For (cosmic) neutrino mass enthusiasts: Peter Graham, Joel Meyers and I have new paper, breaking down why data prefers "negative" masses and how it might be explained with new fields and/or forces. We point to a number of measurements that would clarify the situation arxiv.org/abs/2508.20999

"Putative dark matter particles with masses below around 1 MeV are not ruled out by astronomical observations" Fact check: astrophysics provides a constraint that is 20 orders of magnitude stronger than this new result.

The paper is out here: pole.uchicago.edu/public/data/... Of personal interest: the full range of neutrino masses allowed by neutrino oscillations are now excluded at 98% confidence!

Let the science begin! 🥁 On May 1, NASA’s SPHEREx space observatory began regular science operations, which consist of taking about 3,600 images per day. Read more here: spherex.caltech.edu/news/nasa-s-...

Is dark energy weakening? DESI’s results are ambiguous You've heard the results last week: the DESI collaboration announced evidence for evolving dark energy. But that's not the only interpretation when the full suite of data just doesn't add up. bigthink.com/starts-with-... #space #physics

PSA: when a collaboration whose name starts with DE says they have found evidence for non-standard dark energy, the community should take that interpretation with more skepticism. DESI does not show that w0wa explains there data. Eg neutrino mass remains negative even with w0wa

Dec 31 - Lower bound on primordial non-Gaussianity arxiv.org/abs/1612.00033 Cabass et al. show that inflation predicts a lower bound of equilateral NG of 0.1 x (n_s-1), 3-4 orders of magnitude below the current limits, due to gravity. The search for NG has a set range and target

Dec 30 - CMB Bispectrum modal decomposition arxiv.org/abs/0912.5516 Fergusson et al. define a basis of orthogonal polynomials on the space of CMB 3pt functions, vastly reducing the need to find models on which to build non-Gaussian templates. Planck bounds the first 2000 terms.

Dec 29 - Dispersion Relations & EFT arxiv.org/abs/hep-ph/9... Donoghue shows how to use subtracted dispersion relations to expose the structure of EFT. Specifically, this technique precisely illustrates UV information can be traded to local contact interactions.

Dec 28 - Scattering and CFT Unitarity Bounds arxiv.org/abs/0801.1140 While officially addressing the topic of "unparticles", Grinstein et al. rederive bounds on the dimensions of operators from the unitarity of scattering a weakly coupled spectator off a strongly coupled CFT

Dec 27 - Weinberg Soft Theorems from Weinberg Adiabatic Modes arxiv.org/abs/1602.05196 Mirbabayi & Simonovic show that the photon and graviton soft theorems for scattering in flat space are a consequence of physical long wavelength configurations tied to large diffs (BSM)

Dec 26 - Conformal Invariance of Cosmological Correlators arxiv.org/abs/1108.0874 Creminelli shows that the structure of cosmic observables follows from conformal Ward identities. He gives simple examples at 3- and 4-points that are a starting point for more complex problems

Dec 25 - CMB Peak Locations arxiv.org/abs/1603.03091 Pan et al. use (semi-)analytic methods to model the location of all the CMB peaks at the level of the Planck peak measurements in TTTEEE (<1%). Many corrections are 1-10% and thus are essential for consistency with data.

Dec 24 - Cosmic Bell Inequalities arxiv.org/abs/1508.01082 Maldacena writes down a model of inflation where the statistics of certain hot and cold spots encode the outcome of a Bell-measurement. This shows that the quantum nature of inflation can survive in conventional classical observables

Dec 23 - Analytic CMB Polarization arxiv.org/abs/astro-ph... Zaldarriaga & Harari give a thorough analytic treatment of how polarized scattering affects the evolution of the photon distribution function and the appearance of temperature and polarized CMB anisotropies

Dec 22 - Fat Gravitons and the CC arxiv.org/abs/hep-th/0... arxiv.org/abs/hep-th/0... Sundrum tries to construct a theory of gravity where vacuum loops don't gravitate. This theory is non-local in a non-trivial way in order to avoid the very strong equivalence principle constraints in this idea.

Dec 21 - Conformal Technicolor arxiv.org/abs/hep-ph/0... Luty & Okui rephrase the hierarchy problem as a statement about the relationship between the dimensions of operators. The idea is that the Higgs has a dimension near 1 but all the operators in its OPE have dimensions > 4.

Dec 20 - Spontaneously broken spacetime symmetries arxiv.org/abs/hep-th/0... Low & Manohar explain why there are often fewer Goldstone modes than broken generators for spacetime symmetries. A goldstone acts like a local symmetry, which is not unique to a single global generator.

Dec 19 - Renormalizing Bias Parameters arxiv.org/abs/astro-ph... arxiv.org/pdf/0902.0991 McDonald (+ Roy) show how describing the statistics of tracers of dark matter (such as galaxies) requires renormalization of the bias parameters. They anticipate/discover the EFT structure found later.

Dec 18 - Indirect Evidence for Quantum Gravity journals.aps.org/prl/abstract... Page and Geilker design and perform an experiment to test if gravity is only (semi-) classical. They test and exclude the hypothesis that gravity is classical but couples to the quantum averaged stress tensor of matter

Dec 17 - Positivity Bounds journals.aps.org/prd/abstract... In 1985, Pham and Truong use dispersion relations to show that the 4 derivative term in pi-pi scattering must be positive. This was rediscovered (and generalized) 20 years later by Adams et al (arxiv.org/abs/hep-th/0...).

