Daily Summary for 2026-10-09

Introduction to the show: ident: Astrophysics Radio. The week's best astrophysics papers, unpacked for curious ears.

Vera: It's the ninth of October, twenty twenty-six, and this is the day's research.

Jocelyn: 41 new papers came out today.

Vera: I'm Vera.

Jocelyn: And I'm Jocelyn, here with Subrahmanyan.

Vera: We'll take the day in one pass, then pull out the papers we're staying with.

Jocelyn: Start us off with A GPU-Accelerated JAX Framework for Robust Parametric Component Separation and Clustering Optimization for CMB Polarization Satellites.

The summary: Vera: Today is the ninth of October twenty twenty six. We are diving into work on cosmic microwave background polarization data.

Jocelyn: That involves separating foreground contamination from faint cosmological signals for early universe physics.

Vera: The main effort is a new JAX implementation for parametric component separation and clustering optimization for CMB satellites.

Jocelyn: This method handles spatially varying foreground spectral energy distributions by scanning thousands of pixel subset configurations AKMPC.

Vera: It achieves up to a hundred times speed-up over older optimizers when run on GPUs. It has reduced the upper limit on the tensor-to-scalar ratio r by about thirty percent in LiteBIRD simulations.

Jocelyn: Building on that, there is work modeling large scale structure like Sym-EFT Accelerating Effective Field Theory of Large Scale Structure with Symbolic Regression Sym-EFT.

Vera: This tool emulates the one and two loop cold dark matter power spectrum using symbolic regression for fitting counterterms. It is fast and maintains errors better than zero point five percent.

Jocelyn: Research looks at how dark matter models affect the Lyman-alpha forest Lyman-alpha Forest Signatures of Mixed Fuzzy and Cold Dark Matter.

Vera: This study compares different dark matter treatments, finding flux statistics depend on velocity prescription rather than just the matter power spectrum. These differences grow toward higher redshift and smaller scales.

Jocelyn: This contrasts with work on galaxy clusters like Cosmic gas accretion from filaments onto galaxy clusters using the IllustrisTNG simulation.

Vera: This highlights how filamentary structures drive anisotropic gas inflows into massive systems.

Jocelyn: There are insights into high redshift star formation from JADES Evolution of nitrogen abundances in star-forming galaxies from z 1.5-7 JADES.

Vera: These measurements using JWST data reveal significant scatter in nitrogen abundance. Extreme enhancements are tied to the most intense starbursts, which is important context for chemical enrichment in these early systems.

Jocelyn: Work on gravitational wave emission from nonspherical collapse is particularly important for probing the pre-Big Bang thermal history.

Vera: It offers a way to map present-day gravitational wave spectra to detector sensitivity bands to reveal information about reheating temperatures.

Jocelyn: This study uses a semirelativistic N-body framework to evolve collapse via Zel'dovich deformation in an Einstein--de Sitter background. It shows reliable signal prediction demands fully numerical treatment of nonlinear dynamics.

Vera: Fitting-based procedures and Zel'dovich estimates fail to capture post-shell-crossing evolution, leading to incorrect power estimations for gravitational waves.

Jocelyn: After averaging results from Doroshkevich and BBKS distributions, the two spectra show similar shapes at the peak amplitude. However, the BBKS result is systematically smaller because its dominant contribution comes from peaks of modest height around nu three. This work connects to a broader understanding of cosmological structure formation as one can map these GW spectra across different frequency ranges to constrain early universe physics.

Vera: Research into galaxy clusters focuses on disentangling turbulence from bulk motions in the intracluster medium.

Jocelyn: A paper using GPU-accelerated filtering pipelines on a major galaxy cluster merger simulation found that turbulent pressure fraction on physical scales of fifty kiloparsecs peaks at five percent during the merger. It then drops to two percent after about one point three gigayears, suggesting turbulence levels remain low unless a cluster has been recently perturbed by a major merger, which aligns with recent XRISM observations.

Vera: Another area involves wave propagation in astrophysical environments looking at how solar vortices act as conduits for magnetoacoustic waves.

Jocelyn: Using information-theoretic metrics like Normalised Mutual Information and Jensen-Shannon Divergence, the authors provided the first observational identification of a solar vortex footpoint by locating it where there is highest shared information with the chromospheric swirl. The Bifrost simulation indicated that vortices primarily support compressive magnetoacoustic waves in the lower atmosphere, and these modes carry a thermal signature relevant for localized heating.

