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Physics

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Wednesday 19 August

Quantum Physics

Interior skin focusing and directional mirror transfer in a graded non-Hermitian Krawtchouk network

Y. S. Liu and X. Z. Zhang

Spatially graded nonreciprocity can move skin weight away from a boundary, but it does not generally preserve a real commensurate spectrum or analytically controlled dynamics. We study a finite open Krawtchouk network with oppositely graded directed hoppings. For a broad intermediate range of asymmetries, their local imaginary gauge field changes sign in the bulk, and its accumulated coordinate generates a positive diagonal similarity map whose normalized squared entries form a biased-binomial envelope. The same map converts the open chain into the spin-rotation generator \(2gJ_x\), so the focus and equally spaced spectrum follow from one grading. In this focusing regime, exact right, left, and biorthogonal eigenvectors show that the envelope width and participation number both scale as \(\sqrt N\), identifying a subextensive interior focus. In the physical node basis, spin rotation produces perfect mirror inversion with direction-selective amplification and attenuation whose gains are mutually inverse. The directional Green functions share their poles, while their residues differ by the same similarity ratio. Closing the chain exposes a gauge-invariant imaginary flux, and either exact one-way limit yields an exceptional point of order \(N\). Onsite disorder preserves the directional resolvent ratio, whereas independent hopping disorder breaks the clean analytic Krawtchouk map and degrades commensurability and transfer. The model therefore provides an exactly solvable finite-network framework linking localization geometry and eigenvector nonorthogonality to commensurate spectra and node-resolved directional response.
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History and Philosophy of Physics

Could John Ellard Gore have pre-empted the Hertzsprung-Russell diagram?

Jeremy Shears

John Ellard Gore (1845-1910) was an Irish amateur astronomer, prolific science writer and civil engineer. He was an inaugural member of the British Astronomical Association when it was founded in 1890 and was invited to become the first Director of its Variable Star Section. Through careful reasoning, Gore reached remarkably modern conclusions about the nature of stars, including their sizes, distances and luminosities. This paper explores whether he might have been able to produce an early form of what is now known as the Hertzsprung-Russell (H-R) diagram.
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Optics

Interference-engineered shortcut to perfect state transfer

Yichuan Zhang, Xuanyu Liu, Zemeng Lin et al. (+2 more)

Achieving fast, high-fidelity state transfer is fundamental to scalable integrated photonics and quantum information processing. While adiabatic evolution provides inherent robustness against control and fabrication imperfections, its requirement for slow driving leads to impractically long propagation distances in photonic circuits. Existing acceleration strategies, such as shortcuts to adiabaticity (STA), can dramatically shorten evolution times but generally rely on non-native auxiliary couplings or delicate Hamiltonian engineering that are difficult to implement in practice. Here we introduce evolution-pause synthesis (EPS), an interference engineered shortcut protocol that achieves fast, near-perfect state transfer strictly within the native system Hamiltonian. It achieves this by treating transient excitations as coherent resources and canceling their accumulated amplitudes via strategically interleaved pauses. By decoupling relative dynamical phase accumulation from parameter variations, EPS steers open transition trajectories into a closed loop in complex amplitude space, enabling perfect state transfer without auxiliary fields or complex parameter detours. We demonstrate this mechanism in Landau-Zener dynamics and extend it to a multilevel STIRAP process, achieving an 11.8-fold acceleration over the adiabatic baseline. Further, we experimentally validate EPS on a silicon photonic platform, realizing high-fidelity state transfer in a $16\,{\mu}\mathrm{m}$ footprint, a nearly tenfold reduction in device length compared with a $150\,{\mu}\mathrm{m}$ adiabatic reference. EPS offers a general hardware-compatible framework for fast, practical coherent control across wave and quantum platforms.
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All authors Yichuan Zhang, Xuanyu Liu, Zemeng Lin, Wange Song, Shuang Zhang

Instrumentation and Methods for Astrophysics

Millimeter and sub-millimeter characterization of polymers used for infrared filters in high-sensitivity cryogenic microwave telescopes

Miranda Eiben, Rustam Balafendiev, Thomas Gascard et al. (+1 more)

Vacuum windows and infrared filters are important transmissive optical components in millimeter receivers, as they hold out the atmosphere and reduce radiative loading on cold stages, thereby improving cryogenic performance. However, the complex optical properties of the materials commonly used for windows and filters are poorly characterized, particularly in-band and in the sub-millimeter regime. The absorption and scattering properties of these materials are becoming increasingly important for designing high-sensitivity millimeter instruments, as their loosely constrained properties are one of the greatest sources of uncertainty remaining in noise modeling. We report the absorption in the millimeter and sub-millimeter regime of nylon 6, nylon 6/6, PTFE and polyethylene (both bulk HDPE and foam HDPE used in radio transparent filter stacks). Additionally, we report the relative power scattered out of the main beam by these materials from 90 to 330 GHz, measured in free space by a robot-enabled scanning vector network analyzer.
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All authors Miranda Eiben, Rustam Balafendiev, Thomas Gascard, Jon E. Gudmundsson

