Materials Science
Pronounced Site Preference in Cr-Doped Mn-Based M-Type Hexaferrites and Its Chemical Origins
Dylan Correll, Susheng Tan, Evan Wang et al. (+1 more)
Cation distribution plays a critical role in determining the properties of crystalline
oxides. Understanding the chemical factors that govern cation distribution is therefore essential for the rational design of cation-ordered materials, particularly frustrated magnets in which structural disorder can strongly affect the
magnetic ground state. Here, we investigate the origin and
evolution of cation distribution in the extensively studied M-type hexaferrite structure using the first Mn-based M-type hexaferrite, KSb3Mn9O19, as a model system. A systematic Cr3+-doped series, KSb3(Mn1-xCrx)9O19, was examined using powder and single-
crystal X-ray diffraction, electron microscopy, and energy-dispersive X-ray spectroscopy. Cr3+ exhibits a pronounced preference for the Mn Kagome sublattice, accompanied by the
evolution of Mn vacancies and Mn3+/Sb3+ disorder on neighboring sites. Analysis of the local coordination environments and their
evolution with Cr content suggests that
crystal-field effects, chemical bonding, and local structural strain collectively govern this site selectivity. The
magnetic properties of the Cr-doped compounds show similar behaviors as the undoped parent compound, other than the doping-induced
spin-glass state at the highest Cr concentration, supported by heat capacity measurements. These results establish a chemical picture of cation site distribution and selection in M-type hexaferrites and demonstrate how substitution at one crystallographic site can induce coupled redistribution and disorder across neighboring sublattices. Moreover, this work establishes local coordination chemistry as a route toward understanding and ultimately controlling cation distribution in complex
oxides, providing chemical design principles for structurally well-defined frustrated
magnetic materials.
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All authors Dylan Correll, Susheng Tan, Evan Wang, Xin Gui
High Energy Astrophysical Phenomena
Fast and furious – High-velocity features of Ca and Si in the spectra of Type Ia supernovae
Zsófia Bora, József Vinkó, J. Craig Wheeler et al. (+2 more)
High velocity absorption lines of Ca II and Si II (high-velocity features, HVFs) are common in the early spectra of Type Ia
supernovae (SNe Ia), but their physical origin is still poorly understood. We used 181 optical spectra of 56 SNe Ia that show HVFs in at least the Ca II NIR triplet to better understand the nature of HVFs. To model the profiles of HVFs we applied Gaussian fitting as well as spectrum synthesis modeling with the SYNOW code. We found that Gaussian fitting usually underestimates the velocity of HVFs compared to SYNOW, and derived a linear formula for correction. In accord with many previous studies, the observed properties of HVFs (velocity, strength, duration) were found to correlate with the general observables of SNe Ia (decline rate, spectral subtype). Brighter, slow-declining SNe usually exhibit stronger, higher velocity HVFs, while fainter objects typically show weak, low velocity HVFs. SNe Ia in early-type
galaxies showed weaker and slower HVFs compared to events in late-type
galaxies in our sample. Comparing these observational findings with theoretical predictions, we conclude that the overall physical picture of HVFs is quite complex, and could be explained by multiple models. A double detonation explosion model is promising as it is inherently capable of explaining the creation of high-velocity shells that may produce HVFs, but an asymmetric delayed detonation model or interaction with circumstellar material cannot be ruled out.
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All authors Zsófia Bora, József Vinkó, J. Craig Wheeler, Réka Könyves-Tóth, G.H. Marion
Solar and Stellar Astrophysics
Common Envelope Evolution: Too stochastic to be deterministic
Noam Soker
I argue for significant
stochastic behavior in the common envelope
evolution (CEE) of cool
giants and main-sequence companions to the degree that it is almost impossible to know the exact CEE outcome of an individual binary system from the average properties of the
stars and their initial orbit. I start with two observational properties of post-CEE planetary nebulae: many have jet-shaped morphologies, and they show a wide variety of morphologies. The first suggests that the standard CEE model should include jets, and the second shows that the CEE has a wide variety of evolutionary routes; for example, jets can be launched before, during, and/or after the main CEE phase. I show that the properties of the disk with which the main-sequence companion enters the CEE depend sensitively and stochastically on the pulsations and convection of the
giant star. Pulsations and
giant-envelope convection stochastically determine the
evolution of the
accretion disk inside the envelope. The
stochastic nature of the
accretion disk properties implies that jet power is also
stochastic. Adopting the view that jets play a major role in CEE outcomes, I conclude that the CEE outcome is
stochastic. I conclude that the CEE efficiency parameter alpha(CE) has little merit for individual systems, although it still has meaning in population synthesis and other studies of large populations.
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High Energy Physics (Phenomenology)
A Full Reproduction of the Godfrey–Isgur Relativized Quark Model
Mikhail Mikhasenko
The relativized
quark model of Godfrey and Isgur (1985) remains a reference for
meson spectroscopy four decades after its publication, yet despite its impact the calculation behind it has never been publicly available. I present an independent reproduction of the whole paper, released as the open-source Julia package GIModel.jl with companion packages for transition observables and for the comparison with the original. The published parameters are used without refitting, and the paper's three-stage harmonic-oscillator
algorithm is cross-checked with an independent finite-difference solver. All 209 levels of the paper's spectrum figures are reproduced within the precision of the printed diagrams. The strong-decay, radiative, annihilation, and electromagnetic tables are reproduced with median model-to-paper ratios between 0.97 and 1.06, and the $1P$ mixing angles agree with the values the authors revised after 1985. With the calculation open, the model's own wavefunctions become available for decay amplitudes and structure visualization. The package, its teaching material, and its
agent-accessible interface make the model a baseline for experimental questions and theoretical extensions.
