Rajorshi Sushovan Chandra, Debarshi Mukherjee, Tarun Souradeep
AstronomerThe authors develop NIRL-FLIP for free-form reconstruction of the primordial scalar power spectrum (PPS) from the CMB temperature power spectrum. NIRL iteratively updates the weak-lensing contribution using the PPS recovered in the preceding iteration, avoiding a prescribed PPS form when accounting for lensing. The Fourier-space iterative low-pass filter FLIP regularizes the reconstruction to suppress noise overfitting. Tests on a range of simulated PPS models, with bootstrap uncertainty estimates from simulated realizations, show reduced lensing-induced reconstruction bias and noise overfitting, with reported robustness, accuracy and precision. These are simulation-based performance results, not an observational detection of PPS features. The authors recommend the method for future searches for departures from a power-law PPS and for testing inflation models alongside joint cosmological parameter estimation.
PublicThe cosmic microwave background can help scientists reconstruct the pattern of tiny disturbances present in the early universe. However, gravitational bending of its light can distort that reconstruction, while noise can create misleading features. The authors combine an iterative method that updates the bending correction with a filter designed to prevent noise from being mistaken for structure. In tests using simulated early-universe patterns and simulated data realizations, the combined method reduced both kinds of error; the team also estimated reconstruction uncertainties. The work does not report a discovery of new features in actual observations. Instead, it offers a tool for future searches for departures from a simple primordial pattern that could help test theories of cosmic inflation.
Young explorerScientists study very old light to learn about tiny bumps in the baby universe. But the light gets bent on its way to us, and noise can make pretend bumps appear. The team made a computer method to account for the bending and filter out noise. It worked well in make-believe computer tests. They hope it will help scientists look for real clues about how the universe began, but these tests did not discover any new bumps in the real sky.
Nichole Barry, Jaiden Cook, Cathryn Trott+2 more
AstronomerThe authors derive a functional-analysis framework for widefield radio interferometric imaging to investigate geometry-dependent reconstruction errors and their effects on source flux-density estimates. Using adjoint operator descriptions, they simulate three cases for two fields with the Murchison Widefield Array: deconvolution errors from a minor iteration, gridding errors from excluding primary-beam sidelobes, and w-term errors from omitting the non-coplanar dimension during a 2 min near-zenith transit. In these simulations, fractional flux-density errors reach 5%, 0.1%, and 10%, respectively. The errors depend on the field, so these values are not universal bounds. The formalism also provides a basis for investigating other reconstruction errors.
PublicRadio telescope arrays build images from separate measurements rather than taking a single direct picture. This study develops a mathematical framework to examine how approximations in that process can distort geometry and change estimates of how bright radio sources are. The researchers simulate three kinds of reconstruction error for two fields using the Murchison Widefield Array. Errors in source brightness reach 5% for one image-cleaning step, 0.1% when the reconstruction excludes secondary responses of the telescope beam, and 10% when it neglects the array’s non-flat geometry during a two-minute observation near the point directly overhead. These are simulation results, and their size depends on the field being imaged; they are not fixed error levels for all observations.
Young explorerRadio telescopes collect clues that computers turn into pictures of the sky. If the computer takes shortcuts, it can make things in the picture seem a little brighter or dimmer than they should. The scientists used computer tests of two patches of sky to try three kinds of shortcuts. Some changed the brightness more than others, and the changes depended on which patch they tested. Their new math can help people study these picture-making mistakes.
Kohei Onoda, Shun Arai, Daisuke Yamauchi+3 more
AstronomerThis theoretical and numerical study examines Vainshtein screening in dark matter halos within Horndeski gravity. Assuming cold dark matter and spherical symmetry, the authors analytically identify conditions on halo profiles for effective screening. They find that screening becomes less effective as the central profile becomes core-like, even within the Vainshtein radius. To test whether fifth-force signatures can survive halo evolution, they simulate an isolated halo using Newtonian two-body interactions plus a spherical external fifth force. At equilibrium or quasi-equilibrium, mass proxies based on hydrostatic dynamics, the Jeans equation, and gravitational lensing can be biased relative to one another, unlike their expected agreement under Newtonian gravity. These model-dependent results suggest that comparing observational mass proxies could test gravity on halo scales; they are not an observational detection of modified gravity.
PublicSome theories explain the Universe’s accelerating expansion by changing gravity, but they need a way to hide any extra force on stellar scales. This study asks whether that hiding mechanism might work less well inside large dark matter halos. Mathematical calculations suggest it becomes weaker when a halo’s central density profile is more core-like. In a simplified computer simulation that includes an extra force, three ways of estimating the halo’s mass can disagree even after it settles into a nearly steady state. The authors suggest that comparing such mass estimates in observations could help test gravity. The study does not report an observed extra force.
Young explorerCould gravity have an extra, hidden tug? Scientists used math and a computer model to explore that idea in a big cloud of invisible matter. In their model, three ways of working out how much matter was there could give different answers. Looking for such differences might help test gravity, but they have not found the extra tug in the sky.
Jiale Wang, Taotao Fang
AstronomerUsing a parent catalog of 136 localized FRBs with measured DMs and spectroscopic host redshifts, the study examines foreground and host contributions to scatter about the Macquart relation. For 77 FRBs within the Gfinder footprint, DM excess relative to a fixed Macquart mean correlates with foreground group count excess (Spearman coefficient 0.459). Adding a foreground term to a mean host baseline reduces leave-one-out extragalactic-DM RMSE by 13.0% and MAE by 7.5%. For 20 FRBs with optical host axis ratios, a foreground term calibrated on the other 57 objects improves a host shape model: observer-frame leave-one-out RMSE falls from 76.3 to 64.0 pc cm^-3 and MAE from 54.2 to 50.2 pc cm^-3. The host-rest-frame residual standard deviation decreases by 20.2%, but this is an in-sample statistic. Idealized models based on the Milky Way electron density distribution yield inclination-dependent DM changes comparable to the fitted amplitude under the adopted assumptions; this is a model comparison, not a direct measurement of the inclination effect.
PublicFast radio bursts do not all follow the same average relationship between dispersion measure and distance. This study investigates how galaxies in front of the bursts and the bursts' own host galaxies contribute to those differences. Of a catalog of 136 bursts, 77 lie within the foreground-group survey area used here. In that subset, more foreground galaxy groups than expected are associated with larger dispersion measures above the adopted average relation. Including this foreground information reduces two prediction-error measures by 13.0% and 7.5% in tests that leave out one burst at a time. Predictions also improve for a smaller set of 20 bursts when foreground information is combined with host-galaxy shape. Simplified galaxy models suggest that viewing a host at different angles could produce changes comparable to those fitted, but that comparison depends on the models' assumptions.
