Redshift-space distortions (RSD), caused by the peculiar velocities of galaxies, are a key modeling challenge in galaxy clustering analyses, limiting the scales from which cosmological information can be reliably extracted. Unlike dynamical or galaxy bias effects, RSD imprint features are sensitive to nonlinearities across all scales. This paper explores an alternative to the state-of-the-art analytical approach—the effective field theory (EFT)—by partially preserving this nonperturbative nature of RSD. We compare its effectiveness against the EFT in analyzing power spectrum and bispectrum multipoles from synthetic samples of luminous red galaxies at redshifts 0.3 and 0.57, using the projected sensitivity of a Stage-IV galaxy survey. Our results demonstrate that this distinct treatment of RSD improves the robustness of model predictions for both statistics, extending the validity range of the EFT from approximately $0.2h{\mathrm{Mpc}}^{-1}$ to $0.35h{\mathrm{Mpc}}^{-1}$ for the one-loop power spectrum and from $0.1h{\mathrm{Mpc}}^{-1}$ to $0.14h{\mathrm{Mpc}}^{-1}$ for the tree-level bispectrum. This leads to a significant enhancement in the precision of cosmological parameter constraints, with uncertainties on the Hubble rate, matter density, and scalar amplitude of fluctuations reduced by 20%–40% for the power spectrum multipoles alone compared to the EFT, and by 25%–50% for joint analyses with the bispectrum. The RSD treatment proposed here may thus play a crucial role in maximizing the scientific return of current and future galaxy surveys. To support this advancement, all models for the power spectrum and bispectrum used in this work are made available through an extended version of the python package comet.

We introduce light isotope nucleosynthesis with jax (linx), a new differentiable public big bang nucleosynthesis code designed for fast parameter estimation. By leveraging jax, linx achieves both speed and differentiability, enabling the use of Bayesian inference, including gradient-based methods. We discuss the formalism used in linx for rapid primordial elemental abundance predictions and give examples of how linx can be used. When combined with differentiable cosmic microwave background power spectrum emulators, linx can be used for joint cosmic microwave background and big bang nucleosynthesis analyses without requiring extensive computational resources, including on personal hardware.

We present a joint-likelihood analysis of big bang nucleosynthesis (BBN) and cosmic microwave background (CMB) data, consistently combining likelihoods and taking into account uncertainties in nuclear reaction rates for the first time. Bayesian inference is performed on the baryon abundance and the effective number of neutrino species, $N_{\mathrm{eff}}$, using a CMB Boltzmann solver in combination with linx, a new flexible and efficient BBN code. We marginalize over Planck nuisance parameters and nuclear rates to find $N_{\mathrm{eff}}=3.08_{-0.14}^{+0.15},2.94_{-0.15}^{+0.16}$, or ${2.96}_{-0.14}^{+0.13}$, for three separate reaction networks. This framework enables robust testing of the lambda cold dark matter paradigm and its variants with CMB and BBN data.

The title theory is formulated. It entails a quantum-coherent variant of the Fermi-Dirac distribution and casts new light on neutrino oscillations. It might enable the incorporation of neutrino mixing into the modeling of core-collapse supernovae and neutron star mergers.

Quasiperiodic eruptions (QPEs) are a class of x-ray flaring phenomena that occur at the centers of galactic nuclei and are likely to arise from repeated interactions between a star and an accretion disk. This work investigates whether such disk-crossing events can accelerate protons and generate detectable high-energy neutrinos. Based on observed QPE luminosities, recurrence periods, and flare durations, the stellar motion parameters and the disk properties are evaluated. We consider proton acceleration during the breakout phase and evaluate neutrino production, accounting for both $pp$ and $p\gamma$ interactions. Applying the method to ten observed QPE sources, we estimate the neutrino fluence accumulated over a 10-year observation period and compute the corresponding detection numbers for IceCube and IceCube-Gen2. Our analysis indicates that protons can be accelerated up to several tens of TeV, and neutrino production is mostly confined below $\sim 10\mathrm{TeV}$. The resulting optimized neutrino fluence spans from $7.0\times {10}^{-7}$ to $1.5\times {10}^{-4}\mathrm{GeV}{\mathrm{cm}}^{-2}$ for these ten QPE sources. We find that the expected neutrino detection number for a single QPE source is low, and the expected neutrino detection number would approach unity only for the most promising QPE source occurring at a distance closer than a few Mpc. Next-generation neutrino telescopes with better detection sensitivities at $\lesssim \mathrm{TeV}$ can significantly improve the capture capacity of the cumulative neutrino signal from the QPE population.

