Papers

Gravitational tail-of-tail corrections arise when radiation scatters twice from the mass-monopole field of its source. In the multipolar effective field theory, one of the two-loop topologies contributing to this process involves genuinely coupled loop momenta, preventing its evaluation through nested one-loop integrations. After tensor reduction, this nonfactorizing structure leads to a particularly challenging family of scalar integrals with unbounded numerator powers as the multipole rank increases. We derive exact closed-form expressions for the entire relevant integer numerator domain, valid in generic dimension and accommodating Feynman, retarded, and advanced prescriptions through consistent analytic continuation. Near $d=3+\epsilon$, we also obtain explicit Laurent expansions through $O(\epsilon)$, retaining the subleading information needed in higher-order radiative calculations. While these expansions determine the dimensional poles, identifying their ultraviolet (UV) or infrared (IR) origin requires a separate analysis of momentum regions. We carry out this analysis throughout the integral domain and apply it directly to the coupled tail-of-tail emission diagram for arbitrary electric and magnetic multipoles. In this way, we independently determine the UV and IR residues, and explicitly verify that the complete infrared pole structure, including both double and simple poles, agrees with the exponentiation of the one-loop gravitational tail. The UV residues, calculated directly from hard-momentum regions, reproduce the established multipole anomalous dimensions when combined with the known contributions of the remaining diagrams.

We constructed a (2+1)-dimensional gravastar whose interior region was characterized by a noncommutative geometry with Gauss-Bonnet corrections, while the exterior region was described by a Gauss-Bonnet-modified BTZ solution. The two geometries were joined across a thin shell using the generalized junction formalism, from which we derived the surface equations of state. We investigated the energy conditions at the shell, determining the parameter regimes under which the null, weak, and strong energy conditions were satisfied. We also analyzed the thermodynamic properties of the noncommutative interior region, including the temperature, entropy, and heat capacity.

We study the long-time, large-distance asymptotics of finite-temperature dynamical Fredholm determinants using effective form factors. The method expresses these asymptotics as a functional of an effective phase shift. We determine its two branches on either side of a quadratic stationary point and the transition profile joining them. The profile is expressed through parabolic-cylinder functions. Its connection to the high-temperature Gaussian $\beta$ ensemble fixes the finite normalization, in agreement with an independent Riemann–Hilbert analysis. We also show that the leading exponential asymptotics suffice to recover the Euler-scale prediction of generalized hydrodynamics for the dynamical structure factor of hard rods.

We investigate dilepton production via virtual quark bremsstrahlung in a hot, magnetized quark-gluon plasma (QGP), extending the Landau-Pomeranchuk-Migdal (LPM) framework to account for a background magnetic field and for Fermi-Dirac quark statistics. An external electromagnetic field drives the quark distribution out of equilibrium, and this off-equilibrium correction, obtained from the Boltzmann equation in the relaxation-time approximation, is in principle explicit in the electric and magnetic field strengths. We argue that this correction, being linear in the electric field, vanishes identically upon integration over the full dilepton solid angle and therefore does not contribute to the dilepton production rate (DPR). The leading magnetic-field signature in the rate instead enters entirely through the equilibrium sector: the medium density and Debye screening mass, computed from the Landau-level structure of the magnetized QGP, modifying the LPM suppression parameter. Working in the regime relevant to the hydrodynamic phase of heavy-ion collisions, we present the LPM-induced DPR for quark scatterers and establish, for the first time, a nonzero magnetic-field imprint on this observable through the LPM mechanism.

Current and upcoming galaxy-redshift surveys offer a promising path for constraining inflationary physics. These constraints are often imposed by relating correlations of the primordial curvature perturbation to the late-time galaxy correlation functions. The primordial correlators can either be computed analytically, or via realizations of the primordial curvature perturbations that are initialized on a grid and evolved numerically according to the classical equations of motion. In this work we take a hybrid approach, initializing the fields in the Bunch-Davies vacuum; and then imposing time evolution through direct numerical integration. Our method efficiently generates realizations of the inverse decay primordial curvature perturbations for axion inflation—an inflationary model in which a pseudoscalar inflaton field couples to a $U(1)$ gauge field via a Chern-Simons interaction. Depending on the choice of parameter $\xi\in\{2, 2.5, 3\}$, which controls gauge field particle production in this model, our method generates realizations with an average runtime of a few hours on 1 CPU core. We compute the power spectrum and bispectrum from these realizations and find a surprisingly large discrepancy between our result and previous work that used an approximation for the gauge field mode functions—up to a factor of $\sim4$ difference for the bispectrum in the case of $\xi=2$. This new method enables not only rapid computation of higher order polyspectra, but also generation of initial conditions for large-scale structure analyses.