Young explorerScientists studied quick radio flashes from space. The flashes do not all match the same simple pattern. Flashes with more groups of galaxies in front of them tended to be farther from that pattern. Using those galaxy groups helped scientists make better guesses about the flashes. The shapes of the galaxies where the flashes came from also helped in a smaller group. Simple pretend galaxies suggest that the angle we see them from might matter, but that is not yet proof.
Jiachen Bai, Benjamin Giblin, Andy Taylor
AstronomerThe authors propose cosmological statistics based on topological defects defined purely by the phase structure of the cosmic shear orientation field, complementary to conventional weak-lensing statistics that primarily probe amplitude. They characterise defect number densities, spatial clustering, and convergence distributions at defect locations. Fisher analyses under idealised and realistic survey conditions indicate complementary cosmological information. For Euclid-like simulated data, adding defect statistics yields constraints on Ωm and σ8 up to 3.9 times tighter than those from the convergence two-point correlation function alone. This gain is a simulation-based forecast, not a result from observed survey data.
PublicThe study proposes a new way to extract information about the universe from cosmic shear maps: examine defects in their directional patterns, rather than relying mainly on the strength of the signal. The researchers study how common these defects are, how they cluster, and their relationship to another lensing quantity called convergence. In forecasts using Euclid-like simulated data, combining defect statistics with a conventional method gives constraints on two cosmological parameters up to 3.9 times tighter than the conventional method alone. The improvement has not been demonstrated here with real observations.
Young explorerImagine a map of space filled with little arrows. Scientists suggest learning about the universe by finding places where the arrows make unusual patterns. They tried the idea with computer-made maps, and their tests suggest it could tell us more than an older method alone. This is not yet a result from real sky maps.
Jhananii Yuvaraj Babu, Luca Amendola
AstronomerThe study tests whether coupled quintessence can reproduce the evolving dark-energy equation of state favoured by DESI DR2, including an apparent crossing of w = −1 without a phantom field. Such a crossing can arise when a coupled dark sector is analysed assuming separate conservation. Two thawing potentials, a cosine and a double-exponential hilltop, are fitted to DESI DR2 BAO, Planck PR4 and three supernova compilations. Both improve on ΛCDM by Δχ² = 5–15, recovering 64–92% of the improvement obtained with w0waCDM. They track its equation of state at redshifts z ≲ 0.4, but cross w = −1 near z ≃ 1 rather than z ≃ 0.4–0.5. The coupling constraint is absolute value of β < 0.073 at 95%, with the two potentials agreeing on the coupling within 0.15σ. The cosine potential approaches the DESI-preferred evolution more closely and is weakly preferred by the fit. The coupling posterior has modes near β ≃ +0.05 and β ≃ −0.05; only the negative mode produces the crossing, and its peak is higher in every analysis. These are model fits to observations: the data favour, but do not yet require, coupled-quintessence phantom crossing.
PublicDESI DR2 data favour dark energy that changes over time, with its equation-of-state parameter crossing a boundary called w = −1. This study tests whether interactions within the dark sector could make that crossing appear without introducing a phantom field. The researchers fitted two theoretical models, using cosine and double-exponential hilltop potentials, to DESI DR2, Planck PR4 and three supernova compilations. Both fit better than the standard ΛCDM model, improving the fit statistic by 5–15 and capturing 64–92% of the improvement achieved by the comparison model w0waCDM. They follow that comparison model at redshifts below about 0.4, but cross the boundary near redshift 1 rather than 0.4–0.5. The cosine model is weakly preferred. The interaction strength β is constrained to an absolute value below 0.073 at 95%, and the two models agree on it within 0.15σ. Two preferred coupling values appear near +0.05 and −0.05; only the negative one gives the crossing, and it has the higher peak in every analysis. The observations favour this explanation but do not establish that it is necessary.
Young explorerScientists are studying whether dark energy changes as the universe grows. They tried two mathematical stories in which parts of the universe’s dark side interact. Both stories matched the observations better than the usual story, and one did a little better than the other. These interactions could make dark energy seem to cross a special boundary without needing a phantom field. But this is a possible explanation of the clues, not something scientists have proved must happen.
Felipe Avila, Camila Franco, Armando Bernui
AstronomerUsing FASHI DR2, the authors measure the two-point angular correlation function of 142,204 extragalactic HI sources at z < 0.09, with median redshift 0.034 and approximately 40% sky coverage. With an analytical Gaussian covariance, they find a broad bump near 50 degrees that could be a transverse baryon acoustic oscillation (BAO) feature. Comparing a fifth-order polynomial with a quadratic baseline gives Δχ² = 9.06 for three additional degrees of freedom, a nominal 1.9σ preference for a non-monotonic feature, not an established BAO detection. Their projection analysis shifts the expected BAO scale from 64 degrees for an infinitesimally thin redshift bin to 52 degrees for Δz = 0.09, close to the observed bump. However, comparisons with lognormal mock catalogues show that the bump is consistent with statistical fluctuations at the 1σ level. The study provides an observational baseline for wide-field HI clustering analyses and illustrates their potential to probe low-redshift acoustic features, while leaving the cosmological origin of this feature unresolved.
PublicResearchers used the FAST All Sky HI Survey to examine how 142,204 sources of neutral hydrogen are grouped across roughly 40% of the sky in the nearby Universe. They found a broad excess of pairs separated by about 50 degrees. This might be a baryon acoustic oscillation feature, a pattern linked to sound waves in the early Universe. Their analysis predicts that combining sources across the survey’s range of distances shifts the expected pattern to about 52 degrees, close to the observed feature. But that agreement is not enough to identify it: the statistical evidence is weak, and comparisons with simulated catalogues show that random fluctuations could explain the bump. The work offers a useful reference for future surveys, rather than a confirmed detection of an ancient acoustic pattern.
Young explorerScientists made a big sky map using hydrogen gas far beyond our galaxy. They found a small hint of a pattern that might come from sound waves in the very young Universe. But pretend sky maps showed that chance could make a similar pattern. So the scientists cannot yet tell whether they have found an ancient sound-wave pattern or just a lucky jumble.
Joel Hamlett, Catherine L. Hale, Matt J. Jarvis+4 more
AstronomerThe study detects a cross-correlation between MIGHTEE radio-source positions and Atacama Cosmology Telescope CMB lensing at approximately 4σ over 20 square degrees, for S_1.4GHz > 40 μJy. Combining this with low- and high-redshift radio-source auto-correlations constrains the evolution of galaxy bias. Both b(z) = (1.63 +0.19/−0.22)/D(z), where D(z) is the linear growth factor, and b(z) = (0.49 +0.44/−0.32) + (1.62 +0.37/−0.51)z fit comparably well; current measurements cannot distinguish them. AGN and star-forming galaxy fractions estimated from a radio luminosity function enable model-dependent inference of their separate biases without individual classifications. Although no model is significantly favoured, the best-fitting model gives b_AGN(z) = (2.60 +0.65/−0.91)/D(z) and b_SFG(z) = (0.52 +0.47/−0.34)/D(z). A prior from previous SFG bias measurements tightens these to (1.96 +0.37/−0.40)/D(z) and (0.90 ±0.06)/D(z), respectively.