Tilt-to-length (TTL) noise presents a dominant limitation for space-based gravitational wave (GW) detection. The coupling between pointing jitter and wavefront errors induces phase noise in far-field detection, which emerges as a principal component of the TTL noise budget. We derive an analytical model for this TTL noise using the Zernike polynomial decomposition. Our framework expresses the TTL coefficients via matrix multiplication, providing analytical insight into the interaction mechanism between pointing jitter and wavefront errors. We numerically validate the theoretical expression and perform ${10}^4$ Monte Carlo simulations to quantify the TTL noise at both the maximum intensity point (Imax) and the phase stationary point. Moreover, we demonstrated that optimizing the beam-waist radius to 30 mm efficiently suppresses the TTL noise to $1\mathrm{pm}{\mathrm{Hz}}^{-1/2}$, without compromising the power budget of the geocentric GW detections.

We explore the constraints on new physics from the recent NA62 observation of the kaon decay $K^{+}\to {\pi }^{+}+\cancel{E}$ with missing energy $\cancel{E}$ in the context of a dark-matter (DM) scenario recently used to accommodate the Belle II finding of an enhanced rate of the $b$-meson decay $B^{+}\to K^{+}+\cancel{E}$ compared to the standard-model expectation. Specifically, assuming that a light real scalar boson $\varphi$ plays the role of DM and working in an effective field-theory framework, we study model independently the impact of operators involving $\varphi$ and ordinary quarks on the aforementioned transitions over the kaon mode’s kinematical mass region of $m_{\varphi }<(m_K-m_{\pi })/2=177\mathrm{MeV}$. Such a DM particle is subject to significant restrictions from the observed relic abundance and from DM direct-detection experiments incorporating the Migdal effect, as well as from indirect searches in cosmic microwave background data and collider experiments, except when its mass is between 110 and 146 MeV. We demonstrate that $K^{+}\to {\pi }^{+}\varphi \varphi$ can saturate the new-physics window in the NA62 result if $m_{\varphi }$ lies in the 110–130 MeV portion of the range left by the DM constraints, thus providing a complementary constraint on this scenario. Improved data from future Belle II and NA62 measurements and DM quests can test it more stringently. In particular, expanding the NA62 signal window into the region that is now removed due to three-body decay background modes could further explore the remaining mass window for this type of invisible particle, $130<m_{\varphi }<177\mathrm{MeV}$.

An explicit formula for the interaction energy of $n$ vortices in the Abelian Higgs (or Ginzburg-Landau) model is derived, valid in the regime where all vortices are close to one another. An immediate consequence of this formula is that the interaction energy of a vortex pair with separation $d$ varies as $d^4$, not $d^2$. The formula contains $n-1$ real coefficients, which are fixed by certain spectral data of the Jacobi operator of the cocentered $n$-vortex. The coefficients are computed numerically for $n=2$ and $n=3$ for couplings $0.1\le \lambda \le 2.5$. The resulting short-range interaction potentials are compared with the results of full field theory simulations for $\lambda =0.5$ and $\lambda =2$, with excellent agreement at small to moderate vortex separation.

The gauge-singlet right-handed neutrinos would be essential to explain the tiny masses of active neutrinos. We consider the effective field theory of the Standard Model extended with these fields under the assumption that neutrinos are Dirac particles. In this framework, we provide a comprehensive study for the phenomenological consequences of various dimension six interactions employing various high and low energy observables. These include the neutrino mass itself, constraints from electroweak precision test and collider searches for lepton or jet plus missing energy, coherent neutrino-nucleus scattering, beta decays, as well as decays of proton, meson, tau, and top. We also study their astrophysical and cosmological implications for stellar cooling and relativistic degrees of freedom.

