Modern astronomical surveys are producing progressively larger and more complex datasets, making traditional supervised approaches that rely on extensive labelled catalogues increasingly difficult. Consequently, pre-training using self-supervised learning (SSL), which offers a scalable route by extracting structure directly from unlabelled images, is becoming attractive for many downstream applications. In this work we consider the use of coupled self-supervised representation learning approaches for radio galaxy morphology pre-training. In order to account for the more nuanced variations in radio galaxy morphology than are typically included in the augmented views of view-based SSL algorithms, we use a pre-trained Variational Autoencoder (VAE) to generate views for training a larger view-based self-supervised model. To do this, a $β$-VAE was trained on the Radio Galaxy Zoo (RGZ) dataset, where moderate regularization ($β= 2.3$) was found to provide a good balance between reconstruction quality and disentanglement of generative factors such as source multiplicity and lobe asymmetry. An analysis of the $β$-VAE reveals that Fanaroff-Riley class identity manifests as a continuous transition across the latent space, rather than being associated to a single discrete dimension. $β$-VAE reconstructions were then incorporated as generative augmentations within a view-based SSL pipeline. Our experiments show that combining these generative views with standard image augmentations improves downstream classification performance, and we present ablation studies clarifying the relative contribution of each augmentation type. These results indicate that generative and contrastive approaches are complementary, and point toward disentanglement-aware self-supervised learning as a promising direction for future radio astronomy surveys.

We present a theory of an interference process that starts with N coherently pumped two-mode parametric down-conversion (PDC) sources, whose output modes are directed to N observers such that each observer receives modes from two different source crystals. Each observation station is equipped with a locally controlled PDC crystal, coherently pumped with the source crystals, whose output modes are perfectly aligned with the input modes from the source PDCs. By varying the local phases of the input modes, perfect 2N-photon interference can be observed in 2N single-photon registrations, one in each output mode of these N local PDCs. The interference results from the indistinguishability of the origins of the detected 2N photons: either they all originate from the source PDCs or from the local PDCs. Bell-GHZ nonclassicality of the process emerges when one also considers situations in which at least one of the local PDC processes is blocked. In such cases, the 2N-photon interference disappears. A "lifted" Clauser-Horne inequality is violated when its sole negative term, involving all observers with all local pumps active, is tuned to maximal destructive interference, while all other terms involve settings in which one of the local pumps is off.

We numerically construct a one-parameter family of critical spacetimes in arbitrary continuous dimensions D>3. This generalizes Choptuik's D=4 solution to spherically symmetric massless scalar-field collapse at the threshold of D-dimensional Schwarzschild-Tangherlini black hole formation. We refer to these solutions, which share the discrete self-similarity of their four-dimensional counterpart, as critical spacetime crystals. Our main results are the echoing period and Choptuik exponent of the crystals as continuous functions of D, with detailed data for the interval 3.05<D<5.5. Notably, the echoing period has a maximum near D=3.76. As a by-product, we recover the echoing periods and Choptuik exponents in D=4 (5): Delta=3.445453 (3.22176) and gamma=0.373961 (0.41322). We support these numerical results with analytical expansions in 1/D and D-3. They suggest that both the echoing period and Choptuik exponent vanish as D approaches 3 from above. This paves the way for a small-(D-3) expansion, paralleling the large-$D$ expansion of general relativity. We also extend our results to two-dimensional dilaton gravity.

Large Language Models (LLMs) acting as artificial agents offer the potential for scalable behavioral research, yet their validity depends on whether LLMs can maintain stable personas across extended conversations. We address this point using a dual-assessment framework measuring both self-reported characteristics and observer-rated persona expression. Across two experiments testing four persona conditions (default, high, moderate, and low ADHD presentations), seven LLMs, and three semantically equivalent persona prompts, we examine between-conversation stability (3,473 conversations) and within-conversation stability (1,370 conversations and 18 turns). Self-reports remain highly stable both between and within conversations. However, observer ratings reveal a tendency for persona expressions to decline during extended conversations. These findings suggest that persona-instructed LLMs produce stable, persona-aligned self-reports, an important prerequisite for behavioral research, while identifying this regression tendency as a boundary condition for multi-agent social simulation.

