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Friday 5 June

Quantum Physics

Continuous-time quantum control across an exponentially small bottleneck in a frustrated Ising ring model

Vincenzo Roberto Arezzo, Kiran Thengil and Giuseppe Santoro

Continuous-time Quantum Annealing (QA) is a strategy for preparing the ground state of nontrivial many-body systems. In its standard form, the dynamics is generated by a time-dependent interpolation between a simple driving Hamiltonian and the target problem Hamiltonian, usually implemented through a linear schedule. This approach faces the crucial bottleneck of small spectral gaps, which may require exponentially long annealing times to ensure adiabaticity. Here, we show how to implement quantum control over the annealing schedule in a frustrated Ising ring, one of the simplest models exhibiting an exponentially small bottleneck gap. By optimizing smooth continuous-time annealing schedules with a dressed-CRAB approach, and using a digitized representation of the dynamics to efficiently evaluate gradients, we construct protocols that strongly outperform standard fixed schedules. The optimized dynamics bypasses the bottleneck through a strongly nonadiabatic mechanism, leading to efficient ground-state preparation despite the exponentially small minimum gap. In particular, the annealing time required to reach a fixed residual-energy threshold is found to grow linearly with system size rather than exponentially. We further examine a lowest-order variational counter-diabatic correction and find that, once schedule optimization is allowed, it does not lead to any improvement.
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Geophysics

Implicit Structural Modeling via Generative Diffusion Frameworks

Yimin Dou, Xinming Wu, Zhixiang Guo et al. (+2 more)

Implicit structural modeling can support understanding subsurface spatial configurations, revealing patterns of geological evolution, and enabling quantitative simulation of geological processes, thereby offering substantial scientific and engineering value. Conventional approaches formulate it as an optimization problem or framework interpolation to fit a continuous scalar field, whereas machine learning methods typically adopt discriminative regression to directly predict implicit models. However, in complex scenarios involving fault intersections, branching, and thrust nappes, these methods still struggle to maintain topological consistency and kinematic plausibility. In this work, we develop an implicit structural modeling approach based on diffusion models. We construct a set of training data through a simulation based synthesis pipeline and design a dedicated encoder for conditional injection, allowing the conditional branch to converge rapidly while effectively reinforcing the input conditional priors throughout the diffusion process, thereby more stably propagating structural constraints. We then inject these conditional features into a backbone network pretrained on large scale natural images to enable conditional training of the diffusion model. Although our synthetic data include only a relatively stylized normal fault system, experiments demonstrate strong generalization, enabling the model to effectively handle diverse complex structural types such as strike slip faults and intricate flower fault systems. More importantly, even in challenging thrust nappe settings where the scalar field becomes non monotonic and exhibits abrupt depth discontinuities, the model can still generate reliable implicit structural models.
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All authors Yimin Dou, Xinming Wu, Zhixiang Guo, Hui Gao, Buyu Deng

Astrophysics of Galaxies

Angular momentum evolution in the CIELO simulations. I. Temporal evolution of gas-stellar misalignments and baryonic merger timing

Catalina Casanueva-Villarreal, Patricia B. Tissera, Nelson Padilla et al. (+4 more)

Gas-stellar kinematic misalignments trace how galaxies assemble and reorient their angular momentum. Although well documented locally, their continuous evolution remains largely unexplored. We aim to characterise the pathways linking aligned, misaligned, and counter-rotating phases, assessing how gas accretion channels and mergers drive reorientation. We analysed 44 central galaxies from the CIELO simulations from z=3.5 to z=0. We defined kinematic episodes using the intrinsic angle, psi, between the star-forming (SF) gas and stellar angular momentum vectors, interpreting these histories by tracking accreted gas origins and evaluating paired statistical contrasts. Nearly 80% of the simulated galaxies are aligned at z=0, yet 86% experience at least one non-aligned episode. Although 19% of non-aligned episodes last >2 Gyr, their durations do not differ significantly from aligned episodes. Abrupt changes in psi coincide with intervals where accreted gas dominates the pre-existing SF reservoir and is highly tilted relative to pre-existing stars. During transitions, the median mass ratio of accreted to pre-existing SF gas rises from 0.57 to 2.14, and the median angular offset increases from 21.2 to 64.6 deg. While relevant mergers cluster near these boundaries, they can drive either alignment or misalignment regardless of mass ratios or orbits. Instead, mergers triggering abrupt transitions typically encounter hosts that are already partially decoupled. In the simulated sample, gas-stellar misalignment is fundamentally driven by reservoir competition. Mergers act as conditional triggers, but a galaxy's ultimate kinematic fate depends strictly on how newly accreted gas couples to, replaces, or mixes with the pre-existing material as it joins the central SF reservoir.
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All authors Catalina Casanueva-Villarreal, Patricia B. Tissera, Nelson Padilla, Lucas Bignone, Jenny Gonzalez-Jara, Brian Tapia-Contreras, Susana Pedrosa

Instrumentation and Methods for Astrophysics

Second-Generation Fabry-Pérot Unit for CARMENES

Hanna Lina Pleteit, Michael Debus, Sebastian Schäfer et al. (+1 more)