PublicResearchers compared the locations of radio sources in the MIGHTEE survey with measurements of how matter bends light from the cosmic microwave background, made by the Atacama Cosmology Telescope. Across 20 square degrees of sky, they detected a statistical connection at about four-sigma significance. Combining this with measurements of how radio sources cluster, they studied how strongly these sources trace the distribution of matter at different cosmic epochs. Two different descriptions of how this relationship changes with redshift fit equally well, so the data do not yet distinguish between them. The team also estimated the proportions of sources powered by active galactic nuclei and by star formation, allowing their clustering biases to be inferred without classifying each source individually. The best-fitting model assigns a higher bias to active galactic nuclei, but no single model is significantly preferred. Including earlier measurements for star-forming galaxies makes the inferred biases more precise.
Young explorerScientists looked at where galaxies that send out radio waves sit in the sky. They compared those places with a map of how matter bends very old light. They found a connection, which helps them learn how galaxies gather together. Two different ideas about how this gathering changes over time both matched the clues, so they cannot yet tell which is better. They also used estimates to study two kinds of galaxies separately, without sorting every galaxy one by one. Older measurements helped make those estimates less uncertain.
José Antonio Nájera, Indranil Banik, Harry Desmond
AstronomerThe study tests whether inverse-distance-ladder constraints exclude late-time solutions to the Hubble tension, using a fourth-order expansion of H in 1 − a, DES-Dovekie SNIa, and DESI DR2 BAO, with an assumed standard sound horizon of 147.05 ± 0.30 Mpc. With DES as the only SNIa sample, the inferred H0 is 76.25 ± 2.87 km/s/Mpc, 3.1σ above the CMB-calibrated ΛCDM prediction and consistent with SH0ES at 1.0σ. Including legacy SNIa lowers H0 to 67.98 ± 0.69 km/s/Mpc, 4.7σ below SH0ES. Only 1.24% of 10,000 fiducial-ΛCDM mock realizations produce a shift at least this large from changed redshift sampling, suggesting a systematic mismatch between the SNIa samples. Adding local H0 anchors and fitting an enhancement ΔH(z) = A exp(−z/z1) gives H0 = 70.00 (+4.78, −0.98) km/s/Mpc and z1 < 0.086 at 1σ with DES, versus 67.66 ± 1.01 km/s/Mpc and unconstrained z1 with DES plus legacy data. The authors conclude that late-time solutions remain viable with homogeneous DES data but not with the legacy sample as published. Allowing arbitrary relative recalibration yields a legacy magnitude offset of 0.0646 ± 0.0391 mag and raises the predicted H0 to 71.03 ± 1.99 km/s/Mpc; this is not an independently established correction. Future homogeneous low-redshift samples, including DEBASS, are expected to test the legacy calibration and this conclusion.
PublicCould a recent change in cosmic expansion help explain why estimates of the Universe’s present expansion rate disagree? This study finds that the answer depends strongly on which supernova data are included. Combining DES supernovae with galaxy-distance measurements, and assuming a standard sound horizon, the researchers infer an expansion rate of 76.25 ± 2.87 km/s/Mpc. Adding a legacy supernova sample lowers it to 67.98 ± 0.69 km/s/Mpc. In simulations assuming a standard cosmological model, differences in redshift sampling produced such a large shift only 1.24% of the time. This suggests, but does not establish, a systematic mismatch between the datasets. A separate test including local expansion-rate measurements finds that a recent expansion enhancement remains viable with DES supernovae, but not with the legacy sample included as published. Letting the legacy sample’s brightness calibration shift raises the inferred expansion rate, but does not prove that recalibration is justified. Future surveys with more uniform supernova measurements should help determine whether the mismatch reflects calibration problems and whether late-time explanations remain feasible.
Young explorerScientists are trying to work out how fast space is growing. They used exploding stars as distance clues, but adding another group of stars changed the answer a lot. Their computer tests suggest this difference is hard to explain by chance alone. Maybe the star measurements do not quite match. Better-matched measurements could help them check whether space recently changed how it grows.
Gert Hütsi
AstronomerThe observed abundance and spatial clustering of JWST little red dots (LRDs) at z = 4–8 are compared with formation in virialized dark-matter halos and seeding by a dynamically subdominant primordial black hole (PBH) population. The halo scenario naturally accounts for both observables without fine-tuning. In the PBH model, matching the abundance requires a negligible PBH mass fraction, whose Poisson isocurvature contribution predicts clustering far below that observed. This argument also disfavors other dynamically subdominant early-forming seeds as randomly activated LRD populations, unless their initial clustering is finely tuned or their activity depends on massive host halos. PBH seeds remain viable in the latter case, but clustering alone cannot distinguish them from astrophysical seeds.
PublicThe researchers compared how many little red dots JWST sees in the early universe and how strongly they group together with predictions from two formation scenarios. The standard picture, in which these objects form in dark-matter halos, explains both observations without specially adjusted assumptions. A model involving a small population of primordial black holes can match the number of dots, but predicts much weaker grouping than is observed if the seeds are activated randomly. This favors the standard halo picture, but does not rule out primordial black holes as seeds: if massive host halos control their activity, the grouping alone cannot tell them apart from astrophysical seeds.
Young explorerJWST sees little red dots far away in space. Scientists checked how many there are and how they bunch together. A picture where the dots form in big clumps of dark matter fits both clues well. Another idea uses black holes left from the very early universe as seeds. If those seeds light up at random, the idea predicts too little bunching. The black-hole idea could still work if big dark-matter clumps control which seeds light up. Then bunching alone would not tell scientists which kind of seed is there.
Keith R. Dienes, Fazlollah Hajkarim, Lucien Heurtier+4 more
AstronomerThis theoretical study extends scalar-induced gravitational-wave calculations to cosmologies containing multiple fluids. The authors identify two modifications: velocity effects absent in single-fluid models and altered subsequent redshifting for modes that enter the horizon before the multi-fluid era ends. The predicted signal therefore carries information about both the expansion history and the internal fluid composition. As an example, they examine cosmological stasis, in which components with different equations of state maintain constant fractional abundances despite expansion. Although the effective equation of state is constant, the system remains genuinely multi-fluid. The calculated tensor power spectra and present-day gravitational-wave abundances differ significantly from standard radiation-dominated predictions. These are theoretical results, not reported gravitational-wave detections.
PublicThe researchers calculate how gravitational waves generated by early-universe density disturbances would behave if the universe contained several distinct energy components. Their model predicts changes both in how the waves are produced, through velocity effects unique to the mixture, and in how the waves weaken as the universe expands. Such signals could potentially reveal the mixture's composition as well as the expansion history. One example is 'cosmological stasis,' when different components keep constant shares of the total energy despite expansion. The predicted wave spectrum and abundance today differ substantially from those expected for a standard radiation-dominated universe. The study presents theoretical predictions, not observations of these signals.
