Papers

Super-leading logarithms from Glauber exchange complicate the resummation of non-global observables at hadron colliders. In this Letter, we extend Marzili, a Monte Carlo framework for non-global resummation based on effective field theory, to resum the leading nonzero colour contribution involving two Glauber exchanges. This is the first Monte Carlo resummation of super-leading logarithms. Together with Marzili's treatment of non-global logarithms, this opens a path towards studying their interplay and incorporating Glauber exchange into parton showers.

We construct and analyze a renormalized three-dimensional massive Lee model; its renormalized Hamiltonian is defined intrinsically through an abstract construction which explicitly provides the operator domain, action and a Kre\u\i n-like resolvent formula. Conservation of the total excitation number reduces the spectral analysis of the full Hamiltonian to a sector-wise study of the spectral profile of an explicit operator pencil, playing the role of an operator-valued Weyl function. We construct essential spectrum components in a sector generated by lower excitation sectors and obtain the inclusion in the expected sector-wise HVZ type formula; the full formula is proved in the first two sectors and, under explicit conditions, in every sector. Below the free or one-excitation threshold, the point spectrum in every higher sector is described by a bounded self-adjoint nonnegative Birman–Schwinger operator. In every sector with at least two excitations we prove absence of sub-threshold spectrum for arbitrary coupling when the renormalized gap is not smaller than the boson mass, and under an explicit weak-coupling condition when it is smaller. In the latter case we also derive a sufficient condition for the existence of a simple bound state in the two-excitation sector.

Bound states in the continuum (BICs) enable complete wave confinement within open systems through destructive interference or symmetry protection, giving rise to ideally infinite quality factors and extreme field enhancement. Their practical exploitation, however, is hindered by a fundamental paradox: the same mechanism that suppresses radiation also prevents efficient excitation from the far field. Existing experimental approaches typically overcome this limitation by introducing external coupling channels that inevitably perturb the protected state and reduce its confinement. Here we demonstrate the non-invasive excitation of a symmetry-protected acoustic BIC through nonlinear virtual sources generated directly at the surface of the structure. By focusing time-modulated ultrasonic beams onto a metamirror, nonlinear demodulation produces localized low-frequency sources whose spatial phase matches the symmetry of the target mode while avoiding any physical coupling to the resonator. This approach injects energy into the BIC without opening additional radiative channels, preserving its intrinsic non-radiative character. We develop a theoretical framework describing the formation and symmetry protection of the mode, realize a compact experimental implementation through symmetry reduction, and directly measure the confined pressure field and its quality factor. Our results establish nonlinear virtual sources as a route to accessing symmetry-protected states in open systems while maintaining their exceptional confinement properties, providing a general strategy for wave manipulation and high-sensitivity resonant devices across physical platforms.

Preparation contextuality is often manifested operationally through a quantitative advantage over preparation-noncontextual models in information-processing tasks, yet quantum theory typically falls short of perfect success. Here we introduce a parity-oblivious Hidden Matching task that instead yields an all-vs-nothing manifestation of preparation contextuality. Alice encodes an $n$-bit string so that her message reveals no information about any input parity other than the two-bit parities. Bob, given a perfect matching on the input positions, must output an edge of the matching together with the parity of its two bits. A quantum protocol using a single $\lceil\log_2 n\rceil$-qubit message satisfies the parity-obliviousness constraint and succeeds with certainty. We prove that no preparation-noncontextual model achieves perfect success for any even $n\ge6$. The result holds for arbitrary ontic state spaces and assumes neither outcome determinism nor measurement noncontextuality. For $n=6$ and $n=8$, the optimal noncontextual success probabilities are $4/5$ and $3/4$, respectively, while asymptotically the optimal noncontextual success probability is $1/2+\Theta(1/\sqrt n)$. Our asymptotic upper bound follows from a Fourier-analytic sum rule derived via hypercontractivity on the Boolean hypercube. The resulting separation is qualitative rather than merely quantitative: quantum theory achieves perfect success, whereas preparation-noncontextual models cannot. We aslo show that at $n=8$ the noncontextual bound remains $3/4$ even when Bob is restricted to just suitable $4$ of the $105$ possible perfect matchings, bringing the effect within experimental reach.