CARMENES consists of two high-resolution spectrographs located at the Calar Alto 3.5m telescope, covering the wavelength range from 520nm to 1710 nm. The original Fabry-Perot (FP) units have been essential to track and remove instrumental drift while also improving the wavelength solution provided by the hollow cathode lamps. In this paper we present the second-generation FP unit that has begun operation at Calar Alto in April 2024. It features drastically improved temperature stabilization, additional temperature monitoring, and enhanced optomechanics. Temperature stabilization is improved through better vacuum vessel design, thermal shielding and improved thermal control. The temperature is now monitored with Pt-100 sensors inside the vacuum vessel, one of which is used to drive the temperature control. The new purpose-built optomechanics allow for an improved alignment procedure leading to higher line contrast. The etalon coatings now cover a broader wavelength range, the optics have been upgraded, and the fibers have been updated to an octagonal shape. In laboratory measurements with a Fourier transform spectrometer we compare the FP radial velocity (RV) drift to that of an iodine cell. In a two hour binning we achieve an RMS of the differential RVs of 6cm/s. The new FP unit has already been successfully integrated at CARMENES, with first calibration data indicating improved RV precision.
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All authors Hanna Lina Pleteit, Michael Debus, Sebastian Schäfer, Ansgar Reiners

Plasma Physics

Multi-kilohertz laser plasma acceleration driven by an industrial-grade Yb:YAG laser

Bonaventura Farace, Nikita Khodakovskiy, Rob Shalloo et al. (+10 more)

Laser plasma accelerators (LPAs) are a promising platform for compact radiation sources. For a wide range of applications, including radiotherapy, ultrafast electron diffraction and time-resolved imaging, stable operation at high repetition rates is essential in order to deliver competitive average particle flux. Here we demonstrate the first LPA driven by an industrial-grade ytterbium-doped yttrium aluminium garnet (Yb:YAG) laser, designed for high-average-power operation. The picosecond laser pulses are post-compressed in a multi-pass cell to 50 fs duration and used to drive the interaction. The electron accelerator is operated in burst mode, at repetition rates tuneable from 0.625 to 6.25 kHz, representing a substantial increase compared to the state-of-the-art. Across this range, the electron beam properties remain unchanged, with average charges of 10-12 pC per shot, divergences of 50-70 mrad, and Maxwellian-like spectra extending to a few MeV. Numerical simulations capture the key features of the experimental observations and indicate acceleration in the self-modulated regime, enabled by relativistic self-focusing in near-critical-density plasma. Combining industrial high-average-power laser technology with plasma-based acceleration, these results represent a key step toward scalable, compact high-repetition-rate electron sources for medical, imaging and industrial applications.
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All authors Bonaventura Farace, Nikita Khodakovskiy, Rob Shalloo, Tae Gyu Pak, Esmerando Escoto, Supriya Rajhans, Arthur Schönberg, Ingmar Hartl, Jens Osterhoff, Christoph Heyl, Andreas Maier, Kristjan Põder, Wim Leemans

Earth and Planetary Astrophysics

Freo Doctor: Atmospheric Modelling for Meteorite Falls and Spacecraft Re-Entries

Hadrien Devillepoix and Martin Cupák

How much does the wind affect the path of meteorite falls? We finely model the lower ~30 km of the atmosphere using Weather Research and Forecasting open source tools at 1 km spatial resolution. Models initialised at different times give different results, which can be used as a proxy for uncertainty. We find that in most cases the differences on the ground positions are significant: median shift for a 1 kg meteorite is 143 m, doubling to 307 m for a 10 g rock, though these vary by over an order of magnitude between events. The differences wind model choice makes on the ground are significantly larger than the typical uncertainty on meteoroid state vector obtained from bright flight observations of the fireball (<100 m), and should be taken into account when predicting meteorite free-fall path to the ground. Unsurprisingly the cases where we see the largest differences coincide with documented extreme weather events. We also find that high spatial resolution models (1 vs. 3 km) tend to perform better. We have successfully used these models to guide field teams to the location of 12 fallen meteorites after fireball observations. We release as open data 1107 models we have calculated for 302 meteorite fall events and spacecraft re-entries around the world.
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Quantum Physics

Improved Cryogenic Photodiode Optical Biasing for Low-Noise and Low-Jitter Superconducting Nanowire Single-Photon Detectors

Jia-Hao Hu, Wei-Jun Zhang, Wen-Shuo Yu et al. (+7 more)

We experimentally demonstrate an improved optical biasing scheme for superconducting nanowire single-photon detectors (SNSPDs), which employs a cryogenic InGaAs-InP photodiode (PD) as a local bias source. It is found that, under illumination from a stable external light source, this PD generates a stable photocurrent in a cryogenic environment (~2.3 K), with fluctuations in the photocurrent primarily attributed to fluctuations in the incident optical power. Furthermore, by screening and effectively blocking stray photons leaking from the PD, which give rise to background dark counts, we have achieved an SNSPD exhibiting an ultra-low intrinsic dark count rate of 1e-4 cps. Utilizing this improved optical biasing technique, our SNSPD achieved performance comparable to that obtained under conventional electrical biasing: a system detection efficiency of 80.7%, a background dark count rate of 32.6 cps, and a minimum timing jitter of 57.5 ps. These results indicate that cryogenic-PD-based optical biasing serves as a viable, low-noise, and low-jitter alternative to traditional electrical biasing. Moreover, this work offers useful design guidance for the future development of PD-based low-noise bias sources and for the construction of all-photonic SNSPD systems tailored for high-precision quantum photonics applications.
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All authors Jia-Hao Hu, Wei-Jun Zhang, Wen-Shuo Yu, Yu-Ze Wang, Dong-Wei Chu, Ya-Tao Peng, Hui-Qin Yu, Pu-Sheng Yuan, Ling Wu, Li-Xing You