Young explorerImagine the young universe as a mix of different ingredients that can make tiny ripples in space. Scientists used calculations to explore how those ingredients could change the ripples as the universe grows. They found that the mix could matter, not just how fast everything grows. These are predictions; they have not spotted these ripples in this study.
Kimiko Queen, Abigail V. Fisher, Johannes U. Lange
AstronomerPredicted galaxy-galaxy lensing amplitudes tend to exceed observations by about 20–40%, primarily on small scales—the lensing-is-low problem. Earlier work using BOSS foreground galaxies and SDSS lensing measurements found evidence that the discrepancy extends to large scales, where astrophysical explanations are disfavored. This study revisits that claim with DECADE lensing data. Relative to SDSS, the new measurements reduce the large-scale tension while leaving small-scale measurements mostly unchanged, favoring a scale-dependent discrepancy rather than establishing its cause. Implications for the standard cosmological model remain conditional on ruling out astrophysical effects and measurement systematics.
PublicGalaxies bend the light of more distant galaxies, allowing astronomers to test ideas about galaxy formation and the universe. Predictions for this lensing signal tend to be about 20–40% stronger than observations, mainly at small separations. An earlier study suggested that the mismatch also persists at large separations, where effects related to galaxy physics are less likely to explain it. Using new lensing measurements from DECADE, this study finds less disagreement at large separations than measurements from SDSS showed, while the small-separation measurements remain mostly unchanged. The findings favor a mismatch that depends on separation, but do not settle its cause. A challenge to the standard model of cosmology would require first excluding astrophysical explanations and measurement problems.
Young explorerA galaxy can bend light from a galaxy behind it. Scientists often predict more bending than they measure, especially close to the galaxy doing the bending. New measurements show less disagreement farther away, but about the same disagreement close by. This suggests the puzzle changes with distance. Scientists still do not know whether the problem is in their ideas about galaxies, their measurements, or their bigger picture of the universe.
Flavio Tonioni
AstronomerThis theoretical work derives a no-go result for future cosmic horizons in time-dependent compactifications. Such compactifications evade the setting of the Gibbons/Maldacena-Nuñez no-de Sitter theorem and can support eternal acceleration, but the higher-dimensional strong energy condition alone does not generally exclude future horizons. The authors show that a strengthened strong energy condition excludes lower-dimensional future cosmic horizons when reduction is on a smooth, compact, boundaryless space. For 10- and 11-dimensional supergravities reduced to at least four large spacetime dimensions, sources satisfying the higher-dimensional strong energy condition also satisfy the strengthened condition. The result is conditional on these energy and compactification assumptions, rather than a general exclusion of eternal acceleration.
PublicSome mathematical models with extra dimensions can describe a universe whose expansion keeps accelerating forever. This paper asks whether those models can also produce a future cosmic horizon—a limit beyond which signals can never reach an observer. The authors prove that such horizons are ruled out if the model obeys a strengthened condition on matter and energy and its extra dimensions form a smooth, compact space without an edge. For the ten- and eleven-dimensional supergravity theories considered, with at least four large spacetime dimensions remaining, sources obeying the ordinary strong energy condition meet the strengthened requirement too. This is a mathematical restriction on certain models, not an observation of our universe, and it does not rule out everlasting accelerated expansion.
Young explorerScientists used math to study pretend universes with extra directions curled up very small. They showed that, if those curled-up directions are smooth and have no edges, and the stuff in the model follows certain rules, the universe cannot have a future boundary beyond which messages could never reach us. Its stretching could still keep speeding up forever. This is about what the math allows, not something scientists saw in the sky.
Robyn L. Munoz, Christian T. Byrnes, Marco Bruni+1 more
AstronomerUsing three-dimensional, fully nonlinear numerical-relativity simulations of dust collapse in a matter-dominated era, the authors investigate numerical and gauge limitations that often halt evolution before primordial black hole formation. They compare proposed lapse evolution equations, propose an alternative, and show that slicing prescriptions effective in typical black hole simulations require adaptation to cosmology. They also find that the Gamma-driver shift fails under dust shell-focusing and that the appropriate shift damping depends on how well the shell-focusing region is resolved, motivating spatially varying damping in future work. Improved gauge choices extend the simulations substantially, with the best runs approaching black hole formation, but stable evolution through formation is not demonstrated and requires further gauge development.
PublicThe study explores why computer simulations of collapsing matter in the early universe often stop working before a primordial black hole can form. In three-dimensional simulations, the researchers test and improve the mathematical choices that control how time is tracked and how the computational grid moves. They find that methods commonly used for black hole simulations need changes in an expanding-universe setting, and that a standard grid-motion method fails where the collapsing matter focuses together. Their improvements let simulations run much further, with the best cases getting close to forming a black hole. They have not yet demonstrated stable simulations through black hole formation; further changes are needed, including a proposed adjustment that would vary the grid-motion damping from place to place.
Young explorerThe researchers used a computer to pretend that matter in the early universe was squeezing together and might make a black hole. The computer often got stuck before that happened. They tried better ways to keep track of time and move the computer's grid as the matter squeezed together. This helped the pretend collapse go further, almost to making a black hole. But they still need to improve the computer's rules to keep it working as a black hole forms.
Christian Dioguardi
AstronomerThe authors propose a slow-roll inflation model in metric-affine gravity, with the connection independent of the metric. Requiring that only the Einstein-Hilbert term break three of four connection shift symmetries replaces the usual metric-affine Starobinsky term with the square of the invariant scalar curvature. The theory propagates only the graviton and one healthy scalaron, whose potential approaches a plateau polynomially as U ≃ U0(1 − μ²/χ²), with μ = √6 M_P. Fixing α ≃ 2 × 10^8 from the scalar amplitude leaves no free parameters in the model, although predictions depend on the assumed number of inflationary e-folds N*. At leading order, n_s ≃ 1 − 3/(2N*) and r ≃ 2√3 N*^(−3/2). Exact slow-roll calculations give n_s = 0.968–0.974 and r decreasing from 0.011 to 0.008 for N* = 50–60. The authors report agreement with current data and predict a tensor signal within reach of next-generation B-mode measurements; this is not a detection.
PublicThis theoretical study proposes a model of inflation, an early period of rapid cosmic expansion, using a form of gravity that treats spacetime geometry and its connection as independent. Mathematical symmetry requirements leave gravity with one additional scalar component that can drive inflation. After setting one coefficient using the amplitude of primordial fluctuations, the model has no remaining adjustable parameters, though its predictions depend on how long inflation lasted. For the duration range considered, its predictions agree with current data. The authors also predict a gravitational-wave signature that could be tested by the next generation of measurements of a polarization pattern called B-modes. Agreement with existing data does not establish that this model describes the universe.
