Atomic Physics
A single atom emitting resonance fluorescence into a coherent beam, and its use for non-destructive atom thermometry
Tomáš Lamich, Laura Zarraoa, Sondos Elsehimy et al. (+2 more)
Using a far-off-resonance optical dipole trap, we place a single neutral $^{87}$Rb atom in a weak, atom-resonant coherent beam, while also strongly illuminating it from an orthogonal direction to produce resonance fluorescence. The atom-modified coherent beam is then collected and its
photon statistics analyzed. We observe first-order interference that can increase or decrease the beam flux, depending on the relative phase of the coherent beam and resonance fluorescence. This confirms predictions of Goncalves et al. [Phys. Rev. A 104, 013724]. The interference visibility is also shown to be a sensitive, time-resolved, non-destructive thermometer: by fitting the resulting
photon count distributions, we infer the center-of-mass localization of the atom within the trap. With $1200$ atoms and integration time of $80\mathrm{ms}$ per atom, we demonstrate temperature uncertainties of $4 %$ for $\sim 30 \mu\mathrm{K}$ temperatures at $\sim 200\mu\mathrm{s}$ time resolution.
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All authors Tomáš Lamich, Laura Zarraoa, Sondos Elsehimy, Morgan W. Mitchell, Romain Veyron
Astrophysics of Galaxies
The TOP-SCOPE Survey of Planck Galactic Cold Clumps: Molecular gas properties
Yuebin Yang, Jarken Esimbek, Tie Liu et al. (+11 more)
We surveyed 2008 Planck
Galactic Cold Clumps (PGCCs) in $^{12}\mathrm{CO}$ and $^{13}\mathrm{CO}$ $J=1$–0 lines using the Taeduk
Radio Astronomy Observatory (TRAO) 14 m
telescope's multi-beam receiver. We detected 2784 ($^{12}\mathrm{CO}$) and 2291 ($^{13}\mathrm{CO}$) velocity components, their closely correlated centroid velocities suggest that $^{12}$CO and $^{13}$CO generally trace kinematically associated gas. PGCCs have low excitation temperatures (mean $\sim$10 K), mean $^{13}\mathrm{CO}$ optical depth $\sim$0.5, and mean $^{13}\mathrm{CO}$-derived H$_2$ column density $4.3\times10^{21}$~cm$^{-2}$. Gas–
dust correlations are moderate, with $N_{^{13}\mathrm{CO}}$ more tightly correlated with the
dust-derived H$_2$ column density from the PGCC catalog than $I_{^{12}\mathrm{CO}}$. Colder PGCCs tend to have higher CO-to-H$_2$ conversion factor ($X_{\mathrm{CO}}$) and $[\mathrm{H_{2}}]/[^{13}\mathrm{CO}]$ ratio. $X_{\mathrm{CO}}$ increases clearly with the
dust-derived H$_2$ column density, consistent with enhanced CO freeze-out in high-column-density gas. Supersonic non-thermal motions are widespread: the Mach number derived from $^{13}\mathrm{CO}$ has a mean of 4.3 and a median of 3.6, increasing slightly with
dust-derived H$_2$ column density. Overall, PGCCs are cold but dynamically active, serving as a valuable laboratory for studying the initial conditions of
star formation.
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All authors Yuebin Yang, Jarken Esimbek, Tie Liu, Willem Baan, Xunchuan Liu, Kee-Tae Kim, Gang Wu, Xindi Tang, Jianjun Zhou, Dalei Li, Yuxin He, Sung-ju Kang, Yingxiu Ma, Dongdong Zhou
Materials Science
Ordered-to-disordered transfer learning with graph neural networks for formation-energy and HOMO-LUMO gap prediction in high-entropy perovskite oxides
Panupol Untarabut, Narjes Jomaa, Sylvian Cadars et al. (+4 more)
High-
entropy perovskite
oxides (HEPOs) represent a chemically complex class of materials with promising functional properties, yet their vast compositional space and, chemical/structural disorder pose significant challenge for accurate property prediction. Graph neural networks (GNNs) enable rapid exploration of materials space but are often limited by the availability of representative training data. Here, we investigate ordered-to-disordered transfer learning using GNNs for formation-energy and HOMO-LUMO gap prediction in HEPOs by transferring knowledge learned from chemically ordered perovskites. Four representative GNN models, including CGCNN, GATGNN, ALIGNN and M3GNet are evaluated to understand the role of structural representations, spanning pairwise two-body and angular three-body interactions in transfer performance. We find strong property-dependent transfer behavior: formation-energy prediction transfers effectively to disordered HEPOs, whereas HOMO-LUMO gap prediction shows limited transferability due to its sensitivity to local chemical environments. Incorporating a small HEPO-specific training
dataset substantially improves HOMO-LUMO gap prediction. Representation-level analysis using UMAP further highlights the importance of encoding three-body
geometric information such as in ALIGNN for capturing complex structure-property relationships and improving transferability.