Materials Science

Chromium chalcohalide Janus monolayer ferromagnets with perpendicular magnetic anisotropy and high Curie temperature

M. Bosnar, J.M. Lendinez, A.Yu. Vyazovskaya et al. (+8 more)

Using density functional theory, we revisit the magnetic properties of a recently proposed family of noncentrosymmetric two-dimensional magnetic materials, chromium chalcohalide monolayers, CrXY (X=S, Se, Te; Y=Cl, Br, I). These systems consist of three atomic planes stacked in the X-Cr-Y sequence, which breaks inversion symmetry, giving rise to their designation as "Janus" monolayers. We consider both 1T and 1H structural polymorphs of CrXY. Among the two polymorphs, the 1T phase is consistently more favorable, with energy gains exceeding 0.55 eV per formula unit. Our total-energy calculations reveal that all dynamically stable CrXY monolayers exhibit ferromagnetic coupling. However, robust out-of-plane magnetic anisotropy is observed only in the CrSI and CrSeI compositions, for both 1T and 1H structures. The perpendicular magnetic anisotropy results from a constructive interplay between single-ion and anisotropic exchange contributions that overcome the dipole-dipole interaction. We further quantify the Dzyaloshinskii-Moriya interaction (DMI) in CrSI and CrSeI for both polymorphs, and reveal a weak-to-moderate DMI strength as compared to the isotropic exchange interaction term. Finally, for systems exhibiting ferromagnetic coupling and perpendicular magnetic anisotropy, the exchange and anisotropy parameters derived from density functional theory calculations are employed as inputs for large-scale atomistic spin dynamics simulations to probe the temperature evolution of real-space magnetic structures. The calculated Curie temperatures are at least 210 K for 1T-CrSI, 235-260 K for 1H-CrSeI, and 370-410 K for 1H-CrSI. In contrast, the sizable DMI in 1T-CrSeI results in a worm-like domain ground state at zero external field and enables the stabilization of skyrmions under a perpendicular magnetic field.
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All authors M. Bosnar, J.M. Lendinez, A.Yu. Vyazovskaya, I.Yu. Sklyadneva, R. Heid, S. V. Eremeev, U. Atxitia, S. Gallego, E.V. Chulkov, A. Arnau, M.M. Otrokov

Strongly Correlated Electrons

Inverse Melting of 3D Antiferromagnetic Order in Multi-sublattice Magnetic Perovskites

Bangye Qin, Dmitry D. Khalyavin, Ran Liu et al. (+3 more)

In conventional antiferromagnets a long-range ordered 3D ground state transitions to a disordered paramagnetic state on warming, often via lower dimensional spin correlations within the critical regime. Here we demonstrate a striking departure from this paradigm. Through analysis of neutron powder diffraction data, we show that the magnetic ground state of columnar-ordered quadruple perovskites, Na$R$Mn$_2$Ti$_4$O$_{12}$ ($R$ = Dy, Sm), lacks long-range order, hosting only 2D spin correlations. On warming, this disordered state transitions into a 3D long-range ordered antiferromagnetic structure prior to the phase transition to the paramagnetic state. Our results establish an unconventional order-by-heating mechanism in which intrinsic A-site chemical disorder is coupled to competing exchange interactions between the rare earth and Mn sub-lattices, leading to a novel type of magnetic phase transition.
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All authors Bangye Qin, Dmitry D. Khalyavin, Ran Liu, Kazunari Yamaura, Alexei A. Belik, Roger D. Johnson

Soft Condensed Matter

Enhanced viscous adhesion using deformable structure

Mary Williams, Thomas Desmedt, Fabian Brau et al. (+1 more)

We investigate the adhesion dynamics of a thin elastic structure in contact with a viscous fluid and retracted at a controlled speed, mimicking natural adhesion mechanisms. During detachment, the viscous fluid confined between the deformable structure and a rigid substrate generates an adhesive force due to a pressure drop within the thin film. We show from dedicated experiments that the structural flexibility introduces a strongly nonlinear mechanical response, which significantly alters both the magnitude and the evolution of the adhesion force with retraction velocity. In contrast to rigid systems, the deformability of the structure enables enhanced and tunable adhesion. To capture this interplay, we develop a theoretical framework that couples elasticity and viscosity, providing new insights into how flexible structures enable adhesion control.
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All authors Mary Williams, Thomas Desmedt, Fabian Brau, Pascal Damman

Solar and Stellar Astrophysics

An optimized tidal-trigger model of the QBO, and some implications for the Carrington event

