Implications of Sound Horizon Free H0 Measurements

Implications of the Sound Horizon free H0Measurements for the Hubble Tension Leandros Perivolaropoulos Department of Physics, University of Ioannina, Greece CosmoVerse@Istanbul, 2025

Motivation Two popular approaches to the resolution of the Hubble tension: 1. Modify sound horizon distance calibrator (increases CMB and BAO H0 measurements) 2. Deform H(z)/H0 so that the sound horizon calibrated H(z=0)=H0 increases. Approach 2 has serious challenges: Low z SnIa data calibrated on Cepheids are inconsistent with low z BAO data calibrated on the sound horizon. Thus they can not be simultaneously fit unless one of the two calibrators changes. Approach 1 is more popular (but see Vagnozzi 2023): It assumes however, that all sound horizon free H0 measurements are consistent with each other and with the high H0 value of distance ladder measurements. Q: Is this assumption realized by recent one step H0 measurements?

Mostly Distance Ladder One Step (Direct) Q: What is a more complete list of measurements? What are their statistical properties? Incomplete List

Methods for Measuring H0 Measured in Hubble flow Degeneracy between M (measured at z<0.01) and H0 (fit at z> 0.01). No E(z)= (z)/ 0 dependence. Distance ladder: measuremeasure locally (z<0.01, 40Mpc) using relative distance indicators (eg Cepheids) Fit (assume M is the same in the Hubble flow (z>0.01)) Sound horizon standard ruler: Degeneracy between rs and H0 and E(z). d Depends on b, and CDM One step methods (no sound horizon): Other methods not calibrated with local astrophysics (time delay gravitational lensing, megamasers, gravity waves, cosmic chronometers, teq horizon etc)) H0=?

Main Questions Q1: What are the current distance ladder measurements of H0? Are they consistent with the SH0ES measurement? Q2: What are the currently available one step measurements of H0 independent of sound horizon and distance ladder? Are they consistent with each other? Are they more consistent with the SH0ES measurement or with the sound horizon based measurements?

One Step measurements One step distance methods in Hubble flow (z>0.01, no local calibrator and no sound horizon) Outliers

Distance ladder measurements Distance ladder methods (local calibrators dependent) Distance ladder weighed mean H0: H0=72.8 0.5 km/sec Mpc One Step Measurements (no sound horizon) weighed mean H0: H0=69.0 0.5 km/sec Mpc One Step Measurements remove two outliers H0: H0=68.3 0.5 km/sec Mpc

One step H0 measurements vs Distance Ladder Measurements One step measurements are consistently lower than distance ladder measurements

Comparison of Distribution Functions Inconsistency of probability distribution functions: Kolmogorov Smirnov Test p-value: 0.0001 The probability that the two samples are drawn from the same probability distribution is less than 0.01%

Robustness of Results - Outliers 2/ dof Outliers: TDCOSMO.I and MCP-SH0ES The one step measurements become self consistent and fully consistent with the sound horizon scale measurements if two outliers are removed (TDCOSMO.I is known to suffer from systematics).

Latest One Step Measurements (A last 10-month update) Weighed Mean: H0=70.4 1.2 km/sec Mpc Consistently Lower than Distance Ladder Measurement

Implications H0 measurements that are independent of local astrophysics (non-distance ladder measurements) are consistently lower than distance ladder measurements Theoretical models that are based on modifying the sound horizon scale may have difficulty to simultaneously fit the distance ladder and the one step measurements. Physical or systematic effects on distance ladder calibrators realized through local astrophysics probably play a role in the resolution of the Hubble tension.