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All authors Panupol Untarabut, Narjes Jomaa, Sylvian Cadars, Olivier Masson, Samuel Bernard, Assil Bouzid, Santanu Saha
High Energy Physics (Phenomenology)
The fundamental limit of jet tagging: Beyond top jets
Sarah Koller and Humberto Reyes-González
Jet tagging, i.e. determining the origin of high-energy hadronic jets, is a key challenge in particle physics. Machine-learning-based taggers have achieved remarkable progress, raising the question of how close current methods are to the theoretical limit of performance. Previous work addressed this question for boosted top-
quark jets using
transformer-based generative models that provide realistic synthetic jet data with known probability density functions. This enables a direct comparison between modern taggers and the optimal likelihood-ratio classifier. In this note, we summarize the approach and extend the study to boosted W, Z, and H$\rightarrow gg$ jets. We find that the gap to the estimated optimal limit is strongly jet dependent and is substantially reduced for these seemingly more challenging tagging tasks. Ongoing work aimed at understanding the interpretation, robustness, and scaling of these limits is also briefly discussed.
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Optics
High-NA vectorial hologram optimization
Michael Wischert, Fiona Hellstern, Paul Uerlings et al. (+3 more)
We present a vectorial phase-only framework for the gradient-based optimization of computer-generated holograms. Our approach addresses a critical limitation in high numerical aperture (NA) optical systems, where standard scalar approximations often experience significant fidelity degradation. We highlight the limitations of scalar diffraction models (Fraunhofer and Debye) at high NA for representative classes of target intensities, namely tweezer arrays and extended flat-top profiles. Using a differentiable Richards-Wolf forward model, we numerically demonstrate stable algorithmic convergence and the generation of highly uniform intensity profiles in the deep non-paraxial regime. At NA=0.9, Richards-Wolf (RW) optimization reaches flat-top and tweezer uniformities of 99.97 % and 99.98 %, respectively, with a mean tweezer ellipticity of $\varepsilon=$1.007, while scalar forward models show target-dependent degradation in plateau fidelity or focal geometry. Furthermore, because the RW model returns the full vectorial field, the same framework can optimize objectives that depend on local polarization. We demonstrate this for a polarization-sensitive optical-dipole-potential target, where direct RW-potential optimization reduces the mean normalized residual by more than an order of magnitude when including vector and tensor light-shift terms.
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All authors Michael Wischert, Fiona Hellstern, Paul Uerlings, Tilman Pfau, Stephan Welte, Ralf Klemt
Optics
Causality-Aware Interaction Selection for Retarded Green-Function Assembly
Sushil Kumar, Wolf van der Hert, Giampiero Gerini et al. (+1 more)
In time-domain integral-equation (TDIE) solvers, the assembly of the retarded Green-function interactions remains a major computational bottleneck. We present a causality-aware assembly strategy that exploits the finite space–time support of the retarded Green function to identify admissible interactions prior to numerical evaluation. By using causality as an exact interaction-selection criterion, causally inadmissible interactions are excluded a priori, reducing assembly complexity without modifying the underlying TDIE formulation or introducing approximations. Numerical validation confirms that the proposed
pruning preserves the TDIE transient response. The remaining admissible interactions are organized into vectorized shared-
memory workloads for efficient assembly. The results demonstrate a 41 % reduction in evaluated interactions, a 2.6 times single-worker algorithmic speedup, and a total assembly-time speedup of up to 109 times using 64 CPU workers.
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All authors Sushil Kumar, Wolf van der Hert, Giampiero Gerini, M. C. van Beurden
Mesoscale and Nanoscale Physics
Delayed Formation of Landau Polaritons in Phase-Resolved THz Spectroscopy
Noureddine Charrouj, Yurii Ivonyak, Dmitriy Yavorskiy et al. (+4 more)
Strong light-matter coupling gives rise to polaritons through coherent and periodic energy exchange between electromagnetic cavity fields and material excitations. While this interaction is typically inferred from spectral mode splitting, its dynamics remain largely unexplored. Here, using phase-resolved terahertz time-domain spectroscopy, we observe Rabi oscillations of Landau polaritons formed by coupling the cyclotron resonance in a GaAs/Al$_{0.36}$Ga$_{0.64}$As two-dimensional electron gas with Fabry-Perot cavity modes. By employing cross-polarized spectroscopy and
magnetic-field differential, we resolve the temporal beating of the cyclotron resonance oscillations. Remarkably, we find that the Rabi oscillations do not start immediately after excitation of the cyclotron resonance, but after a delay corresponding to one cavity round-trip time. This demonstrates that the strong-coupling regime sets up only after the formation of the cavity mode field. Our results provide direct insight into the dynamics of hybrid light-matter states in the THz regime.