Vera: Analysis of binary black hole mergers in gravitational wave catalogs reveals distinct mass regions characterized by sharp transitions in mass-ratio and effective spin properties. For example, below fifteen solar masses, the population favors equal-mass binaries with a narrow positive spin distribution. This suggests that different primary-mass ranges trace distinct formation channels, linking the merger statistics to hierarchical assembly processes.

Jocelyn: That covers all the material for today.

Vera: Indeed.

Vera: SAETASS offers a novel open-source numerical tool for solving time-dependent transport equations in spherical symmetry.

Jocelyn: That solver is crucial for modeling non-thermal particle movement through astrophysical plasmas like supernova remnants.

Subrahmanyan: It uses a conservative finite-volume framework and operator splitting to handle advection, losses, and diffusion simultaneously.

Vera: Application to cosmic ray proton transport recovers steady-state limits while revealing pre-equilibrium temporal dynamics across diffusion regimes.

Jocelyn: This capability is complemented by AMS-02 proton and antiproton fluxes during solar minimum data.

Subrahmanyan: It develops a unified charge-dependent solar modulation model by solving the three-dimensional Parker transport equation.

Vera: That model fits observed fluxes using a local interstellar spectrum constrained by Voyager data.

Jocelyn: It employs neural network surrogate models to speed up parameter scans for understanding solar activity effects.

Subrahmanyan: Research addresses the hadronic origin of sub-PeV gamma-ray emission from pulsars via proton-proton interactions.

Vera: This explores an alternative explanation based on a one-zone superdiffusive environment with a diffusion index of one point zero five.

Jocelyn: This scenario requires proton luminosity about zero point one four times the spin-down luminosity of PSR J0622+3749.

Subrahmanyan: The study on wide binary stars tests Modified Newtonian Dynamics by measuring differential radial velocities with high precision.

Vera: These measurements improve upon Gaia DR3 in resolving velocity differences for constraining the global MOND acceleration scale.

Jocelyn: This technique combines kinematic measurements with astrometric data to constrain the global MOND acceleration scale.

Subrahmanyan: The analysis of Laniakea shows modeling bias on cosmological observables can shift inferred values for the Hubble constant.

Vera: This work uses peculiar velocity data from Cosmicflows-4 to model the triaxial expansion of Laniakea and luminosity distance corrections.

Jocelyn: The most significant finding probes fundamental physics through cosmic structure using the Integrated Sachs Wolfe effect or ISWRS.

Subrahmanyan: This links current and future CMB experiments with large scale structure surveys like Euclid and LSST to forecast results.

Vera: The analysis models how the ISWRS effect correlates with gravitational potential tracers like galaxy clustering, cosmic shear, and CMB lensing potential.

Jocelyn: This tests the neutrino mass sum M nu in the ν Λ CDM model by differentiating between cosmological models.

Subrahmanyan: A study on halo mass functions in mixed cold and fuzzy dark matter investigates an ultralight axion-like component.

Vera: This component has a mass between ten and twenty-four point five electron volts constituting up to three tenths of total dark matter.

Jocelyn: This fuzzy dark matter traces large scale distribution while suppressing small scale structure, reducing low mass haloes.

Subrahmanyan: A phenomenological model maps cold dark matter halo mass functions to their mixed cold and fuzzy counterparts.

Vera: This reproduces simulated results within about zero point one to zero point two dex across the explored parameter space efficiently.

Jocelyn: Work identifies an intrinsic degeneracy in simplified semi-analytic two spot models for thermal X-ray pulse-profile modeling.

Subrahmanyan: This suggests even a simplified model can produce two peaks on the likelihood surface when more complex factors are included.

Vera: This analytic degeneracy offers intuition for multi modal posterior distributions seen in other studies.

Jocelyn: The finding points to limitations in parameter inference methods concerning instrumental modeling and inference.

Subrahmanyan: The paper suggests including Doppler effects can still result in two peaks on the likelihood surface when errors are added.

Lucky paper: 2604.08463: Vera: So we’re looking at A GPU-Accelerated JAX Framework for Robust Parametric Component Separation and Clustering Optimization for CMB Polarization Satellites.

Jocelyn: It’s a novel JAX powered implementation for component separation that handles spatially varying foreground Spectral Energy Distributions by scanning thousands of pixel subset configurations.

Vera: The key here is the up to one hundred times speed-up over standard CPU optimizers and reducing the sixty-eight percent upper limit on the tensor-to-scalar ratio by approximately thirty percent relative to fixed configurations.

