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Physics Astrophysics Cosmology and Nongalactic Astrophysics

astro-ph.CO Watch Cosmology and Nongalactic Astrophysics

Thursday 17 September

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Cosmological Correlators from Resurgence

Yuanzhao Li and Zhong-Zhi Xianyu

Integrating out heavy particles is generally viewed as an irreversible procedure that erases some physical information above the cutoff scale of the resulting effective theory. However, this does not preclude the possibility of recovering the heavy propagating degrees from the low-energy effective theory with appropriate boundary data supplied. A classic example is the recovery of Schwinger pair production from the resummed Euler-Heisenberg effective action. In this work, we perform a similar exercise in a cosmological setting. We show that it is possible to reconstruct the inflationary correlators with massive exchanges, for a discrete heavy spectrum and arbitrary tree topologies, from the low-energy effective theory together with unitarity and Bunch-Davies boundary conditions. The divergent EFT series is resummed in three ways: the boundary differential operators, spectral representation, and Borel resummation, and the exponentially suppressed cosmological collider signals are recovered via analytic continuation. Our construction provides a resurgent relation between the local EFT background and the nonanalytic heavy-particle production, and may also be viewed as an inverse problem for the dispersive bootstrap.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

The axion mass in the post-inflationary scenario in a minimal scaling model

José Correia, Mark Hindmarsh, Joanes Lizarraga et al. (+3 more)

We calculate the dark matter axion mass in the post-inflationary scenario in a minimal model with a set of classical field theory simulations on $12\,288^3$ grids. In the model, the Peccei-Quinn U(1) symmetry is broken by a complex scalar field at a temperature $f_{\rm a} \sim 10^{11}$ GeV, creating a string network. The strings become the boundaries of domain walls at the QCD transition, which draw the strings together and annihilate them. The decay of the strings and domain walls leaves behind axion radiation, with a comoving number density estimated to be $9.48(23)f_{\rm a}^2 H_*$, normalised to unit scale factor when the axion mass is equal to the Hubble rate $H_*$. Using the most commonly quoted lattice results for the topological susceptibility, the dark matter axion mass in this minimal model is $17.46(84)\,\mu\text{eV}$. This corresponds to a symmetry-breaking scale of $3.27(15) \times 10^{11}\, \text{GeV}$, and a haloscope resonant frequency of $4.22(20)\,\text{GHz}$. We argue that field theory simulations of non-minimal models where the strings have a Higgs condensate or gauge flux, and are annihilated by domain walls, will give axion mass predictions below about $40\,\mu\text{eV}$.
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All authors José Correia, Mark Hindmarsh, Joanes Lizarraga, Asier Lopez-Eiguren, Kari Rummukainen, Jon Urrestilla

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Palatini inflationary (non-)attractors: Universal mapping of observables

Christian Dioguardi, Francesco Gianesello and Antonio Racioppi

We study single-field slow-roll inflation in the context of Palatini gravity for the class of non-minimally coupled $\xi$-attractors, i.e.,\ models where the same function $f(\phi)$ fixes both the non-minimal coupling, $1+\xi f(\phi)$, and the inflationary potential, $V(\phi) = M^4 f(\phi)^2$. For an arbitrary $f(\phi)$, the number of $e$-folds is, at leading order, independent of $\xi$. Thanks to this, we provide an immediate mapping between the observables of the non-minimally coupled setup and those of the minimally coupled one. In the strong coupling limit, the tensor-to-scalar ratio is, as usual, suppressed, while the scalar spectral index is shifted towards larger values, with the magnitude of the shift depending only on the tensor-to-scalar ratio associated with the original potential $V(\phi)$.
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Cosmology and Nongalactic Astrophysics

Euclid: Galaxy cluster detection through the weak lensing effect - algorithm assessment and selection

A. Manjón-García, G. Leroy, S. Pires et al. (+164 more)

Weak gravitational lensing offers a powerful way to detect galaxy clusters by directly tracing their total matter content. Its effectiveness increases with the density of background galaxies, a requirement that is now being met by the high sensitivity and wide coverage of current large-area surveys. A prime example is the Euclid telescope, which will map approximately 14 000 deg2 of the sky, measuring the shapes of billions of galaxies and opening a meaningful window for detecting galaxy clusters uniquely through their weak lensing signal. We present the results of nine galaxy cluster detection algorithms in a blind challenge, using 1200 deg2 of Euclid-like weak lensing observations from the DEMNUni-Cov simulations. The performance of these methods was assessed by matching their detections to known synthetic clusters with signal-to-noise ratios greater than 2, satisfying the z-M selection cut, and adopting two different matching procedures. The purpose of the challenge was to identify and improve strategies for galaxy cluster detection via weak lensing for the upcoming Euclid data releases. We pre-selected four methods based on their individual performance and complementarity. Each pre-selected method adopts a distinct approach: AMICO-WL uses an optimal filtering technique, DoG employs Gaussian filtering, O21 relies on aperture-mass filtering, and W234 applies multi-scale wavelet filtering. Together, the results of these methods can be merged to enhance the processing of Euclid data. Individually, these algorithms reach approximately 10% completeness for a mean purity of 90%, while their combination leads to roughly a two-fold improvement in overall performance, exceeding 70% completeness for low-redshift, high-mass clusters. When extrapolating the results of this work to Euclid Data Release 1, we expect to detect approximately 2500 galaxy clusters via weak gravitational lensing.
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All authors A. Manjón-García, G. Leroy, S. Pires, J. M. Diego, C. Giocoli, L. Trobbiani, A. Díaz-Sánchez, M. Maturi, M. Oguri, G. Panebianco, G. W. Pratt, S. Andreon, L. Moscardini, M. Sereno, C. Carbone, A. M. C. Le Brun, M. Lieu, L. Chappuis, B. Altieri, T. Castro, M. Douspis, D. Eckert, S. Farrens, R. Gavazzi, A. H. Gonzalez, L. Ingoglia, E. Jullo, S. Maurogordato, J.-B. Melin, N. Okabe, F. Pacaud, M. Radovich, Z. Sakr, L. Salvati, B. Sartoris, S. A. Stanford, J. E. Taylor, J. Weller, C. Wood, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, V. F. Cardone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, H. Degaudenzi, S. de la Torre, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Escoffier, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, H. Hoekstra, M. S. Holliman, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kunz, H. Kurki-Suonio, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, E. Munari, R. Nakajima, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, C. Rosset, R. Saglia, A. G. Sánchez, D. Sapone, M. Schirmer, P. Schneider, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, Y. Wang, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, J. García-Bellido, J. Martín-Fleitas, V. Scottez, M. Viel

Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det

Mineral Detection of Neutrinos and Dark Matter 2026 Proceedings

Alexey Elykov, Patrick Stengel, Natsue Abe et al. (+81 more)

The fourth "Mineral Detection of Neutrinos and Dark Matter" (MDvDM'26) meeting was held April 14-17, 2026 in Karlsruhe, Germany, hosted by the Institute for Astroparticle Physics (IAP) at Karlsruhe Institute of Technology (KIT). These proceedings detail the contributions that were presented during MDvDM'26, illustrating the unprecedented progress in theoretical, computational and experimental studies towards the realization of the concept of mineral detectors. Mineral detectors represent an emerging particle detection concept that has risen in prominence in recent years due to the advent of modern computational and high-resolution microscopy techniques. Natural and synthetic crystals are capable of retaining microscopic damage features induced by nuclear recoils, which could be then read out with a variety of micrometer and nanometer resolution microscopy techniques. On laboratory time scales mineral detectors could be employed for reactor neutrino monitoring and dark matter detection, with the potential to measure the directions as well as the energies of the induced nuclear recoils. Uniquely, ancient natural crystals (so-called paleo-detectors) that have been recording nuclear recoils over geological timescales could be used for studying astrophysical neutrinos, cosmic rays, dark matter and heavy exotic particles, as well as the variation of their fluxes over our Galaxy's lifetime. In recent years the international MDvDM community has been successfully tackling the challenges associated with realizing the concept of mineral detectors, opening the pathway towards a fully fledged experimental program and potential future discoveries.
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All authors Alexey Elykov, Patrick Stengel, Natsue Abe, Daniel Ang, Lorenzo Apollonio, Levente Balogh, Laura Baudis, Chinmay Bharathulwar, Priyanshu Bhattacharya, Yilda Boukhtouchen, Joseph Bramante, Vincent Breton, Andrew Buchanan, Jens Burkhart, Lorenzo Caccianiga, Andrew Calabrese-Day, Mason Camp, Jordan Chapman, Anson Cook, Reza Ebadi, Denis Erkal, Katherine Freese, Audrey Fung, Shota Futamura, Claudio Galelli, Kevin Gao, Peter W. Graham, Thomas Haddock, Minako Hashiguchi, Alexander Hayes, Adam A. Hecht, Samuel C. Hedges, Shigenobu Hirose, Luisa M. Hötzsch, Patrick Huber, Yohei Igami, Vsevolod Ivanov, Florian Jörg, Ayuki Kamada, Takenori Kato, Yoji Kawamura, Katharina Kehl, Chris Kelso, Holger Kluck, Emilie M. LaVoie-Ingram, Matthew Leybourne, Gavishta H. M. Liyanage, Thalles Lucas, Brenden A. Magill, Paolo Magnani, Jennika McIntosh, Naoki Mizutani, Kohta Murase, Tatsuhiro Naka, Lina Necib, Pranav Parvathaneni, Andre Peterson, Zachary S. C. Picker, Rabeya Rabu, Harikrishnan Ramani, Anupam Ray, Morteza Roostaeinia, Hannah Ross, Issei Saikyo, Lukas Scherne, Maximilian Shen, Aaron Shugar, Joshua Spitz, Kai Sun, Jiashen Tang, Erwin H. Tanin, Dionysios P. Theodosopoulos, Yoichi Usui, Pieter Vermeesch, Aaron Vincent, Ronald Walsworth, Jin-Wei Wang, David Waters, Samuel S. Y. Wong, Audrey Wu, Gregory Wurtz, Wen Yin, Xiuyuan Zhang, Zhexian Zhang

Cosmology and Nongalactic Astrophysics

Predictions on the abundance of primordial black holes: results from the SMILE VLBI milli-lensing sample

Xinyue Jiang, Shuo Cao, Marek Biesiada et al. (+4 more)

Primordial black holes (PBHs) formed in the early universe represent a well-motivated dark matter candidate. However, their abundance in the intermediate-to-high mass range ($10^6$-$10^9\,M_\odot$) remains relatively less constrained. In this mass regime, the corresponding Einstein radii on the milliarcsecond scale make Very Long Baseline Interferometry (VLBI) the most direct observational probe via milli-lensing of compact radio sources. In this paper, we present predictions for the abundance of PBH dark matter ($f_{\rm PBH}$) using the large SMILE sample of $\sim 5000$ flat-spectrum compact radio sources. Under the optimistic observational conditions (with an angular resolution of $1.5\,\mathrm{mas}$, a maximum image separation of $100\,\mathrm{mas}$, and a maximum detectable flux ratio of $40$), assuming that no milli-lensing events are confirmed, we obtain the projected 95% upper limit of $f_{\rm PBH}\lesssim0.12%$ in the intermediate-to-high mass range, which would be approximately an order of magnitude tighter than previous VLBI milli-lensing limits. Broader lognormal mass functions yield correspondingly weaker projected limits. Generalising the optical depth to account for magnification bias and finite-core resolvability changes these projected limits by only about $5$%. Moreover, we show that the predicted limits are highly sensitive to a small number of confirmed events, i.e., even one confirmed milli-lensing event would relax the projected upper limit to $0.20$%, highlighting the critical importance of robust candidate confirmation in the SMILE sample. Finally, under the optimistic baryonic accretion scenario, the PBH mass growth changes the projected limits by $\lesssim 1$% within the VLBI-sensitive mass range, confirming the robustness of our results.
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All authors Xinyue Jiang, Shuo Cao, Marek Biesiada, Xuanni Chen, Yalong Nan, Xinyang Jin, Xuchen Tai

