{"topic":"dark-energy-hubble-tension","sort":"top","limit":25,"offset":0,"count":25,"papers":[{"id":"arxiv:1303.5076","kind":"article","title":"Planck 2013 results. XVI. Cosmological parameters","authors":["Peter A. R. Ade","N. Aghanim","Charmaine Armitage-Caplan","M. Arnaud","M. Ashdown","Fernando Atrio-Barandela","J. Aumont","C. Baccigalupi","Anthony J. Banday","R. Belén Barreiro","J. G. Bartlett","E. Battaner","K. Benabed","A. Benoı̂t","A. Benoit-Lévy","J.-P. Bernard","Marco Bersanelli","P. Bielewicz","Jérôme Bobin","James J. Bock","A. Bonaldi","John Richard Bond","Jullian Borrill","François R. Bouchet","M. Bridges"],"author_count":100,"year":2014,"published":"2014-02-25","venue":"Astronomy and Astrophysics","cited_by":6888,"doi":"10.1051/0004-6361/201321591","arxiv_id":"1303.5076","nct_id":null,"source_url":"https://doi.org/10.1051/0004-6361/201321591","archive_url":"https://space-kitty.com/papers/arxiv:1303.5076","updated":"2014-03-20","pmid":null,"pmcid":null,"openalex_id":"W2139937287","pdf_url":"https://www.aanda.org/articles/aa/pdf/2014/11/aa21591-13.pdf","abstract":"We present the first results based on Planck measurements of the CMB temperature and lensing-potential power spectra. The Planck spectra at high multipoles are extremely well described by the standard spatially-flat six-parameter LCDM cosmology. In this model Planck data determine the cosmological parameters to high precision. We find a low value of the Hubble constant, H0=67.3+/-1.2 km/s/Mpc and a high value of the matter density parameter, Omega_m=0.315+/-0.017 (+/-1 sigma errors) in excellent agreement with constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent-level precision using Planck CMB data alone. We present results from an analysis of extensions to the standard cosmology, using astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured significantly over standard LCDM. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find a 95% upper limit of r<0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles. Using BAO and CMB data, we find N_eff=3.30+/-0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the summed neutrino mass. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N_eff=3.046. We find no evidence for dynamical dark energy. Despite the success of the standard LCDM model, this cosmology does not provide a good fit to the CMB power spectrum at low multipoles, as noted previously by the WMAP team. While not of decisive significance, this is an anomaly in an otherwise self-consistent analysis of the Planck temperature data.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1804.10655","kind":"article","title":"The Banana Bridge - The Unitary Kinematic Solution to the Hubble Tension and the 1.618 x 137 Master Law","authors":["Epperson, Arya"],"author_count":1,"year":2026,"published":"2026-03-18","venue":"Zenodo (CERN European Organization for Nuclear Research)","cited_by":510,"doi":"10.5281/zenodo.19098596","arxiv_id":"1804.10655","nct_id":null,"source_url":"https://arxiv.org/abs/arXiv:1804.10655","archive_url":"https://space-kitty.com/papers/arxiv:1804.10655","updated":"2018-05-25","pmid":null,"pmcid":null,"openalex_id":"W3101030129","pdf_url":"https://arxiv.org/pdf/1804.10655","abstract":"We present HST photometry of a selected sample of 50 long-period, low-extinction Milky Way Cepheids measured on the same WFC3 F555W, F814W, and F160W-band photometric system as extragalactic Cepheids in SN Ia hosts. These bright Cepheids were observed with the WFC3 spatial scanning mode in the optical and near-infrared to mitigate saturation and reduce pixel-to-pixel calibration errors to reach a mean photometric error of 5 millimags per observation. We use the new Gaia DR2 parallaxes and HST photometry to simultaneously constrain the cosmic distance scale and to measure the DR2 parallax zeropoint offset appropriate for Cepheids. We find a value for the zeropoint offset of -46 +/- 13 muas or +/- 6 muas for a fixed distance scale, higher than found from quasars, as expected, for these brighter and redder sources. The precision of the distance scale from DR2 has been reduced by a factor of 2.5 due to the need to independently determine the parallax offset. The best fit distance scale is 1.006 +/- 0.033, relative to the scale from Riess et al 2016 with H0=73.24 km/s/Mpc used to predict the parallaxes photometrically, and is inconsistent with the scale needed to match the Planck 2016 CMB data combined with LCDM at the 2.9 sigma confidence level (99.6%). At 96.5% confidence we find that the formal DR2 errors may be underestimated as indicated. We identify additional error associated with the use of augmented Cepheid samples utilizing ground-based photometry and discuss their likely origins. Including the DR2 parallaxes with all prior distance ladder data raises the current tension between the late and early Universe route to the Hubble constant to 3.8 sigma (99.99 %). With the final expected precision from Gaia, the sample of 50 Cepheids with HST photometry will limit to 0.5% the contribution of the first rung of the distance ladder to the uncertainty in the Hubble constant.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1710.00845","kind":"article","title":"The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample","authors":["Daniel M. Scolnic","D. O. Jones","A. Rest","Y. C. Pan","R. Chornock","R. J. Foley","M. E. Huber","Rick Kessler","Gautham Narayan","Adam G. Riess","S. Rodney","Edo Berger","Dillon Brout","Peter Challis","M. R. Drout","Douglas P. Finkbeiner","R. Lunnan","R. Kirshner","Nathan Sanders","Edward F. Schlafly","Stephen J. Smartt","Christopher W. Stubbs","John L. Tonry","W. M. Wood‐Vasey","Michael M. Foley"],"author_count":40,"year":2018,"published":"2018-05-29","venue":"The Astrophysical Journal","cited_by":2710,"doi":"10.3847/1538-4357/aab9bb","arxiv_id":"1710.00845","nct_id":null,"source_url":"https://doi.org/10.3847/1538-4357/aab9bb","archive_url":"https://space-kitty.com/papers/arxiv:1710.00845","updated":"2018-03-26","pmid":null,"pmcid":null,"openalex_id":"W2763117186","pdf_url":"https://iopscience.iop.org/article/10.3847/1538-4357/aab9bb/pdf","abstract":"We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the PS1 SN photometry, astrometry and calibration that reduce the systematic uncertainties in the PS1 SN Ia distances. We combine the subset of 279 PS1 SN Ia ($0.03 < z < 0.68$) with useful distance estimates of SN Ia from SDSS, SNLS, various low-z and HST samples to form the largest combined sample of SN Ia consisting of a total of 1048 SN Ia ranging from $0.01 < z < 2.3$, which we call the `Pantheon Sample'. When combining Planck 2015 CMB measurements with the Pantheon SN sample, we find $Ω_m=0.307\\pm0.012$ and $w = -1.026\\pm0.041$ for the wCDM model. When the SN and CMB constraints are combined with constraints from BAO and local H0 measurements, the analysis yields the most precise measurement of dark energy to date: $w0 = -1.007\\pm 0.089$ and $wa = -0.222 \\pm0.407$ for the w0waCDM model. Tension with a cosmological constant previously seen in an analysis of PS1 and low-z SNe has diminished after an increase of $2\\times$ in the statistics of the PS1 sample, improved calibration and photometry, and stricter light-curve quality cuts. We find the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. This must be addressed for future progress in using SN Ia to measure dark energy.