We introduce a novel operator to describe a random walk process on a simplicial complex. Walkers are allowed to wonder across simplices of various dimensions, bridging nodes to edges, and edges to triangles, via a nested organization that hierarchically extends to higher structures of arbitrary large, but finite, dimension. The asymptotic distribution of the walkers provides a natural ranking to gauge the relative importance of higher order simplices. Optimal search strategies in presence of stochastic teleportation are addressed and the peculiar interplay of noise with higher order structures unraveled.

Carbon monoxide (CO) is a significant indicator gas with considerable application value in atmospheric monitoring, industrial production and medical diagnosis. Its fundamental vibrational band locates around 4.6 $\upmu$m and has larger absorption line strength than that of overtone band, which is more suitable for the precise identification and concentration detection of CO. In this paper, the up-conversion detection is employed to convert the mid-infrared absorption signal obtained by TDLAS to the visible light band, then a silicon-based detector is utilized for detection. By which, we can achieve the highest sensitivity of 79.6 ppb under the condition of cavity-free in-situ with an absorption range length of only 0.14 m. Furthermore, the single-photon level real-time detection of CO concentration after the diffuse reflection is realized by using SPAD. This work demonstrates the merits of the up-conversion detection in terms of its functionality at room temperature and capacity for sensitivity detection. Furthermore, it presents a design and optimization methodology that has the potential to underpin the advancement of the method towards more practical applications, like industrial process monitoring, medical diagnosis and so on.

We consider a general class of round-robin tournament models of equally strong players. In these models, each of the $n$ players competes against every other player exactly once. For each match between two players, the outcome is a value from a countable subset of the unit interval, and the scores of the two players in a match sum to one. The final score of each player is defined as the sum of the scores obtained in matches against all other players. We study the distribution of extreme scores, including the maximum, second maximum, and lower-order extremes. Since the exact distribution is computationally intractable even for small values of $n$, we derive asymptotic results as the number of players $n$ tends to infinity, including limiting distributions, and rates of convergence.

We consider stochastic particle dynamics on hypersurfaces represented in Monge gauge parametrization. Starting from the underlying Langevin system, we derive the surface Dean-Kawasaki (DK) equation and formulate it in the martingale sense. The resulting SPDE explicitly reflects the geometry of the hypersurface through the induced metric and its differential operators. Our framework accommodates both pairwise interactions and environmental potentials, and we extend the analysis to evolving hypersurfaces driven by an SDE that interacts with the particles, yielding the corresponding surface DK equation for the coupled surface-particle system. We establish a weak uniqueness result in the non-interacting case, and we develop a finite-volume discretization preserving the fluctuation-dissipation relation. Numerical experiments illustrate equilibrium properties and dynamical behavior influenced by surface geometry and external potentials.

Traditional computational fluid dynamics and physics-informed neural networks (PINNs) often suffer from high computational cost, mesh sensitivity, and reduced accuracy for strongly nonlinear and time-dependent flows. To address these limitations, we propose \textit{PhysicsFormer}, a simple and efficient Transformer-based physics-informed neural network framework for complex fluid flow simulations. The proposed architecture employs encoder--decoder multi-head attention to capture long-range temporal dependencies and enhance spatio-temporal information propagation. Unlike conventional multilayer perceptron-based PINNs, \textit{PhysicsFormer} utilizes pseudo-sequential spatio-temporal representations together with a dynamics-weighted loss formulation to improve convergence, stability, and predictive accuracy. Owing to its lightweight architecture and parallel learning strategy, the proposed framework achieves faster training and lower computational cost than existing Transformer-based PINN models. The performance of the proposed framework is demonstrated on the convection equation, Burgers' equation, lid-driven cavity flow at $Re=100$, and inverse Navier--Stokes and flow reconstruction problems for flow past a circular cylinder at $Re=100$ and $Re=3900$. For the inverse Navier--Stokes problem at $Re=100$, the proposed framework simultaneously reconstructs the flow field and identifies governing equation parameters with nearly $0\%$ absolute error under both clean and noisy data conditions. Furthermore, for the high-Reynolds-number case at $Re=3900$, \textit{PhysicsFormer} accurately reconstructs the velocity and pressure fields using only $25$ spatial measurements per snapshot over $100$ temporal snapshots. The obtained results demonstrate that \textit{PhysicsFormer} provides an accurate, robust, and computationally efficient framework for complex time-dependent fluid flow problems.

