Tootfinder

Revisiting the equation of state of dark energy from DESI BAO with SNe Ia and CMB
Jie Zheng, Da-Chun Qiang, Zhi-Qiang You, Darshan Kumar
https://arxiv.org/abs/2608.04353 https://arxiv.org/pdf/2608.04353 https://arxiv.org/html/2608.04353
arXiv:2608.04353v1 Announce Type: new
Abstract: The Dark Energy Spectroscopic Instrument (DESI) measurements of baryon acoustic oscillations (BAO) have recently shown a mild preference for dynamical dark energy over the standard $\rm \Lambda$CDM model. In this paper, we analyze the $w_0w_a$CDM model using DESI BAO DR2, Pantheon SNe Ia, and Planck 2018 CMB distance prior data. To examine how different parts of the data affect the apparent deviation from $\rm \Lambda$CDM, we adopt two complementary redshift-cut strategies, dividing the dataset into $zz_{\rm cut}$ subsamples. We find that the most noticeable shifts occur when BAO and SNe Ia data in the redshift range $z\sim0.4$--$0.8$ are included, reaching a significance of about $\sim2\sigma$. Within this framework, the inclusion of higher-redshift measurements progressively weakens this deviation and brings the constraints closer to the $\rm \Lambda$CDM expectation. Moreover, the information criteria show no statistically significant preference between the $w_0w_a$CDM and $\rm \Lambda$CDM models, while the Bayesian information criterion consistently favors the $\rm \Lambda$CDM model. In addition, a parameter-shift consistency test reveals no statistically significant tension between complementary redshift subsamples. Within the DESI BAO DR2, Pantheon , and CMB distance prior framework adopted here, these results do not provide statistically robust evidence favoring the $w_0w_a$CDM model over $\rm \Lambda$CDM. They instead indicate that the apparent parameter shifts under different redshift cuts may be affected by statistical fluctuations and by the limited precision and number of datapoints in the current subsamples. Our analysis provides a complementary redshift-dependent diagnostic for assessing how the inferred cosmological constraints vary under different redshift selections.
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Small-Scale Clustering of Primordial Black Holes: The Little Red Dot Mass Function and the High-Redshift Galaxy Tension
Borui Zhang, Wei-Xiang Feng, Haipeng An
https://arxiv.org/abs/2609.09078 https://arxiv.org/pdf/2609.09078 https://arxiv.org/html/2609.09078
arXiv:2609.09078v1 Announce Type: new
Abstract: Supermassive black holes (SMBHs) in "little red dots" (LRDs) discovered the James Webb Space Telescope (JWST) may result from runaway mergers of primordial black holes (PBHs) in clusters---through long--short mode coupling on small scales in the early Universe. In this framework, we derive the SMBH mass function, together with the compactness and overmassive features of LRDs. We also estimate that the dense gas residing in PBH clusters is consistent with LRD observations. In addition, SMBHs formed from PBH clusters can help accelerate galaxy formation at high redshifts, thus alleviating tension with $\Lambda$CDM cosmology.
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Coupled quintessence from an axion dark sector
Rayff de Souza, Edmund J. Copeland, Jailson Alcaniz
https://arxiv.org/abs/2608.05032 https://arxiv.org/pdf/2608.05032 https://arxiv.org/html/2608.05032
arXiv:2608.05032v1 Announce Type: new
Abstract: Recent observational data arising from the DESI collaboration has hinted at a possible departure from the standard $\Lambda$CDM cosmological model, preferring instead the presence of a dynamical dark energy component. Specifically, the associated equation of state of the dark energy features a crossing into the so-called phantom regime, which is challenging to accommodate in canonical single scalar-field scenarios. However, this behavior can be effectively described by an interacting dark sector, where the specific dark energy equation of state remains above the phantom divide whilst the dark matter component deviates from the standard cold dark matter evolution. In this work, we explore this possibility in the context of an axion dark sector, where both the dark energy and dark matter are represented by two interacting axion-like fields. We show that given the required mass hierarchy for these fields to play such roles, their dynamics can be effectively placed in the coupled quintessence framework, where their motion follows from a sourced continuity equation in the fluid description. In this regime, we perform a statistical analysis of this scenario with current data, finding that a sub-Planckian dark energy axion decay constant stays well within the observational bounds without the need to fine-tune the associated field's initial conditions. We also perform a comparison with $\Lambda$CDM, where we find that the model provides a better fit to the data while staying competitive from a Bayesian perspective.
