arXiv subjects

David Camarena

Publications and source records attributed to David Camarena.

At least 19 recordsLinked to original sources

arXiv2026

Limits of self-interacting neutrinos from the BAO and CMB phase shift

Neutrinos with Standard Model interactions free-stream in the early Universe, leaving a distinct phase shift in the pattern of baryon acoustic oscillations (BAO). When isolated, this phase shift allows one to robustly infer the presence of the cosmic neutrino background in BAO and cosmic microwave background (CMB) data independently of other cosmological parameters. While in the context of the Standard Model, this phase shift follows a known scale-dependent relation, new physics in the cosmic neutrino background could alter the overall shape of this feature. In this paper, we discuss how changes in the neutrino phase shift could be used to constrain self-interactions among neutrinos. We produce simple models for this phase-shift assuming universal self-interactions, and use these in order to understand what constraining power is available for the strength of such interactions in BAO and CMB data. We find that, although challenging, it may be possible to use a detection of the phase to put a more robust limit on the strength of the self-interaction, $G_{\mathrm{eff}}$, which at present suffers from bimodality in cosmological constraints. Our forecast analysis reveals that BAO data alone will not provide the precision needed to tightly constrain self-interactions; however, the combined analysis of the phase shift signature in both CMB and BAO can potentially provide a way to detect the impact of new neutrino interactions. Our results could be extended upon for models with non-universal interactions.

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arXiv2025

DESIgning concordant distances in the age of precision cosmology: the impact of density fluctuations

Discrepancies between distance measurements and $Λ$CDM predictions reveal notable features in the distance-redshift relation, possibly suggesting the presence of an evolving dark energy component. Given the central role of the Friedmann-Lemaître-Robertson-Walker (FLRW) metric in modeling cosmological distances, we investigate here whether these features instead point to a possible departure from the fundamental FLRW symmetries. Exploiting the transverse and line-of-sight distances provided by baryonic acoustic oscillations (BAO) observations, we demonstrate that observed distances hint at a slight but systematic preference for an anisotropic expansion rate emerging regardless of the dark energy model considered. Leveraging this non-FLRW feature, we investigate an inhomogeneous extension of the $Λ$CDM model that naturally provides an anisotropic expansion rate. Our analysis demonstrates that models featuring spherical overdensities can explain BAO, supernova, and cosmic microwave background data, providing fits statistically indistinguishable from those obtained with a phantom dark energy scenario. When Pantheon+ data is considered, our analysis challenges the FLRW framework at $2.8σ$ and yields scenarios that can be interpreted as subtle but non-negligible deviations from the FLRW metric. When DESY5 supernovae are considered instead, deviations are notably more significant, yielding scenarios that mildly violate the Copernican principle and exclude the FLRW assumption at $5.2σ$. Overall, our results motivate a more in-depth investigation of whether the perfectly homogeneous and isotropic FLRW paradigm can still be assumed to accurately predict cosmological distances in the era of precision cosmology.

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arXiv2025

Strong constraints on a simple self-interacting neutrino cosmology

Some cosmic microwave background (CMB) data allow a cosmological scenario in which the free streaming of neutrinos is delayed until close to matter-radiation equality. Interestingly, recent analyses have revealed that large-scale structure (LSS) data also align with this scenario, discarding the possibility of an accidental feature in the CMB sky and calling for further investigation into the free-streaming nature of neutrinos. By assuming a simple representation of self-interacting neutrinos, we investigate whether this nonstandard scenario can accommodate a consistent cosmology for both the CMB power spectra and the large-scale distribution of galaxies simultaneously. Employing three different approaches - a profile likelihood exploration, a nested sampling method, and a heuristic Metropolis-Hasting approximation - we exhaustively explore the parameter space and demonstrate that galaxy data exacerbates the challenge already posed by the Planck polarization data for this nonstandard scenario. We find that the Bayes factor disfavor strong interactions among neutrinos over the $Λ$CDM and $Λ$CDM + $N_\mathrm{eff}$ + $\sum m_ν$ models with odds of $7:10000$ and $23:1000$, respectively, providing large evidence against the simple self-interacting neutrino model. Our analysis emphasizes the need to consider a broader range of phenomenologies in the early Universe. We also highlight significant numerical and theoretical challenges ahead in uncovering the exact nature of the feature observed in the data or, ultimately, confirming the standard chronological evolution of the Universe.

