We present a single, dimension-independent framework that links four-dimensional duality-invariant nonlinear electrodynamics to two-dimensional integrable sigma models. Both sectors are shown to obey the same firs-order Courant–Hilbert equation, solved by a common generating function and an auxiliary-potential formulation. Within this structure, a discrete $\phi$ parity acts as a selection rule, organizing deformation series into integer versus fractional powers. Two commuting deformations—an irrelevant parameter $\lambda$ and a marginal parameter $\gamma$—admit universal flow representations that recover root-$T\overline{T}$ dynamics and extend them in a controlled way. The construction yields closed-form families (generalized Born-Infeld, logarithmic, and $q$ deformed) and a new integrable model, all realized in 2D and 4D. These results replace case-by-case analyses with a unified route to solvable nonlinear theories, with immediate relevance to gauge dynamics, string-inspired effective actions, and integrable models.

Nontopological solitons formed during first-order phase transitions can serve as macroscopic dark matter candidates, with their stability ensured by a charge asymmetry traditionally assumed to originate from baryogenesis. Following this generic pattern, we demonstrate that solitogenesis after baryogenesis makes the solitons a coincident dark matter candidate, providing new explanations for the coincidence problem between baryon and dark matter energy densities. We derive a novel and robust conclusion; asteroid-mass coincident soliton dark matter is always accompanied by detectable gravitational waves observable by LISA, $\mu \mathrm{Ares}$, and Theia, providing a new candidate beyond primordial black holes in this mass window. Additionally, we propose a simple neutrino-ball scenario that addresses baryon asymmetry, dark matter, and neutrino masses, featuring new particles below the electroweak scale and correlated observable signals, including lensing, gravitational waves, and soliton evaporation or collisions.

The recent observation of multiple near-threshold structures in $e^{+}{e}^{-}$ annihilation—including $\psi (3770)$, $G(3900)$, $R(3760)$, $R(3780)$, and $R(3810)$—reveals limitations in existing models of charmonium and exotic hadrons. In this paper, we propose a unified coupled-channel description that simultaneously incorporates all five near-threshold structures using parameters constrained by hadron spectroscopy. Our model accurately reproduces the line shapes in both $D\overline{D}$ and nonopen-charm hadron (nOCH) channels, resolves the asymmetric profile of $\psi (3770)$, and produces the $G(3900)$ bump. We identify the $R(3780)$ as the dominant manifestation of $\psi (3770)$, attribute $R(3760)$ to $D\overline{D}\to \text{nOCH}$ rescattering and suggest that $R(3810)$ arises from coupling between the $\psi (1D)$ state and the $h_c\pi \pi$ channel. The significant non-$D\overline{D}$ decay of $\psi (3770)$ is explained by its near-threshold position. This analysis provides a coherent, unquenched framework centered on a charmonium $\psi (1D)$ core for near-threshold phenomena and offers a predictive approach extendable to bottomonium systems and future data from Belle II.

We compute the partition function for the $N=1$ spinning particle, including pictures and the large Hilbert space, and show that it counts the dimension of the Becchi-Rouet-Stora-Tyutin cohomology in two- and four-dimensional target space. We also construct a quadratic action in the target space. Furthermore, we find a consistent interaction as a derived bracket based on the associative product of worldline fields, leading to an interacting theory of multiforms in space-time. Finally, we comment on the equivalence of the multiform theory with a Dirac fermion. We also identify the chiral anomaly of the latter with a Hodge anomaly for the multiform theory, which manifests itself as a deformation of the gauge fixing.

We compute tree-level gluon amplitudes as worldline correlators of vertex operators in a bosonic spinning particle model. In this framework, the particle’s position degrees of freedom are extended by complex bosonic variables that encode its spin. In the free theory, the model exhibits a first-class constraint algebra whose gauging ensures the unitarity of the quantum theory. This algebra is a contraction of the $sl(2,\mathbb{R})$ algebra, which is by itself a subalgebra of the Virasoro algebra. In string theory, gauging the Virasoro algebra plays a similar role. Our model admits a consistent truncation to describe a pure spin-1 particle. Non-Abelian interactions are introduced by using Becchi-Rouet-Stora-Tyutin (BRST) techniques, which allow us to extract the vertex operators of the theory as suitable deformations of the BRST charge. BRST invariance is central to ensuring the consistency of the tree-level amplitudes analyzed in this work. We discuss connections with similar worldline constructions and comment on the potential relevance of this framework for uncovering the structures underlying the double-copy program in gauge and gravitational theories.