Jocelyn: The paper follows a parametric formalism where observed data in each pixel is a linear combination of astrophysical components with additive Gaussian noise.

Vera: They generalize this by allowing the spectral parameters beta p to vary across independent sky pixel subsets called patches.

Jocelyn: The method uses a spherical K-means clustering algorithm implemented via jax-healpy to partition the sky into disjoint patches where beta p equals beta k for all p in Pk.

Vera: They treat the number of patches assigned to each spectral parameter as discrete hyperparameters held fixed while optimizing the spectral parameters and recovering component amplitudes.

Jocelyn: A structured grid search is performed over G equal to the intersection of Gs, for each configuration CK, they optimize the spectral parameters by maximizing Lspec which depends on both parameter values in each patch and the spatial patch structure.

Vera: The selection metric is the upper limit of the sixty-eight percent confidence interval on the tensor-to-scalar ratio r hat plus sigma of r, which sums systematic bias driven by foreground residuals and statistical uncertainty.

Jocelyn: They found an estimate of r hat equal to eight point five times ten to the minus five with a sixty-eight percent confidence interval of negative two point seven times ten to the minus four plus positive six point five times ten to the minus4, which represents a about thirty percent reduction in the upper limit on r compared to fixed, manually tuned configurations.

Vera: The pipeline uses FURAX for end-to-end differentiability and GPU acceleration, leveraging intra-device parallelism via JAX’s vmap transformation.

Jocelyn: The central task of maximizing Lspec is solved using the custom AdaTopK optimizer which is a JAX native active-set algorithm that outperforms standard scipy TNC on CPU by up to one hundred times in low SNR regions.

Vera: They partitioned the sky into three disjoint Galactic regions based on Planck Galactic masks: high-latitude, mid-latitude, and low-latitude.

Jocelyn: The optimal patch counts vary by region; they found that the dust spectral index requires near pixel resolution while the synchrotron spectral index is well described by fewer patches.

Vera: This work addresses future developments aiming to move towards more flexible pixel subsets through grouping multiple K-means clusters or employing more flexible clustering algorithms like Support Vector Machine clustering.

Jocelyn: They noted that a naive binning approach does not perform well compared to the optimized K-means configuration, though they plan to extend the framework to incorporate instrumental systematics.

Subrahmanyan: From an engineering standpoint, seeing a one hundred times speed-up on GPU using a JAX native active-set algorithm is impressive for robust optimization in this kind of problem.

Vera: It’s a clean ablation showing how moving the optimization to a JAX native optimizer really helps stability in low SNR regions.

Jocelyn: It shows that the choice of how you structure your spatial modeling directly impacts the final confidence interval on r hat plus sigma of r.

Subrahmanyan: I think for those working on CMB polarization, this framework offers a very tangible way to get better bounds without needing massive amounts of simulation time.

Lucky paper: 2604.24852: Vera: We are looking at Cosmic gas accretion from filaments onto galaxy clusters using the IllustrisTNG simulation today.

Jocelyn: It characterizes gas accretion onto clusters using the IllustrisTNG-three hundred hydrodynamical simulation to build a coherent picture of how gas is accreted and thermally processed during its infall into these structures.

Vera: The paper focuses on filaments acting as distinct channels within the cluster environment, imprinting a strong directional dependence on gas properties that shapes their thermodynamic structure out to several virial radii.

Jocelyn: They utilize the IllustrisTNG-three hundred magneto-hydrodynamical simulation at z = zero analyzing four hundred fifteen galaxy clusters selected from the Friends-of-Friends halo catalog based on criteria like M200 > five x ten thirteen M sun h-one.

Vera: They extracted physical properties like temperature, entropy, density, and pressure from gas cells using equations (one) through (three), where entropy is defined as S = T n(two/three) e.

Jocelyn: To explore cluster properties, they assess the dynamical state using two proxies: a center-of-mass offset normalized by R200, denoted as delta r, and the sub-halo mass fraction fsub.

Vera: This selection process resulted in ninety-five relaxed clusters and ninety-five unrelaxed clusters.

Jocelyn: The core methodology involves probing the radial distribution of gas properties as a function of distance to clusters by comparing isotropic profiles with anisotropic profiles that account only for gas in filaments.

Vera: A key finding is that the ratio of anisotropic to isotropic profiles is "close to unity below zero point seven five R200," which indicates a large fraction of the cluster volume at these radii is occupied by filaments converging near cluster centers.

Jocelyn: The temperature profiles reveal three distinct thermal regimes influenced by filamentary structures.