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arXiv2024

Constraining LLTB models with galaxy cluster counts from next generation surveys

The Universe's assumed homogeneity and isotropy is known as the cosmological principle. It is one of the assumptions that lead to the Friedmann-Lema\^ıtre-Robertson-Walker (FLRW) metric and it is a cornerstone of modern cosmology, because the metric plays a crucial role into the determination of the cosmological observables. Thus, it is of paramount importance to question this principle and perform observational tests that may falsify this hypothesis. Here we explore the use of galaxy cluster counts as a probe of a large-scale inhomogeneity, which is a novel approach for the study of inhomogeneous models, and to determine the precision with which future galaxy cluster surveys will be able to test the cosmological principle. We present forecast constraints on the inhomogeneous Lema\^ıtre-Tolman-Bondi (LTB) model with a cosmological constant and cold dark matter, from a combination of simulated data according to a compilation of `Stage-IV' galaxy surveys following a methodology that involves the use of a mass function correction from numerical $N$-body simulations of an LTB cosmology. When considering the \lcdm fiducial model as a baseline for constructing our mock catalogs, we find that our combination of the forthcoming cluster surveys, will improve the constraints on the cosmological principle parameters as well on the FLRW parameters by about $50\%$ with respect to previous similar forecasts performed using geometrical and linear growth of structure probes, with $\pm20\%$ variations depending on the level of knowledge of systematic effects.These results indicate that galaxy cluster abundances are sensitive probes of inhomogeneity, and that next-generation galaxy cluster surveys, will thoroughly test homogeneity at cosmological scales, tightening the constraints on possible violations of the cosmological principle in the framework of $Λ$LTB scenarios. (Abridged)

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arXiv2024

Bayesian analysis of a Unified Dark Matter model with transition: can it alleviate the $H_{0}$ tension?

We consider cosmological models in which Dark Matter (DM) and Dark Energy (DE) are described by a single component, dubbed Unified Dark Matter (UDM) models, in which the DE-like part can have an equation state $<-1$ at late times without violating the null energy condition. In this paper, we investigate whether this feature can relieve the Hubble tension. We perform a Bayesian analysis of the model using SNIa data from Pantheon, the CMB distance prior from Planck, and the prior on the absolute magnitude $M$ of SNIa from SH0ES. Using the prior, the data suggests a smooth transition taking place at redshifts $z_{\rm t} \simeq 2.85$, which provides a value $H_0=69.64\pm 0.88$ for the Hubble constant, slightly alleviating the tension by $\sim 1.5 σ$. Without it, we obtain $H_0 = 67.6^{+1.3}_{-0.82}$ and a transition happening at $z_t=1.36$. We also discuss the importance of using the prior on $M$ for constraining this model.

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arXiv2023

The two-mode puzzle: Confronting self-interacting neutrinos with the full shape of the galaxy power spectrum

A cosmological scenario in which the onset of neutrino free streaming in the early Universe is delayed until close to the epoch of matter-radiation equality has been shown to provide a good fit to some cosmic microwave background (CMB) data, while being somewhat disfavored by Planck CMB polarization data. To clarify this situation, we investigate in this paper CMB-independent constraints on this scenario from the Full Shape of the galaxy power spectrum. Although this scenario predicts significant changes to the linear matter power spectrum, we find that it can provide a good fit to the galaxy power spectrum data. Interestingly, we show that the data display a modest preference for a delayed onset of neutrino free streaming over the standard model of cosmology, which is driven by the galaxy power spectrum data on mildly non-linear scales. This conclusion is supported by both profile likelihood and Bayesian exploration analyses, showing robustness of the results. Compared to the standard cosmological paradigm, this scenario predicts a significant suppression of structure on subgalactic scales. While our analysis relies on the simplest cosmological representation of neutrino self-interactions, we argue that this persistent - and somehow consistent - picture in which neutrino free streaming is delayed motivates the exploration of particle models capable of reconciling all CMB, large-scale structure, and laboratory data.

