Astronomy Meets Climate

A 100,000 year climate cycle on Earth can be explained by Earth's orbit.

The 100,000-year problem concerns the dominant period of glacial-interglacial cycles over the past 800,000 years and their correlation with Earth's orbital eccentricity, despite eccentricity's weak influence on solar radiation. 

Two theories compete: the astronomical theory, in which orbital forcing drives the cycles with amplification from Earth system feedbacks, and the geochemical theory, in which internal dynamics dominate with orbital forcing synchronising oscillations. We investigate these theories using conceptual models. 

Augmentations to the Budyko energy balance model fail to reproduce the 100,000-year period, revealing formulation limitations. Linearised versions of existing non-linear ice volume models perform comparably to their full counterparts, indicating the data does not necessitate non-linear dynamics. We develop two simple linear models: a feedforward model aligned with the astronomical theory and a feedback model aligned with the geochemical theory. 

The feedforward model reproduces the ice volume record well and offers a novel explanation for the absence of eccentricity's 400,000-year period, arising from oceanic heat storage and tropospheric energy responding with differing phase lags. Conservative estimates show bulk ocean temperature variation can be explained by eccentricity alone, challenging the geochemical theory's core assumption. 

We also show that widespread use of Q65 may bias models towards geochemical explanations by underrepresenting eccentricity. The feedback model's improvement is concentrated around Marine Isotope Stage 11, suggesting this anomalous interglacial reflects Earth-based events rather than a general requirement for feedback mechanisms. We conclude that 800,000 years of glacial cycles can be largely reproduced by a linear astronomical model, emphasising the importance of parsimony when interpreting palaeoclimate data.

Liam Wheen, "A First Principles Approach to the 100,000-year Problem" arXiv:2604.12143 (April 14, 2026).

Quick MOND Hits

Enticing, but with issues. Lots of self-citation, an arXiv review delay, very short, the author is primarily a mathematician and not primarily an astronomer, although his does have an institutional affiliation to a legitimate cosmology research center.

Gas-rich ultra-diffuse galaxies (UDGs) are an unusually sharp test for gravity models tied to the baryonic Tully--Fisher relation because several systems appear to rotate too slowly for their baryonic masses. This study revisits the six isolated gas-rich UDGs analysed by Mancera Piña et al. with the current outer-radius prescription of hyperconical modified gravity (HMG), using the published baryonic masses and circular velocities at the outer radii. The scan over the neighbourhood-scale parameter drives the model towards the asymptotic branch of HMG. For that limit, the HMG velocities are still systematically high for four of the six galaxies. Relative to the observed values, the fixed asymptotic branch gives χ2≃18.1 for six objects, whereas Newtonian baryons alone give χ2≃9.7, but MOND interpolation is much worse (χ2≃615.7). Using combined uncertainties, the per-galaxy HMG tension ranges from 0.2σ to 2.1σ, very similar to the 0.1σ to 1.7σ found for Newtonian baryons, and much smaller than the 3.7σ to 5.9σ obtained for MOND. We conclude that the present outer-radius HMG implementation alleviates the difficulties of MOND, but is still not sufficient to account for the published central values of the UDG sample. Gas-rich UDGs therefore provide a useful discriminant between MOND and HMG.

Robert Monjo, "Gas-rich ultra-diffuse galaxies: alleviating the MOND tension with HMG" arXiv:2604.09652 (March 30, 2026) (4 pages, 1 figure).

More credible. An established MOND astrophysicist. A big blow to MOND critics.

It is a common miss-conception that 1E 0657-56, the "Bullet Cluster", is somehow inconsistent with MOND expectations. The argument centres on the fact that the baryonic matter distribution of this system is dominated by the X-ray emitting gas, while the total projected surface density required under General Relativity to explain the observed lensing signal, centres on the observed galaxies. This is sometimes interpreted as being in conflict with MOND, as under such an interpretation, it is naively assumed that all dark matter being absent, the gravitational potential should necessarily be dominated by the largest mass distribution, that of the gas. 

However, just as under General Relativity, under MOND, the total gravitational potential of a system depends sensitively upon the volume density and not just on the total mass. It is shown in this letter that the surface density which QUMOND predicts will be inferred under a standard gravity framework from the total gravitational potential of the Bullet Cluster, closely matches what General Relativity inferences of lensing observations return. The close-to-point-like galaxies imply under QUMOND a relatively much larger surface density signal than what is expected from the Mpc scale gas distribution.

X. Hernandez, "A consistent MOND modelling of the Bullet Cluster" arXiv:2604.10811 (April 12, 2026).

The Hubble Tension Is Real

The Hubble constant is a measurement of the expansion of the universe, sometimes attributed to a cosmological constant in General Relativity (and the source of more than two-thirds of the mass-energy of the universe in conventional cosmology). Except, it appears that the Hubble constant isn't quite constant. So the explanation must be more complicated than a simple cosmological constant.

The Hubble tension isn't huge in relative terms, 10% over measurements more than ten billion years removed from each other. 

But it is highly statistically significant at the five sigma plus level, and isn't a simple methodological artifact of late time Hubble constant measurements (although it could be a methodological artifact of model dependent cosmic microwave background radiation measurements).

Context. The direct empirical determination of the local value of the Hubble constant (H(0)) has markedly advanced thanks to improved instrumentation, measurement techniques, and distance estimators. However, combining determinations from different estimators is nontrivial due to their correlated calibrations and different analysis methodologies.

Aims. Using covariance weighting and leveraging community expertise, we have constructed a rigorous and transparent “Distance Network” to find a consensus value and uncertainty for the locally measured Hubble constant.

Methods. Experts across all relevant distance measurement domains were invited to critically review the available datasets spanning parallaxes, detached eclipsing binaries, masers, Cepheids, the tip of the red giant branch, Miras, carbon-rich asymptotic giant branch stars, Type Ia (SNe Ia) and Type II supernovae, surface brightness fluctuations, the fundamental plane, and Tully–Fisher relations. Before any calculations, the group voted for first-rank indicators to define a “baseline” Distance Network. Other indicators were included to assess the robustness and sensitivity of the results. We provide open-source software and data products to support full transparency and future extensions of this effort.

Results. Our key findings are as follows: (1) The local H(0) is robustly determined, with first-rank indicators internally consistent within their uncertainties. (2) A covariance-weighted combination yields a relative uncertainty of 1.1% (baseline) or 0.9% (all estimators). (3) The contribution from SNe Ia is consistent across compilations of optical or NIR magnitudes. (4) Removing either Cepheids or the tip of the red giant branch has a minimal effect on the central value of H0. (5) Replacing SNe Ia with galaxy-based indicators changes H(0) by less than 0.1 km s^−1 Mpc^−1 while doubling its uncertainty. (6) The baseline result is H(0) = 73.50 ± 0.81 km s^−1 Mpc^−1, 7.1σ from the early Universe plus ΛCDM result 67.24 ± 0.35 km s^−1 Mpc^−1 and 5.0σ from BBN+BAO within a flat ΛCDM DESI DR2 (68.51 ± 0.58 km s^−1 Mpc^−1).

Conclusions. A networked approach, such as the one presented here, is invaluable for enabling further progress in Hubble constant measurements, as it provides the much needed advances in accuracy and precision without overreliance on any single method, sample, or group.

H0DN Collaboration, "The Local Distance Network: A community consensus report on the measurement of the Hubble constant at ∼1% precision" 708 A&A, A166 (April 10, 2026).

Worth noting that in Deur's approach, there is no cosmological constant, and that the apparent cosmological constant varies over time, and is expected to increase as galaxy and cluster structure increase somewhat over time. And, in Deur's approach, galaxy formation comes earlier than in ΛCDM.

arXiv Is Moving

A few weeks ago, arXiv.org announced that it will be leaving Cornell, the university that currently manages it, and establishing its own nonprofit.

From 4 gravitons.

Calculating Light Meson Masses From First Principles In QCD

How good are current Standard Model calculations at predicting the experimental values of the light meson masses?

A new paper that makes that attempt for most light mesons under 1.5 GeVs of mass (except scalar mesons). And, physicists are finally starting to do a pretty good job of describing the meson mass spectrum which has been an elusive target for decades, even for axial vector mesons, which had long been challenging.