Synthetic Data Generation (SDG) can be used to facilitate privacy-preserving data sharing. However, most existing research focuses on privacy attacks where the adversary is the recipient of the released synthetic data and attempts to infer sensitive information from it. This study investigates quality degradation attacks initiated by adversaries who possess access to the real dataset or control over the generation process, such as the data owner, the synthetic data provider, or potential intruders. We formalize a corresponding threat model and empirically evaluate the effectiveness of targeted manipulations of real data (e.g., label flipping and feature-importance-based interventions) on the quality of generated synthetic data. The results show that even small perturbations can substantially reduce downstream predictive performance and increase statistical divergence, exposing vulnerabilities within SDG pipelines. This study highlights the need to integrate integrity verification and robustness mechanisms, alongside privacy protection, to ensure the reliability and trustworthiness of synthetic data sharing frameworks.

Density functional theory calculations are conducted to understand and reveal the origin of the complex shear strain morphology and of the polar Moiré topological pattern recently observed in twisted BaTiO$_3$ bilayers. Our first-principles calculations, along with an original analysis of them allowing the decomposition of forces into the acoustic and optical contributions, point out to the occurrence of forces mostly acting on the {\it acoustic-related} motions to produce the standing waves of the shear strain. Such acoustic waves naturally generate a striking self-organization of the shear strains, and hence create a peculiar gradient of these shear strains. A Moiré dipole pattern, consisting of the interpenetrated arrays of vortices and antivortices made of the electric dipoles, then mostly arises due to the coupling of this gradient of the shear strain with the electric dipoles. Furthermore, other forces, namely acting on the motions associated with the {\it optical phonons}, could also play a role in the formation of these polar vortices and antivortices, but at a smaller extent.

Serotonin (5-hydroxytryptamine) is a major neurotransmitter whose release from densely distributed serotonergic varicosities shapes plasticity and network integration throughout the brain, yet its extracellular dynamics remain poorly understood due to the sub-micrometer and millisecond scales involved. We develop a mathematical framework that captures the coupled reaction-diffusion processes governing serotonin signaling in realistic tissue microenvironments. Formulating a two-dimensional compartmental-reaction diffusion system, we use strong localized perturbation theory to derive an asymptotically equivalent set of nonlinear integro-ODEs that preserve diffusive coupling while enabling efficient computation. We analyze period-averaged steady states, establish bounds using Jensen's inequality, obtain closed-form spike maxima and minima, and implement a fast marching-scheme solver based on sum-of-exponentials kernels. These mathematical results provide quantitative insight into how firing frequency, varicosity geometry, and uptake kinetics shape extracellular serotonin. The model reveals that varicosities form diffusively coupled microdomains capable of generating spatial "serotonin reservoirs," clarifies aspects of local versus volume transmission, and yields predictions relevant to interpreting high-resolution serotonin imaging and the actions of selective serotonin-reuptake inhibitors.

We classify the Fano and reflexive polytopes that arise from quasi-finite Feynman integrals. These polytopes appear as scaled Minkowski sums of the Newton polytopes associated with the Symanzik graph polynomials. For one-loop graphs and multiloop sunset graphs, we identify the Fano and reflexive cases by computing the number of interior points from the associated bivariate Ehrhart polynomials. More generally, we utilize the properties of Symanzik polynomials and their symmetries to conduct a direct search over all Feynman graphs in generic kinematics with up to ten edges and nine loops. We find that such cases are remarkably sparse: for example, we find only two two-dimensional reflexive polytopes, three three-dimensional reflexive polytopes, and four three-dimensional Fano polytopes. We also reveal a surprising feature of one-loop $N$-gon integrals in higher dimensions: their associated reflexive polytopes encode degenerate Calabi--Yau $(N-2)$-folds. We further analyze the geometric structures encoded by these polytopes and exhibit explicit connections with del Pezzo surfaces, $K3$ surfaces, and Calabi--Yau threefolds. Since reflexive polytopes naturally correspond to Calabi--Yau varieties, our classification demonstrates that quasi-finite Feynman integrals, with reflexive polytopes, are intrinsically linked to Calabi--Yau period integrals.