We investigate how the long-range tail of dipole-dipole interactions modifies the dynamics of strongly interacting hard-core bosons in a one-dimensional lattice. In the nearest-neighbour model, large interactions generate an emergent Hilbert-space fragmentation into manifolds labelled by the number of nearest-neighbour bonds \(N_{\mathrm{NN}}\). The dipolar tail has a non-monotonic effect on this fragmented dynamics as the interaction-to-tunnelling ratio \(V/t\) is increased. At intermediate \(V/t\), it enhances delocalisation relative to the nearest-neighbour model by reducing the energetic detuning between neighbouring \(N_{\mathrm{NN}}\) manifolds and sustaining their hybridisation by hopping. At larger \(V/t\), the same tail lifts degeneracies within each manifold, beginning with the splitting associated with the next-nearest-neighbour bond number \(N_{\mathrm{NNN}}\), and promotes intra-manifold localisation and Hilbert-space shattering. The competition between these two effects produces a crossover from a delocalising to a localising role of the dipolar tail, visible in the late-time spatial inhomogeneity. This crossover occurs for nearly all initial states considered and persists at different fillings. Transverse confinement strengthens the short-range part of the dipolar tail and shifts the crossover to lower \(V/t\), bringing it into the regime relevant to current experiments with magnetic atoms and polar molecules.

Fewest-switches surface hopping (FSSH) is a popular and versatile approach for performing dynamical simulations beyond the Born-Oppenheimer approximation, in which nonadiabatic effects are incorporated through stochastic hops of the active potential energy surface. However, the FSSH algorithm does not ensure that hops are completely consistent with the underlying electronic wavefunction dynamics. This can lead to significant errors as well as requiring small propagation time steps, which can significantly compromise the computational efficiency of the method. These problems are known to be particularly severe at so-called trivial crossings, for which the nonadiabatic coupling is entirely localized at the crossing point. Here, we solve the trivial-crossing problem by developing a fully-consistent hopping-probability formula, which generates attempted hops that match the time-evolution of the wavefunction across any size time step by construction. A state-tracking algorithm is also utilized to ensure that attempted hops are always accepted at trivial crossings. Through application to systems that contain extremely challenging trivial crossings, we demonstrate that this hopping scheme is capable of obtaining highly accurate results, even when large propagation time steps are used.

Gauge-equivariant graph neural networks generate ordered products of gauge links through local message passing, but the geometry of these internal structures is not captured by the receptive field alone. We investigate the statistical ensemble of closed lattice walks generated by recursive node- and edge-feature operations, independently of network training. Analytical and numerical results reveal a separation between rapid growth of contour length and much slower spatial expansion: deeper compositions generate increasingly long paths through repeated traversal of relatively compact regions. Loop expansions of fermionic observables provide a physical interpretation of this hierarchy, showing how spatial locality remains compatible with high-order dependence on nearby gauge fields. These findings identify complementary roles of network depth in extending spatial reach and enriching the representations constructed within that reach, providing a geometrical perspective on learning lattice gauge observables.

In the present article the self-contained derivation of main formulas of the inverse eigenvalue problem for the Sturm-Liouville operator is given on the base of its discrete approximation and the subsequent transition to the limit of the continuum coordinate. In doing so, we adhere to Tikhonov concept, where the discrete approximation is performed as a regularization of the ill-posed operator problem. While the continuum limit for the three-diagonal matrix Hamiltonian is impossible as such, following the Tikhonov procedure leads not to a limit for the potential matrix itself, but rather for a certain combination of the matrix elements, and this limit is precisely the desired potential in the continuum case.