F. Stefani, G.M. Horstmann, G. Mamatsashvili et al. (+1 more)

Magneto-Rossby waves in the solar tachocline are currently being discussed as a potential cause of the quasi-biennial oscillation (QBO). By analyzing sequences of ground-level enhancement (GLE) events and S-flares, the dominant period of the QBO was recently shown to be close to 1.723 years, which is the dominant beat between the periods of the two-planet spring tides of Venus, Earth and Jupiter. We improve upon this model by taking into account the dependence of the three tidally-triggered magneto-Rossby waves on the actual strength of the toroidal field at the tachocline, which we infer from the averaged monthly sunspot number. When optimizing the parameters of this magnetic-field dependence, the correlation of the tidal-forcing function with the 109 extreme solar events reaches values of up to 0.8. This is much higher than the corresponding value for the field-independent tidal forcing function (appr. 0.4), and also higher than the correlation with the sunspot number (appr. 0.56). Based on this improved model, we discuss some interesting parallels between the Carrington event of 1859 and the clustering of strong solar events in summer and autumn 1989. We also make some cautious forecasts for the remainder of cycle 25.
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All authors F. Stefani, G.M. Horstmann, G. Mamatsashvili, T. Weier

Solar and Stellar Astrophysics

Revealing mixed modes in compressible hydrodynamical simulations of red giant stars

Nils B. de Vries, Arthur Le Saux, Isabelle Baraffe et al. (+4 more)

Mixed modes are observed in many low-mass evolved stars. They provide information about core rotation rates of these stars, which are lower than predicted by stellar evolution models. The mixed modes themselves have been invoked as an angular momentum transport mechanism, but estimating their transport efficiency requires knowledge of their amplitudes. We constrain, for the first time, the mixed mode amplitudes in 2D hydrodynamical simulations of a $1.3M_\odot$ red giant using the code music. We perform two simulations with outer radial truncations at fractional radii $r_o/r_\star = 0.90$ and $r_o/r_\star = 0.98$. We compare the modes in the simulation with those found using both gyre and a dedalus eigenvalue solver. Excellent frequency agreement is found for all p-dominated modes, with minor discrepancies for g-dominated modes, especially in the frequency range $[60, \ 240]\ \mu\mathrm{Hz}$. We find excellent eigenfunction agreement for all modes except those in this frequency range. According to empirical predictions the largest kinetic energies are located around $\nu_{\mathrm{max}} = 312.8\ \mu\mathrm{Hz}$, but in both simulations the modes with frequencies $\nu <50\ \mu\mathrm{Hz}$ have the largest kinetic energies. In the simulation with $r/r_\star = 0.98$, the simulated modes have extrapolated surface velocities comparable to the empirical predictions, with highest surface velocities in a bell-shaped curve peaking around $\nu = 700 \ \mu\mathrm{Hz}$. The extrapolated surface velocities of the low frequency modes are small, and thus hard to observe, but their large kinetic energies deeper in the interior could significantly impact angular momentum transport, which has not yet been investigated.
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All authors Nils B. de Vries, Arthur Le Saux, Isabelle Baraffe, Thomas Guillet, Richard H. D. Townsend, Armand Leclerc, Adrien Morison

Mathematical Physics

Einstein-Kropina Metrics and Their Application in Finsler Gravity

Sjors Heefer, Fidel F. Villaseñor and Andrea Fuster

We generalize the Einstein condition for Kropina metrics obtained in the positive definite setting by Zhang, Shen and others to all signatures. As examples of Einstein-Kropina metrics $L=L_{a,b}$, we construct new explicit positive definite ones and the first ones with Lorentzian signature. Next, we classify all Einstein-Kropina solutions to the vacuum equation of Finsler gravity by Pfeifer and Wohlfarth, in arbitrary dimension and including a possible cosmological constant $\Lambda$. For the Lorentzian and positive definite cases, the local picture is as follows. In dimension 4 or lower, only the trivial solution exists: a Minkowski or Euclidean space, essentially. In dimension 5 and higher, the solutions are those $L_{a,b}$ for which the metric $a$ is a product of the real line with a Ricci-flat metric (Lorentzian or Riemannian) and the vector field $b$ is the unique unit vector on the first factor. As a very surprising rigidity phenomenon, all Einstein-Kropina solutions to the $\Lambda$-vacuum equation are Berwald and Ricci-flat, and the cosmological constant necessarily vanishes.
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Materials Science

Skyrmions in Synthetic Antiferromagnets: Collapse and Nucleation

M.N. Potkina

Magnetic skyrmions in synthetic antiferromagnets are promising nanoscale bits, but their usefulness depends on how reliably a written pair survives and can be created. Using a reduced lattice model, we compute minimum energy paths for collapse of an antiferromagnetically bound skyrmion pair and for reverse nucleation from a pinned antiferromagnetic reference state. With antiferromagnetically pinned boundaries, the main saddle energy changes only weakly with pinned-island size, whereas the skyrmion-pair minimum carries a strong size-dependent boundary penalty. For large pinned islands, collapse is layer-sequential and can pass through a single-layer skyrmion intermediate whenever this state satisfies the relaxation criterion. The much larger reverse barrier for nucleation shows a strong asymmetry with collapse in the same pinned-boundary model and is consistent with assisted layer-sequential writing.
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Quantum Gases

