clusters with spectroscopic redshift measured from the SDSS/SPIDERS survey. This paper focuses on the most massive structures: galaxy clusters with a mean mass of M$_{500c}$ = 2.7$\times 10^{14}$ M$_{\odot}$. We used a large number of background quasar optical spectra from SDSS DR16 to probe the diffuse T$=$10$^4$K gas in their intracluster medium. We first analysed a sample of spectra with known MgII absorbers, and then blindly stacked about 16,000 archival spectra at the redshifts of the foreground galaxy clusters. We tentatively ($3.7 \sigma$ significance) detect MgII in the clusters with an equivalent width EW(MgII $\lambda$2796) of 0.056$\pm$0.015 \r{A}, corresponding to a column density of log [N(MgII)/cm$^{-2}$]=12.12$\pm0.1$. We tested our methodology by generating 22,000 mock SDSS spectra with MgII absorbers from TNG50 cosmological magnetohydrodynamical simulations, combining photo-ionisation modelling and ray tracing. We also performed bootstrapping stacking at different cluster redshifts and stacked quasar spectra with no intervening clusters in the line of sight to measure the significance of our detection. These results are in line with the findings of recent, similar observational studies but challenge predictions from TNG simulations. Together, our findings indicate that large amounts of cold gas may be found in the most massive structures of the Universe.

The capability of Cosmic Inflation to explain the latest Cosmic Microwave Background and Baryonic Acoustic Oscillation data is assessed by performing Bayesian model comparison within the landscape of nearly three-hundred models of single-field slow-roll inflation. We present the first Bayesian data analysis based on the third-order slow-roll primordial power spectra. In particular, the fourth Hubble-flow function $\epsilon_4$ remains unbounded while the third function verifies, at two-sigma, $\epsilon_{3}\in[-0.4,0.5]$, which is perfectly compatible with the slow-roll predictions for the running of the spectral index. We also observe some residual excess of $B$-modes within the BICEP/Keck data favoring, at a non-statistically significant level, non-vanishing primordial tensor modes: $\log(\epsilon_{1}) > -3.9$, at $68\%$ confidence level. Then, for 283 models of single-field inflation, we compute the Bayesian evidence, the Bayesian dimensionality and the marginalized posteriors of all the models' parameters, including the ones associated with the reheating era. The average information gain on the reheating parameter $R_\mathrm{reh}$ reaches $1.3 \pm 0.18$ bits, which is more than a factor two improvement compared to the first Planck data release. As such, inflationary model predictions cannot meet data accuracy without specifying, or marginalizing over, the reheating kinematics. We also find that more than $40\%$ of the scenarios are now strongly disfavored, which shows that the constraining power of cosmological data is winning against the increase of the number of proposed models. In addition, about $20\%$ of all models have evidences within the most probable region and are all favored according to the Jeffreys' scale of Bayesian evidences., Comment: 77 pages, 37 figures, uses jcappub

We propose a new model of scalar field dark matter interacting with dark energy. Adopting a fluid description of the dark matter field in the regime of rapid oscillations, we find that the equation of state for dark matter is non-zero and even becomes increasingly negative at late times during dark energy domination. Furthermore, the speed of sound of dark matter is non-vanishing at all length scales, and a non-adiabatic pressure contribution arises. The results indicate that there are still unexplored possible interactions within the dark sector that lead to novel background effects and can impact structure formation processes., Comment: 20 pages, 3 figures

We study the dynamical evolution of superradiant instabilities of rotating black holes for multiple axion fields with comparable masses, motivated by string theory constructions, which typically exhibit a large number of light axions, with a broad range of masses. We show, in particular, that even though superradiant clouds for the heavier axion species grow faster, they are eventually reabsorbed by the black hole as the latter amplifies the lighter axion field(s), analogously to the dynamics of different species competing for the same resources in an ecosystem. We also incorporate in our study the effects of accretion and gravitational wave emission. We further demonstrate that the existence of multiple axion species with comparable masses may have a substantial impact on the stochastic gravitational wave background produced by axion clouds around black hole binary merger remnants, which could be probed with planned detectors., Comment: 14 pages, 11 figures

We present novel findings concerning the parameter space of axion stars, extended object forming in dense dark matter environments through gravitational condensation. We emphasize their formation within the dense minihalos that potentially surround primordial black holes and in axion miniclusters. Our study investigates the relation between the radius and mass of an axion star in these dense surroundings, revealing distinct morphological characteristics compared to isolated scenarios. We explore the implications of these results when applied to gravitational microlensing from extended objects and gravitational wave detection from compact binaries, leading to insights on the observational constraints from such ``halo'' axion stars. We provide a constraint on the fraction of the galactic population of axion stars from their contribution to the microlensing events from the EROS-2 survey, using the numerical resolution of the Schr\"odinger-Poisson equation., Comment: 19 pages + references, 8 figures. Part of COST actions CA21106 and CA21136