A Pythagorean scale is a mathematical encoding of a musical scale as a finite list of numbers of the form 3^b/2^a. Previous work of the first author discussed the 2-step property as a way to measure which Pythagorean scales are the most "evenly-spaced." In this paper, we give a mathematician's account of the characterization of the Pythagorean scales that have the 2-step property; compellingly, the list includes the 5-note, 7-note, and 12-note Pythagorean scales, which are well-known as the pentatonic, diatonic, and chromatic scales of music theory. (After this preprint was initially posted, it was brought to our attention that these results are not new: they have previously appeared in the work of Carey and Clampitt, and related work has been done by several other members of the music theory community, now cited below. We leave this preprint available because it is written for mathematicians with no musical background, and as such may provide helpful exposition for some audiences, but we no longer make any claim to originality of the content.)

We find the atomic response to the intense femtosecond laser pulse via solving numerically the three-dimensional non-stationary Schrödinger equation (TDSE) for a model atom and calculating its dipole moment. For weak quasi-static fields, the response is well described by a perturbation approach, but for intensities higher than about $0.6 \, \, 10^{14}$ W/cm$^2$ the accuracy of this description is unsatisfactory, regardless of the order of non-linearity taken into account. We suggest fitting the numerical TDSE solution results with a Padé expansion, and show that this approximation describes the response well both in the perturbative regime and beyond it for intensities approximately up to $1.4 \, \, 10^{14}$ W/cm$^2$. To consider the non-perturbative nonlinearity beyond the quasi-static limit we use the model of nonlinear oscillator with the restoring force defined by the found Padé expression. Our model fails to predict the behaviour of the nonlinear refractive index in the nonperturbative domain, but it describes well the nonperturbative growth of the efficiency with the laser intensity for other nonlinear optical processes, namely, the third and fifth harmonic generation in the IR field and the optical rectification in a two-color field.

Pulsars emit beams of radiation that reveal the extreme physics of neutron star magnetospheres. Yet, their understanding remains incomplete. Recent global Particle-in-Cell (PIC) simulations have raised several questions that led us to question their validity and their extrapolation to realistic particle Lorentz factors, electric and magnetic fields. We want to generate realistic sky maps of high-energy radiation from first principles. We propose a novel method to study the Equatorial Current Sheet (ECS) where most of the particle acceleration and the high-energy radiation is expected to originate. We first determine its shape and external magnetic field with a steady-state ideal force-free solution. Then, we consider the extra electric and magnetic field components that develop when dissipation is considered. Finally, we study the particle acceleration and radiation that is due to these extra field components for realistic field and particle parameters. We generate realistic sky maps of high-energy radiation and compare them with those obtained via PIC simulations. These sky maps may also be closely reproduced using the ECS of the split-monopole solution beyond the light cylinder. The ECS is probably stabilized by the normal magnetic field component that is due to the global magnetospheric reconnection. Our method helps us better understand the origin of the pulsed high-energy radiation in the pulsar magnetosphere.

We present the first theoretical results of the magnetic dipole (M1) $γ$-ray strength function ($γ$SF) for actinide nuclei within the shell-model Monte Carlo (SMMC) method. We observe a low-energy enhancement (LEE) in the M1 $γ$SFs of the six nuclei studied here, which serves as the first evidence, theoretical or experimental, that the LEE persists in the actinides. We also identify a scissors mode resonance in all six nuclei, which we compare with recent Oslo-method experiments.