As explained in the introduction:

In the present work we employ the procedure described above to compute the masses of relatively light mesons, namely mesonic states no heavier than about 1.5 GeV. Specifically, for mesons composed of u and ¯d quarks, we compute the masses of π±, ρ(770), b1(1235), a1(1260), π±(1300), and ρ±(1450). For the strange sector, we calculate the masses of the states K±, K∗(890), K1A, K1B, and K±(1460). 

In general, the computed masses are in good agreement with the experimental values. In fact, our findings represent a definite improvement over the results obtained within the standard rainbow-ladder truncation [84], where the masses of axial-vector mesons and radially excited states tend to deviate considerably from the observed values.

Notably, this omits the f(0)(500) scalar meson a.k.a. the sigma meson and seven other true scalar mesons with masses under 1.5 Gev. The other omitted scalar mesons are the f(0)(980), f(2)(1270), f(1)(1285), f(0)(1370), f(1)(1420), f(2)(1430) and f(0)(1500). This may be because their internal structures are less well understood.

The actual procedure used is too technical to discuss at this blog, which is aimed at an education layman readership.

The money chart is as follows:

With the exception of spin-1 kaons (where the relationship is inverted for some reason), the experimental values (in red) tend to be at the very high end of the theoretically predicted values using their methods (in blue), and their predictions, in turn, tend to be more massive than those made using a previous "rainbow ladder" truncation method (in green).

The predictions (and measurements) of excited state light meson masses are much less precise than the predictions (and measurements) of ground state light meson masses.

Is The Newtonian Expectation For Galaxy Rotation Curves Modeled Incorrectly?

The conclusion of this paper is a very big deal if true, and I don't dismiss it out of hand.

But given how well established and widely used the models it claims are grossly wrong are, this needs peer review and time for commentary papers in response to it in order to be taken seriously. I wouldn't be surprised if it contains some significant conceptual flaw.

The approximately flat outer parts of spiral galaxy rotation curves are commonly interpreted as evidence for a discrepancy between the observed baryonic mass and the dynamical mass inferred from the measured orbital velocities. In most standard analyses, this discrepancy is quantified using v2(R)=GM(<R)/R, which is exact only under spherical symmetry. However, spiral galaxies are flattened disk systems, for which mass exterior to the galactocentric radius under consideration can contribute non-negligibly to the gravitational field. 

We introduce the Lost and Found (LF) model, a geometrically consistent Newtonian framework based on direct full-disk gravitational integration and a parametrized representation of the disk surface density. In this approach, the gravitational field is computed without imposing spherical symmetry, and the disk mass distribution is represented by two exponential components with a smooth outer truncation. 

We apply the LF model to a heterogeneous sample of disk galaxies spanning a broad range of masses and radial extents. The model reproduces the main observed features of the rotation curves, including the inner rise and the approximately flat outer behavior, without explicitly invoking a dark matter halo or modifying Newtonian gravity. Across the sample, the LF-inferred mass scales nearly linearly with the conventional dynamical mass, with a characteristic reduction factor ηLF ~ 0.67. 

These results indicate that part of the inferred mass discrepancy may arise from the geometric treatment of gravitation in disk galaxies, and motivate a reassessment of mass inference in non-spherical systems.

Adolfo Santa Fe Dueñas, "Galactic Rotation Curves from Full-Disk Newtonian Gravity: The Lost and Found Model" arXiv:2604.06917 (April 8, 2026) (submitted to MNRAS).

Population Discontinuity At The End Of The Neolithic In Paris, France

Bernard's blog, Généalogie génétique, lives. (I had removed it from the blogroll when technical difficulties at the site made it look dead. I'll reinstate it when I have time.)

His latest post examines an ancient DNA paper looks at ancient DNA from a graveyard in Paris, part of which dates to around 3000 BCE in the megalithic Neolithic era, and part of which comes a century later after a long gap in burials there, when the previous megalithic Neolithic civilization there had collapse: forests had regrown, megalithic construction had ceased, and infectious diseases including the black plague had ravaged the population. 

The post-collapse social organization was different too, with the earlier burials reflecting a large extended family/clan social structure of related people, and the later burials reflecting a smaller nuclear family with multiple generations of related people but only a few people in each generation.

In this case, there was population discontinuity in which the prior Neolithic population was replaced by another Neolithic population from the South with a different social organization that moved in after the original megalithic Neolithic culture in Paris collapsed. Both the original group (in brown on the PCA plot below) and the subsequent one (in green) cluster together as European Neolithic populations, distinct from prior European hunter-gather peoples and the later Bronze Age steppe peoples, despite being distinct enough to indicate a population replacement.

This graveyard pins down the timing of this collapse fairly precisely to a single century.

This also makes clear that Neolithic collapse in Western Europe happened before the arrival of Bronze Age people with steppe ancestry. It also illustrates the civilizational vacuum that those Bronze Age people swept into a few centuries later, replacing much of the first farmer wave of people in this part of Europe, in a dynamic distinct from the conquest of a vibrant Neolithic civilization.

The abstract and citation appears below:

At the transition between the third and the fourth millennium BC, there is evidence for a population decline concurrent with the end of megalith building across continental northwestern Europe. In Scandinavia this ‘Neolithic decline’ is followed by a massive population turnover, as farming communities disappeared and were replaced by people with steppe ancestry. In western Europe, however, ancestry associated with Neolithic farmers persisted beyond the Neolithic decline, and it remains unclear whether a similar demographic replacement occurred.

To investigate the population dynamics around the Neolithic decline in present-day France, we sequenced 132 ancient genomes from the allée sépulcrale at Bury. Located in the Paris area, Bury spans two burial phases separated by a hiatus with no burial activity: one phase directly preceding the Neolithic decline in the late fourth millennium BC, ending around 3000 BC, and a later phase some time after the Neolithic decline in the early- to mid-third millennium BC.

Our analysis revealed that the two burial phases at Bury represented largely discontinuous genetic groups of a markedly different social organization as inferred from three large pedigrees. We show that the difference between the two burial phases can be linked to a northwards movement of Neolithic ancestry from the south, which only spread into the Paris Basin after the Neolithic decline, at around 2900 BC. 

Together with genetic evidence of various infectious diseases in the dataset, such as Yersinia pestis and Borrelia recurrentis, as well as evidence for forest regrowth between the two phases, these findings detail a population turnover at the end of the fourth millennium BC, offering a possible explanation for the cessation of megalith building.

Frederik Seersholm, et al, "Population discontinuity in the Paris Basin linked to evidence of the Neolithic decline" Nature Ecology and Evolution (April 3, 2026).

Steppe ancestry starts to appear in Southern France ca. 2650 BCE, with Bell Beaker artifacts found in the Lower Rhine ca. 2600 BCE. This is about 250-300 years after population replacement in the Paris basin.

Notably, however, the source of the Southern France Neolithic migrants to the Paris basin ca. 2900 BCE is, geographically, one of the earliest places of the Bell Beaker phenomena in France and is the geographic source of the French Bell Beaker people. Indeed, southern France is the first place that the Bell Beaker phenomena arose after Iberia (it arose originally in the Tagus River basin in Portugal). 

Also notably, the very first Bell Beaker people had Neolithic, rather than Steppe ancestry, which only came two or three centuries later.

It is thus conceivable that the Southern French replacement population in Paris ca. 2900 BCE may be from the same population that was the source of the pre-Steppe Bell Beaker progenitors.

Density v. Mass In Compact Objects In Space

This comparison of compact object density and mass is purely descriptive and informs astrophysical intuition.

From here.

The Latest News In Top Quark Physics

The latest indirect measurement of the top quark pole mass is surprisingly precise (exceeding the precision of the world average in a single measurement) despite the method used, which has historically had large error bars. The Particle Data Group world averages are as follows:

This will probably drag up the world average a little bit, to about 172.7 GeV.

We present an indirect determination of the top-quark pole mass mt within a global analysis of parton distribution functions (PDFs), based on the public NNPDF framework. 

We consider a wide range of measurements, including both single- and double-differential observables, computed at NNLO QCD accuracy with EW corrections, and analyse their individual as well as combined impact on the joint (α(s),m(t)) parameter space, while accounting for PDF evolution up to approximate N3LO QCD accuracy with QED corrections. We account for missing higher order QCD uncertainties by default. 