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All authors Noureddine Charrouj, Yurii Ivonyak, Dmitriy Yavorskiy, Vladimir Y. Umansky, Jerzy Lusakowski, Wojciech Knap, Marcin Bialek
Astrophysics of Galaxies
ROLLIN': Rotating globular cluster simulations II. The complex morphology of globular clusters driven by multi-scale dynamics
Arn Marklund, Paolo Bianchini, Anna Lisa Varri et al. (+2 more)
Globular clusters (GCs) are inherently non-spherical systems that in many cases show internal rotation. Typically, rotation is considered the main driver of GC morphology; however, the relationship between ellipticity and rotational support is not a simple one-to-one mapping, and other multi-scale dynamical processes may contribute. We investigate how morphology evolves in realistic models of rotating GCs, and how it correlates with key physical ingredients, including mass loss,
stellar evolution, external
tidal fields, and two-body relaxation. Using the ROLLIN' suite of direct N-body simulations, we measure the intrinsic ellipticity and triaxiality of our models using the second-moment tensor method, and explore their
evolution and the physical mechanisms driving them. We find that early GC
evolution can be dominated by dynamical instabilities driven by internal rotation and velocity anisotropy, leading to bar-like structures that rapidly erode due to collisional effects around the time of the first core collapse. These bars are stronger and longer-lived ($\lesssim 800,\mathrm{Myr}$) in strongly rotating clusters with longer relaxation times and subject to
stellar evolution. In the long term, clusters evolve toward less flattened and gradually triaxial configurations, particularly when they experience stronger mass loss, are more tidally filling and isotropic, and have lower rotational support. Our models provide a physical explanation for the observational $V/\sigma$–ellipticity relation and demonstrate that morphology can serve as a reliable tracer of the dynamical state of GCs. Initially retrograde, dense, and inclined rotating models deviate from this relation, providing a physical explanation for observational outliers. This framework will aid the interpretation of GC
evolution in upcoming large-scale photometric surveys.
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All authors Arn Marklund, Paolo Bianchini, Anna Lisa Varri, Katarina Kraljic, Giulia Pagnini
History and Philosophy of Physics
Erwin Schroedinger: His Poetry and Fragment of a Galilean Dialogue
Helge Kragh
While Erwin Schroedinger's contributions to
quantum mechanics and other areas of theoretical physics are very well known, his works as a poet and literary writer are usually ignored. In this paper I reconsider his poetry and refer to a few poems written about him. A short fragment of a Galileo-inspired dialogue that Schroedinger published in 1955 is as interesting as it is puzzling and little known. The dialogue is essentially about atomic theory as known much earlier, namely in the early 1910s. Indeed, there is the slight possibility that Schroedinger may originally have conceived it at that time and even composed a version of it. Apart from considering the origin and reception of the manuscript, I analyze its content from the point of view of the history of physics.
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High Energy Physics (Phenomenology)
The price for monopole dark matter
Felix Brümmer, Giacomo Ferrante, Théodore Fischer et al. (+1 more)
We construct an explicit model where dark matter consists of 't Hooft-Polyakov monopoles. The dark sector is in thermal contact with the Standard Model, and dark monopoles are created by a thermal phase transition in the early Universe. Generically, the abundance of monopoles is negligible with respect to that of stable dark elementary particles. We show how to avoid this by taking the lightest stable particle, a dark
fermion, sufficiently light for its abundance to be suppressed, yet heavy enough to satisfy constraints on dark radiation. In this specific window of parameters, dark matter is composed of monopoles with a mass of about $10^8$ GeV or larger, depending on the nature of the phase transition. This candidate lies beyond the reach of present, conventional dark-matter detection experiments. However, the model necessarily predicts dark radiation, with $\Delta N_{\rm eff}$ close to present-day bounds. In addition, if the dark phase transition is strongly first order, we find that the corresponding gravitational wave spectrum lies close to the region probed by future interferometers.
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All authors Felix Brümmer, Giacomo Ferrante, Théodore Fischer, Michele Frigerio
Solar and Stellar Astrophysics
Spectroscopic Analysis of the 2025 Eclipse of the Symbiotic Binary V1413 Aquilae
David Boyd, James Foster, Forrest Sims et al. (+12 more)
We report on a coordinated campaign by amateur astronomers using a combination of high and low resolution spectroscopy to observe the 2025 eclipse of the symbiotic binary V1413 Aql shortly after a probable Z And-type symbiotic outburst. We measured the eclipse time of minimum and computed an updated eclipse ephemeris. Our spectra were calibrated in absolute flux and multi-Gaussian fits were used to resolve and quantify components of the H{\alpha} emission line. We measured the radial velocity curve of the white
dwarf and determined the semi-amplitude as 25.7 km/s and the systemic radial velocity as 95.1 km/s. We found the spectral continuum was consistent with that of a late F or early G type
giant star.
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All authors David Boyd, James Foster, Forrest Sims, David Cejudo, Robin Leadbeater, Pavol Dubovsky, Xavier Dupont, Keith Shank, David Trowbridge, Jerry Hinnefeld, Colin Eldridge, Joan Guarro Flo, Kevin Gurney, Gary Walker, Josch Hambsch
High Energy Astrophysical Phenomena
Gamma-ray emission from particle illumination and shock-cloud interaction in the W51 Complex
Alan Sunny and Martina Cardillo
In the current era of very-high-energy (VHE) and ultra-high-energy (UHE) $\gamma$-ray astronomy, understanding
Galactic PeVatrons and their acceleration mechanisms remains a primary objective. Recent LHAASO observations of the W51 Complex make it an ideal laboratory for investigating the origin of UHE emission, particularly due to the presence of massive and dense molecular environment surrounding multiple potential particle accelerators. In this work, we study two hadronic scenarios for the W51 Complex. First, we model the direct interaction between the SNR W51C and the nearby clouds in W51B, incorporating fresh particle acceleration, shock-driven adiabatic compression, and reacceleration of permeating
Galactic cosmic rays. Second, we explore an accelerator-independent illumination scenario in which the W51B cloud acts as a long-term confinement region for high-energy particles injected during an earlier epoch. We find that the direct shock-cloud interaction scenario successfully reproduces the GeV emission observed by
Fermi-LAT, but fails to account for the UHE emission detected by LHAASO. In contrast, the illumination scenario naturally explains the UHE spectrum, indicating that dense molecular clouds can efficiently confine and sustain energetic hadronic populations over long timescales. Although the inferred injection history is compatible with a young SNR origin, the source-independent nature of the illumination framework also permits other accelerators within the W51 Complex. Our results therefore identify dense molecular environments as the key structures sustaining historical PeVatron activity and shaping the observed UHE $\gamma$-ray emission.
