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Bhattacharya, Suman, Katrin Heitmann, Martin White, Zarija Lukić, Christian Wagner i Salman Habib. "MASS FUNCTION PREDICTIONS BEYOND ΛCDM". Astrophysical Journal 732, nr 2 (26.04.2011): 122. http://dx.doi.org/10.1088/0004-637x/732/2/122.
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Das, Sudeep, Roland de Putter, Eric V. Linder i Reiko Nakajima. "Weak lensing cosmology beyond ΛCDM". Journal of Cosmology and Astroparticle Physics 2012, nr 11 (6.11.2012): 011. http://dx.doi.org/10.1088/1475-7516/2012/11/011.
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Rizzo, Luca A., Francisco Villaescusa-Navarro, Pierluigi Monaco, Emiliano Munari, Stefano Borgani, Emanuele Castorina i Emiliano Sefusatti. "Simulating cosmologies beyond ΛCDM with PINOCCHIO". Journal of Cosmology and Astroparticle Physics 2017, nr 01 (4.01.2017): 008. http://dx.doi.org/10.1088/1475-7516/2017/01/008.
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Tröster, Tilman, Marika Asgari, Chris Blake, Matteo Cataneo, Catherine Heymans, Hendrik Hildebrandt, Benjamin Joachimi i in. "KiDS-1000 Cosmology: Constraints beyond flat ΛCDM". Astronomy & Astrophysics 649 (maj 2021): A88. http://dx.doi.org/10.1051/0004-6361/202039805.
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We present constraints on extensions to the standard cosmological model of a spatially flat Universe governed by general relativity, a cosmological constant (Λ), and cold dark matter (CDM) by varying the spatial curvature ΩK, the sum of the neutrino masses ∑mν, the dark energy equation of state parameter w, and the Hu-Sawicki f(R) gravity fR0 parameter. With the combined 3 × 2 pt measurements of cosmic shear from the Kilo-Degree Survey (KiDS-1000), galaxy clustering from the Baryon Oscillation Spectroscopic Survey (BOSS), and galaxy-galaxy lensing from the overlap between KiDS-1000, BOSS, and the spectroscopic 2-degree Field Lensing Survey, we find results that are fully consistent with a flat ΛCDM model with ΩK = 0.011−0.057+0.054, ∑mν < 1.76 eV (95% CL), and w = −0.99−0.13+0.11. The fR0 parameter is unconstrained in our fully non-linear f(R) cosmic shear analysis. Considering three different model selection criteria, we find no clear preference for either the fiducial flat ΛCDM model or any of the considered extensions. In addition to extensions to the flat ΛCDM parameter space, we also explore restrictions to common subsets of the flat ΛCDM parameter space by fixing the amplitude of the primordial power spectrum to the Planck best-fit value, as well as adding external data from supernovae and lensing of the cosmic microwave background (CMB). Neither the beyond-ΛCDM models nor the imposed restrictions explored in this analysis are able to resolve the ∼3σ tension in S8 between the 3 × 2 pt constraints and the Planck temperature and polarisation data, with the exception of wCDM, where the S8 tension is resolved. The tension in the wCDM case persists, however, when considering the joint S8 − w parameter space. The joint flat ΛCDM CMB lensing and 3 × 2 pt analysis is found to yield tight constraints on Ωm = 0.307−0.013+0.008, σ8 = 0.769−0.010+0.022, and S8 = 0.779−0.013+0.013.
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Giblin, Benjamin, Matteo Cataneo, Ben Moews i Catherine Heymans. "On the road to per cent accuracy – II. Calibration of the non-linear matter power spectrum for arbitrary cosmologies". Monthly Notices of the Royal Astronomical Society 490, nr 4 (21.09.2019): 4826–40. http://dx.doi.org/10.1093/mnras/stz2659.
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ABSTRACT We introduce an emulator approach to predict the non-linear matter power spectrum for broad classes of beyond-ΛCDM cosmologies, using only a suite of ΛCDM N-body simulations. By including a range of suitably modified initial conditions in the simulations, and rescaling the resulting emulator predictions with analytical ‘halo model reactions’, accurate non-linear matter power spectra for general extensions to the standard ΛCDM model can be calculated. We optimize the emulator design by substituting the simulation suite with non-linear predictions from the standard halofit tool. We review the performance of the emulator for artificially generated departures from the standard cosmology as well as for theoretically motivated models, such as f(R) gravity and massive neutrinos. For the majority of cosmologies we have tested, the emulator can reproduce the matter power spectrum with errors ${\lesssim}1{{\ \rm per\ cent}}$ deep into the highly non-linear regime. This work demonstrates that with a well-designed suite of ΛCDM simulations, extensions to the standard cosmological model can be tested in the non-linear regime without any reliance on expensive beyond-ΛCDM simulations.
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Sakr, Z. "A trium test on beyond ΛCDM triggering parameters". Journal of Cosmology and Astroparticle Physics 2023, nr 08 (1.08.2023): 080. http://dx.doi.org/10.1088/1475-7516/2023/08/080.
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Abstract We performed a Bayesian study on three beyond ΛCDM phenomenological triggering parameters, the growth index γ, the dark energy equation of state parameter ω and the lensing deviation from the GR prediction parameter Σ, using the latest cosmological geometric, growth and lensing probes, all in a consistent implementation within the modified gravity cosmological solver code MGCLASS. We find, when we combined all our probes, i.e. the cosmic microwave background (CMB), the baryonic acoustic oscilation (BAO), the growth measurements fσ 8 and the 3×2pt joint analysis of weak lensing and galaxy clustering in photometric redshift surveys, assuming flat space, constraints compatible with general relativity and ΛCDM with ω = -1.025 ± 0.045, and Σ = 0.992 ± 0.022 at the 68% level, while γ = 0.633±0.044 is still within ∼ 2σ from the ΛCDM value of γ ∼ 0.55, and that when Σ is considered as constant; while γℓ = -0.025 ±0.045 when the lensing parameter is parameterised as function of a lensing index, introduced for the first time in this work, as Σ(z) = Ωm(z)γℓ .
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Li, En-Kun, Hongchao Zhang, Minghui Du, Zhi-Huan Zhou i Lixin Xu. "Probing the Neutrino Mass Hierarchy beyond ΛCDM Model". Journal of Cosmology and Astroparticle Physics 2018, nr 08 (28.08.2018): 042. http://dx.doi.org/10.1088/1475-7516/2018/08/042.
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Bull, Philip, Yashar Akrami, Julian Adamek, Tessa Baker, Emilio Bellini, Jose Beltrán Jiménez, Eloisa Bentivegna i in. "Beyond ΛCDM: Problems, solutions, and the road ahead". Physics of the Dark Universe 12 (czerwiec 2016): 56–99. http://dx.doi.org/10.1016/j.dark.2016.02.001.
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Villa, Eleonora, Enea Di Dio i Francesca Lepori. "Lensing convergence in galaxy clustering in ΛCDM and beyond". Journal of Cosmology and Astroparticle Physics 2018, nr 04 (9.04.2018): 033. http://dx.doi.org/10.1088/1475-7516/2018/04/033.
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L’Huillier, Benjamin, Arman Shafieloo, Eric V. Linder i Alex G. Kim. "Model independent expansion history from supernovae: Cosmology versus systematics". Monthly Notices of the Royal Astronomical Society 485, nr 2 (2.03.2019): 2783–90. http://dx.doi.org/10.1093/mnras/stz589.