Young explorerScientists made a math idea about how the universe might have grown very fast when it was very young. Their idea fits what measurements currently allow, but that does not prove it is right. It also says there could be a special pattern in light from the early universe. Future measurements might be able to look for that pattern and test the idea.
Ngo Phuc Duc Loc
AstronomerThe authors conjecture that the Universe may be configured so that the black hole information paradox cannot be physically realized. In standard ΛCDM, an infinite cosmic lifetime allows even the most massive black holes eventually to evaporate. Motivated by recent DESI results that they interpret as suggestive of dynamical dark energy, the authors instead consider a finite-lifetime Universe ending in a Big Crunch. In that scenario, even the lightest confirmed black hole, with mass of order one solar mass, might not evaporate before cosmic collapse. They derive a lower bound on black hole mass as a function of cosmic lifetime for their proposed avoidance of the paradox and report resulting predictions. Neither a future Big Crunch nor the conjectured avoidance of the paradox is established by the abstract.
PublicCould the Universe end before black holes have time to disappear? This paper proposes that possibility as a way to keep the black hole information paradox—a puzzle about information when black holes evaporate—from ever playing out in reality. The standard cosmological model gives the Universe an infinite future, but the authors interpret recent DESI findings as suggesting that dark energy may change over time. They consider a possible future collapse, or Big Crunch, which might occur before even the lightest confirmed black holes could evaporate. They calculate how the minimum black hole mass needed for this proposal depends on the Universe’s lifetime. This is a conjecture, not evidence that the Universe will collapse or that the information puzzle has been solved.
Young explorerBlack holes might slowly fade away, and scientists have a puzzle about what happens to information when they do. This paper asks: what if the Universe ends before any black hole has time to fade away completely? The researchers work out how heavy black holes would need to be for that idea to work. It is a possible idea, not something we know will happen.
Donald Liveoak, Anshuman Maharana, James D. Wells
AstronomerThis theoretical study develops a framework for calculating how dark matter relic abundances in thermalized hidden sectors depend on the inflaton branching ratio B into a sector. The framework introduces an effective Planck mass into the hidden-sector Boltzmann equations and is applied to freeze-out and freeze-in WIMPs and multicomponent dark matter. The authors find that the fractional energy density in freeze-out relics, in both single- and multicomponent models, and in monopoles produced by second-order phase transitions scales as B^(1/4). These populations may therefore overclose the Universe even for B much smaller than one. In contrast, freeze-in relic energy density scales as B^(5/4), becoming cosmologically irrelevant for sufficiently small B. The paper also discusses the cumulative implications of many hidden sectors. These are model-based results, not observational detections.
PublicThe paper explores theoretical hidden sectors that could contain dark matter. Their supply of energy depends partly on how often the inflaton, associated with the early Universe, transfers energy into them. The researchers develop a calculation method for sectors whose particles have reached thermal equilibrium. They find that giving a sector only a tiny share of the inflaton's energy does not necessarily prevent it from producing too much dark matter: the abundance of certain relic particles and objects called monopoles decreases only slowly as that share shrinks. Dark matter produced through a different process, called freeze-in, decreases much faster and can become cosmologically unimportant. The authors also discuss what having many hidden sectors could imply. The study concerns theoretical models, not evidence that these sectors exist.
Young explorerImagine the young Universe sharing energy with hidden rooms that might hold dark matter. Scientists used math to ask what happens if a room gets only a tiny share. In their models, some kinds of dark matter could still leave too much stuff in the Universe. Other kinds would become too scarce to matter. This is an idea studied with math, not a discovery of real hidden rooms.
Joshua Williamson, Niall Jeffrey, Lorne Whiteway
AstronomerThe authors introduce a gauge-equivariant spherical mesh CNN architecture tailored to HEALPix, using steerable filters, parallel transport, and spin-weighted features. Its convolutions are provably SO(3)-equivariant subject to a band-limit; full-network SO(3)-invariance errors reach the percent level or below and are controlled by hyperparameters. Benchmark results show the highest accuracy among compared methods for dense gradient regression, with competitive performance in cosmic microwave background foreground removal and denoising. In cosmological lensing simulation-based inference, the method produces the tightest posteriors among the comparisons at matched simulation count. These are methodological and benchmark results, not new astronomical observations. By building rotational symmetry into the architecture, the approach reduces the need to learn that symmetry from training simulations. The authors propose broader applications to generative modeling and inference on spherical data.
PublicA new neural-network design handles data mapped onto a sphere, including maps of the sky. It builds in the rule that rotating a map should transform its features consistently, rather than requiring the network to learn that rule from many examples. The underlying operations have an exact mathematical guarantee under a stated limit on the map’s angular detail, although complete networks still show small rotation-related errors, at the percent level or below. In benchmark tests, the method excelled at one map-analysis task and was competitive at cleaning cosmic microwave background maps. In a cosmological lensing inference test, it gave the tightest parameter estimates among the methods compared using the same number of simulations. These tests support its usefulness for simulation-intensive analysis; they are not new observations of the universe.
Young explorerImagine turning a ball with a picture on it. The picture is still the same, just turned around. Researchers made a computer helper that uses this rule when studying maps on a ball, like maps of the sky. In tests, it did some jobs better than other helpers and some about as well. It can still make small mistakes. This is a new way to study maps, not a discovery of something new in space.
Kai Lehman, Jameson Dong, Carolina Cuesta-Lazaro+5 more
AstronomerThis methods paper introduces ENFR, Evidence Networks with Flow-matched References, for fast, amortized estimation of absolute Bayesian evidence in likelihood-based and simulation-based inference. The method learns Bayes factors relative to a flow-matched reference and recovers absolute evidence from those ratios. Evidence can serve as a goodness-of-fit or model-misspecification statistic, inducing a minimum-volume level-alpha test. Across the applications examined, the authors report improved evidence estimation over a flow-based baseline and the best performance among the density-estimation methods benchmarked; these comparisons do not establish universal superiority. They also introduce and provide a proof for an architecture that jointly learns the individual evidences of multiple models, and demonstrate performance and scaling on data from several scientific applications. The abstract reports a methodological advance, not an astronomical observational finding.
PublicScientists need ways to check whether their models adequately describe data, especially when using simulations to infer unknown quantities. Bayesian evidence is useful for this purpose but is difficult to calculate. The authors introduce ENFR, a machine-learning method that estimates evidence itself rather than only ratios comparing two models. It first learns comparisons with a specially learned reference, then uses those comparisons to recover evidence estimates. In the applications tested, it outperformed the baseline and the other density-estimation methods considered. The authors also present a mathematically supported design for estimating evidence for several models together. These are results from method demonstrations and benchmarks, not a new discovery about the universe or a guarantee of success on every problem.
Young explorerScientists make models to help explain what they see, but checking those models can be hard. The researchers made a computer helper that estimates a score for checking a model against data. It did better than the other methods they tried in their tests, but that does not mean it will always be best.