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arXiv2023

The tension in the absolute magnitude of Type Ia supernovae

This study aims to elucidate the tension in the Hubble constant ($H_0$), a key metric in cosmology representing the universe's expansion rate. Conflicting results from independent measurements such as the Planck satellite mission and the SH0ES collaboration have sparked interest in exploring alternative cosmological models. We extend the analysis by SH0ES to an arbitrary cosmographic model, obtaining a competitive local $H_0$ determination which only assumes the standard flat $Λ$CDM model ($73.14 \pm 1.10$ km/s/Mpc), and another which only assumes the FLRW metric ($74.56 \pm 1.61$ km/s/Mpc). The study also stresses the importance of the supernova magnitude calibration ($M_B$) in cosmological inference and highlights the tension in $M_B$ when supernovae are calibrated either by CMB and BAO observations or the first two rungs of the cosmic distance ladder. This discrepancy, independent of the physics involved, suggests that models solely changing the Hubble flow and maintaining a sound horizon distance consistent with CMB, fail to explain the discrepancy between early- and late-time measurements of $H_0$.

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arXiv2022

A void in the Hubble tension? The end of the line for the Hubble bubble

The Universe may feature large-scale inhomogeneities beyond the standard paradigm, implying that statistical homogeneity and isotropy may be reached only on much larger scales than the usually assumed $\sim$100 Mpc. This means that we are not necessarily typical observers and that the Copernican principle could be recovered only on super-Hubble scales. Here, we do not assume the validity of the Copernican principle and let Cosmic Microwave Background, Baryon Acoustic Oscillations, type Ia supernovae, local $H_0$, cosmic chronometers, Compton y-distortion and kinetic Sunyaev-Zeldovich observations constrain the geometrical degrees of freedom of the local structure, which we parametrize via the $Λ$LTB model -- basically a non-linear radial perturbation of a FLRW metric. In order to quantify if a non-Copernican structure could explain away the Hubble tension, we pay careful attention to computing the Hubble constant in an inhomogeneous universe, and we adopt model selection via both the Bayes factor and the Akaike information criterion. Our results show that, while the $Λ$LTB model can successfully explain away the $H_0$ tension, it is favored with respect to the $Λ$CDM model only if one solely considers supernovae in the redshift range that is used to fit the Hubble constant, that is, $0.023<z<0.15$. If one considers all the supernova sample, then the $H_0$ tension is not solved and the support for the $Λ$LTB model vanishes. Combined with other data sets, this solution to the Hubble tension barely helps. Finally, we have reconstructed our local spacetime. We have found that data are best fit by a shallow void with $δ_L \approx -0.04$ and $r^{\mathrm{out}}_L \approx 300$ Mpc, which, interestingly, lies on the border of the 95\% credible region relative to the standard model expectation.

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arXiv2022

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

In this paper we will list a few important goals that need to be addressed in the next decade, also taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant $H_0$, the $σ_8$--$S_8$ tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the $5.0\,σ$ tension between the {\it Planck} CMB estimate of the Hubble constant $H_0$ and the SH0ES collaboration measurements. After showing the $H_0$ evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the {\it Planck} CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density $Ω_m$, and the amplitude or rate of the growth of structure ($σ_8,fσ_8$). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the $H_0$--$S_8$ tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals.[Abridged]

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arXiv2022

Late-transition vs smooth $H(z)$ deformation models for the resolution of the Hubble crisis

Gravitational transitions at low redshifts ($z_t<0.1$) have been recently proposed as a solution to the Hubble and growth tensions. Such transitions would naturally lead to a transition in the absolute magnitude $M$ of type Ia supernovae (SnIa) at $z_t$ (Late $M$ Transitions - $LMT$) and possibly in the dark energy equation of state parameter $w$ (Late $w-M$ Transitions - $LwMT$). Here, we compare the quality of fit to cosmological data of this class of models, with the corresponding quality of fit of the cosmological constant model ($Λ$CDM) and some of the best smooth $H(z)$ deformation models ($w$CDM, CPL, PEDE). We also perform model selection via the Akaike Information Criterion and the Bayes factor. We use the full CMB temperature anisotropy spectrum data, the baryon acoustic oscillations (BAO) data, the Pantheon SnIa data, the SnIa absolute magnitude $M$ as determined by Cepheid calibrators and the value of the Hubble constant $H_0$ as determined by local SnIa calibrated using Cepheids. We find that smooth $H(z)$ deformation models perform worse than transition models for the following reasons: 1) They have a worse fit to low-$z$ geometric probes (BAO and SnIa data); 2) They favor values of the SnIa absolute magnitude $M$ that are lower as compared to the value $M_c$ obtained with local Cepheid calibrators at $z<0.01$; 3) They tend to worsen the $Ω_\mathrm{m,0}-σ_\mathrm{8,0}$ growth tension. We also find that the $w-M$ transition model ($LwMT$) does not provide a better quality of fit to cosmological data than a pure $M$ transition model ($LMT$) where $w$ is fixed to the \lcdm value $w=-1$ at all redshifts. We conclude that the $LMT$ model has significant statistical advantages over smooth late-time $H(z)$ deformation models in addressing the Hubble crisis.