We resolve an open problem posed by Frank–Loss. Let $n\ge 3$ and let $\varphi\in L^p(\mathbb{S}^n)$, with $\frac{n}{n-1}<p<\infty$, be a nontrivial Dirac zero mode on $\mathbb{S}^n$, i.e. a nonzero spinor satisfying \begin{equation*} D\varphi = iA\cdot\varphi, \end{equation*} where $D$ is the Dirac operator and $A$ is a vector field with $\mathrm{d} A^\flat\in L^{n/2}$. We prove the sharp lower bound \begin{equation*} \|\mathrm{d} A^\flat\|_{\frac{n}{2}} \ge 2\left[\frac{n}{2}\right]^{-\frac12}\frac{n-1}{n-2}S_n = \left[\frac{n}{2}\right]^{-\frac12}\frac{n(n-1)}{2}\omega_n^{\frac{2}{n}}. \end{equation*} Equality is attainable if and only if $n$ is odd; in that case, modulo conformal and gauge transformations, $\varphi$ is a Killing spinor and $A$ is a real multiple of the Reeb field associated with $\varphi$. The case $n=3$ was proved in our recent paper using a different method. In the paper we divide the remaining cases into 3 cases: i) $n\ge 5$ is odd, ii) $n\ge 5$ is even and iii) $n=4$. All these cases need to use different methods. For $n\ge 5$, the argument crucially reduces to an improved Sobolev inequality on $\mathbb{S}^n$ under a barycenter constraint. Specifically, for $u\in W^{1,2}(\mathbb{S}^n)$ we consider \begin{equation*} \mathfrak{a}_n := \inf\Bigg\{ \frac{ \int \Big(|\nabla u|^2 + \frac{n(n-2)}{4}u^2\Big) - \frac{n(n-2)}{4}\omega_n^{\frac{2}{n}}\|u\|_{\frac{2n}{n-2}}^2 }{ \omega_n^{\frac{2}{n}}\|u\|_{\frac{2n}{n-2}}^2 - \int u^2 } \,\Bigg|\, \int x|u|^{\frac{2n}{n-2}}=0,\ \omega_n^{\frac{2}{n}}\|u\|_{\frac{2n}{n-2}}^2 - \int u^2>0 \Bigg\}, \end{equation*} and we obtain the following universal estimate \begin{equation*} \mathfrak{a}_n > \frac{n(n-2)}{4(n^2-3n+1)}, \end{equation*} which is enough for our aim. Determining the exact value of $\mathfrak{a}_n$ remains open.

We investigate static, charged, asymptotically flat black holes in logarithmic nonlinear electrodynamics (LNED) within the $(Q,\epsilon)$ parameter space. We distinguish three phase structures: the horizon geometry, the background circular null orbits, and the circular photon orbits of the effective optical geometry. All share a zero-radius boundary $Q_{nc}(\epsilon;M)=\gamma M^{2/3}\epsilon^{1/6}$, but possess distinct critical structures: the extremal curve $Q_{ext}(\epsilon;M)$ and the background merger curve $Q_{m}(\epsilon;M)$ both terminate at the bifurcation point $(Q_{b},\epsilon_{b})$, located at $r=0$. In contrast, the effective photon-orbit merger curve $Q_{m}^{ph}(\epsilon;M)$ does not pass through this point. For $\epsilon\ge\epsilon_{b}$, approaching $Q_{nc}$ shrinks the horizon to zero radius, resulting in black points with non-zero, quantum-corrected entropy. Their Hawking temperature vanishes at the bifurcation point and diverges for $\epsilon>\epsilon_{b}$, except when $\eta\delta=1$, where the temperature at the bifurcation point also diverges. The background potential $V_{eff}^{bg}(r)$ develops an infinite barrier at $r=0$ without local extrema, acting as a perfect repeller. In contrast, the photon potential $V_{eff}^{ph}(r)$ is regularized with a maximum at a finite radius, acting as a partial reflector. Consequently, the black points retain photon spheres of finite radius. Away from $Q_{nc}$, for $\epsilon<\epsilon_{b}$, both geometries support horizonless structures above $Q_{ext}$; for $\epsilon\ge\epsilon_{b}$, only the optical geometry does so in the region $Q_{nc}<Q<Q_{m}^{ph}$. Non-radial geodesics are blocked from the singularity and can form metastable bound states, while radial geodesics either reach $r=0$ or escape to infinity. The critical impact parameter encodes both gravitational and optical-geometry effects, probing the distinct phase structures.

