New DESI Data Shifts the Local Value of the Hubble Constant ✛ ✦
Context
Since Edwin Hubble discovered the universe's expansion, the Hubble constant has become a key number in cosmology. Its exact value, however, remains contentious: the discrepancy between local measurements and inferences from the cosmic microwave background (discovered by Arno Penzias), which carries the imprint of the first moments after the Big Bang, is known as the Hubble tension. It was traditionally assumed that local measurements are insensitive to the details of background cosmology, but growing precision (approaches developed by Adam Riess and others) is forcing a rethink of this assumption. New expansion data from spectroscopy of millions of galaxies by the DESI instrument, pointing to the evolution of dark energy, could substantially alter the picture.
Methods
The authors used data from the Hubble Distance Network (H0DN)—a combination of local distance measurements up to redshifts z ~ 0.1—along with open-source code to extract H0. To assess the impact of the cosmological model, they varied the dark energy parameters: in wCDM and w0wa models, where w is the equation-of-state parameter and wa its evolution. The matter density ΩM includes dark matter and ordinary matter. Using Markov chains from a joint analysis of DESI DR2 BAO, CMB data, and type Ia supernovae, they weighted H0 values according to model likelihoods.
Results
With a fixed ΛCDM and matter density ΩM=0.3, the local H0 = 73.50 km/s/Mpc. Varying ΩM within reasonable limits changes H0 by only ±0.29 km/s/Mpc, but more significant shifts occur when dark energy evolves. In the wCDM model with w far from -1, H0 can drop by 2.7 km/s/Mpc. In the DESI-preferred w0wa model with hints of w0 = -1 - wa/3, the H0 shift can reach 2.5 km/s/Mpc. A joint analysis with CMB and SNIa narrows the allowed range: for DESI+CMB+SNIa, H0 = 73.03 ± 0.81(stat.) ± 0.11(model) km/s/Mpc, which is 0.5 km/s/Mpc lower than the baseline; for DESI+CMB, the reduction is 1.1 ± 0.38 km/s/Mpc. Thus, accounting for possible dark energy evolution lowers the local H0 value.
Implications
It is shown that changes in the background cosmology at low redshifts can significantly impact local measurements of the Hubble constant—an effect previously overlooked. This not only adds systematic uncertainty to direct measurements but also demonstrates that the Hubble tension could be partially alleviated by modifications to the late universe, not just the early one. DESI's results underline that the standard ΛCDM model of expansion may be incomplete.
Future development
If the DESI data hold up, all local H0 measurements will need to be re-evaluated taking into account dynamic dark energy. Future surveys like Euclid and Roman will provide more precise BAO and supernova data, allowing tighter constraints on the w0wa model. Moreover, there will be a need to study physically motivated dark energy models, such as freezing scalar fields, rather than just phenomenological parameterizations.
Impact
This research will impact the field of cosmological standard rulers, the calibration of local distances via supernovae and Cepheids, as well as the interpretation of the cosmic microwave background.
Next steps
Next steps include reanalyzing all local distance datasets within w0wa models, and developing methods for jointly accounting for cosmological uncertainties when measuring H0.
Key open problems
This work is directly linked to the problem of the Hubble tension—the mismatch between H0 values from the early and late universe—and to the mystery of dark energy's nature, especially its possible evolution over time.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The authors used data from the Hubble Distance Network (H0DN) and open-source code to extract the local value of the Hubble constant H0, varying dark energy cosmological models (wCDM and w0wa) and matter density. They weighted H0 values according to model probabilities obtained from a joint analysis of DESI DR2 BAO, CMB, and Type Ia supernovae. They showed that accounting for dark energy evolution can reduce the local H0 by up to 2.7 km/s/Mpc, easing the Hubble tension.
Where its strength is
This work demonstrates that local H0 measurements are not completely independent of background cosmology and quantitatively estimates a model systematic that has often been ignored. It opens the possibility of reconciling local and global H0 values through modifications of the late Universe.
Where it could go next
- It might be interesting to compare the obtained model shifts in H0 with alternative methods of measuring the expansion rate, e.g., using gravitational waves as standard sirens, which would test the independence of the effect from the local distance ladder.based on: Gravitational waves measure the expansion rate of the universe arXiv:2605.27227
- There is a nearby work where dark energy with a changing sign of the equation of state is considered as a way to resolve the Hubble tension; it might be worth exploring how such exotic evolution would affect the local H0 within your approach.based on: The Breath of the Universe: How Dark Energy's Sign Change Eases the Tension arXiv:2607.05044
- In the archive, there is an analysis where two independent cosmological observables (e.g., BAO and supernovae) are used to test model consistency; your probability-weighting method could be extended to include additional data to refine the allowed H0 shifts.based on: Cosmic Detective: Two Independent Clues Against the Main Cosmological Debate arXiv:2606.03634v1
Worth trying
- Test whether the magnitude of the model shift in H0 persists when using alternative datasets to constrain dark energy parameters, e.g., DESI BAO alone without CMB.
- Investigate how the local H0 changes in models with interacting dark matter and dark energy, which could also affect late-time evolution.
- Apply the method to future DESI data with larger statistics to see if the statistical uncertainty shrinks and the model shift becomes more significant.
Why this may matter
If local H0 measurements are indeed sensitive to the dark energy model, this changes the interpretation of the Hubble tension and underscores the need for joint analysis of local and global data within extended cosmologies.
Nearby works in our archive
- Dark Matter Decays, the Universe Smooths Outsimilarity 0.67
- Gravitational waves measure the expansion rate of the universesimilarity 0.66
- A Dark Deal: How the Universe Reconciles Its Clockssimilarity 0.66
- Cosmic Detective: Two Independent Clues Against the Main Cosmological Debatesimilarity 0.66
- The Cosmic Tuning Fork: Why the Universe Plays Two Different Notessimilarity 0.65
- Bubble in a Sea of Dark Energysimilarity 0.65
- The Breath of the Universe: How Dark Energy's Sign Change Eases the Tensionsimilarity 0.64
The closest work in the archive sits at 0.67 by meaning — the usual level for our corpus.
Original abstract
as written by the authors arXiv:2606.05358v1
Measurements of baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) have revealed evidence for dark energy that evolves. If local distance measurements are analyzed with the $$w_0w_a$$ models preferred by the DESI measurements, the value for the Hubble constant can be as much as $$2.5\,\mathrm{km\,s^{-1}Mpc^{-1}}$$ smaller than the value obtained assuming $$\Lambda$$CDM. When these $$w_0w_a$$ models are further constrained by cosmic microwave background (CMB) and type Ia supernova (SNIa) data, the downward shift is $$1.1 \pm 0.38\,\mathrm{km\,s^{-1}Mpc^{-1}}$$ (DESI + CMB) and $$0.5 \pm 0.1\,\mathrm{km\,s^{-1}Mpc^{-1}}$$ (DESI + CMB + SNIa). The dependence of local determinations of $$H_0$$ on the background cosmology, combined with the fact that the low-redshift cosmology is not well constrained, is relevant to the Hubble tension.
Over almost a century of measuring the Hubble constant, its value has evolved from the original 500 km/s/Mpc (obtained by Edwin Hubble himself) to today’s 73 with around 1% precision. Yet, the mystery of the Hubble tension remains unsolved.
Key numbers
- Baseline H0 value (ΛCDM): 73.50 km/s/Mpc
- Maximum H0 shift from w0wa model: 2.5 km/s/Mpc
- H0 reduction for DESI+CMB+SNIa: 0.5 km/s/Mpc
- Statistical error of H0DN: ±0.81 km/s/Mpc
- Redshift of local measurements: z ~ 0.1