Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB

Daniel Stern (JPL); Licia Verde (Princeton); Raul Jimenez (UPenn); Tommaso Treu (Caltech)

REVIEW

Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB

Raul Jimenez (UPenn), Licia Verde (Princeton), Tommaso Treu (Caltech), Daniel Stern (JPL)

Astrophysics · Submitted 27 Feb 2003 · 38 references

Pith's verdict: A genuinely independent w bound and an independent H0 from cosmic chronometry; the headline number is premise-dependent in a way the paper half-admits, and footnote 8 contradicts their own z = 6 result.

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CitationDaniel Stern (JPL), Licia Verde (Princeton), Raul Jimenez (UPenn), Tommaso Treu (Caltech). "Constraints on the equation of state of dark energy and the Hubble constant from stellar ages and the CMB." arXiv:astro-ph/0302560 (2003). https://pith.science/paper/A652VHUA

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Two things here are worth your time: a w bound that shares no data with supernovae, and an H0 from dz/dt. The first is the headline and it mostly holds up; the second is the more durable contribution. The w < -0.8 (68%) comes from fixing the acoustic scale to WMAP's l1 ~ 220 and imposing the Krauss-Chaboyer globular cluster age distribution offset by 0.3 Gyr, then running CMBFAST over wide uniform priors on h, Omega_m and Omega_b h^2. The logic is not new — they cite Caldwell, Hu and Knox for exactly this degeneracy — but the concrete application with a real age likelihood is. The H0 = 69 +/- 12 from the slope of the SDSS LRG age-redshift envelope at z < 0.17 is the piece I would actually cite; it is independent of the distance ladder and lands on the Key Project value. Soft spots, in order of weight. Footnote 8 says the 0.3 Gyr offset uncertainty is negligible next to the cluster age error, but their own z = 6 variant moves the 90% bound from -0.67 to -0.5. That is not negligible, and the footnote should go. The abstract then quotes only the z ~ 17 number, the optimistic end of a premise they never marginalize over. That is the real criticism and it is fair. Second, the zmax = 0.17 cutoff in Section 3.4 is picked because larger values drift and P>=chi2 drops below 0.1; Figure 7 shows the dependence is weak, but choosing a cutoff on fit quality and then quoting the fit is a little circular. Third, the Monte Carlo in Section 3.3 that validates the edge method assumes Omega_m = 0.27, w = -1, h = 0.71 — the cosmology it is meant to test. It is a bias test rather than a recovery test, so it is defensible, but the paper overstates it as recovering w(z) = -1 +/- 0.2. None of this is load-bearing failure. The authors disclose the sparse z > 0.2 sample and the model dependence of the H0 conversion. Send it out; a referee should ask for the formation-redshift marginalization and a decomposition of the H0 error budget.

Referee report

Major objections (4)

[Section 2.2 and abstract:s1] The 0.3 Gyr offset encodes the premise that the oldest clusters formed before reionization at z ~ 17 (Kogut et al. 2003). The manuscript itself reports that relaxing this to formation by z = 6 weakens the 90% bound from w < -0.67 to w < -0.5, yet footnote 8 calls the offset uncertainty negligible compared with the cluster-age error. Those two statements are in tension, and the abstract reports only the z ~ 17 endpoint. Please place an explicit prior on the formation redshift (or on the offset) and propagate it through the same CMBFAST pipeline, reporting the resulting bound; at minimum, the abstract should state that w < -0.8 is conditional on the reionization-era formation premise.
[Section 2.2, direction of the age-offset sensitivity] The text says that with formation by z = 6 the age distribution 'needs to be offset by ≲ 1 Gyr' and the bound weakens to w < -0.5 at 90%. For the age-w degeneracy shown in Fig. 1, a larger t0 should correspond to a more negative w, so a larger offset would be expected to tighten rather than loosen the bound. Please state the direction of the degeneracy explicitly and clarify whether 'offset by ≲ 1 Gyr' means a shift of the distribution or a broadening of it; if it is a broadening, say so, since that would resolve the apparent sign inversion.
[Section 3.4 and Fig. 7] The fit range zmax = 0.17 is chosen because at larger zmax the value of H0 drifts and P>=chi2 falls below 0.1. This is a post-hoc selection on the same data used for the fit, and the quoted H0 = 69 ± 12 depends on it. Please report H0 over a range of zmax with a fixed, physically motivated criterion, and state the error budget: does ±12 include the systematic from the edge definition (Delta ln P = 0.5 for the edge, Delta ln P = 2 for the error), the SPS and metallicity systematics, and the assumed cosmology (Omega_m = 0.27, w = -1) used for the 4% H(zeff) → H0 correction? The claim that the method is 'fully independent' should be softened accordingly.
[Section 3.3 and Fig. 5] The Monte Carlo generates spectra with the same single-burst SPS and the same cosmology (Omega_m = 0.27, w = -1, h = 0.71) that are used in the fit, so the statement 'we recover w(z) = -1 ± 0.2' is a consistency check of the pipeline, not a blind recovery, and it cannot test SPS or metallicity systematics. Please say this explicitly and, if feasible, repeat the simulation with a different input SPS or metallicity distribution to bound that systematic.