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Other Condensed Matter
Valley- and Orbital-Controlled 2D Chern Insulators Without Spin-orbit Interaction
J. Benkaida, O. Benhaida, L. B. Drissi et al. (+1 more)
We present a theoretical study of orbital-induced topological phase transitions in a two-dimensional
lattice model with staggered potential $(\Delta)$ and orbital coupling $(\lambda)$ competing with the hopping strength. By tuning these parameters, two gap-closing mechanisms emerge: valley closure at $\mathbf{K}$ and $\mathbf{K'}$ for $\lambda=\pm\Delta$, and a $\mathbf{\Gamma}$-point closure at $\lambda=\pm\sqrt{\Delta^2+9t_0^{2}}$. Their interplay defines a topological window in which the Berry
curvature localizes near a single valley, yielding a quantized anomalous
Hall conductivity ($\sigma_{xy}=e^{2}/h$) and Chern number ($C=1$). These results demonstrate orbital-driven Chern insulating behavior without
spin-orbit coupling. The resulting phase diagram captures the transition from trivial to topological phases and suggests practical routes for orbital engineering in tunable
lattice systems.
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All authors J. Benkaida, O. Benhaida, L. B. Drissi, E. H. Saidi
Mathematical Physics
On the Emergence of Exponential Decay from Discrete Spectra for Friedrichs Hamiltonians
Tamim Al-Qaiwani and Sören Petrat
We study a class of Friedrichs
Hamiltonians, that is, operators describing an excited state coupled to a bath through a rank-one perturbation, in the case where the bath
Hamiltonian has purely discrete spectrum. We consider sequences of such
Hamiltonians for which the spectral measures associated to the coupling functions by the bath
Hamiltonians converge weakly to a limiting measure that is absolutely continuous with a Hölder continuous density near the excited energy. Under this assumption, we show that the survival probability of the excited state decays in an approximately exponential manner on suitable time scales and under favourable conditions, with a decay rate given by
Fermi's golden rule for the limiting measure. The error is estimated in terms of the coupling strength and the Lévy distance between the discrete spectral measures and the limiting measure. As an application, we treat a two-level atom coupled to a massless bosonic field confined to a large cavity in the rotating-wave approximation.
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Earth and Planetary Astrophysics
Twin Impact Lunar Telescope network: Lunar Impact Flash observations of the 2025 Geminids
Daniel Sheward, Marco Delbo, Chrysa Avdellidou et al. (+23 more)
Meteoroid impacts on the Moon, observed from Earth as flashes typically lasting a few tens of milliseconds, have been monitored for three decades for determining meteoroids' size and mass frequency distribution in the cm to dm range. Studies link these observed impact events to fresh craters advancing our understanding of energy partitioning during an impact. Currently we are transitioning to a new era where lunar impact flashes (LIFs) can be used to supplement upcoming lunar seismology to study the internal lunar structure. Here we present results from the first station of a
telescope network under development for continuous LIF monitoring. Observations were carried out during the Geminids 2025 campaign, initiated by the LUMIO Science Team in the framework of their public engagement activities. We detected 53 potential impact flashes and confirmed 11 of them through multiframe observations, and independent detections by other observers. We present evidence suggesting that some of the yet unconfirmed events may be real. Our confirmed events range between magnitude +7.5 and +10.4, primarily in the V and R band. We obtained a high rate of observations per hour, highlighting the importance of high ZHR meteoroid streams for observing LIFs. We also discuss the scientific value of potential LIFs that remain unconfirmed in optical data alone. Even without multi station confirmation, these events can correlate to seismic signals in future lunar seismic networks, thereby providing useful physical constraints on impact processes. This approach would also allow stations equipped with a single
telescope/camera to meaningfully contribute to the network.
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All authors Daniel Sheward, Marco Delbo, Chrysa Avdellidou, Philippe Lognonné, Jeremie Vaubaillon, Pierre-Yves Froissart, Christelle Saliby, Paul Girard, Nicolas Mauclert, Bruno Mongellaz, Laurent Herrier, Nicolas Anfosso, Thierry Parra, Fausto Giacometti, Andrea Ferrero, Jean-Pierre Rivet, Elisa Maria Alessi, Anthony Cook, Detlef Koschny, James Dawson, Chris Hooker, Alex Pratt, Michael O'Connell, Aldo Tonon, Vincenzo della Vecchia, Luigi Zanatta
Optics
Universal Phase Contrast in Micro-CT Systems
Grammatiki Lioliou, Alberto Astolfo, Marco Endrizzi et al. (+3 more)
Conventional high-resolution micro-CT systems are regarded as attenuation-based unless visible Fresnel fringes reveal the presence of propagation-based phase contrast. Here we show that this interpretation is incomplete. When propagation-induced phase transfer is non-negligible relative to the system blur, micro-CT operates in a phase-transfer regime in which propagation improves spatial resolution relative to that expected from source and detector blur alone, irrespective of whether Fresnel fringes remain visible. Because micro-CT systems possess finite source and detector blur, this phase transfer is accompanied by a degree of hardware-induced phase
retrieval (HIPR), ranging from under-HIPR to matched-HIPR and over-HIPR. We further identify detector-induced phase
retrieval (DIPR) as the optimal case in which the detector provides all of the filtering required for phase
retrieval, thereby preserving the phase-induced resolution enhancement while introducing spatial correlations between detected
photons that reduce high-spatial-frequency noise. We derive analytical conditions for HIPR and DIPR, introduce frequency-domain metrics quantifying preserved phase transfer and detector compatibility, and validate the framework numerically with simulations and experimentally using custom and commercial micro-CT systems. Our results demonstrate that phase-induced resolution enhancement can occur in conventional micro-CT systems even in the absence of visible Fresnel fringes, changing how image formation, spatial resolution, and optimization should be interpreted.