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Materials Science
Chemical-Disorder-Induced Non-metallic Transport in Thermodynamically Metallic Mo4TGa16Ge (T = Co, Rh or Ir)
Chaoguo Wang, Jiaqi Tian and Xin Gui
Flat-band electronic states can be highly sensitive to chemical perturbations, offering opportunities to access a broader range of electronic behaviors beyond that of parent materials. Here, we report the discovery of a new series of compounds, Mo4TGa16Ge (T = Co, Rh, or Ir), derived from the strongly correlated flat-band
superconductor, Mo4PtGa17, via nominally preserving the total valence electron counts. All three materials crystallize in a noncentrosymmetric cubic space group, F-43m, with Ge selectively occupying one of the Ga sites in the parent compound. Although the total electron count remains the same, Mo4TGa16Ge exhibits significantly distinct properties from Mo4PtGa17. Theoretical calculations predict metallic electronic structures with narrow, dominant Mo-d states at the
Fermi energy, while low-temperature heat capacity results demonstrate finite Sommerfeld coefficients. However, electrical transport measurements show predominantly non-metallic behaviors with small observed activation energies, excluding the possibilities of conventional semiconducting behaviors. Combining chemical bonding analysis, electronic structure and compositional determination from X-ray crystallography and spectroscopy, we propose that the coexistence of the non-metallic transport features and the thermodynamically metallic behaviors can be attributed to the high sensitivity of the narrow-band materials to chemical disorders. Thus, the discovery and investigation of Mo4TGa16Ge provide a chemically tunable platform for studying disorder-controlled transport in flat-band intermetallics.
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Biological Physics · Cross-listed from q-bio.PE
Stochastic gradient descent on the epigenetic landscape: a unified framework for cellular plasticity, tumor heterogeneity, and the asymptotic irrelevance of fitness
Artur C. Fassoni
Phenotypic plasticity, the ability of
cells to switch between states, is central to development, differentiation, and therapy resistance. Although it is modeled at several scales, from compartmental ODEs to phenotype-structured PDEs and single-
cell stochastic equations, a framework connecting these descriptions is missing. We present such a framework. Starting from a general $n$-compartment ODE model encompassing nonlinear growth and linear transitions between phenotypes, we show, with a new, elementary and generalizable proof of a recent
theorem, that under uniform competition, the long-term population distribution is solely governed by transition rates. All phenotypes become selectively neutral at saturation, and the imprint of fitness differences during growth fades at an explicit rate. Restricting transitions to neighboring states transforms the model into a discretization of a phenotype-structured reaction-
diffusion-advection PDE. In this continuum model,
diffusion and advection are identified from switching rates, and fitness remains asymptotically irrelevant. Interpreting the advection velocity as the negative gradient of an effective epigenetic potential transforms the PDE into a Fokker–Planck equation and converts single-
cell trajectories into
stochastic gradient descent (SGD) in the Langevin sense on the phenotypic landscape. Non-local transitions, such as mutations, are incorporated via an integro-differential term, yielding a unified model with reaction, gradient flow,
diffusion, and jumps. State-dependent noise reshapes the effective landscape without altering the underlying potential. This gives cancer a route to elevated plasticity that static, single-
cell snapshots cannot distinguish from a changed landscape. This framework provides a physical interpretation of Waddington's landscape, where
cells perform SGD, and cancer corresponds to a corrupted landscape.
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Quantum Physics
Constant-rate quantum codes with low-weight stabilizers and full logical Clifford actions via transversal and fold-transversal gates
Takaya Matsuura, Yohji Chin, Shohei Kiryu et al. (+1 more)
Low-space-overhead fault-tolerant
quantum computation requires not only high-rate
quantum error-correcting codes but also space-efficient implementations of logical operations. Transversal and fold-transversal gates are promising since they limit error propagation and require no additional
qubits. However, the logical operations they enable are typically restricted, and a central challenge is to construct codes that combine a complete set of logical Clifford gates with favorable code parameters. In this work, we introduce a family of
quantum codes with an asymptotically constant encoding rate and sublogarithmically growing stabilizer weight, while supporting the entire logical Clifford group using only transversal and fold-transversal gates. Our construction is based on classical codes whose code spaces are absolutely irreducible Steinberg modules of their Tanner-graph
automorphism groups. Taking hypergraph products of these classical codes yields
quantum codes for which all logical Clifford operations can be synthesized from a fixed set of transversal and fold-transversal gates. Moreover, the slow growth of the stabilizer weight enables a high error-correcting performance in small instances. These results provide a path toward fault-tolerant
quantum computation with low space overhead using transversal and fold-transversal gates.