The dynamics of highly magnetized plasmas in extreme astrophysical environments are effectively modeled by force-free electrodynamics (FFE), a framework essential for studying objects like neutron stars and accreting black holes. The inherently nonlinear nature of the FFE equations makes finding exact solutions a challenging task. This paper explores an innovative approach to solving these equations by foliating spacetime into two-dimensional surfaces, specifically tailored to the geometry of electromagnetic fields. The foliation approach exploits the fact that the kernel of the force-free field defines an involutive distribution, naturally lending itself to a geometric decomposition. This method has previously been applied with great success in Kerr and FLRW spacetimes. By extending this formalism, we develop new exact solutions to the FFE equations in several distinct spacetimes, including cases where the metric remains partially undetermined. Additionally, we present a novel class of solutions that smoothly transition between magnetically dominated and electrically dominated regimes over time. Finally, we construct a pair of vacuum degenerate fields in arbitrary axisymmetric spacetimes, further demonstrating the utility of the foliation approach. These results offer a new perspective on the dynamical evolution of electromagnetic fields and their geometric underpinnings in various spacetime geometries, broadening the applicability of the framework for understanding the dynamics of highly magnetized plasmas in general relativistic astrophysical contexts.

We construct Kaluza-Klein monopole solutions with scalar hair provided by a massive complex scalar field multiplet that minimally couples to five-dimensional Einstein gravity. Writing the scalar field multiplet in terms of the Wigner D-matrices, we introduce the ansatz of the scalar multiplet compatible with the symmetries of the Gross-Perry-Sorkin monopole, on which the scalar hair grows. We give the ansatz for a multiplet with arbitrary number of components, whereas we show numerical solutions of the hairy Kaluza-Klein monopole specifically for the cases of scalar triplet and quadruplet. These generalize the preceding study on a doublet [J. High Energy Phys. 01 (2024) 181]. We find that the range of the mass and angular momentum of the hairy solutions are larger for higher multiplets.

Dark matter (DM) search is one of the greatest challenges in physics. If DM consists of particles, it may form a spike around supermassive black holes prevalent in galaxy centers. This spike could be potentially observed by altering the orbits of extreme mass ratio inspirals (EMRIs), one of LISA’s main targets. Meanwhile, the effects of EMRI on the DM spike have also been explored. In this study, we focus on the tidal resonances between DM particles and EMRI secondary. As the EMRI orbit evolves via gravitational wave backreaction, each DM particle experiences a significant number of resonances. Although the effect of each individual resonance is small, their cumulative impact might significantly alter the DM particle’s orbit. To test this possibility, we derived an explicit form of the interaction Hamiltonian and carried out numerical simulations on generic Kerr orbits with nonzero eccentricity and inclination—cases not previously explored extensively. Extending our analysis to unprecedentedly high resonance orders, we quantified the exponential decay of higher-order resonance amplitudes. These results demonstrate that tidal resonances exert an extremely limited influence on the DM spike.

We introduce a new coherent state expansion of the exponential representation of the S-matrix for the classical gravitational two-body problem. By combining the Kosower-Maybee-O’Connell (KMOC) formalism with the Dirac bracket structure emerging in the classical limit, we derive compact and gauge-invariant expressions for scattering observables in the presence of radiation. This causal formulation bypasses the calculation of KMOC cuts and provides a direct link between observables and a minimal set of classical matrix elements extracted from amplitudes. We illustrate our method with several examples, including the impulse, spin kick, angular momentum, waveform and the related radiative fluxes. Finally, using our formalism we evaluate for the first time the spin kick and the change in angular momentum of each particle up to $\mathcal{O}(G^2{s}_1^{j_1}{s}_2^{j_2})$ with $j_1+j_2\le 11$.

We investigate the dynamics of the Friedmann-Lemaître-Robertson-Walker spacetime within the framework of $f(R)$ gravity using a compact, model-independent dynamical systems approach. By assuming a power-law scale factor, we explore ekpyrotic and accelerating solutions to address the big bang singularity. Our analysis demonstrates that a cosmological bounce, characterized by a transition from contraction to expansion, possibly avoids the singularity without directly using the Raychaudhuri equation, unlike previous approaches using specific $f(R)\simeq R^n$ forms. We identify a key fixed point in the phase space corresponding to the bounce, supported by perturbation analysis and qualitative description of trajectories in the phase space. The results suggest that $f(R)$ gravity provides a robust framework for nonsingular cosmologies.

Employing the Newman-Penrose formalism and following the classic Teukolsky-like approach, we linearize the field equations of quadratic gravity on the Kerr background and combine them with the linearized Ricci and Bianchi identities. This leads to constraints on linear perturbations of the Kerr spacetime in quadratic gravity. The resulting differential equations are decoupled in such a way that only the Ricci tensor perturbations need to be found on the Kerr background in order to fully determine the solution. The results are illustrated in the simple nontrivial cases of the Schwarzschild and Minkowski geometries.