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All authors Grammatiki Lioliou, Alberto Astolfo, Marco Endrizzi, David Bate, Charlotte K. Hagen, Alessandro Olivo
Soft Condensed Matter
Substrate contact angle governs microgel shape, stiffness and deposition pattern
M. Friederike Schulte, Sebastian S. Meyer, Timon Kratzenberg et al. (+7 more)
Soft microgels are widely used as deformable building blocks for two-dimensional assemblies, yet solid substrates are often treated as passive supports after interfacial deposition. Here, we show that substrate wettability mechanically preconditions soft microgels before drying. Using in-
liquid force-volume atomic force microscopy, we find that the same microgels adopt markedly different hydrated shapes and stiffness profiles depending on substrate contact angle: hydrophobic substrates induce spreading, flattening, and internal stiffening, whereas hydrophilic substrates preserve taller, softer microgels with smaller contact areas. These single-microgel states can explain how Langmuir-Blodgett-deposited monolayers respond during drying. On hydrophilic substrates, the observed assemblies are consistent with soft and weakly immobilized microgels rearranging under immersion-capillary forces, producing distinct corona-corona and core-core contact states and an apparent isostructural transition. On hydrophobic substrates, the flattened and stiffened microgels are more strongly immobilized, likely suppressing capillary-driven rearrangements and largely preserving the transferred interfacial assembly structure. These findings establish substrate-controlled microgel mechanics as the missing link between interfacial self-assembly and the final structures observed after transfer and drying.
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All authors M. Friederike Schulte, Sebastian S. Meyer, Timon Kratzenberg, Simon Schog, Jesco M. Schönfelder, Silke Klein-Kormelink, Tim Blinzer, Matthias Karg, Walter Richtering, Marcel Rey
Quantum Gases
Dissipation-enhanced vortex clustering in a compressible quantum fluid
P. Comaron, M. Matuszewski, D. Sanvitto et al. (+2 more)
Vortex clustering is commonly associated with conservative two-dimensional
quantum-fluid dynamics. Therefore, particle loss is mainly expected to limit clustering by shortening the time available for
vortex correlations to develop. Here we show instead that particle loss can enhance transient
vortex clustering beyond the conservative
evolution. We numerically study freely decaying, confined two-dimensional condensates initialized with random distributions of
vortices and antivortices, and find a pronounced nonmonotonic dependence of the maximum clustering on particle lifetime. The enhancement is strongest at intermediate particle-loss rates, where loss-induced background rarefaction and incompressible kinetic energy relaxation occur on comparable timescales. Our results identify a finite dynamical window, selected by linear particle loss, in which a confined compressible
quantum fluid develops stronger same-sign
vortex correlations than in the conservative limit.
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All authors P. Comaron, M. Matuszewski, D. Sanvitto, D. Ballarini, A. S. Lanotte
Materials Science
Tuneable magnetic behaviour, electronic structure and nitrogen vacancy formation in Gd$_{x}$Sm$_{1-x}$N
Omri Porat, Elma Joshy, Jackson Miller et al. (+2 more)
The rare earth nitrides are the only series of intrinsic
ferromagnetic semiconductors where the interplay of
spin and unquenched orbital angular momentum provides access to a range of
magnetic behaviour. Furthermore, the
magnetic properties can be finely tuned through the combination of multiple lanthanide ions in the nitride. Here we present a combined computational and experimental study on the electronic and
magnetic properties of Gd$_x$Sm$_{1-x}$N and discuss the effect of cation substitution on the internal exchange field and band structure. We find that as the coercive field of Gd$_x$Sm$_{1-x}$N changes over orders of magnitude via cation substitution the internal exchange field changes by $\sim$20%. Control of these material properties is vital in the field of superconducting spintronics. Finally, motivated by an enhanced concentration of nitrogen vacancies in films with higher Sm content, we investigate computationally the formation of nitrogen vacancy defects in Gd$_x$Sm$_{1-x}$N finding that the formation energy is significantly reduced for vacancy sites adjacent to Sm ions rather than Gd ions.