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arXiv2021

The Copernican principle in light of the latest cosmological data

We pursue a program to confront observations with inhomogeneous extensions of the FLRW metric. The main idea is to test the Copernican principle rather than assuming it a priori. We consider the $Λ$CDM model endowed with a spherical $Λ$LTB inhomogeneity around us, that is, we assume isotropy and test the hypothesis of homogeneity. We confront the $Λ$LTB model with the latest available data from CMB, BAO, type Ia supernovae, local $H_0$, cosmic chronometers, Compton y-distortion and kinetic Sunyaev-Zeldovich effect. We find that these data can constrain tightly this extra inhomogeneity, almost to the cosmic variance level: on scales $\gtrsim 100$ Mpc structures can have a small non-Copernican effective contrast of just $δ_L \sim 0.01$. Furthermore, the constraints on the standard $Λ$CDM parameters are not weakened after marginalizing over the parameters that model the local structure, to which we assign ignorance priors. In other words, dropping the Copernican principle assumption does not imply worse constraints on the cosmological parameters. This positive result confirms that the present and future data can be meaningfully analyzed within the framework of inhomogeneous cosmology.

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arXiv2021

On the use of the local prior on the absolute magnitude of Type Ia supernovae in cosmological inference

A dark-energy which behaves as the cosmological constant until a sudden phantom transition at very-low redshift ($z<0.1$) seems to solve the >4$σ$ disagreement between the local and high-redshift determinations of the Hubble constant, while maintaining the phenomenological success of the $Λ$CDM model with respect to the other observables. Here, we show that such a hockey-stick dark energy cannot solve the $H_0$ crisis. The basic reason is that the supernova absolute magnitude $M_B$ that is used to derive the local $H_0$ constraint is not compatible with the $M_B$ that is necessary to fit supernova, BAO and CMB data, and this disagreement is not solved by a sudden phantom transition at very-low redshift. We make use of this example to show why it is preferable to adopt in the statistical analyses the prior on $M_B$ as an alternative to the prior on $H_0$. The three reasons are: i) one avoids potential double counting of low-redshift supernovae, ii) one avoids assuming the validity of cosmography, in particular fixing the deceleration parameter to the standard model value $q_0=-0.55$, iii) one includes in the analysis the fact that $M_B$ is constrained by local calibration, an information which would otherwise be neglected in the analysis, biasing both model selection and parameter constraints. We provide the priors on $M_B$ relative to the recent Pantheon and DES-SN3YR supernova catalogs. We also provide a Gaussian joint prior on $H_0$ and $q_0$ that generalizes the prior on $H_0$ by SH0ES.

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arXiv2020

Cosmology Intertwined III: $f σ_8$ and $S_8$

The standard $Λ$ Cold Dark Matter cosmological model provides a wonderful fit to current cosmological data, but a few tensions and anomalies became statistically significant with the latest data analyses. While these anomalies could be due to the presence of systematic errors in the experiments, they could also indicate the need for new physics beyond the standard model. In this Letter of Interest we focus on the tension of the Planck data with weak lensing measurements and redshift surveys, about the value of the matter energy density $Ω_m$, and the amplitude or rate of the growth of structure ($σ_8,fσ_8$). We list a few interesting models for solving this tension, and we discuss the importance of trying to fit with a single model a full array of data and not just one parameter at a time.

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arXiv2020

Cosmology Intertwined II: The Hubble Constant Tension

The current cosmological probes have provided a fantastic confirmation of the standard $Λ$ Cold Dark Matter cosmological model, that has been constrained with unprecedented accuracy. However, with the increase of the experimental sensitivity a few statistically significant tensions between different independent cosmological datasets emerged. While these tensions can be in portion the result of systematic errors, the persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the need for new physics. In this Letter of Interest we will focus on the $4.4σ$ tension between the Planck estimate of the Hubble constant $H_0$ and the SH0ES collaboration measurements. After showing the $H_0$ evaluations made from different teams using different methods and geometric calibrations, we will list a few interesting new physics models that could solve this tension and discuss how the next decade experiments will be crucial.