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Abstract We examine the Pantheon supernovae distance data compilation in a model independent analysis to test the validity of cosmic history reconstructions beyond the concordance ΛCDM cosmology. Strong deviations are allowed by the data at z ≳ 1 in the reconstructed Hubble parameter, Om diagnostic, and dark energy equation of state. We explore three interpretations: 1) possibility of the true cosmology being far from ΛCDM, 2) supernovae property evolution, and 3) survey selection effects. The strong (and theoretically problematic) deviations at z ≳ 1 vanish and good consistency with ΛCDM is found with a simple Malmquist-like linear correction. The adjusted data is robust against the model independent iterative smoothing reconstruction. However, we caution that while by eye the original deviation from ΛCDM is striking, χ2 tests do not show the extra linear correction parameter is statistically significant, and a model-independent Gaussian Process regression does not find significant evidence for the need for correction at high-redshifts.
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Paoletti, Daniela, Dhiraj Kumar Hazra, Fabio Finelli i George F. Smoot. "Extended reionization in models beyond ΛCDM with Planck 2018 data". Journal of Cosmology and Astroparticle Physics 2020, nr 09 (1.09.2020): 005. http://dx.doi.org/10.1088/1475-7516/2020/09/005.
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Enqvist, Kari, Till Sawala i Tomo Takahashi. "Structure formation with two periods of inflation: beyond PLaIn ΛCDM". Journal of Cosmology and Astroparticle Physics 2020, nr 10 (27.10.2020): 053. http://dx.doi.org/10.1088/1475-7516/2020/10/053.
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Doux, C., E. Baxter, P. Lemos, C. Chang, A. Alarcon, A. Amon, A. Campos i in. "Dark energy survey internal consistency tests of the joint cosmological probes analysis with posterior predictive distributions". Monthly Notices of the Royal Astronomical Society 503, nr 2 (24.02.2021): 2688–705. http://dx.doi.org/10.1093/mnras/stab526.
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ABSTRACT Beyond ΛCDM, physics or systematic errors may cause subsets of a cosmological data set to appear inconsistent when analysed assuming ΛCDM. We present an application of internal consistency tests to measurements from the Dark Energy Survey Year 1 (DES Y1) joint probes analysis. Our analysis relies on computing the posterior predictive distribution (PPD) for these data under the assumption of ΛCDM. We find that the DES Y1 data have an acceptable goodness of fit to ΛCDM, with a probability of finding a worse fit by random chance of p = 0.046. Using numerical PPD tests, supplemented by graphical checks, we show that most of the data vector appears completely consistent with expectations, although we observe a small tension between large- and small-scale measurements. A small part (roughly 1.5 per cent) of the data vector shows an unusually large departure from expectations; excluding this part of the data has negligible impact on cosmological constraints, but does significantly improve the p-value to 0.10. The methodology developed here will be applied to test the consistency of DES Year 3 joint probes data sets.
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Sun, Chen, Manuel A. Buen-Abad i JiJi Fan. "Probing New physics with high-redshift quasars: axions and non-standard cosmology". Journal of Cosmology and Astroparticle Physics 2024, nr 06 (1.06.2024): 037. http://dx.doi.org/10.1088/1475-7516/2024/06/037.
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Abstract The Hubble diagram of quasars, as candidates to “standardizable” candles, has been used to measure the expansion history of the Universe at late times, up to very high redshifts (z ∼ 7). It has been shown that this history, as inferred from the quasar dataset, deviates at ≳ 3σ level from the concordance (ΛCDM) cosmology model preferred by the cosmic microwave background (CMB) and other datasets. In this article, we investigate whether new physics beyond ΛCDM (BΛCDM) or beyond the Standard Model (BSM) could make the quasar data consistent with the concordance model. We first show that an effective redshift-dependent relation between the quasar UV and X-ray luminosities, complementing previous phenomenological work in the literature, can potentially remedy the discrepancy. Such a redshift dependence can be realized in a BSM model with axion-photon conversion in the intergalactic medium (IGM), although the preferred parameter space is in tension with various other astrophysical constraints on axions, at a level depending on the specific assumptions made regarding the IGM magnetic field. We briefly discuss a variation of the axion model that could evade these astrophysical constraints. On the other hand, we show that models beyond ΛCDM such as one with a varying dark energy equation of state (wCDM) or the phenomenological cosmographic model with a polynomial expansion of the luminosity distance, cannot alleviate the tension. The code for our analysis, based on emcee [1] and corner.py [2], is publicly available at github.com/ChenSun-Phys/high_z_candles.
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Pedersen, Christian, Andreu Font-Ribera, Keir K. Rogers, Patrick McDonald, Hiranya V. Peiris, Andrew Pontzen i Anže Slosar. "An emulator for the Lyman-α forest in beyond-ΛCDM cosmologies". Journal of Cosmology and Astroparticle Physics 2021, nr 05 (1.05.2021): 033. http://dx.doi.org/10.1088/1475-7516/2021/05/033.
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Brando, Guilherme, Bartolomeo Fiorini, Kazuya Koyama i Hans A. Winther. "Enabling matter power spectrum emulation in beyond-ΛCDM cosmologies with COLA". Journal of Cosmology and Astroparticle Physics 2022, nr 09 (1.09.2022): 051. http://dx.doi.org/10.1088/1475-7516/2022/09/051.
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Abstract We compare and validate COLA (COmoving Lagrangian Acceleration) simulations against existing emulators in the literature, namely Bacco and Euclid Emulator 2. Our analysis focuses on the non-linear response function, i.e., the ratio between the non-linear dark matter power spectrum in a given cosmology with respect to a pre-defined reference cosmology, which is chosen to be the Euclid Emulator 2 reference cosmology in this paper. We vary three cosmological parameters, the total matter density, the amplitude of the primordial scalar perturbations and the spectral index. By comparing the COLA non-linear response function with those computed from each emulator in the redshift range 0 ≤ z ≤ 3, we find that the COLA method is in excellent agreement with the two emulators for scales up to k ∼ 1 h/Mpc as long as the deviations of the matter power spectrum from the reference cosmology are not too large. We validate the implementation of massive neutrinos in our COLA simulations by varying the sum of neutrino masses to three different values, 0.0 eV, 0.058 eV and 0.15 eV. We show that all three non-linear prescriptions used in this work agree at the 1% level at k ≤ 1 h/Mpc. We then introduce the Effective Field Theory of Dark Energy in our COLA simulations using the N-body gauge method. We consider two different modified gravity models in which the growth of structure is enhanced or suppressed at small scales, and show that the response function with respect to the change of modified gravity parameters depends weakly on cosmological parameters in these models.
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Paradiso, S., G. McGee i W. J. Percival. "Evaluating extensions to LCDM: an application of Bayesian model averaging and selection". Journal of Cosmology and Astroparticle Physics 2024, nr 10 (1.10.2024): 021. http://dx.doi.org/10.1088/1475-7516/2024/10/021.
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Abstract We present a powerful and innovative statistical framework to address key cosmological questions about the universe's fundamental properties, performing Bayesian model averaging (BMA) and model selection. Utilizing this framework, we systematically explore extensions beyond the standard ΛCDM model, considering a varying curvature density parameter ΩK, a spectral index ns = 1 and a varying n run, a constant dark energy equation of state (EOS) w 0CDM and a time-dependent one w 0 w aCDM. We also assess cosmological data against a varying effective number of neutrino species N eff. Our analysis incorporates data from various combinations of cosmic microwave background (CMB) data from the latest Planck PR4 analysis, CMB lensing from Planck 2018, baryonic acoustic oscillations (BAO), and the Bicep-KECK 2018 results. We reinforce the standard ΛCDM model statistical preference when combining CMB data with CMB lensing, BAO, and Bicep-KECK 2018 data against the K-ΛCDM model and dns /d ln k-ΛCDM with a probability > 80%. When evaluating the dark energy EOS, we find that this dataset does not exhibit a strong preference between the standard ΛCDM model and the constant dark energy EOS model w 0CDM, with a model posterior probability distribution of approximately ≈ 40%:60% in favour of w 0CDM, while the time-varying dark energy EOS model only holds below 1% probability. We find a similar result also when considering the N eff-ΛCDM model, with a split probability almost 50%-50% from both our datasets. Overall, our application of BMA reveals that including model uncertainty in these cases does not significantly impact the Hubble tension, showcasing BMA's robustness and utility in cosmological model evaluation.