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All authors Omri Porat, Elma Joshy, Jackson Miller, Simon Granville, William Holmes-Hewett
Optics
Tomographic Phase Imaging with Randomized Probe Imaging
Jordan T. O'Neal, Byeongdu Lee, Soenke Seifert et al. (+6 more)
We demonstrate tomographic phase imaging of cubic gold nanoparticles with sub-100 nm resolution requiring just a single far-field coherent diffraction pattern per projection. By using randomized probe imaging (RPI), a real-space amplitude and phase image can be reconstructed from a single diffraction pattern. These phase images are then fed into a standard tomographic workflow to retrieve the 3D volume. Nanoscale X-ray phase
tomography has often relied on ptychography, which requires slow 2D scanning for each projection. By using RPI, the data collection is greatly sped up at the cost of some resolution. We compare an RPI-
tomography volume to a ptychography-
tomography volume of the same sample, finding high consistency between the two methods. To the best of our knowledge, this is the first application of RPI to
tomography.
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All authors Jordan T. O'Neal, Byeongdu Lee, Soenke Seifert, Hanna Ruth, Michael Wojcik, Haidan Wen, Yanqi Luo, Yi Jiang, Junjing Deng
Quantum Physics
Phase Sensitivity of Spectrally Multimode SU(1,1) Interferometers with Waveguide based Optical Parametric Amplifier
Sonu Jana, Swagatam Bag, Fabien Bretenaker et al. (+2 more)
We present a comprehensive framework for evaluating the phase sensitivity of spectrally multimode SU(1,1) interferometers probed with a coherent-
vacuum input, under both number and homodyne detections. The optical parametric amplifiers (OPAs) are simulated using a periodically polled thin-film lithium niobate waveguide. The theoretical model incorporates the intrinsic multimode spectral nature of waveguide-based OPAs. Under the assumptions of identical OPAs and Schmidt-mode-independent phase shifts, we have shown that the multimode SU(1,1) interferometer is equivalent to a collection of independent single-mode interferometers in the Schmidt basis that operate in parallel, each associated with a Schmidt mode of the parametric process. We further present an optimized waveguide design based on asymmetric group-velocity matching to realize a practical OPA with nearly factorizable joint spectral amplitude (JSA). The Schmidt coefficients extracted from the numerically simulated JSA are incorporated into the theoretical model to evaluate the phase sensitivity. The results show that the sensitivity under a multimode condition depends strongly on the measurement scheme. For number detection, the degradation in sensitivity arises from the redistribution of the available nonlinear resource among the Schmidt modes, whereas homodyne detection exhibits an additional coherence penalty that can be substantially reduced by optimally shaping the local oscillator. Moreover, we show that the performance degradation can be to a large extent mitigated by optimizing the spectrum of the injected signal coherent state and, in the case of homodyne detection, the spectrum of the local oscillator. Altogether, this work provides a unified theoretical and numerical framework for analyzing and optimizing realistic multimode SU(1,1) interferometers with waveguide-based OPAs for
quantum-enhanced sensing applications.
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All authors Sonu Jana, Swagatam Bag, Fabien Bretenaker, Nadia Belabas, Syamsundar De
Quantum Physics
A spectral viewpoint on the single defect tight-binding chain
Sayan Roy
We analyze the time
evolution of the nearest-neighbour tight-binding chain in the presence of a single onsite defect. Such a defect was shown to generate non-trivial transport behavior recently in the article by Acharya et al J. Stat. Mech. (2026) 043102. The authors have used a defect technique inspired by classical random walk methods to obtain exact analytical expressions for the occupation probability and subsequently the mean and mean-squared displacement (MSD). Here we derive the same results using a spectral decomposition approach. Starting from the secular equation, we obtain the self-consistency condition for the
eigenvalues and construct the corresponding normalized eigenvectors. This approach naturally separates the
Hilbert space into a dark subspace, whose states have zero amplitude at the defect site and remain unaffected, and bright subspaces, whose states get modified because of the defect. Using this
eigenvalue decomposition, we provide a spectral origin of non-monotonicity in the MSD. Numerical calculations for finite chains show that the analytically estimated critical defect strength is in excellent agreement with the defect strength that minimizes the MSD.
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Physics and Society
Poverty Mapping: Data, Models and Applications
Suoyi Tan, Mengning Wang, Yixiu Kong et al. (+5 more)
Poverty mapping is increasingly important for monitoring Sustainable Development Goal 1 (SDG 1) of the United Nations 2030 Agenda, which aims to end poverty in all its forms everywhere. Yet timely and fine-resolution poverty estimation remains difficult because conventional census- and survey-based approaches are costly, infrequent, and often sparse precisely where deprivation is most severe. As poverty emerges from complex socioeconomic systems shaped by human mobility, social interactions, infrastructure, and economic activities, emerging computational methods and nontraditional data sources have created new opportunities for poverty estimation and mapping. At the intersection of statistical physics, complex systems science, and data science, these approaches enable poverty estimation at finer spatial and temporal resolutions. This review summarizes the main concepts of poverty and the principal frameworks used to measure it, and examines recent advances on poverty estimation and mapping using satellite imagery, mobile phone data, social media data, and multisource data fusion. The review also discusses persistent challenges related to representativeness, transferability across regions, interpretability, and uncertainty quantification. Finally, the review clarifies both the analytical promise and the practical limits of contemporary poverty mapping.