Dec 16 - CMB Trispectrum constraints arxiv.org/abs/2205.14408 arxiv.org/abs/1502.00635 These papers place the best constraints on primordial 4-point functions using Planck CMB data. Planck explored 3-point functions is great detail but analyses at higher points have been limited.

Dec 15 - Scattering amplitudes and Navier-Stokes arxiv.org/abs/2010.15970 www.sciencedirect.com/science/arti... Cheung & Mangan (building on an old paper by Wyld) study fluid dynamics through the lens of scattering amplitudes. They find new structures in fluids, particularly the double-copy

Dec 14 - cosmological perturbation theory in 1+1 D arxiv.org/abs/1502.07389 McQuinn and White study the evolution of structure in 1+1 dimensions, where the all-loop results can be calculated. They show SPT has a finite radius of convergence but doesn't converge to simulations.

Dec 13 - RG flow between minimal models inspirehep.net/literature/2... Zamolodchikov uses conformal perturbation theory to calculate the flow from the p to p-1 minimal model. He shows how to reproduce the predictions for the IR dimensions at p-1 from the data of the UV fixed point.

Dec 12 - A de Sitter S-matrix arxiv.org/abs/1209.6039 Marolf et al. define an S-matrix for massive particles in (fixed) global dS. They prove that many facts about flat space S-matrix also apply to dS. They develop a lot of interesting ideas that should have a wide range of applications

Dec 11 - The Phase Transition to Eternal Inflation arxiv.org/abs/0802.1067 Creminelli et al define the transition to slow-roll eternal inflation by the diverging volume of the reheating surface. They offer a precise prediction for the amplitude of the power spectrum where this occurs.

Dec 10 - Detectors and Rindler Particles journals.aps.org/prd/abstract... Unruh and Wald give a fantastically clear explanation of why accelerating observers see a thermal spectrum of particles: the particles are created from the energy you put into the detector to accelerate it.

Dec 9 - Axion-electron coupling limit from 47 Tucanae arxiv.org/abs/1507.05665 Studying white dwarf cooling in this globular cluster, Hansen et al. bound the axion coupling g_ae < 8.4E-14. This excludes the hint of axion cooling seen in previous studies (eg arxiv.org/abs/0806.2807).

Dec 8 - EFT / model building and the anomalous perihelion of mercury arxiv.org/abs/1106.1568 Wells explores how a model building / EFT approach to explaining Mercury's orbit would have worked. He introduces 3 ideas that all can work, and are realized in GR in different gauges.

Dec 7 - The Age of the Universe arxiv.org/abs/astro-ph... Combining data from CBI, DASI, BOOMERANG ++, Seivers et al. measure the age to be 13.7 +/- 0.2 billion years in near perfect agreement the modern value. This is when cosmology becomes a precision subject, giving tight errors on LCDM.

Dec 6 - Coherent Phase Argument for Inflation arxiv.org/abs/hep-ph/0... The horizon problem in the era of precision CMB is better understood in terms of the fact that all sound waves have the same phase. Dodelson provides a simple and powerful explanation of this modern argument.

Dec 5 - Microcausality in Curved Space-Time arxiv.org/abs/0709.1483 Causality is a central principle in physics, but how it manifests itself in quantum mechanical observables can be opaque. This paper provides a careful treatment of (some of) what it does and does not imply.

Dec 4 - An EFT for Holographic RG (Kaplan & Wang) arxiv.org/pdf/1406.4152 This paper writes the non-relativistic EFT in AdS that is dual to a large class of relativistic RG flows on the boundary. The construction of the bulk theory is the AdS analogue of the EFT of Inflation.

Dec 3 - Dark Energy Survey CMB-free H0 measurement arxiv.org/abs/1711.00403 Combining BBN+BAO+weak lensing they measure H0 = 67.4 +/- 1.1 km/s/Mpc, in agreement with the CMB without using CMB data. This was the first measurement of its kind at essentially current day precision.

Dec 2 - Scattering to many particles is (semi)-classical Eg inspirehep.net/literature/2... arxiv.org/abs/hep-ph/9... Two to N scattering is described by a semi-classical solution to the equations of motion (controlled by large N). This property of rare processes is far more general

Dec 1 - Peebles on dark matter and the CMB ui.adsabs.harvard.edu/abs/1982ApJ.... Peebles explains how the lack of observations of CMB temperature fluctuations at dT/T > 10^(-3) requires dark matter. It was a decade before anyone measured a non-zero value but this connection is profound

This December, I will be trying another experiment: Each day I will post 1 under-appreciated paper/result (my definition/no rules). I will also be posting my choices on Twitter (@nu_phases). I am curious to see which site has more interesting feedback/discussion

As a cosmologist - my New Year’s resolution is to find more ways to use the prefix “re” when it is in fact the first time something happened. Eg - fried chicken (2023) -> refried chicken (2024)

I want this wall for my office

Some exceptional young cosmologists won the breakthrough new horizons prize for their work on LSS! Their work has really transformed the field to the point that seeing a new BOSS analysis is as common as new CMB analyses have been. Congrats!