Physics and Society

Removing Population Size, World Cities Leave on Land a Footprint of Wealth

Victor Vignolles and Rémi Lemoy

Urban expansion builds on precious arable land, affecting ecosystems and health, despite worldwide measures to alleviate its impacts, in small and large cities. Nonetheless, the link between urban extent and population size is still unclear. Here we uncover a scaling law governing built-up land in 1800+ global urban areas. We observe that world cities have homothetic (or isometric) radial land use profiles, and that built-up footprint is proportional to total population. This spatial scaling law is important for the understanding and the definition of urban areas, to help build a science of cities and make them more sustainable. It implies that small and large cities have similar internal structures, and that built-up area per capita is constant across city sizes. The remaining variations are very strongly correlated to wealth measured by gross domestic product per capita, suggesting a pick between economic development and sustainabiliy.
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Geophysics

Scaling-law-informed neural point processes for earthquake sequence forecasting

Tianlu Xiong, Zaibo Zhao, Yunrui Li et al. (+3 more)

Earthquake sequence forecasting requires models that can learn nonlinear history dependence while retaining robust statistical structure. We develop a scaling-law-informed neural marked point process, termed Fusion, that combines neural representations of catalog history with temporal features derived from the Epidemic-Type Aftershock Sequence model and magnitude information derived from the Gutenberg–Richter law. The model separates the magnitude cutoff applied to the input catalog from the fixed target-event threshold, allowing lower-magnitude earthquakes to inform forecasts without changing the target-event set. For the 2016–2017 Amatrice–Visso–Norcia sequence, Fusion achieves the highest target-event temporal likelihood when lower-magnitude events are retained, outperforming both ETAS and a purely neural point-process baseline. Event-wise and cumulative analyses show sustained timing gains through substantial portions of the Visso and Norcia sequences. Across five benchmark catalogs, catalog-specific neural training with a fixed ETAS prior yields the highest temporal likelihood at the minimum evaluated magnitude cutoff. Magnitude likelihood shows no consistent predictive gain beyond the Gutenberg–Richter-based ETAS reference, indicating that the additional information captured by Fusion is primarily temporal. These results show that lower-magnitude catalog histories and empirical scaling-law information complement neural sequence learning for target-event timing.
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All authors Tianlu Xiong, Zaibo Zhao, Yunrui Li, Wenqi Liu, Yosef Ashkenazy, Yongwen Zhang

History and Philosophy of Physics

The Birth of Radar Meteor Astronomy at Jodrell Bank: The Collaboration between Bernard Lovell and Manning Prentice

Jeremy Shears

The discovery of radar echoes from meteor trains at Jodrell Bank in December 1945 heralded the beginning of a new era in meteor astronomy. This paper examines the early collaboration between Bernard Lovell, whose expertise in radar and physics transformed wartime technology into a new astronomical technique, and J. P. Manning Prentice, Director of the British Astronomical Association Meteor Section, whose knowledge of visual meteor observation proved essential to interpreting the discoveries. Drawing on previously unpublished correspondence from the Lovell Archive at the University of Manchester, the paper traces the development of their partnership, including the pioneering 1946 Perseid and Giacobinid observations, the contribution of BAA observers, and the establishment of radar meteor research at Jodrell Bank. It reveals how complementary professional and amateur expertise combined to create a new field of astronomy and a lasting scientific friendship.
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High Energy Physics (Phenomenology)

Modelling electroweak interactions at lepton colliders - from the Z pole to the highest energies

Krzysztof Mękała

Despite the Standard Model's ability to describe collider data from all experiments conducted around the world, several questions about the history of the Universe, including the hierarchy problem, the baryon asymmetry, and the dark matter density, remain open. To address these unresolved issues, the particle physics community agrees on the need to construct a next-generation collider that could probe the Standard Model with higher accuracy and potentially reveal deviations from the predictions of this fundamental theory. Future lepton colliders, operating at energies from the Z pole up to the multi-TeV scale, could probe the electroweak sector in various ways. In this thesis, the influence of radiative corrections on the modelling of electroweak processes is investigated.
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Astrophysics of Galaxies

Size-Mass Relation Shows Its Colours: Contrasting Physical Imprints of Galaxy Evolution in Rest-Frame UV and Optical

Angelo George, Marcin Sawicki and Ivana Damjanov

The galaxy size-mass relation (SMR) is a key scaling relation used to constrain the physical processes that build galaxy structure, yet it is almost always measured in a single rest-frame optical band, where the light traces the bulk of the old stellar mass. Tracing younger populations with flux-weighted ages of ~100-500 Myr and low-metallicity stars, the rest-frame near-ultraviolet opens a new stellar window on this scaling relation. Because each process redistributes the light of young and old stars differently, the same mechanism shifts the slope and zero point of the SMR by different amounts in the two wavelength regimes. Here we review and synthesize the effects of main physical processes on the form of the SMR for star-forming and quiescent galaxies in the rest-UV and optical. For each process, we start from its underlying physics, the galaxy stellar masses it affects, and the light it adds/removes/rearranges, anchoring the predictions to observations and simulations. We validate the predicted imprints with forward Monte Carlo modelling. The two-wavelength view breaks several degeneracies that single-band analyses cannot, most notably between minor mergers, dry major mergers, and adiabatic expansion. These results motivate joint rest-UV and optical SMR measurements with current and upcoming wide-field imaging surveys.
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Nuclear Experiment