Marios Kalomenopoulos, Riccardo Barbieri, Sadegh Khochfar+2 more
AstronomerThis simulation study tests H0 inference from gravitational-wave events without electromagnetic counterparts using high-resolution cosmological simulations with realistic clustering. The assumed O5 LVK + LIGO India network has binary-black-hole sky localisation of order 60 square degrees, distance uncertainty of order 10%, and a range of about 1600 Mpc/h. With clustering, the H0 posterior clearly recovers the input value with as few as 40 events; uniform catalogues remain largely unconstrained even with 100 events. Catalogues with 25% completeness can be competitive with complete catalogues, while 50% completeness gives statistically similar performance to complete catalogues with only 40 events. Within this setup, the authors conclude that improving GW detection capabilities is more beneficial than increasing galaxy-catalogue completeness. Physical weights add no significant constraining power beyond clustering. Luminosity-distance errors contribute more for smaller localisation cones, and events within roughly 100 Mpc/h give about twice the precision of the more distant sample extending to roughly 1600 Mpc/h. The authors report no H0-posterior bias from the prior range and robustness to the modelling choices tested. These are simulation results under assumed detector capabilities, not measurements from O5 observations.
PublicCould gravitational waves from merging black holes help measure how fast the Universe is expanding, even when no accompanying light is detected? This study explores that possibility in cosmological simulations, assuming a future gravitational-wave detector network. The key advantage is that galaxies gather in clusters rather than being spread evenly. Including that clustering allowed the analysis to recover the simulation’s input expansion rate with just 40 events, whereas an evenly distributed galaxy catalogue left it poorly constrained even with 100. A catalogue containing only half the galaxies performed statistically similarly to a complete one with 40 events; even 25% completeness could be competitive. Under the study’s assumptions, improving gravitational-wave detection was more valuable than making galaxy lists more complete. Nearby events also gave better precision. These findings describe simulated performance, not an expansion-rate measurement from real observations.
Young explorerWhen black holes join together, they make ripples in space. Scientists used computer-made universes to test whether those ripples could help tell how fast the Universe is growing, even without a flash of light. Galaxies bunch together, and those bunches helped the test find the answer put into the computer. Even a galaxy list with many galaxies missing could work well. This was a computer test, not a new measurement of the real Universe.
Bao-Min Gu, Yu-Peng Zhang, Fu-Wen Shu+1 more
AstronomerThis theoretical study examines self-resonance preheating in a deformed alpha-attractor T-model with a Gaussian potential feature near the minimum, far from the end of inflation. Linear analysis shows feature-dependent changes to resonance bands and Floquet charts, primarily through the localized modification of the potential curvature. Fully nonlinear lattice simulations find only modest changes to gradient-energy transfer during resonance, but substantial changes to subsequent oscillon evolution. Increasing the magnitude of the dimensionless feature amplitude h suppresses compact-oscillon formation and persistence, reducing their abundance and energy fraction. Within the directly resolved range, lifetimes decrease nonlinearly with increasing absolute h; negative h generally yields shorter lifetimes than positive h of equal magnitude. Total-energy and internal-gradient-energy diagnostics agree on these trends. Simulated gravitational-wave emission is dominated by the resonant stage and strongly suppressed after oscillon formation, while the feature enhances the spectrum's high-frequency tail. Qualitative differences in post-inflationary expansion appear within the simulated window, but a complete reheating description requires external couplings and higher-resolution simulations.
PublicComputer simulations explore how a localized change in the potential governing the inflaton, the field associated with cosmic inflation, could affect the early universe after inflation ends. This field can break into compact, localized clumps called oscillons. In the model studied, strengthening a Gaussian-shaped feature in the potential has only a modest effect on energy transfer during the initial resonance, but makes the later clumps fewer, less persistent, and responsible for a smaller share of the energy. Over the range directly followed in the simulations, stronger features shorten clump lifetimes nonlinearly, with negative feature amplitudes generally shortening them more than equally strong positive amplitudes. The simulated gravitational waves arise mainly during the resonance stage, with much weaker emission after the clumps form; the feature also strengthens the high-frequency end of the spectrum. These are model results, not observations. The simulations show differences in how the universe expands after inflation, but additional interactions and higher-resolution calculations are needed for a complete account of reheating.
Young explorerScientists used a computer to explore what might have happened just after the universe's very early burst of stretching. In their model, a field can gather into little clumps of energy. Changing the rules for how that field moves made fewer clumps survive, and stronger changes generally made them last less time. The model also made tiny ripples in space, mostly before the clumps formed. This is something the computer model shows, not something scientists have seen happen. They need more detailed models to tell the whole story.
April Qiu Cheng, Jonathan Gair
AstronomerThis methodological study relates gravitational-wave–galaxy two-point cross-correlations to galaxy-catalog dark-siren inference, which marginalizes over possible hosts when no electromagnetic counterpart is available. The authors show that a 2×2-point analysis extends the harmonic-space angular component of the galaxy-catalog method by marginalizing over the unknown galaxy field rather than treating it as fixed and uniform. They clarify the assumptions needed for application to GW data and present a strategy for incorporating GW measurement errors into the likelihood. Combining cross-correlations with spectral-siren information from GW rate evolution, mass distributions, and selection effects could exploit the joint constraining power of dark-siren methods. For a future configuration of two Einstein Telescopes and one Cosmic Explorer, they forecast joint precision of 1% on H0 and 5% on Ωm,0 from cross-correlations alone after two years. These are projected capabilities, not current measurements. The method offers a potentially scalable alternative to canonical hierarchical Bayesian population inference, but requires large-number statistics unavailable in current GW catalogs.
PublicGravitational waves can help measure the universe even when no accompanying light reveals which galaxy produced them. This paper explains how to compare the statistical patterns of gravitational-wave sources and galaxies, without needing to identify their host galaxies. It connects that approach to other gravitational-wave methods and describes how to account for measurement errors. For a future network of two Einstein Telescopes and one Cosmic Explorer, the authors project that two years of data could jointly measure the cosmic expansion parameter H0 to 1% precision and the matter-density parameter Ωm,0 to 5%. Those are forecasts, not measurements already made. The approach needs many sources, and current gravitational-wave catalogs are too small.
Young explorerSpace can make tiny ripples that tell us about the universe. Sometimes we cannot tell which galaxy a ripple came from. Scientists describe a way to compare patterns of many ripples with patterns of galaxies, instead of finding each ripple’s home. They think future detectors could use this to learn how fast the universe grows and how much matter it has. There are not enough recorded ripples to do this yet.