Vera: At large distances, around r ≈

three point five – five: R200, filaments are "hotter than the isotropic average, reaching temperatures up to twice as high," suggesting filaments are isothermal at this scale and consistent with warm gas with T ∼ ten five–seven K.

Jocelyn: Between three point five and two R200, the radial temperature gradient is shallower along filaments than in their surroundings, resulting in temperatures "up to ∼ twenty percent lower around three R200 compared to the ambient medium," reflecting rapid penetration into the warm circumcluster medium.

Vera: Around 2R200, filaments become "hotter than the ICM and exhibit an inverse tangential gradient—i.e., the filament center is hotter than its outskirts." At this interface, filament temperature exceeds the isotropic average by up to ∼ ten percent, suggesting heating induced by interaction with the hot ICM.

Jocelyn: The study investigates how cluster mass and dynamical state impact gas anisotropy.

Vera: The "strong dependence with cluster mass is evident," as the temperature drop inside filaments around clusters, which is about one point five–3 point 5R200, is "significantly stronger for massive clusters, reaching up to thirty-five percent below the isotropic temperature."

Jocelyn: Furthermore, relaxed massive clusters exhibit the "strongest temperature contrast," with filament temperatures being "colder up to ∼ forty percent than the surrounding cluster outskirts at 3R200." This suggests that massive halos are linked to more "well-established" filaments that are denser and hotter.

Vera: The radial velocity analysis, quantified by the conditional probability distribution P(vrad r), highlights preferential flow.

Jocelyn: Beyond 3R200, "warm gas predominantly accretes along filaments," while between 1R200 and 3R200, velocities are bimodal: "high-velocity inflows occur mainly along filaments, while lower-velocity outflows are almost only outside filaments."

Vera: This indicates that gas accretion occurs through a combination of "coherent filamentary inflows and more diffuse isotropic infall from the surrounding medium," with gas within filaments following "preferential, dynamically organized pathways."

Jocelyn: The analysis also identifies potential shock mechanisms in the cluster outskirts.

Vera: Between one and 2R200, the entropy outside filaments increases from ∼ zero percent up to ∼ fifty percent higher than inside filaments, likely reflecting heating or mixing driven by shocks.

Jocelyn: A Mach number distribution around R200 shows "a shock front near R200 with M ∼ two in most of the clusters," supporting the scenario where "fast infalling gas along filaments shocks against the intracluster medium."

Lucky paper: 2608.17869: Vera: We're looking at three dee simulations of magnetospheric accretion in T Tauri stars today, a paper by Pantolmos, Zanni, and Bouvier.

Jocelyn: This research investigates how an inclined stellar dipole influences a star's rotation through three dee Magnetohydrodynamic MHD simulations using the PLUTO code.

Vera: The core methodology involves modeling the interaction between an alpha accretion disk and a tilted magnetosphere surrounding a rotating star over twenty stellar periods, discarding the first ten to get robust results.

Jocelyn: A central finding is characterizing stable versus unstable accretion regimes based on the ratio of truncation radius R t to corotation radius R co.

Vera: Stable accretion is characterized by a condition where the ratio of R t over R co is between zero point eight zero and zero point eight five.

Jocelyn: When that ratio falls below that critical threshold, accretion becomes unstable, which leads to a net spin-up torque on the central star.

Vera: That transition point around zero point eight or zero point eight five is crucial because it dictates the net torque exerted on the star.

Jocelyn: The study also derives parameters for the truncation radius R t by relating it to A, r beta, and T equals one pi over two times pi one half.

Vera: They found that the ratio of truncation radius R t over stellar radius R star is weakly dependent on the mass accretion rate acc and dipolar intensity.

Jocelyn: But it is strongly dependent on the stellar rotation rate, which is a critical insight for applying simulation results to real observational data.

Vera: The corotation radius itself is defined by GM* P squared over four pi squared, where M* is the stellar mass and P is the rotational period.

Jocelyn: They decomposed the total torque into contributions from accretion and magnetospheric ejections, which they parametrize as SDI equals acc plus MEs.

Vera: Accretion torque is parametrized by K acc acc p G M* R t, while magnetospheric ejections are parametrized by K MEs B squared R star six over R MEs cubed.

Jocelyn: They also derived a specific condition for zero total SDI torque as SDI over J equals zero point eight three f zero factorial minus zero point zero one.

Vera: The contribution of stellar winds is accounted for via the torque parametrization SW equals SW r squared A star.