Minor objections (10)

[Fig. 1 caption vs Section 2.2] The Fig. 1 caption states 0.05 < Omega_m < 0.4 while Section 2.2 states 0.05 < Omega_m < 0.45; please reconcile the two ranges.
[Fig. 1 and Section 2.2] Fig. 1 fixes Omega_b h^2 = 0.02, whereas Section 2.2 samples 0.01 < Omega_b h^2 < 0.03; please state which value is used in which calculation.
[Section 2.2, Eq. (5)] The analytic form of Eq. (5) is fitted to the Krauss & Chaboyer (2003) distribution, but no goodness of fit is given; please quote it so the reader can judge whether the parametrization reproduces the tails of the age distribution.
[Section 4 vs abstract] The Conclusions say 'We have restricted our analysis to values of w > -1', while the abstract says 'If we further consider that w > -1'; please state explicitly whether the likelihood is truncated at w = -1 and how that affects the interpretation of the quoted 68% interval.
[Section 3.2] The MS1054-0321 spectra have S/N = 8, below the S/N > 9 selection applied to the other samples; please justify their inclusion or note the effect on the envelope.
[Fig. 4 caption] The dotted alternative model is disfavored only under the assumption that the oldest galaxies at all redshifts formed at the same epoch; the text acknowledges this, but the caption should say so as well.
[Section 3.4] The edge and its error are defined by the thresholds Delta ln P = 0.5 and Delta ln P = 2; please justify these choices or show that the resulting t(z) and H0 are insensitive to them.
[Section 3.2] The ages adopted for 53W069 rest in part on Dey et al. (in preparation) and Nolan et al. (in press); please state the age uncertainties used for these two objects and note that one source is unpublished.
[Abstract:s3] An age-redshift trend is expected in any expanding universe; the novel content is the slope of the envelope, so consider rephrasing 'We detect a correlation' to make that distinction clear.
[Presentation] There are several typographical errors, including 'the the 400 lines' in Section 3.2, 'of SDSS LRG sample' in Section 3.3, 'valued derived' in Section 3.4, and 'Je t Propulsion' in the acknowledgments.

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The paper

The paper claims

Using only the ages of the oldest stars and the position of the CMB's first acoustic peak, the authors bound the dark-energy equation of state to $w < -0.8$ at 68% confidence, and separately read a Hubble constant of $69$ from how galaxy st

The reading

The paper asks whether the dark energy that is accelerating the universe behaves like a plain cosmological constant (equation-of-state parameter $w = -1$) or like something else, and it tries to answer using data that share nothing with the supernova Hubble diagram. The lever is a near-degeneracy in flat cosmologies: if you pin the angular scale of the first CMB acoustic peak to the WMAP value ($l_1$ about 220) and independently know the absolute age of the universe, the pair fixes the effective $w$ almost regardless of the matter density or the Hubble constant. Taking the age of the oldest Galactic globular clusters from the Krauss and Chaboyer analysis, plus 0.3 Gyr, the authors conclude $w < -0.8$ at 68% confidence ($w < -0.67$ at 90%), which is consistent with a classical vacuum energy. The second half of the paper turns the same idea into a measurement: the upper envelope of galaxy ages as a function of redshift traces $dz/dt$, hence $H(z)$, and the authors use SDSS luminous red galaxies at $z < 0.2$ to get $H_0 = 69$.