Improved $^{94}$Mo neutron resonance parameters from neutron capture and transmission measurements at n_TOF and GELINA

R. Mucciola, S. Cristallo, S. Kopecky et al. (+140 more)

We report high-resolution measurements of the $^{94}\mathrm{Mo}(\mathrm{n},\gamma)^{95}\mathrm{Mo}$ cross section in the neutron energy range from a few eV up to about 250 keV, performed at the n_TOF facility (CERN), and of the $^{94}\mathrm{Mo}(\mathrm{n},\mathrm{tot})$ cross section up to 32 keV, measured at GELINA (JRC Geel). A combined R-matrix analysis of capture and transmission data yields significantly improved neutron-resonance parameters for $^{94}$Mo. A total of 186 resonances were observed in this analysis of which 127 reported here for the first time. The resulting Maxwellian-averaged cross section at stellar temperatures relevant to the slow neutron-capture process (s-process) is approximately 25% lower than previous evaluations and literature values. To assess the astrophysical impact of the revised cross section, we performed s-process nucleosynthesis calculations for low-mass asymptotic giant branch stars. Despite the substantial reduction in the $^{94}\mathrm{Mo}(\mathrm{n},\gamma)^{95}\mathrm{Mo}$ rate, the final yields vary by only 3-4%. This demonstrates that the isotopic budget of $^{94}$Mo in AGB stars is primarily governed by the branching flow at $^{94}\mathrm{Nb}$ rather than by the neutron-capture destruction on $^{94}$Mo itself. The new cross section thus helps disentangle nuclear cross-section uncertainties from branching-flow effects in the s-process production of $^{94}$Mo.
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All authors R. Mucciola, S. Cristallo, S. Kopecky, N. Liu, C. Massimi, A. Mengoni, A. Manna, C. Paradela, P. Schillebeeckx, G. Sibbens, D. Vescovi, O. Aberle, V. Alcayne, S. Altieri, S. Amaducci, J. Andrzejewski, V. Babiano-Suarez, M. Bacak, J. Balibrea-Correa, C. Beltrami, S. Bennett, A. P. Bernardes, E. Berthoumieux, R. Beyer, M. Boromiza, D. Bosnar, M. Caamano, F. Calvino, M. Calviani, D. Cano-Ott, A. Casanovas, D. M. Castelluccio, F. Cerutti, G. Cescutti, S. Chasapoglou, E. Chiaveri, P. Colombetti, N. Colonna, P. Console Camprini, G. Cortes, M. A. Cortes-Giraldo, L. Cosentino, S. F. Dellmann, M. Diakaki, M. Di Castro, M. Dietz, S. Di Maria, C. Domingo-Pardo, R. Dressler, E. Dupont, I. Duran, Z. Eleme, S. Fargier, B. Fernandez, B. Fernandez-Dominguez, P. Finocchiaro, S. Fiore, V. Furman, F. Garcia-Infantes, A. Gawlik-Ramiega, G. Gervino, S. Gilardoni, E. Gonzalez-Romero, S. Goula, C. Guerrero, F. Gunsing, C. Gustavino, J. Heyse, W. Hillman, D. G. Jenkins, E. Jericha, A. Junghans, Y. Kadi, K. Kaperoni, G. Kaur, A. Kimura, I. Knapova, M. Kokkoris, Y. Kopatch, M. Krticka, N. Kyritsis, I. Ladarescu, S. Lanzi, C. Lederer-Woods, J. Lerendegui-Marco, G. Lerner, T. Martinez, A. Masi, P. Mastinu, M. Mastromarco, E. A. Maugeri, A. Mazzone, E. Mendoza, V. Michalopoulou, P. M. Milazzo, F. Murtas, E. Musacchio Gonzalez, A. Musumarra, A. Negret, N. Patronis, J. A. Pavon, M. G. Pellegriti, P. Perez-Maroto, A. Perez de Rada Fiol, J. Perkowski, C. Petrone, L. Piersanti, E. Pirovano, J. Plaza del Olmo, S. Pomp, I. Porras, J. Praena, J. M. Quesada, R. Reifarth, D. Rochman, Y. Romanets, C. Rubbia, A. Sanchez-Caballero, M. Sabate-Gilarte, D. Schumann, A. Sekhar, A. G. Smith, N. V. Sosnin, M. E. Stamati, A. Sturniolo, G. Tagliente, A. Tarifeno-Saldivia, D. Tarrio, P. Torres-Sanchez, S. Urlass, E. Vagena, S. Valenta, V. Variale, P. Vaz, G. Vecchio, V. Vlachoudis, R. Vlastou, A. Wallner, P. J. Woods, T. Wright, R. Zarrella, P. Zugec, The n_TOF Collaboration

Atomic Physics

Electron Correlation Enables Phase-Coherent One-Attosecond Pulse Trains

Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas et al. (+2 more)