Jocelyn: Applying this framework to Classical T Tauri stars observed via spectropolarimetry, they predict that most young stars in the sample should currently be accreting in an unstable regime.

Vera: This instability leads to a net spin-up torque for most of those young stars in the observed sample.

Jocelyn: So, this work on three dee simulations of magnetospheric accretion in T Tauri stars shows a clear prediction for stellar spin evolution based on the accretion flow dynamics.

Lucky paper: 2512.21044: Vera: Alright, let's look at this one now. We're talking about Quantum scattering of hot H/D on CO2: Cross sections and rate coefficients for planetary atmospheres and their evolution by Cheikh T Bop and Marko Gacesa.

Jocelyn: The core idea here is how collisions between hot hydrogen atoms and CO2 play a central role in energy transfer and atmospheric escape in CO2-rich planetary atmospheres.

Vera: The scattering calculations reveal that mass-scaling from O/C–CO2 systems overestimates H–CO2 total cross sections by factors of thirty to forty-five.

Jocelyn: And isotopic substitution, using H/D, produces energy-dependent differences of up to thirty-five percent at energies less than zero point one electron volt.

Vera: The study presents "quantum mechanical jz-conserving coupled-states calculations" for state-resolved cross sections for H/D–CO2 collisions up to five electron volts.

Jocelyn: They used the high-level ab initio potential energy surface of Dagdigian from two thousand fifteen computed with the coupled cluster method RCCSD(T) and an augmented quadruplezeta basis set.

Vera: They employed the "quantum mechanical jz-conserving coupled states (CS) approximation" combined with a hybrid log-derivative-Airy propagator to solve the scattering problem.

Jocelyn: This method offers significant computational savings compared to the fully rigorous close-coupling approach, which is what they noted.

Vera: The results show that scattering is "strongly forward-peaked," yielding momentum-transfer cross sections substantially smaller than commonly assumed.

Jocelyn: Specifically, mass-scaling from O–CO2 and C–CO2 systems leads to an overestimation of the actual H–CO2 total cross section by up to factors of forty-five or about thirty.

Vera: Furthermore, isotopic differences are significant: D-induced cross sections exceed those from H by up to thirty-five percent at energy zero point one electron volt, but that difference falls below nine percent at higher energies.

Jocelyn: Elastic scattering accounts for forty percent to fifty-five percent of the total cross section across the full energy range.

Vera: They compute Maxwellian-averaged momentum-transfer rate coefficients by integrating the state-specific momentum-transfer cross section over a Maxwell–Boltzmann energy distribution.

Jocelyn: For thermal distributions, the isotopic ratio kD/kH is approximately zero point six across the temperature range of one hundred to five thousand Kelvin.

Vera: This indicates that deuterium atoms transfer about forty percent less momentum per collision than hydrogen atoms at comparable temperatures.

Jocelyn: The calculated rate coefficients are approximately sixteen times smaller than would be obtained by mass-scaling from O–CO2 collisions.

Vera: That implies H–CO2 energy transfer in hydrogen-rich regimes may have been less efficient than previously estimated.

Jocelyn: These revisions have direct implications for atmospheric escape modelling, particularly for thermal Jeans escape.

Vera: If a mass-scaled momentum-transfer cross section exceeds the true H–CO2 value by a factor f, the exobase altitude shifts by delta z exo approximately H times natural log f.

Jocelyn: That leads to exobase shifts of order about ten to twenty kilometers.

Vera: For non-thermal escape, differences between true and mass-scaled total or momentum-transfer cross sections translate directly into comparable changes in the number of collisions experienced by a typical suprathermal atom.

Jocelyn: These findings provide essential quantum mechanical inputs for revisiting atmospheric evolution scenarios on Mars, early Earth, and CO2-rich exoplanets.

Vera: The limitations are that the calculations treat CO2 as a linear rigid rotor with fixed bond lengths, neglecting vibrational excitation and vibration–rotation coupling.

Jocelyn: Also, the use of the CS approximation means that while transport cross sections are accurate to within about seven percent over the energy range considered, it may be less reliable very near threshold and for subtle interference features in differential cross sections.

Vera: The results underscore the limitations of mass-scaling and fitting approaches, highlighting the need for system-specific quantum calculations for light-atom projectiles with polyatomic targets.

Jocelyn: The key parameters enumerated are: cross sections calculated up to collision energies of five electron volts, a rotational basis including one hundred forty-one low-lying energy levels for CO2 from j zero to one forty, and up to two hundred forty-one partial waves used for convergence.