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All authors Takaya Matsuura, Yohji Chin, Shohei Kiryu, Kosuke Fukui
Mathematical Physics
Distribution of Scattering Matrix Elements in the case of Symplectic Symmetry
Nils Gluth and Thomas Guhr
Scattering theory is at the core of gaining information about most
quantum systems. In general, analytic progress is difficult and the investigation of universal features using statistical methods is of interest. Commonly this is carried out within the Heidelberg approach which models the
Hamiltonian of the target by a random
matrix. Hitherto, such investigations were performed for systems that are effectively spinless or have total angular momentum conservation. In light of recent experimental progress it has become relevant to also investigate systems with half-integer
spin. Using supersymmetry, we derive the distribution for the real and imaginary parts of the scattering
matrix elements and the corresponding cross sections in the case of
symplectic symmetry. These results complete the derivations for Dysons threefold way.
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General Relativity and Quantum Cosmology
On more general Gibbons-Hawking-York boundary terms for f(R) gravity
Federico Scali, Sergio Luigi Cacciatori, Matteo Galaverni et al. (+1 more)
More general boundary conditions are introduced - with respect to known literature - which produce a well-posed stationary action principle in $f(R)$
gravity. These conditions encompass the known cases, thus enlarging the space of admissible solutions. The corresponding Gibbons-Hawking-York boundary terms are explicitly computed and hold for any analytic f(R). The perspectives of application concerning the scalar-tensor mapping and the laws of black-hole thermodynamics are outlined in the conclusions.
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All authors Federico Scali, Sergio Luigi Cacciatori, Matteo Galaverni, Gabriele Gionti
Materials Science
Switching Anomalous Hall and Nernst Responses by Nonmagnetic N Occupation at Fixed Noncoplanar Mn Antiferromagnetic Order
Xin Liu, Jiyuan Xu, Li Ma et al. (+4 more)
Nonmagnetic atomic occupation can control anomalous transverse transport by modifying
magnetic symmetry without changing the underlying
magnetic order. We demonstrate this effect using controlled $\gamma$-Mn, Mn$_4$N, and MnN reference states with the same
lattice constant and identical noncoplanar all-in-all-out Mn
magnetic configurations, while varying only the occupation of the N sublattice. The anomalous
Hall and anomalous Nernst responses exhibit a pronounced zero–finite–zero
evolution across the series despite the unchanged Mn
spin order. In $\gamma$-Mn and MnN, the high
magnetic symmetry enforces complete cancellation of the Brillouin-zone-integrated Berry
curvature. In Mn$_4$N, N occupation lowers the
magnetic symmetry while preserving inversion and breaking the relevant twofold rotational
symmetries, thereby lifting the cancellation constraint and permitting an uncompensated Berry-
curvature contribution along the [111] direction. The resulting finite anomalous
Hall conductivity reaches $-126$~S/cm near the
Fermi level. These results establish nonmagnetic sublattice occupation as a
symmetry-control parameter for Berry-
curvature-driven transport in compensated antiferromagnets, independent of changes in the
magnetic order.
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All authors Xin Liu, Jiyuan Xu, Li Ma, Guoke Li, Dewei Zhao, Congmian Zhen, Denglu Hou
High Energy Physics (Theory)
Reconciling Inflation with the Festina Lente Bound through Affleck-Dine Baryogenesis
Kazuto Nakamura and Masaki Yamada
The Festina-Lente bound is a swampland
conjecture motivated by the behavior of charged BHs in dS spacetime, which imposes a constraint on the masses of charged particles. Although relatively weak in the present-day Universe, it can severely constrain inflation. We clarify its underlying assumptions and show that breaking all gauge
symmetries during inflation, with gauge
boson masses above the Hubble scale, provides a natural way to evade these constraints. We catalogue single flat directions in the Minimal Supersymmetric Standard Model that completely break its continuous gauge group, together with pairs that achieve complete breaking only when both directions are excited and simultaneously satisfy F- and D-flatness. With suitable lifting operators, such condensates can also generate the
baryon asymmetry through the Affleck-Dine mechanism. Within this classification, all single-direction monomials that admit complete breaking carry nonzero $B-L$, providing candidates for Affleck-Dine baryogenesis. We further show that, in this setting, a large condensate compatible with the observed
baryon asymmetry and isocurvature constraints readily satisfies the Festina-Lente bound, establishing a natural connection between the FL bound and Affleck-Dine baryogenesis.
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Quantum Physics
Integrated balanced homodyne detector using CMOS capacitive-feedback TIA for quantum measurements
Sarah Bastiaens, Cedric Bruynsteen, Simone Cammarata et al. (+5 more)
A low-noise, high-speed balanced homodyne detector is demonstrated, combining a capacitive-feedback transimpedance amplifier implemented in 28 nm CMOS with a custom photonic integrated
circuit fabricated in imec's iSiPP200 silicon photonics platform. The receiver achieves a 3-dB bandwidth of 7.6 GHz, a maximum shot noise clearance of 27 dB, a shot noise-limited bandwidth of 13.7 GHz and a common-mode rejection ratio up to 54.8 dB. These results demonstrate the suitability of CMOS capacitive-feedback transimpedance amplifiers for demanding
quantum and coherent sensing optical applications, including continuous-variable
quantum key distribution,
quantum random number generation, and optical coherence
tomography.