Attosecond synthesis is ultimately a phase problem: a broad spectrum produces an ultrashort waveform only if its harmonics remain phase-locked. We show theoretically that correlated two-electron high-harmonic generation in helium driven by a long, multicycle laser pulse supports a train of soft-x-ray bursts with durations approaching 1 as. Using a two-electron strong-field approximation, we calculate the complex harmonic spectrum and reconstruct the temporal emission while retaining its full intrinsic spectral phase, rather than imposing a flat-phase approximation. Despite the trajectory-dependent phase accumulated by two continuum electrons, the correlation-extended plateau contains a broad phase-coherent region reaching the keV range. Its superposition produces reproducible bursts separated by one half-cycle of the driving field. These results identify electron correlation not only as a mechanism for extending the high-harmonic cutoff, but also as a route toward phase-coherent x-ray waveforms on the zeptosecond timescale.
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All authors Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas, Maciej Lewenstein, Marcelo F. Ciappina

Mesoscale and Nanoscale Physics

Electromagnetic and Acoustic Fano Interference in Surface Acoustic Wave Resonators

P.K. Rath, J.M. Kitzman, M. Mesbah et al. (+2 more)

Surface acoustic wave-based resonators are sensitive probes of condensed matter systems, as well as surface-selective sensors for chemistry and biology. Surface acoustic wave devices have also been integrated into hybrid quantum systems with qubit platforms for applications in quantum information processing and sensing. The sensitivity of piezoelectric surface wave-based resonators to investigate these various systems can be enhanced by optimizing the device architecture and electrical measurement techniques. Alternatively, tailoring the spectral symmetry, arising from interference effects, offers a promising route to further improve sensitivity. In this work, we demonstrate the simultaneous introduction of both electromagnetic and acoustic Fano interference to shape the spectral response of GHz-frequency surface acoustic wave resonators. By systematically modifying the acoustic reflectivity of the resonators, we are able to isolate and analyze each interference mechanism independently. The broad range of temperature operation, from ambient to cryogenic temperatures highlights the potential for both classical and quantum sensing applications.
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All authors P.K. Rath, J.M. Kitzman, M. Mesbah, C. Undershute, J. Pollanen

Materials Science · Cross-listed from math.NA

A shifted energy barrier approach for phase-field modeling of tensile-dominated brittle fracture

Yaode Yin, Luigi Greco, Hongjun Yu et al. (+1 more)

The classical AT1 phase-field model contains an intrinsic energy barrier for crack nucle ation, which makes the predicted strength depend on the fracture toughness and the regularization length. For tensile-dominated brittle fracture, this barrier is shifted by mapping the Rankine criterion, evaluated on the effective stress, onto a state-dependent active-energy threshold. The prescribed tensile strength then controls crack nucleation, while the AT1 crack-density functional, stiffness degradation, and degraded stress response remain unchanged. Since the threshold depends on the current stress state, the field equations are derived from a restricted variational principle. A microforce formulation identifies the barrier shift as a dissipative resistance and provides the corresponding lower bound on the regularization length. In one-dimensional tension, closed-form solutions recover the prescribed peak strength and give a cosine-type localization profile that ap proaches the classical AT1 profile as the shift vanishes. Numerical examples show that, within the admissible range, the nucleation load is nearly insensitive to the regularization length and the predicted multiaxial nucleation states follow the Rankine envelope. Under overall compression, crack nucleation remains associated with local tensile stress concen trations. The formulation also captures the transition from strength-controlled failure for small flaws to the LEFM limit for large cracks.
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All authors Yaode Yin, Luigi Greco, Hongjun Yu, Simone Morganti

Materials Science

On the temperature dependence of the optical band gap in the material system of lithium niobate and lithium tantalate

Maximilian Henneke, Michael Ruesing, Nina A. Lange et al. (+13 more)

Lithium niobate and lithium tantalate see widespread use in optics and electronics, and are increasingly used for cryogenic applications. Despite their broad deployment, their optical band gap and its relation to the crystal stoichiometry are not well characterised as a function of temperature. In this work, we study the optical absorption properties of congruent, stoichiometric, MgO-doped and Er-doped lithium niobate as well as congruent lithium tantalate across the temperature range between 7~K and 1000~K by means of optical transmission spectroscopy. Our results demonstrate that the difference of the optical band gap typically observed at room temperature between different stoichiometries is not primarily attributable to the intrinsic electronic structure, but rather to different electron-phonon couplings and the average phonon energies. Additionally, we exemplarily study the temperature shift of the 523 nm absorption line in Er-doped lithium niobate due to the increased interest in optically active dopants. To facilitate future analyses, we present the open-source software suite PhoQS-Treat (Tauc Regression Edge Analysis Tool), which enables automated Tauc regressions alongside additional analytical capabilities. This work advances the development of high-performance lithium niobate-based devices.
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All authors Maximilian Henneke, Michael Ruesing, Nina A. Lange, Timon Schapeler, Noah Spiegelberg, Ernst-Lukas Kuhlmann, Elke Beyreuther, Philipp Mues, Ludmila Eisner, Lukas M. Eng, Laura Padberg, Donat J. As, Klaus-Dieter Becker, Tim J. Bartley, Christine Silberhorn, Christof Eigner

Quantum Physics

Robustness of spin state superpositions for noisy quantum metrology

Trinidad B. Lantaño, Gabriela Wójtowicz, Susana F. Huelga et al. (+1 more)