Failure of the Quench Action Formalism for Mott Insulator Initial States

Garry Goldstein

The quench action formalism relies on the assumption that the overlap between a generic initial state $\left|\Psi_{0}\right\rangle $ and an eigenstate of an integrable model - defined through the rapidities $\left|k_{1},...k_{N}\right\rangle $ - can be written as: \begin{equation} \left\langle k_{1},...k_{N}\mid\Psi_{0}\right\rangle =\exp\left(-S_{\Psi_{0}}\left(\rho\left(k\right)\right)\right),\label{eq:Exponential} \end{equation} where $\rho\left(k\right)$ is the quasiparticle density of the state $\left|k_{1},...k_{N}\right\rangle $ and $S_{\Psi_{0}}$ is some smooth function of $\rho\left(k\right)$ that depends on $\Psi_{0}$. In particular the quench action formalism assumes the overlap depends smoothly on the quasiparticle density $\rho\left(k\right)$. In this work, by explicit counter example, we show that this is not the case. We consider the quench between a Mott insulator and a Lieb Liniger gas. We show that the overlap between the ground state of the Mott insulator and arbitrary eigenstates of the Lieb Liniger gas has a highly singular behavior and no expression like Eq. (1) applies. We do so within the Tonks Girardeau limit of the Lieb Liniger gas and to leading order in the $1/c$ expansion for the overlap (with $c$ being the coupling constant of the Lieb Liniger gas). In the Appendix we show similar results for overlaps in the XXZ model with crystal states.
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High Energy Physics (Phenomenology)

Joint probes of dark matter annihilation from neutrino detectors and CMB targets

Ruifeng Leng and Shao-Ping Li

Dark matter (DM) annihilation into neutrinos provides a promising observational channel targeted by current and forthcoming neutrino detectors. However, the detection of such neutrino fluxes alone cannot uniquely determine their astrophysical or cosmological origin, such as the recent observations from Super-Kamiokande that hint at a small excess of electron antineutrino events. We propose that the effective number of neutrino species and the spectral distortion of the cosmic microwave background (CMB) can serve as complementary observables to probe neutrino signatures from DM annihilation. Using a simple model-independent analysis, we determine the detection windows of these cosmic observables that overlap with the experimental sensitivities from the Super-Kamiokande, Jiangmen Underground Neutrino Observatory, Hyper-Kamiokande, and the Deep Underground Neutrino Experiment, showing that joint probes of large DM annihilation to neutrinos with MeV-GeV masses can be achieved by neutrino detectors and CMB experiments.
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Optics

Generalized analytical relations to describe global optical systems with a plenoptic camera

Marc Brunel, Pierre Schleuniger, Adrian Marszalek et al. (+4 more)

The optical transfer matrix formalism is used to describe global set-ups incorporating a plenoptic camera. Analytical relations that give the effective resolution, depth of field, disparity and optimum patch size for image reconstruction are established versus the optical parameters of any global arrangement. The potentiality of this formulation is illustrated analyzing experimental results obtained in astigmatic cylindrical imaging conditions.
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All authors Marc Brunel, Pierre Schleuniger, Adrian Marszalek, Valentin Muset, Ramana Kukkarasi, Sébastien Coetmellec, Jean-Bernard Blaisot

Materials Science

Cocktail effect and robust Berry curvature driven anomalous Hall conductivity in the entropy-stabilized Heusler alloy Co$_2$(Ti$_{0.25}$V$_{0.25}$Cr$_{0.25}$Fe$_{0.25}$)Al

Suraj Kushwaha, S. K. Panda, Sourav Marik et al. (+2 more)

The interplay between chemical disorder and persistence of Berry curvature driven transport phenomena remains an important open question in entropy-stabilized systems. Here, we synthesize an entropy-stabilized Heusler alloy Co$_2$(Ti$_{0.25}$V$_{0.25}$Cr$_{0.25}$Fe$_{0.25}$)Al and systematically investigate its structural, magnetic, and magnetotransport properties using a combination of experimental measurements and density functional theory (DFT) calculations. The system crystallizes in cubic space group $Fm\Bar{3}m$ and exhibits ferromagnetism with saturation magnetization in close agreement with the Slater–Pauling prediction. Transport and magnetotransport measurements reveal metallic behavior and a pronounced anomalous Hall effect with an anomalous Hall conductivity of approximately $134.4~ \Omega^{-1}$.cm$^{-1}$. Combined experimental observations and first-principles calculations establish that the anomalous Hall effect is predominantly intrinsic in origin and originates from the Berry curvature of the electronic bands. Remarkably, despite the substantial configurational disorder and the dilution of the constituent parent compounds, the anomalous Hall conductivity remains comparable to the largest values reported in the corresponding parent Heusler systems. This behavior reflects the manifestation of the cocktail effect, one of the core characteristics of entropy-stabilized systems. Our results also demonstrate that Berry curvature mediated transport persists in this chemically disordered system and indicates that entropy engineering can be a promising route for tuning intrinsic anomalous Hall responses.
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All authors Suraj Kushwaha, S. K. Panda, Sourav Marik, Kartik Samanta, Tirthankar Chakraborty