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arXiv2020

Cosmology Intertwined I: Perspectives for the Next Decade

The standard $Λ$ Cold Dark Matter cosmological model provides an amazing description of a wide range of astrophysical and astronomical data. However, there are a few big open questions, that make the standard model look like a first-order approximation to a more realistic scenario that still needs to be fully understood. In this Letter of Interest we will list a few important goals that need to be addressed in the next decade, also taking into account the current discordances present between the different cosmological probes, as the Hubble constant $H_0$ value, the $σ_8 - S_8$ tension, and the anomalies present in the Planck results. Finally, we will give an overview of upgraded experiments and next-generation space-missions and facilities on Earth, that will be of crucial importance to address all these questions.

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arXiv2020

Cosmology Intertwined IV: The Age of the Universe and its Curvature

A precise measurement of the curvature of the Universe is of primeval importance for cosmology since it could not only confirm the paradigm of primordial inflation but also help in discriminating between different early Universe scenarios. The recent observations, while broadly consistent with a spatially flat standard $Λ$ Cold Dark Matter ($Λ$CDM) model, are showing tensions that still allow (and, in some cases, even suggest) a few percent deviations from a flat universe. In particular, the Planck Cosmic Microwave Background power spectra, assuming the nominal likelihood, prefer a closed universe at more than 99\% confidence level. While new physics could be in action, this anomaly may be the result of an unresolved systematic error or just a statistical fluctuation. However, since a positive curvature allows a larger age of the Universe, an accurate determination of the age of the oldest objects provides a smoking gun in confirming or falsifying the current flat $Λ$CDM model.

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arXiv2020

A new method to build the (inverse) distance ladder

The cosmic distance ladder is the succession of techniques by which it is possible to determine distances to astronomical objects. Here, we present a new method to build the cosmic distance ladder, going from local astrophysical measurements to the CMB. Instead of relying on high-redshift cosmography in order to model the luminosity-distance relation and calibrate supernovae with BAO, we exploit directly the distance-duality relation $d_L = (1+z)^2 d_A$---valid if photon number is conserved and gravity is described by a metric theory. The advantage is that the results will not depend on the parametrization of the luminosity-distance relation at $z>0.15$: no model is adopted in order to calibrate BAO with supernovae. This method yields local measurements of the Hubble constant and deceleration parameter. Furthermore, it can directly assess the impact of BAO observations on the strong 4--5$σ$ tension between local and global $H_0$. Using the latest supernova, BAO and CMB observations, we found a consistently low value of $q_0$ and strong inconsistency between angular-only BAO constraints and anisotropic BAO measurements, which are, or not, in agreement with CMB depending on the kind of analysis (see Table~$4$). We conclude that, in order to understand the reasons behind the $H_0$ crisis, a first step should be clarifying the tension between angular and perpendicular anisotropic BAO as this will help understanding if new physics is required at the pre-recombination epoch or/and during the dark energy era.

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arXiv2019

Local determination of the Hubble constant and the deceleration parameter

The determination of the Hubble constant $H_0$ from the Cosmic Microwave Background by the Planck Collaboration [Aghanim et al. 2018] is in tension at $4.2σ$ with respect to the local determination of $H_0$ by the SH0ES collaboration [Reid et al. 2019]. Here, we improve upon the local determination, which fixes the deceleration parameter to the standard $Λ$CDM model value of $q_0=-0.55$, that is, uses information from observations beyond the local universe. First, we derive the effective calibration prior on the absolute magnitude $M_B$ of Supernovae Ia, which can be used in cosmological analyses in order to avoid the double counting of low-redshift supernovae. We find $M_B = -19.2334 \pm 0.0404$ mag. Then, we use the above $M_B$ prior in order to obtain a determination of the local $H_0$ which only uses local observations and only assumes the cosmological principle, that is, large-scale homogeneity and isotropy. This is achieved by adopting an uninformative flat prior for $q_0$ in the cosmographic expansion of the luminosity distance. We use the latest Pantheon sample and find $H_0= 75.35 \pm 1.68 \text{ km s}^{-1} {\rm Mpc}^{-1}$, which features a 2.2% uncertainty, close to the 1.9% error obtained by the SH0ES Collaboration. Our determination is at the higher tension of $4.5σ$ with the latest results from the Planck Collaboration that assume the $Λ$CDM model. Furthermore, we also constrain the deceleration parameter to $q_0= -1.08 \pm 0.29$, which disagrees with Planck at the $1.9σ$ level. These estimations only use supernovae in the redshift range $0.023\le z\le 0.15$.

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