We study quantum communication, entanglement distribution, and secret-key generation through multimode bosonic loss and fading channels, assisted by local quantum operations and two-way classical communication. Using sector teleportation, we determine the exact two-way quantum and secret-key capacities of multimode pure-loss channels under a mean photon-number constraint, allowing arbitrary adaptive quantum protocols. We extend these results to continuous frequency-dependent loss under a power constraint and identify the optimal allocation of photons among optical modes. For constant loss over an unlimited bandwidth, we obtain a closed-form capacity proportional to the square root of power. For randomly varying loss, we determine exact finite-energy capacities when the channel realization is publicly revealed, distinguishing knowledge before and after transmission. When fading remains unobserved, we derive capacity bounds and explicit formulas for an on/off channel. We also establish strong-converse bounds, with exact thresholds for the deterministic loss models considered here, observed fading, and unobserved fading with finitely many possible transmissivities. Under mean energy constraints, these thresholds generally exceed the corresponding finite-energy capacities. These results guide energy allocation and provide benchmarks for energy-constrained optical quantum communication with multimode signals and variable loss.

Wilms tumor (WT) is a heterogeneous pediatric renal malignancy. Invasive procedures to establish histology prior to pre operative treatment are not recommended by the International Society of Pediatric (SIOP) Oncology Renal Tumor Study Group, yet different tissue components are associated with different responses to therapy (SIOP Umbrella protocol). Intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) may improve subtype differentiation before surgery as a noninvasive radiographic biomarker by capturing both diffusion and perfusion characteristics, as opposed to the conventionally used apparent diffusion coefficient (ADC). The objective of this study is to evaluate the discriminative performance of IVIM MRI in differentiating WT subtypes. IVIM provides quantitative parameters that disentangle the diffusion coefficient (D), incoherent blood flow (pseudodiffusion Dstar) and perfusion fraction (f). This retrospective study included thirthy children with WT. Standardized 1.5T MRI with 10 b value diffusion weighted imaging (DWI) was performed. IVIM parameters were estimated using a selfsupervised implicit neural representations network and were correlated with histopathology via a patient specific 3D printed cutting guide. Statistical analyses included mixed models, receiver operating curve analysis, and logistic regression. Thirty lesions were MRI histopathology correlated on slice level. Significant subtype differences were observed for Dstar stromal versus epithelial (p = 0.024), regressive tumors (p = 0.031) and mixed WT tumors (p = 0.043). ADC showed no significant subtype differences. Direct MRI histopathology correlation enabled differentiation between stromal subtype and epithelial, mixed and regressive subtype on macroscopic slice level using Dstar.

The valence-bond-glass state of the 4d^1 double perovskite Ba2YMoO6 combines Mo^5+ singlets with residual paramagnetic "orphan" spins whose coupling is hard to reach with bulk probes. We probe them by electron paramagnetic resonance of a dilute Gd^3+ ion on the Y^3+ site via broadband coplanar-waveguide transmission at 5 K. The isostructural nonmagnetic niobate Ba2YNbO6, doped with the same Gd^3+ probe, is a fixed-lattice control. The Gd^3+ linewidth nearly doubles in the magnetic host. Dipolar coupling to the sparse orphans is nearly an order of magnitude too weak; the excess is instead reproduced by a transferred f-d superexchange of J ~ 0.2 K, so the width is a static measure of orphan-spin coupling. The half-field (Delta m_S = +/-2) satellite collapses in the magnetic host, a dynamical dephasing channel, while the unchanged g-factor marks a zero-mean random internal field. Together the two channels probe the coupling and dynamics of valence-bond-glass orphan spins.

We study the imaginary part of the holographic timelike entanglement entropy (HTEE) in a charged asymptotically AdS$_5$ black-hole background whose dual field theory exhibits a critical point in the presence of a chemical potential $\mu$ and temperature $T$. Identifying the imaginary part of the HTEE with the imaginary part of the pseudoentropy, we derive an analytical expression for this quantity and investigate its behavior on the stable and unstable thermodynamic branches. We find that the imaginary HTEE vanishes in the uncharged limit and is induced entirely by a nonzero chemical potential, signaling the emergence of quantum coherence between the initial and final states. As the dimensionless ratio $\mu/T$ approaches its critical value, we obtain an inverse-square-root divergence in the derivative of the imaginary HTEE and extract the critical exponent $\theta_I = 1/2$ analytically. We further show that the same exponent governs the temperature response at fixed chemical potential. Our results establish the imaginary part of the HTEE as a non-local quantum-information probe of criticality in strongly coupled systems, and they imply that the initial and final states become maximally coherent at the critical point.