Nuclear Theory

Impact of Shape Coexistence on Nuclear Stability

G. Saxena, H. Sikhwal, N. Chandnani et al. (+4 more)

Nuclear decay properties are conventionally predicted assuming nuclei decay from their ground-state configurations. However, this often neglects a fundamental structural complexity which is the phenomenon of shape coexistence, where nuclei possess multiple competing configurations at nearly degenerate energies. When both parent and daughter nuclei can exist in different energy minima, multiple decay pathways become possible. We systematically investigate how shape coexistence influences nuclear decay for approximately 1500 even-even nuclei ($8 \leq Z \leq 118$, $8 \leq N \leq 184$) using the Nilsson-Strutinsky method and relativistic mean-field calculations with NL3$^*$, DD-ME2, and DD-PC1 functionals. We identify around 400 nuclei exhibiting competing energy minima separated by less than 1 MeV. For these shape-coexisting nuclei, we calculate $\alpha$, $\beta^+$ and $\beta^-$ decay half-lives considering all possible transition pathways between the competing minima. Our results demonstrate that shape coexistence substantially impacts decay predictions, with half-lives showing variations up to nearly one logarithmic unit depending on which configurations participate in the transition. Comparison with experimental data from NUBASE2020 shows that pathways involving the second minimum sometimes reproduce measured lifetimes more closely than conventional ground-state to ground-state assumptions. Branching ratios exhibit even stronger sensitivity, with certain nuclei displaying complete inversions of the dominant decay mode depending on configuration choice. These pathway-dependent variations are not due to model uncertainties but reflect inherent structural effects. The correlation between the shape dynamics and nuclear stability establishes the shape coexistence as an essential component in predictive nuclear structure and astrophysics studies.
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All authors G. Saxena, H. Sikhwal, N. Chandnani, Pranali Parab, Siddharth Parashari, Gabriela Llosá, Mamta Aggarwal

High Energy Astrophysical Phenomena

A series of unfortunate events: CHIME/FRB misclassification of a Galactic pulsar as a periodic fast radio burst

The CHIME/FRB Collaboration

In 2022, the CHIME/FRB Collaboration reported the detection of FRB 20191221A, an apparent fast radio burst exhibiting a significant periodicity of 217 ms. Recently, this event has been identified as a series of pulses originating from the known Galactic pulsar PSR J0248+6021. The initial misidentification was caused by an unusual calibration problem with the CHIME telescope, coupled with the atypical characteristics of the pulsar's emission. Here, we detail the issues with the calibration and how it led to a many-degree offset in the pointing of the calculated beams. We describe how we verified that this problem has not affected any other FRB localization, including those reported in the Second CHIME/FRB Catalog, and our newly implemented checks to ensure this mispointing problem does not affect future data.
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Quantum Physics

Projector Quantum Variational Ansatz

Thomas Dumontier, Robin Ollive and Stephane Louise

Quantum computing offers several algorithms for computing the ground state of a problem Hamiltonian. Algorithms in the Fault-Tolerant Quantum Computing (FTQC) regime, such as Quantum Phase Estimation (QPE) and Quantum Signal Processing (QSP), are the most desirable because they offer optimal asymptotic scaling. In the Noisy Intermediate Scale Quantum (NISQ) regime, the most realistic approaches involve Variational Quantum Eigensolver (VQE) algorithms and their variants. A central difference between the two regimes is that FTQC algorithms do not prepare the ground state via direct state transition. Instead, they build a project that identifies the ground state using ancillary qubits that flag the target subspace. The desired state is then recovered via amplitude amplification or post-selection. In this work, we propose a VQE ansatz whose structure is more similar to that of an FTQC algorithm. We introduce the Projector Variational Ansatz (PVA), which incorporates the projector structure into the adaptive variational setting. Depending on its parametrization, this ansatz can be equivalent to either an Adaptive Derivative-Assembled Pseudo-Trotter (ADAPT)-VQE when all ancilla mixing angles vanish, or to an Intermediate Scale Quantum (ISQ)-QSP quantum circuit structure. We benchmarked PVA against an ADAPT-VQE baseline using both qubit-excitation and fermionic-operator pools. We propose an implementation in which an L-layer PVA circuit is designed using 3L + 1 parameters and requires only one ancilla and two additional CNOT gates per Pauli generator used in ADAPT. Our experimental results show that this first proposal for PVA converges using fewer CNOT gates than the standard ADAPT-VQE on the tested system.
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Fluid Dynamics

The Omitted Noise Contribution of Surface Normal Variation: Farassat's Formulation 1A revisited

Qitian Tao, Chen He, Xiaohua Liu et al. (+2 more)

Farassat's Formulations 1 and 1A have been extensively employed for propeller noise prediction. However, in the derivation of Formulation 1A from Formulation 1, the contribution associated with the temporal variation of the direction of the unsteady force is omitted, appearing mathematically as the temporal derivative of the local surface normal vector. Through rigorous mathematical derivation, this study demonstrates that the omitted term constitutes an indispensable component of the acoustic source representation. Accordingly, a Modified Formulation 1A is proposed by explicitly retaining the normal vector temporal derivative term in the time-domain formulation. Far-field acoustic predictions for propellers are performed to evaluate the proposed formulation, and the results confirm both its theoretical consistency and predictive capability.
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All authors Qitian Tao, Chen He, Xiaohua Liu, Zhengwu Chen, Jiale Lu

Nuclear Theory

External-Field-Assisted Muon Reactivation in Muon-Catalyzed Fusion: A Rate-Network Criterion for Reducing Alpha Sticking