Ashu Kushwaha, Teruaki Suyama
AstronomerThis theoretical analysis translates up-to-date limits on primordial black hole (PBH) abundances into upper bounds on primordial curvature power spectra with narrow and broad peaks. It assumes PBH formation through the collapse of large density perturbations during radiation domination, which gives an approximate correspondence between PBH mass and the scale of the curvature-spectrum peak, indirectly probing the last e-folds of inflation. The authors compare Press-Schechter and peak-theory calculations, account for the nonlinear curvature–density relation, and assess window-function and transfer-function effects. Including nonspherical collapse significantly increases the inferred power-spectrum amplitude because PBH formation requires a higher density threshold. Press-Schechter and peak theory yield largely similar constraints for the monochromatic case but differ for broad primordial spectra. The treatment covers monochromatic and extended PBH mass functions using existing methodologies. These are model-dependent constraints derived from abundance bounds, not a detection of PBHs or a direct measurement of primordial fluctuations; statistical and collapse-model uncertainties remain important.
PublicThe study uses existing limits on how many primordial black holes could exist to constrain how strong small-scale fluctuations in the early Universe could have been. Such black holes could have formed when unusually dense regions collapsed, and their masses would approximately indicate the scales of the fluctuations that produced them. The researchers compare different mathematical descriptions of this process rather than report a black hole discovery. They find that allowing collapsing regions to be nonspherical raises the fluctuation amplitudes inferred from the abundance limits. Two statistical methods give similar constraints when all black holes have one mass, but differ when the underlying fluctuations span a broad range of scales. The results highlight how uncertainty about black hole formation affects what these limits can reveal about inflation.
Young explorerLong ago, very crowded patches of the young Universe might have squeezed into black holes. Scientists used limits on how many such black holes there could be to work out how strong the early bumps might have been. Different ways of doing the sums give different answers, so the answer is still uncertain.
Anna Bencke, Nanoom Lee, Marc Kamionkowski
AstronomerMotivated by DESI measurements suggesting a late-time matter density approximately 5% below the Planck-inferred value, this study tests dark matter decay into two less massive, warm daughter states. The models vary the decaying fraction f, decay rate Γ, and retained mass fraction ε, using CLASSIER-DDM to evolve perturbations through an integral-equation method. Analysis of DESI DR2 BAO and Planck 2018 CMB data, including lensing, finds no preference for these models over ΛCDM because CMB lensing tightly constrains daughter-particle velocity kicks. For f ≃ 0.5, the reported 1σ kick-velocity constraints are of order 10⁻²–10⁻³ times the speed of light for decays shortly after recombination through today. Allowed models can nevertheless suppress small-scale power enough to potentially address dwarf-galaxy anomalies. The authors further suggest that CMB lensing will constrain proposed DESI explanations involving decay into one massive and one massless particle.
PublicRecent DESI measurements suggest that the universe’s late-time matter density is about 5% lower than the value inferred from Planck observations. The researchers investigated whether dark matter breaking down into two lighter particles could help explain this difference. Comparing these models with DESI and Planck data, they found that the decay models are not favored over the standard cosmological model. A key restriction comes from how matter bends light from the early universe: these measurements tightly limit the speeds that the newly produced particles could receive from the decay. Some allowed models could still reduce matter clustering on small scales enough to potentially help explain puzzles involving dwarf galaxies, but the study does not establish that they solve those puzzles. The authors also suggest that similar light-bending measurements will restrict proposals in which dark matter decays into one massive and one massless particle.
Young explorerScientists wondered whether dark matter, a kind of matter we cannot see, might break into two lighter bits. They tested this idea using measurements of the universe, including how matter bends very old light. The measurements did not favor this idea over the usual explanation, and they put tight limits on how fast the new bits could move. Some versions of the idea might still help explain puzzles about tiny galaxies, but scientists have not shown that they do.
D. Forero-Sánchez, S. Novell-Masot, H. Gil-Marín+48 more
AstronomerThe analysis combines DESI DR1 full-shape measurements, including the LRG bispectrum, with DESI DR2 BAO. Mock-based cross-covariances are included, and ShapeFit compression mitigates prior-volume effects in extensions to ΛCDM. Within ΛCDM, adding the bispectrum raises the inferred clustering amplitudes to σ8 = 0.868 ± 0.026 and S8 = 0.880 ± 0.028, from 0.822 ± 0.034 and 0.827 ± 0.036 in the previous power-spectrum-only analysis, reducing marginalized uncertainties by 24% and 22%. In w0waCDM, DESI-only constraints shift toward ΛCDM and are consistent with it within 1σ in the w0–wa plane. DESI+CMB gives a 2.8σ preference for evolving dark energy; the supernova-only addition gives 1.6σ, while the full combination gives 3.1σ. Overall, the bispectrum weakens evidence for evolving dark energy relative to power-spectrum-only analyses. For DESI-only neutrino-mass constraints, adding the bispectrum shifts the posterior peak into the positive region, yielding Σmν = 0.26 ± 0.18 eV and a 95% upper limit of 0.59 eV; this is not a firm detection. The modified-gravity constraint μ0 = 0.12 ± 0.51 remains consistent with general relativity.
PublicResearchers combined DESI measurements of galaxy clustering with measurements of a characteristic cosmic distance scale. Adding a statistic called the bispectrum tightened estimates of how strongly matter clusters and shifted their best-fit values upward. The implications for dark energy depend on which observations are combined: DESI alone remains consistent with a cosmological constant, while adding other observations produces varying levels of preference for dark energy that changes over time. Including the bispectrum weakens that preference compared with analyses that omit it, so these findings do not establish that dark energy evolves. The added information also improves sensitivity to the total mass of neutrinos and moves its preferred value above zero, but the uncertainty remains substantial. A test of modified gravity is consistent with general relativity.
Young explorerScientists studied patterns in where galaxies are. Looking at the patterns in an extra way helped them make some estimates more precise. They also looked for clues about whether dark energy, which is connected to the universe’s expansion, changes over time. Different sets of clues gave different answers, so they cannot say for sure that it changes. They found a possible clue about the mass of tiny particles called neutrinos, but that answer is still uncertain too.
Hongrui Feng, Yudong Luo, Toshitaka Kajino+2 more
AstronomerThe study models how changes in the Higgs vacuum expectation value (VEV) affect electroweak and strong interaction rates during big bang nucleosynthesis (BBN). It finds a strong negative correlation between the primordial helium-4 abundance and the Higgs VEV. A VEV 1.58% above its current value during BBN can reconcile the EMPRESS helium-4 abundance, deuterium inferred from high-redshift quasar absorption spectra, and Spite-plateau lithium. However, this fit requires a baryon-to-photon ratio inconsistent with the CMB determination, implying a need for nonstandard evolution between BBN and recombination. A smaller, 0.2% increase can partially alleviate the cosmic lithium problem while maintaining CMB consistency; stellar depletion could potentially explain the remaining discrepancy. These are conditional modeling results, not observational evidence that the Higgs VEV changed.