What carries the argument

The engine is the age-peak degeneracy: in a flat universe the age integral $t_0 = H_0^{-1} int_0^infty (1+z)^{-1} [Omega_rad (1+z)^4 + Omega_m (1+z)^3 + Omega_Lambda (1+z)^{3(1+w)}]^{-1/2} dz$ and the acoustic angular scale $theta_A = r_s(a_dec)/d_A(a_dec)$ respond to $w$ in a way that cannot be cancelled by adjusting $Omega_m$ and $h$ simultaneously, so an independent absolute age plus a measured peak position isolates $w$. The second engine is the cosmic chronometer: for a flat universe $H_0^{-1} dz/dt = -(1+z)^{5/2} [Omega_m + Omega_Lambda exp{3 int_0^z w(z')/(1+z') dz'}]^{1/2}$, so the slope of the old envelope of the age-redshift relation is a direct handle on $H(z)$ and hence on $w(z)$, with no need for standard candles.

Extended reading notes

Core claim

Two results, one method. First, the authors combine a published probability distribution for the age of the oldest Galactic globular clusters with the WMAP measurement of the first acoustic peak's multipole, sampling flat models over $0.5 < h < 0.9$, $0.05 < Omega_m < 0.45$ and $0.01 < Omega_b h^2 < 0.03$ with CMBFAST. Because fixing the peak position and the age leaves little room for $w$ to vary, they obtain $w < -0.8$ at 68% confidence and $w < -0.67$ at 90%, tightening to about $w < -0.5$ at 90% if the clusters are only required to have formed by $z = 6$ instead of before reionization at $z$ about 17. Second, they assemble spectra of early-type galaxies from SDSS luminous red galaxies, a field early-type sample, cluster galaxies at $z = 0.83$, and the radio galaxies 53W091 and 53W069, fit single-burst stellar population models, and find that the old envelope of the age-redshift plane is a recognizable, monotonic feature. Binning the $z < 0.2$ SDSS galaxies and locating the edge of the age distribution in each bin yields a slope $dt/dz$, which converts to $H_0 = 69 pm 12$ km/s/Mpc at effective redshift 0.09, independent of distance-ladder methods. The age-redshift envelope is consistent with a flat $Lambda$CDM model with $Omega_m = 0.27$, $h = 0.71$ and $w = -1$, and the authors argue that an extreme alternative, $w(z) = -2$ at $z > 1$ growing to $w = 0$ today, would require local galaxies to have formed their stars several Gyr later than high-redshift ones, which they consider unlikely.

Load-bearing premise

The bound depends on treating the age of the oldest globular clusters plus 0.3 Gyr as the age of the universe, which requires those clusters to have formed before reionization; the authors themselves show the bound weakens to about $w < -0.5$ at 90% confidence if clusters need only have formed by redshift 6.

Editorial extensions

If this is right

A bound on $w$ derived without any Type Ia supernova data provides an independent cross-check on the cosmological-constant interpretation of the accelerating universe.
The same age-peak logic becomes a sharper $w$ measurement as globular cluster ages improve, since the constraint is limited by the age distribution rather than by the CMB peak position.
The age-redshift envelope of early-type galaxies is established as a usable chronometer at $z < 0.2$, giving $H_0 = 69 pm 12$ km/s/Mpc from a method independent of the distance ladder.
Extending the sample of high signal-to-noise spectra of old galaxies beyond $z = 0.2$ would convert the envelope slope into a measurement of $w(z)$ at the few-tens-of-percent level.
Simulations in the paper show that a 10% mass contribution from late star formation does not shift the edge of the age distribution, so the chronometer survives realistic contamination.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

Because the $w$ bound moves from $-0.8$ to roughly $-0.5$ when the globular cluster formation redshift is relaxed from 17 to 6, the two halves of this paper are coupled: better constraints on when clusters formed would tighten the dark-energy number more than better CMB peak measurements would.
The $H_0$ value extracted from the local age gradient sits between the Hubble Key Project value and the lower values from lensing time delays and Sunyaev-Zeldovich work; a future sample large enough to push the edge fit past $z = 0.2$ would test whether that spread is systematic or statistical.
The old-envelope method implicitly assumes that the oldest galaxies at every redshift are drawn from one population with a common formation epoch; a direct spectroscopic confirmation that the most massive high-redshift ellipticals are as old as the local ones would be the cleanest test of that premise.
The paper restricts itself to $w geq -1$ on theoretical grounds; the same age-plus-peak data could in principle be inverted to ask how far below $-1$ the data would still tolerate, which is a question the authors leave open.