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Cosmological constraints and standard sirens forecasts for non-dynamical dark energy in Horndeski gravity
Marcello Miranda, Ruchika, Ivan De Martino, Daniele Vernieri, Salvatore Capozziello
https://arxiv.org/abs/2608.04079 https://arxiv.org/pdf/2608.04079 https://arxiv.org/html/2608.04079
arXiv:2608.04079v1 Announce Type: new
Abstract: We investigate an analytically tractable sector of the Extended Cuscuton model, a non-dynamical dark-energy realization within the framework of viable Horndeski gravity. We focus on four benchmark submodels and constrain them with current background probes, namely cosmic chronometers, Type-Ia supernovae, and BAO, while imposing theoretical viability, Lunar Laser Ranging, and Big Bang Nucleosynthesis bounds. We then forecast third-generation bright-standard-siren constraints with Einstein Telescope and Cosmic Explorer networks, considering prompt-emission, afterglow, and kilonova counterparts. Current data already restrict the viable parameter space to small departures from $\Lambda$CDM and do not remove the calibration-driven offset between the CC SN and CC BAO determinations of $H_0$. In principle, future bright sirens substantially sharpen the constraints, especially for kilonova catalogues and extended detector networks. Across the forecast configurations, the relative uncertainty on $H_0$ remains below $13.18\%$ and can reach $0.21\%$ in the most constraining cases, while $\Omega_\Lambda$ is recovered at the percent level in the best cases. These results show that third-generation standard sirens can provide a precise complementary test of non-dynamical dark energy beyond $\Lambda$CDM.
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Crosslisted article(s) found for astro-ph.GA. https://arxiv.org/list/astro-ph.GA/new
[2/3]:
- Shaving the Outskirts of Planetary Systems Probed by Roman via Stellar Flybys
Donald Liveoak, Tim Hallatt, Sarah Millholland
https://arxiv.org/abs/2609.06112 https://mastoxiv.page/@arXiv_astrophEP_bot/117240099000374426
- PERRY: A Human-in-the-Loop GUI for Precision Alignment of MUSE Data
Bazkiaei, Miszalski, van de Sande, Lorente, O'Toole, Sheng
https://arxiv.org/abs/2609.06400 https://mastoxiv.page/@arXiv_astrophIM_bot/117240072263459997
- DustRover: A Python Package for Modelling Dust Extinction Curves (Phase I)
Amir E. Bazkiaei, Tayyaba Zafar, Nuria P. F. Lorente, Anilkumar Mailvaganam, Arihant Raidani
https://arxiv.org/abs/2609.06401 https://mastoxiv.page/@arXiv_astrophIM_bot/117240079505346895
- Chandra X-ray imaging and IC/CMB model for the inner jet of PKS 0637-752
Jaya Maithil, Daniel A. Schwartz, Aneta Siemiginowska, Diana M. Worrall, Preeti Kharb
https://arxiv.org/abs/2609.06587 https://mastoxiv.page/@arXiv_astrophHE_bot/117240161495404904
- Calibration of CNEOS Fireball Velocities and the Robustness of Nominally Hyperbolic Events
Volkan Duran, Abraham Loeb
https://arxiv.org/abs/2609.06745 https://mastoxiv.page/@arXiv_astrophEP_bot/117240133608812317
- Elusive helium stars in the gap between subdwarfs and Wolf-Rayet stars III. Formation of the Gala...
L. R. Yungelson, A. G. Kuranov, A. V. Mishakina
https://arxiv.org/abs/2609.06764 https://mastoxiv.page/@arXiv_astrophSR_bot/117240134556915599
- Little Red Dot Cosmology: A Matter-Era Baryon Acoustic Oscillations Probe of $\Lambda$CDM
Jessica A. Zebrowski, Rohan P. Naidu
https://arxiv.org/abs/2609.06926 https://mastoxiv.page/@arXiv_astrophCO_bot/117240064791330387
- An Eccentric Massive Protobinary Assembled via a Core-merger Parabolic Encounter
Yao Wang, et al.
https://arxiv.org/abs/2609.07390 https://mastoxiv.page/@arXiv_astrophSR_bot/117240144389587963
- Approximating the statistics of a gravitational wave background
Mikel Falxa
https://arxiv.org/abs/2609.07686 https://mastoxiv.page/@arXiv_astrophIM_bot/117240144585484923
- Precise physical and kinematical parameters of massive eclipsing binaries in the Small Magellanic...
M. Kaya, \"O. \c{C}ak{\i}rl{\i}, B. Hoyman, O. \"Ozdarcan, T. Yontan, R. Canbay
https://arxiv.org/abs/2609.07870
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Fractal properties of the cosmic web
Jaan Einasto
https://arxiv.org/abs/2608.04694 https://arxiv.org/pdf/2608.04694 https://arxiv.org/html/2608.04694
arXiv:2608.04694v1 Announce Type: new
Abstract: The cosmic web is one of the most complex systems in nature, consisting of galaxies and clusters of galaxies connected by filaments and walls, and separated by large empty regions known as cosmic voids. The most common method for describing the web is the correlation function and its derivative, the structure function and fractal dimension function. In this paper I review the fractal properties of the cosmic web within the concordance {\Lambda}CDM framework. I describe how the fractal function is derived from the angular and spatial distributions of galaxies and discuss the relations between these approaches.
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Is Dark Matter Really Matter?