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All authors Sarah Bastiaens, Cedric Bruynsteen, Simone Cammarata, Axl Bomhals, Leandro da Silva, Michiel Van Osta, Johan Bauwelinck, Xin Yin
Soft Condensed Matter
Defect Organization in Coexisting Hexagonal and Square Lattices on Ellipsoids
Wenyu Liu, Han Xie, Baohui Li et al. (+2 more)
Curvature and
topology jointly organize defects in two-dimensional
crystals, but their combined role remains unresolved when competing
lattice symmetries coexist with spatially varying
curvature. We use simulated-annealing Langevin dynamics to study Hertzian particles forming coexisting hexagonal (Hex) and square (Sq)
lattices on prolate and oblate ellipsoids. Mapping reduced density and aspect ratio reveals a broad sequence of scar and domain-based morphologies in both Hex-dominant and Sq-dominant backgrounds. Latitude-resolved comparisons show that Gaussian
curvature biases defects toward its maxima under weak deformation. Strong prolateness, however, confines high
curvature to small polar caps that cannot independently accommodate all defect motifs. Defects then spread toward lower-
curvature latitudes to relieve defect crowding and elastic repulsion. In the Hex-dominant regime, this competition drives vertex-contacted domains with neutralized corner contacts, and compensating positive defects locate away from the poles. The Sq-dominant regime features Hex-rich triangular domains, bridged states, and linear or open scars similarly reorganized by
curvature anisotropy. On oblate ellipsoids, the extended equatorial high-
curvature belt allows defects to separate azimuthally while remaining
curvature-localized. This work elucidates that nonuniform
curvature can engineer rich defect patterns by selecting the spatial distribution of topological charge and the connectivity of finite defect motifs.
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All authors Wenyu Liu, Han Xie, Baohui Li, Jeff Z.Y. Chen, Yao Li
Classical Physics · Cross-listed from math.DG
A geometric rigidity estimate for codimension-1 immersions into spheres
Siran Li and Isaac Newell
We establish a quantitative stability estimate for codimension-one immersions into a round sphere. Let $(M,g)$ be an oriented Riemannian
manifold and suppose that a prescribed shape operator is realised by a smooth isometric immersion $\theta:(M,g)\to\mathbb S^{n+1}$. We prove that, on every relatively compact strongly Lipschitz domain and for every $1<p<\infty$, any Sobolev immersion $\phi$ is close to $\theta$ modulo an ambient rotation, with the $W^{1,p}$-distances between both the immersions and their Gauss maps controlled by the $L^p$ stretching-plus-bending energies of $\phi$. No a priori bounds on the fundamental forms of $\phi$ are required. The proof proceeds by extending the immersions along normal geodesics and reducing the problem to an equidimensional
geometric rigidity estimate on the sphere. A finite localisation and patching argument handles the possible non-injectivity of the normal extension of the reference immersion.
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Astrophysics of Galaxies
Thermally irreversible sulfur chemisorption on silicate grains as a major sulfur reservoir in molecular clouds
Ni-En Sie, Masashi Tsuge, Yasuhiro Oba et al. (+3 more)
Sulfur (S) chemistry in the interstellar medium remains poorly constrained due to the longstanding "missing sulfur" problem, where a significant fraction of
cosmic sulfur in molecular clouds remains unidentified. To gain a comprehensive understanding of S chemistry in the interstellar medium, its behavior on interstellar
dust grains must be clarified. Here, we experimentally investigated the surface elementary processes of S atoms under conditions mimicking interstellar molecular clouds. Our in-situ
laser-based detection method enabled the direct tracking of S atoms adsorbed on astrophysically relevant silicate substrates and amorphous solid water (ASW). We found that sulfur atoms strongly chemisorbs onto silicate surfaces and remains bound even after ASW sublimation, rendering it observationally invisible. An astrochemical model coupled with these results suggests that at least 10 percent of the total sulfur budget in molecular clouds must be locked onto silicate
dust grains. Our results identify sulfur chemisorption on silicate as a key mechanism driving sulfur depletion and provide a physical explanation for the missing sulfur problem.
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All authors Ni-En Sie, Masashi Tsuge, Yasuhiro Oba, Germán Molpeceres, Kenji Furuya, Naoki Watanabe
High Energy Physics (Phenomenology)
A glueball puzzle explained in terms of $\phi h_1(1380)$ dynamics: Aka $X(2370)$
K. P. Khemchandani, A. Martinez Torres and E. Oset
We study the interaction of $\phi$ with $h_1(1380)$, considering the latter as a $K^*\bar K$ molecular state, and find the generation of a state with the same
quantum numbers, together with a mass and width compatible with the experimental results, as those of $X(2370)$, recently advocated as a candidate for a glueball. Within our description, the suppressed decay modes of $X(2370)$ to $\gamma \omega$, $\omega \phi$ and $K^*\bar K$, reported in the experimental paper as clues to its glueball nature, are naturally explained. Conversely, the non $K^* \bar K$ decay to $K \bar K \pi$ (the latter being the invariant mass where the resonance is observed) is shown to be largely enhanced due to the combination of a triangle singularity and the presence of $K(1630)$ in the $\rho \phi \to \bar K$ vertex involved in the triangle loop.