Interstellar extinction at high Galactic latitude is often traced by thermal dust emission, but the conversion from infrared surface brightness to reddening is sensitive to grain properties and temperature. We test dust-scattered far-ultraviolet (FUV) and near-ultraviolet (NUV) diffuse emission as a high-resolution extinction tracer towards the North Galactic Pole (NGP), where E(B-V) < 0.1 mag. Using the GALEX diffuse maps of Murthy (2014), we build FUV and NUV intensity maps at 6' resolution over the region b > 70 deg and compare them with the Planck E(B-V) map at matched resolution. A direct pixel-to-pixel regression gives only moderate correlations (rho = 0.536 for FUV, 0.243 for NUV) owing to high per-pixel scatter from H2 fluorescence, line emission, and photon-counting noise; we therefore construct per-pixel GALEX uncertainty maps and apply a centroid-fitting method that fits the mean intensity in bins of E(B-V) after rejection of outliers via iterative sigma-clipping, recovering tight relations (rho = 0.993 for FUV, 0.976 for NUV). We find the best-fit relations for the FUV and NUV intensity per 6'x6' pixel: FUV = 2285.3 E(B-V) + 278.6 and NUV = 1517.6 E(B-V) + 547.2 (photons/cm^2/s/sr/A), inverted to produce a 601x601 GALEX reddening map. GALEX E(B-V) correlates strongly with HI column density from the all-sky HI4PI survey (rho = 0.991). We validate the maps using SDSS quasars as extragalactic extinction calibrators: quasar extinctions from the GALEX and Planck maps agree with a correlation of 0.99 and a slope of 0.986. Comparison with the Pan-STARRS1 stellar reddening map of Schlafly et al. (2014) shows the GALEX-based values have a smaller mean difference (0.039 mag) than the Planck-based values (0.064 mag). These results establish dust-scattered FUV diffuse emission as a viable alternative to thermal-dust extinction maps at high Galactic latitude.

The Surface Water and Ocean Topography (SWOT) mission offers unprecedented freshwater monitoring capabilities through its innovative wide-swath measurement system, which generates several data products, including the high-resolution pixel cloud (PIXC) product. However, the native PIXC water classification remains prone to systematic misclassification in urban environments, where strong radar returns from non-water surfaces are the predominant error sources. We present a deep learning approach that enhances land-water classification directly on SWOT PIXC data based on a dynamic graph convolutional neural network that simultaneously exploits spatial proximity and feature similarity to derive binary land-water class labels. The model is trained on a full year of PIXC data for the Dallas-Fort Worth metropolitan area using pixel-level ground-truth class labels derived from the DSWx-HLS product, which provides water-class labels based on Landsat and Sentinel-2 at a 30\,m spatial resolution. Against the DSWx-derived reference, the proposed method increases the mean scene-level F1 score against the DSWx-derived reference from 0.52 to 0.86 on the temporally independent test set and from 0.43 to 0.74 on the spatiotemporal test set, relative to the native PIXC classification. These results demonstrate that dynamic graph neural networks are well-suited to the irregular, point-cloud-like structure of PIXC data and offer a scalable path toward more reliable urban flood monitoring and freshwater mapping at the high spatial resolution provided by the SWOT PIXC product.

The radio – soft $\gamma$-ray data of the Galactic black hole binary XTE J1859+226 showed that discrete jets are launched when the inner radius of the accretion disk ($R_{\rm in}$) rapidly approaches the innermost stable circular orbit (ISCO). Given the correlations among the X-ray fractional variability amplitude (rms), $R_{\rm in}$, and the X-ray hardness, previous phenomenological findings related to jet ejections (“jet line” and sharp drops of rms) also indicate that the rapid shrinkage of $R_{\rm in}$ down to the ISCO turns on the jet formation. In order to make clear how these properties appear in other objects, we investigated the X-ray and radio data of XTE J1550-564, GX 339-4, and MAXI J1820+070. We found that all the four sources show drops of $R_{\rm in}$ and rms 1-10 days ahead of a jet activity, and exhibit no huge jumps of the accretion rates prior to jet ejections. XTE J1859 and MAXI J1820 show the jet activities under sub-Eddington accretion. Models for the jet production that require an enhancement of $\dot{M}$ or a super-Eddington accretion rate are unlikely. Another behavior common to multiple sources is the curved shape of the rms–$R_{\rm in}$ correlation. Therefore, monitoring of $R_{\rm in}$ seems to be suitable to predict the timing of jet ejections. When both $R_{\rm in}$ and rms continuously decrease and when $R_{\rm in}$ is about to reach the ISCO, alerts can be circulated as a “jet forecast” for triggering Target-of-Opportunity observations.

An effective field theory (EFT) of gravity with a cubic Riemann invariant coupled to an axion-like field is investigated and shown to propagate no additional independent low-energy degrees of freedom. This interaction generates a curvature-induced scalar profile around black holes, characterised by a secondary axion charge fixed by regularity of the axion field at the horizon, while the requirement of a regular event horizon constrains the asymptotic axion background. We construct the corresponding black hole solutions and show that the backreaction of the axion field could affect the metric only at subleading order in the EFT expansion. The modified geometry impacts black hole thermodynamics and Hawking evaporation, thus providing a controlled realisation of black holes with higher-curvature contributions and secondary axion hair motivated by ultraviolet physics. The modified Hawking temperature allows for the existence of black hole remnants at the end of the evaporation within the regime of validity of the EFT.