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All authors Suoyi Tan, Mengning Wang, Yixiu Kong, Huimin Bai, Jianguo Liu, Dirk Brockmann, Yicheng Zhang, Xin Lu
Solar and Stellar Astrophysics
The Fe I 4377 Å Line as a Solar Faculae Indicator: Insights from Spectral Ratio Analysis
Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes et al. (+21 more)
Faculae are a dominant source of
stellar activity noise in radial velocity measurements, yet their low contrast and broad surface distribution make them difficult to track in disc-integrated observations. We apply Spectral Ratio Analysis (SRA) to HARPS-N Sun-as-a-
star observations to isolate and characterize the spectral imprint of facular regions over rotational timescales. The resulting SRA spectra show coherent, line-dependent variability sensitive to surface
magnetic activity, with the Fe I 4377 Angstrom line exhibiting a particularly strong diagnostic response to facular coverage. We interpret the observed signatures using two complementary synthetic frameworks: composite PHOENIX spectra, from which we derive best-fit facular temperature contrasts in the range 200-400 K, and MPS-ATLAS spectra synthesized using MURaM simulations of the quiet Sun including a small-scale dynamo and magnetically-enhanced facular analogues with initial mean vertical
magnetic fields of 100G, 200G, and 300G. Both approaches are benchmarked against facular filling factors measured from
Solar Dynamics Observatory (SDO) disc-resolved images. We find good agreement between SDO-measured and SRA-inferred filling factors using the Fe I 4377 Angstrom line, with Pearson R coefficients of 0.587-0.927 across models and timescales. The estimated filling factors track the
solar activity cycle, rising from ~1.5% at lower activity to ~5.5% at higher activity, consistent with SDO-measured filling factors. These results demonstrate that SRA offers a means to reliably track surface
magnetic activity in disc-resolved spectra, which is necessary for mitigating the effects of activity on RV characterization of
exoplanet masses and atmospheres at modern precision.
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All authors Katlyn L. Hobbs, Christopher A. Watson, Jean C. Costes, Yvonne Unruh, Dana Clarice Yaptangco, Krishnamurthy Sowmya, Mitchell E. Young, Ernst J. W. de Mooij, Alexander G. M. Pietrow, Pál Váradi Nagy, Alexander I. Shapiro, Veronika Witzke, Federica Rescigno, Ryan A. Rubenzahl, Megan Bedell, Andrew Collier Cameron, Xavier Dumusque, Sean M. O'Brien, Benjamin M. J. Cadell, Baptiste Klein, Niamh Mallaghan, Niamh K. O'Sullivan, Toby Rodel, Sara Tavella
High Energy Astrophysical Phenomena
Rates of tidal disruption events from constrained cosmological simulations of the local Universe: population properties and implications for transient surveys
Julian S. Sommer, Ildar Khabibullin, Klaus Dolag et al. (+4 more)
(abridged) Motivated by upcoming surveys like LSST, we estimate
tidal disruption event (TDE) rates using the constrained cosmological Simulation of the LOcal Web (SLOW) to test the limitations of traditional 2D analytical extrapolations within a fully 3D framework. We aim to provide reliable TDE budgets extracted from the simulated zoom-in volumes of the digital counterparts of the Coma, Hercules, Shapley, Virgo, and Perseus supercluster environments, and the Fornax
galaxy cluster. From the zoom-in boundary volumes of the six environments, reaching radial extents of $55-92\,$Mpc, we extracted black hole demographics (including
spin) and their host
galaxy properties to establish a filter scheme that strictly preserves dynamically stable "main-sequence" black holes. We further classified host
galaxies as cuspy or cored based on the slope of their 3D
stellar density profile measured within $1\,$kpc as a proxy for unresolved
nuclear structure and applied the relativistic Kesden efficiency correction to the filtered sample. We find an average volumetric and per black hole TDE rate of $\approx 600\,$Gpc$^{-3}\,$yr$^{-1}$ and $\approx 4.5\times 10^{-5}\,$yr$^{-1}$ across all six environments, respectively. Although our absolute TDE rates match early literature estimates, the underlying spatial distribution fundamentally differs. Central core rates are heavily reduced by dynamical depletion and direct capture constraints, meaning the total TDE budget is overwhelmingly dominated by cuspy satellite
galaxies in the extended cluster
halos. TDE yields are driven by black hole demographics and spatial concentration rather than total cluster mass. Actively assembling superclusters (e.g., Hercules) reduce per-black-hole TDE efficiencies via merger-driven black hole mass growth, whereas low-mass environments (e.g., Fornax) are highly efficient due to unmerged, low-mass black holes.
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All authors Julian S. Sommer, Ildar Khabibullin, Klaus Dolag, Luca Sala, Benjamin Seidel, Jenny G. Sorce, Alice Damiano
Quantum Physics
Yann Tal
We give a bounded-error
quantum algorithm that, given a
prime $p$, a divisor $q\mid(p-1)$, and an integer $0<n<p$, computes $n!\bmod p$ in expected time $\widetilde{O}(q^c+\sqrt{p/q})$ for some absolute constant $c\ge 1$. When $p-1$ has a divisor of size $q\approx p^{1/(2c+1)}$, this gives the exponent $c/(2c+1)<1/2$. To our knowledge, this is the first
algorithm to break the exponent $1/2$ barrier for modular factorials under such a divisor promise. The main technical ingredient is a
quantum algorithm that reconstructs the relevant Jacobi sum exactly in compact algebraic form, with
polynomial dependence on $q$ and $\log p$. We further extend the same asymptotic bound to the computation of $n!\bmod p^2$, uniformly over $0\le n<p^2$. At $n=p-1$, this determines the Wilson quotient $\frac{(p-1)!+1}{p}\pmod p$. We
conjecture that the condition $q\mid(p-1)$ is a technical limitation of the present method rather than an inherent obstruction, and that a uniform
quantum algorithm exists for all
primes.