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High Energy Physics (Phenomenology)
Bound-state decay of a charged scalar particle in an external Coulomb field
Andrzej Czarnecki and Artem O. Davydov
We determine the decay rate $\Gamma$ of a scalar particle bound to a light
nucleus, numerically and analytically. As a model system, we consider a negatively charged kaon in the ground state of a hydrogen-like ion decaying into charged and neutral scalar pions, $K^-\to \pi^-\pi^0$. All particles are assumed point-like; the
nucleus is infinitely heavy. The partial wave expansion converges slowly, as in a recent analysis of the bound-
muon decay. To overcome this difficulty, we introduce a subtraction method: the free $\pi^-$ contribution is evaluated separately, while the partial-wave sum is used only for the Coulomb distortion. The ratio of bound-to-free decay rates, $\Gamma/\Gamma_0$, is found for light
nuclei, $1\leq Z\leq 10$. The numerical calculation is complemented by a diagrammatic small-$\alpha Z$ expansion. We find $ \Gamma/\Gamma_0 = 1-(\alpha Z)^2/2 + 17(\alpha Z)^4/24 +\mathcal{O}((\alpha Z)^5)$, in agreement with the all-orders numerical calculation at low $Z$.
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High Energy Astrophysical Phenomena
X-ray measurements of the elemental abundances for the diffuse emission in the nuclear starburst galaxy NGC 3079
Jiejia Liu, Junjie Mao, Shuinai Zhang et al. (+3 more)
Outflows driven by feedback leave imprints on a
galaxy's diffuse X-ray emission. Elemental abundances provide key diagnostics of feedback-driven chemical enrichment. We present a spectroscopic study of the diffuse X-ray emission in NGC 3079 using XMM-Newton RGS and EPIC, focusing on the
nuclear region and the extended
galactic-scale superbubble (GSB). We analyzed the high-resolution RGS spectrum of the central $\sim4~\rm kpc$ region, encompassing the $\sim1~\rm kpc$
nuclear superbubble (NSB), and the EPIC spectrum of the GSB out to $5'~(\sim25~\rm kpc)$. The
nuclear spectrum is best described by a multi-temperature thermal-
plasma model plus a charge-exchange (CX) component, which contributes approximately $13\%$ of the total observed energy flux in the $0.2-2~\rm keV$ band. The best-fit O/Fe and Ne/Fe ratios are $0.47$ and $0.77$ in
solar units. Comparing these ratios with IMF-weighted core-collapse
supernova (SNcc) yields gives an upper progenitor-mass cutoff of $M_{\rm u}\simeq13-15~M_{\odot}$ for pure SNcc enrichment. For the best-fit spectral model, including an SNIa contribution increases the inferred cutoff, but its $1\sigma$ upper limit remains below $25~M_\odot$ for SNIa fractions up to $10\%$ within the adopted yield models. The characteristic ages of the NSB and GSB are $0.92^{+0.39}_{-0.46}~\rm Myr$ and $29.6^{+1.6}_{-2.9}~\rm Myr$, respectively, suggesting episodic feedback in NGC 3079.
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All authors Jiejia Liu, Junjie Mao, Shuinai Zhang, Guan-Fu Liu, Rui Huang, Wei Cui
Atomic Physics
All-optical switching in a trapped ion cavity QED system: a comparative study
Abhijit Kundu, Vijay Bhatt and Arijit Sharma
We investigate the transient dynamics of cavity-EIT-based all-optical switching in a system of trapped ions coupled to an optical cavity through numerical simulations. In contrast to steady-state analysis, the time-dependent response provides direct insight into the switching speed, transient dynamics, and achievable switching contrast. We consider three distinct switching schemes and systematically compare their performance as a function of the relevant system parameters. The switching contrast is evaluated from the time-dependent cavity output and used to characterize the performance of each scheme. For the four-level N-type system, we find distinct trade-offs between switching through suppression of the cavity-EIT signal and switching through resonance shifting, with the former exhibiting a faster temporal response. The corresponding three-level scheme can achieve near-unity switching contrast with substantially shorter switching pulses, although it does not provide an independent switching control field. These results establish the performance limits and trade-offs of different cavity-EIT-based switching schemes and provide guidelines for optimizing their operation for applications such as high-speed optical gating, frequency-selective
photon routing, frequency-multiplexed
quantum communication, etc.
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Applied Physics
PIN-Diode-Controlled X-/Ku-Band Frequency Reconfiguration of a CPW-Fed Quasi-Yagi Antenna
Huijuan Niu, Mengyu Dong, Yuanhao Li et al. (+9 more)
A PIN-diode-reconfigurable quasi-Yagi
antenna fed by a coplanar waveguide (CPW) is presented for X-band and Ku-band frequency reconfiguration. PIN diodes are strategically introduced between the driven and parasitic elements to control the effective surface-current paths and thereby modify the operating frequency characteristics. By optimizing the diode locations, number, and switching states, two distinct operating modes are achieved. In Mode I, dual-band operation covering the X-band and Ku-band is obtained, with simulated impedance bandwidths of 9-11 GHz and 12.2-18.8 GHz. In Mode II, a simulated continuous impedance bandwidth from 10 to 14.2 GHz is achieved. The corresponding simulated peak gains are approximately 8 and 7 dBi for Mode I and Mode II, respectively. A prototype is fabricated and experimentally characterized in terms of its S-parameters, and the measured results confirm the frequency-reconfiguration behavior of the proposed
antenna. The effects of the number and placement of the PIN diodes on the impedance characteristics are further investigated to clarify their roles in frequency reconfiguration and design complexity. The proposed
antenna provides a compact CPW-fed quasi-Yagi configuration with PIN-controlled X-band and Ku-band frequency reconfiguration.