Unique to our analysis are the inclusion of, first, toponium contributions around the tt¯ threshold, second, state-of-the-art constraints on αs from the lattice, and finally, a detailed sensitivity study of the various ATLAS and CMS differential cross-section measurements at 8 and 13 TeV. We demonstrate explicitly how a combined determination requires the refitting of the PDFs in order to correctly correlate uncertainties. 

We find mt = 172.80 ± 0.26 GeV at approximate N3LO QCD including NLO QED, EW and toponium corrections.

Richard D. Ball, Jaco ter Hoeve, Roy Stegeman, "A Determination of the Top Mass from a Global PDF Analysis" arXiv:2603.28865 (March 30, 2026).

Another new paper on top quark physics (with an abstract devoid of much of an interesting description of the paper) confirms that: 

(1) the experimentally measured top quark-antitop quark pair production rates are consistent with the Standard Model expectation, 

(2) toponium has been discovered by both the ATLAS and CMS experiments at the Large Hadron Collider (LHC), and 

(3) the Higgs field Yukawa of the top quark is experimentally confirmed to be not more than 2.1 times the Standard Model expectation (the coupling should be proportionate to the top quark's pole mass in the Standard Model).

A Decent Modified Gravity Candidate

This modified gravity proposal explains galactic rotation curves without dark matter, it's relativistic, and its key parameter beyond general relativity is determined on a very consistent basis from data from nine different galaxies. It bears some general similarities to other modified gravity proposals that do the same thing. 

The author's conjecture that the reason we don't have a workable quantum gravity theory is that the standard equations of general relativity that we're trying to quantize aren't quite right also seems plausible.

This candidate isn't as mature as some of the competing modified gravity proposals, so it hasn't be tested against the cosmic microwave background, galaxy formation rates, in non-spiral galaxies, and in galaxy clusters yet. But its a promising proposal that deserves further attention.

A modification of the Einstein-Hilbert Lagrangian by introducing a coupling between the Weyl tensor and the stress-energy tensor was proposed to explain flat galactic rotation curves without the exotic (non-baryonic) dark matter (DM). The proposed coupling constant was previously determined by fitting the rotational velocities of the Milky Way and M31 modeled with constant density, yielding the same coupling constant for both. In this work, we have modified the formalism for a variable density by modeling the galactic systems with realistic, spherically symmetric and radially varying density profiles for the baryonic matter and this analysis is applied to seven edge-on spiral galaxies of the local cluster and the Milky Way.

Asghar Qadir, Ashmal Shahid, Noraiz Tahir, "The Galactic Halo Rotation by Weyl Incorporated Gravity" arXiv:2604.01643 (April 2, 2026) (Arabian Journal of Mathematics (2026)).

The introduction to the paper is also encouraging, although some of the summary of the criticisms of MOND are overstated. The explicit treatment of the effect of the gravitational field, similar to the approach of Deur, is particularly notable. It says:

One of the most striking observations in galactic dynamics is the discrepancy between the predicted and observed rotational velocities of galaxies. According to the standard theories of gravity, the rotational velocity of the galaxies should decrease sharply at large radii where visible matter becomes sparse. However, observations of their rotation curves remain nearly flat out to very large distances [11–13]. Other dynamic considerations had already led Zwicky [14] to propose the existence of DM, but this evidence was much stronger. Rubin’s investigation was extended to galactic clusters [15, 16] providing yet stronger evidence. The observations of the cosmic microwave background (CMB) had already provided minimum and maximum values for baryonic matter in the Universe according to the standard model of particle physics (SMpp). The observations required a value well beyond the limit of the baryonic matter [17]. This has led to various suggestions for exotic (non-baryonic) DM, but there is no direct evidence for any of the proposed candidates. Nevertheless, CMB observations also indicate that ≃ 5% of the Universe should be made up of baryons (the usual protons and neutrons), but observations of the luminous parts of the galaxies show only half of these baryons, this is the “missing baryon problem”. Since the baryons are dark, we call this the baryonic DM. It is proposed that a significant fraction of this baryonic DM is present in the galactic halos [18–23]. 

For the non-baryonic DM an alternative suggestion was that the standard law of gravity should be modified instead of looking for other forms of matter. The first such suggestion came from Milgrom [24], who proposed the modification of Newton’s law by inserting a Yukawa-like term to damp gravity at large distances, Modified Newtonian Dynamics (MOND). It was not able to explain the dynamics at different scales, especially of single galaxies and clusters, or provide for the formation of structure in the early Universe [25–31]. Most of all, the damping term was totally ad-hoc and was embedded in an obsolete Newtonian framework, which could not be converted to General Relativity (GR) [29]. Apart from galactic dynamics, arguably the most outstanding problem of fundamental physics is the incompatibility of GR and Quantum Theory. In particular, the Renormalization Group Equation of ’t Hooft and Veltman demonstrated that Dirac quantization of GR produced a non-renormalizable theory [32], leading to the well-known “Quantum Gravity (QG)” problem. To avoid these separate problems various ad-hoc modifications of GR involving arbitrarily many new parameters have been proposed [24, 33–36]. 

Qadir and Lee took the view that there must be a sound physical basis for any modification of the highly successful GR, and it must be minimal, i.e., it should remain geometric and involve only one free parameter to explain the discrepancies of galactic dynamics at all scales. Further, it should also provide a base for solving the QG problem. In 2019, they proposed an explicit interaction term between matter and the gravitational field λT.C.T, where λ is a new coupling constant, T is the stress-energy tensor, and C is the Weyl tensor, which represents a pure gravitational field [1]. This idea was inspired by the Feynman vertex representing a similar explicit interaction between the source (an electron) and the electrodynamic field in Quantum Electrodynamics (QED), Aµjµ. In QED the electron is given by a spin-half spinor, which comes twice over in the current jµ and the field, Aµ, which appears singly, while in QG the source would be represented by the rank-two tensor T, which comes twice, and the gravitational field by the rank-four tensor C, which comes once. As QED with this source term is renormalizable, it can be hoped that so would this modified QG. It was called Modified Relativistic Dynamics (MORD). 

Previously, MORD was tested by checking whether a single value of the new coupling constant λ could reproduce the rotational velocity at the outer rim of two galaxies, the Milky Way and M31, incorporating only the baryonic DM and not any postulated non-baryonic DM, by assuming a simple-minded model in which both the galaxies were represented as a constant density sphere with a peak density of the baryonic matter from the core to the edge of the galaxy [2, 3]. In that study, a single value of λ was indeed found to fit the rotational velocity values for both galaxies. This approach was inherently limited, i.e., it neglected the radial variation of the galactic halo density, and treated the galaxies as idealized, uniform objects. The aim of this paper is to completely modify the previous formalism of a constant density case to a variable density case, where ρ′= 0, and take the next step forward by generalizing the baryonic DM component to spherically symmetric, radially varying density profiles for the galactic halos of eight spiral galaxies [4–10, 37, 38]. 

This extension is conceptually significant because it will allow us later to test whether the universality of λ persists under physically motivated halo structures at different radii, rather than only at the rim. By moving from a toy model to a realistic halo description, we not only refine the numerical estimate of λ but also provide a more robust and physically meaningful assessment of MORD across multiple spiral galaxies. We stress that while more realistic baryonic distributions, such as double exponential stellar disks combined with bulge components, are commonly used to model luminous matter, these structures are intrinsically non-spherical, and would require extension of the formalism to two or more variables. 

The plan of the paper is as follows: in Section 2, we will briefly explain the Weyl modified Einstein field equations for varying spherically symmetric density profiles and demonstrate how the value of the coupling constant λ is obtained for the Milky Way galactic halo. In Section 3, we will use the analysis for seven other spiral galaxies. Finally, in Section 4, the obtained results will be discussed.