Several external sources (the rings, the satellites, cometary impacts, interplanetary dust particles) supply material to the upper atmosphere of Saturn. The signature of this external influx has been documented on the ionospheric electronic and ionic densities, and in the stratosphere on oxygenated molecules (CO, CO2, H2O). We search for the chemical signature of the external sources in nitrogen-bearing species in Saturn's stratosphere. We have targeted the HCN(4-3) rotational line and mapped its emission line at the planet limb with ALMA in 2018 with configuration C43-3, providing a synthetic beam of 0.61"x0.50". HCN was detected at all observable latitudes from 20{\deg}S to 60{\deg}N. The HCN abundance was measured at two independent pressure levels, 0.1 and 1 hPa. The measured volume mixing ratios are latitudinally uniform within uncertainties at both pressure levels. The mean vmr is $(7\pm 2)\times 10^{-11}$ and $(4\pm 1)\times 10^{-12}$ at 0.1 and 1 hPa respectively. This corresponds to a mean column-density of $(4\pm 1)\times 10^{12}$ cm$^{-2}$, and a total nitrogen mass of $(3.7 \pm 0.9)\times 10^{10}$ g. The steep vertical profile suggests that another loss mechanism, possibly sticking or heterogeneous chemistry on aerosols, is active besides photodissociation. The huge influx of material detected in the ring plane by Cassini left no detectable chemical signature on HCN. The detected HCN mass seems compatible with several sources: the ring rain at mid-latitudes, Enceladus, or an old cometary impact. The detected HCN could also be a chemical product of internal N2 transported from the deep atmosphere up to the stratosphere.

Even-layer topological antiferromagnetic thin films such as MnBi$_2$Te$_4$ exhibit an unconventional layer Hall effect (LHE) arising from a layer-locked Berry curvature. This effect manifests as a layer-polarized anomalous Hall effect that can be controlled by a vertical displacement field. However, achieving a quantized version of the LHE remains experimentally challenging. In this work, we propose that moiré engineering, using an electrostatic superlattice potential from control layers, can realize the quantum layer Hall effect (QLHE). Specifically, by placing moiré control layers in close proximity to the surfaces of a MnBi$_2$Te$_4$ thin film without breaking $PT$ symmetry, the resulting system exhibits a vanishing net Hall conductance but a quantized layer Hall conductance of $e^2/h$. A weak gate electric field then breaks $PT$ symmetry and drives the system into a layer-polarized quantum anomalous Hall (QAH) phase. Furthermore, when a single control layer is introduced on only one surface, the layer-polarized QAH emerges even in the absence of an external electric field. We identify the microscopic origin of the QLHE as an emergent layer-$U(1)$ gauge field generated by the scalar moiré potential, which in turn produces opposite periodic pseudomagnetic fields on the top and bottom layers. Our work provides a feasible pathway toward realizing the QLHE in antiferromagnetic thin films.

Long gamma-ray bursts (LGRBs) are believed to originate from the core collapse of massive Wolf-Rayet (WR) stars, leading to the formation of a spinning black hole that powers a relativistic jet. The prompt emission is produced once the jet emerges from the stellar envelope. We perform 2D axisymmetric RHD simulations using the PLUTO code to model semi-self-consistent, accretion-powered jets launched by Kerr black holes. For the two progenitor models, we adopt black hole masses of $4 M_{\odot}$ and $5 M_{\odot}$ corresponding to WR stars of $10 M_{\odot}$ and $25 M_{\odot}$, respectively. Unlike previous studies, our simulations employ continuous jet injection, with the injected power linked to black hole spin and accretion through an empirical relation motivated by GRMHD simulations, enabling a controlled exploration of jet energetics over $10^{48}$-$10^{52}\,\mathrm{erg\,s^{-1}}$. We investigate jet breakout for WR progenitors of $10\,M_{\odot}$ and $25\,M_{\odot}$ and identify a critical spin threshold: jets are choked for $a \leq 0.001$ and successfully break out for $a > 0.001$. The breakout time ($t_B$) shows a correlation with jet luminosity ($L_{\rm jet}$) and spin ($a$), revealing three regimes: Newtonian ($a \lesssim 0.03$), relativistic ($a \gtrsim 0.3$), and intermediate. A dichotomy is observed in jet head velocity at breakout, with $\beta_h \gtrsim 0.8$ for high-spin and $\beta_h \sim 0.35$-$0.8$ for lower spins. In the Newtonian regime, simulations yield $t_B \propto L_{\rm jet}^{-0.48}$, steeper than analytical predictions, with systematically longer breakout times indicating modified jet-head scaling. In the relativistic regime, calibrated analytical models show improved agreement, with simulations indicating efficient jet propagation.