PublicThe researchers explore whether changing the Higgs field’s background value in the early universe could help explain the observed amounts of helium, deuterium and lithium. Their calculations include effects on both the weak and strong nuclear interactions and predict less helium-4 for a larger Higgs value. A value 1.58% higher than today’s during early element formation could bring the three element abundances into agreement with observations. But that scenario requires a ratio of ordinary matter particles to photons that differs from the value inferred from the cosmic microwave background, so it would also require nonstandard cosmic evolution afterward. A smaller increase of 0.2% could ease, but not eliminate, the lithium mismatch while remaining consistent with the microwave background. Lithium depletion in stars might explain the remaining difference. The study does not establish that either change actually happened.
Young explorerWhen the universe was very young, it made light kinds of matter, including helium and lithium. Scientists used calculations to ask what would happen if something called the Higgs field had been a little different then. One change could help match the amounts we see, but it would not fit clues from the universe’s old light unless the universe also changed in an unusual way later. A smaller change could help with the lithium puzzle and still fit that old light, but it would not solve the whole puzzle. Stars might explain the rest by using up some lithium. These are ideas tested with calculations, not proof that the Higgs field really changed.
Surajit Das, Surojit Dalui, Bum-Hoon Lee+1 more
AstronomerThis theoretical study computes numerical-kludge gravitational waveforms for chaotic and non-chaotic extreme-mass-ratio inspiral orbits in a model comprising a stellar-mass object subject to an external harmonic-oscillator potential and a supermassive Schwarzschild-like black hole embedded in a Dehnen-type dark matter halo. Building on earlier dynamical analyses, the authors find that the chaotic trajectories considered produce broader, finite-width frequency spectra, irregular waveform modulations with comparatively large strain excursions, and altered energy-emission characteristics relative to non-chaotic trajectories. These are numerical model results, not observed gravitational-wave signatures. The authors discuss possible detectability with LISA, TianQin, and Taiji, but the abstract does not establish detection prospects quantitatively.
PublicCould chaotic motion near a black hole leave a recognizable pattern in gravitational waves? Researchers calculated signals from a model in which a stellar-mass object orbits a supermassive black hole surrounded by dark matter, while also feeling an additional confining force. For the chaotic paths they studied, the calculated waves covered a broader range of frequencies, varied more irregularly, showed comparatively larger swings in strain, and carried energy differently than waves from orderly paths. These findings come from numerical calculations, not observations. The researchers discuss whether future observatories such as LISA, TianQin, and Taiji might detect such patterns, but detection remains a possibility rather than a demonstrated result.
Young explorerScientists used a computer to study a small space object going around a much bigger black hole, with invisible matter around it and an extra force keeping the little object confined. They calculated the tiny ripples this motion would make in space. When the object's path was chaotic, the ripples changed less regularly and had a wider mix of rhythms than those from orderly paths. This happened in their computer model; they have not seen these ripples in space. Future space detectors might be able to look for them.
Abhishek Roy, Prasenjit Sanyal, Stefano Scopel
AstronomerThis theoretical study scans the five parameters of dark-photon inelastic dark matter: the lighter Majorana-state mass, the positive splitting to a heavier Majorana state, the dark-photon mass, kinetic mixing with Standard Model hypercharge, and the dark gauge coupling. It integrates relic-abundance constraints with direct, indirect, astrophysical, and accelerator search prospects beyond previously studied benchmarks. The scan finds that a dark coupling equal to the electromagnetic coupling is not disfavored. Where the lighter state reproduces the observed dark matter relic density, direct and indirect searches are found to be kinematically inaccessible. At its projected luminosity, FASER could probe or exclude model parameter space with a lighter-state mass below approximately 7 GeV, a splitting of roughly 100–300 MeV, and a dark-photon mass below approximately 25 GeV. The proposed FASER 2 upgrade could significantly extend this reach. Long-lived-particle searches and neutron-star capture of the lighter state probe partially overlapping parameter space. These are model-scan findings and sensitivity projections, not a dark matter detection.
PublicThe researchers investigate a possible dark matter model containing two related particles and a dark photon that links their hidden sector to ordinary matter. They explore the model's five adjustable parameters rather than only a few selected examples. Their calculations find that a dark-force coupling equal to the electromagnetic coupling remains viable, contrary to what some narrower studies may suggest. When the lighter particle accounts for the observed dark matter abundance, the direct and indirect searches considered are blocked by the model's reaction kinematics. Accelerator searches offer another route: with its projected collision exposure, the LHC's FASER detector could test or rule out a region of the model with particular particle masses and mass differences. The proposed FASER 2 upgrade could broaden that reach substantially. Searches involving dark matter capture in neutron stars would test some of the same possibilities. The work predicts where searches could be useful; it does not report finding dark matter.
Young explorerScientists are testing an idea about what dark matter might be made of. Their idea has two kinds of hidden particles and another particle that connects their hidden world to ordinary matter. They used calculations to try many versions of the idea. Some ways of looking would not work when the idea gives the right amount of dark matter. But a detector called FASER might be able to check some versions, and a proposed bigger detector could check more. Very dense stars called neutron stars might also help test some of the same ideas. Nobody found these hidden particles in this study.
Marco Figliolia, Petr Jizba, Gaetano Lambiase
AstronomerThis theoretical study revisits Jacobson’s thermodynamic derivation of gravity using generalized, non-extensive horizon entropy S(A). Treating entropy as a coarse-grained constitutive quantity, the authors find that only its local slope s0 at a reference area enters macroscopic dynamics in their local Rindler-wedge construction. Reformulating the Clausius relation as stationarity of a Massieu functional at fixed Unruh temperature identifies s0 as controlling the effective gravitational coupling; linear area entropy recovers Einstein’s equations with G_eff = 1/(4s0). As a separate consistency check, a scalar-response extension with internal entropy production reproduces f(R) field equations. For an adopted power-law entropy, the authors propose a Topological Calibration Principle that fixes the reference area using the Gauss–Bonnet theorem. For compact cross-sections allowed by the theory or boundary conditions, this produces an Euler-characteristic-dependent effective coupling. Consistency requirements constrain departures from extensivity, while the resulting scale-dependent modifications could have observable cosmological signatures. These are theoretical implications, not reported observational detections.
PublicCan gravity be understood through the thermodynamics of horizons? This theoretical paper explores that question using entropy laws more general than simple proportionality to horizon area. In the authors’ construction, the way entropy changes near a chosen reference area controls the effective strength of gravity. The familiar area-proportional law recovers Einstein’s equations. The authors also propose using a mathematical relation involving a horizon cross-section’s geometry and topology to choose that reference area. For certain allowed compact cross-sections, this makes the effective gravitational coupling depend on topology. Their framework constrains possible departures from the usual entropy law and suggests effects that might be observable in cosmology, but the abstract reports no observational confirmation.
Young explorerScientists tried a new mathematical way to understand gravity, the pull that brings things together. They studied how rules about heat and information at special boundaries might describe that pull. One familiar rule gives Einstein’s gravity. Different rules might change it, but this paper does not show that nature really uses those different rules.