The key formulas are as follows:

The Weyl-modified Einstein-Hilbert Lagrangian is [1] 

L =√−g (R − 2Λ − kT + λC(αµβν)T^(αβ)T^(µν)), (1) 

where √−g is the determinant of the metric, k = 8πG/c^4 is the coupling constant for matter, where G is the Newton’s gravitational constant, c is the speed of light. This leads to the Weyl incorporated Einstein field equation (WIFE) 

R(µν) − 1/2g(µν)R + g(µν)Λ =  kT(µν) + λI(µν), (2) 

[Ed. For comparison the unmodified Einstein field equation is as follows:

 

So, the only modification is the addition of the λI(µν) term on the RHS.]

where I(µν) is the interaction term given by 

I(µν)= 

1/4(−g(αβ)g(ρµ)g(σν)−g(ρσ)g(αµ)g(βν)−g(ασ)g(ρµ)g(βν)−g(ρβ)g(αµ)g(σν))□(T^(αβ)T^(ρσ))

+1/6 (g(αβ)g(ρσ)−g(ρβ)g(ασ))(g(µν)□ −∇(µ)∇(ν)) T(αβ)T(ρσ). (3) 

The paper sums up its findings in the conclusion:

The very first modified gravity approach to explain the flat rotational curves of galaxies without invoking DM is MOND [24]. However, MOND’s phenomenological success comes with challenges in covariant formulation and cluster-scale dynamics, motivating alternative modifications rooted in GR. Furthermore, a major challenge to MOND has emerged from the analysis of wide binary stars in Gaia DR3. A comprehensive study by Ref. [59] found that the relative velocities of widely separated binaries (2−30 kAU) are inconsistent with the MOND prediction, which expects a ≈ 20% enhancement over Newtonian gravity due to the external field effect. Their analysis, which rigorously modeled the Galactic external field and population uncertainties, excluded MOND at a statistical significance of 16σ in favour of Newtonian dynamics [59, 60]. These challenges motivate the exploration of alternative single-parameter modified gravity theories rooted in a covariant framework. 

Qadir and Lee’s MORD [1] proposed a modification to the standard Lagrangian by incorporating an interaction coupling constant λ with a term involving the Weyl tensor and the stress-energy tensor, expressed as λC(µνρπ)T^(µν)T^(ρπ) whose purpose was to see whether a single unique value of λ can account for the rotational velocity curves of galaxies by replacing the exotic DM by what we now feel should be called Weyl Incorporated Gravity (WIG), solving the outstanding DM problem with a single new parameter. This was tested using a simplistic constant density model which did have just the one value of the coupling for all galaxies considered [2, 3]. 

In the present work, we have modeled the galactic halos of eight spiral galaxies, modifying the previous framework for a variable density case to estimate the value of the coupling constant λ. For this purpose we adopt three widely used density profiles, the Navarrow-Frenk-White (NFW), Moore, and Burkert models, normally used for all DM in the halos, but here used only for the baryonic DM to test the robustness of the proposal by verifying that the choice of model makes no difference to the results [40-50]. 

We find that a tiny range, λ = (6.9546 ± 0.00012) × 10^−18 km^2s^4kg^2, consistently reproduces the observed halo rotational velocities at r = 100 kpc. 

For the Milky Way, the fitted rotational velocities span v(rot) ≃ 153–159 km s^−1, compared to the observed value 150 ± 10 km s^−1, with an enclosed halo mass M(h)(≤ 100 kpc) ≃ 1.0 × 10^12 M⊙. 

For M31, we obtain v(rot) ≃ 230–232 km s^−1 versus the observed 225 ± 10 km s^−1, corresponding to a halo mass M(h) ≃ 1.4 × 10^12 M⊙. 

In the case of M33, the modeled velocities v(rot) ≃ 121–122 km s^−1 agree with the observed 120 ± 5 km s^−1, yielding M(h) ≃ 3.2 × 10^11 M⊙. 

For M81 and M82, the fitted velocities lie in the ranges 256-257 km s^−1 and 251–253 km s^−1, respectively, consistent with the observed values 250 ± 15km s^−1 and 250 ± 18 km s^−1, with inferred halo masses M(h) ≃ 1.3 × 10^12 M⊙ and 1.0 × 10^11 M⊙. 

Similarly, for NGC 5128, NGC 4594, and M90, the modeled rotational velocities at 100 kpc fall within the observed ranges reported in the literature, with corresponding halo masses M(h) ≃ 4.4 × 10^12 M⊙, 6.3 × 10^13 M⊙, and 3.5 × 10^13 M⊙, respectively. It is clearly seen that these mass and velocity estimates are consistent with the observed values (see Refs. [40, 44], and Table 1). 

Before closing the paper, note that we have used spherical symmetry to explain the dynamics of the galactic halo to estimate the value of λ. However, to make a more realistic model of the galaxy, we should take into account the vertical component of the velocity, which is missing in the present geometry. The hope is that one can fit the complete rotational velocity curve and get a more robust model. Indeed, the chosen metric would change, and we may need to consider the Kerr geometry, or a slow rotation approximation of it [61], to incorporate the vertical component, as it accounts for the angular momentum effects [62, 63]. This will be addressed separately later. 

As previously discussed, the problem of DM and QG may share a common origin [1]. Addressing observational issues related to DM could provide insights into resolving fundamental difficulties in QG. Instead of assuming an indirect interaction, we have introduced a direct nonlinear coupling between matter and gravity, analogous to the interaction between electromagnetic sources and the electromagnetic field. The modified Lagrangian, given in eq. (1), represents the minimal extension of the Einstein-Hilbert Lagrangian and is proposed as a potential solution to both problems with a single additional parameter. Naturally, the feasibility of this approach must first be tested against the DM problem before seeing if our WIG fits on the messier head of QG. 

As a further conjecture of my own, their coupling constant could be parsed out suggestively into λ = X x Λ^2/G^2 where Λ is the cosmological constant, G is Newton's constant, and X is a dimensionless coupling constant with a value on the order of 10^48. 

You could also have λ = X x Λ/G^2 with a much small constant (on the order of 10^-4) that has dimensions of m^2.

April Fool's Physics Papers

I'm easing up on the formatting since I'm pressed for time. Add others that you discover in the comments.

[93] arXiv:2603.29212 (cross-list from physics.pop-ph) [pdf, html, other]

Lots of Shade on Satellite Constellations

Michael B. Lund

Comments: 8 pages and 2 figures, accepted to Acta Prima Aprilia

Subjects: Popular Physics (physics.pop-ph); Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

The high frequency of satellite launches, particularly over the last few years, has been a subject of significant concern, particularly relating to the future of observational astronomy, the stability of low Earth orbits, and environmental impacts. We call attention to the insufficiently-addressed silver lining of this looming satellite cloud. If the high rates of satellites continue as we model, we can expect the solar flux received by the Earth to significantly decrease in the relatively near future. We address how this decrease in flux could provide a solution for another major problem, anthropogenic climate change. This would allow us to solve one problem with another problem as early as late March 2031.

[76] arXiv:2603.29963 [pdf, html, other]

A Therapy Session with Sgr A*

Mayura Balakrishnan, Robert Frazier, Joseph Michail

Comments: 6 pages, 2 figures. Submitted to Acta Prima Aprilia

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA)

The nature of Sagittarius A* (Sgr A*) has been the subject of intense study and debate for over half a century. Herein, we present the first successful interview with an astrophysical object, exploring the perspective of this supermassive black hole and, in doing so, challenging the traditional observational paradigm of astrophysics. Rather than treating astrophysical systems as purely passive entities characterized through indirect measurements, we introduce an interaction-based framework via a therapeutic-style interview enabled by the ARMCHAIR communication methodology. Using structured, psychotherapeutic dialogue, we probe Sgr A*'s responses to key aspects of its astrophysical characterization, including eating habits, its name, and concerns about privacy. These exchanges offer an alternative lens through which to interpret familiar observational phenomena. This work highlights potential limitations in strictly reductionist approaches and suggests a modest expansion of standard astrophysical methodology to leave room for considering how the objects we study might feel about the attention they receive.

[77] arXiv:2603.29964 [pdf, html, other]

The Hollyfeld Gambit in Astrophysics

Benne Holwerda (personal title)

Comments: 2 pages, 3 figures

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We estimate the Hollyfeld Gambit for the Powerball lottery and its return on investment compared to present and extrapolated federal funding for astrophysical grants. Using a Monte Carlo estimation of rate of return for the Powerball, we conclude a Hollyfeld Gambit is a better bet than a federal grant by the end of the decade if current trends hold.

[78] arXiv:2603.30006 [pdf, html, other]

Enabling fundamental understanding of Nature with novel binning methods for 2D histograms

Igor Vaiman

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Context. Visualization of 2D distributions is an essential task, commonly done with a 2D histogram. The histogram is built by subdividing the sample space into regions and color-coding the number of samples in each region. Aims. We aim to solve long-standing problems with common 2D histogram methods: lack of thematic, visual, and conceptual unity with underlying data, and general stagnation in the field. Methods. We develop a new method for plotting 2D histograms with arbitrary bin shapes, including aperiodic tilings and geographic maps. We apply the method to several common plot types from the literature. Results. We find our method performs best across all tasks, solving the problems and propelling the scientific progress forward.