We quantize, in the homogeneous temporal gauge, both the electric and the magnetic Carrollian Yang-Mills theories with SU(N) gauge symmetry in the fundamental representation. We use the BRST method implemented in the path integral. We show that in the first case all the interaction vertices vanish, thus, giving a free theory. In the magnetic case, there are no loop contributions to the Green functions of the elementary fields –i.e., Green functions not involving composite operators– and the only connected parts of such Green functions with a dependence on the coupling constant are the tree level contributions to the three and four point functions of the field $\xi_i$. We also show that in the magnetic case the Green functions involving only Wilson loops are trivial and not so in the electric case.

We introduce PULSUS, a direct frequency-domain framework for multidimensional spectroscopy of open quantum systems beyond the impulsive rotating-wave approximation. Coherence-frequency intervals are represented through Liouvillian resolvents, while finite Gaussian pulses are incorporated through operator-valued functions of the field-free Liouvillian. This enables direct evaluation on Cartesian grids or arbitrary spectral coordinates while retaining molecular evolution during the pulse envelopes and, when required, the complete light–matter interaction. The implementation is validated against analytical and independent time-domain benchmarks and supports targeted spectral sampling that reduces the number of evaluated coordinates when the response is spectrally localized. A controlled hierarchy of finite-pulse, rotating-wave, short-pulse, and impulsive models separates the errors introduced by each approximation. For a coupled electronic dimer, the total impulsive-RWA error is nonmonotonic in pulse duration: an intermediate regime provides the highest accuracy, whereas ultrashort pulses expose coupling-enabled beyond-RWA pathways and longer pulses develop substantial finite-pulse corrections. These results show that the impulsive and rotating-wave approximations cannot be assumed to improve simultaneously and should be tested when quantitatively interpreting multidimensional spectra. PULSUS provides a direct frequency-domain framework for carrying out that comparison.

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has published its second catalog of 3,641 fast radio bursts (FRBs). While this sample includes 981 bursts from 83 repeating sources, only 2.3% of CHIME FRBs are observed to repeat. This raises the question of whether the FRB population truly consists of a single repeating population or includes a distinct subpopulation of one-off sources. We apply Simulation Based Inference (SBI), a likelihood-free machine learning framework, to model the CHIME/FRB Catalog 2 dataset, testing eight FRB population models, half of which include a subpopulation of truly one-off sources. The current catalog strongly and decisively favors models including such a subpopulation, with the best-fitting model combining a log-normal burst rate distribution, a Poissonian wait-time distribution, and a one-off subpopulation. This preference is corroborated by an independent random forest classifier and by the ability of one-off models to naturally reproduce the hyperactive repeating sources present in the catalog without having been trained on them. We place upper limits on the potentially observable CHIME/FRB population of 36,000 repeating sources and 19 one-off sources per day in the CHIME sky. Models with a one-off subpopulation naturally account for the hyperactive repeating sources present in the catalog without having been trained on them, providing an independent consistency check on our results. We predict the repeater percentage will fall below 2% in the next five years, eventually declining to ~0.5% as the sample saturates with one-off detections.

We investigate parity violation searches with the 4-Point Correlation Function (4PCF) using the Quijote and Quijote-Odd halo catalogs. Specifically, we explore the auto- and cross-correlation searching methodologies that have been previously used in the Baryon Oscillation Spectroscopic Survey (BOSS) and the Dark Energy Spectroscopic Instrument (DESI) searches. Although the Quijote-Odd simulations are initialized with a parity-violating primordial trispectrum, we find no statistically detectable parity-odd signal in the halo 4PCF. Instead, we find that the halo measurements are dominated by Poisson noise. We are able to distinguish this noise-dominated behavior from the response expected for a parity-odd signal. These results clarify how parity-sensitive 4PCF statistics respond to noise in a controlled simulation setting.

We study the potential of very high-energy lepton colliders to probe effective operators affecting the loop-induced Higgs boson decays $h\to \gamma\gamma$ and $h\to Z\gamma$, providing constraints complementary to Higgs coupling measurements at the Large Hadron Collider. In particular, we consider processes with two and three bosons in the final state and analyze their individual and combined impact on the effective field theory parameter space. We demonstrate that these processes at a multi-TeV lepton collider can improve the bounds from rare Higgs decays and electroweak precision observables, surpassing the projections for High-Luminosity LHC and FCC-ee. This is especially true for triboson processes, whose sensitivity is enhanced by the growth with energy of the new physics cross-sections, making them the dominant constraint at very high energies, potentially competitive with FCC-hh.