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2103.01183","kind":"article","title":"In the realm of the Hubble tension—a review of solutions *","authors":["Eleonora Di Valentino","Olga Mena","Supriya Pan","Luca Visinelli","Weiqiang Yang","ALESSANDRO MELCHIORRI","David F Mota","Adam G Riess","Joseph I. Silk"],"author_count":9,"year":2021,"published":"2021-06-04","venue":"Classical and Quantum Gravity","cited_by":2077,"doi":"10.1088/1361-6382/ac086d","arxiv_id":"2103.01183","nct_id":null,"source_url":"https://doi.org/10.1088/1361-6382/ac086d","archive_url":"https://space-kitty.com/papers/arxiv:2103.01183","updated":"2021-06-05","pmid":null,"pmcid":null,"openalex_id":"W3135850969","pdf_url":"https://iopscience.iop.org/article/10.1088/1361-6382/ac086d/pdf","abstract":"The $Λ$CDM model provides a good fit to a large span of cosmological data but harbors areas of phenomenology. With the improvement of the number and the accuracy of observations, discrepancies among key cosmological parameters of the model have emerged. The most statistically significant tension is the $4-6σ$ disagreement between predictions of the Hubble constant $H_0$ by early time probes with $Λ$CDM model, and a number of late time, model-independent determinations of $H_0$ from local measurements of distances and redshifts. The high precision and consistency of the data at both ends present strong challenges to the possible solution space and demand a hypothesis with enough rigor to explain multiple observations--whether these invoke new physics, unexpected large-scale structures or multiple, unrelated errors. We present a thorough review of the problem, including a discussion of recent Hubble constant estimates and a summary of the proposed theoretical solutions. Some of the models presented are formally successful, improving the fit to the data in light of their additional degrees of freedom, restoring agreement within $1-2σ$ between {\\it Planck} 2018, using CMB power spectra data, BAO, Pantheon SN data, and R20, the latest SH0ES Team measurement of the Hubble constant ($H_0 = 73.2 \\pm 1.3{\\rm\\,km\\,s^{-1}\\,Mpc^{-1}}$ at 68\\% confidence level). Reduced tension might not simply come from a change in $H_0$ but also from an increase in its uncertainty due to degeneracy with additional physics, pointing to the need for additional probes. While no specific proposal makes a strong case for being highly likely or far better than all others, solutions involving early or dynamical dark energy, neutrino interactions, interacting cosmologies, primordial magnetic fields, and modified gravity provide the best options until a better alternative comes along.[Abridged]","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1604.01424","kind":"article","title":"A 2.4% DETERMINATION OF THE LOCAL VALUE OF THE HUBBLE CONSTANT *","authors":["Adam G. Riess","Lucas M. Macri","Samantha L. Hoffmann","Dan Scolnic","Stefano Casertano","A. V. Filippenko","Brad E. Tucker","Mark J. Reid","David O. Jones","Jeffrey M. Silverman","Ryan Chornock","Peter Challis","Wenlong Yuan","Peter J. Brown","Ryan J. Foley"],"author_count":15,"year":2016,"published":"2016-07-20","venue":"The Astrophysical Journal","cited_by":2249,"doi":"10.3847/0004-637x/826/1/56","arxiv_id":"1604.01424","nct_id":null,"source_url":"https://doi.org/10.3847/0004-637x/826/1/56","archive_url":"https://space-kitty.com/papers/arxiv:1604.01424","updated":"2016-06-09","pmid":null,"pmcid":null,"openalex_id":"W2339590713","pdf_url":"https://iopscience.iop.org/article/10.3847/0004-637X/826/1/56/pdf","abstract":"We use the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) to reduce the uncertainty in the local value of the Hubble constant (H_0) from 3.3% to 2.4%. Improvements come from new, near-infrared observations of Cepheid variables in 11 new hosts of recent SNe~Ia, more than doubling the sample of SNe~Ia having a Cepheid-calibrated distance for a total of 19; these leverage the magnitude-z relation based on 300 SNe~Ia at z<0.15. All 19 hosts and the megamaser system NGC4258 were observed with WFC3, thus nullifying cross-instrument zeropoint errors. Other improvements include a 33% reduction in the systematic uncertainty in the maser distance to NGC4258, more Cepheids and a more robust distance to the LMC from late-type DEBs, HST observations of Cepheids in M31, and new HST-based trigonometric parallaxes for Milky Way (MW) Cepheids. We consider four geometric distance calibrations of Cepheids: (i) megamasers in NGC4258, (ii) 8 DEBs in the LMC, (iii) 15 MW Cepheids with parallaxes, and (iv) 2 DEBs in M31. H_0 from each is 72.25+/-2.51, 72.04+/-2.67, 76.18+/-2.37, and 74.50+/-3.27 km/sec/Mpc, respectively. Our best estimate of 73.24+/-1.74 km/sec/Mpc combines the anchors NGC4258, MW, and LMC, and includes systematic errors for a final uncertainty of 2.4%. This value is 3.4 sigma higher than 66.93+/-0.62 km/sec/Mpc predicted by LambdaCDM with 3 neutrinos with mass 0.06 eV and the Planck data, but reduces to 2.1 sigma relative to the prediction of 69.3+/-0.7 km/sec/Mpc with the combination of WMAP+ACT+SPT+BAO, suggesting systematic uncertainties in CMB measurements may play a role in the tension. If we take the conflict between Planck and H_0 at face value, one plausible explanation could involve an additional source of dark radiation in the early Universe in the range of Delta N_eff=0.4-1. We anticipate significant improvements in H_0 from upcoming parallax measurements.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"doi:10.3847/1538-4357/ac8e04","kind":"article","title":"The Pantheon+ Analysis: Cosmological Constraints","authors":["Dillon Brout","Daniel M. Scolnic","B Popovic","Adam G. Riess","Anthony Carr","Joe Zuntz","Rick Kessler","T. M. Davis","S. R. Hinton","D. O. Jones","W. D. Kenworthy","Erik R. Peterson","Khaled Said","G. Taylor","Noor Ali","P. Armstrong","Pranav Charvu","Arianna Dwomoh","Cole Meldorf","A. Palmese","Helen Qu","Benjamin M. Rose","B. Sánchez","Christopher W. Stubbs","M. Vincenzi"],"author_count":48,"year":2022,"published":"2022-10-01","venue":"The Astrophysical Journal","cited_by":1368,"doi":"10.3847/1538-4357/ac8e04","arxiv_id":null,"nct_id":null,"source_url":"https://doi.org/10.3847/1538-4357/ac8e04","archive_url":"https://space-kitty.com/papers/doi:10.3847/1538-4357/ac8e04","updated":null,"pmid":null,"pmcid":null,"openalex_id":"W4282961335","pdf_url":"https://iopscience.iop.org/article/10.3847/1538-4357/ac8e04/pdf","abstract":"Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0 CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s −1 Mpc −1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s −1 Mpc −1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.","abstract_license":"CC-BY (publisher license, via OpenAlex)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex","attribution":"Abstract of \"The Pantheon+ Analysis: Cosmological Constraints\" by Dillon Brout, Daniel M. Scolnic, B Popovic et al., https://doi.org/10.3847/1538-4357/ac8e04, used under its Creative Commons Attribution license (CC-BY); markup removed, otherwise unmodified."