Membrane proteins often form dimers and higher-order oligomers whose stability and spatial organization depend sensitively on their lipid environment. To investigate the physical principles underlying this coupling, we employ a lattice Monte Carlo model of ternary lipid mixtures that exhibit liquid-disordered ($L_d$) and liquid-ordered ($L_o$) phase coexistence. In this framework, proteins are represented as small membrane inclusions with tunable nearest neighbor interactions with both lipids and other proteins, allowing us to examine how protein-lipid affinity competes with protein-protein interactions and lipid-lipid demixing. We find that the balance of these interactions controls whether proteins remain dispersed, assemble into small oligomers, or form large stable clusters within $L_o$ domains, and that increasing the protein concentration further promotes coarsening of the ordered phase. To incorporate ligand-regulated activation, we extend the model to a kinetic Monte Carlo scheme in which proteins stochastically switch between inactive and active states with distinct affinities. The inverse switching rate, relative to the time required for a protein to diffuse across the characteristic size of the $L_o$ domains, governs the aggregation behavior. Rapid switching yields only transient small oligomers, slow switching reproduces the static limit with persistent large clusters, and intermediate rates produce broad cluster-size distributions. These results highlight the interplay between lipid phase organization, protein-lipid affinity, and activation dynamics in regulating membrane protein oligomerization, a coupling that is central to signal transduction and membrane organization in living cells.

The generic shape of the single-time and two-time correlators in non-equilibrium phase-ordering kinetics with ${z}=2$ is obtained from the co-variance of the four-point response functions. Their non-equilibrium scaling forms follow from a new non-equilibrium representation of the Schrödinger algebra.

The scaling functions of single-time and two-time correlators in systems undergoing non-equilibrium critical dynamics with dynamical exponent ${z}=2$ are predicted from a new time-dependent non-equilibrium representation of the Schrödinger algebra. These explicit predictions are tested and confirmed in the ageing of several exactly solvable models.

We present evidence of an extreme scattering event (ESE) toward PSR J2313+4253 using high-cadence observations taken with the Green Bank Observatory 20m telescope. The high density of observations in time allow for detailed tracking of the event. We observe a pair of spikes along with the characteristic drop in scintillation bandwidth that is expected during an ESE. This pattern implies that the structures predominantly responsible for scattering occur at different distances than those from previous and subsequent epochs. A secondary spectrum processed during the event shows a detached feature similar to those found in double lensing events from previously observed ESEs. We measure this event as originating from a scattering region with a distance of 1.04(1) kpc, a transverse size of 15 AU, and a duration of approximately 220 days. These rare events provide opportunities to study the properties of small-scale structures in the ISM.

In this work, expanding on previous analyses, we employ an effective Lagrangian approach to investigate the mass spectrum of scalar and pseudoscalar mesons at finite temperature, above the (pseudo-)critical temperature $T_c$, in a "realistic" $N_f = 2 + 1$ flavor scenario with degenerate $up$ and $down$ quarks and a heavier $strange$ quark: $0 < m_u = m_d \ll m_s$. The model's predictions are then critically compared with available lattice QCD results (where meson screening masses are extracted from chiral susceptibilities, which correspond to two-point correlation functions of suitable interpolating operators), looking, in particular, for signatures of the breaking of the $U(1)$ axial symmetry above $T_c$.

In this paper, we show that the chiral soliton lattice (ChSL) is, in a precise sense, a universal feature of the low-energy limit of QCD minimally coupled to Maxwell theory. Here, we disclose that not only can the ChSL be obtained from the gauged Skyrme model in $3+1$ dimensions, including the back-reaction of the Maxwell $U(1)$ gauge field, we also demonstrate that the ChSL remains unchanged when higher-order terms arising from QCD, specifically the sub-leading corrections in the 't Hooft large $N_c$ expansion, are included. By considering a suitable ansatz adapted to describe topological solitons at finite baryon density in a constant magnetic field, the generalized Skyrme model coupled to the Maxwell theory is reduced to the effective Lagrangian of the ChSL phase, which describes a lattice of domain walls made of hadrons. One of the key points in this construction is the fact that even when the usual topological charge density vanishes, the presence of the Callan-Witten term in the topological charge density allows for a non-vanishing baryon number. In the present approach, the magnetic field can be external, as is usually assumed for the ChSL, or it can be self-consistently generated by the hadronic layers themselves. Finally, we show how our formulation allows us to study the coupling of the ChSL with quark matter. In particular, we derive the exact analytical spectrum of the Dirac equation in the high-density limit, providing a microscopic characterization of the fermionic excitations within the inhomogeneous hadronic background provided by the ChSL. The comparison of the present spectrum of the Dirac operator within the ChSL with the spectrum of the usual Dirac operator in a constant magnetic field discloses the fundamental role of both the quark-Skyrmion coupling and the hadronic profile in opening a gap and generating a shift in the spectrum itself.