Accurate forecasting of optical turbulence (OT) is useful to optimise telescope scheduling and maximising observing efficiency, as the performance of adaptive optics systems strongly depends on turbulence conditions. While various numerical weather prediction and machine learning models are developed to predict these complex turbulence properties, properly evaluating their added value requires well-defined baseline reference models. This study establishes baseline performance thresholds for key astroclimatic parameters using two distinct models: one forecasting the parameter average over a specific timescale, and the other forecasting the temporal evolution over the same specific timescale. We apply these frameworks to extensive, multi-year datasets from the sites of the Very Large Telescope (VLT) and the Large Binocular Telescope (LBT) and discuss the possibility of extrapolating reference values of forecast performances for other sites based on their optical turbulence statistical characteristics. Our results show that baseline predictive accuracy varies according to the observing site, the specific parameter, the chosen timescale, and the forecasting approach. Therefore, an OT forecasting model's accuracy cannot be quantified in absolute terms, but relatively to the baseline.

Topological photonics has recently attracted a significant attention, leading to many theoretical studies and predictions. However, direct experimental demonstrations of topology-driven effects, particularly in nanostructures, are rarely proven. In this work, we experimentally investigate multilayer photonic nanostructures composed of alternating subwavelength dielectric layers, arranged according to the topological Su-Schrieffer-Heeger model. By engineering different edge truncations, we probe different supported topological phases. Our theoretical predictions and experimental measurements reveal strong field confinement at the surface exclusively in the configuration supporting topological edge states, providing their localized character and topological origin. First, we demonstrate enhanced absorption in an ultrathin absorbing overlayer deposited on the surface when the topological surface mode is present, highlighting the potential for surface-sensing applications. Second, we observe enhanced second-harmonic generation in reflection from the surface, demonstrating the potential of topological states for surface enhanced nonlinear optics enabled by the strong localization of the electromagnetic field at the interface.

X-ray binaries are excellent laboratories to study the coupling between accretion and ejection phenomena around compact objects through multiwavelength observations. Swift J1753.5-0127 is a black hole low-mass X-ray binary discovered in outburst in 2005 that remained active for 11 years, followed by two mini-outbursts. We investigate the behavior of the compact jets of Swift J1753.5-0127 during its 2023-2024 outburst. We report a dense multiwavelength monitoring in the radio, NIR/optical/UV and X-ray bands. Using new and archival luminosity measurements, we construct a refined, smoother radio/X-ray plane that covers the steep/outlier and shallow/transition branches of the radio/X-ray correlation. We also present spectral energy distributions (SEDs) constructed using quasi-simultaneous observations from four epochs. Swift J1753.5-0127 underwent a faint, hard-only, double-peaked outburst, followed by a re-brightening in the optical. The updated radio/X-ray plane offers a clear view on the region occupied by this source, similar to MAXI J1348-630, but at lower radio luminosities than H 1743-322, and we confirm its hybrid behavior. The broad-band SED fitting reveals that a cool, truncated accretion disk dominates the NIR/optical/UV band. We find that the compact jets have a variable but weak contribution in the NIR, with a break frequency $\nu_\mathrm{break} \lesssim 5 \times 10^{12}~\mathrm{Hz}$, providing additional evidence that radio-quiet sources are also infrared-quiet. We also find evidence that the radio spectral index evolves with X-ray luminosity, transitioning from inverted values near quiescence to flatter or negative values at higher luminosities. In the context of adiabatic jet models, this trend may indicate that the jet geometry becomes increasingly confined as the accretion rate rises.

This paper presents two methods for probing the proton structure and the number of partonic interactions in proton-proton collisions using dimuon production and minimum bias events. At the LHC these targeted measurements can provide information on the average number of partonic scatters in different event classes, their dependence on the partonic momentum fraction, x, and potentially partonic flavour. Within a simple mostly geometric model of multiparton interactions as quasi-independent scatters, the measurements can be used to make inference about the proton-proton overlap dependence on impact parameter and its partonic-x dependence.