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Hu, Jian-Ping, i Fa-Yin Wang. "Hubble Tension: The Evidence of New Physics". Universe 9, nr 2 (10.02.2023): 94. http://dx.doi.org/10.3390/universe9020094.
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The ΛCDM model provides a good fit to most astronomical observations but harbors large areas of phenomenology and ignorance. With the improvements in the precision and number of observations, discrepancies between key cosmological parameters of this model have emerged. Among them, the most notable tension is the 4σ to 6σ deviation between the Hubble constant (H0) estimations measured by the local distance ladder and the cosmic microwave background (CMB) measurement. In this review, we revisit the H0 tension based on the latest research and sort out evidence from solutions to this tension that might imply new physics beyond the ΛCDM model. The evidence leans more towards modifying the late-time universe.
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Cataneo, M., J. D. Emberson, D. Inman, J. Harnois-Déraps i C. Heymans. "On the road to per cent accuracy – III. Non-linear reaction of the matter power spectrum to massive neutrinos". Monthly Notices of the Royal Astronomical Society 491, nr 3 (15.11.2019): 3101–7. http://dx.doi.org/10.1093/mnras/stz3189.
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ABSTRACT We analytically model the non-linear effects induced by massive neutrinos on the total matter power spectrum using the halo model reaction framework of Cataneo et al. In this approach, the halo model is used to determine the relative change to the matter power spectrum caused by new physics beyond the concordance cosmology. Using standard fitting functions for the halo abundance and the halo mass–concentration relation, the total matter power spectrum in the presence of massive neutrinos is predicted to per cent-level accuracy, out to $k=10 \,{ h}\,{\rm Mpc}^{-1}$. We find that refining the prescriptions for the halo properties using N-body simulations improves the recovered accuracy to better than 1 per cent. This paper serves as another demonstration for how the halo model reaction framework, in combination with a single suite of standard Λ cold dark matter (ΛCDM) simulations, can recover per cent-level accurate predictions for beyond ΛCDM matter power spectra, well into the non-linear regime.
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Hu, J. P., X. D. Jia, J. Hu i F. Y. Wang. "Hints of New Physics for the Hubble Tension: Violation of Cosmological Principle". Astrophysical Journal Letters 975, nr 2 (1.11.2024): L36. http://dx.doi.org/10.3847/2041-8213/ad85cf.
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Abstract Discrepancy between the measurements of Hubble constant H 0 from the cosmic microwave background and the local distance ladder is the most serious challenge to the standard ΛCDM model. Recent research has pointed out that it might be related with the violation of cosmological principle. Here, we investigate the impact of dipole–monopole correction on the constraints of H 0 utilizing the dipole-fitting method based on the ΛCDM model and cosmography method. Our results show that the dipole–monopole correction can reduce the constraints of H 0 from a larger value consistent with SH0ES results to a smaller value consistent with Planck results. This finding can effectively alleviate the Hubble tension. Through making redshift tomography and model-independent analyses, we confirm that our findings are independent of the redshift and cosmological model. In addition, the theoretical prediction of H(z)/(1 + z) reconstructed by the constraints of the ΛCDM model with the dipole correction is in agreement with baryon acoustic oscillation (BAO) measurements, including five Dark Energy Spectroscopic Instrument BAOs within the 1σ range except a data point at z = 0.51. Our research suggests that the Hubble tension originates from new physics beyond the standard ΛCDM model, which might lead to a violation of the cosmological principle.
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Petreca, A. Turmina, M. Benetti i S. Capozziello. "Beyond ΛCDM with f(z)CDM: Criticalities and solutions of Padé Cosmography". Physics of the Dark Universe 44 (maj 2024): 101453. http://dx.doi.org/10.1016/j.dark.2024.101453.
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Kumar, Suresh, Rafael C. Nunes i Santosh Kumar Yadav. "Testing the warmness of dark matter". Monthly Notices of the Royal Astronomical Society 490, nr 1 (27.09.2019): 1406–14. http://dx.doi.org/10.1093/mnras/stz2676.
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ABSTRACT Dark matter (DM) as a pressureless perfect fluid provides a good fit of the standard Λ cold dark matter (ΛCDM) model to the astrophysical and cosmological data. In this paper, we investigate two extended properties of DM: a possible time dependence of the equation of state of DM via Chevallier–Polarski–Linder parametrization, wdm = wdm0 + wdm1(1 − a), and the constant non-null sound speed $\hat{c}^2_{\rm s,dm}$. We analyse these DM properties on top of the base ΛCDM model by using the data from Planck cosmic microwave background (CMB) temperature and polarization anisotropy, baryonic acoustic oscillations (BAOs), and the local value of the Hubble constant from the Hubble Space Telescope (HST). We find new and robust constraints on the extended free parameters of DM. The most tight constraints are imposed by CMB+BAO data, where the three parameters wdm0, wdm1, and $\hat{c}^2_{\rm s,dm}$ are, respectively, constrained to be less than 1.43 × 10−3, 1.44 × 10−3, and 1.79 × 10−6 at 95 per cent CL. All the extended parameters of DM show consistency with zero at 95 per cent CL, indicating no evidence beyond the CDM paradigm. We notice that the extended properties of DM significantly affect several parameters of the base ΛCDM model. In particular, in all the analyses performed here, we find significantly larger mean values of H0 and lower mean values of σ8 in comparison to the base ΛCDM model. Thus, the well-known H0 and σ8 tensions might be reconciled in the presence of extended DM parameters within the ΛCDM framework. Also, we estimate the warmness of DM particles as well as its mass scale, and find a lower bound: ∼500 eV from our analyses.
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Bose, Benjamin, Matteo Cataneo, Tilman Tröster, Qianli Xia, Catherine Heymans i Lucas Lombriser. "On the road to per cent accuracy IV: ReACT – computing the non-linear power spectrum beyond ΛCDM". Monthly Notices of the Royal Astronomical Society 498, nr 4 (7.09.2020): 4650–62. http://dx.doi.org/10.1093/mnras/staa2696.
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ABSTRACT To effectively exploit large-scale structure surveys, we depend on accurate and reliable predictions of non-linear cosmological structure formation. Tools for efficient and comprehensive computational modelling are therefore essential to perform cosmological parameter inference analyses. We present the public software package ReACT, demonstrating its capability for the fast and accurate calculation of non-linear power spectra from non-standard physics. We showcase ReACT through a series of analyses on the DGP and f(R) gravity models, adopting LSST-like cosmic shear power spectra. Accurate non-linear modelling with ReACT has the potential to more than double LSST’s constraining power on the f(R) parameter, in contrast to an analysis that is limited to the quasi-linear regime. We find that ReACT is sufficiently robust for the inference of consistent constraints on theories beyond ΛCDM for current and ongoing surveys. With further improvement, particularly in terms of the accuracy of the non-linear ΛCDM power spectrum, ReACT can, in principle, meet the accuracy requirements for future surveys such as Euclid and LSST.
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Lee, Bum-Hoon, Wonwoo Lee, Eoin Ó Colgáin, M. M. Sheikh-Jabbari i Somyadip Thakur. "Is local H 0 at odds with dark energy EFT?" Journal of Cosmology and Astroparticle Physics 2022, nr 04 (1.04.2022): 004. http://dx.doi.org/10.1088/1475-7516/2022/04/004.