Quantum metrology faces major challenges in noisy environments, where decoherence rapidly degrades useful quantum resources. We investigate the dynamics of the precision limits given by the quantum Fisher information (QFI) for phase estimation under spatially correlated dephasing. We characterize the dynamics of the QFI by the sensitivity and degradation indicators that can be obtained as analytical expressions derived using perturbative theory treatment. These short-time and weak-noise formulas yield analytic insight into how collective-spin moments govern both (i) the noiseless sensitivity and (ii) the leading noise-induced degradation of metrological usefulness. We identify a trade-off that is intrinsic to our commuting encoding-noise structure. We analyze the QFI dynamics for the Gaussian spin state (GSS) superpositions, encompassing spin coherent state (SCS), Dicke state superpositions, spin-squeezed states, and GHZ-like states. Predictions from indicators of the QFI dynamics are compared to both the quantum Cramér–Rao bound and the measurement-specific sensitivity bounds for an optimal parameter and interrogation time under a finite total time resource. When possible, we analytically derive the measurement-specific sensitivity bounds for spin-projection and parity-based measurements.
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All authors Trinidad B. Lantaño, Gabriela Wójtowicz, Susana F. Huelga, Martin B. Plenio

General Relativity and Quantum Cosmology

Effective curvature coupling of link-based causal set propagators in $1+1$ dimensions

Arsim Kastrati

We study how a recently introduced causal-set propagator defined in terms of links responds to curvature. On sprinklings embedded in a flat 1+1-dimensional Minkowski space, this propagator is known to reproduce the massless retarded continuum Greens function on large scales. In conformally flat embeddings with constant curvature $\mathcal R$, the causal order is unchanged, but the link relationship is sensitive to the physical volume of the spanned causal diamond. We show that this volume dependence generates a leading curvature correction to the propagator. On large distances, this correction is equivalent to a continuum scalar propagator with an effective curvature coupling of the form $\xi \mathcal R$ with the coupling constant $\xi_{\rm eff}=1/6$, equivalently corresponding to an effective mass-squared parameter $m_{\rm eff}^2=\xi_{\rm eff}\mathcal R$. This coupling is not inserted by hand but emerges from the link-based path sum itself, reflecting the microscopic structure of the causal set. Numerical simulations on sprinklings embedded in $\mathrm{AdS}_{1+1}$ and $\mathrm{dS}_{1+1}$ support the predicted curvature response and indicate that the effective coupling persists as the sprinkling density is increased.
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Optics

Seeded SU(1,1) interferometry for Fourier-domain optical coherence tomography

Alejandra A. Padilla, Valentina Gacha, Daniel F. Urrego et al. (+1 more)

We demonstrate Fourier-domain optical coherence tomography (FD-OCT) based on a seeded SU(1,1) interferometer. Multilayer objects are probed with broadband light centered at 1550nm, while depth-resolved 3D images are reconstructed from photon flux measurements centered at 810nm. We show that, in the low parametric-gain regime, seeding increases the photon flux, enabling volumetric imaging with a spectrometer rather than single-photon detectors. Our analysis further shows that, under the conditions considered, seeding provides a more effective route to sensitivity enhancement than increasing the parametric gain.
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All authors Alejandra A. Padilla, Valentina Gacha, Daniel F. Urrego, Juan P. Torres

High Energy Physics (Experiment)

FAST-HEP: Compiling Declarative Analysis Workflows for High-Energy Physics and Beyond

Luke Kreczko

High-energy physics analyses increasingly rely on complex software workflows whose scientific lifetime often exceeds that of the underlying software ecosystem. Maintaining reproducibility while accommodating evolving analysis software, data formats, and execution environments therefore remains a significant challenge. These challenges are not unique to high-energy physics and are shared by many data-intensive scientific analyses. We present FAST-HEP and its workflow engine, Flow, which combines a declarative workflow language, compiler, and runtime. Flow separates the scientific description of a workflow from its implementation and execution, and compiles workflows into backend-independent execution plans through normalization, graph construction, dependency analysis, and execution planning. A common runtime then orchestrates the resulting plan using replaceable capabilities. This architecture enables static validation and modular replacement of analysis operations, execution backends, and storage technologies, while recording provenance throughout compilation and execution. Although developed for the requirements of high-energy physics analysis, Flow's workflow model and orchestration layer are domain-independent. By applying compiler techniques to scientific analysis workflows, FAST-HEP provides a foundation for workflows that are transparent, extensible, portable, and reproducible, allowing scientific analyses and their supporting software ecosystems to evolve independently.
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High Energy Physics (Experiment)

Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility

Gianluigi Arduini, Nadja Augst, Mark G. Bason et al. (+79 more)