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All authors Huijuan Niu, Mengyu Dong, Yuanhao Li, Bin Shao, Qingtao Chen, Junqiang Zhang, Jiawei Tao, Zhenzhong Chen, Gaoming Xu, Gongqing Li, Yongqing Huang, Chenglin Bai
Atomic Physics
Shortcut to Adiabatic Transfer in a Four-Level N-type System using Counterdiabatic Driving
Marius Romuald Kamsap, Simon Evehe Ndong, Maïk Delon Mboumba et al. (+5 more)
The stimulated Raman shortcut-to-adiabatic passage (STIRSAP) technique has been demonstrated to accelerate adiabatic population transfer processes. Traditionally applied to three-level atomic systems, this method enables rapid and efficient population transfer in a short interaction time. In this work, we extend this approach to a four-level N -type system driven by three
laser fields. Under the three-
photon phase matching condition, the first-order Doppler effect can be completely eliminated, making this configuration more suitable for applications in frequency metrology and
quantum information processing. By adiabatically eliminating the intermediate state, the four-level system is effectively reduced to a two-level model, enabling the application of counterdiabatic driving without requiring additional couplings. This approach allows for fast and efficient population transfer between metastable states. We analyze the influence of
laser intensity peaks and detuning, and we show that the transfer time is significantly shorter than that achieved with the STIRAP technique. Moreover, we also show 1 that an optimal coupling strength between the ground and metastable states further minimizes the operation time.
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All authors Marius Romuald Kamsap, Simon Evehe Ndong, Maïk Delon Mboumba, Mathurin Esouague Ateuafack, Christian Kenfack-Sadem, Thierry Blanchard Ekogo, Alain-Brice Moubissi, Caroline Champenois
Physics and Society
Statistical Physics of Fish Collective Motion
Elena G. de Lamo, M. C. Miguel and R. Pastor-Satorras
We review recent theoretical and empirical advances that recast fish schooling within a statistical-physics framework, emphasizing how heterogeneous and time-dependent interactions govern collective motion. Building on extensions of Vicsek-type models to complex and weighted social networks, we show that
topology and link strength qualitatively alter flocking stability and critical thresholds, with empirical weights typically reducing global
alignment. High-resolution trajectory inference reveals selective, nonreciprocal responses: individuals preferentially attend to faster neighbors, producing transient, speed-induced leadership rather than fixed hierarchies. At the mesoscopic scale, schools exhibit avalanche-like turning cascades with scale-free size and duration statistics, aftershock clustering, and an Omori-type temporal decay with a short
memory. Together, these findings support a unified picture in which collective order and critical-like fluctuations coexist:
alignment provides stability while near-critical variability preserves responsiveness. This synthesis highlights fish schools as a tractable experimental model for how living collectives organize, transmit and process information across scales.
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Quantum Physics
Resonance Breaking in Noisy Shor's Algorithm
Zhengwei Liu
We argue that the exponential
quantum advantage in Shor's
algorithm is broken under one-layer depolarizing noise of arbitrary small error rate, by analyzing a resonance breaking phenomenon in noisy
quantum circuits. First, we express the distribution of measurements on $n$-
qubit strings as the superposition of the $4^n$ wave functions in the Pauli path integral. In the noiseless case, the bit-strings achieving resonant peaks guaranteed a constant rate of successful measurements to factor a large number. Secondly, when the middle layer of the
quantum circuit has independent depolarizing noise of rate $\lambda$, for any Hamming weight $d$, we obtain corresponding measurement rate bounded by $2(1-\lambda)^d$ for higher frequency terms and by $O(n^d)/2^{n/2}$ for low frequency terms. The rate approaches to zero as $n$ and $d$ approaches to infinity. Resonance breaking destroys the exponential
quantum advantage. Furthermore, we design a classical factoring
algorithm in
polynomial time $O(n^d)$ to substitute the low frequency contribution.
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Quantum Physics
Adaptive decoding of quantum LDPC codes through decoder disagreement
Maida Wang and Peter V. Coveney
Accurate decoding of
quantum low-density parity-check (qLDPC) codes often relies on expensive post-processing search, although decoding difficulty varies strongly between syndromes. We find that the benefit of deeper post-processing search is highly concentrated in a small subset of decoding instances, and that these instances can be identified directly from the decoder itself. To this end, we introduce an adaptive decoder based on belief propagation (BP) and ordered-statistics decoding (OSD), using the disagreement between the BP hard decision and the syndrome-consistent order-zero OSD solution as an internal risk signal to determine where deeper search is required. On a $[[144,12,12]]$ bivariate bicycle code under
circuit-level depolarising noise, encoding $12$ logical
qubits in $144$ data
qubits with distance $12$, escalating only the highest-risk $20\%$ of instances recovers $85\%$ to $92\%$ of the improvement in logical error rate available from a full one-free-variable sweep, while reducing the mean serial decoding cost by a factor of $3.6$ relative to applying the same truncated search to every instance. At matched budget, disagreement-guided routing also outperforms routing based on the BP syndrome residual, syndrome weight and random selection. The same behaviour reappears on a structurally distinct radial qLDPC code obtained from a lifted-product construction, where escalating $20\%$ of instances recovers $87\%$ to $94\%$ of the available gain. A $Z$-
memory experiment on the Quantinuum H2 trapped-ion processor, implementing both $X$-type and $Z$-type checks, further shows that the signal remains predictive under device noise. These results show that decoder-internal disagreement can expose where additional decoding effort is valuable, allowing classical computation to be concentrated on the instances most likely to benefit from it.