Cosmology and Nongalactic Astrophysics

Constraints on the Pop III Sky Surface Brightness from High-Redshift Caustic Transients in MACS0416

Jakob P. Perivolotis, Pietro Bergamini, Rogier A. Windhorst et al. (+18 more)

Population III (Pop III) stars are hypothetical zero-metallicity stellar structures formed from primordial hydrogen and helium. They are theorized to span a wide mass range, extending to several 100 solar masses, and may have played important roles in nucleosynthesis and reionization. Their expected fluxes are far below JWST NIRCam detection limits, making direct observation unlikely. However, extreme magnification near the caustics of massive foreground galaxy clusters may enable their detection. We search for overlooked high-redshift (7 <= z <= 17) caustic transits in the lensing cluster MACS J0416.1-2403. Using three observations spanning 126 days, we create difference images to identify potential candidates. Critical curves for sources at 7 <= z <= 17, derived from a strong-lensing model, guided visual inspection of three difference-images. No additional transits were found. The longer caustics in our model sweep a larger source-plane area, increasing the probability of detecting an event. Combining this increased statistical sensitivity with deeper imaging, we establish a fainter limit for the unresolved stellar population at z >= 7. From this null result, we constrain the 100 solar mass 2 micron Pop III sky surface brightness to >= 32.8 +/- 0.6 mag arcsec^-2. Modeling the non-detection as a Poisson process gives a posterior mean caustic-transit rate of 0.29 cluster^-1 yr^-1 and a 95 percent upper credible limit of lambda_95 = 0.86 cluster^-1 yr^-1. The inferred rate remains consistent with the adopted fiducial Pop III caustic-transit model and provides an empirical benchmark for future multi-epoch monitoring campaigns. This search exploits the fact that individual stars projected close to source-plane caustics can be briefly magnified far beyond their unlensed fluxes. These constraints provide a direct test of the abundance of luminous Pop III stars at early cosmic times.
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All authors Jakob P. Perivolotis, Pietro Bergamini, Rogier A. Windhorst, Erik Zackrisson, Timothy Carleton, Seth H. Cohen, Jordan C. J. D'Silva, Rachel Honor, Rolf A. Jansen, Anton M. Koekemoer, Rafael Ortiz III, Jake Summers, Dan Coe, Christopher J. Conselice, Jose M. Diego, Brenda Frye, Massimo Ricotti, Gibson B. Bowling, Brent Smith, Christopher N. A. Willmer, Haojing Yan

Cosmology and Nongalactic Astrophysics

Probing submillimeter number counts below the confusion limit: extreme-value statistics of the P(D) distribution and its modulation by gravitational lensing

Kaustuv Basu, Andrea Guerrero and Frank Bertoldi

The shape of the submillimeter galaxy number counts below the confusion limit is a key record of cosmic star formation but is accessible only statistically, through the one-point distribution of map surface brightness, $P(D)$. Classical $P(D)$ analysis compresses the counts into flux-integrated constraints and requires a full instrument forward model. We introduce an extreme-value-theory analysis of the confusion $P(D)$ tail: the peaks-over-threshold formalism, in which exceedances above a threshold $u$ follow a generalized Pareto distribution (GPD). The GPD shape parameter $\xi(u)$ is a flux-resolved, normalization-free readout of the local logarithmic slope of the counts, and its gravitational-lensing modulation $\Delta\xi(u)$ probes their local curvature. We derive analytic relations for both, validate them with end-to-end simulations, and apply the method to Planck 857 GHz maps and the Herschel/SPIRE 350 $\mu$m map of GAMA-09. At Planck's 5' resolution the tail reflects the bright, clustered sky rather than the faint counts, though the background alone excludes the single power-law count model. At SPIRE resolution $\xi$ rises markedly with threshold, consistent with the strongly lensed bright population (a first detection of lensing in a $P(D)$ tail), and the bright-masked map favors the Schechter model. Behind galaxy clusters we set the first calibrated upper limits on $\Delta\xi(u)$. CCAT/FYST should separate the count models directly, but a cluster-lensing detection needs more $10^{15}\,M_\odot$ clusters than the sky contains. The GPD tail statistic thus discriminates the functional form of the counts at fluxes of order the threshold, below the detection limit, invariant to map mean, gain and count normalization, and robust to clustering; lensing supplies a calibrated ruler for count features, whose detection awaits deep, high-resolution surveys of massive clusters.
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Cosmology and Nongalactic Astrophysics

Distinguishing Coupled Dark Matter Dark Energy from Kinematic Phantom Crossing

Samit Ganguly, Koushik Dutta and Goutam Manna

Recent measurements of cosmic expansion have renewed interest in dark-energy scenarios in which the effective equation of state exhibits phantom-like evolution and may cross $w=-1$. Such behavior, however, does not require a fundamental phantom field: in coupled dark-energy-dark-matter~(CDEDM) models, energy exchange between a canonical scalar field and cold dark matter, happens Lagrangian labels, can reproduce the same effective equation of state evolution as that of phenomenological $w_0w_a$CDM model. We show that this microscopic interaction leaves distinctive, testable signatures in structure growth by forming a two-fluid system in which only cold dark matter feels the scalar-mediated fifth force (and an associated drag term), while baryons remain uncoupled. When combined with neutrino-free streaming, this setup generates a characteristic coupling, neutrino-mass degeneracy, whose leading scaling $\sum m_\nu \propto f_c^2 \alpha^2$ follows analytically from the two-fluid growth equations. Using DESI DR2 BAO, CMB distance information, ACT DR6 lensing, redshift-space distortions, and three supernova compilations, we find that this scaling is recovered for both exponential and inverse-power-law potentials. We further show that the dominant contribution to the growth response arises from the coupling-induced modification of the background evolution, with the fifth force enhancing growth and the drag partially counteracting it. Finally, the interaction induces a running dark-matter mass, changing it at recombination by $4.3\%$–$5.5\%$, so CMB distance calculations must account for the evolving dark-matter density. These correlated growth and recombination effects provide a route to distinguish interaction-driven phantom crossing from purely kinematic dark-energy parametrizations.
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Wednesday 16 September

Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

The extreme Disturbed Galaxy Cluster Sample (eDGeS): Spectroscopy and Dynamical Analysis of the eROSITA-Selected Merging Galaxy Cluster Candidate 1eRASS J025859.4-193727

Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno et al. (+7 more)

Addressing open questions such as the effect of galaxy cluster mergers on the evolution of galaxies and the self-interaction cross-section of dark matter requires the construction of a large, diverse sample of disturbed galaxy clusters. One contribution to such a sample is the extreme Disturbed Galaxy Cluster Sample (eDGeS), an ongoing spectroscopic study of massive disturbed and merging galaxy clusters selected from complementary surveys. Here, we present our first results from the eROSITA-selected subsample (eDGeS-eROSITA): a dynamical state analysis for the merging cluster candidate 1eRASS J025859.4-193727. We present the first spectroscopic redshift measurements for 76 galaxies in the direction of the cluster, confirming 51 as cluster members. The cluster displays a line-of-sight velocity dispersion of $\sigma_{\rm{cl}}=808^{+59}_{-66}~\rm{km~s^{-1}}$ and a dynamical mass of $M_{200}=4.47^{+0.94}_{-0.93} \times 10^{14}~M_{\rm{Sun}}$. While the cluster shows no evidence for substructure along the line of sight, the projected distribution of member galaxies reveals three subclusters, only one of which appears associated with the cluster's X-ray contours. Phase-space analysis reveals a large fraction of recently infallen member galaxies. Together, this evidence suggests a cluster merger along the plane of the sky. Assuming that the two most massive subclusters are on outgoing (incoming) trajectories after their first pericentric passage, a two-body Monte Carlo model predicts that the two subclusters collided $0.50^{+0.20}_{-0.22}~\rm{Gyr}$ ($1.24^{+0.96}_{-0.38}~\rm{Gyr}$) ago.
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All authors Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno, Rogério Monteiro-Oliveira, Facundo A. Gómez, Konstantina Boutsia, Esra Bulbul, Guillermo Damke, Amelia Ramirez, Hector Cuevas

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Relativistic Stellar Oscillations from Ultralight Dark Matter

Shanae Oishi, Christopher Reyes and Jeremy Sakstein

Ultra-light dark matter, composed of bosons behaving as classical waves, can resonantly excite stellar oscillations. In this work, we investigate this phenomenon in relativistic stars, showing that $\ell=0$ fluid modes can be excited. We derive a framework for calculating the mode amplitude and apply it to neutron stars to predict the associated surface temperature fluctuations; the resulting signal lies beyond current observational sensitivities. We discuss prospects for extending this approach to other compact objects.
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Cosmology and Nongalactic Astrophysics

Monitoring the power spectrum of magnetic field fluctuations across the simulated intracluster medium

T. Bartalesi, F. Vazza, S. Ettori et al. (+2 more)

Thanks to the current and forthcoming radio interferometers, Faraday rotation measure maps extend out to the outskirts of galaxy clusters. Interpreted through models of the magnetic power spectrum, these maps can provide stringent constraints on the properties of the magnetic field of the intracluster medium (ICM). Our goal is to ascertain how the magnetic power spectrum varies with the environment and dynamics of the ICM in a post-merger galaxy cluster formed in a state-of-the-art non-radiative cosmological magneto-hydrodynamic simulation. We divide the simulated cluster into cubic subboxes with side length 950 kpc and compute the kinetic and magnetic power spectra in each. Starting from a "dynamo-only" functional form proposed in previous works to describe magnetic fluctuations amplified by the small-scale dynamo, we introduce an additional Kolmogorov-like component to account for the contribution of unamplified magnetic field patches. We fit this extended model to the magnetic power spectrum of each subbox individually using a Markov chain Monte Carlo method and examine scatter plots of the inferred parameters versus the local ICM properties evaluated in the corresponding subboxes. The extended model reproduces the magnetic power spectrum data well in most subboxes, whereas the "dynamo-only" model fits these data well only in subboxes not too far from the center. The inferred parameters exhibit substantial subbox-to-subbox variations that correlate significantly with the local ICM density and clumpiness. These correlations suggest that the magnetic power spectrum is closely linked to the local ICM environment, and may help observers in the interpretation of Faraday Rotation data.
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All authors T. Bartalesi, F. Vazza, S. Ettori, C. Nipoti, P. Dominguez-Fernandez

Cosmology and Nongalactic Astrophysics

A Global Overview of Starobinsky Inflation beyond slow-roll with CMB-BAO data

Tarun, Tanmoy Modak and Björn Malte Schäfer

We perform a global analysis of the Starobinsky inflation using most recent CMB data from ACT and SPT together with DESI BAO measurements. By directly solving the equations of motion, we find relatively stronger constraints on the model parameters than those obtained under the slow-roll approximation from the baseline $\Lambda$CDM parameters $A_s$ and $n_s$. We translate these constraints into limits on the reheating temperature. We also discuss the dependence of the prior choices of the model parameters. Further, the correlation of the model parameters with the BAO parameter $r_d h$ is also studied. We further investigate the impact of the global analysis on the dimension-six $R^3$ modified Starobinsky model, deriving constraints on its additional parameters. Finally, we also provide parameter limits on the effective inflationary Hubble slow-roll (HSR) and potential slow-roll (PSR) parametrization.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Lukewarm inflation and the QCD axion