Given a submanifold $M\subset \mathbf{R}^ν$, a curve $γ:I\to M$ and tangent vectors $v$ along $γ$, we roll the tangent space along $γ$. In doing so, we get an imprint/trace of $γ$ on the tangent space, as well as an imprint/trace of the tangent vectors. We show that for a vector field $v$ along $γ$, the imprint/trace of its covariant derivative is the ordinary derivative of its imprint/trace vector field. It then follows easily that $v$ is a set of parallel vectors along $γ$ if and only if their imprint/trace on the (affine) tangent space is constant and that $γ$ is a geodesic if and only if its trace on the tangent space is a straight line.

While scandium-doped aluminum nitride (AlScN) exhibits robust ferroelectricity and excellent thermal stability, its utility is limited by an exceptionally high coercive field ($E_c$) for polarization switching. Unraveling the atomistic switching dynamics is therefore critical for tailoring $E_c$. Here, we combine density functional theory and machine-learning molecular dynamics to elucidate the polarization switching mechanisms in AlScN over various Sc concentrations and applied electric fields. We find that excessive lattice strain strictly prohibits collective polarization switching, but the pre-existing domain walls relieve strain and lead to a distinct switching dynamics -- dictating a field-dependent switching mechanism. At low electric fields, switching occurs via gradual domain-wall propagation consistent with the Kolmogorov-Avrami-Ishibashi model. In contrast, high fields stimulate additional nucleation, driving a rapid, homogeneous reversal process described by the simultaneous non-linear nucleation and growth model. These findings highlight the critical role of domain-wall dynamics and suggest domain engineering as a viable strategy to tailor coercive fields in AlScN and related ferroelectrics.

We investigate monotonicity properties of eigenvalues of the Dirichlet Laplacian in polyhedral layers of fixed width. We establish that eigenvalues below the essential spectrum threshold monotonically depend on geometric parameters defining the polyhedral layer, generalizing previous results known for planar V-shaped waveguides and conical layers. Moreover, we demonstrate non-monotone spectral behavior arising from asymmetric geometric perturbations, providing an explicit example where unfolding the polyhedral layer unexpectedly leads to the emergence of discrete eigenvalues. The limiting behavior of eigenvalues as the geometric parameters approach critical configurations is also rigorously analyzed.

This study explores the scattering dynamics of kinks within a nonlinear system governed by a parameterized potential $U_λ(χ)$, examining the distinct behaviors of small and large kinks across a range of $λ$ values and initial velocities. For small kinks, we investigate the critical velocity for separation, the influence of vibrational modes, resonance phenomena, and the conditions under which large kinks emerge from collisions. Our findings reveal that the critical velocity exhibits a non-monotonic dependence on the parameter $λ$, reflecting the evolving stability of small kinks, while the decreasing frequency of vibrational modes with increasing $λ$ diminishes resonance effects, leading to simpler scattering dynamics at higher $λ$. The formation of large kinks from small kink collisions is favored at lower $λ$, where the mass difference between small and large kinks is reduced. Conversely, large kink scattering consistently results in the production of small kinks, with the number of small kink pairs growing as both $λ$ and initial velocity increase, a process driven by energy transfer from the translational modes of large kinks to the potential energy required for small kink creation. The absence of vibrational modes in large kinks contrasts with their presence in small kinks, where such modes give rise to complex phenomena like bion formation and resonance. These results underscore the pivotal role of $λ$ in shaping kink interactions and offer valuable insights into the dynamics of topological defects in nonlinear systems, with potential implications for understanding similar phenomena in condensed matter physics and related fields.