Explicitly correlated methods, which represent dominant short-range correlations by a diagonal Jastrow-type correlator, are designed to accurately describe systems of strongly correlated electrons, such as the fully periodic 2D Fermi–Hubbard model. However, as the reference state is compact in momentum space whereas the correlator acts naturally in real space, there is a fundamental mismatch of bases that classical algorithms resolve only by restricting the reference or the correlator. Here we propose a hybrid algorithm in which a quantum processor prepares a low-entanglement momentum-space matrix product state (MPS), precomputed classically by the transcorrelated method at the cost of a nonvariational energy, rotates it to real space, and measures in bases fixed by the Hamiltonian. Because the measurement bases are independent of the correlator, the correlator can be variationally optimized entirely in classical post-processing with no quantum-classical feedback loop. We demonstrate our algorithm on 32 qubits of Quantinuum's H2-2 with a bond-dimension-4 MPS for the half-filled $4 \times 4$ lattice and achieve a relative ground-state energy error of $16 \pm 4\%$ after postselection, reduced to $3.5 \pm 0.5\%$ by calibration using low-order moments from the MPS. Compared with other feedback-free hybrid algorithms, even under generous assumptions, our method requires fewer samples than quantum-selected configuration interaction and fewer two-qubit gates than quantum Krylov methods.

High-energy neutrinos from Seyfert galaxies probe particle acceleration near supermassive black holes, but the accelerated nuclear composition remains uncertain. We connect stochastic acceleration to nuclear and radiative cascades to assess nuclear contributions. Acceleration and losses limit the energy per nucleon available to nuclear cascades; without secondary reacceleration, fragmentation cannot raise this scale. For NGC~1068, joint neutrino and gamma-ray constraints depend on the nuclear mixture: helium-dominated injection permits larger nuclear power fractions than the heavier mixtures considered. For the harder candidate {neutrino} spectrum of NGC~7469, the adopted model yields more energetic nuclear cascades, while the source-specific flux selections allow larger nuclear fractions for the heavier mixtures than in NGC~1068. These results show that composition constraints depend on nuclear yields as well as acceleration conditions and available power.

Double perovskites (DPs) offer a compositionally versatile platform for photocatalysis and optoelectronics, but their soft lattices favor strong exciton-phonon coupling and self-trapped excitons (STEs), which produce broad, red-shifted photoluminescence (PL). Here, we combine optical spectroscopy and ab initio calculations to study lead-free, Sb-doped Cs2BInCl6 nanocrystals with B-site alloying from Na to K. Alloying tunes the PL energy from about 2.48 to 2.70 eV, while absorption features near 3.8 eV remain nearly unchanged. Calculations reveal that Sb doping enables bright radiative recombination channels and delocalizes the excitonic wavefunction. We identify STEs responsible for the large PL red shift, associated with an upward shift of dopant-hybridized in-gap states. Na-to-K substitution selectively changes the STE lattice distortion, explaining why PL varies strongly with composition while absorption does not. Theory further predicts pronounced PL polarization anisotropy that reflects the STE wavefunction's spatial structure and depends on B-site composition. Time-resolved anisotropy measurements closely agree with these predictions, providing experimental fingerprints of the excitonic wavefunction and its evolution with alloying. Together, these results disentangle the roles of doping and alloying in lead-free DPs and establish polarization-resolved spectroscopy as a probe of STE wavefunctions.

A possible mechanism of tornado generation is associated with the Schwarzschild criterion for convective instability. The supercooled cloud-air mixture near the axis starts to descend and, due to the super adiabatic temperature gradient, the overheated near-surface air mass rises. The complete system of equations for full model includes equations for the stream function, for the azimuthal velocity component, and for the change in density. The refined model considers rotating convection within the framework of ideal hydrodynamics. The simplest model uses a separate equation for the stream function and can be applied to the initial stage of vortex generation. Within the framework of the simplest model, an analytical solution is combined from 8 linear dependencies by height. Rotation increases due to the conservation of angular momentum. Within the framework of the refined model, some unidirectional differential rotation arises, but it depends on boundary conditions (can be local). The full model studies the tornado development as rotating convection from the very beginning to the quasi-stationary stage. Velocity components increase in a coordinated manner. Two cases are considered: a single whirlwind and a two-eyed tornado. Radial flows converge towards the central part of the tornado near the earth surface, and there is an outflow from the "wall" to the axis and to the periphery near the top of the tornado. The maximum vertical velocity component is achieved at a certain radial distance at a certain height. The maximum azimuthal velocity component is achieved in the tornado "wall". Tornado generation criteria are discussed.