We investigate the twist-4 generalized transverse momentum dependent parton distributions (GTMDs) of $\bar{u}$ and $\bar{d}$ quarks inside the proton at zero skewness by adopting the overlap representation within the light-cone formalism. Using the light-cone wave functions of the proton derived from the baryon-meson fluctuation model in terms of the $|q\bar{q}B\rangle$ Fock states, we calculate the twist-4 GTMDs of $\bar{u}$ and $\bar{d}$ quarks. Additionally, the intricate relations between the GTMDs and the generalized parton distributions are also explored in our research. Numerical results for these twist-4 GTMDs and twist-4 GPDs at zero skewness are analyzed and presented.

Classical simulation of quantum random access memory (QRAM) under noise can be accelerated dramatically by branch pruning: noise histories are sampled as trajectory ensembles, and good branches, whose routing paths avoid every sampled fault, need not be evolved because their final states are analytically predictable. Under amplitude damping this predictability is not automatic, because the no-jump operator $K_0$ acts on every branch at every time slice. Here we give a complete account of damping-channel predictability in bucket-brigade QRAM simulation, for both qutrit and qubit encodings. For the qutrit encoding, $K_0$ is diagonal in the node basis, and the wait state $|W\rangle$ is its fixed point, so a good branch follows the noiseless orbit up to a scalar attenuation. In the qubit encoding, phase-kickback memory fetching between two Hadamard walls makes $K_0$ no longer diagonal, yet the resulting structure is exactly solvable in closed form. Conditional on no jump, the in-branch infidelity of a good branch is second order in the damping rate $\gamma$, with coherent leakage $\sim n^2\gamma^2/4$ per data qubit, and the closed form captures it without approximation. We also revise the pruning criterion for the qubit encoding. The resulting algorithm evolves only the bad branches plus one reference branch and shares every other cost with the full evolution it replaces. It is validated by end-to-end benchmarks with pruned-over-full speedups up to $285\times$ and by trajectory-level tests confirming every closed form to machine precision.

Planetesimal formation via the streaming instability of small pebbles in protoplanetary discs requires enhanced solid concentrations relative to the solar metallicity, $Z\simeq 0.01$. We investigate here whether pile-ups in weak axisymmetric pressure bumps are sufficient to trigger strong particle concentrations via the streaming instability. Using high-resolution 2D shearing box simulations with millimetre-to-centimetre pebbles, we explore the behaviour of the streaming instability in the presence of a non-reinforced pressure bump. We find that even very weak bumps, with gas density amplitudes as low as $A = 0.04$ relative to the background, produce dense particle filaments via the streaming instability for all tested Stokes numbers at solar metallicity in the inner disc. Outer disc regions require slightly stronger bumps ($A \geq 0.14$) to form filaments at a solar metallicity, though the necessary bump amplitude is substantially lowered when the metallicity is increased to $Z = 0.02$. Our results suggest that weak, non-reinforced pressure bumps can act as focal points for planetesimal formation via the streaming instability in small pebbles, in contrast to previous studies which used reinforcement to maintain the pressure bump. Additionally, we introduce a pressure-bump-dependent clumping criterion, $(Z/\chi)_\mathrm{crit} \approx 0.3$, where $\chi = \Pi_\mathrm{min}^2/\Pi_0$ reduces to the background pressure gradient $\Pi_0$ in the absence of a pressure bump. This criterion encapsulates the scale of solid pile-ups at lower pressure gradients and accurately predicts the onset of strong clumping based on the results of our simulations. With pressure bump signatures being common features of observed young discs and magnetohydrodynamical simulations, the results of our 2D simulations imply that weak pressure bumps may be major cradles for planetesimal formation in protoplanetary discs.

The Efimov effect manifests discrete scale invariance through a geometric series of three-body bound states. Analogous discrete scale symmetry has been observed in the Efimovian expansion of scale-invariant strongly interacting Fermi gases. However, it is unclear whether strong correlation is necessary. Here we investigate the spontaneous breaking of continuous scale invariance in a simple driven-dissipative harmonic oscillator whose driving and dissipation parameters scale as $1/t$. By transforming to logarithmic time, we show that the dynamics is governed by a non-Hermitian superoperator whose spectral decomposition reveals the emergence of a pair of eigenmodes with opposite real parts and equal imaginary parts. This signals the spontaneous breaking of continuous scale invariance and gives rise to Efimovian-like oscillations: log-periodic decay oscillations obeying discrete scaling laws. The onset of oscillations coincides with a PT-symmetry breaking transition in logarithmic time. The Efimovian-like oscillations are robust against weak nonlinear interactions and perturbations. Our work implies that the spontaneous breaking of continuous temporal scale symmetry and the emergence of Efimovian-like dynamics can even be observed in a simple driven-dissipative system without many-body interactions.