Recent work [M. L. Wagman, Lanczos, the transfer matrix, and the signal-to-noise problem, Phys. Rev. Lett. 134, 241901 (2025).] found that an analysis formalism based on the Lanczos algorithm allows energy levels to be extracted from Euclidean correlation functions with faster ground-state convergence than effective masses, convergent estimators for multiple states from a single correlator, and two-sided error bounds. After filtering out spurious eigenvalues and using outlier-robust estimators within a nested bootstrap framework, Lanczos estimators behave more like multistate fit results than effective masses—but without involving statistical fitting. We extend this formalism to the determination of matrix elements from three-point correlation functions and provide a physical picture of “spurious-state filtering” involving restriction to a Hermitian subspace. We demonstrate similar advantages for matrix elements as for spectroscopy through example applications to noiseless mock-data and (bare) forward matrix elements of the strange scalar current between both ground and excited states with the quantum numbers of the nucleon.

Two-quark–two-antiquark systems with four different quark flavors are considered in the framework of two-dimensional QCD, in the light-cone gauge, at leading orders of the $1/N_c$ expansion. Introducing basis functions with color-singlet mesonic clusters, integral equations are established for the Green’s functions and the related scattering amplitudes involved in the sectors of the direct and quark-exchange channels. The problem of infrared divergences is dealt with via a systematic use of an infrared regulator cutoff introduced in the gluon propagator. It is shown that the on-mass shell scattering amplitudes are free of infrared divergences up to order $1/N_c^2$. In the limit of vanishing of the infrared cutoff, they can be represented by effective four-meson contact-type interaction terms with unitarity loops, calculable in terms of the meson wave functions and propagators. The results, obtained at order $1/N_c^2$, are summed with the constraint of unitarization. The unitarized scattering amplitudes are continued in the total mass-squared variable below the two-meson thresholds, leading to a tetraquark bound state equation, which generally has one solution. Spectroscopic applications of the above results are sketched and discussed.

The spectrum of half-Bogomol’nyi–Prasad–Sommerfeld (BPS) single-particle operators of the D1-D5 system in the supergravity regime is dual to the spectrum of Kaluza-Klein modes of tensor and graviton multiplets in ${\mathrm{AdS}}_3\times {\mathrm{S}}^3$. We present simple formulas for all four-point tree-level correlators of scalar half-BPS primary operators in the spectrum, and in particular, we bootstrap the four-point correlator of the graviton multiplet for all KK levels. A key insight of our approach is the use of generalized Mellin space, and a decomposition of the correlators into distinct subsectors each one characterized by different on shell constraints among the Mellin variables. The resulting Mellin amplitudes involve a small set of building blocks with manifest properties under a six-dimensional symmetry.

Double field theory (DFT) can be constructed up to third order as the double copy of Yang-Mills theory. In this construction, one starts with Yang-Mills theory on Minkowski space and the resulting DFT action is also defined on Minkowski space. In this work, I extend this double copy procedure to obtain a DFT action on a constant DFT background starting from two Yang-Mills actions constructed around nontrivial background gauge fields on Minkowski space.

We discuss the emission of radiation from general sources in quantum scalar, electromagnetic, and gravitational fields using the Rindler coordinate frame, which is suitable for uniformly accelerated observers, in the Minkowski vacuum. In particular, we point out that to recover, from the point of view of uniformly accelerated observers in the interaction picture, the usual Larmor radiation, which is independent of the choice of the vacuum state, it is necessary to incorporate the Unruh effect assuming the Minkowski vacuum. Thus, the observation of classical Larmor radiation in the Minkowski vacuum could be seen as vindicating the Unruh effect in the sense that it is not correctly recovered in the uniformly accelerated frame unless the Unruh effect is taken into account.

We present multifermions in the spherically symmetric Einstein-Dirac system. Dirac fermions are self-localized within a spherically symmetric Einstein gravity, i.e., the Schwarzschild-like space-time metric. Most of previous studies of the Einstein-Dirac system are restricted to two neutral fermions or to many fermions with the same high-angular momentum filling a single shell. Our model considers full-filling of fermions in multiple shells, similarly to the conventional nuclear shell model. We solve the model for fermion numbers $N_{\mathrm{f}}=2$, 6, 12 and 20, which can realize a spherically symmetric system. Even single-shell multifermions exhibit a multipeak structure and fragmentation in the high redshift region. The behavior observed in our multishell model can be explained by interactions between the shells and resulting delocalization. We also investigate the pressure of the solutions which defines the existence (or absence) of intershell interactions. The radial pressure is attractive, supporting compactness of the solutions. Finally, we show the correlations between the nontrivial changes in the Shannon entropy (a logarithmic measure of information content) and the structural deformations of the solutions.