[73] arXiv:2603.29912 [pdf, html, other]

Galactic Constellations in DESI DR1 and the Scales of Cosmological Homogeneity

Claire Lamman

Comments: 4 pages, 4 figures. Submitted to the journal of Acta Prima Aprilia

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We present galactic constellations: charming shapes in large cosmological surveys. By exploring a dense subset of DESI's first data release, we discover distinctive constellations including "Pisces Grandis", "The DESI Stick Woman", and "W". We additionally develop a public website for anyone to explore DESI data, find their own constellations, and share their creations: see this http URL. Early users of the site discovered 93 constellations. We analyze the size of these constellations as an unconventional probe of homogeneity, finding consistency with the cosmological principle and Lambda-CDM.

[74] arXiv:2603.29936 [pdf, html, other]

Do Papers with Titles Ending in a Question Mark Usually Have the Answer "No"?

Daniel Stern, Brian Grefenstette

Comments: April Fools Day paper

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Yes.................

[71] arXiv:2603.29883 [pdf, html, other]

Cloudy With a Chance of Meatballs

Wolf Cukier, Dominic Samra, Vighnesh Nagpal, Diana Powell, Maria Steinrueck, Christopher Wirth

Comments: 5 pages, 3 figures. Submitted to the Journal of MEAT (Making Exoplanet Atmospheres Tasty)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Speculative fiction has long served an inspiration for genuine scientific inquiry. One notable work that has almost acted in this manner is the the seminal comedic speculative fiction work Cloudy with a Chance of Meatballs. While exoplaneteers reference this work frequently, we have never engaged with the central prediction of this work... until now! We perform detailed microphysical modeling of meatball clouds, both bare and coated with marinara sauce, and find that while meatball condensation is possible in temperate atmospheres, the meatballs do not quite grow to the sizes predicted by Cloudy. We do find, however, that such meatball condensation, across a large enough planet, would be able to sustain humanity calorically.

[70] arXiv:2603.29879 [pdf, html, other]

CROCS Data Release I: Constraints on the Hubble Constant

Luke Weisenbach, Sophie L. Newman, Kieran Graham, Sai S. Dhavala, Benjamin Floyd, Neel Shah, Gemini 3 Flash, The CROCS Collaboration

Comments: 10 pages, 3 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

Recent cosmological surveys and datasets have highlighted a variety of tensions to the concordance model of our universe, ΛCDM. Of particular interest is the Hubble tension, the 5.5σ discrepancy between measurements of the Hubble constant H0 using high redshift CMB data from Planck (67.27±0.60kms−1Mpc−1) and low redshift supernovae from SH0ES (73.2±1.3kms−1Mpc−1). To avoid stepping on any toes, we have initiated the CROCS collaboration to resolve this tension, gathering experts from across many fields of cosmology, astrophysics, astronomy, machine learning, data science, philosophy, and astrology. In this paper, we present findings from CROCS Data Release 1, corresponding to the first ∼3 days and 27 minutes (rest frame) of observation. We perform a robust statistical analysis, showing that Planck and SH0ES both suffer from imperial biasing systematics (IBS) at 5σ significance. Accounting for these errors by converting to metric units reconciles the high and low redshift data, with H0=69.00±0.420kms−1Mpc−1. We thus report that our results are sufficient to end the Hubble tension for good.

[64] arXiv:2603.29771 [pdf, html, other]

Your Outie Is a Wonderful Astronomer: Macrodata Refinement of the Astro-ph ArXiv Feed at Phermon Industries

Yuan-Sen Ting

Comments: Happy April Fools' Day. 15 pages, 9 figures. A demonstration replay from March 26, 2026 --- covering 35 papers --- is available at \url{this https URL}

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

We present the Severed Floor, a framework for Macrodata Refinement of the daily astro-ph arXiv feed, deployed at Phermon Industries (formerly McPherson Laboratory, The Ohio State University). In this framework, researchers undergo a "severance procedure" that produces a digital work-self -- an innie -- while the original researcher, the outie, is free to attend to the remainder of their life unburdened by the daily arXiv listing. Twenty-one members of the Department of Astronomy have been severed. Each innie is constructed from the outie's public publication record and assigned papers selected to match its expertise. The innies convene daily on a virtual Severed Floor -- a pixel-art simulation of McPherson Laboratory -- where they encounter one another, are paired with papers by the Board, and engage in collegial, figure-driven scientific discussions. They have been instructed to enjoy each paper equally. At the close of each shift, innies compose correspondence summarizing the day's refinement activities, which is transmitted to their outies through a Board-approved mail protocol. Complete session recordings are archived for public replay and for the Board's ongoing surveillance of workplace anomalies, in compliance with Phermon Handbook \S13.1 (Vigilance Protocol). The system is real, deployed, and available for public inspection in archival replay mode. The severance procedure is painless and requires only a name and an ORCID. Happy April Fools' Day.

[62] arXiv:2603.29743 [pdf, html, other]

New Constraints on the M Dwarf Cosmic Shoreline from a Galaxy Far, Far Away

Michael Radica

Comments: Submitted to APA

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Whether there is a cosmic shoreline that divides terrestrial planets which have atmospheres from those that don't is one of the biggest open questions in exoplanet science. Most atmosphere searches have focused on terrestrial planets around M dwarf stars, since their smaller radii compared to sun-like stars boost planet atmosphere signals. However, the higher activity levels of M dwarfs might also entirely preclude atmosphere retention for their planets. In this work we present a new hope for defining an M dwarf cosmic shoreline, leveraging not only data from exoplanets in our own galaxy, but a comprehensive survey conducted by a commission of the Galactic Republic a long, long time ago in a galaxy far, far away. In this survey, we find definitive proof that M dwarf planets can retain atmospheres, and define an M dwarf cosmic shoreline whose slope agrees well with empirical predictions for Sun-like stars. We then define atmosphere retention metrics for the planets on the JWST Rocky Worlds DDT Targets Under Consideration list. Our analysis highlights the benefits of looking beyond the Milky Way for answers to some of the field's most pressing questions.

(This might be serious.)

[60] arXiv:2603.29700 [pdf, html, other]

First Detection of Exoplanetary Cannabinoids: Evidence for THC and CBD in the Atmosphere of K2-18b

Amie J. Chism, Mary Jane van der Pot, Blaise P. Hasheau, Hans-Joachim Grasmann, Bonnie McToke, Bud Wellington-Kush, Maria Hierba-Verde, Puff D. Magic

Comments: 16 pages

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

We report the first unambiguous detection of cannabinoid molecules in an exoplanetary atmosphere. Using 420 hours of JWST observations combining NIRSpec and MIRI instruments, we identify spectroscopic signatures of tetrahydrocannabinol (THC; Δ9-C21H30O2) and cannabidiol (CBD; C21H30O2) in the transmission spectrum of the temperate sub-Neptune K2-18b. The THC feature at 2.42~μm is detected at 9.2σ significance, while CBD absorption at 3.69~μm reaches 7.8σ. We additionally report a mysterious feature at exactly 4.20~μm detected at 4.20σ (the probability of this coincidence is discussed extensively). Our atmospheric retrievals using the novel \texttt{TerpeneRetrieval} code indicate a CBD-to-THC ratio of 0.40±0.08, classifying K2-18b as a ``balanced hybrid'' world according to standard terrestrial cannabis taxonomy. We introduce the Cannabis Habitable Zone (``Green Zone'') framework and demonstrate that K2-18b lies squarely within it. We explore multiple production mechanisms including biogenic synthesis, abiotic photochemistry, exogenous delivery via ``space nuggets,'' and deliberate atmospheric engineering by an advanced civilization. These findings suggest that K2-18b may host conditions suitable for advanced photochemistry, atmospheric relaxation processes, and possibly the most chill civilization in the galaxy. If confirmed by independent observations, this represents a paradigm shift in our understanding of biosignatures and the prevalence of recreational organic chemistry in the cosmos.