},{"id":"arxiv:2007.08991","kind":"article","title":"Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory","authors":["Shadab Alam","M Aubert","Santiago Avila","Christophe Balland","Julian Bautista","Matthew A. Bershady","Dmitry Bizyaev","Michael Rogers Blanton","Adam S. Bolton","Jo Bovy","J. Brinkmann","Joel R. Brownstein","E. Burtin","Solène Chabanier","Michael J. Chapman","Peter Doohyun Choi","Chia-Hsun Chuang","Johan Comparat","M.-C. Cousinou","Andrei Cuceu","Kyle Dawson","S. de la Torre","Arnaud de Mattia","Victoria de Sainte Agathe","Hélion du Mas des Bourboux"],"author_count":99,"year":2021,"published":"2021-04-28","venue":"Physical review. D/Physical review. D.","cited_by":1351,"doi":"10.1103/physrevd.103.083533","arxiv_id":"2007.08991","nct_id":null,"source_url":"https://doi.org/10.1103/physrevd.103.083533","archive_url":"https://space-kitty.com/papers/arxiv:2007.08991","updated":"2024-07-09","pmid":null,"pmcid":null,"openalex_id":"W3043102132","pdf_url":"http://link.aps.org/pdf/10.1103/PhysRevD.103.083533","abstract":"We present the cosmological implications from final measurements of clustering using galaxies, quasars, and Ly$α$ forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, $r_d$, from eight different samples and six measurements of the growth rate parameter, $fσ_8$, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, $Λ$CDM model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization the BAO data provide nearly an order of magnitude improvement on curvature constraints. The RSD measurements indicate a growth rate that is consistent with predictions from Planck primary data and with General Relativity. When combining the results of SDSS BAO and RSD with external data, all multiple-parameter extensions remain consistent with a $Λ$CDM model. Regardless of cosmological model, the precision on $Ω_Λ$, $H_0$, and $σ_8$, remains at roughly 1\\%, showing changes of less than 0.6\\% in the central values between models. The inverse distance ladder measurement under a o$w_0w_a$CDM yields $H_0= 68.20 \\pm 0.81 \\, \\rm km\\, s^{-1} Mpc^{-1}$, remaining in tension with several direct determination methods. (abridged)","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"other-oa","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1907.10625","kind":"article","title":"Tensions between the early and late Universe","authors":["Licia Verde","Tommaso Treu","Adam G. Riess"],"author_count":3,"year":2019,"published":"2019-09-27","venue":"Nature Astronomy","cited_by":1380,"doi":"10.1038/s41550-019-0902-0","arxiv_id":"1907.10625","nct_id":null,"source_url":"https://doi.org/10.1038/s41550-019-0902-0","archive_url":"https://space-kitty.com/papers/arxiv:1907.10625","updated":"2019-07-24","pmid":null,"pmcid":null,"openalex_id":"W2963125685","pdf_url":"https://arxiv.org/pdf/1907.10625","abstract":"The standard cosmological model successfully describes many observations from widely different epochs of the Universe, from primordial nucleosynthesis to the accelerating expansion of the present day. However, as the basic cosmological parameters of the model are being determined with increasing and unprecedented precision, it is not guaranteed that the same model will fit more precise observations from widely different cosmic epochs. Discrepancies developing between observations at early and late cosmological time may require an expansion of the standard model, and may lead to the discovery of new physics. The workshop \"Tensions between the Early and the Late Universe\" was held at the Kavli Institute for Theoretical Physics on July 15-17 2019 (More details of the workshop (including on-line presentations) are given at the website: https://www.kitp.ucsb.edu/activities/enervac-c19) to evaluate increasing evidence for these discrepancies, primarily in the value of the Hubble constant as well as ideas recently proposed to explain this tension. Multiple new observational results for the Hubble constant were presented in the time frame of the workshop using different probes: Cepheids, strong lensing time delays, tip of the red giant branch (TRGB), megamasers, Oxygen-rich Miras and surface brightness fluctuations (SBF) resulting in a set of six new ones in the last several months. Here we present the summary plot of the meeting that shows combining any three independent approaches to measure H$_0$ in the late universe yields tension with the early Universe values between 4.0$σ$ and 5.8$σ$. This shows that the discrepancy does not appear to be dependent on the use of any one method, team, or source. Theoretical ideas to explain the discrepancy focused on new physics in the decade of expansion preceding recombination as the most plausible. This is a brief summary of the workshop.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1907.04869","kind":"article","title":"H0LiCOW – XIII. A 2.4 per cent measurement of H0 from lensed quasars: 5.3σ tension between early- and late-Universe probes","authors":["Kenneth C. Wong","Sherry H. Suyu","Geoff C.-F. Chen","Cristian E. Rusu","Martin Millon","Dominique Sluse","V. Bonvin","Christopher D. Fassnacht","S. Taubenberger","Matthew W. Auger","Simon Birrer","J. H. H. Chan","F. Courbin","Stefan Hilbert","O. Tihhonova","Tommaso Treu","Adriano Agnello","Xuheng Ding","Inh Jee","Eiichiro Komatsu","Anowar J. Shajib","Alessandro Sonnenfeld","Roger D. Blandford","Léon V. E. Koopmans","Philip J Marshall"],"author_count":26,"year":2019,"published":"2019-09-16","venue":"Monthly Notices of the Royal Astronomical Society","cited_by":1178,"doi":"10.1093/mnras/stz3094","arxiv_id":"1907.04869","nct_id":null,"source_url":"https://doi.org/10.1093/mnras/stz3094","archive_url":"https://space-kitty.com/papers/arxiv:1907.04869","updated":"2019-11-06","pmid":null,"pmcid":null,"openalex_id":"W2961457169","pdf_url":"https://academic.oup.com/mnras/article-pdf/498/1/1420/33755111/stz3094.pdf","abstract":"We present a measurement of the Hubble constant ($H_{0}$) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analyzed blindly with respect to the cosmological parameters. In a flat $Λ$CDM cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}$, a 2.4% precision measurement, in agreement with local measurements of $H_{0}$ from type Ia supernovae calibrated by the distance ladder, but in $3.1σ$ tension with $Planck$ observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of time-delay cosmography and the distance ladder results is in $5.3σ$ tension with $Planck$ CMB determinations of $H_{0}$ in flat $Λ$CDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat $Λ$CDM using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from $Planck$, baryon acoustic oscillations, and type Ia supernovae. Time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with $Planck$. Using the distance constraints from time-delay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our $H_0$ inference to cosmological model assumptions. For six different cosmological models, our combined inference on $H_{0}$ ranges from $\\sim73$-$78~\\mathrm{km~s^{-1}~Mpc^{-1}}$, which is consistent with the local distance ladder constraints.