Jun-Qian Jiang, Arman Shafieloo
https://arxiv.org/abs/2608.04763 https://arxiv.org/pdf/2608.04763 https://arxiv.org/html/2608.04763
arXiv:2608.04763v1 Announce Type: new
Abstract: In the standard model of cosmology, it is assumed that dark matter is pressureless with equation of state $w=0$ and dark energy has $w=-1$. We test these assumptions jointly using DESI DR2 distance measurements, including the recent Lyman-$\alpha$ full-shape Alcock-Paczynski (AP) information, DES supernovae, and two complementary CMB treatment. When constant $w_{dm}$ and $w_{de}$ are varied together, we find $w_{dm}=0.000968^{ 0.000501}_{-0.000496}$ and $w_{de}=-0.9380^{ 0.0259}_{-0.0262}$ (68%). With an alternative CMB treatment that marginalizes over the lensing spectrum, the corresponding constraints are $w_{dm}=0.000870^{ 0.000408}_{-0.000410}$ and $w_{de}=-0.9353^{ 0.0258}_{-0.0254}$. Both standard $\Lambda$CDM values are disfavored at approximately $2\sigma$ in the joint extension. Neither parameter departs significantly from its standard value when only that parameter is varied. This behavior arises because late-time distances favor $w_{de}>-1$, while maintaining the early-Universe physical matter density requires a compensating positive $w_{dm}$, which changes the mapping to the matter density today. Allowing dynamical dark energy clarify further on complexity of the situation: phantom crossing for dark energy makes $w_{dm}=0$ consistent with the data, whereas a positive $w_{dm}$ preference persists when crossing is forbidden. Interestingly, the Pad'e-$w$ parameterization that provides a flexible description of a class of quintessence models (with no phantom crossing), along with $w_{dm}$ free, is even mildly favored over the phantom-crossing $w_0w_a$ model according to both the best-fit $\chi^2$ and the DIC under both CMB treatments. One can conclude that the apparent preference for phantom crossing may instead reflect deviations in the dark-matter sector rather than dark-energy dynamics alone. [abridged]
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Modified Cosmological Expansion and the JWST CMB Optical Depth Tension in Self Interaction Gravity
Subhadeep Mukherjee, Shashank Shekhar Pandey, A. S. Majumdar
https://arxiv.org/abs/2608.03470 https://arxiv.org/pdf/2608.03470 https://arxiv.org/html/2608.03470
arXiv:2608.03470v1 Announce Type: new
Abstract: Recent James Webb Space Telescope (JWST) observations favor an earlier and more efficient reionization history, leading to Thomson-scattering optical depths larger than those inferred from the cosmic microwave background (CMB). We investigate whether this tension can be alleviated within the framework of self-interaction (SI) gravity by modifying the cosmological expansion history while retaining the standard astrophysical description of reionization. The SI gravity parameters are constrained through a Bayesian MCMC analysis of the Union3 Type Ia supernova and DESI DR2 Baryon Acoustic Oscillations (BAO) data. The resulting expansion history is then used to predict the ionization history and Thomson optical depth. We find that the predicted optical depth decreases from $\tau_{\rm{CMB}}\simeq0.076$ in $\Lambda$CDM to $\tau_{\rm{CMB}}\simeq0.061$, consistent with the Planck PR4 measurement within $1\sigma$, thereby substantially reducing the optical-depth tension.
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Cosmology in the Einstein Telescope era: comparing traditional and simulation-based methods for population inference
Giovanni Antinozzi, Guillermo Franco Abell\'an, Davide Sciotti, Matteo Martinelli
https://arxiv.org/abs/2608.04005 https://arxiv.org/pdf/2608.04005 https://arxiv.org/html/2608.04005
arXiv:2608.04005v1 Announce Type: new
Abstract: The next generation of gravitational wave detectors, such as the Einstein Telescope (ET), will observe orders of magnitude more binary black hole mergers than current facilities. Most of these events will lack an electromagnetic counterpart, also known as dark siren events, yet will still enable percent-level cosmological constraints. However, the likelihood traditionally used in Hierarchical Bayesian Inference (HBI) for population-level analyses becomes computationally prohibitive as the size of dark siren catalogues and population parameters grow. In this work we compare HBI against simulation-based inference (SBI) as a scalable alternative for cosmological population inference in the ET era. Studying a proof-of-concept example of a mock ET inference, we build a catalogue of $O(10^4)$ binary black hole events, then perform inference on the Hubble constant $H_0$ and matter density $\Omega_m$ in a flat $\Lambda$CDM cosmology, using both a hierarchical analytical likelihood and Marginal Neural Ratio Estimation (MNRE). We find excellent agreement between the two approaches, with SBI reproducing the HBI posteriors to high accuracy, while requiring orders of magnitude less computation once the simulation and training cost is amortized. We further demonstrate that SBI extends straightforwardly to a joint cosmology-plus-astrophysics analysis, simultaneously constraining $(H_0,\Omega_m)$ together with the parameters of the star formation rate density, at negligible additional cost compared to the significant increase in complexity such an extension would require within the HBI framework. Our results indicate that SBI is a promising and scalable tool for population inference with third-generation GW detectors.
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