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Abstract Local H_0 determinations currently fall in a window between H 0 ∼ 70 km/s/Mpc (TRGB) and H 0 ∼ 76 km/s/Mpc (Tully-Fisher). In contrast, BAO data calibrated in an early ΛCDM universe are largely consistent with Planck-ΛCDM, H 0 ∼ 67.5 km/s/Mpc. Employing a generic two parameter family of evolving equations of state (EoS) for dark energy (DE) w DE(z) and mock BAO data, we demonstrate that if i) w DE(z = 0) < -1 and ii) integrated DE density less than ΛCDM, then H 0 increases. EoS that violate these conditions at best lead to modest H 0 increases within 1σ. Tellingly, Quintessence and K-essence satisfy neither condition, whereas coupled Quintessence can only satisfy ii). Beyond these seminal DE Effective Field Theories (EFTs), we turn to explicit examples. Working model agnostically in an expansion in powers of redshift z, we show that Brans-Dicke/f(R) and Kinetic Gravity Braiding models within the Horndeski class can lead to marginal and modest increases in H 0, respectively. We confirm that as far as increasing H 0 is concerned, no DE EFT model can outperform the phenomenological two parameter family of the DE models. Evidently, the late universe may no longer be large enough to accommodate H 0, BAO and DE described by EFT.
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Alexeyev, Stanislav, i Vyacheslav Prokopov. "Extended Gravity Constraints at Different Scales". Universe 8, nr 5 (15.05.2022): 283. http://dx.doi.org/10.3390/universe8050283.
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We review a set of the possible ways to constrain extended gravity models at Galaxy clusters scales (the regime of dark energy explanations and comparison with ΛCDM), for black hole shadows, gravitational wave astronomy, binary pulsars, the Solar system and a Large Hadron Collider (consequences for high-energy physics at TeV scale). The key idea is that modern experimental and observational precise data provide us with the chance to go beyond general relativity.
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Garrison, Lehman H., Michael Joyce i Daniel J. Eisenstein. "Good and proper: self-similarity of N-body simulations with proper force softening". Monthly Notices of the Royal Astronomical Society 504, nr 3 (22.04.2021): 3550–60. http://dx.doi.org/10.1093/mnras/stab1096.
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ABSTRACT Analysis of self-similarity in scale-free N-body simulations reveals the spatial and temporal scales for which statistics measured in cosmological simulations are converged to the physical continuum limit. We examine how the range of scales in which the two-point correlation function is converged depends on the force softening length and whether it is held constant in comoving or proper coordinates. We find that a proper softening that reaches roughly 1/30th of the inter-particle spacing by the end of the simulation resolves the same spatial and temporal scales as a comoving softening of the same length while using a third fewer time-steps, for a range of scale factors typical to Lambda cold dark matter (ΛCDM) simulations. We additionally infer an inherent resolution limit, set by the particle mass and scaling as a−1/2, beyond which reducing the softening does not improve the resolution. We postulate a mapping of these results with spectral index n = −2 to ΛCDM simulations.
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Steinhardt, Charles L., Albert Sneppen, Thorbjørn Clausen, Harley Katz, Martin P. Rey i Jonas Stahlschmidt. "The Highest-redshift Balmer Breaks as a Test of ΛCDM". Astrophysical Journal 967, nr 2 (30.05.2024): 172. http://dx.doi.org/10.3847/1538-4357/ad3afb.
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Abstract Recent studies have reported tension between the presence of luminous, high-redshift galaxies and the halo mass functions predicted by standard cosmology. Here, an improved test is proposed using the presence of high-redshift Balmer breaks to probe the formation of early 104–105 M ⊙ baryonic minihalos. Unlike previous tests, this does not depend upon the mass-to-light ratio and has only a slight dependence upon the metallicity, stellar initial mass function, and star formation history, which are all weakly constrained at high redshift. We show that the strongest Balmer breaks allowed at z = 9 using the simplest ΛCDM cosmological model would allow a D 4000 as high as 1.26 under idealized circumstances and D 4000 ≤ 1.14 including realistic feedback models. Since current photometric template fitting to JWST sources infers the existence of stronger Balmer breaks out to z ≳ 11, upcoming spectroscopic follow-up will either demonstrate those templates are invalid at high redshift or imply new physics beyond “vanilla” ΛCDM.
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Gough, Alex, i Cora Uhlemann. "One-Point Statistics Matter in Extended Cosmologies". Universe 8, nr 1 (17.01.2022): 55. http://dx.doi.org/10.3390/universe8010055.
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The late universe contains a wealth of information about fundamental physics and gravity, wrapped up in non-Gaussian fields. To make use of as much information as possible, it is necessary to go beyond two-point statistics. Rather than going to higher-order N-point correlation functions, we demonstrate that the probability distribution function (PDF) of spheres in the matter field (a one-point function) already contains a significant amount of this non-Gaussian information. The matter PDF dissects different density environments which are lumped together in two-point statistics, making it particularly useful for probing modifications of gravity or expansion history. Our approach in Cataneo et al. 2021 extends the success of Large Deviation Theory for predicting the matter PDF in ΛCDM in these “extended” cosmologies. A Fisher forecast demonstrates the information content in the matter PDF via constraints for a Euclid-like survey volume combining the 3D matter PDF with the 3D matter power spectrum. Adding the matter PDF halves the uncertainties on parameters in an evolving dark energy model, relative to the power spectrum alone. Additionally, the matter PDF contains enough non-linear information to substantially increase the detection significance of departures from General Relativity, with improvements up to six times the power spectrum alone. This analysis demonstrates that the matter PDF is a promising non-Gaussian statistic for extracting cosmological information, particularly for beyond ΛCDM models.
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Moradinezhad Dizgah, Azadeh, Emilio Bellini i Garrett K. Keating. "Probing Dark Energy and Modifications of Gravity with Ground-based millimeter-wavelength Line Intensity Mapping". Astrophysical Journal 965, nr 1 (1.04.2024): 19. http://dx.doi.org/10.3847/1538-4357/ad2078.
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Abstract Line intensity mapping (LIM) can provide a powerful means to constrain the theory of gravity and the nature of dark energy at low and high redshifts by mapping the large-scale structure over many redshift epochs. In this paper, we investigate the potential of the next generation ground-based millimeter-wavelength LIM surveys in constraining several models beyond ΛCDM, involving either a dynamic dark energy component or modifications of the theory of gravity. Limiting ourselves to two-point clustering statistics, we consider the measurements of auto-spectra of several CO rotational lines (from J = 2−1 to J = 6−5) and the [C ii] fine structure line in the redshift range of 0.25 < z < 12. We consider different models beyond ΛCDM, each one with different signatures and peculiarities. Among them, we focus on Jordan–Brans–Dicke and axion-driven early dark energy models as examples of well-studied scalar-tensor theories acting at late and early times, respectively. Additionally, we consider three phenomenological models based on an effective description of gravity at cosmological scales. We show that LIM surveys deployable within a decade (with ∼108 spectrometer hours) have the potential to improve upon the current bounds on all considered models significantly. The level of improvements range from a factor of a few to an order of magnitude.
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Berti, M., M. Spinelli, B. S. Haridasu, M. Viel i A. Silvestri. "Constraining beyond ΛCDM models with 21cm intensity mapping forecasted observations combined with latest CMB data". Journal of Cosmology and Astroparticle Physics 2022, nr 01 (1.01.2022): 018. http://dx.doi.org/10.1088/1475-7516/2022/01/018.