Paulo B. Ferraz, António Torres Manso and João G. Rosa

We show that a late period of warm inflation, at temperatures just above the QCD scale, can dilute the abundance of the QCD axion produced by the misalignment mechanism, thus avoiding the need to fine-tune the initial misalignment angle in scenarios with an axion decay constant close to the GUT scale. We develop a concrete realization of this lukewarm inflation stage involving right-handed neutrinos in 0.1 - 1 GeV mass range and an associated scalar sector, showing that coherent axion oscillations are damped during this period. In this scenario, a previously generated large baryon asymmetry may also be diluted to yield the observed value, and lukewarm inflation is followed by an early-matter era dominated by the lightest right-handed neutrino, before it decays into Standard Model states. This model can be tested via changes to the number of relativistic species and the induced small-scale enhancements of the primordial curvature power spectrum, leading to primordial black holes and scalar-induced gravitational waves.
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Cosmology and Nongalactic Astrophysics

Generalised Visibility ILC: a new foreground mitigation strategy for interferometric HI intensity mapping in the low-redshift Universe

M. Ruiz-Granda, A. Mazumder, L. Wolz et al. (+3 more)

HI intensity mapping is a powerful probe of the large-scale matter distribution and of the underlying astrophysics and cosmology. However, its application is limited by the challenge of separating the faint neutral hydrogen (HI) signal from much brighter foreground emission. We present a new non-parametric foreground-cleaning method in visibility space for low-redshift HI intensity mapping and apply it to interferometric MeerKAT and SKA-Mid-like simulations. Our newly-developed Generalised Visibility Internal Linear Combination (GVILC) method combines Principal Component Analysis (PCA) for foreground subspace identification, informed by a prior HI signal-plus-noise covariance matrix, with a multi-dimensional ILC in visibility space to suppress foregrounds and recover the HI signal with reduced contamination. The number of modes to remove in the PCA is calculated using a data-driven statistical approach, leading to significant foreground residual suppression with limited HI signal loss. Moreover, GVILC in combination with foreground avoidance can prevent most of the signal loss, while simultaneously recovering modes that were initially contaminated by foregrounds. The mean squared error statistic shows that for both MeerKAT and SKA-Mid-like simulations, GVILC outperforms the foreground avoidance only strategy. We find that including a more realistic HI model with line broadening and spatial correlations between HI and continuum sources leads to increased signal loss after foreground removal, without affecting the number of modes removed by GVILC. This paper demonstrates that GVILC is an effective method to clean foreground contamination in HI intensity mapping with radio interferometric data, enabling the recovery of cosmological information from previously inaccessible regions of Fourier space.
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All authors M. Ruiz-Granda, A. Mazumder, L. Wolz, M. Remazeilles, D. Herranz, P. Vielva

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Probing Scalar-Induced First-Order Phase Transitions with the Diffuse Supernova Neutrino Background

Sudipta Das, Shamik Niyogi and Manibrata Sen

We investigate the possibility of probing a scalar-induced first-order phase transition (FOPT) inside core-collapse supernovae through the diffuse supernova neutrino background (DSNB). We consider a light scalar coupled to neutrinos that is produced and thermalised in the proto-neutron-star core. This leads to two distinct neutrino components: a prompt contribution from thermally produced scalars and a delayed, spectrally narrow contribution from the decay of coherent scalar excitations due to the FOPT. We study the resulting DSNB signal at Super-Kamiokande, Hyper-Kamiokande, and DUNE, finding a strong dependence on the neutrino mass ordering. The recent Super-Kamiokande data already constrain the scalar parameter space for inverted ordering and quasi-degenerate neutrino masses, while future detectors can significantly improve this sensitivity. Our results demonstrate that DSNB measurements can provide a novel probe of finite-temperature scalar dynamics in core-collapse supernovae.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Lukewarm inflation, primordial black holes and gravitational waves

Paulo B. Ferraz, António Torres Manso and João G. Rosa

We show that a secondary period of warm inflation, at temperatures parametrically below the GUT scale, may not only dilute any unwanted thermal relics formed after reheating but also significantly enhance the power spectrum of primordial curvature perturbations on small scales. The latter is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-solar mass primordial black holes (PBHs). This scenario could, in particular, explain the NANOGrav signal if it persists at much higher frequencies with a comparable magnitude, up to a sharp cut-off, $f_{max}$. The associated PBH mass distribution may exhibit either a peak at a mass $M_*\propto f_{max}^{-2}$ or a broad plateaux above this mass threshold, depending on the spectral tilt. Moreover, in this scenario the NANOGrav signal is compatible with a significant fraction of dark matter in PBHs in the asteroid- and planetary-mass ranges.
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Cosmology and Nongalactic Astrophysics

On the Clustering Bias of Unresolved Gamma-Ray Sources

Bhashin A. Thakore, Marco Regis, Michela Negro et al. (+4 more)

The Unresolved $\gamma$-Ray Background (UGRB) encodes the collective emission of source populations that are too faint to be detected individually, and its cross-correlation with tracers of the large-scale structure has emerged as a powerful tool to characterize those populations. In this work, we analyze the weak-lensing–UGRB cross-correlation using a reference blazar model. By modeling the relation between blazar $\gamma$-ray luminosity and host-halo mass, we infer the average linear bias $\langle b(z) \rangle$ and host-halo mass $\langle M(z) \rangle$ of the unresolved blazar population. We find that the signal is dominated by moderately biased sources, with $\langle b \rangle \gtrsim 2$ at $z\simeq 1$, hosted by halos with $\langle M \rangle \sim \mathcal{O}(10^{13}\,M_\odot)$. Repeating the analysis with a misaligned-AGN model yields consistent bias values, indicating that the result is determined by the clustering properties of the UGRB rather than by the details of the $\gamma$-ray source model.
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All authors Bhashin A. Thakore, Marco Regis, Michela Negro, Stefano Camera, Daniel Gruen, Nicolao Fornengo, Aaron J. Roodman