Original abstract

We place tight constraints on the redshift-averaged, effective value of the equation of state of dark energy, w, using only the absolute ages of Galactic stars and the observed position of the first peak in the angular power spectrum of the CMB. We find w<-0.8 at the 68% confidence level. If we further consider that w > -1, this finding suggests that within our uncertainties, dark energy is indistinguishable from a classical vacuum energy term. We detect a correlation between the ages of the oldest galaxies and their redshift. This opens up the possibility of measuring w(z) by computing the relative ages of the oldest galaxies in the universe as a function of redshift, dz/dt. We show that this is a realistic possibility by computing dz/dt at z~0 from SDSS galaxies and obtain an independent estimate for the Hubble constant, H_0 = 69 \pm 12 km s-1 Mpc-1. The small number of galaxies considered at z>0.2 does not yield, currently, a precise determination of w(z), but shows that the age--redshift relation is consistent with a Standard LCDM universe with $w=-1$.

The compiled record

The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.

Compiled by classifier-1.13.0 via TypeSafe API, question bank abstract-p1-20260923, 2026-09-23: 1 request, 5,718 input tokens.

What the abstract itself states, as probabilities: claims first 0.05 · states limitation 0.98 · human participants 0.01 · controlled comparison 0.08 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.46 · mentions code or data availability 0.02.

The abstract, sentence by sentence

arXiv listing abstract v1. Results and the main claim are underlined; show every role.

We place tight constraints on the redshift-averaged, effective value of the equation of state of dark energy, w, using only the absolute ages of Galactic stars and the observed position of the first peak in the angular power spectrum of the CMB. We find w<-0.8 at the 68% confidence level. If we further consider that w > -1, this finding suggests that within our uncertainties, dark energy is indistinguishable from a classical vacuum energy term. We detect a correlation between the ages of the oldest galaxies and their redshift. This opens up the possibility of measuring w(z) by computing the relative ages of the oldest galaxies in the universe as a function of redshift, dz/dt. We show that this is a realistic possibility by computing dz/dt at z~0 from SDSS galaxies and obtain an independent estimate for the Hubble constant, H_0 = 69 \pm 12 km s-1 Mpc-1. The small number of galaxies considered at z>0.2 does not yield, currently, a precise determination of w(z), but shows that the age--redshift relation is consistent with a Standard LCDM universe with $w=-1$.

background contribution method result interpretation main claim

What the classifier reports for each sentence. The number is the probability it gave the label.
#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We place tight constraints on the redshift-averaged, effective value of the equation of state of dark energy, w, using only the absolute ages of Galactic stars and the observed position of the first peak in the angular power spectrum of the CMB.	contribution 0.93	0.96	0.24	asserted 1.00
s1	We find w<-0.8 at the 68% confidence level.	result 1.00	0.97	0.65	asserted 1.00
s2	If we further consider that w > -1, this finding suggests that within our uncertainties, dark energy is indistinguishable from a classical vacuum energy term.	interpretation 1.00	0.86	0.31	hedged possibility 1.00
s3	We detect a correlation between the ages of the oldest galaxies and their redshift.	result 0.99	0.92	0.05	asserted 1.00
s4	This opens up the possibility of measuring w(z) by computing the relative ages of the oldest galaxies in the universe as a function of redshift, dz/dt.	interpretation 0.41	0.28	0.07	hedged possibility 0.99
s5	We show that this is a realistic possibility by computing dz/dt at z~0 from SDSS galaxies and obtain an independent estimate for the Hubble constant, H_0 = 69 \pm 12 km s-1 Mpc-1.	result 0.95	0.96	0.12	asserted 1.00
s6	The small number of galaxies considered at z>0.2 does not yield, currently, a precise determination of w(z), but shows that the age--redshift relation is consistent with a Standard LCDM universe with $w=-1$.	limitation 0.95	0.93	0.11	hedged possibility 0.86

What kind of paper the classifier reports this is: empirical study 0.93 · evidence from analysis of existing data 0.99.