Wei Kou and Xurong Chen

Alpha sticking is a major loss channel in deuterium–tritium muon-catalyzed fusion. We study whether an additional external-field-assisted stripping channel can reduce the residual sticking loss after conventional collisional reactivation. The external contribution is written as $R_X=f_XP_X\eta_X$, where $f_X$ is the space–time overlap between the external field and the residual stuck $(\alpha\mu)^+$ population, $P_X$ is the microscopic stripping probability, and $\eta_X$ is the probability that the stripped $\mu^-$ is returned to the $d\mu/t\mu\to dt\mu$ fusion cycle before escape or decay. This gives $\omega_S^{\rm eff}=\omega_S^0(1-R_{\rm col})(1-R_X)$ and leads directly to a probability-level no-go condition, $\eta_X^{\rm crit}>1$, for any target improvement requiring more recycling than is probabilistically available. We construct an energy-resolved post-stripping rate network including slowing down, atomic capture, free escape, muon decay, atomic-stage loss, ordinary molecular formation, and an effective resonant $dt\mu$ channel. Benchmark scans show that the useful regime is a transport window: the stripped muon must be confined and recycled efficiently. With the reference inputs used here, the best-performing scenario increases the cycle yield from $N_{\rm fus,\mu}=112.6$ in the collision-only case to $N_{\rm fus,\mu}=156.5$. Resonant molecular formation suppresses atomic-stage loss and broadens the high-recycling region, but it cannot compensate for prompt escape or poor field–population overlap. The rate network therefore identifies the transport and overlap conditions required for external-field-assisted reactivation to reduce residual alpha sticking.
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High Energy Physics (Phenomenology)

Mechanical distribution of the pseudoscalar charmonium and bottomonium on the light-front

Ashutosh Dwibedi, Satyajit Puhan and Sabyasachi Ghosh

We investigate the energy-momentum tensor of pseudoscalar charmonium and bottomonium within the framework of the self-consistent light-front quark model. The gravitational form factors (GFFs), namely the $A$ and $D$-terms, are evaluated in terms of the light-front wave functions. The corresponding spatial mechanical distributions in the transverse plane are obtained through the Fourier transform of these GFFs. To examine the sensitivity of the results to the internal quark-antiquark distribution inside the meson, two distinct Gaussian forms are employed for the spatial part of the wave function. We analyze several mechanical properties in the transverse plane, including the momentum density, pressure distribution, shear stress, force density, and internal energy density. The pressure distribution exhibits a node where it changes sign from positive (repulsive) to negative (attractive) with increasing transverse distance. The force distribution remains positive throughout the transverse plane, supporting the stability condition proposed in earlier studies. Most of the spatial distributions, except for the shear stress, are found to be sensitive to the choice of the spatial wave function near the center of the meson, while they become nearly insensitive toward the periphery. In contrast, the shear stress distribution exhibits noticeable sensitivity to the choice of wave function in the intermediate transverse region.
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High Energy Astrophysical Phenomena

Infrared Echoes of Precessing Tidal Disruption Events

Hong-Zhou Wu, Shao-Yu Fu, Wen-Long Xu et al. (+2 more)

A tidal disruption event (TDE) occurs when a star is torn apart by a supermassive black hole. The resulting UV/optical flare irradiates parsec-scale dust, producing delayed mid-infrared echoes that persist for years. These echoes provide unique calorimetric probes of the total radiated energy and dust geometry. Existing models usually assume static axisymmetric illumination patterns. However, the TDE accretion disk is likely misaligned and undergoes relativistic precession. In this work, we present a theoretical framework for infrared dust echoes from a precessing TDE disk. The precession will lead to highly variable infrared light curves, which can be revealed by high-cadence observations. The overall profile of the infrared light curves shows double-peaked to single-peaked pattern transitions as a result of the changes in the viewing angle or precession angle. The results indicate that infrared echoes are dynamic tracers of the evolving lighting patterns of the central engine.
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All authors Hong-Zhou Wu, Shao-Yu Fu, Wen-Long Xu, Chang Zhou, Wei-Hua Lei

General Relativity and Quantum Cosmology

Gravitational waveforms from binaries in higher-derivative gravity: a Love story

Pablo A. Cano, Francesco Fucito, Jose F. Morales et al. (+1 more)

We study the emission of gravitational waves by a test particle orbiting a non-rotating black hole in higher-derivative gravity theories with cubic and quartic contractions of the Riemann tensor. To this aim, we first derive the master equations describing even- and odd-parity perturbations in the presence of an arbitrary source term, and then construct a Post-Minkowskian expansion of the solutions to the homogeneous master equations. Specializing to a circular binary system, we compute the Post-Newtonian expansion of the waveform, as well as the energy and angular-momentum fluxes at infinity. We show that higher-derivative corrections to the waveform and to the fluxes always appear at 5PN order, and are universally proportional to the Love number describing the deformability of the geometry under the $\ell=2$ mode perturbation. These analytical results are validated against numerical computations, which also allow us to extend the analysis to larger velocities.
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All authors Pablo A. Cano, Francesco Fucito, Jose F. Morales, Alejandro Ruipérez

High Energy Physics (Theory)

On Quantum Aspects of 1-Form Symmetries II: Bordism, Invertible Phases, and Anomalies