We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $\alpha$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries.
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All authors Gianluigi Arduini, Nadja Augst, Mark G. Bason, Charles Baynham, Andrea Bertoldi, Gianfranco Bertone, Diego Blas, Daniela Bortoletto, Sougato Bose, Roberto Ales Bozzi, Oliver Buchmueller, Tamara Alice Bud, Clare Burrage, Sergio Calatroni, John Carlton, Vassilis Charmandaris, Maria Luisa Chiofalo, Pierre Cladé, Jonathon Coleman, Fabio Corsanego, Albert De Roeck, Arnaud Devienne, Fabio Di Pumpo, John Ellis, Pierre Fayet, Chris Foot, Elina Fuchs, Naceur Gaaloul, Susan Gardner, Enno Giese, Eduardo Granados, Saïda Guellati-Khelifa, Michael Guinchard, Timo Hakulinen, Tiffany Harte, Richard Hobson, Michael Holynski, Angelo Infantino, Alex Kehagias, Eva Kilian-Rademacher, Wolfgang Korsch, Damien Lafarge, Samuel Lellouch, Lucas Lombriser, Elias Lopez Asamar, J. Luis Lopez-Gonzalez, Michele Maggiore, Charline Marcel, Anna Marchant, Christopher McCabe, Gaetano Mileti, Peter Millington, Jeremiah Mitchell, Noam Mouelle, Angel Navascues Cornago, François Pillon, Rosa Poggiani, Johann Rafelski, Ernst M. Rasel, Maike Reckermann, Albert Roura, Rui Samoes, Federico Sanchez Nieto, Jack Sander, Carlo Scarcia, Jesse Schelfhout, Wolfgang Schleich, Dennis Schlippert, Ulrich Schneider, Steven Schramm, Florian Schreck, Olga Sergijenko, Marcelle Soares-Santos, Guglielmo M. Tino, Jonathan N. Tinsley, Tristan Valenzuela, Daniel Valuch, Maurits van der Grinten, Klaasjan van Druten, Ville Vaskonen, Wolf von Klitzing, Michael Werner

Mesoscale and Nanoscale Physics

A miniature evaporator for in-operando deposition of isolated atoms in a low-temperature scanning tunneling microscope

Jeongmin Oh, Hermann Osterhage, Vasily Cherepanov et al. (+5 more)

Depositing dilute atomic ensembles onto cold samples is challenging in low-temperature scanning tunneling microscopes (STM) because radiation shields and restricted internal geometries often preclude a direct deposition path, particularly in instruments designed for millikelvin operation. We present a compact, milliwatt-range evaporation source fabricated from a commercial miniature incandescent lamp and integrated directly into a millikelvin STM head. The exposed tungsten filament is coated with a micrometre-thick Fe film and positioned about 1 cm from the sample. We deposit isolated Fe atoms onto MgO/Ag(100) while operating the microscope near 5 K. Evaporation increases the STM-body temperature by only about 2 K, and the same nanoscopic surface region can be readily scanned after deposition with a lateral displacement of less than 5 nm. Differential-conductance spectra displaying symmetric inelastic steps near $\pm$14 mV identify the deposited atoms on MgO as Fe. From STM images, we estimate a local deposition flux of $1.5\times10^{-5}~\mathrm{nm^{-2}\,s^{-1}}$, corresponding to a nominal evaporator lifetime of ~150 h. The fixed evaporator enables repeated low-flux deposition without a room-temperature line of sight, the need for movable radiation shields, or mechanical evaporator access after cooldown, while preserving access to the same atomic-scale surface region before and after deposition.
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All authors Jeongmin Oh, Hermann Osterhage, Vasily Cherepanov, Sven Just, Denis Krylov, F. Stefan Tautz, Taner Esat, Ruslan Temirov

High Energy Physics (Phenomenology)

Identifying the origin of the 146-GeV excess at the LHC

P. Uttayarat, J. Julio and R. Primulando

The 146-GeV excess in the electron-muon final state reported by the CMS Collaboration offers a tantalizing hint for new physics. There are two competing explanations for the origin of the 146-GeV resonance: production via mixing with the Standard Model Higgs boson and leptophilic production through sea electrons and muons inside the proton. In anticipation that such an excess may still persist by the end of LHC Run 3, we propose three related production channels $H\gamma$, $H j$, and $H jj$, which could be used to distinguish between these two possible scenarios. Taking the two-Higgs-doublet model (2HDM) as an explicit example, we estimate that with $3000~\text{fb}^{-1}$ of the high-luminosity LHC data, the $H\gamma$ channel can provide a striking discriminating power between the mixing and leptophilic scenarios with a significance of 7.1. Combining it with the other two channels, $H j$ and $H jj$, the significance can be pushed up to 7.6.
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High Energy Physics (Phenomenology)

Genuine Tripartite Entanglement Selects Gauge-Invariant Theories

Junya Yamagishi

Recent studies have explored whether physical constants and symmetries can be selected by extremizing bipartite entanglement entropy. We extend this approach to a three-particle setting. Specifically, we consider a $2+1$-particle system in which particles $B$ and $C$ are initially entangled, and then particles $A$ and $B$ scatter without the direct participation of particle $C$ for both gluon-gluon and graviton-graviton scatterings. Using angular expansions around the forward and backward scattering limits, we analyze bipartite entanglement in the corresponding two-particle system of $A$ and $B$ and two measures of genuine tripartite entanglement (GTE), the concurrence fill and the generalized geometric measure (GGM), in the three-particle system. As is already known, the bipartite entanglement provides no universal criterion for selecting the symmetry-preserving theory: depending on the initial helicities, it may either maximize or minimize the entanglement entropy. By contrast, we find that the GTE-based analysis uniquely identifies the gauge-invariant and diffeomorphism-invariant theories as those that suppress the GTE in gluon-gluon and graviton-graviton scatterings, respectively. This result suggests a nontrivial connection between tripartite entanglement and the gauge and diffeomorphism symmetries of fundamental interactions.
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Mathematical Physics · Cross-listed from math.SP