We propose a protocol to prepare and probe dark states in a single-molecule electron spin resonance based on atomic force microscopy (ESR-AFM), thus extending existing techniques developed to address Rabi oscillations. To this end, we simulate in analogy to atomic physics the coherent manipulation of a three-level system in the V-configuration using a multifrequency magnetic field. More specifically, we consider a neutral molecule with a zero-field-split (ZFS) first excited triplet and analyze within a pump-probe scheme the dynamics of the total triplet population. In the triplet subspace, the dark state is a coherent superposition formed by two ZFS states which does not evolve in time despite a continuous resonant driving towards the third one. We characterize the properties of this state comparing it to its fully incoherent counterpart. Within a density-matrix formalism for open systems, we then compute the expected dark state signatures both for ideal scenarios and for the realistic parameterization of ESR-AFM on pentacene.

Massive black holes (MBHs) grow through both gas accretion and mergers and it remains unclear how variations to MBH growth and dynamical histories contribute to the spread in empirical scaling relations between MBHs and their host galaxies. We examine the ex- and in-situ growth of MBHs within large-scale cosmological simulations and compare the evolution of an outlier population of under-grown MBHs to the general population. We use the Romulus25 uniform volume cosmological simulation and the RomulusC cluster zoom-in simulation to examine the growth and merger histories of MBHs. We identify central MBHs that are undergrown relative to other MBHs in similar mass galaxies and investigate their accretion, merger, and orbital histories within the simulations. The contribution of ex-situ growth increases with MBH mass, with mergers becoming increasingly important in the most massive galaxies. We find no difference between cluster and field environments in terms of the importance of ex-situ growth, which is generally very low. Under-grown MBHs have experienced fewer mergers and have had complex dynamical histories, spending significant time 'drifting' within the galaxy or 'competing' with another MBH. Other under-grown MBHs have experienced a 'late entrance' into a galaxy which until then had no central MBH. Our results demonstrate that MBH assembly is dominated by in-situ growth, which in turn is impacted by the dynamical histories of MBHs within assembling galaxies. Prolonged off-centre evolution can suppress accretion and contribute to the formation of under-grown central MBHs at $z=0$.

Rare events, such as crystal nucleation in mildly supercooled liquids, are characterized by waiting times that can be much longer than the timescale of the underlying microscopic dynamics. The mean first-passage time (MFPT) formalism [J. Wedekind and D. Reguera, J. Phys. Chem. B 112, 11060 (2008)] provides a route to reconstruct one-dimensional free-energy profiles from the MFPT and steady-state distribution measured along a reaction coordinate, but conventional implementations become inefficient for sufficiently high barriers because spontaneous crossings are rarely observed. We introduce a "top-start" extension that initiates trajectories near the barrier top and reconstructs the free-energy profile from their subsequent evolution away from the barrier toward lower-free-energy regions. We establish the equivalence between the top-start and two-region constructions using a Markov-chain transition-matrix formulation. We validate the method using one-dimensional random-walk simulations across low, medium, and high free-energy barriers, with transition-matrix calculations providing an exact benchmark for the corresponding discretized models. The top-start reconstruction remains accurate in the high-barrier regime where conventional MFPT sampling becomes prohibitively inefficient.

Chemical language models (CLMs) are pretrained on large corpora of molecules with the aim of learning representations that transfer to diverse downstream tasks. Here, we systematically study the effects of pretraining using a series of such CLMs across 64 molecular property prediction datasets. We find that the downstream gains of pretraining in CLMs do not scale and performance saturates below gradient-boosting baselines. Across the regimes evaluated, only supervised pretraining on traditional physico-chemical descriptors consistently improves downstream performance for the CLMs tested whereas some forms of pretraining result in models worse than a randomly initialized encoder. While models can resolve molecular structure well, they do so no better than a randomly initialized model, suggesting that, at best, CLMs learn descriptor-like properties in addition to low-level token statistics during pretraining, but surprisingly little chemistry beyond what classical molecular features already capture.