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1811.04083","kind":"article","title":"Early Dark Energy Can Resolve The Hubble Tension","authors":["Vivian Poulin","Tristan L. Smith","Tanvi Karwal","Marc Kamionkowski"],"author_count":4,"year":2018,"published":"2018-11-09","venue":"Phys. Rev. Lett. 122, 221301 (2019)","cited_by":1014,"doi":"10.1103/physrevlett.122.221301","arxiv_id":"1811.04083","nct_id":null,"source_url":"https://arxiv.org/abs/1811.04083","archive_url":"https://space-kitty.com/papers/arxiv:1811.04083","updated":"2019-06-11","pmid":"31283280","pmcid":null,"openalex_id":"W2900418540","pdf_url":"https://arxiv.org/pdf/1811.04083","abstract":"Early dark energy (EDE) that behaves like a cosmological constant at early times (redshifts $z\\gtrsim3000$) and then dilutes away like radiation or faster at later times can solve the Hubble tension. In these models, the sound horizon at decoupling is reduced resulting in a larger value of the Hubble parameter $H_0$ inferred from the cosmic microwave background (CMB). We consider two physical models for this EDE, one involving an oscillating scalar field and another a slowly-rolling field. We perform a detailed calculation of the evolution of perturbations in these models. A Markov Chain Monte Carlo search of the parameter space for the EDE parameters, in conjunction with the standard cosmological parameters, identifies regions in which $H_0$ inferred from {\\it Planck} CMB data agrees with the SH0ES local measurement. In these cosmologies, current baryon acoustic oscillation and supernova data are described as successfully as in \\LCDM, while the fit to {\\it Planck} data is slightly improved. Future CMB and large-scale-structure surveys will further probe this scenario.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO","hep-ph"],"details":null,"provenance":"arxiv+openalex","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2012.08534","kind":"article","title":"Cosmic Distances Calibrated to 1% Precision with Gaia EDR3 Parallaxes and Hubble Space Telescope Photometry of 75 Milky Way Cepheids Confirm Tension with ΛCDM","authors":["Adam G. Riess","Stefano Casertano","Wenlong Yuan","J. Bradley Bowers","Lucas Macri","Joel Zinn","Dan Scolnic"],"author_count":7,"year":2021,"published":"2021-02-01","venue":"The Astrophysical Journal Letters","cited_by":815,"doi":"10.3847/2041-8213/abdbaf","arxiv_id":"2012.08534","nct_id":null,"source_url":"https://doi.org/10.3847/2041-8213/abdbaf","archive_url":"https://space-kitty.com/papers/arxiv:2012.08534","updated":"2021-01-02","pmid":null,"pmcid":null,"openalex_id":"W3110936278","pdf_url":"https://iopscience.iop.org/article/10.3847/2041-8213/abdbaf/pdf","abstract":"We present an expanded sample of 75 Milky Way Cepheids with Hubble Space Telescope (HST) photometry and Gaia EDR3 parallaxes which we use to recalibrate the extragalactic distance ladder and refine the determination of the Hubble constant. All HST observations were obtained with the same instrument (WFC3) and filters (F555W, F814W, F160W) used for imaging of extragalactic Cepheids in Type Ia supernova (SN Ia) hosts. The HST observations used the WFC3 spatial scanning mode to mitigate saturation and reduce pixel-to-pixel calibration errors, reaching a mean photometric error of 5 millimags per observation. We use new Gaia EDR3 parallaxes, vastly improved since DR2, and the Period-Luminosity (PL) relation of these Cepheids to simultaneously calibrate the extragalactic distance ladder and to refine the determination of the Gaia EDR3 parallax offset. The resulting geometric calibration of Cepheid luminosities has 1.0% precision, better than any alternative geometric anchor. Applied to the calibration of SNe~Ia, it results in a measurement of the Hubble constant of 73.0 +/- 1.4 km/sec/Mpc, in good agreement with conclusions based on earlier Gaia data releases. We also find the slope of the Cepheid PL relation in the Milky Way, and the metallicity dependence of its zeropoint, to be in good agreement with the mean values derived from other galaxies. In combination with the best complementary sources of Cepheid calibration, we reach 1.8% precision and find H_0=73.2 +/- 1.3 km/sec/Mpc, a 4.2 sigma difference with the prediction from Planck CMB observations under LambdaCDM. We expect to reach ~1.3% precision in the near term from an expanded sample of ~40 SNe Ia in Cepheid hosts.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1907.05922","kind":"article","title":"The Carnegie-Chicago Hubble Program. VIII. An Independent Determination of the Hubble Constant Based on the Tip of the Red Giant Branch*","authors":["Wendy L. Freedman","Barry F. Madore","Dylan Hatt","Taylor J. Hoyt","In Sung Jang","Rachael Lynn Beaton","C. R. Burns","Myung Gyoon Lee","Andrew J. Monson","J. Neeley","Mark M. Phillips","J. A. Rich","Mark Seibert"],"author_count":13,"year":2019,"published":"2019-08-29","venue":"The Astrophysical Journal","cited_by":843,"doi":"10.3847/1538-4357/ab2f73","arxiv_id":"1907.05922","nct_id":null,"source_url":"https://doi.org/10.3847/1538-4357/ab2f73","archive_url":"https://space-kitty.com/papers/arxiv:1907.05922","updated":"2019-07-12","pmid":null,"pmcid":null,"openalex_id":"W2959471610","pdf_url":"https://iopscience.iop.org/article/10.3847/1538-4357/ab2f73/pdf","abstract":"We present a new and independent determination of the local value of the Hubble constant based on a calibration of the Tip of the Red Giant Branch (TRGB) applied to Type Ia supernovae (SNeIa). We find a value of Ho = 69.8 +/- 0.8 (+/-1.1\\% stat) +/- 1.7 (+/-2.4\\% sys) km/sec/Mpc. The TRGB method is both precise and accurate, and is parallel to, but independent of the Cepheid distance scale. Our value sits midway in the range defined by the current Hubble tension. It agrees at the 1.2-sigma level with that of the Planck 2018 estimate, and at the 1.7-sigma level with the SHoES measurement of Ho based on the Cepheid distance scale. The TRGB distances have been measured using deep Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging of galaxy halos. The zero point of the TRGB calibration is set with a distance modulus to the Large Magellanic Cloud of 18.477 +/- 0.004 (stat) +/-0.020 (sys) mag, based on measurement of 20 late-type detached eclipsing binary (DEB) stars, combined with an HST parallax calibration of a 3.6 micron Cepheid Leavitt law based on Spitzer observations. We anchor the TRGB distances to galaxies that extend our measurement into the Hubble flow using the recently completed Carnegie Supernova Project I sample containing about 100 well-observed SNeIa. There are several advantages of halo TRGB distance measurements relative to Cepheid variables: these include low halo reddening, minimal effects of crowding or blending of the photometry, only a shallow (calibrated) sensitivity to metallicity in the I-band, and no need for multiple epochs of observations or concerns of different slopes with period. In addition, the host masses of our TRGB host-galaxy sample are higher on average than the Cepheid sample, better matching the range of host-galaxy masses in the CSP distant sample, and reducing potential systematic effects in the SNeIa measurements.