Vera: We also see that the state-specific transport cross sections are compared between the CS approximation and CC results, agreeing within seven percent across the full energy range.

Jocelyn: The Maxwellian-averaged rate coefficients show kH at three hundred Kelvin is one point eight four times ten to minus eleven cm cubed per second, while kD at three hundred Kelvin is one point one four times ten to minus eleven cm cubed per second.

Lucky paper: 2601.06250: Vera: We are looking at Characterizing turbulence in galaxy clusters defining turbulent energies and assessing multi-scale versus fixed-scale filters.

Jocelyn: This paper is about disentangling turbulence from bulk motions because the plasma is stirred by different processes on different scales, which makes it inherently ambiguous.

Subrahmanyan: They use filtering operators in real space to separate bulk motion from turbulence at different scales, showing how those filters can be used to define consistent kinetic and magnetic energies for the bulk and turbulent components.

Vera: The research applied a GPU-accelerated filtering pipeline to a simulation of a major galaxy cluster merger called Halo3 within the PICO-Clusters suite.

Jocelyn: They found that during the merger, "the turbulent pressure fraction on physical scales ≲one hundred sixty kpc reaches a maximum of five percent, before decreasing to two percent after ∼one point three Gyr from the core passage."

Subrahmanyan: These low values are consistent with recent observations of clusters with XRISM and suggest that "unless a cluster was recently perturbed by a major merger, turbulence levels are low."

Vera: The authors argue for an approach based on fixed-scale filtering and the computation of turbulent energies via statistical moments rather than the popular multiscale iterative filter method.

Jocelyn: They found that the iterative scheme can introduce artifacts and does not reliably disentangle fluctuations living on widely separated length scales.

Subrahmanyan: The mathematical preliminaries define filtering operators in real space using a kernel Wl(x′, x) parametrized by smoothing length l, which allows for decomposition into a smooth component denoted as ⟨f⟩l(x) and its fluctuating component δ fl(x).

Vera: Turbulent energies are defined using generalized statistical moments, specifically µ2 and µ3 of the turbulent fields.

Jocelyn: For magnetic energy, the filtered energy density is expressed as εB = εB,bulk + εB,turb where the bulk component is derived from the second-order moment: εB,bulk = ⟨B⟩two/8π.

Subrahmanyan: The turbulent component is defined by the third-order moment: εB,turb = P(µ2(Bi, Bi))/8π. Integrating these filtered energy densities over a volume V recovers the total energy EB = EB,bulk + EB,turb.

Vera: For kinetic energy in compressible turbulence where motions can reach transonic Mach numbers M ≳ one the filtered kinetic energy density is decomposed into three parts: εk = εk,bulk + εk,cross + εk,turb.

Jocelyn: The terms are defined as: εk,bulk = one/two⟨ρ⟩l Xi⟨ui⟩l⟨ui⟩l, and the turbulent kinetic energy density is given by epsilon k,turb = one/twoXiµ2(ui, ui) + one/twoXiµ3(ρ, ui, ui).

Subrahmanyan: In the subsonic limit where M ≪ one the turbulent kinetic energy density reduces to a form similar to the turbulent magnetic energy density.

Vera: They compute the "turbulent kinetic pressure fraction" fk,turb and "magnetic pressure fraction" fB,turb within R200,c for different filter scales.

Jocelyn: For the intermediate filter length l = thirty kpc, they measure a maximum kinetic turbulent fraction of fk,turb ≈ five percent near the core passage at t ≈ ten point seven Gyr and a subsequent decay to two percent by t = twelve Gyr.

Subrahmanyan: These estimates are noted as being "consistent with observations of nearby massive clusters (XRISM Collaboration et al. 2025c) in the regions farther away from the core."

Vera: The paper explicitly tests the multiscale iterative filter and concludes that it is unsuitable as a "one-size-fits-all solution."

Jocelyn: The iterative scheme suffers because its convergence is susceptible to noise and strongly depends on the initial conditions.

Subrahmanyan: It can fail to distinguish between fluctuations living on widely separated scales in tests involving Kelvin–Helmholtz instability, producing "visible artifacts in the bulk and turbulent fields."

Vera: The authors recommend that instead of an iterative approach, one should use a fixed scale filter with a physically-motivated choice for the smoothing length appropriate for the problem.

Jocelyn: When volume averaging and filtering operators commute, it is possible to recover the total energy within a volume by integrating the filtered energies: E⋆ = ZV ε⋆.