The short wavelength of terahertz (THz) waves makes the acceleration of electrons, from typical electron gun energies to fully relativistic energies, challenging due to the need to match the velocities over comparably long distances. However, the inherent laser synchronisation of a photogun to the THz drive laser offers significant advantage in applications where timing is critical. We present a novel design process for high-gradient THz-driven dielectric-lined waveguide injectors and demonstrate designs for rectangular and cylindrical geometries. These structures utilize novel tapering and stepping schemes to manipulate the phase velocity, controlling the position of the electron bunch relative to the phase of the accelerating field. We demonstrate a hybrid optimisation method utilizing firstly a multi-objective genetic algorithm based on analytic models of the waveguide accelerating modes, and then high-detail particle-in-cell simulations. Our example designs achieve electron acceleration from 100 keV to 1 MeV over a distance of 20 mm by interacting with a multicycle 0.5 mJ, 0.2 THz pulse, paving the way for the realisation of THz-based injectors. The exit beam shows excellent beam quality with 50 fs bunch lengths, sub 0.5% energy spread and emittances of under 0.15 {\mu}rad. We also present an analysis of the robustness of the designs to errors in machining and operational parameters demonstrating the feasibility of the concept. We show that using multi-objective genetic algorithm optimization and robust design process, we can achieve high-quality 1 MeV beams.

We investigate dynamical dark energy emerging from quantum gravity within the framework of group field theory (GFT) condensate cosmology. We generalise previous models of quantum gravity induced cosmic acceleration by considering a broader parameter space, including an additional scalar matter field besides the relational clock, and accounting simultaneously for the phase dynamics and the contribution of multiple condensate modes. Working in a mean-field approximation with coherent peaked states and restricting to Hermitian GFT interactions, we derive the corresponding effective cosmological dynamics and analyse its late-time behaviour. We show that the system approaches an asymptotic de Sitter regime, dynamically dominated by a single condensate mode, while the approach to this regime can exhibit a non-trivial dynamical dark-energy evolution. In particular, both the condensate phase and subdominant modes can generate deviations from the asymptotic equation of state $w=-1$, including phantom behaviour and, under suitable conditions, a crossing of the phantom divide. The additional scalar matter field enters directly into these conditions, providing a link between the matter content and the quantum gravity induced dark-energy dynamics. These results extend the robustness and generality of the GFT mechanism for dynamical dark energy and provide a basis for confronting the underlying quantum gravity dynamics with cosmological observations.

Accurate prediction of avalanche motion is essential for hazard assessment in mountainous terrain. This study develops and evaluates a physics-informed neural network (PINN) framework for the Savage-Hutter model of depth-averaged granular flow, progressing from 1D analytical verification to 2D experimental validation. First, three 1D problems of increasing complexity were verified against the analytical solution: height prediction with prescribed velocity, velocity prediction with prescribed height, and coupled prediction of both fields using the conservative formulation. The decoupled tests accurately reconstructed the spatio-temporal evolution of each field when the other was prescribed. The coupled formulation learned both fields without prescribed data, achieving mean height and velocity RMSEs of 0.043 and 0.079 in non-dimensional units. A hyperparameter sensitivity study evaluated the effects of network depth, width, collocation density, learning rate, and epochs. The framework was then extended to 2D and validated against laboratory experiments of a cylindrical granular pile collapsing on an inclined plane, with TITAN2D providing numerical comparisons. Purely physics-based training converged to the trivial zero solution; augmenting the loss with 10 sparse training points from final deposit profiles produced a physics-informed, data-assisted hybrid framework. Peak flow depth, depth-averaged velocity, RMSE, and wetted-area IoU evaluated global and local agreement. Global height RMSE ranged from 2.7 to 6.7 mm across four experimental cases, while mean wetted-area IoU ranged from 69 to 81 %, demonstrating consistent performance across variations in pile mass and slope angle.

We develop a rational-function approximation for the structural properties of multicomponent fluids with narrow square-well and square-shoulder interactions, together with weakly nonadditive hard-sphere mixtures. The theory is obtained by reformulating the analytical Percus–Yevick solution for additive sticky hard-sphere mixtures so as to account for finite interaction widths, leading to a unified semianalytical framework for these classes of fluids. The approximation satisfies the exact low-density limit and preserves the continuity of the cavity functions; a simple local correction restores the continuity of their first derivatives. Comparison with Monte Carlo simulations for binary mixtures shows that the theory accurately describes both the radial distribution functions and their Fourier transforms for narrow wells and shoulders and for weak nonadditivity. The proposed formulation extends previous sticky-hard-sphere-based approaches while retaining their analytical simplicity.