Gravitational lensing of gravitational waves provides a powerful probe of the mass density distribution in the Universe. Wave optics effects, such as diffraction, make the lensing effect sensitive to the structure around the Fresnel scale, which depends on the gravitational wave frequency and is typically sub-Galactic for realistic observations. Contrary to this common lore, we show that wave optics can, in principle, probe matter perturbations even below the Fresnel scale. This is achieved by introducing a new quantity derived from the amplification factor, which characterizes the lensing effect, and analyzing its correlation function. Our results demonstrate that this quantity defines an effective Fresnel scale—a characteristic scale that can be arbitrarily small, even when observational frequencies are bounded. In practice, the effective Fresnel scale is constrained by the observation time $T$ and is suppressed by a factor of $1/\sqrt{fT}$ relative to the standard Fresnel scale at frequency $f$. Nevertheless, it remains significantly smaller than the conventional Fresnel scale for $fT\gg 1$; for instance, in one-year observations of mHz GWs, the effective Fresnel scale can be as small as 1 pc. This approach opens new avenues for probing the fine-scale structure of the Universe and the nature of dark matter.

Cosmological models are often motivated and formulated in the language of particle physics, using quantities such as the axion decay constant, but tested against data using ostensibly physical quantities, such as energy density ratios, assuming uniform priors on the latter. This approach neglects priors on the model from fundamental theory, including from particle physics and string theory, such as the preference for sub-Planckian axion decay constants. We introduce a novel approach to learning theory informed priors for Bayesian inference using normalizing flow (NF), a flexible generative machine learning technique that generates priors on model parameters when analytic expressions are unavailable or difficult to compute. As a test case, we focus on early dark energy (EDE), a model designed to address the Hubble tension. Rather than using uniform priors on the phenomenological EDE parameters $f_{\mathrm{EDE}}$ and $z_c$, we train a NF on EDE cosmologies informed by theory expectations for axion masses and decay constants. Our method recovers known constraints in this representation while being $\sim 300$, 000 times more efficient in terms of total CPU compute time. Applying our NF to Planck and BOSS data, we obtain the first theory informed constraints on EDE, finding $f_{\mathrm{EDE}}\lesssim 0.02$ at 95% confidence with an $H_0$ consistent with Planck, but in $\sim 6\sigma$ tension with SH0ES. This yields the strongest constraints on EDE to date, additionally challenging its role in resolving the Hubble tension.

We present a Gaussianity test of the cosmic microwave background polarization by analyzing the statistics of unpolarized points in the sky, classified into three distinct types: saddles, comets, and beaks. This classification of singular points where both Stokes parameters $Q$ and $U$ vanish stems from the fact that linear polarization is described by a second-rank tensor. By varying the number of spherical harmonics included in the polarization maps, one can probe the statistics of these singularities across a range of angular scales. Applying this method to Planck data we find clear evidence of non-Gaussianity in both E and B modes of polarization. This approach may be especially useful for processing data from current and future experiments such as the Simons Observatory. In particular, it can help to assess the Gaussianity of a potentially detected B mode signal, thereby determining whether it arises from primordial tensor perturbations—as predicted by inflation—or from alternative sources such as polarized foregrounds (e.g., thermal dust), E-to-B mode leakage, systematics, photon noise, or gravitational lensing. We have made publicly available software that finds unpolarized points of all three types on any polarization map in Hierarchical Equal Area isoLatitude Pixelation format with full or incomplete sky coverage to enable testing of the observed signal for Gaussianity.

The Laser Interferometer Space Antenna (LISA) is expected to detect thousands of individually resolved gravitational wave sources, overlapping in time and frequency, on top of unresolved astrophysical and/or primordial backgrounds. Disentangling resolved sources from backgrounds and extracting their parameters in a computationally intensive “global fit” is normally regarded as a necessary step toward reconstructing the properties of the underlying astrophysical populations. Here, we show that it is in principle feasible to infer the population properties of the most numerous of LISA sources—Galactic double white dwarfs—directly from the frequency (or, equivalently, time) strain series by adopting a simulation-based approach, without extracting and estimating the parameters of each single source. By training a normalizing flow on a custom-designed compression of simulated LISA frequency series from the Galactic double white dwarf population, we demonstrate how to infer the posterior distribution of population parameters (e.g., mass function, frequency, and spatial distributions). This allows for extracting information on the population parameters from both resolved and unresolved sources simultaneously and in a computationally efficient manner. This approach can be extended to other source classes (e.g., massive and stellar-mass black holes, extreme mass ratio inspirals) and to scenarios involving non-Gaussian or nonstationary noise (e.g., data gaps), provided that fast and accurate simulations are available.