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Collective flavor conversion in dense neutrino plasmas

Damiano F. G. Fiorillo

Compact transient sources, such as supernovae (SNe) and neutron star mergers (NSMs), host a population of thermal neutrinos in their inner cores, which decouple from the dense matter as they stream out. Yet, collisionless does not mean free; their density is large enough to mediate collective waves driven by the coherent weak neutrino–neutrino interaction. These collective waves carry little energy, but crucially they transport flavor. Neutrinos thus form a collisionless plasma with flavor transport driven by flavor waves, whose quanta are called flavomons $\psi$. The wavelength of these flavomons is much shorter than the characteristic scales of SNe and NSMs, so that a brute-force numerical treatment of the neutrino plasma is beyond our capabilities. Yet flavomons cannot be neglected, as the stimulated neutrino decays, schematically $\overline{\nu}_e\to \overline{\nu}_\mu\psi$, cause a rapid buildup in their population, more conventionally called a flavor instability. We review the theory of the neutrino plasma, and systematically discuss the instabilities leading to flavomon growth, and connect this emerging quasiparticle description with recent advances in numerical neutrino flavor kinetics.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

A High-Mass Size Deficit for Void Galaxies in the Complete SDSS DR7

Olivia Curtis, Bryanne McDonough and Tereasa G. Brainerd

We characterize how environment shapes the sizes, luminosity functions, and mass functions of galaxies in large-scale underdensities by comparing the NSA catalog of the Sloan Digital Sky Survey Data Release 7 with an identically selected TNG300 sample, both built with the void finding algorithm VoidFinder, and by assigning a local average underdensity contrast to each galaxy via a spherical top-hat smoothed density field approximation. Void galaxies have fainter characteristic magnitudes than their non-void counterparts, and, at fixed stellar mass, redshift, and color, NSA void galaxies with $M_*>10^{11}h^{-1}M_\odot$ are about $11\pm3\%$ more compact than galaxies in the field, a deficit the TNG300 simulation reproduces. The galaxies that are responsible for this effect are almost all central and predominantly early type, i.e., the systems that are most likely to grow their outer envelopes via late-time mergers. These trends hold across two redshift bins to $z\leq0.114$. Crucially, this deficit is not a fixed property of the void sample but a steep function of the underdensity contrast, deepening toward the emptiest interiors and washing out at a typical density, implying that strict density control and sample selection are imperative when conducting environmental dependency studies like these. The same environmental dependence appears in the stellar mass function, which shifts to lower masses in the deepest voids, and in the close-pair (i.e., the ongoing merger) fraction, which falls toward the emptiest regions. Together, these point to a late-time, merger-driven growth of massive galaxies that is suppressed in voids, leaving their most massive members structurally distinct today.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Cosmological Correlators from Scattering Amplitudes: A Review

Soner Albayrak and Savan Kharel

The primordial statistics underlying the CMB and large-scale structure are encoded in late-time cosmological correlation functions (constructed from the coefficients of the wavefunction of the universe). They are the closest analogue cosmology has to an $S$-matrix, yet the standard $S$-matrix toolkit does not directly apply. This review explains how the modern scattering-amplitudes program (spinor helicity, on-shell recursion, the double copy, positive geometry, and generalized unitarity) has nevertheless been extended to cosmology and, through a single analytic continuation, to Euclidean anti-de Sitter space, where the same objects appear as holographic boundary correlators and are often cleanest to compute. The organizing framework is momentum space on the late-time boundary, where the primordial statistics are simplest and where the total energy of the external legs, the sum of their momentum magnitudes, controls the analytic structure. At the total-energy singularity, the flat-space scattering amplitude emerges. We develop this toolkit starting from the wave equation and use it to compute tree-level scalar, gauge-field, and graviton correlators, exposing relations across spins and dimensions. We then show how bulk integrals can be bypassed using cosmological polytopes, on-shell recursion, and curved-space versions of the double copy, before extending the discussion to loops, soft limits, transition amplitudes, and (A)dS cutting rules. Finally, we connect these structures to inflationary observables and to three allied programs: the cosmological optical theorem, the cosmological bootstrap, and the cosmological collider. We conclude with a map of the current frontier and a set of open and interesting problems.
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Cosmology and Nongalactic Astrophysics

Where the Forest Goes Dark: Halo-centered Characterization of High Column Density Systems with IllustrisTNG

Victor R. Soares da Silva, Daniel López-Cano, L. Raul Abramo et al. (+2 more)

High column density systems of neutral hydrogen (HCDs) — Lyman limit systems (LLSs), sub-damped and damped Ly$\alpha$ absorbers (DLAs) — contaminate both the 3D and the 1D statistics of the Ly$\alpha$ forest. Most DLAs are masked out from the analyses, but cleaning algorithms are not perfect, and weaker LLSs are individually undetectable, so the residual contamination is absorbed into nuisance parameters that dilute the cosmological constraining power. Simulations provide the ideal setting to study this effect, allowing absorption features to be directly traced back to the gas producing them. We identify high-column-density structures on the gas cells of the TNG50 hydrodynamical simulation, deblend them in velocity space, and split every sightline into HCD-only and forest-only spectra. Applied to halos at $z \simeq 3$ out to 50 virial radii, it yields each class's covering fraction against impact parameter $b$ and halo mass. The impact parameter defines the type of absorption appearing in the spectrum: DLAs give way to sub-DLAs at $b \approx 0.11\,R_{200c}$, sub-DLAs to LLSs at $0.3$, and LLSs to the Ly$\alpha$-forest at $0.5$, which covers $\simeq 78\%$ of sightlines at $R_{200c}$. In units of $R_{200c}$ the sequence is nearly mass-independent over three decades in mass, so the virial radius sets the scale of the neutral gas distribution. A single Voigt component recovers the column density of essentially every damped system, but not of LLSs, whose absorption features often arise from several separate contributions from gas structures along the sightline. Our detailed characterization of HCDs gives the first step to the construction of advanced techniques to directly forward-model their contribution to Ly$\alpha$ spectra.
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All authors Victor R. Soares da Silva, Daniel López-Cano, L. Raul Abramo, J. Chaves-Montero, Francisco Maion