The idea of engaging critically and creatively with physics theories is a stretch for many physicists and physics educators. Most physicists become enculturated into the belief that physics definitions, laws, and equations are read from the book of nature. However, this belief obscures how theories are collectively negotiated by people in specific socio-political and personal conditions, and how students' particular ideas and intuitions will inevitably shape their own practice of science. To help students build their skills for collective theory-building, we suggest a pedagogy for physics in which students actively negotiate the laws and definitions of theories.

We develop a holographic dual to the integrable field theories built from $4d$ Chern-Simons theory. The dual theory is a topological string on a generalized Calabi-Yau manifold, which is entirely encoded in a geometric object we call a planar spectral curve. We describe the RG flow for a planar integrable field theory as a geometric flow on the moduli of planar spectral curves. This description is valid at all orders in the 't Hooft coupling. We compute this flow explicitly up to two loops in many examples, and find an exact match with known field theory results. At one loop this includes a wide class of models. At two loops we reproduce the RG flow for the principal chiral model with WZ term, and for a class of integrable $\sigma$-models with target $U(N) \times U(N)$.

We employ a projection operator technique to study the equilibrium phases and the non-equilibrium quench and ramp dynamics of ultracold bosons described by a two-dimensional (2D) Bose-Hubbard model coupled to a high-finesse cavity with competing local short-range and cavity-mediated long-range interactions. Our analysis relies on a systematic elimination of high-energy virtual hopping processes; this enables us to capture the effects of short-range quantum fluctuations on the phase diagram of the model while treating the cavity-induced long-range interaction within mean-field theory. We find that the phase boundaries between the superfluid (SF), supersolid (SS), charge-density-wave (CDW) and Mott insulating (MI) phases are significantly modified by the presence of these fluctuations. We use this approach to study the dynamics of bosons following a quench/ramp from the CDW to the SS and SF phases; our analysis indicates the presence of oscillatory dynamics characterized by a single frequency due to a quench which takes the system near the critical point. In contrast, for a quench deep inside the SF phase, the dynamics involves multiple frequencies. An explicit comparison with Gutzwiller mean-field theory shows the importance of quantum fluctuations in shaping such post-quench dynamics; this feature may be tested experimentally as we discuss. We also study the ramp dynamics of these bosons and identify a bound on the ramp rate above which the present method is expected to produce accurate results.

JWST has uncovered compact high-redshift (z>=4) sources, dubbed Little Red Dots (LRDs), characterised by a distinct V-shaped continuum. Their nature remains debated since broad-line AGN signatures coexist with non-AGN continua, marked by weak X-ray and mid-IR emission. We investigate which properties of LRDs naturally emerge within simulations of massive AGN host galaxies and which require additional physics. We post-process two cosmological zoom-in simulations of the same massive halo, one including black hole growth and AGN feedback (AGNfid) and the other with only star formation and stellar feedback (SFonly). We analyse snapshots spanning z=6-9 to probe different evolutionary stages. Using SKIRTv8, we develop a forward-modelling framework exploring various dust models, dust-to-metal ratios, and intrinsic AGN spectra. We generate mock spectra and images to apply JWST observational LRD selection criteria. Not designed to model LRDs, our AGNfid simulations naturally reproduce their properties: V-shaped continua, compact morphologies with rest-UV complexity, UV luminosities, attenuations, overmassive BHs, sub-Eddington accretion, and Balmer break strengths (~1-2) typical of most LRDs. Spectral decomposition reveals that the rest-UV continuum is dominated by stellar emission, whereas the optical continuum stems from a dust-attenuated AGN. Dust geometry and AGN-to-stellar contribution drive photometric differences between LRDs and Little Blue Dots. Our results suggest that LRDs do not necessarily represent a distinct class of objects. Instead, their defining properties can arise in massive AGN host galaxies from the interplay between stellar emission, an obscured central engine, and dust geometry. Super-Eddington accretion, dust-free gas columns, evolved stellar populations, and photoionisation modelling are required to test whether this framework reproduces the diversity of observed LRDs.

A resonant classical field drives a two-level system coherently and, with ordinary relaxation, produces saturation rather than directional population transfer. Here we show that directionality emerges when the excitation source is retained as a quantum subsystem and subsequently traced out. We model the source as a single-excitation degree of freedom, or equivalently a stream of two-level ancillas, exchange-coupled to a target two-level system. The source first moment generates the usual coherent drive, while its second moments produce upward and downward dissipative channels. For a number-diagonal, fully excited source, the first moment vanishes and only the upward channel remains, yielding monotonic pumping of the target. The same structure follows from both an exact collision map and a fluctuation-regulated second-order quantum master equation. For exponentially decaying source correlations, the pumping rate shows a Lorentzian detuning dependence governed by the correlation time $\tau_c$, accompanied by a dispersive frequency shift. In the presence of thermal relaxation, the steady-state excited-state population can exceed the resonantly driven optical-Bloch limit of one half. Within the fluctuation-regulated master equation, this directional pumping arises as a drive-induced dissipative contribution whose strength and spectral response are controlled by $\tau_c$.