We analyze 15 years of Fermi-LAT data and produce a detailed model of the Sun’s inverse-Compton scattering emission (solar halo), which is powered by interactions between ambient cosmic-ray electrons and positrons with sunlight. By developing a novel analysis method to analyze moving sources, we robustly detect the solar halo at energies between 31.6 MeV and 100 GeV, and angular extensions up to 45° from the Sun, providing new insight into spatial regions where there are no direct measurements of the Galactic cosmic-ray flux. The large statistical significance of our signal allows us to subdivide the data and provide the first $\gamma$-ray probes into the time variation and azimuthal asymmetry of the solar modulation potential, finding time-dependent changes in solar modulation both parallel and perpendicular to the ecliptic plane. Our results are consistent with (but with independent uncertainties from) local cosmic-ray measurements, unlocking new probes into astrophysical processes near the solar surface.

We explore the connection of baryogenesis at temperatures below the electroweak scale and signals for long-lived particles at the LHC. The model features new SM singlets, with a long-lived fermion decaying to quarks to generate the baryon asymmetry. The model avoids strong flavor physics bounds while predicting a rich diquark phenomenology, monojet signals, and displaced vertices. We show how the displaced vertex signals can be probed at the high luminosity LHC. The large transverse production makes a strong physics case for constructing far detector experiments such as MATHUSLA, ANUBIS, and CODEX-b, complementary to the central and forward long-lived particle program.

We propose a novel cogenesis scenario by utilizing the two-body decay of heavy right-handed neutrinos (RHNs) via an effective operator involving an axionlike particle (ALP), dark matter (DM), and a light chiral fermion ${\nu }_R$. This allows the two-body decay of heavy RHNs into ${\nu }_R$ and ALP, thereby generating a lepton asymmetry in ${\nu }_R$ which later gets transferred to left-handed leptons via sizeable Yukawa coupling with a neutrinophilic Higgs doublet. The asymmetry in left-handed leptons is then converted into baryon asymmetry via electroweak sphalerons. The lepton number violation by heavy RHNs also induces a one-loop Majorana mass of ${\nu }_R$ rendering the light neutrinos to be Majorana fermions. Successful leptogenesis constrains the parameter space in terms of RHN mass and axion decay constant. This has interesting consequences for both ALP and QCD axion DM parameter space within reach of several ongoing and near future experiments. We also propose a Dirac version of this scenario without any total lepton number violation. This leads to a long-lived asymmetric Dirac fermion contributing partially to DM, thereby opening up more parameter space for ALP. In addition to axion search experiments, the proposed scenarios can have observable signatures at cosmic microwave background and DM search as well as terrestrial particle physics experiments.

The recent detection of the solar neutrino background at dark matter direct detection experiments paves the way to fully explore an important degeneracy in neutrino oscillations in the presence of new interactions, named the LMA-Dark degeneracy. This degeneracy makes it impossible to determine the neutrino mass ordering in oscillation experiments if neutrinos have new vectorial interactions with matter. As the composition of solar neutrinos at the Earth consists of all three neutrino flavors, testing the presence of new neutrino interactions in the muon and tau neutrino sector in scatterings can fully probe the LMA-Dark region for the first time. In this paper we show that current data from XENONnT and PandaX-4T do not yet exclude the LMA-Dark region with equal couplings of a new mediator to muon and tau neutrinos and quarks, and we identify the possible experimental scenarios to do so in the future. We also show that dark matter experiments can distinguish new interactions in the muon or tau sector only from new interactions affecting both sectors.

The Randall-Sundrum model with the Higgs localized on the IR brane solves the gauge hierarchy problem. However, the associated low cutoff ($\mathrm{\Lambda }\sim 10\mathrm{TeV}$) generically leads to unacceptably rapid nucleon decay and excessively large Majorana neutrino masses. Achieving consistency while simultaneously explaining the Yukawa hierarchy requires either a horizontal symmetry or a discrete gauged symmetry. We demonstrate that eliminating all dangerous operators within a horizontal symmetry framework must come with large and unattractive charge assignments, if possible at all. Hence, we consider an exact discrete gauged ${\mathbf{Z}}_N$ symmetry, with fermion mass hierarchies generated via wave function overlap. We employ this to reproduce the current Cabibbo-Kobayashi-Maskawa and Pontecorvo-Maki-Nakagawa-Sakata structures. Assuming universal five-dimensional Yukawa couplings, generation-blind profile for right-handed neutrinos, and flat profile for the third generation SM doublets, it predicts Dirac neutrinos with a total mass $\sim 66\mathrm{meV}$. Since the ${\mathbf{Z}}_N$ charges must be generation blind, flavor observables serve as key probes.