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Abstract We explore constraints on dark energy and modified gravity with forecasted 21cm intensity mapping measurements using the Effective Field Theory approach. We construct a realistic mock data set forecasting a low redshift 21cm signal power spectrum P 21(z,k) measurement from the MeerKAT radio-telescope. We compute constraints on cosmological and model parameters through Monte-Carlo Markov-Chain techniques, testing both the constraining power of P 21(k) alone and its effect when combined with the latest Planck 2018 CMB data. We complement our analysis by testing the effects of tomography from an ideal mock data set of observations in multiple redshift bins. We conduct our analysis numerically with the codes EFTCAMB/EFTCosmoMC, which we extend by implementing a likelihood module fully integrated with the original codes. We find that adding P 21(k) to CMB data provides significantly tighter constraints on Ωc h 2 and H 0, with a reduction of the error with respect to Planck results at the level of more than 60%. For the parameters describing beyond ΛCDM theories, we observe a reduction in the error with respect to the Planck constraints at the level of ≲ 10%. The improvement increases up to ∼ 35% when we constrain the parameters using ideal, tomographic mock observations. We conclude that the power spectrum of the 21cm signal is sensitive to variations of the parameters describing the examined beyond ΛCDM models and, thus, P 21(k) observations could help to constrain dark energy. The constraining power on such theories is improved significantly by tomography.
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Huang, Lu, Zhi-Qi Huang, Zhuo-Yang Li i Huan Zhou. "A more accurate Parameterization based on cosmic Age (MAPAge)". Research in Astronomy and Astrophysics 21, nr 11 (1.12.2021): 277. http://dx.doi.org/10.1088/1674-4527/21/11/277.
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Abstract Recently, several statistically significant tensions between different cosmological datasets have raised doubts about the standard Lambda cold dark matter (ΛCDM) model. A recent letter (Huang 2020) suggests to use “Parameterization based on cosmic Age” (PAge) to approximate a broad class of beyond-ΛCDM models, with a typical accuracy ∼1% in angular diameter distances at z ≲ 10. In this work, we extend PAge to a More Accurate Parameterization based on cosmic Age (MAPAge) by adding a new degree of freedom η 2. The parameter η 2 describes the difference between physically motivated models and their phenomenological PAge approximations. The accuracy of MAPAge, typically of order 10−3 in angular diameter distances at z ≲ 10, is significantly better than PAge. We compare PAge and MAPAge with current observational data and forecast data. The conjecture in Huang (2020), that PAge approximation is sufficiently good for current observations, is quantitatively confirmed in this work. We also show that the extension from PAge to MAPAge is important for future observations, which typically require sub-percent accuracy in theoretical predictions.
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Capozziello, Salvatore, Giuseppe Sarracino i Giulia De Somma. "A Critical Discussion on the H0 Tension". Universe 10, nr 3 (13.03.2024): 140. http://dx.doi.org/10.3390/universe10030140.
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A critical discussion on the H0 Hubble constant tension is presented by considering both early and late-type observations. From recent precise measurements, discrepancies emerge when comparing results for some cosmological quantities obtained at different redshifts. We highlight the most relevant measurements of H0 and propose potential ideas to solve its tension. These solutions concern the exploration of new physics beyond the ΛCDM model or the evaluation of H0 by other methods. In particular, we focus on the role of the look-back time.
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Balaudo, Anna, Alice Garoffolo, Matteo Martinelli, Suvodip Mukherjee i Alessandra Silvestri. "Prospects of testing late-time cosmology with weak lensing of gravitational waves and galaxy surveys". Journal of Cosmology and Astroparticle Physics 2023, nr 06 (1.06.2023): 050. http://dx.doi.org/10.1088/1475-7516/2023/06/050.
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Abstract We investigate the synergy of upcoming galaxy surveys and gravitational wave (GW) experiments in constraining late-time cosmology, examining the cross-correlations between the weak lensing of gravitational waves (GW-WL) and the galaxy fields. Without focusing on any specific GW detector configuration, we benchmark the requirements for the high precision measurement of cosmological parameters by considering several scenarios, varying the number of detected GW events and the uncertainty on the inference of the source luminosity distance and redshift. We focus on ΛCDM and scalar-tensor cosmologies, using the Effective Field Theory formalism as a unifying language. We find that, in some of the explored setups, GW-WL contributes to the galaxy signal by doubling the accuracy on non-ΛCDM parameters, allowing in the most favourable scenarios to reach even percent and sub-percent level bounds. Though the most extreme cases presented here are likely beyond the observational capabilities of currently planned individual GW detectors, we show nonetheless that — provided that enough statistics of events can be accumulated — GW-WL offers the potential to become a cosmological probe complementary to LSS surveys, particularly for those parameters that cannot be constrained by other GW probes such as standard sirens.
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Pawlowski, Marcel S., i Sangmo Tony Sohn. "On the Co-orbitation of Satellite Galaxies along the Great Plane of Andromeda: NGC 147, NGC 185, and Expectations from Cosmological Simulations". Astrophysical Journal 923, nr 1 (1.12.2021): 42. http://dx.doi.org/10.3847/1538-4357/ac2aa9.
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Abstract Half of the satellite galaxies of Andromeda form a narrow plane termed the Great Plane of Andromeda (GPoA), and their line-of-sight velocities display a correlation reminiscent of a rotating structure. Recently reported first proper-motion measurements for the on-plane satellites NGC 147 and NGC 185 indicate that they indeed co-orbit along the GPoA. This provides a novel opportunity to compare the M31 satellite system to ΛCDM expectations. We perform the first detailed comparison of the orbital alignment of two satellite galaxies beyond the Milky Way with several hydrodynamical and dark-matter-only cosmological simulations (Illustris TNG50, TNG100, ELVIS, and PhatELVIS) in the context of the Planes of Satellite Galaxies Problem. In line with previous works, we find that the spatial flattening and line-of-sight velocity correlation are already in substantial tension with ΛCDM, with none of the simulated analogs simultaneously reproducing both parameters. Almost none (3%–4%) of the simulated systems contain two satellites with orbital poles as well aligned with their satellite plane as indicated by the most likely proper motions of NGC 147 and NGC 185. However, within current measurement uncertainties, it is common (≈70%) that the two best-aligned satellites of simulated systems are consistent with the orbital alignment. Yet, the chance that any two simulated on-plane satellites have as well-aligned orbital poles as observed is low (≈4%). We conclude that confirmation of the tight orbital alignment for these two objects via improved measurements, or the discovery of similar alignments for additional GPoA members, holds the potential to further raise the tension with ΛCDM expectations.
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Sakr, Ziad, Stéphane Ilić, Alain Blanchard, Jamal Bittar i Wehbeh Farah. "Cluster counts: Calibration issue or new physics?" Astronomy & Astrophysics 620 (30.11.2018): A78. http://dx.doi.org/10.1051/0004-6361/201833151.
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In recent years, the amplitude of matter fluctuations inferred from low-redshift probes has been found to be generally lower than the value derived from cosmic microwave background (CMB) observations in the ΛCDM model. This tension has been exemplified by Sunyaev-Zel’dovich and X-ray cluster counts which, when using theirPlanckstandard cluster mass calibration, yield a value ofσ8, appreciably lower than estimations based on the latestPlanckCMB measurements. In this work we examine whether non-minimal neutrino masses can alleviate this tension substantially. We used the cluster X-ray temperature distribution function derived from a flux-limited sample of local X-ray clusters, combined withPlanckCMB measurements. These datasets were compared to ΛCDM predictions based on recent mass function, adapted to account for the effects of massive neutrinos. Treating the clusters mass calibration as a free parameter, we examined whether the data favours neutrino masses appreciably higher than the minimal 0.06 eV value. Using Markov chain Monte Carlo methods, we found no significant correlation between the mass calibration of clusters and the sum of neutrino masses, meaning that massive neutrinos do not noticeably alleviate the above-mentionedPlanckCMB–clusters tension. The addition of other datasets (baryon acoustic oscillations and Ly-α) reinforces those conclusions. As an alternative possible solution to the tension, we introduced a simple, phenomenological modification of gravity by letting the growth indexγvary as an additional free parameter. We find that the cluster mass calibration is robustly correlated with theγparameter, insensitively to the presence of massive neutrinos or/and additional data used. We conclude that the standardPlanckmass calibration of clusters, if consolidated, would represent evidence for new physics beyond ΛCDM with massive neutrinos.