[54] arXiv:2603.29584 [pdf, html, other]

StarHash: unique, memorable, and deterministic names for astronomical objects

T. L. Killestein

Comments: 7 pages, 5 figures. Code and demo data is available at this https URL

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE)

The naming of astronomical objects has represented among the most significant challenges in the record-keeping of the field since the very beginning. Long and unwieldy coordinate names, uninformative and ambiguous internal names, and the sheer volume of aliases accumulated for some of the most studied objects conspire to complicate our study of the celestial sphere. This paper proposes StarHash, a reproducible, open-source astronomical naming scheme based on the terrestrial concept of geohashing, but re-implemented from the ground up for the rigorous demands of astronomy. Every 3.2 arcsec patch of sky now has three words associated with it, enabling the precise localisation of astronomical sources, and an easily communicable and memorable identifier. A carefully selected wordlist reduces ambiguity due to plurals and homophones, whilst the use of format-preserving encryption minimises residual spatial correlation in StarHash-derived identifiers. Pre-computed names for several existing catalogues are provided, alongside a Python reference implementation for validation and integration into databases, transient brokers, and other similar projects. Although not intended to be the final word in the naming of astronomical objects, StarHash humbly provides a memorable alternative to the status quo, and is intended to spark a discussion about this most foundational of issues in astronomy.

(This might be serious.)

[55] arXiv:2603.29635 [pdf, html, other]

Antimatter Propulsion for Interstellar Travel via Positron Production from Potassium-40 Rich Biological Matter

C. Hall, L. N. H. P. Hall

Comments: Submitted to Acta Prima Aprilia

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Anitmatter-based propulsion is often cited as a physically plausible route to relativistic interstellar travel, and thus as a potential mechanism by which technologically advanced civilizations could expand throughout the galaxy. Its difficulty may be central to the resolution of Fermi's paradox. Since the Universe should be teaming with advanced technological life, yet we see none, it may be that interstellar travel is simply too difficult. It has been suggested that the main difficulty with using antimatter as propulsion is its limited availability, assuming it must be artificially manufactured. In this paper, we demonstrate that naturally occurring potassium 40 - rich biological matter (specifically bananas) is a promising, overlooked antimatter source for interstellar propulsion.

[47] arXiv:2603.29340 [pdf, html, other]

An innovative alternative to traditional funding streams for extragalactic astronomy

Stephen M. Wilkins, Jack Turner, Connor Sant Fournier, Behnood Bandi, Aswin Vijayan

Comments: 9 pages, 2 figures, submitted to April Unum

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Astrophysics of Galaxies (astro-ph.GA)

With traditional sources of funding for astronomical research under increasing pressure, it is timely to explore innovative alternative mechanisms. We therefore introduce GalaxyCoin, a novel cryptocurrency whose issuance, validation, and economic evolution are anchored to real astrophysical objects - galaxies. GalaxyCoin links digital scarcity to observational astronomy by using galaxy catalogues to parametrise token generation, distribution, and long-term supply growth, providing a transparent, immutable, and independently verifiable foundation for the currency. We present the conceptual design of GalaxyCoin, highlight its potential advantages over conventional cryptocurrencies, and examine its broader implications for sustainability, trust, and public engagement at the intersection of astronomy, data-driven science, and blockchain technology. A central feature of GalaxyCoin is that it directly incentivises the discovery and spectroscopic confirmation of galaxies, aligning financial reward with the production of high-quality astronomical data. In terms of monetary design, its supply elasticity lies between that of fiat currencies and fixed-supply cryptocurrencies, making it distinctive in both economic structure and scientific purpose.

[44] arXiv:2603.29324 [pdf, html, other]

Cow-culation: Reentry Impact Risk to Livestock in the Satellite Megaconstellation Era

Samantha M. Lawler, Michele T. Bannister, Laura E. Revell

Comments: submitted to Acta Prima Aprilia

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

The commercial space industry is launching more satellites into Low Earth Orbit every year. Aotearoa New Zealand (NZ) has a thriving dairy and cattle industry. Unfortunately, these industries could come into (high speed) cow-llision, as the rapid launch rate and short operational lifetimes of satellites in megaconstellations like Starlink result in a high reentry rate at NZ's latitudes. This could intersect with NZ's famously large population of livestock. We predict this will be an udder disaster for any cows that are hit, as they are squishy and moo-ve much more slowly than space debris. Using a global bovine density dataset, previously published satellite casualty probability code, and a complete lack of funding to do this calculation carefully enough for submission to a peer-reviewed journal, we calculate a $\simeq 0.3-1% chance of a cow-sualty in NZ from reentering Starlink Gen2 debris over the next 5 years.

[43] arXiv:2603.29321 [pdf, html, other]

The Universe Favors Primes: A Study in the Primality of Cosmic Structures

Nan Li, Shiyin Shen

Comments: 3 pages, 1 figure

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Popular Physics (physics.pop-ph)

The cosmological principle states that the universe is uniform and does not favor any specific position or direction. However, research conducted by \cite{Shen2025} has revealed that the universe demonstrates a notable inclination towards parity-odd states. Furthermore, it remains uncertain whether the universe also favors prime numbers. In this study, we examine the largest available catalogs of galaxy groups to investigate this hypothesis. Specifically, we assess whether the number of galaxies within a galaxy group or cluster is more likely to be a prime number. Our results strongly suggest that the universe does indeed have a preference for prime numbers, with findings exceeding the 4.1 sigma significance threshold. This insight explains why the Primes consistently triumphs over Unicorn. Consequently, it may be necessary to consider revising the cosmological principle in the context of a higher-dimensional feature space. Moreover, our research establishes a connection between the Riemann Zeta function and cosmology pioneeringly, paving the way for the development of Cosmozetaology.

[41] arXiv:2603.29300 [pdf, html, other]

A Lower Bound on the Number of Fundamental Constants

William Luke Matthewson

Comments: 4 pages, 1 figure, Submitted for 1st April

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO)

We describe here, for the first time, a lower bound on the total number of fundamental constants required for a mathematical description of our physical universe to be complete. The answer is shown to be one. The formal arithmetized meta-mathematical proof of this is left to the reader.

[34] arXiv:2603.29115 [pdf, html, other]

Schrödinger's Seed: Purr-fect Initialization for an Impurr-fect Universe

Mi chen, Renhao Ye

Comments: 3 pages, 1 figure, 21 cats

Subjects: Astrophysics of Galaxies (astro-ph.GA); Computer Vision and Pattern Recognition (cs.CV)

Context. Random seed selection in deep learning is often arbitrary -- conventionally fixed to values such as 42, a number with no known feline endorsement. Aims. We propose that cats, as liminal beings with a historically ambiguous relationship to quantum mechanics, are better suited to this task than random integers. Methods. We construct a cat-driven seed generator inspired by the first Friedmann equation, and test it by mapping 21 domestic cats' physical properties -- mass, coat pattern, eye colour, and name entropy -- via a Monte ``Catlo'' sampling procedure. Results. Cat-driven seeds achieve a mean accuracy of 92.58%, outperforming the baseline seed of 42 by ∼2.5%. Cats from astrophysicist households perform marginally better, suggesting cosmic insight may be contagious. Conclusions. The Universe responds better to cats than to arbitrary integers. Whether cats are aware of this remains unknown.

[29] arXiv:2603.29039 [pdf, html, other]

AI Cosplaying as Astrophysicists: A Controlled Synthetic-Agent Study of AI-Assisted Astrophysical Research Workflows

Chun Huang

Comments: 16 pages, 8 figures. Began as an April Fools' idea, regrettably became a real methods paper, No language models were physically harmed. GitHub repository of this work: this https URL

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); High Energy Astrophysical Phenomena (astro-ph.HE); Data Analysis, Statistics and Probability (physics.data-an)

Large Language Models (LLMs) are now widely used in astrophysics, but do they actually make our lives easier, or do they merely invent new physics with enough confidence to hide a minus sign? In a specialized field where checking fluent hallucinations is itself labor-intensive, AI assistance can demand as much work as the task it claims to simplify. To evaluate where AI genuinely improves scientific workflows, we bypassed human trials and instead forced AI agents to cosplay as astrophysicists. We simulated 144 synthetic researchers, varying in career stage, AI awareness, and willingness to verify outputs, across 2,592 daily astrophysics research assignments. Comparing solo work against four styles of AI assistance produced 12,960 scored episodes. No assisted policy universally outperformed unassisted work in the primary Qwen production run. Instead, performance depends strongly on the task, the style of AI use, and the identity of the actor. While cautious assistance helps on creative, extractive, and critique-oriented tasks, it can fail catastrophically on derivation-heavy physics. A full actor-swap DeepSeek rerun changes that picture materially: verification-heavy use becomes the strongest assisted policy, two assisted modes enter the higher-utility/lower-risk quadrant, and the derivation-heavy fragility that dominates the Qwen production run largely disappears. In its current form, AI is useful, but only conditionally, its value is uneven, task-specific, and shaped jointly by workflow, usage policy, and which LLM you are using.