The Local Physics Transition hypothesis A fundamental physics transition induces a transition of M (absolute magnitude or luminosity) at z<0.01. Resolves M tension and Hubble tension. Can potentially also resolve growth tension if the transition is connected with weaker gravity at z>zt

Hints for an M transition in SH0ES? Allow (but do not enforce) an M transition at 50Mpc (new degree of freedom approach) Derive i and do not allow any transition (the original SH0ES approach)

Main Points / Conclusion The Hubble tension is a tension between distance ladder measurements and most other measurements of H0. The resolution of the Hubble tension most probably requires a reanalysis of the distance ladder measurements introducing new degrees of freedom for the identification of new physics and/or systematics. A late transition event involving a sudden change of the SnIa intrinsic luminosity occurring less than 150 million years ago (zt<0.01) is a hypothesis that deserves further investigation by reanalyzing the SH0ES data with new degrees of freedom. There are hints in the SH0ES data for such an ultralate physics transition.

Additional Slides

The Hubble Crisis Approaches Distance Ladder H(z) (M calibrator Cepheids at z<0.01 ) Inverse distance ladder + CDM E(z) (rs or req calibrator) How can H(z) derived from late time calibrators (blue point and SnIa calibrated from it) become consistent with H(z) derived from early time calibrators (black line, CMB+BAO)? Change SnIa Intrinsic Luminosity (systematics or physics change at 0<z<0.01). (move blue point down) Change sound horizon scale AND matter equality scale (Early DE transition at trec and more new physics at teq). (shift black line up) One step measurements (no sound horizon)

The Hubble Crisis Approaches One step measurements (no sound horizon) How can H(z) derived from late time calibrators (blue point and SnIa calibrated from it) become consistent with H(z) derived from early time calibrators (black line, CMB+BAO)? Change SnIa Intrinsic Luminosity (systematics or physics change at 0<z<0.1). (move blue point down) Change sound horizon scale AND matter equality scale (Early DE transition at trec and more new physics at teq). (shift black line up) Deform H(z) by eg dynamical dark energy (problems with BAO, growth, M). (distort black line) Tension Problems with BAO data

Hubble Tension Tomography: The problem with H(z) deformation models Planck/ CDM Residual SnIa and BAO distance moduli. The Hubble tension is a calibrator tension and can not be resolved by H(z) deformation. Planck CDM distance residual Sound Horizon Calibration w=-1.2 Pantheon+ CDM distance residual Cepheid Calibration

Postdictions of Early Time Models

The Local Physics Transition hypothesis A fundamental physics transition induces a transition of M (absolute magnitude or luminosity) at z<0.01. Resolves M tension and Hubble tension. Can potentially also resolve growth tension if the transition is connected with weaker gravity at z>zt

Hints for an M transition in SH0ES? Allow (but do not enforce) an M transition at 50Mpc (new degree of freedom approach) Derive i and do not allow any transition (the original SH0ES approach)

Reanalyze the Local SH0ES Calibrator Calibrate Cepheids in anchor galaxies and in SnIa hosts 3492 equations fit for 47 unknown parameters (including M of SnIa) jth Cepheid in ith galaxy Cepheid calibration SnIa calibration m= ( 0)+ ->Hubble flow SnIa Express the system as linear vector transformation The latest SH0ES measurement of H0 : The distance ladder in practice Minimize 2:

Generalizing the baseline SH0ES modeling analysis: New degrees of freedom Allow for a change (transition) of the SH0ES modeling parameters MW, bW, ZW, MB at a given distance Dc (cosmic time tc). For example if MB was allowed to change, the Cepheid modeling would have to change as: The new matrix equation Y=L q would have the same data/constraints Y (labeled with their distance) the same covariance matrix C but different model matrix L and parameter vector q.

Generalized Local Physics Analyses I: Predictions H0(Dc) MB< MB> Spontaneous transition of the best fit value of H0 when a transition at Dc~50Mpc is allowed. 0=(67.3 4.6) km/secMpc Ruchika, Melchiorri, LP 2024 (Shift MWH, fit for MB MB2)

Generalized Local PhysicsAnalyses II: Postdictions Include SH0ES datapoint for MB: 0=(68.2 0.8) km/secMpc

Generalized Local Physics Analyses III Allow for different color parameter between Cepheid hosted SnIa and Hubble flow SnIa Discrepancy between the two values of the color parameter.