What was examined, and what was not

sources read

arXiv listing abstract v1

not examined

full text
figures and tables
references and citing sentences
relations to other papers

levels run

P abstract

not run

S sections
T body sentences
C citations
R cross-paper relations

Every quoted sentence on this record is the authors'. Every label is from Pith's closed vocabulary, with the probability shown beside it. Every number in the measurements table is the authors', checked by code. Record as JSON

Figures

**Figure 1.** — The region of parameter space allowed if we fix

**Figure 2.** — Confidence regions (68 and 90%) for the value of

**Figure 3.** — The top 3 panels show examples of spectra from the SDSS LRG

**Figure 4.** — Top panel: Age–redshift envelope obtained for the galaxies s

**Figure 5.** — Simulated distribution for the age–redshift relation assuming

**Figure 6.** — The binned, low-redshift age–redshift relation, derived fro

**Figure 7.** — The value for H0 derived from

Figures reproduced from arXiv:astro-ph/0302560 by the authors.

References

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astro-ph.CO 2025-10 conditional novelty 5.0 of 10

A cosmic-age-based inverse distance ladder with DESI DR2, DESY5, SGL, CC and GRB data gives H0=71.59±0.94 km/s/Mpc and ΩK=0.001±0.038.
Cosmo-Learn: code for learning cosmology using different methods and mock data
astro-ph.CO 2025-08 conditional novelty 5.0 of 10

An open-source toolkit that simulates late-universe cosmological observations and benchmarks MCMC, genetic algorithms, Gaussian processes, Bayesian ridge regression, and neural networks in one pipeline.
Is Dark Energy an Effective Manifestation of Non-equilibrium Thermodynamics? -- Insights from DESI
astro-ph.CO 2025-07 conditional novelty 5.0 of 10

Two phenomenological dark matter creation rates can reproduce the accelerated expansion of the universe and fit current background data as well as or slightly better than LambdaCDM for some DESI-based data combinations.
Composite Dark Energy and the Cosmological Tensions
astro-ph.CO 2024-12 conditional novelty 5.0 of 10

A composite dark energy with negative-energy phantom matter before z≈1.5 and quintessence afterward improves the fit over ΛCDM by ΔAIC≈60 and resolves both tensions with BAO 2D, but not with BAO 3D.
Implications for the Hubble tension from the ages of the oldest astrophysical objects
astro-ph.CO 2021-05 conditional novelty 5.0 of 10

Ages of 114 old galaxies and quasars up to redshift 8 cap the Hubble constant at 73.2 km/s/Mpc at 95% confidence, about 2.3 sigma below the Cepheid distance-ladder value.
The galaxy power spectrum take on spatial curvature and cosmic concordance
astro-ph.CO 2020-10 conditional novelty 5.0 of 10

Planck plus the BOSS DR12 full-shape galaxy power spectrum gives a curvature parameter of 0.0023 ± 0.0028, flat to sub-percent precision, but only by combining two datasets that disagree at high significance when curv...
Brans-Dicke cosmology with a $\Lambda$- term: a possible solution to $\Lambda$CDM tensions
astro-ph.CO 2020-06 conditional novelty 5.0 of 10

A Brans-Dicke plus Lambda model with two extra parameters fits the joint cosmological data better than GR-Lambda-CDM and pulls both the H0 and sigma8 tensions down to about 1.5 sigma.
Is there an early Universe solution to Hubble tension?
astro-ph.CO 2020-02 conditional novelty 5.0 of 10

Fitting flat LCDM to six redshift bins of low-z data yields a Hubble constant that declines with redshift at 2.1 sigma, an independent echo of the H0LiCOW trend.
$H_0$ from cosmic chronometers and Type Ia supernovae, with Gaussian Processes and the novel Weighted Polynomial Regression method
astro-ph.CO 2018-02 conditional novelty 5.0 of 10

Cosmic chronometers plus Pantheon supernova Hubble rates give H0 = 67.06 +/- 1.68 km/s/Mpc, 2.71 sigma below the local HST measurement, with a new weighted-polynomial method agreeing at 68.90 +/- 1.96.
Cosmic Chronometers: Constraining the Equation of State of Dark Energy. I: H(z) Measurements
astro-ph.CO 2009-07 conditional novelty 5.0 of 10