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2503.14738","kind":"article","title":"DESI DR2 Results II: Measurements of Baryon Acoustic Oscillations and Cosmological Constraints","authors":["DESI Collaboration","M. Abdul-Karim","J. Aguilar","S. Ahlen","S. Alam","L. Allen","C. Allende Prieto","O. Alves","A. Anand","U. Andrade","E. Armengaud","A. Aviles","S. Bailey","C. Baltay","P. Bansal","A. Bault","J. Behera","S. BenZvi","D. Bianchi","C. Blake","S. Brieden","A. Brodzeller","D. Brooks","E. Buckley-Geer","E. Burtin"],"author_count":187,"year":2025,"published":"2025-03-18","venue":"Phys. Rev. D 112, 083515, 2025","cited_by":617,"doi":"10.1103/tr6y-kpc6","arxiv_id":"2503.14738","nct_id":null,"source_url":"https://arxiv.org/abs/2503.14738","archive_url":"https://space-kitty.com/papers/arxiv:2503.14738","updated":"2025-10-09","pmid":null,"pmcid":null,"openalex_id":"W4410636511","pdf_url":"https://arxiv.org/pdf/2503.14738","abstract":"We present baryon acoustic oscillation (BAO) measurements from more than 14 million galaxies and quasars drawn from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2), based on three years of operation. For cosmology inference, these galaxy measurements are combined with DESI Lyman-$α$ forest BAO results presented in a companion paper. The DR2 BAO results are consistent with DESI DR1 and SDSS, and their distance-redshift relationship matches those from recent compilations of supernovae (SNe) over the same redshift range. The results are well described by a flat $Λ$CDM model, but the parameters preferred by BAO are in mild, $2.3σ$ tension with those determined from the cosmic microwave background (CMB), although the DESI results are consistent with the acoustic angular scale $θ_*$ that is well-measured by Planck. This tension is alleviated by dark energy with a time-evolving equation of state parametrized by $w_0$ and $w_a$, which provides a better fit to the data, with a favored solution in the quadrant with $w_0>-1$ and $w_a<0$. This solution is preferred over $Λ$CDM at $3.1σ$ for the combination of DESI BAO and CMB data. When also including SNe, the preference for a dynamical dark energy model over $Λ$CDM ranges from $2.8-4.2σ$ depending on which SNe sample is used. We present evidence from other data combinations which also favor the same behavior at high significance. From the combination of DESI and CMB we derive 95% upper limits on the sum of neutrino masses, finding $\\sum m_ν<0.064$ eV assuming $Λ$CDM and $\\sum m_ν<0.16$ eV in the $w_0w_a$ model. Unless there is an unknown systematic error associated with one or more datasets, it is clear that $Λ$CDM is being challenged by the combination of DESI BAO with other measurements and that dynamical dark energy offers a possible solution.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2106.15656","kind":"article","title":"Measurements of the Hubble Constant: Tensions in Perspective*","authors":["Wendy L. Freedman"],"author_count":1,"year":2021,"published":"2021-09-01","venue":"The Astrophysical Journal","cited_by":576,"doi":"10.3847/1538-4357/ac0e95","arxiv_id":"2106.15656","nct_id":null,"source_url":"https://doi.org/10.3847/1538-4357/ac0e95","archive_url":"https://space-kitty.com/papers/arxiv:2106.15656","updated":"2021-06-29","pmid":null,"pmcid":null,"openalex_id":"W3176418170","pdf_url":"https://iopscience.iop.org/article/10.3847/1538-4357/ac0e95/pdf","abstract":"Measurement of the distances to nearby galaxies have improved rapidly in recent decades. The ever-present challenge is to reduce systematic effects, especially as greater distances are probed, and the uncertainties become larger. In this paper, we combine several recent calibrations of the Tip of the Red Giant Branch (TRGB) method. These calibrations are internally self-consistent at the 1% level. New Gaia Early Data Release 3 (EDR3) data provide an additional consistency check, at a (lower) 5% level of accuracy, a result of the well-documented Gaia angular covariance bias. The updated TRGB calibration applied to a distant sample of Type Ia supernovae from the Carnegie Supernova Project results in a value of the Hubble constant of Ho = 69.8 $\\pm$ 0.6 (stat) $\\pm$ 1.6 (sys) km/s/Mpc. No statistically significant difference is found between the value of Ho based on the TRGB and that determined from measurements of the cosmic microwave background. The TRGB results are also consistent to within 2$σ$ with the SHoES and Spitzer plus HST Key Project Cepheid calibrations. The TRGB results alone do not demand additional new physics beyond the standard Lambda-CDM cosmological model. They have the advantage of simplicity of the underlying physics (the core He flash) and small systematic uncertainties (from extinction, metallicity and crowding). Finally, the strengths and weaknesses of both the TRGB and Cepheids are reviewed, and prospects for addressing the current discrepancy with future Gaia, HST and JWST observations are discussed. Resolving this discrepancy is essential for ascertaining if the claimed tension in Ho between the locally-measured and the CMB-inferred value is physically motivated.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2404.03002","kind":"article","title":"DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations","authors":["DESI Collaboration","A. G. Adame","J. Aguilar","S. Ahlen","S. Alam","D. M. Alexander","M. Alvarez","O. Alves","A. Anand","U. Andrade","E. Armengaud","S. Avila","A. Aviles","H. Awan","B. Bahr-Kalus","S. Bailey","C. Baltay","A. Bault","J. Behera","S. BenZvi","A. Bera","F. Beutler","D. Bianchi","C. Blake","R. Blum"],"author_count":203,"year":2024,"published":"2024-04-03","venue":"JCAP 02 (2025) 021","cited_by":1155,"doi":"10.1088/1475-7516/2025/02/021","arxiv_id":"2404.03002","nct_id":null,"source_url":"https://arxiv.org/abs/2404.03002","archive_url":"https://space-kitty.com/papers/arxiv:2404.03002","updated":"2024-11-04","pmid":null,"pmcid":null,"openalex_id":"W4394029306","pdf_url":"https://arxiv.org/pdf/2404.03002","abstract":"We present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Lyman-$α$ forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI), to be released in the DESI Data Release 1. DESI BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range $0.1<z<4.2$. DESI BAO data alone are consistent with the standard flat $Λ$CDM cosmological model with a matter density $Ω_\\mathrm{m}=0.295\\pm 0.015$. Paired with a BBN prior and the robustly measured acoustic angular scale from the CMB, DESI requires $H_0=(68.52\\pm0.62)$ km/s/Mpc. In conjunction with CMB anisotropies from Planck and CMB lensing data from Planck and ACT, we find $Ω_\\mathrm{m}=0.307\\pm 0.005$ and $H_0=(67.97\\pm0.38)$ km/s/Mpc. Extending the baseline model with a constant dark energy equation of state parameter $w$, DESI BAO alone require $w=-0.99^{+0.15}_{-0.13}$. In models with a time-varying dark energy equation of state parametrized by $w_0$ and $w_a$, combinations of DESI with CMB or with SN~Ia individually prefer $w_0>-1$ and $w_a<0$. This preference is 2.6$σ$ for the DESI+CMB combination, and persists or grows when SN~Ia are added in, giving results discrepant with the $Λ$CDM model at the $2.5σ$, $3.5σ$ or $3.9σ$ levels for the addition of Pantheon+, Union3, or DES-SN5YR datasets respectively. For the flat $Λ$CDM model with the sum of neutrino mass $\\sum m_ν$ free, combining the DESI and CMB data yields an upper limit $\\sum m_ν< 0.072$ $(0.113)$ eV at 95% confidence for a $\\sum m_ν>0$ $(\\sum m_ν>0.059)$ eV prior. These neutrino-mass constraints are substantially relaxed in models beyond $Λ$CDM. [Abridged.]","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2503.21600","kind":"article","title":"The Impact of the Hubble Tension on the Evidence for Dynamical Dark Energy","authors":["Ye-Huang Pang","Xue Zhang","Qing-Guo Huang"],"author_count":3,"year":2025,"published":"2025-03-27","venue":"Science China Physics Mechanics and Astronomy","cited_by":56,"doi":"10.1007/s11433-025-2713-8","arxiv_id":"2503.21600","nct_id":null,"source_url":"https://arxiv.org/abs/2503.21600","archive_url":"https://space-kitty.com/papers/arxiv:2503.21600","updated":"2025-04-10","pmid":null,"pmcid":null,"openalex_id":"W4411722016","pdf_url":"https://arxiv.org/pdf/2503.21600","abstract":"Recent findings from the Dark Energy Spectroscopic Instrument (DESI) Data Release 2 (DR2) favor a dynamical dark energy characterized by a phantom crossing feature. This result also implies a lower value of the Hubble constant, thereby intensifying the so-called Hubble tension. To alleviate the Hubble tension, we consider the early dark energy and explore its impact on the evidence for dynamical dark energy including the Hubble constant calibrated by the SH0ES collaboration. We find that incorporating SH0ES prior with CMB, DESI DR2 BAO and Pantheon Plus/Union3/DESY5 data reduces the preference to dynamical dark energy to $1.5σ/1.4σ/2.4σ$ level, respectively. Our results suggest a potential tension between the Hubble constant $H_0$ of the SH0ES measurement and the phantom-to-quintessence transition in dark energy favored by DESI DR2 BAO data.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2404.15232","kind":"article","title":"Interacting Dark Energy after DESI Baryon Acoustic Oscillation measurements","authors":["William Giarè","Miguel A. Sabogal","Rafael C. Nunes","Eleonora Di Valentino"],"author_count":4,"year":2024,"published":"2024-04-23","venue":"Physical Review Letters","cited_by":160,"doi":"10.1103/physrevlett.133.251003","arxiv_id":"2404.15232","nct_id":null,"source_url":"https://arxiv.org/abs/2404.15232","archive_url":"https://space-kitty.com/papers/arxiv:2404.15232","updated":"2024-12-19","pmid":null,"pmcid":null,"openalex_id":"W4405526361","pdf_url":"https://arxiv.org/pdf/2404.15232","abstract":"We investigate the implications of the Baryon Acoustic Oscillations measurement released by the Dark Energy Spectroscopic Instrument (DESI) for Interacting Dark Energy (IDE) models characterized by an energy-momentum flow from Dark Matter to Dark Energy. By combining Planck-2018 and DESI data, we observe a preference for interactions, leading to a non-vanishing interaction rate $ξ=-0.32^{+0.18}_{-0.14}$, which results in a present-day expansion rate $H_0=70.8^{+1.4}_{-1.7}$ km/s/Mpc, reducing the tension with the value provided by the SH0ES collaboration to less than $\\sim 1.3 σ$. The preference for interactions remains robust when including measurements of the expansion rate $H(z)$ obtained from the relative ages of massive, early-time, and passively-evolving galaxies, as well as when considering distance moduli measurements from Type-Ia Supernovae sourced from the Pantheon-plus catalog using the SH0ES Cepheid host distances as calibrators. Overall, the IDE framework provides an equally good, or better, explanation of both high- and low-redshift background observations compared to $Λ$CDM, while also yielding higher $H_0$ values that align more closely with the local distance ladder estimates. However, a limitation of the IDE model is that it predicts lower $Ω_{m}$ and higher $σ_{8}$ values, which may not be fully consistent with large-scale structure data at the perturbation level.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO","hep-ph"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2008.11284","kind":"article","title":"Snowmass2021 - Letter of interest cosmology intertwined II: The hubble constant tension","authors":["Eleonora Di Valentino","Luis A. Anchordoqui","Özgür Akarsu","Yacine Ali-Haïmoud","Luca Amendola","Nikki Arendse","Marika Asgari","M. Ballardini","Spyros Basilakos","E. S. Battistelli","Micol Benetti","Simon Birrer","François R. Bouchet","Marco Bruni","Erminia Calabrese","David Camarena","Salvatore Capozzıello","Angela Chen","Jens Chluba","Anton Chudaykin","Eoin Ó Colgáin","Francis-Yan Cyr-Racine","P. de Bernardis","Javier de Cruz Pérez","Jacques Delabrouille"],"author_count":93,"year":2021,"published":"2021-05-12","venue":"Astroparticle Physics","cited_by":513,"doi":"10.1016/j.astropartphys.2021.102605","arxiv_id":"2008.11284","nct_id":null,"source_url":"https://doi.org/10.1016/j.astropartphys.2021.102605","archive_url":"https://space-kitty.com/papers/arxiv:2008.11284","updated":"2020-10-13","pmid":null,"pmcid":null,"openalex_id":"W3080176159","pdf_url":"https://www.sciencedirect.com/science/article/pii/S0927650521000499","abstract":"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.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1806.09718","kind":"article","title":"On the cosmological implications of the string Swampland","authors":["Prateek Agrawal","Georges Obied","Paul Joseph Steinhardt","Cumrun Vafa"],"author_count":4,"year":2018,"published":"2018-08-06","venue":"Physics Letters B","cited_by":553,"doi":"10.1016/j.physletb.2018.07.040","arxiv_id":"1806.09718","nct_id":null,"source_url":"https://doi.org/10.1016/j.physletb.2018.07.040","archive_url":"https://space-kitty.com/papers/arxiv:1806.09718","updated":"2018-07-19","pmid":null,"pmcid":null,"openalex_id":"W2810921023","pdf_url":"https://arxiv.org/pdf/1806.09718","abstract":"We study constraints imposed by two proposed string Swampland criteria on cosmology. These criteria involve an upper bound on the range traversed by scalar fields as well as a lower bound on $|\\nabla_φ V|/V$ when $V >0$. We find that inflationary models are generically in tension with these two criteria. Applying these same criteria to dark energy in the present epoch, we find that specific quintessence models can satisfy these bounds and, at the same time, satisfy current observational constraints. Assuming the two Swampland criteria are valid, we argue that the universe will undergo a phase transition within a few Hubble times. These criteria sharpen the motivation for future measurements of the tensor-to-scalar ratio $r$ and the dark energy equation of state $w$, and for tests of the equivalence principle for dark matter.