Spectral convergence of hyperbolic surfaces and quantum ergodicity

Giacomo Gavelli

We extend the notion of Plancherel convergence, introduced in the study of compact quotients of locally compact groups, to finite-area hyperbolic surfaces and establish a quantum ergodicity theorem for Plancherel sequences. We show that the expectation values of integral operators whose kernels are uniformly bounded and have uniformly bounded propagation become asymptotically equidistributed, on average, for eigenvalues in a fixed compact interval. Our result recovers the case of multiplication operators studied by Le Masson and Sahlsten, corresponding to the degenerate case of propagation bound zero and kernels supported on the diagonal. Moreover, our result allows the systole to shrink without a uniform lower bound, with the allowed degeneration constrained by Plancherel convergence. This identifies Plancherel convergence as a natural spectral framework for quantum ergodicity on degenerating hyperbolic surfaces.
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Materials Science

Revisiting the topological properties of XMg2Bi2 (X = Ca, Sr, Ba, Yb and Eu)

Antoni Facca, Xujia Gong, Amar Fakhredine et al. (+2 more)

Density functional theory is known to underestimate band gaps in semiconductors and to over- estimate inverted band gaps, frequently exaggerating the predicted size of the topological phase diagram of materials. Employing hybrid functionals and calculating the topological invariants, we revisit the topological properties of compounds crystallizing in the CaAl2Si2-type and demonstrate that the overestimation of the inverted band gaps is particularly pronounced in compounds with this crystal structure. Among these, the class of XMg2Bi2 materials (X = Ca, Sr, Ba, Yb, and Eu) is topologically trivial for all considered cations. Our calculations show that these materi- als are narrow-gap semiconductors with direct band gaps of 0.24-0.34 eV, slightly decreasing with increasing the atomic weight of the element X. We confirm this by applying uniaxial strain and hydrostatic pressure, confirming these results. We emphasize that the experimental observation of surface states alone is insufficient to establish nontrivial topology, as trivial semiconductors may host surface states without a surface Dirac point. Consequently, since these materials are intrinsi- cally topologically trivial, any experimentally observed topological signatures should be attributed to extrinsic effects such as doping or surface reconstruction. Our results underscore the importance of accurately treating electronic correlations when assessing topological character, even in materials containing heavy elements with strong spin-orbit coupling, such as bismuth.
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All authors Antoni Facca, Xujia Gong, Amar Fakhredine, Carmine Autieri, Asiyeh Shokri

High Energy Physics (Experiment)

Exact time-correlated coincidence modeling with reset boundaries

Jinjing Li

Delayed-coincidence searches identify a rare prompt-delayed signal, but their accidental background is not a simple product of marginal rates: muon vetoes, event dead time, and delayed events created before the current window condition which event sequences can be recorded. We derive exact ordered coincidence rates, within a stated stochastic model, for a recorded stream of uncorrelated prompt-like singles and correlated prompt-delayed sources subject to Poisson reset boundaries and event dead time. The calculation separates two tasks: a Markov history chain carries the delayed events still pending at reset boundaries across windows, and a current-window propagator evaluates the ordered within-window integrals in closed form with block-matrix exponentials, the matrix-analytic toolkit of applied probability. The construction extends to any prescribed finite multiplicity by increasing the block-chain depth. Here we report every ordered one-, two-, and three-fold rate formed from uncorrelated singles, correlated prompts, and recorded delayed events, together with the genuine/accidental split of prompt-delayed pairs, multiplicity efficiencies, and the aggregate rate for multiplicity four or more. For the default window-close convention, we derive a three-term a posteriori error bound for the finite pending-population truncation. An independent streaming toy Monte Carlo validates the ordered rates, two-fold time densities, matched dead-time conventions, and aggregate high multiplicity. Within the stated assumptions, the construction is exact on the retained finite state spaces and provides explicit, computable truncation-error bounds.
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Instrumentation and Detectors

Study of the intrinsic resolution of LaBr3(Ce,Sr) and NaI(Tl) crystals

Peiyi Feng, Xilei Sun, Zhenghua An et al. (+4 more)

The Gravitational wave burst high-energy Elec?tromagnetic Counterpart All-sky Monitor (GECAM) utilizes a large number of LaBr3 and NaI(Tl) crystals as sensitive materials for its gamma-ray detectors. To address the fitting issues of the energy resolution curves in the ground calibration of the GECAM detectors, this work conducts a comprehensive testing and comparative study of the energy resolution of 1-inch LaBr3(Ce,Sr) and NaI(Tl) crystals produced from the same batch. We employed a Hard X-ray Calibration Facility (HXCF), a PMT single-photoelectron calibration system, and Geant4 Monte Carlo simulation tools to quantify seven factors influencing energy resolution. The results indicate that the contributions of various components to energy resolution differ, with pho?toelectron statistical fluctuations and intrinsic resolution being predominant. For 100 keV X-rays, the total energy resolution of the LaBr3(Ce,Sr) crystal is 3.71% \pm 0.03% (expressed as 1-{\sigma}), with a contribution from photoelectron statistical fluctuations of 2.69% \pm 0.00% and an intrinsic resolution of 2.45% \pm 0.05%. For 100 keV X-rays, the total energy resolution of the NaI(Tl) crystal is 4.41% \pm 0.14% (expressed as 1-{\sigma}), with a contribution from photoelectron statistical fluctuations of 3.20% \pm 0.00% and an intrinsic resolution of 2.90% \pm 0.21%. We discussed the sources of intrinsic resolution, and the results indicate that the intrinsic resolution of the LaBr3(Ce,Sr) crystal primarily arises from luminescence non-proportionality, while that of the NaI(Tl) crystal mainly stems from fluctuations during energy transfer. This study emphasizes precise and specific experimental measurements and comparative research, demonstrating that both factors are important contributors to intrinsic resolution.
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All authors Peiyi Feng, Xilei Sun, Zhenghua An, Dali Zhang, Xinqiao Li, Shaolin Xiong, Hong Lu