New Keck spectra of red-envelope galaxies in 24 clusters yield direct expansion-rate measurements H(z) = 97 +/- 62 at z about 0.5 and 90 +/- 40 km/s/Mpc at z about 0.8, which modestly tighten dark-energy and neutrino ...
Late-time cosmological constraints on three holographic dark energy models with DESI DR2 BAO and Type Ia supernovae
physics.gen-ph 2026-07 accept novelty 4.0 of 10

DESI DR2 and late-time data constrain HDE, ADE and RDE, yielding H0≈67–68 km/s/Mpc, c≈1, n≈2.8, γ≈0.54, with none resolving the Hubble tension or decisively beating ΛCDM.
Cosmological Constraints on Minimal Cubic Galileon Models in Teleparallel Gravity
gr-qc 2026-06 unverdicted novelty 4.0 of 10

Observational constraints on teleparallel cubic Galileon cosmologies with quadratic and exponential potentials show viability for late-time acceleration, with the fixed b1 quadratic case competitive under AIC but not BIC.
EFT of Dark Energy with Cosmic Chronometers: Reconstructing Background EFT Functions
astro-ph.CO 2025-12 unverdicted novelty 4.0 of 10

Reconstruction of EFT background functions from cosmic chronometer Hubble data allows model-independent tests of dark energy evolution in scalar-tensor theories.
In search of an interaction in the dark sector through Gaussian Process and ANN approaches
astro-ph.CO 2025-05 conditional novelty 4.0 of 10

Reconstructed dark-sector interaction from CC and Pantheon+ data is consistent with zero for w_DE = -1 but becomes nonzero whenever w_DE is fixed away from -1, in both Gaussian Process and ANN analyses.
Late Time Phenomena in $f(T,\mathcal{T})$ Gravity Framework: Role of $H_0$ Priors
gr-qc 2024-11 conditional novelty 4.0 of 10

An f(T,T) gravity model fitted to Pantheon+, BAO, and cosmic chronometer data yields a range of H0 posteriors that track the input priors, and predicts a growth rate about 9-11% below ΛCDM for two data combinations.
Model-independent reconstruction of the Interacting Dark Energy Kernel: Binned and Gaussian process
astro-ph.CO 2023-05 conditional novelty 4.0 of 10

Flexible, data-driven reconstructions of the dark matter-dark energy interaction kernel show a roughly 1-sigma oscillatory hint and a possible sign change in energy transfer, but Bayesian evidence still favors Lambda-CDM.
Primordial gravitational waves from NANOGrav: a broken power-law approach
astro-ph.CO 2021-11 conditional novelty 4.0 of 10

A broken power-law primordial gravitational-wave spectrum can fit the NANOGrav signal while satisfying CMB, BBN, and LIGO/Virgo bounds, with a blue tilt n_T about 0.97 below a break frequency under 0.2 Hz.
Hubble Sinks In The Low-Redshift Swampland
astro-ph.CO 2020-05 conditional novelty 4.0 of 10

Low-redshift data prefer quintessence models that lower H0 below the ΛCDM value, and a small exponential dark-matter coupling does not reverse this.
Update on Coupled Dark Energy and the $H_0$ tension
astro-ph.CO 2020-04 accept novelty 4.0 of 10

Coupled dark energy with a Peebles-Ratra potential fits current cosmological data marginally better than Lambda-CDM, but the improvement does not survive Bayesian evidence, and the H0 tension is only reduced from 4.8 ...
The model-independent degeneracy-breaking point in cosmological models with interacting Dark Energy and Dark Matter
astro-ph.CO 2019-08 conditional novelty 4.0 of 10

In interacting dark energy models, the interaction term becomes independent of the constant dark energy equation of state at a specific redshift (about z=1.4), giving a point where the interaction can be observed with...
Curvature vs Distances: testing the FLRW cosmology
astro-ph.CO 2014-02 conditional novelty 4.0 of 10

Four independent reconstructions of the Hubble rate and comoving distance from current data are consistent with a constant curvature parameter, but the errors are too large to discriminate FLRW from inhomogeneous models.
Dynamical age of the universe as a constraint on the parametrization of dark energy equation of state
astro-ph 2006-03 conditional novelty 4.0 of 10