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Camera, Stefano, i Hamsa Padmanabhan. "Beyond ΛCDM with H i intensity mapping: robustness of cosmological constraints in the presence of astrophysics". Monthly Notices of the Royal Astronomical Society 496, nr 4 (12.06.2020): 4115–26. http://dx.doi.org/10.1093/mnras/staa1663.
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ABSTRACT Mapping the unresolved intensity of the 21-cm emission of neutral hydrogen (H i) is now regarded as one the most promising tools for cosmological investigation in the coming decades. Here, we investigate, for the first time, extensions of the standard cosmological model, such as modified gravity and primordial non-Gaussianity, taking self-consistently into account. The present constraints on the astrophysics of H i clustering in the treatment of the brightness temperature fluctuations. To understand the boundaries within which results thus obtained can be considered reliable, we examine the robustness of cosmological parameter estimation performed via studies of 21-cm intensity mapping, against our knowledge of the astrophysical processes leading to H i clustering. Modelling of astrophysical effects affects cosmological observables through the relation linking the overall H i mass in a bound object, to the mass of the underlying dark matter halo that hosts it. We quantify the biases in estimates of standard cosmological parameters and those describing modified gravity and primordial non-Gaussianity that are obtained if one misconceives the slope of the relation between H i mass and halo mass, or the lower virial velocity cut-off for a dark matter halo to be able to host H i. Remarkably, we find that astrophysical uncertainties will not affect searches for primordial non-Gaussianity – one of the strongest science cases for H i intensity mapping – despite the signal being deeply linked to the H i bias.
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Brouwer, Margot M., Kyle A. Oman, Edwin A. Valentijn, Maciej Bilicki, Catherine Heymans, Henk Hoekstra, Nicola R. Napolitano i in. "The weak lensing radial acceleration relation: Constraining modified gravity and cold dark matter theories with KiDS-1000". Astronomy & Astrophysics 650 (czerwiec 2021): A113. http://dx.doi.org/10.1051/0004-6361/202040108.
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We present measurements of the radial gravitational acceleration around isolated galaxies, comparing the expected gravitational acceleration given the baryonic matter (gbar) with the observed gravitational acceleration (gobs), using weak lensing measurements from the fourth data release of the Kilo-Degree Survey (KiDS-1000). These measurements extend the radial acceleration relation (RAR), traditionally measured using galaxy rotation curves, by 2 decades in gobs into the low-acceleration regime beyond the outskirts of the observable galaxy. We compare our RAR measurements to the predictions of two modified gravity (MG) theories: modified Newtonian dynamics and Verlinde’s emergent gravity (EG). We find that the measured relation between gobs and gbar agrees well with the MG predictions. In addition, we find a difference of at least 6σ between the RARs of early- and late-type galaxies (split by Sérsic index and u − r colour) with the same stellar mass. Current MG theories involve a gravity modification that is independent of other galaxy properties, which would be unable to explain this behaviour, although the EG theory is still limited to spherically symmetric static mass models. The difference might be explained if only the early-type galaxies have significant (Mgas ≈ M⋆) circumgalactic gaseous haloes. The observed behaviour is also expected in Λ-cold dark matter (ΛCDM) models where the galaxy-to-halo mass relation depends on the galaxy formation history. We find that MICE, a ΛCDM simulation with hybrid halo occupation distribution modelling and abundance matching, reproduces the observed RAR but significantly differs from BAHAMAS, a hydrodynamical cosmological galaxy formation simulation. Our results are sensitive to the amount of circumgalactic gas; current observational constraints indicate that the resulting corrections are likely moderate. Measurements of the lensing RAR with future cosmological surveys (such as Euclid) will be able to further distinguish between MG and ΛCDM models if systematic uncertainties in the baryonic mass distribution around galaxies are reduced.
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Hurier, G., i R. E. Angulo. "Measuring the hydrostatic mass bias in galaxy clusters by combining Sunyaev–Zel’dovich and CMB lensing data". Astronomy & Astrophysics 610 (luty 2018): L4. http://dx.doi.org/10.1051/0004-6361/201731999.
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The cosmological parameters preferred by the cosmic microwave background (CMB) primary anisotropies predict many more galaxy clusters than those that have been detected via the thermal Sunyaev–Zeldovich (tSZ) effect. This discrepancy has attracted considerable attention since it might be evidence of physics beyond the simplest ΛCDM model. However, an accurate and robust calibration of the mass-observable relation for clusters is necessary for the comparison, which has been proven difficult to obtain so far. Here, we present new constraints on the mass–pressure relation by combining tSZ and CMB lensing measurements of optically selected clusters. Consequently, our galaxy cluster sample is independent of the data employed to derive cosmological constrains. We estimate an average hydrostatic mass bias of b = 0.26 ± 0.07, with no significant mass or redshift evolution. This value greatly reduces the discrepancy between the predictions of ΛCDM and the observed abundance of tSZ clusters but agrees with recent estimates from tSZ clustering. On the other hand, our value for b is higher than the predictions from hydrodynamical simulations. This suggests mechanisms that drive large departures from hydrostatic equilibrium and that are not included in the latest simulations, and/or unaccounted systematic errors such as biases in the cluster catalogue that are due to the optical selection.
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Deng, Heling. "μ-distortion around stupendously large primordial black holes". Journal of Cosmology and Astroparticle Physics 2021, nr 11 (1.11.2021): 054. http://dx.doi.org/10.1088/1475-7516/2021/11/054.
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Abstract In a variety of mechanisms generating primordial black holes, each black hole is expected to form along with a surrounding underdense region that roughly compensates the black hole mass. This region will propagate outwards and expand as a shell at the speed of sound in the homogeneous background. Dissipation of the shell due to Silk damping could lead to detectable μ-distortion in the CMB spectrum: if black holes are rare on the last scattering surface, the signal(s) would be pointlike; whereas if there are a sufficient number of them, we could have a uniform distortion in the CMB sky. While the current bound on the average μ-distortion is |μ̅| ≲ 10-4, the standard ΛCDM model predicts |μ̅| ∼ 10-8, which could possibly be detected in future missions. It is shown in this work that the non-observation of μ̅ beyond ΛCDM can place a new upper bound on the density of supermassive primordial black holes within the mass range 106 M ☉≲ M ≲ 1015 M ☉. Furthermore, black holes with initial mass M ≳ 1012 M ☉ could leave a pointlike distortion with μ ≳10-8 at an angular scale ∼ 1° in CMB, and its non-observation would impose an even more stringent bound on the population of these stupendously large primordial black holes.
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Laghi, Danny, Nicola Tamanini, Walter Del Pozzo, Alberto Sesana, Jonathan Gair, Stanislav Babak i David Izquierdo-Villalba. "Gravitational-wave cosmology with extreme mass-ratio inspirals". Monthly Notices of the Royal Astronomical Society 508, nr 3 (2.10.2021): 4512–31. http://dx.doi.org/10.1093/mnras/stab2741.