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Materials Science
A Unified Symmetry Framework For In-plane Anomalous Hall effect
Xun-Jiang Luo, Yong-Ting Shi, Ding-Fu Shao et al. (+3 more)
The in-plane anomalous
Hall effect (IPAHE), driven by an in-plane net magnetization or an applied
magnetic field, challenges the conventional anomalous
Hall paradigm. Despite growing interest, a unified
symmetry principle governing these phenomena has remained elusive. Here, we establish a comprehensive
symmetry framework that bridges the
spin space group, which dictates the
magnetic geometry, with the
magnetic space group, which governs the anomalous
Hall response. We show that spontaneous IPAHE can emerge in ferromagnets when
spin-orbit-coupling-induced
spin-group
symmetry breaking permits additional net magnetization directions. For field-induced IPAHE, we analyze how an applied
magnetic field reduces the
symmetries of all 122
magnetic point groups and identify 54 groups that support IPAHE. Our framework naturally predicts IPAHE in a broad class of unconventional magnets, including altermagnets and odd-parity magnets. In particular,
symmetry analysis reveals characteristic one-, two-, or three-fold angular harmonics of the
Hall conductance under an in-plane rotating field, providing a
symmetry-resolved fingerprint for unconventional magnetism. Using this framework, we screen the MAGNDATA database and identify candidate materials supporting spontaneous or field-induced IPAHE, encompassing ferromagnets, antiferromagnets, and unconventional magnets. Finally, we validate the
symmetry predictions through first-principles calculations for two representative materials.
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All authors Xun-Jiang Luo, Yong-Ting Shi, Ding-Fu Shao, Ping Zhang, Ning Hao, Mingliang Tian
High Energy Physics (Theory)
BPS Invariants for Generalized Toric Calabi-Yau Threefolds
Antoine Bourget, Peng Cheng and Quentin Lamouret
We apply topological vertex techniques to Calabi-Yau threefolds dual to brane webs where several 5-branes can end on the same 7-brane. In this context, we determine how topological string partition functions transform under Hanany-Witten transitions and flops, which allows us to track curves and the associated invariants under such transitions. The contributions of parallel external branes form a universal sector invisible to the 5d SCFT; once it is removed, invariants can be transported between different geometries engineering the same theory. This yields an efficient technique to compute Gopakumar-Vafa invariants at any degree and genus. We illustrate this with local Hirzebruch and del Pezzo surfaces, including $dP_4$, whose invariants we obtain at high degree for the first time.
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Statistical Mechanics
Optimal Navigation on Simplicial Complexes
Diego Febbe, Duccio Fanelli, Gianluca Peri et al. (+1 more)
The
navigation time and optimal search strategies deriving from random dynamical processes on binary graphs have been extensively explored and analyzed, being of prominent interest in the network science field. In this work, we study an extension of these topological measures for simplicial complexes: a specific type of
geometric and algebraic structures that encapsulates higher-order interactions. Here, the explorability analysis of simplicial complexes has been conducted in terms of the mean first passage times between nodes, i.e. the 0th-order simplices, with the inclusion of a long-range
stochastic teleportation term modulated with respect to the local random walk hopping across the various dimensions. We also provide a perturbative approximation scheme recovering the modulation parameter between pure random walk and teleportation mode (for higher-order setting) acting as the expansion parameter.
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All authors Diego Febbe, Duccio Fanelli, Gianluca Peri, Timoteo Carletti
General Relativity and Quantum Cosmology · Cross-listed from math.DG
The Penrose inequality with charge for 2-convex initial data sets
Tuan Dolmen
We prove the Penrose inequality with charge under the 2-convexity condition recently introduced by Dong. More precisely, given a complete, connected and asymptotically flat Einstein-Maxwell initial data set $(M,g,k; E,B)$ satisfying the charged dominant energy and the 2-convexity conditions, with divergence-free electromagnetic vector fields $(E,B)$ and a connected outermost past apparent horizon $\Sigma$ that satisfies $|\Sigma| \geq 4\pi q^2$ - where $q$ is the total charge - we show that the following inequality for the ADM mass $m$ holds: $m\geq \sqrt{\frac{|\Sigma|}{16\pi}} + q^2 \sqrt{\frac{\pi}{|\Sigma|}}$, with equality if and only if $k \equiv 0$ and $(M,g;E,B)$ is isometric to a canonical slice of sub-extremal Reissner-Nordström spacetime. Building on Dong's proof of the uncharged case, we use his $\mathbf{P}$-inverse mean
curvature flow and its weak formulation, which only depends on $(g,\mathbf{P})$ and hence applies to the charged setting unchanged. The novelty of our work is the modification of the monotonicity formula to account for the additional charge term. For time-symmetric data ($k \equiv 0$), the flow reduces to the classical inverse mean
curvature flow and our monotonicity formula to Jang's monotonicity of the charged Hawking mass, recovering the charged Riemannian Penrose inequality.
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