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Quantum Physics
Operational theory for photonic circuits: generalizing linear optics beyond quantum theory
Ismaël Septembre, Matthias Kleinmann and Martin Plávala
We use the analogy between the quadrature operators in
quantum optics and the phase-space coordinates in a mechanical harmonic oscillator to generalise the theory of linear optics beyond
quantum theory. For this, we introduce a framework for analysing photonic
circuits within generalised probabilistic theories based on quadrature operators. Using this framework, we ask whether phenomena like the Hong-Ou-Mandel effect, Mach-Zehnder interferometry are specific to
quantum theory or also occur across a broader class of theories. We find the latter: the vanishing
photon coincidences at the output of a beam splitter also occur for classical light and for a modified version of quantised light. Similarly, for Mach-Zehnder interferometry we find that there is no qualitative difference between
quantum theory and these alternative theories. Our framework can serve as a foundation to study generalised theories of complex photonic set-ups and photonic
quantum computers.
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Astrophysics of Galaxies
GA-NIFS: sRMS, a new method for disentangling resolved and unresolved emission in integral field spectroscopy. Application to distant quasars
Michele Perna, Santiago Arribas, Carlota Prieto-Jiménez et al. (+28 more)
The interpretation of AGN emission-line profiles in type1 AGN is often complicated by the dominance of bright, spatially unresolved
nuclear continuum and broad-line region (BLR) emission over narrower and blended components from the narrow-line region (NLR) and the host
galaxy. This remains challenging even with integral-field spectroscopy (IFS), as the relevant spatial variations can occur on scales smaller than the angular resolution, particularly in the compact host of distant AGN. We introduce the spatial root-mean-square (sRMS) technique, a new approach to analyse single-epoch IFS that uses the spatial variance of spectra extracted from partially overlapping apertures to isolate off-
nuclear emission of high-z BL-AGN, and investigate whether the resulting kinematic information can improve the decomposition of their integrated spectra. We construct sRMS spectra from ensembles of overlapping apertures centred on the unresolved
nucleus. Emission that is spatially invariant on the scales probed by the apertures is consequently suppressed, whereas spatially varying emission is retained. We apply the procedure to JWST/NIRSpec data of two z~6.5 QSOs. We model the resulting sRMS spectra with multiple Gaussian components to determine the kinematics of the spatially varying emission, and use these kinematic constraints to model the integrated spectra. The sRMS technique identifies spatially varying narrow-line emission on scales up to ~5x smaller than the NIRSpec PSF and provides robust constraints on the kinematics of individual kinematic components. Imposing these kinematic constraints on the integrated-spectrum fit reduces significantly the degeneracy of multi-component decompositions. Simulations further demonstrate the potential of the method to detect spatially offset BLR emission from close dual BL-AGN, down to projected separations of ~200 pc at z~6.5 for a BLR flux ratio of ~10.
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All authors Michele Perna, Santiago Arribas, Carlota Prieto-Jiménez, Isabella Lamperti, Lorenzo Ulivi, Hannah Übler, Giovanni Cresci, Bruno Rodríguez Del Pino, Torsten Böker, Andrew J. Bunker, Stéphane Charlot, Roberto Maiolino, Chris J. Willott, Ivan Delvecchio, Elena Bertola, Madeline A. Marshall, Eleonora Parlanti, Pablo G. Pérez-González, Giacomo Venturi, Sandra Zamora, Filippo Mannucci, Quirino D'Amato, Alessandra De Rosa, Ismael García-Bernete, Alessandro Marconi, Miguel Pereira-Santaella, Fabio Rigamonti, Martina Scialpi, Paola Severgnini, Cristian Vignali, Maria Vittoria Zanchettin
Medical Physics
Using a radiopharmaceutical production cyclotron for radiobiological research
Eva Kasanda, Jan Gruber, Pierluigi Casolaro et al. (+8 more)
The Laboratory for High Energy Physics and the Institute of Anatomy at the University of Bern are establishing a pre-clinical
proton therapy research facility at the Bern University Hospital (Inselspital). The facility centers on the Bern Medical Cyclotron, an 18 MeV compact cyclotron designed for microampere-range beam currents for radioisotope production. The Bern Medical Cyclotron can be adapted as a highly accessible and customizable platform for pre-clinical
proton therapy research, enabling advanced modalities such as ultra-high dose rate (FLASH) radiotherapy and spatially fractionated radiation therapy. Human keratinocytes (HaCaT) and mouse melanoma (B16-F10)
cell lines were irradiated with 8.14(29) MeV
protons at conventional dose rates and with 225 kV X-rays at doses from 0 to 8 Gy. Clonogenic survival assays were analyzed using the linear-quadratic model, and relative biological effectiveness values were derived by comparing the
proton and X-ray doses required for 0.1 survival.