Self-dual black holes in (2, 2) signature spacetime—Klein space—have recently attracted interest in the context of celestial holography. Motivated by this development, we investigate the structure of spacetime near the horizons of these solutions. Focusing on the self-dual Schwarzschild-Taub-Newman-Unti-Tamburino solution, we demonstrate that, near the Kleinian horizons, the geometry exhibits a local infinite-dimensional symmetry generated by supertranslations and super-rotations. Establishing this result requires refining and extending earlier analyses of asymptotic symmetries near null surfaces. We formulate the appropriate boundary conditions, derive the infinite-dimensional algebra underlying the local symmetries, and compute the associated Noether charges, finding them to be integrable. Finally, we discuss the connection of our findings to recent observations in the literature regarding self-dual black holes in Klein space, including the diffeomorphism relating static and stationary solutions.

A novel procedure is presented that allows the construction of all axial vector fields on Riemannian two-spheres. Using these axial vector fields and the center-of-mass unit sphere reference systems, a constructive definition of quasilocal spin-angular momentum is introduced. Balance relations are also derived, with respect to arbitrary Lie-propagated unit sphere reference systems, to characterize the angular momentum transports in spacetimes without symmetries.

Instead of the much more involved covariant counterterm method, we apply the well-justified background subtraction method to calculate the first-order corrections to Kerr-AdS black hole thermodynamics induced by the higher derivative terms up to the cubic of Riemann tensor, where the computation is further simplified by the decomposition trick for the bulk action. The validity of our results is further substantiated by examining the corrections induced by the Gauss-Bonnet term. Moreover, by comparing our results with those obtained via the Arnowitt-Deser-Misner and Wald formulas in Lorentzian signature, we can extract some generic information about the first-order corrected black hole solution induced by each higher derivative term.

It is known that the amplification factor, defined as the ratio of the lensed to the unlensed waveform in the frequency domain, satisfies the Kramers-Kronig (KK) relation, which connects the real and imaginary parts of the amplification factor for any lensing signal. In this work, we reformulate the KK relation in terms of the magnitude and phase of the amplification factor. Unlike the original formulation, the phase cannot be uniquely determined from the magnitude alone due to the possible presence of a Blaschke product. While this ambiguity does not arise in the case of a point-mass lens, it can appear in more complex lens models, such as those with an NFW (Navarro–Frenk–White) lens profile. As an application of our formulation, we demonstrate that the leading-order behavior of the phase in the low-frequency regime is completely determined by the leading-order behavior of the magnitude in the same regime. This reproduces known results from the literature, derived via low-frequency expansions for specific lens models. Importantly, our result does not rely on any particular lens model, highlighting a universal feature that the low-frequency behavior of the amplification factor is tightly constrained by the KK relation. As a further application, we present two examples in which the phase is constructed from a given analytic form of the magnitude using the newly derived KK relation. In particular, the second example allows for an analytic evaluation of the KK integral, yielding an explicit expression for the phase. This study offers a potentially powerful method for applying the KK relation in model-agnostic searches for lensing signals.

We forecast the sensitivity of future correlations between cosmic microwave background (CMB) lensing and the Lyman-$\alpha$ forest power spectrum. This squeezed-limit bispectrum probes the connection between the Lyman-$\alpha$ transmission and the underlying large-scale matter density field. We recover the measured signal-to-noise (SNR) ratio obtained with $\mathrm{Planck}\times \mathrm{BOSS}$, and forecast a SNR of 10.3,14.8 and 20.2 for DESI combined with ACT, SO, and CMB-S4, respectively. For DESI and SO/CMB-S4, the correlation should be detectable at $\mathrm{SNR}\ge 5$ in 5 redshift bins, useful for distinguishing our signal from several contaminants. Indeed, our forecast is affected by large theoretical uncertainties in the current modeling of the signal and its contaminants, such as continuum misestimation bias or damped-Lyman-$\alpha$ absorbers. Quantifying these more accurately will be crucial to enable a reliable cosmological interpretation of this observable in future measurements. We attempt to enumerate the features required in future Lyman-$\alpha$ forest simulations required to do so.