Using the CMB-measured cosmic age, the paper rejects most popular time-varying dark energy parameterizations as predicting a universe younger than observed, with only Lee's parameterization surviving.
Arbitrating the $S_8$ discrepancy with growth rate measurements from Redshift-Space Distortions
astro-ph.CO 2021-06 conditional novelty 3.0 of 10

Growth-rate data combined with distance measurements give S8 = 0.762 (+0.030/-0.025), 2.2 sigma below Planck, so the S8 discrepancy is not yet strong evidence for new physics.
Measuring the expansion history of the Universe with cosmic chronometers
astro-ph.CO 2024-12 unverdicted

A review of the cosmic chronometer method: differential ages of massive passive galaxies yield cosmology-independent H(z) measurements, now at about 5% accuracy at z~0.5 and potentially percent-level H0 with future surveys.

How the literature uses it

70 arXiv papers cite this in 87 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 21 sentences without a confident label

Contests it 1 paper

In addition, as noted in the appendix of [ref] , the commonly used value $H(0.09)=69±12$ km/s/Mpc from [ref] actually corresponds to the inferred $H_0$ value in that paper, and should be corrected to $H(0.09)=70.7±12.3$ km/s/Mpc.

Model-independent test of the cosmic distance duality relation with recent observational data · Cosmic Chronometers · contest 0.72

Uses its method or tool 2 papers

For the data points taken from [ref] we follow the calculation of the covariance matrix as shown in [ref] .

The Ages of the Oldest Astrophysical Objects in an Ellipsoidal Universe · CC Hubble data · 0.92
The same information can also be used to derive $H(z)$ [ref] since H(z) = -1/1+z dz/dt,

Two new diagnostics of dark energy · The Acceleration probe · 0.84

Uses its data or values 53 papers

In this study we use the 24 data points on $H(z)$ from CCH in the redshift range $z∈[0.07,1.965]$ reported in [ref] .

Measuring the sound horizon and absolute magnitude of SNIa by maximizing the consistency between low-redshift data sets · Cosmic chronometers · 1.00
We adopt a widely used compilation of 32 CC measurements spanning the redshift range $0.07 ≤z ≤1.97$ [ref] .

Model-independent late-universe measurements of $H_0$ and $\Omega_K$ with the parametrization based on cosmic age-improved inverse distance ladder · Cosmological data · 1.00
* SNeIa: We use the Pantheon+ compilation [ref] , which consists of 1550 Type Ia supernovae covering the redshift range $z = 0.001$ to $z = 2.26$. * BAO: We use high-precision BAO measurements at various redshifts up to $z < 2.36$, including data from BOSS DR14 quasars (eBOSS) [ref] , SDSS DR12 Galaxy Consensus [ref] , Ly-$α$ DR14 cross-correlation [ref] , Ly-$α$ DR14 auto-correlation [ref] , the Six-Degree Field Galaxy Survey (6dFGS) [ref] , and the SDSS Main Galaxy Sample (MGS) [ref] . * Cosmic chronometers: We use 31 cosmic chronometer measurements, which provide direct estimates of the Hubble parameter $H(z)$ from galaxies that evolve slowly [ref] .

Equivalence of Dark Energy Models: A Theoretical and Bayesian Perspective · Bayesian analysis · 0.96

Compares with it 1 paper

An age-redshift envelope emerges from the scatter of the points in Fig. [ref], quite similar to the predictions for the so called “red envelope” in [ref] (their Fig. 5): lower redshift galaxies are older than higher redshift ones.

Cosmic Chronometers with Photometry: a new path to $H(z)$ · Age-redshift relation and the red envelope · 0.97

Cites it as background 3 papers

With a few exceptions [ref] , OAO received less attention with the end of the “age crisis”.

Implications for the Hubble tension from the ages of the oldest astrophysical objects · Introduction · 0.83
We should note here that there have been many articles in the literature using $H(z)$ derived from age of passively evolving galaxies through the cosmic chronometers approach [ref] .

Model-independent test of the FLRW metric, the flatness of the Universe, and non-local measurement of $H_0r_\mathrm{d}$ · Discussion and conclusion · 1.00
As a result, over the last couple of years, modern cosmology has witnessed the appearance of many theoretical models in the context of both dark energy, modified gravity theories, and these models have been confronted with a variety of astronomical probes [ref] .

Evidence of dynamical dark energy in a non-flat universe: current and future observations · Introduction · 0.91

Discussion

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