Cosmology and Nongalactic Astrophysics

Follow-up of SN 2025wny VI: The Rate and Detectable Population of Strongly Lensed SLSNe-I in ZTF

Jacob O. Hjortlund, Edvard Mörtsell, Ariel Goobar et al. (+13 more)

The Type I superluminous supernova (SLSN-I) SN 2025wny, multiply imaged by two foreground galaxies at $z_l = 0.375$, is the first confirmed strongly lensed SLSN and the highest-redshift ($z_s = 2.015$) multiply imaged supernova in a galaxy-scale configuration. We ask whether one discovery in seven years of Zwicky Transient Facility (ZTF) operations is consistent with expectations, and whether SN 2025wny is typical of the detectable population. We develop a forward simulation of strongly lensed SLSNe-I in ZTF, combining an empirically calibrated volumetric rate and luminosity function with a galaxy-scale deflector population, unresolved lensed light curves, and the actual ZTF observing history. We predict $0.037^{+0.022}_{-0.020}\,{\rm yr}^{-1}$, consistent with the rate of $0.14^{+0.31}_{-0.11}\,{\rm yr}^{-1}$ inferred from a single discovery in seven years of ZTF operations. Conditioning the simulation on discovery by ZTF corrects the magnifications and intrinsic luminosity of SN 2025wny for Malmquist- and magnification biases: the debiased peak bolometric luminosity, $\log_{10}(L_{\rm bol,int}/{\rm erg\,s^{-1}}) = 44.60^{+0.05}_{-0.10}$, places it at the $\sim$97th percentile of the assumed SLSNe-I luminosity function. SN 2025wny is typical of the detectable population in redshift, luminosity, and magnification, but its $4.9''$ image separation exceeds single-galaxy deflector expectations, implying our rates are conservative for wide-separation systems.
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All authors Jacob O. Hjortlund, Edvard Mörtsell, Ariel Goobar, Joel Johansson, Avinash Singh, Alice Townsend, Erin E. Hayes, Maggie L. Li, Steve Schulze, Suhail Dhawan, Jakob Nordin, Aleksandra Bochenek, Chiara Ventura, Conor M. B. Omand, Jacob L. Wise, Jesper Sollerman

Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

CosmoDyn: a semi-analytic post-processing framework for the dynamical evolution of compact stellar systems and black holes in cosmological simulations

Pierre Boldrini, Paola Di Matteo, David Katz et al. (+5 more)

Although a large number of cosmological simulations are now publicly available, their spatial and mass resolutions remain insufficient to accurately follow the dynamics of compact stellar systems and black holes. A complementary approach is therefore required to exploit the cosmological assembly histories encoded in these simulations without rerunning them. We present CosmoDyn, an open-source Python framework that reconstructs time-dependent galactic environments from any cosmological simulations and explicitly follows unresolved compact objects within them. A distinctive feature of CosmoDyn is that it models not only the main host galaxy but also its accreted satellites via moving gravitational potentials. The framework can therefore account simultaneously for the delivery of ex-situ populations and for the dynamical influence of satellites on in-situ population already present in the host. The modular pipeline comprises four main stages: reconstructing the evolving host and satellite potentials; generating in-situ and ex-situ populations of compact objects; integrating their orbits with configurable prescriptions for dynamical friction, and mass loss; and modeling tidal streams. Once reconstructed, the same cosmological environment can be reused to explore different objects, initial conditions, and physical prescriptions at low computational cost. CosmoDyn thus enables rapid parameter exploration and applications to statistically significant galaxy samples, while its modular architecture is designed to incorporate progressively more realistic potentials, and formation models.
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All authors Pierre Boldrini, Paola Di Matteo, David Katz, Laia Casamiquela, Chervin Laporte, Maxime Assuerus, Marco Montuori, Glenn van de Ven

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Reheating Bounds from Thermal GUT Monopole Production

Donald Liveoak, Arielle Schutz and James D. Wells

Magnetic monopoles are a generic prediction of Grand Unified Theories (GUTs) that are in tension with modern cosmological and observational bounds. In this paper, we calculate the present-day abundance of GUT monopoles produced thermally in the early Universe. We improve on previous calculations by accounting for full relativistic corrections to the thermal abundance and enhanced monopole annihilation due to the emission of radiation and scattering off massive gauge bosons, the Standard Model fermions and their superpartners. To obtain a present-day energy density less than that of dark matter, we show that the reheating temperature of the Universe, $T_{\rm RH}$, must be less than $0.55$ times the GUT symmetry breaking scale $T_{\rm GUT}$ for the canonical 't Hooft-Polyakov monopole mass. Accounting for Parker bounds on the present-day magnetic monopole abundance, the bound is tightened to $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.45$. Furthermore, experimental bounds from Super-Kamiokande require $T_{\text{RH}}/T_{\text{GUT}} \lesssim 0.35$ in our scenario.
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Cosmology and Nongalactic Astrophysics · Cross-listed from astro-ph.GA

Signatures of dark subhaloes in dwarf spheroidal galaxies: II. Transient and localised kinematic features

Eduardo Vitral, Jorge Penarrubia, Roeland P. van der Marel et al. (+1 more)