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":"cc-by","is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1907.07569","kind":"article","title":"New physics in light of the H 0 tension: An alternative view","authors":["Sunny Vagnozzi"],"author_count":1,"year":2020,"published":"2020-07-10","venue":"Physical review. D/Physical review. D.","cited_by":516,"doi":"10.1103/physrevd.102.023518","arxiv_id":"1907.07569","nct_id":null,"source_url":"https://doi.org/10.1103/physrevd.102.023518","archive_url":"https://space-kitty.com/papers/arxiv:1907.07569","updated":"2020-06-26","pmid":null,"pmcid":null,"openalex_id":"W2958670513","pdf_url":"https://arxiv.org/pdf/1907.07569","abstract":"The strong discrepancy between local and inverse distance ladder estimates of the Hubble constant $H_0$ could be pointing towards new physics beyond $Λ$CDM. Several attempts to address this tension through new physics rely on extended models, featuring extra free parameters beyond the 6 $Λ$CDM parameters. However, marginalizing over extra parameters has the effect of broadening the uncertainties on the inferred parameters, and it is often the case that within these models the $H_0$ tension is addressed due to larger uncertainties rather than a genuine shift in the central value of $H_0$. What happens if a physical theory is able to fix the extra parameters to a specific set of non-standard values? The degrees of freedom of the model are reduced with respect to the standard case where the extra parameters are free to vary. Focusing on the dark energy equation of state $w$ and the effective number of relativistic species $N_{\\rm eff}$, I find that physical theories able to fix $w \\approx -1.3$ or $N_{\\rm eff} \\approx 3.95$ would lead to an estimate of $H_0$ from CMB, BAO, and SNeIa data in perfect agreement with the local distance ladder estimate, without broadening its uncertainty. These two non-standard models are, from a model-selection perspective, strongly disfavoured with respect to $Λ$CDM. However, models that predict $N_{\\rm eff} \\approx 3.45$ would be able to bring the tension down to $1.5σ$ while only being weakly disfavored with respect to $Λ$CDM, whereas models that predict $w \\approx -1.1$ would be able to bring the tension down to $2σ$ (at the cost of the preference for $Λ$CDM being definite). Finally, I estimate dimensionless multipliers relating variations in $H_0$ to variations in $w$ and $N_{\\rm eff}$, which can be used to repeat the analysis of this paper in light of future more precise local distance ladder estimates of $H_0$.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1801.01120","kind":"article","title":"New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant","authors":["Adam G. Riess","Stefano Casertano","Wenlong Yuan","Lucas M. Macri","Jay Anderson","John W. MacKenty","J. Bradley Bowers","K. I. Clubb","A. V. Filippenko","D. O. Jones","Brad E. Tucker"],"author_count":11,"year":2018,"published":"2018-03-10","venue":"The Astrophysical Journal","cited_by":544,"doi":"10.3847/1538-4357/aaadb7","arxiv_id":"1801.01120","nct_id":null,"source_url":"https://doi.org/10.3847/1538-4357/aaadb7","archive_url":"https://space-kitty.com/papers/arxiv:1801.01120","updated":"2018-02-09","pmid":null,"pmcid":null,"openalex_id":"W2782530178","pdf_url":"https://arxiv.org/pdf/1801.01120","abstract":"We present new parallax measurements of 7 long-period (> 10 days) Milky Way Cepheids (SS CMa, XY Car, VY Car, VX Per, WZ Sgr, X Pup and S Vul) using astrometry from spatial scanning of WFC3 on HST. Observations were obtained at 6 month intervals over 4 years. The distances are 1.7--3.6 kpc with a mean precision of 45 microarcseconds and a best of 29 microarcseconds (SNR = 14). The accuracy of the parallaxes is demonstrated through independent analyses of >100 reference stars. This raises to 10 the number of long-period Cepheids with significant parallax measurements, 8 obtained from this program. We also present high-precision F555W, F814W, and F160W magnitudes of these Cepheids, allowing a direct, zeropoint-independent comparison to >1800 extragalactic Cepheids in the hosts of 19 SNeIa. This sample addresses two outstanding systematic uncertainties affecting prior comparisons of Milky Way and extragalactic Cepheids used to calibrate H_0: their dissimilarity of periods and photometric systems. Comparing the new parallaxes to their predicted values derived from reversing the distance ladder gives a ratio (or independent scale for H_0) of 1.037+/-0.036, consistent with no change and inconsistent at the 3.5 sigma level with a ratio of 0.91 needed to match the value predicted by Planck+LCDM. Using these data instead to augment the Riess et al. (2016) measurement of H_0 improves the precision to 2.3%, yielding 73.48+/-1.66 km/s/Mpc, and tension with Planck+LCDM increases to 3.7 sigma. The future combination of Gaia parallaxes and HST spatial scanning photometry of 50 Milky Way Cepheids can support a < 1% calibration of H_0.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Stellar, planetary, and galactic studies"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1906.11628","kind":"article","title":"Baryon Acoustic Oscillations and the Hubble Constant: Past, Present and Future","authors":["Andrei Cuceu","James Farr","Pablo Lemos","Andreu Font-Ribera"],"author_count":4,"year":2019,"published":"2019-06-27","venue":"JCAP10(2019)044","cited_by":205,"doi":"10.1088/1475-7516/2019/10/044","arxiv_id":"1906.11628","nct_id":null,"source_url":"https://arxiv.org/abs/1906.11628","archive_url":"https://space-kitty.com/papers/arxiv:1906.11628","updated":"2020-01-23","pmid":null,"pmcid":null,"openalex_id":"W2954834825","pdf_url":"https://arxiv.org/pdf/1906.11628","abstract":"We investigate constraints on the Hubble constant ($H_0$) using Baryon Acoustic Oscillations (BAO) and baryon density measurements from Big Bang Nucleosynthesis (BBN). We start by investigating the tension between galaxy BAO measurements and those using the Lyman-$α$ forest, within a Bayesian framework. Using the latest results from eBOSS DR14 we find that the probability of this tension being statistical is $\\simeq6.3\\%$ assuming flat $Λ$CDM. We measure $H_0 = 67.6\\pm1.1$ km s$^{-1}$ Mpc$^{-1}$, with a weak dependence on the BBN prior used, in agreement with results from Planck Cosmic Microwave Background (CMB) results and in strong tension with distance ladder results. Finally, we forecast the future of BAO $+$ BBN measurements of $H_0$, using the Dark Energy Spectroscopic Instrument (DESI). We find that the choice of BBN prior will have a significant impact when considering future BAO measurements from DESI.