Future Directions in Resolving the Huble Tension: Timeline and Roles

Main Points / Conclusion The Hubble tension is a tension between distance ladder measurements and all other measurements of H0. The resolution of the Hubble tension most probably requires a reanalysis of the distance ladder measurements introducing new degrees of freedom for the identification of new physics and/or systematics. A late transition event involving a sudden change of the SnIa intrinsic luminosity occurring less than 150 million years ago (zt<0.01) is a hypothesis that deserves further investigation by reanalyzing the SH0ES data with new degrees of freedom. There are hints in the SH0ES data for such an ultralate physics transition.

Extra Slides

Results of the Generalized Analysis H0(Dc) MB< MB> Spontaneous transition of the best fit value of H0 when a transition at Dc~50Mpc is allowed. 0=(67.3 4.6) km/secMpc Using Inverse distance ladder input 0=(68.2 0.9) km/secMpc

Hints for an M transition in SH0ES? Allow (but do not enforce) an M transition at 50Mpc (new degree of freedom approach) Derive i and do not allow any transition (the original SH0ES approach)

Measuring H0H(z) with standard candles: late time calibrators fit with kinematic expansion (0.01<z<0.1) Fit SnIa Standard Candles for H0 , 0.02<z<0.1: measuremeasure locally (z<0.01, 40Mpc) using relative distance indicators (eg Cepheids) Fit (assume M is the same in the Hubble flow (z>0.01)) Degeneracy between M (measured at z<0.01) and H0 (fit at z> 0.01). No E(z)= (z)/ 0 dependence. H0 measurement using distance ladder: H0 Tension Assumption: Geff(z<0.01)=Geff(z>0.01)

Measuring H0-H(z) with a standard ruler: early time calibrators calculated Sound Horizon at Recombination Standard Ruler (Early Universe): Depends on b, and CDM 1. EDE: Add new fluids to decrease rs. But keep the same E(z). inferred 2. (z) deformation: New dark energy. But keep the same rs. rs=147.6 Mpc from Planck and BBN values of b, and CDM Same with BAO (projected rs on LSS) (zs->zBAO, s-> BAO rs->rd) measured d comoving Degeneracy between rs and H0 and E(z).

Inverse Distance Ladder and the M tension H0 measurement using sound horizon standard ruler Assumptions: P18 CDM E(z), Standard expansion before zrec Calibrate M from rs (Inverse distance ladder) or M transition? M tension. Local! In Hubble flow. M depends on Geff.

The M transition hypothesis A fundamental physics transition induces a transition of M (absolute magnitude or luminosity) at z<0.01. Resolves M tension and Hubble tension. Can potentially also resolve growth tension if the transition is connected with weaker gravity at z>zt

The M transition Model: Fit to the data

Horizon at teq: An independent early time standard ruler hint at with CMB H0 Parameter degeneracies: Measured with Hubble free expansion rate E(z)=H(z)/H0 1100>z>0.01 (CMB, BAO, SnIa): Accurate-no tension here Obtained from CDM E(z) from teq using shape of LSS power spectrum. Measured with ultralate time calibrators (Cepheids, TRGB etc) at z<0.01 (no Hubble flow) Measured from CMB, BBN assuming CDM E(z) before recombination.

Generic Distance Scale In the context of false vacuum decay bubbles of true vacuum form Predicted bubble scale is close to favored scale of transition Scale of True Vacuum Bubbles: Rb~15Mpc Planck mass O(1)

Theoretical Model: Scalar Tensor Theory 8 G ~ 1/F( ) Scalar Tensor Transition: Temporal transition A phase transition (false vacuum decay) would induce a transition in the strength of gravity as well Field rolling in constant potential Spatial transition In the context of false vacuum decay bubbles of true vacuum form

The Hubble tension Q.: What is the feature that distinguishes the two groups of H0 values? Is it cosmic time of measurements? or is it the use of local calibrators (distance ladder)?