Materials Science

Linear and nonlinear optical responses in the chiral multifold semimetal BeAu: A quantum-geometric perspective

Babu Baijnath Prasad and Taisuke Ozaki

Chiral topological semimetals provide a natural platform for exploring how multifold band topology and quantum geometry manifest in optical and photovoltaic responses. BeAu is a chiral multifold semimetal hosting band crossings at $\Gamma$, $M$, and $R$ with Chern numbers $C_\Gamma=-4$, $C_M=-2$, and $C_R=+4$, respectively. In this work, we study the linear optical conductivity and second-order dc photocurrent responses of BeAu using fully relativistic first-principles calculations. The calculated interband linear optical conductivity, Re $\sigma_{xx}(\omega)$, is quantitatively reproduced by $(e^2/\hbar)\omega g_{xx}(\omega)$, showing that its spectral features are governed by the photon energy factor and the variation of the photon energy-resolved quantum-metric spectral weight. The linear shift current conductivity is closely related to the symplectic connection, whereas the circular injection current susceptibility is governed by the transition-resolved product of Berry curvature and the interband group velocity difference. At the Fermi level, the linear shift current conductivity reaches approximately -810 $\mu$A/V$^2$ at a photon energy of 0.05 eV. Aligning the chemical potential with the multifold crossings strongly reshapes both responses, producing the largest linear shift current conductivity peak for $\mu=\mu_R$ and pronounced changes in the magnitude and sign of the circular injection current susceptibility. The circular photogalvanic trace is strongly photon-energy and chemical-potential dependent and does not exhibit a broad quantized plateau, indicating competing multiband transitions. Our results establish a unified quantum-geometric description of the linear and nonlinear optical responses of BeAu and identify it as a promising platform for optoelectronic phenomena governed by multifold band topology and quantum geometry.
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Atomic Physics

Comparative study of nonperturbative electron-positron pair production by intense laser fields colliding with either bremsstrahlung $\gamma$-rays or relativistic ions

S. Remme, A. B. Voitkiv, S. Villalba-Chávez et al. (+1 more)

It is well known that electron-positron pairs can be created in the strong-field environments formed by (i) a high-intensity laser field and a high-energy $\gamma$-photon (nonlinear Breit-Wheeler process) or (ii) a high-intensity laser field and a nuclear Coulomb field (nonlinear Bethe-Heitler process). Both of these processes are particularly interesting in the interaction regime where the laser field enters nonperturbatively. Various experimental collaborations are currently aiming at detecting for the first time the nonperturbative Breit-Wheeler process, by exploiting high-intensity laser pulses and $\gamma$-ray sources based on bremsstrahlung. In contrast, an experimental observation of the nonlinear, nonperturbative Bethe-Heitler process still lies further ahead in the future because its technical realization appears at present more challenging. Our comparative study shows, however, that the physical properties of the total rates for the processes (i) and (ii) can become remarkably similar when the parameters for the bremsstrahlung-driven nonperturbative Breit-Wheeler process are properly chosen. In this sense, the upcoming experiments on the nonlinear Breit-Wheeler process could also be used to closely “simulate” the currently hard to observe nonlinear Bethe-Heitler process.
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All authors S. Remme, A. B. Voitkiv, S. Villalba-Chávez, C. Müller

Materials Science

The parity gap in crystal tensor prediction

Can Polat, Mustafa Kurban, Erchin Serpedin et al. (+1 more)

Crystal symmetry dictates whether a physical response tensor must vanish, establishing a direct test for machine learning predictions independent of property calculations. We derive the parity gap, a group-theoretic metric quantifying the piezoelectric tensor freedom permitted by a crystal's proper rotation subgroup $SO(3)$ but eliminated by inversion symmetry in $O(3)$. Across state-of-the-art equivariant neural network architectures, unconstrained $SO(3)$ models systematically predict forbidden non-zero responses matching the parity gap of each centrosymmetric crystal class, while polar distortion paths dynamically map output responses to the loss of inversion symmetry. Regression controls confirm that enforcing full $O(3)$ parity incurs no consistent accuracy cost across predictive tasks. Crucially, while training interventions using explicit zero labels reduce violation magnitudes, they leave residual forbidden outputs. Exact physical compliance instead requires structural enforcement through $O(3)$ representation design or explicit output antisymmetrization. The parity gap thus provides a unified framework to distinguish empirical error reduction from exact structural compliance with physical law.
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All authors Can Polat, Mustafa Kurban, Erchin Serpedin, Hasan Kurban