The solar spectral irradiance (SSI) depicts the spectral distribution of solar energy flux reaching the top of the Earth's atmosphere. Daily SSI measurements constitute a matrix with spectrally (rows) and temporally (columns) resolved solar energy flux measurements. The most recent SSI measurements have been made by NASA's Total and Spectral Solar Irradiance Sensor-1 (TSIS-1) Spectral Irradiance Monitor (SIM) since March 2018. This data has considerable missing data due to both random factors and instrument downtime, a periodic trend related to the Sun's cyclical magnetic activity, and varying degrees of correlation among the spectra, some approaching unity. We propose a low-rank matrix factorization method for SSI reconstruction that incorporates autoregressive temporal regularization, periodic spline detrending, and cross-spectral covariance information. The method is implemented as a two-stage procedure designed to address scattered missingness and extended downtime missingness, respectively, and is fitted using efficient alternating optimization algorithms. We further accompany the reconstructed SSI values with a distribution-free interval estimation procedure based on conformal prediction. Through synthetic experiments and real-data analyses, we compare this method with Gaussian process regression, linear time series smoothing, and existing matrix-completion approaches in terms of imputation accuracy, interval coverage, interval length, and computational efficiency. The results show that exploiting the periodic, temporal, and cross-spectral structure of SSI substantially improves reconstruction performance and yields calibrated uncertainty intervals, producing a reconstructed SSI data product suitable for downstream climate science studies.

A wide range of phenomena, from explosive transients to active galactic nuclei, exhibit variability at radio wavelengths on timescales of a few years. Characterizing the rate and scale of variability in the radio sky can provide keen insights into dynamic processes in the Universe, such as accretion mechanics, jet propagation, and stellar evolution. We use data from the first two epochs of the Very Large Array Sky Survey (VLASS) to conduct a census of the variable radio sky. Approximately $3,600$ compact sources are found to significantly vary in brightness during the $\sim2.5\,$ years between observations. In this work we focus on sources that are detected in both VLASS epochs, but estimate there may be $>10,000$ additional variable radio sources in VLASS that are only detected in either the first or second epoch. For objects detected in both epochs whose mean flux density across the two epochs, $μ_{S}$, is brighter than $20\,$mJy, $5\,$% show brightness variations $>30\,$%, rising to $9\,$% at $μ_{S}>300\,$mJy. We analyze the redshift distributions, infrared colors, and $γ$-ray properties of the variable radio sources, finding that most have multiwavelength characteristics that are consistent with blazars and quasars. Blazars in particular are found to be overrepresented among the variable radio sources, and the largest absolute changes in flux density are produced by blazars. The largest fractional changes in brightness are exhibited by galactic sources. We discuss our results, including some of the more interesting and extreme examples of variable radio sources identified, as well as future research directions.

In this note we consider examples of decomposition (in which a local QFT is equivalent to a disjoint union of multiple independent theories, known as universes) where there is a continuous familiy of universes, rather than a finite or countably infinite collection. In particular, this allows us to consistently eliminate all instantons in a local QFT via a suitable topological gauging of the (-1)-form symmetry. In two-dimensional U(1) gauge theories, this is equivalent to changing the gauge group to R. This makes both locality as well as the instanton restriction explicit. We apply this to clarify the Gross-Taylor string interpretation of the decomposition of two-dimensional pure Yang-Mills. We also apply decomposition to study two-dimensional R gauge theories, such as the pure R Maxwell theory, and two-dimensional supersymmetric gauged linear sigma models whose gauge groups have factors of R. In that context, we find that analogues of the Witten effect for dyons, here rotating between universes, play a role in relating anomalies of the individual universes to (different) anomalies in the disjoint union. Finally, we discuss limits of the Tanizaki-Unsal construction, which accomplish instanton restriction by topologically gauging a Q/Z (-1)-form symmetry, and speculate in two-dimensional theories on possible interpretations of those limits in terms of the adelic solenoid.