The growth tension S8~ 8 0m1/2 Redshift Space Distortions (galactic peculiar velocities) Cluster counts Weak Lensing Could gravity be weaker on cosmological scales compared to local scales (recent times)?

Distance residuals

Cosmic Dipoles Bulk Flows QSO dipole 5 Radio Galaxy dipole 3-5 90- zones

Cosmic Dipoles Radio Galaxy dipole 3-5 QSO dipole 5 Bulk Flows 5

Local measurements One step distance methods in Hubble flow (z>0.01, local calibrator and sound horizon free) Method H0(km/sec Mpc) Arxiv-link First author Cosmic Chronometers Cosmic Chronometers + HII gal. Gravitational Waves + Kilonovae Gravitational Waves + Kilonovae Lensing Time Delays TDCOSMO I 74.2 1.6 Lensing Time Delays TDCOSMO IV 67.4 4 Megamasers Megamasers (SH0ES) SZ effect Gamma ray attenuation Teq standard ruler 66.7 5.3 65.9 3.0 69.6 5.5 67.0 3.6 https://arxiv.org/pdf/2307.09501.pdf https://arxiv.org/pdf/2208.03960.pdf https://arxiv.org/pdf/2205.09145.pdf https://arxiv.org/pdf/2306.12468.pdf https://arxiv.org/pdf/1912.08027.pdf https://arxiv.org/pdf/2007.02941.pdf https://arxiv.org/pdf/1511.08311.pdf https://arxiv.org/pdf/2001.09213.pdf https://arxiv.org/pdf/astro-ph/0306073.pdf Reese https://arxiv.org/pdf/2306.09878.pdf https://arxiv.org/pdf/2204.02984.pdf Moresco Jianchen Zhang etal Bulla etal Sneppen etal Millon etal Birrer etal Gao etal Pesce etal 66.0 6.0 73.9 3.0 61 21 61.9 2.6 64.8 2.4 Dom nguez etal Philcox etal

The Hubble Crisis Approaches Distance Ladder H(z) (M calibrator Cepheids at z<0.01 ) Inverse distance ladder + CDM E(z) (rs or req calibrator) How can H(z) derived from late time calibrators (blue point and SnIa calibrated from it) become consistent with H(z) derived from early time calibrators (black line, CMB+BAO)? Change SnIa Intrinsic Luminosity (systematics or physics change at 0<z<0.01). (move blue point down)

Local measurements Distance ladder methods (local calibrators dependent) Method H0(km/sec Mpc) Arxiv-link First author Tully Fisher + Cepheid + TRGB SBF + Cepheids + TRGB SnII + Cepheids + TRGB Mira calibrators TRGB (SH0ES) Cepheid (SH0ES) 76.0 3.4 73.3 3.1 75.57 15 73.3 4.0 73.22 2.06 73.04 1.04 https://arxiv.org/pdf/2004.14499.pdf https://arxiv.org/pdf/2101.02221.pdf https://arxiv.org/pdf/2305.17243.pdf https://arxiv.org/pdf/1908.10883.pdf https://arxiv.org/pdf/2304.06693.pdf https://arxiv.org/pdf/2112.04510.pdf Kourkchi etal Blakeslee etal Jaeger etal Huang etal Scolnic etal Riess etal Could we be missing something with ALL local calibrators?? Could there be a physics change between local calibrator scales (z<0.01) and Hubble flow scales (z>0.01)?

Why is CDM still our standard model? Inertia due to the several standard model successes (human factor). Lack of SIMPLE alternative model. Too many tensions (tension noise). Comparison with previous standard model changes From Steady State to Big Bang: Data and Simple alternative supported by simple theory (Friedman equations) From sCDM to CDM: Data and Simple Alternative (cosmological constant) Peebles 1984, Efstathiou 1990 and Krauss-Turner 1995 (Universe age, matter power spectrum and peculiar velocities) Q: What is the new simple and generic replacement of CDM that will release most tensions with just 1-2 parameters? For model building we need to understand deeply the data and the origins of the assumptions hidden in the tensions.