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ABSTRACT The Laser Interferometer Space Antenna (LISA) will open the mHz frequency window of the gravitational-wave (GW) landscape. Among all the new GW sources expected to emit in this frequency band, extreme mass-ratio inspirals (EMRIs) constitute a unique laboratory for astrophysics and fundamental physics. Here, we show that EMRIs can also be used to extract relevant cosmological information, complementary to both electromagnetic (EM) and other GW observations. By using the loudest EMRIs (S/N > 100) detected by LISA as dark standard sirens, statistically matching their sky localization region with mock galaxy catalogues, we find that constraints on H0 can reach ∼1.1 per cent (∼3.6 per cent) accuracy, at the 90 per cent credible level, in our best(worst)- case scenario. By considering a dynamical dark energy (DE) cosmological model, with ΛCDM parameters fixed by other observations, we further show that in our best(worst)- case scenario ∼5.9 per cent (∼12.3 per cent) relative uncertainties at the 90 per cent credible level can be obtained on w0, the DE equation of state parameter. Besides being relevant in their own right, EMRI measurements will be affected by different systematics compared to both EM and ground-based GW observations. Cross-validation with complementary cosmological measurements will therefore be of paramount importance, especially if convincing evidence of physics beyond ΛCDM emerges from future observations.
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Pal, Sourav, Rickmoy Samanta i Supratik Pal. "Revisiting coupled CDM-massive neutrino perturbations in diverse cosmological backgrounds". Journal of Cosmology and Astroparticle Physics 2023, nr 12 (1.12.2023): 004. http://dx.doi.org/10.1088/1475-7516/2023/12/004.
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Abstract Massive neutrinos are well-known to cause a characteristic suppression in the growth of structures at scales below the neutrino free-streaming length. A detailed understanding of this suppression is essential in the era of precision cosmology we are entering into, enabling us to better constrain the total neutrino mass and possibly probe (beyond)-ΛCDM cosmological model(s). Instead of the usual N-body simulation or Boltzmann solver, in this article we consider a two-fluid framework at the linear scales, where the neutrino fluid perturbations are coupled to the CDM (+ baryon) fluid via gravity at redshifts of interest. Treating the neutrino mass fraction f ν as a perturbative parameter, we find solutions to the system with redshift-dependent neutrino free-streaming length in ΛCDM background via two separate approaches. The perturbative scale-dependent solution is shown to be in excellent agreement with numerical solution of the two-fluid equations valid to all orders in f ν, and also agrees with results from CLASS to a good accuracy. We further generalize the framework to incorporate different evolving dark energy backgrounds and found sub-percent level differences in the suppression, all of which lie within the observational uncertainty of BOSS-like surveys. We also present a brief discussion on the prospects of the current analysis in the context of upcoming missions.
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Suyu, Sherry H. "Progress toward an accurate Hubble Constant". Proceedings of the International Astronomical Union 13, S336 (wrzesień 2017): 80–85. http://dx.doi.org/10.1017/s1743921318000133.
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AbstractThe Hubble constant is a key cosmological parameter that sets the present-day expansion rate as well as the age, size, and critical density of the Universe. Intriguingly, there is currently a tension in the measurements of its value in the standard flat ΛCDM model – observations of the Cosmic Microwave Background with the Planck satellite lead to a value of the Hubble constant that is lower than the measurements from the local Cepheids-supernovae distance ladder and strong gravitational lensing. Precise and accurate Hubble constant measurements from independent probes, including water masers, are necessary to assess the significance of this tension and the possible need of new physics beyond the current standard cosmological model. We present the progress toward an accurate Hubble constant determination.
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Pandey, Biswajit. "The Time Evolution of Mutual Information between Disjoint Regions in the Universe". Entropy 25, nr 7 (21.07.2023): 1094. http://dx.doi.org/10.3390/e25071094.
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We study the time evolution of mutual information between mass distributions in spatially separated but casually connected regions in an expanding universe. The evolution of mutual information is primarily determined by the configuration entropy rate, which depends on the dynamics of the expansion and growth of density perturbations. The joint entropy between distributions from the two regions plays a negligible role in such evolution. Mutual information decreases with time in a matter-dominated universe, whereas it stays constant in a Λ-dominated universe. The ΛCDM model and some other models of dark energy predict a minimum in mutual information beyond which dark energy dominates the dynamics of the universe. Mutual information may have deeper connections to the dark energy and accelerated expansion of the universe.
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Yniguez, Basilio, Shea Garrison-Kimmel, Michael Boylan-Kolchin i James S. Bullock. "On the stark difference in satellite distributions around the Milky Way and Andromeda". Monthly Notices of the Royal Astronomical Society 439, nr 1 (4.02.2014): 73–82. http://dx.doi.org/10.1093/mnras/stt2058.
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Abstract We compare spherically averaged radial number counts of bright (≳105 L⊙) dwarf satellite galaxies within 400 kpc of the Milky Way (MW) and M31 and find that the MW satellites are much more centrally concentrated. Remarkably, the two satellite systems are almost identical within the central 100 kpc, while M31 satellites outnumber MW satellites by about a factor of 4 at deprojected distances spanning 100–400 kpc. We compare the observed distributions to those predicted for Λ cold dark matter (ΛCDM) subhaloes using a suite of 44 high-resolution ∼1012 M⊙ halo zoom simulations, 22 of which are in pairs like the MW and M31. We find that the radial distribution of satellites around M31 is fairly typical of those predicted for subhaloes, while the MW's distribution is more centrally concentrated than any of our simulated ΛCDM haloes. One possible explanation is that our census of bright (≳105 L⊙) MW dwarf galaxies is significantly incomplete beyond ∼100 kpc of the Sun. If there were ∼8–20 more bright dwarfs orbiting undetected at 100–400 kpc distance, then the MW's radial distribution would fall within the range expected from subhalo distributions and also look very much like the known M31 system. We use our simulations to demonstrate that there is enough area left unexplored by the Sloan Digital Sky Survey and its extensions that the discovery of ∼10 new bright dwarfs is not implausible given the expected range of angular anisotropy of subhaloes in the sky.
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Thompson, Rodger I. "Non-Canonical Dark Energy Parameter Evolution in a Canonical Quintessence Cosmology". Universe 10, nr 9 (5.09.2024): 356. http://dx.doi.org/10.3390/universe10090356.
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This study considers the specific case of a flat, minimally coupled to gravity, quintessence cosmology with a dark energy quartic polynomial potential that has the same mathematical form as the Higgs potential. Previous work on this case determined that the scalar field is given by a simple expression of the Lambert W function in terms of the easily observable scale factor. This expression provides analytic equations for the evolution of cosmological dark energy parameters as a function of the scale factor for all points on the Lambert W function principal branch. The Lambert W function is zero at a scale factor of zero that marks the big bang. The evolutionary equations beyond the big bang describe a canonical universe that is similar to ΛCDM, making it an excellent dynamical template to compare with observational data. The portion of the W function principal before the big bang extends to the infinite pre-bang past. It describes a noncanonical universe with an initially very low mass density that contracts by rolling down the dark energy potential to a singularity, big bang, at the scale factor zero point. This provides a natural origin for the big bang. It also raises the possibility that the universe existed before the big bang and is far older, and that it was once far larger than its current size. The recent increasing interest in the possibility of a dynamical universe instead of ΛCDM makes the exploration of the nature of such universes particularly relevant.
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McAlpine, Stuart, John C. Helly, Matthieu Schaller, Till Sawala, Guilhem Lavaux, Jens Jasche, Carlos S. Frenk, Adrian Jenkins, John R. Lucey i Peter H. Johansson. "SIBELIUS-DARK: a galaxy catalogue of the local volume from a constrained realization simulation". Monthly Notices of the Royal Astronomical Society 512, nr 4 (8.02.2022): 5823–47. http://dx.doi.org/10.1093/mnras/stac295.