Weizhen Jia, Yi-Nan Wang and Yi Zhang

We study quantum anomalies associated with $U(1)$ 1-form symmetries from the perspective of invertible phases and bordism. We compute the oriented and spin bordism groups of the Eilenberg-Mac Lane space $K(\mathbb{Z},3)$ up to degree 8 using the Atiyah-Hirzebruch spectral sequence, resolving the relevant extension problems by geometric arguments and identifying both bordism invariants and geometric generators. We then relate these invariants to perturbative and global anomalies, and discuss physical examples and top-down constructions of the corresponding anomaly terms. For 5-dimensional theories, we find a new mixed perturbative anomaly between the $U(1)$ 1-form symmetry and spacetime diffeomorphisms, while for 7-dimensional theories we find a new $\mathbb{Z}_2$-valued discrete anomaly intrinsic to the $U(1)$ 1-form symmetry. We also discuss their boundary realizations and give new physical interpretations of these anomalies.
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Quantum Physics

Quantum correlations and coherence in a two-qubit anisotropic $XY$ under magnetic field

Ahmed Jellal, Pablo Díaz and David Laroze

We study thermal quantum correlations and coherence in Heisenberg $XY$ model with anisotropic interactions under a uniform magnetic field $ B $. Using concurrence $C$, local quantum uncertainty (LQU), Bell-Clauser-Horne-Shimony-Holt (CHSH) nonlocality $ \mathbb{B}$, and coherence $C_l$ as quantifiers, we analyze how magnetic anisotropy $ \delta_m $, coupling anisotropy $ \delta_c $, Dzyaloshinskii-Moriya (DM) interaction $ D $, temperature $ T $, and magnetic field $ B $ modulate quantum resources. At low temperatures and relevant magnetic fields, the entanglement is maximized, but exhibits sudden death for $ \delta_m = 0 $, which turns into a smooth decay as $ \delta_m $ increases, highlighting its stabilizing role. LQU shows that stronger anisotropy suppresses quantum correlations, while $ \mathbb{B} $ induces a non-monotonic response peaking at a critical field $ B_c $. Bell-CHSH nonlocality violations ($ \mathbb{B} > 2 $) persist below $ B_c $, but thermal noise ($ T \geq 1 $) suppresses them. Coherence $ C_l $ is most robust to thermal fluctuations, especially for high \( \delta_m \), which also dampens abrupt quantum phase transitions. The DM interaction is essential for entanglement generation, with $ D $ and anisotropy synergistically enhancing correlation resilience. We identify a hierarchy of thermal degradation: nonlocality ($ \mathbb{B} $) vanishes first, followed by entanglement ($ C $), then general quantum correlations (LQU), while coherence $ C_l $ persists the longest. These results demonstrate tunable control of quantum resources via anisotropy and external parameters, providing insights for the design of robust spin-based quantum technologies.
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Quantum Physics

Exact noise characterization of entanglement distribution in star networks

Kenneth Goodenough, Xiaonan Chen and Patrick Emonts

Multipartite entanglement forms the core of many networking applications. In the near-term future, it is expected that multipartite distribution will be achieved first through star topologies, making it important to understand the noise incurred during the distribution process. In such networks, elementary links are created stochastically and successful links must be stored while waiting for the remaining links, causing memory decoherence that depends on the random waiting times. We derive analytical expressions for both the average noise and its distribution, when distributing GHZ states under memory dephasing in star networks. We study and compare two distribution protocols: the factory and piecemaker protocol. Furthermore, we find expressions for the case of a global cut-off (allowing fast optimization of the cut-off without requiring Monte Carlo simulations) and extend the analysis for the factory protocol to depolarizing noise for arbitrary states.
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Materials Science

Unravelling the Role of Stacking Disorder on the Optoelectronic Properties of Zn3P2

Francesco Salutari, Nico Kawashima, Aidas Urbonavicius et al. (+9 more)

Zinc phosphide (Zn3P2) is a promising photovoltaic absorber for thin-film and flexible solar cells due to its earth-abundant composition and favourable optoelectronic properties. Recent advances in epitaxy have enabled the growth of high-quality Zn3P2 thin films despite the challenges posed by its incompatible lattice parameter and thermal expansion coefficient. However, Zn3P2 remains prone to intrinsic extended defects, such as rotated domains, that can limit device performance. Here, using (scanning) transmission electron microscopy, we identify a previously unreported class of extended defects that appear as planar faults described by displacement vectors lying in the (001) plane. Within a pseudo-cubic description of Zn3P2, we establish a direct correspondence between planar faults and rotated domains, showing that both arise from the flexible ordering of vacant sites in the Zn sublattice. First-principles calculations reveal an extremely low planar-defect formation energy of 2.5 mJ m-2, demonstrating that these defects form at essentially negligible energetic cost, in excellent agreement with their high experimentally observed occurrence. Additional density functional theory (DFT) calculations show that intrinsic planar defects neither introduce mid-gap electronic states nor significantly perturb the local electrostatic potential, indicating that they are electronically benign. Instead, we propose that planar defects indirectly degrade device performance by acting as preferential segregation sites for optically active point defects.
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All authors Francesco Salutari, Nico Kawashima, Aidas Urbonavicius, Helena Rabelo Freitas, Raphael Lemerle, Thomas Hagger, Kimberly A. Dick, Anna Fontcuberta i Morral, Simon Escobar Steinvall, Maria Chiara Spadaro, Silvana Botti, Jordi Arbiol