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv+openalex","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2504.06118","kind":"article","title":"Dynamical Dark Energy in light of the DESI DR2 Baryonic Acoustic Oscillations Measurements","authors":["Gan Gu","Xiaoma Wang","Yuting Wang","Gong-Bo Zhao","Levon Pogosian","Kazuya Koyama","John A. Peacock","Zheng Cai","Jorge L. Cervantes-Cota","Mustapha Ishak","Arman Shafieloo","Ruiyang Zhao","Steven Ahlen","Davide Bianchi","David Brooks","Todd Claybaugh","Shaun Cole","Axel de la Macorra","Arnaud de Mattia","Peter Doel","Simone Ferraro","Jaime E. Forero-Romero","Enrique Gaztañaga","Satya Gontcho A Gontcho","Gaston Gutierrez"],"author_count":60,"year":2025,"published":"2025-04-08","venue":"Nature Astronomy (2025) with Open Access available at https://www.nature.com/articles/s41550-025-02669-6","cited_by":71,"doi":"10.1038/s41550-025-02669-6","arxiv_id":"2504.06118","nct_id":null,"source_url":"https://arxiv.org/abs/2504.06118","archive_url":"https://space-kitty.com/papers/arxiv:2504.06118","updated":"2025-09-01","pmid":null,"pmcid":null,"openalex_id":"W4414451193","pdf_url":"https://arxiv.org/pdf/2504.06118","abstract":"Understanding whether cosmic acceleration arises from a cosmological constant or a dynamical component is a central goal of cosmology, and the Dark Energy Spectroscopic Instrument (DESI) enables stringent tests with high-precision distance measurements. We analyze baryon acoustic oscillation (BAO) measurements from DESI Data Release 1 (DR1) and Data Release 2 (DR2), combined with Type Ia supernovae and a cosmic microwave background (CMB) distance prior. With the larger statistical power and wider redshift coverage of DR2, the preference for dynamical dark energy does not diminish relative to DR1. Using both a shape-function reconstruction and non-parametric approaches with a Horndeski-motivated correlation prior, we find that the dark-energy equation of state $w(z)$ varies with redshift. BAO data alone yield modest constraints, but in combination with independent supernova compilations and the CMB prior they strengthen the evidence for dynamics. Bayesian model comparison shows moderate support for departures from $Λ$CDM when multiple degrees of freedom in $w(z)$ are allowed, corresponding to $\\approx3σ$ tension with $Λ$CDM (and higher for some data sets). Despite methodological differences, our results are consistent with companion DESI papers, underscoring the complementarity of approaches. Possible systematics remain under study; forthcoming DESI, \\emph{Euclid}, and next-generation CMB data will provide decisive tests.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:1701.08165","kind":"article","title":"Dynamical dark energy in light of the latest observations","authors":["Gong‐Bo Zhao","Marco Raveri","Levon Pogosian","Yuting Wang","Robert Crittenden","Will J. Handley","Will J. Percival","Florian Beutler","J. Brinkmann","Chia-Hsun Chuang","Antonio J. Cuesta","Daniel J. Eisenstein","Francisco-Shu Kitaura","Kazuya Koyama","Benjamin L’Huillier","Robert C. Nichol","Matthew M. Pieri","Sergio A. Rodríguez-Torres","Ashley J. Ross","Graziano Rossi","Ariel G. Sánchez","Arman Shafieloo","Jeremy L. Tinker","Rita Tojeiro","Jose Alberto Vazquez"],"author_count":26,"year":2017,"published":"2017-08-25","venue":"Nature Astronomy","cited_by":491,"doi":"10.1038/s41550-017-0216-z","arxiv_id":"1701.08165","nct_id":null,"source_url":"https://doi.org/10.1038/s41550-017-0216-z","archive_url":"https://space-kitty.com/papers/arxiv:1701.08165","updated":"2017-07-13","pmid":null,"pmcid":null,"openalex_id":"W2734629623","pdf_url":"https://arxiv.org/pdf/1701.08165","abstract":"A flat Friedman-Roberson-Walker universe dominated by a cosmological constant ($Λ$) and cold dark matter (CDM) has been the working model preferred by cosmologists since the discovery of cosmic acceleration. However, tensions of various degrees of significance are known to be present among existing datasets within the $Λ$CDM framework. In particular, the Lyman-$α$ forest measurement of the Baryon Acoustic Oscillations (BAO) by the Baryon Oscillation Spectroscopic Survey (BOSS) prefers a smaller value of the matter density fraction $Ω_{\\rm M}$ compared to the value preferred by cosmic microwave background (CMB). Also, the recently measured value of the Hubble constant, $H_0=73.24\\pm1.74 \\ {\\rm km}\\ {\\rm s}^{-1} \\ {\\rm Mpc}^{-1}$, is $3.4σ$ higher than $66.93\\pm0.62 \\ {\\rm km}\\ {\\rm s}^{-1} \\ {\\rm Mpc}^{-1}$ inferred from the Planck CMB data. In this work, we investigate if these tensions can be interpreted as evidence for a non-constant dynamical dark energy (DE). Using the Kullback-Leibler (KL) divergence to quantify the tension between datasets, we find that the tensions are relieved by an evolving DE, with the dynamical DE model preferred at a $3.5σ$ significance level based on the improvement in the fit alone. While, at present, the Bayesian evidence for the dynamical DE is insufficient to favour it over $Λ$CDM, we show that, if the current best fit DE happened to be the true model, it would be decisively detected by the upcoming DESI survey.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":true,"retracted":false,"peer_reviewed":null,"categories":["Cosmology and Gravitation Theories"],"details":null,"provenance":"openalex+arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."},{"id":"arxiv:2504.15274","kind":"article","title":"Is Dynamical Dark Energy Necessary? DESI BAO and Modified Recombination","authors":["Seyed Hamidreza Mirpoorian","Karsten Jedamzik","Levon Pogosian"],"author_count":3,"year":2025,"published":"2025-04-21","venue":"JCAP 12 (2025) 050","cited_by":28,"doi":"10.1088/1475-7516/2025/12/050","arxiv_id":"2504.15274","nct_id":null,"source_url":"https://arxiv.org/abs/2504.15274","archive_url":"https://space-kitty.com/papers/arxiv:2504.15274","updated":"2025-12-23","pmid":null,"pmcid":null,"openalex_id":"W4414565520","pdf_url":"https://arxiv.org/pdf/2504.15274","abstract":"Recent measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) exhibit a mild-to-moderate tension with cosmic microwave background (CMB) and Type Ia supernova (SN) observations when interpreted within the $Λ$CDM framework. This discrepancy has been cited as evidence for dynamical dark energy (DDE). Given the profound implications of DDE for fundamental physics, we explore whether the tension can instead be resolved by modifying the physics of recombination. We find that a phenomenological model of modified recombination can effectively reconcile the BAO and CMB datasets and, unlike DDE, also predicts a higher Hubble constant $H_0$, thereby partially alleviating the Hubble tension. A global fit to BAO, CMB, and calibrated SN data favors modified recombination over DDE.","abstract_license":"CC0-1.0 (arXiv descriptive metadata)","license":null,"is_open_access":false,"retracted":false,"peer_reviewed":null,"categories":["astro-ph.CO"],"details":null,"provenance":"arxiv","attribution":"Abstract: arXiv descriptive metadata (CC0). Thank you to arXiv for use of its open access interoperability. This service was not reviewed or approved by, nor does it necessarily express or reflect the policies or opinions of, arXiv."}],"next":"https://space-kitty.com/api/v1/topics/dark-energy-hubble-tension/papers?sort=top&limit=25&offset=25"}