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ABSTRACT We present sibelius-dark, a constrained realization simulation of the local volume to a distance of 200 Mpc from the Milky Way. sibelius-dark is the first study of the ‘Simulations Beyond The Local Universe’ (sibelius) project, which has the goal of embedding a model Local Group-like system within the correct cosmic environment. The simulation is dark-matter-only, with the galaxy population calculated using the semi-analytic model of galaxy formation, galform. We demonstrate that the large-scale structure that emerges from the sibelius constrained initial conditions matches well the observational data. The inferred galaxy population of sibelius-dark also match well the observational data, both statistically for the whole volume and on an object-by-object basis for the most massive clusters. For example, the K-band number counts across the whole sky, and when divided between the northern and southern Galactic hemispheres, are well reproduced by sibelius-dark. We find that the local volume is somewhat unusual in the wider context of ΛCDM: it contains an abnormally high number of supermassive clusters, as well as an overall large-scale underdensity at the level of ≈5 per cent relative to the cosmic mean. However, whilst rare, the extent of these peculiarities does not significantly challenge the ΛCDM model. sibelius-dark is the most comprehensive constrained realization simulation of the local volume to date, and with this paper we publicly release the halo and galaxy catalogues at z = 0, which we hope will be useful to the wider astronomy community.
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Dwivedi, Sowmaydeep, i Marcus Högås. "2D BAO vs. 3D BAO: Solving the Hubble Tension with Bimetric Cosmology". Universe 10, nr 11 (28.10.2024): 406. http://dx.doi.org/10.3390/universe10110406.
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Ordinary 3D Baryon Acoustic Oscillations (BAO) data are model-dependent, requiring the assumption of a cosmological model to calculate comoving distances during data reduction. Throughout the present-day literature, the assumed model is ΛCDM. However, it has been pointed out in several recent works that this assumption can be inadequate when analyzing alternative cosmologies, potentially biasing the Hubble constant (H0) low, thus contributing to the Hubble tension. To address this issue, 3D BAO data can be replaced with 2D BAO data, which are only weakly model-dependent. The impact of using 2D BAO data, in combination with alternative cosmological models beyond ΛCDM, has been explored for several phenomenological models, showing a promising reduction in the Hubble tension. In this work, we accommodate these models in the theoretically robust framework of bimetric gravity. This is a modified theory of gravity that exhibits a transition from a (possibly) negative cosmological constant in the early universe to a positive one in the late universe. By combining 2D BAO data with cosmic microwave background and type Ia supernovae data, we find that the inverse distance ladder in this theory yields a Hubble constant of H0=(71.0±0.9)km/s/Mpc, consistent with the SH0ES local distance ladder measurement of H0=(73.0±1.0)km/s/Mpc. Replacing 2D BAO with 3D BAO results in H0=(68.6±0.5)km/s/Mpc from the inverse distance ladder. We conclude that the choice of BAO data significantly impacts the Hubble tension, with ordinary 3D BAO data exacerbating the tension, while 2D BAO data provide results consistent with the local distance ladder.
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Lemos, P., M. Raveri, A. Campos, Y. Park, C. Chang, N. Weaverdyck, D. Huterer i in. "Assessing tension metrics with dark energy survey and Planck data". Monthly Notices of the Royal Astronomical Society 505, nr 4 (14.06.2021): 6179–94. http://dx.doi.org/10.1093/mnras/stab1670.
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ABSTRACT Quantifying tensions – inconsistencies amongst measurements of cosmological parameters by different experiments – has emerged as a crucial part of modern cosmological data analysis. Statistically significant tensions between two experiments or cosmological probes may indicate new physics extending beyond the standard cosmological model and need to be promptly identified. We apply several tension estimators proposed in the literature to the dark energy survey (DES) large-scale structure measurement and Planck cosmic microwave background data. We first evaluate the responsiveness of these metrics to an input tension artificially introduced between the two, using synthetic DES data. We then apply the metrics to the comparison of Planck and actual DES Year 1 data. We find that the parameter differences, Eigentension, and Suspiciousness metrics all yield similar results on both simulated and real data, while the Bayes ratio is inconsistent with the rest due to its dependence on the prior volume. Using these metrics, we calculate the tension between DES Year 1 3 × 2pt and Planck, finding the surveys to be in ∼2.3σ tension under the ΛCDM paradigm. This suite of metrics provides a toolset for robustly testing tensions in the DES Year 3 data and beyond.
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Bargiacchi, G., G. Risaliti, M. Benetti, S. Capozziello, E. Lusso, A. Saccardi i M. Signorini. "Cosmography by orthogonalized logarithmic polynomials". Astronomy & Astrophysics 649 (maj 2021): A65. http://dx.doi.org/10.1051/0004-6361/202140386.
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Cosmography is a powerful tool for investigating the Universe kinematic and then for reconstructing the dynamics in a model-independent way. However, recent new measurements of supernovae Ia and quasars have populated the Hubble diagram up to high redshifts (z ∼ 7.5) and the application of the traditional cosmographic approach has become less straightforward due to the large redshifts implied. Here we investigate this issue through an expansion of the luminosity distance–redshift relation in terms of orthogonal logarithmic polynomials. In particular, we point out the advantages of a new procedure called orthogonalization, and we show that such an expansion provides a very good fit in the whole z = 0 ÷ 7.5 range to both real and mock data obtained assuming various cosmological models. Moreover, although the cosmographic series is tested well beyond its convergence radius, the parameters obtained expanding the luminosity distance–redshift relation for the Lambda cold dark matter (ΛCDM) model are broadly consistent with the results from a fit of mock data obtained with the same cosmological model. This provides a method for testing the reliability of a cosmographic function to study cosmological models at high redshifts, and it demonstrates that the logarithmic polynomial series can be used to test the consistency of the ΛCDM model with the current Hubble diagram of quasars and supernovae Ia. We confirm a strong tension (at > 4σ) between the concordance cosmological model and the Hubble diagram at z > 1.5. This tension is dominated by the contribution of quasars at z > 2 and also starts to be present in the few supernovae Ia observed at z > 1.
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Giocoli, Carlo, Federico Marulli, Lauro Moscardini, Mauro Sereno, Alfonso Veropalumbo, Lorenzo Gigante, Matteo Maturi i in. "AMICO galaxy clusters in KiDS-DR3". Astronomy & Astrophysics 653 (wrzesień 2021): A19. http://dx.doi.org/10.1051/0004-6361/202140795.
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Context. The large-scale mass distribution around dark matter haloes hosting galaxy clusters provides sensitive cosmological information. Aims. In this work we make use of a large photometric galaxy cluster sample, constructed from the public Third Data Release of the Kilo-Degree Survey, and the corresponding shear signal, to assess cluster masses and test the concordance Λ-cold dark matter (ΛCDM) model. In particular, we study the weak gravitational lensing effects on scales beyond the cluster virial radius, where the signal is dominated by correlated and uncorrelated matter density distributions along the line of sight. The analysed catalogue consists of 6962 galaxy clusters, in the redshift range 0.1 ≤ z ≤ 0.6 and with signal-to-noise ratios higher than 3.5. Methods. We perform a full Bayesian analysis to model the stacked shear profiles of these clusters. The adopted likelihood function considers both the small-scale one-halo term, used primarily to constrain the cluster structural properties, and the two-halo term, that can be used to constrain cosmological parameters. Results. We find that the adopted modelling is successful in assessing both the cluster masses and the total matter density parameter, ΩM, when fitting shear profiles up to the largest available scales of 35 Mpc h−1. Moreover, our results provide a strong observational evidence of the two-halo signal in the stacked gravitational lensing of galaxy clusters, further demonstrating the reliability of this probe for cosmological studies. The main result of this work is a robust constraint on ΩM, assuming a flat ΛCDM cosmology. We get ΩM = 0.29 ± 0.02, estimated from the full posterior probability distribution, consistent with the estimates from cosmic microwave background experiments.