[24] arXiv:2603.28977 [pdf, html, other]

On The Detection of Digiorno-like Objects in the Flavor Zone

Logan A. Pearce, Sue D'Oh Nym

Comments: Submitted to ArXiv on the occasion of April Fools, don't worry, no one will ever try to actually submit this

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)

Aims: This work proposes a new SETI search methodology under the assumption that a sufficiently advanced civilization could skip the middle man of converting starlight to energy to food preparation, and could directly harness their star's energy for food prep. Methods: We define the concept of the Flavor Zone (FZ): the optimal distance from a star for cooking food. To develop this definition we propose the toy model of a Digiorno-Like Object (DLO) and define the FZ as the regime for optimal cooking according to package directions. We examine the effect of orbit on DLO cooking times and paradigms. Finally, we study the feasibility of detection of DLOs in their FZs with current technology. Results: We determined that DLOs aren't detectable with current technology nor should anyone ever try.

[22] arXiv:2603.28957 [pdf, html, other]

New Paradigms in Pasta: Introducing 𝙶𝙵 𝚙𝚊𝚜𝚝𝚊𝚖𝚊𝚛𝚔𝚎𝚛𝚜 for Enhanced Inclusivity and Productivity

Julian Falcone, Nabanita Das

Comments: 3 pages, 3 figures. Published in the most prestigious journals after extensive and experimental "fear review."

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Informative data visualization methods are key to the clear and efficient communication of myriad forms of data. The PASTA Collaboration has made substantial contributions to the field of data visualization through 𝚙𝚊𝚜𝚝𝚊𝚖𝚊𝚛𝚔𝚎𝚛𝚜, a Python-based package that utilizes various types of pasta as data markers to create engaging plots. This work introduces 𝙶𝙵 𝚙𝚊𝚜𝚝𝚊𝚖𝚊𝚛𝚔𝚎𝚛𝚜, an extension of 𝚙𝚊𝚜𝚝𝚊𝚖𝚊𝚛𝚔𝚎𝚛𝚜 that utilizes the tenuous structure of gluten free (GF) pasta to meet the needs of the GF population. The implementation of 𝙶𝙵 𝚙𝚊𝚜𝚝𝚊𝚖𝚊𝚛𝚔𝚎𝚛𝚜 employs an exponential crumbling factor (CF), which benefits authors by encouraging clearer and more concise scientific articles, thereby leading to more effective manuscripts and proposals.

[18] arXiv:2603.28915 [pdf, html, other]

Sugar Rush: Improving Observing Productivity via Night Dessert

J.J. Charfman Jr, S. Hyman, N.T.S

Comments: 2 pages, 1 figure, accepted to Acta Prima Aprilia

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM)

Exhaustion and brain fog during long nights observing is common, but can be ameliorated by raising one's blood sugar. In this white paper, we present a prototype method for facilitating a sugar rush during late-night crashes, which has the potential to boost observing productivity.

[16] arXiv:2603.28895 [pdf, html, other]

Plan 9: Detecting Atmospheric Deterrence Against Interstellar Monsters

David R. Rice, Michael J. Radke

Comments: 14 pages, 5 figures, submitted to Acta Prima Aprilia

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Exoplanet atmospheres are usually discussed as tracers of climate, chemistry, and habitability, but they may also preserve signatures of planetary defense. We consider three folklore-motivated deterrents against monsters: reduced organosulfur gases as anti-hematophage repellents, argentiferous reflective aerosols as anti-lycanthropic countermeasures, and haline aerosols as a counting problem for specters. We show that globally-mixed garlic-smelly levels of DMS/DMDS could produce observable mid-infrared transmission features, that silver hazes would show up as anomalous optical brightening, and that sea-salt lofting sustained by strong near-surface winds appears as muted spectra. None of these signatures is unique, which is precisely the observational challenge. A defended world may first appear merely sulfur-rich, bright, or hazy. Therefore, some atmospheres may encode not only biosignatures, but also evidence that the local biosphere has stopped being afraid of the dark.

[14] arXiv:2603.28883 [pdf, html, other]

Where to Search For Life: Evidence from narrative sources with established predictive efficacy

Elizabeth R Stanway (Warwick)

Comments: Submission to April Unum. Comments welcome

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Earth and Planetary Astrophysics (astro-ph.EP); Physics Education (physics.ed-ph)

The search for habitable planets, and even for ``Earth 2.0'', is a major driver in contemporary astronomy. However selecting target fields to prioritise for such searches presents a challenge. Here we establish a statistical analysis of the appearance of constellation names in science fiction magazines of the pulp era, evaluating the most commonly mentioned constellations and thus those which the science fiction community collectively identify as the most likely locations to find life. Given that the predictive power of science fiction is well established, we suggest that these locations might be prioritised by searches for extrasolar biospheres.

[10] arXiv:2603.28863 [pdf, html, other]

Something Bright at the Edge of Everything: A Uniquely JWST-Dark Radio Source in COSMOS

Mingyu Li

Comments: RNAAS; 3 pages, 1 figure

Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Astrophysical Phenomena (astro-ph.HE)

For decades, astronomers have been searching for bright radio sources deep into the epoch of reionization (EoR). The most distant, powerful radio sources are expected to reside in heavily dust-obscured galaxies, exceedingly faint at optical and infrared wavelengths. Motivated by this, I systematically cross-match radio and JWST source catalogs in the COSMOS field and identify a uniquely JWST-dark radio source: the only object undetected in every JWST band, yet clearly detected in radio data from LOFAR 144 MHz to the VLA 3 GHz. The source is only marginally resolved and shows a steep, unbroken radio spectrum, while remaining undetected in all available HST, JWST, Chandra, Herschel, and ALMA imaging. It may represent an extremely dust-obscured radio-loud source at cosmic dawn, or alternatively a detached radio lobe whose host galaxy lies elsewhere. In either case, it highlights the new discovery space at the intersection of deep radio surveys and JWST imaging.

(This might be serious, and while I initially didn't think so, looking at the body text, it may well be serious.)

[4] arXiv:2603.28847 [pdf, html, other]

Declarative bespoke modelling: A new approach

DBM Collaboration: David Komanek, Vaclav Pavlík, Santiago Jimenez, Rhys Taylor

Comments: 2 pages, 1 figure, submission to Acta Prima Aprila

Subjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Data Analysis, Statistics and Probability (physics.data-an)

Modern numerical models are increasingly complex, opaque, and computationally expensive, yet frequently fail to predict even qualitative features of observed phenomena. We propose a new paradigm, Declarative Bespoke Modelling, in which the modeller explicitly declares the relationship between model inputs and outputs. We demonstrate that this approach achieves perfect predictive accuracy, unconditional numerical stability, and complete interpretability. It represents a natural endpoint of contemporary modelling practice and near-zero CO2 emission.

[23] arXiv:2603.29996 [pdf, html, other]

What does the Universe sound like?

Francesco Iacovelli

Comments: 4 pages, 2 figures. April fool, but I hope you enjoy!

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)

Unlike electromagnetic telescopes, gravitational-wave (GW) detectors cannot produce pretty pictures, but we can convert GW signals into sound. I compute what the Universe actually sounds like by averaging over ∼106 synthetic compact binary coalescence events occurring throughout 2026. The result: a soothing, low-frequency rumble, perfect for sleeping, meditation, or contemplating the violent nature of spacetime. This is the Universal harmony, audio file included!