Proton irradiation yielded steeper survival curves than X-rays, indicating higher cytotoxicity. B16-F10
cells were most sensitive, with a relative biological effectiveness of 1.34 at 0.1 survival, while HaCaT
cells showed a relative biological effectiveness of 1.21. These results confirm enhanced
proton effectiveness in
cell killing and demonstrate that the Bern Medical Cyclotron provides a reliable platform for radiobiological studies. Establishing in vitro
proton irradiation capability marks a key milestone toward developing a comprehensive pre-clinical radiobiology research facility in Bern. Ongoing upgrades will further refine dosimetry and
proton delivery, paving the way for future FLASH and
proton spatially fractionated radiation therapy studies.
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All authors Eva Kasanda, Jan Gruber, Pierluigi Casolaro, Lars Eggimann, Alexander Gottstein, Isidre Mateu, Paolo Pellicioli, Maria Vittoria Rossi, Paola Scampoli, Cristian Fernandez-Palomo, Saverio Braccini
Quantum Physics
Optimal interferometric certification of multi-photon indistinguishability
Marco Robbio, Michał Oszmaniec, Nicolas J. Cerf et al. (+2 more)
Multiphoton indistinguishability is a key resource for photonic
quantum technologies, yet its characterization typically relies on resource-intensive methods. In this work, we develop two efficient and experimentally friendly protocols to estimate or bound the fidelity $F_{\mathrm{ind}}$ of an $N$-
photon state to the closest perfectly indistinguishable state. The first protocol applies to sources preparing separable states, uses a single
Fourier interferometer together with
photon-number-resolving detection, and yields tight two-sided bounds on $F_{\mathrm{ind}}$. The second protocol combines randomized implementations of linear-optical interferometers with
photon counting, enabling direct estimation of $F_{\mathrm{ind}}$ for arbitrary $N$-
photon states. Both protocols can certify $F_{\mathrm{ind}} = 1 - \mathcal{O}(\epsilon)$ using provably optimal $\mathcal{O}(1/\epsilon)$ samples, in contrast to previous approaches which required prior assumptions on the model of partial distinguishability. Our methods, based on a multiphoton generalization of the Hong-Ou-Mandel test, bring the rigorous and operationally meaningful certification of multiphoton indistinguishability within reach of current photonic technologies.
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All authors Marco Robbio, Michał Oszmaniec, Nicolas J. Cerf, Ernesto Galvão, Leonardo Novo
Optics
Optical enhancement cavities operated at GHz repetition rate in burst mode regime
Kevin Dupraz, Frédéric Blanc, Ronic Chiche et al. (+7 more)
The design and experimental validation of a burst-mode optical cavity tailored for inverse Compton scattering X-ray sources is presented. The system is tailored for a room temperature linear accelerator operating at 880 MHz and utilizes a common-path injection scheme for both locking and burst
laser pulses to optimize stability and simplicity. We detail the cavity construction, the
laser system, and performance under two enhancement cavity finesse regimes (2000 and 7300), highlighting the sensitivity of cavity filling to carrier-envelope offset parameters. A theoretical model is developed to explain observed power dynamics and to guide optimization for high-energy storage. Our findings demonstrate reliable storage exceeding 300 mJ over 20 minutes, paving the way toward compact, high-flux inverse Compton scattering X-ray sources.
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All authors Kevin Dupraz, Frédéric Blanc, Ronic Chiche, Aurélien Martens, Antoine Courjaud, Loïc Amoudry, Titouan Le Barillec, Daniele Nutarelli, Yann Peinaud, Fabian Zomer
Mathematical Physics · Cross-listed from math.NT
On minima of theta and Epstein zeta functions in dimension four
Senping Luo and Juncheng Wei
Let the theta and Epstein
zeta functions be $\Theta(\alpha,L)=\sum_{v\in L}e^{-\pi\alpha|v|^2}$ for $\alpha>0$ and $E(L,s)=\sum_{v\in L\setminus\{0\}}{|v|^{-2s}}$ for $s>2$, respectively. We consider full-rank
lattices $L\subset\mathbb R^4$. Let the covolume of $L$ be one, and let $\mathcal D_4=2^{-1/4}D_4$ be the root
lattice $D_4$ rescaled to covolume one. We prove that, up to orthogonal transformations, \begin{equation}\nonumber arg\,min_{covol(L)=1}\Theta(\alpha,L)=\mathcal D_4 \qquad\text{if}\quad \alpha>0, \end{equation} and this implies that \begin{equation}\nonumber arg\,min_{covol(L)=1}E(L,s)=\mathcal D_4 \qquad\text{if}\quad s>2. \end{equation} This proves that the root
lattice minimizes the theta and Epstein
zeta functions among all
lattices in dimension four, as conjectured by Sarnak-Strömbergsson (\cite{SS}, 2006), who established the local minimality of $\mathcal D_4$. Thereby, this resolves the Rankin-Sobolev problem in dimension four dating back to Éndibaev (\cite{End1978}, 1978) and Shushbaev (\cite{Shu1978}, 1978).
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