We use controlled N-body simulations to investigate whether dark matter subhaloes leave detectable signatures in the internal kinematics of dwarf spheroidal galaxies. At each snapshot, we fit a velocity distribution function to stellar line-of-sight velocities and proper motions, construct normalised residual fields for the projected velocity components, and analyse their power-spectra. We show that subhalo encounters generate a plethora of kinematic features. Amongst the most prominent are rotation-like signals, which arise in our models even though the stellar component is initialised without intrinsic rotation. In line-of-sight velocity alone, several snapshots resemble the classical blueshift–redshift pattern associated with stationary rotation. The plane-of-sky components, however, bring complexity, with alternating regions of expansion and contraction, as well as clockwise and anticlockwise streaming. Although we observe coherent streaming globally, these structures depart from typical equilibrium configurations, while their residual power-spectra quantify the characteristic spatial scales involved. This signal strengthens in models containing more massive subhaloes and becomes difficult to recover for small stellar samples: robust power-spectrum recovery of the full velocity-space signature usually requires O(10^{4}) tracers, although a rotation signal alone can be recovered with considerably smaller samples. These results suggest that dwarf spheroidal velocity fields can retain signatures of subhalo heating. Future spectroscopy, improved Gaia astrometry, and chemo-dynamical information should turn these diagnostics into population-level probes of dark matter substructure.
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All authors Eduardo Vitral, Jorge Penarrubia, Roeland P. van der Marel, Matthew G. Walker

Cosmology and Nongalactic Astrophysics

Cosmological anatomy of interacting dark energy

Miguel A. Sabogal, Sunny Vagnozzi and Eleonora Di Valentino

Interacting dark energy (IDE) models, featuring interactions between dark matter (DM) and dark energy (DE), have received significant renewed interest. However, little attention has been devoted to understanding their genuine cosmological signatures, with comparisons against $\Lambda$CDM often carried out at fixed cosmological parameters. Considering the widely studied model with energy exchange rate proportional to the DE density, we carry out a three-level sequence of comparisons, starting from the naïve fixed-parameter comparison, then compensating for shifts in $\theta_s$ and $z_{\text{eq}}$, and then removing effects due to the modified background. We show that fixing $\theta_s$ and $z_{\text{eq}}$ leads to pre-recombination evolutions of the Weyl potential, photon monopole, and baryon velocity which are nearly identical to their $\Lambda$CDM counterparts, and hence virtually indistinguishable Cosmic Microwave Background (CMB) temperature power spectra. Comparing IDE to a non-interacting $w$CDM model with the same background, we find small scale-dependent signatures in CMB lensing. We find larger differences in the matter power spectrum, reflecting the different values of $\Omega_m$ resulting from the different partition of the dark sector into DM and DE, with only percent-level differences remaining once we compare $\Omega_m^2P_m(k)$, indicating the importance of high-fidelity determinations of $\Omega_m$. Our controlled comparison strategy can be a powerful tool for a wide range of models beyond $\Lambda$CDM.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Probing Lorentz-violating scalar forces and dark matter with precision matter and antimatter experiments

Yevgeny V. Stadnik

We explore a class of Lorentz-violating scalar-field models where the effects of the scalar field on antimatter can be strongly enhanced compared to matter. Non-trivial differences in phenomenology arise for spectroscopy measurements depending on whether the scalar field changes slowly or rapidly on the atomic scale. We highlight opportunities for precision tests in the laboratory including dark matter searches, in particular with spectroscopy and interferometry measurements, as well as certain types of antimatter experiments.
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Cosmology and Nongalactic Astrophysics

Void probability function in the Quijote simulations

Snehasish Bhattacharjee

The void probability function (VPF) is the likelihood of finding no tracers (galaxies or dark-matter haloes) within a given volume and is sensitive to the large-scale matter distribution. We investigate the VPF of dark matter haloes and galaxies using the Quijote N-body simulations across a range of cosmological models, including $\Lambda$CDM and several extensions. We examine its dependence on cosmology, redshift, halo mass, morphology, and sample dilution, and compare the results with theoretical predictions from the geometric hierarchical (GH) and negative binomial (NB) models. We find that the halo VPF is sensitive to cosmology and halo mass and follows the GH model at $z=0$, with $\Lambda$CDM showing the smallest deviation and the massive-neutrino cosmology the largest. At higher redshift and stronger sample dilution, the VPF departs from the GH model and approaches the NB model. The dependence on halo mass varies with cosmology, with low-mass haloes showing the largest deviations in $\Lambda$CDM, while intermediate- and high-mass haloes show stronger deviations in the modified-gravity scenario. In redshift space, the VPF shifts toward the NB model, with primordial non-Gaussianity producing the largest deviations. For galaxies, the VPF depends on morphology and cosmology, with ellipticals following the GH model and spirals following the NB model. We also find that cosmic variance introduces non-negligible scatter in the VPF measurements. Overall, these results suggest that the VPF could be useful as a computationally efficient probe to distinguish extensions of the standard $\Lambda$CDM model in upcoming large-volume galaxy surveys.
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Cosmology and Nongalactic Astrophysics

Constraints of Big Bang Nucleosynthesis and Cosmological Observations on varying Higgs VEV

Hongrui Feng, Yudong Luo, Toshitaka Kajino et al. (+2 more)

The Higgs vacuum expectation value (VEV) alters both the electroweak and strong interaction rates. We study both effects on Big Bang Nucleosynthesis (BBN) and seek concordance between observed primordial abundances of light elements and cosmological constraints from cosmic microwave background (CMB) fluctuations and anisotropies. We find a strong negative correlation between primordial 4He abundance and the Higgs VEV. Consequently, using a 1.58% uplift of the Higgs VEV during BBN from the current value, an agreement can be achieved among the new primordial 4He abundance, observed by the EMPRESS group, Deuterium abundance determined from absorption lines in the Lyman-alpha forest along the line-of-sight of high-redshift quasars, and the lithium abundance on the Spite plateau. This agreement requires a baryon-to-photon ratio different from the CMB determination, indicating the need for non-standard cosmological evolution between BBN and recombination epochs.We also demonstrate that a 0.2% uplift in the Higgs VEV can partially alleviate the "cosmic Li problem", keeping consistency with the CMB with remaining discrepancy potentially accounted for by stellar depletion mechanisms.
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All authors Hongrui Feng, Yudong Luo, Toshitaka Kajino, Bao-Hua Sun, Tatsushi Shima