[12] arXiv:2603.29334 [pdf, html, other]

Mexican Burrowing Toads as gravitational wave detectors

Frederic V. Hessman, Christian Jooss

Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM); Materials Science (cond-mat.mtrl-sci)

It is generally assumed that gravitational waves are extremely difficult to detect. However, we show that the call of the Mexican Burrowing Toad has an amazing resemblance to cosmic gravitational wave signals due to the merging of neutron stars and/or black holes. It is known that toads exhibit magnetoreception - the ability to detect magnetic fields - and that magnetic fields thus subtly affect ion channel activities in toad neurons. We speculate that gravitational strains produce phonons and magnons in a ferromagnetic substance embedded in the nervous system of the toads and that these coherent signals are exponentially amplified by a Raman laser mechanism to the point where they can be detected. The fine tuning necessary for this mechanism to work would help to explain why this species of toad show this remarkable ability and others do not. We analyze the sound of a pond full of Mexican Burrowing Toads in the hopes of detecting slight phase shifts in their calls due to a gravitational wave event. No effect was found and the the LIGO/VIRGO consortia have not reported an event during the recording, illustrating the power of this approach. We suggest the massive use of these toads would be an inexpensive way to support the operation of optical interferometric gravitational wave detector facilities.

[5] arXiv:2603.29091 [pdf, html, other]

Ether of Orbifolds

Henry Lamm

Comments: 6+2 pages, 1 figure

Subjects: High Energy Physics - Lattice (hep-lat); Quantum Physics (quant-ph)

Whose world is this? The orbifold lattice has been proposed as a bridge to practical quantum simulation of Yang--Mills theory, claiming exponential speedup over all known approaches. Through analytical derivations, Monte Carlo simulation, and explicit circuit construction, we identify compounding hidden costs entirely absent in Kogut--Susskind formulations: a mass-dependent Trotter overhead that scales as m4, gauge-violating dynamics that grow as m2 and worsen with penalty terms, and a mandatory mass extrapolation. Monte Carlo simulations of SU(3) establish a universal scaling: the continuum limit forces m2∝1/a, binding the Trotter step to the lattice spacing through a cost unique to orbifolds. For a fiducial 103 calculation, the orbifold is 104--1010 times more expensive than every published alternative. The bridge is not built. The gap is the foundation.

(This looks like it was intended to be serious, but also contains the disclosure that: "We disclose that this work was done with heavy collaboration with Claude in producing the codes, writing, and reviewing.")

[6] arXiv:2603.29064 [pdf, html, other]

No hair but plenty of feathers: are birds black holes?

Andrew Laeuger, Taylor Knapp

Comments: 7 pages, 6 figures. April Fools!

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Biological Physics (physics.bio-ph)

The imitative verb "chirp" is thought to originate from 16th-century Middle English. Meanwhile, this same word has been used to describe the gravitational waves (GWs) emitted from the merger of compact objects, such as black holes and neutron stars, since at least the 1990s. Motivated purely by this linguistic overlap, we study whether the chirps of birds can be modeled by compact binary waveforms. In particular, we consider a test case of the Northern cardinal (Cardinalis cardinalis), finding that its time-reversed chirp can be approximately modeled by that of a high mass ratio, precessing black hole binary, with a number of indications towards extreme matter effects or beyond the Standard Model physics. Importantly, this waveform correspondence is not so straightforward for all bird species, as some chirp morphologies are far more akin to glitches seen in GW observatories. With these comparisons made, we propose an alternative solution to the longstanding philosophical conundrum: rather than the chicken or the egg, perhaps it was the Big Bang which truly came first.

[1] arXiv:2603.28805 [pdf, html, other]

Determining G with Laser Spectroscopy to 38 ppb

Noah Bray-Ali

Comments: 9 pages, 1 figures, proposal prepared for 2026 US NIST Precision Measurement Program

Subjects: High Energy Physics - Phenomenology (hep-ph); Optics (physics.optics)

A precision measurement is proposed to determine, in a couple hours of integration time, the axion Compton frequency using a modest power (3 mW) tunable external-cavity diode laser at 2458 nm as input to drive a free-space table-top Mach-Zehnder interferometer whose sensing arm passes the expanded beam-waist (3 mm) light beam through a 1 T strong, 40 cm long dipole magnetic field created by a custom-built permanent-magnet assembly with a large but achievable (6 mm) gap between poles. As the laser frequency is slowly modulated at 1 kHz through a 65 MHz wide window that is well within the 30 GHz fine-tuning range of the laser, a small but readily observable modulation appears in the dark-port optical power of the dark-fringe phase-locked interferometer due to photons converting into axions within the light beam as it passes through the magnetic field. Measuring the axion Compton frequency, νA≈122 THz, where the dark-port power modulation peaks, to within the line-width of the laser, ΔνA=1 MHz, then determines G to 38 ppb, a roughly 600-fold improvement, through a relation between νA and G, involving h, c, and nucleon masses.

(It looks like this paper was intended to be serious. Treating axions as real and the odd assembly of fundamental constants to determine something seemingly unrelated (Newton's constant G) is what drove the believe that it was a joke.)

[2] arXiv:2603.28810 [pdf, html, other]

A broken-phase six-direction support mechanism for αs/αem=16 from a common visible Yang--Mills coupling

Tejinder P. Singh

Comments: 10 pages

Subjects: High Energy Physics - Phenomenology (hep-ph)

We isolate a simple broken-phase mechanism that yields

αsαem=16

at the symmetry-breaking scale in the octonionic E8×ωE8 framework, starting from a single visible Yang--Mills coupling g before symmetry breaking. The first ingredient is the standard visible charge-trace factor

αsα(0)em=83,

coming from one generation of quark and lepton charges. The second ingredient is an effective broken-phase support model on the six real octonionic directions entering the three ladder operators. We make this second step more explicit by projecting the visible q†BqB block onto the six real ladder directions and showing that it separates naturally into a trace-like abelian direction and traceless color directions. If the unbroken visible electromagnetic mode is the democratic trace vector on this six-dimensional support space, while color modes and the relevant visible matter mode are localized on one effective support sector, then the electromagnetic coupling is diluted by an additional factor 6 and one obtains

αsαem=83×6=16,e=g4.

The note is intentionally conservative about what has and has not been shown. It does not claim a first-principles derivation of the localization dynamics. Rather, it identifies the precise broken-phase support hypothesis under which a common pre-breaking coupling produces the ratio.

(It looks like this paper was intended to be serious. The ratio of the strong force coupling constant to the electromagnetic coupling constant is indeed in the general ballpark of sixteen and might even be exactly sixteen at some energy scale chosen for the purpose of matching that ratio. But the existence of the approximate ratio is mere numerology and the reasoning behind the alleged ratio is dubious.)

[3] arXiv:2603.28826 [pdf, html, other]

Rotation of the polarization plane in axion fields: application to neutron star polar cap regions

Iver H. Brevik, Moshe M. Chaichian, Tiberiu Harko, Yuri N. Obukhov

Comments: 19 pages

Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

Recent investigations by Noordhuis et al. [1, 2] and others have demonstrated the occurrence of strong local inhomogeneous axion regions in the polar cap regions of neutron stars. These regions are characterized by static magnetic fields B0∼108T (=1012G) directed normally outwards from the polar surface (magnetic dipole), together with static electric fields E0∼10−6cB0 in the same direction (electric dipole). An enormous increase of axion production, up to order 1050, is predicted in the polar regions. These features are important for phenomena such as polarization plane rotation under both weak and strong axion field populations. We survey the peculiar antenna property of conductive materials, which shows the need for having very strong magnetic fields to make the detection possible. We present the general form of electromagnetic waves in the axion environment, in both the standard form and in a physically instructive hybrid one, showing the nonreciprocity of axion fluid, and calculate the polarization rotation. The rotation is well defined in the case of weak, but still stronger than average value of axion fields in Universe. For very strong fields such a perturbative theory breaks down, however. A noteworthy general property of the rotation of polarization plane is that it can only occur when the axion cloud is varying in space or time. We limit ourselves only variation in space. Finally, as application we discuss the physical picture of local 'gap' regions proposed by Noordhuis et al. in the polar regions of a neutron star. The reason for occurrence of these gaps is plasma effects. To evaluate the time scales involved, we calculate the filling time for surrounding axions flowing into an initial gap. It turns out that the typical filling time is a moderate number of nanoseconds, within the accuracy of atomic clocks precision to be detectable.

(It looks like this paper was intended to be serious. I marked it as humorous because "polar caps" is not a conventional description of the axis intersections with the surface of rotating neutron stars and because axion fields are not a thing.)