The O-band telecommunication spectral range combines minimal chromatic dispersion with low transmission loss, making it highly suitable for optical communications. Semiconductor telecom lasers utilizing low-dimensional active regions, such as quantum dots, offer low threshold power and high thermal stability. However, long-wavelength quantum dot emitters often suffer from thermal carrier escape through excited states when the energy separation between the ground and excited states is insufficient. Here we demonstrate the optimization of InAs quantum dot emitters grown on InP by molecular-beam epitaxy for O-band laser active regions. By optimizing the design for better carrier capture efficiency and tuning the emission wavelength to the O-band, we show ways of improving the carrier confinement. Absorption spectroscopy on the finalized structure confirms substantial energy separation between the quantum dot ground and excited states, effectively suppressing thermal carrier escape even at elevated temperatures. These results highlight critical design for improving carrier capture and retention in long-wavelength quantum dot lasers.

Light scattering in heterogeneous media underpins a broad range of natural phenomena and optical technologies, yet remains difficult to understand in porous nanocomposites. State-of-the-art theories generally treat these materials as two-phase systems consisting of particles and a matrix, overlooking the air pores that are intrinsically present in porous composites. Here we experimentally determine the scattering coefficients of six BaSO4-acrylic and TiO2-acrylic coatings spanning a range of particle volume fractions and develop a three-phase scattering framework that explicitly accounts for pore-induced scattering. By representing the composite as two coupled scattering subsystems, particle-matrix and particle-air, the framework resolves discrepancies between theory and experiment: conventional two phase models substantially underpredict scattering in BaSO4 coatings while overpredicting scattering in TiO2 coatings, whereas the three-phase model accurately captures the observed trends and reduces the mean absolute logarithmic error from 0.667 to 0.379. This framework identifies air pores as a fundamental and independently controllable contributor to optical scattering, providing new physical insights and design principles for engineering highly scattering porous nanocomposites.

Interatomic potentials are central tools in the atomistic modeling of materials. The atomic cluster expansion (ACE) parameterizes such potentials from ab initio data, conventionally encoding the chemical degrees of freedom with a one-hot representation that yields chemically stratified models. The alternative chemical representations used in on-lattice configurational cluster expansions have not been assessed for interatomic potentials. Here we revisit the multicomponent ACE for an arbitrary chemical site basis. We then establish an exact analytical mapping between a fitted linear ACE and the average-atom potential that describes a perfectly random alloy. We benchmark potentials built on the occupational, Chebyshev, and conventional ACE bases against solute binding and vacancy formation energies in Mg-Nd, and against the mixing enthalpies of the Mo-Nb and Cr-W solid solutions. When training data are scarce, the occupational basis converges fastest and offers the best control over targeted material properties, while the conventional and Chebyshev bases face challenges in reproducing these properties. The occupational basis likewise yields the most reliable average-atom description of disordered alloy thermodynamics. In the large-data limit the three bases perform identically. The chemical basis is therefore a design choice that governs data efficiency. Its explicit treatment opens a route to average-atom potentials for the thermodynamic, mechanical, and kinetic properties of concentrated alloys.

This study presents multi-epoch photometry from the Wide-field Infrared Survey Explorer to investigate variability in white dwarf debris disks, utilizing the full 14.5 yr mission datasets pre- and post-cryogen. Unambiguous variations are detected across the bulk of the 52 confirmed dusty white dwarfs and are consistent with universal variability after correcting for the sensitivity of WISE relative to Spitzer. Some disk light curves exhibit trends such as possible oscillations, sudden brightening, and steadily decaying fluxes, but all infrared excesses persist utterly. On baselines longer than 0.5 yr, flux changes are significantly skewed toward decreases, in contrast to the symmetric distribution found at shorter baselines with Spitzer, consistent with gradual dust depletion over time. Disk emission generally becomes redder when dimmer and bluer when brighter, consistent with changes in the grain size distribution following collisions, although five disks exhibit the opposite trend possibly due to dust production near apastron. A moderate positive correlation is observed between disk luminosity and photospheric Ca abundance, consistent with the accretion of disk material in an optically thin configuration. Taken together with the Spitzer legacy of dusty white dwarfs, these results provide a comprehensive view of debris disk variability and provide empirical constraints on models of disk structure and evolution.