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Physics

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Wednesday 1 July

Fluid Dynamics

Two-dimensional simulations of hydrodynamic spin coupling in a two-rotor corral

Tsorng-Whay Pan and Jiwen He

We study hydrodynamic spin coupling in a two-rotor corral using DNS of 2D incompressible viscous fluid flow. An active rotor is driven at angular velocity W, and a nearby torque-free passive rotor selects an angular velocity w through hydrodynamic torque balance. The signed gear ratio Gamma=w/W distinguishes corotation from counterrotation, with Reynolds number Re=|\Omega|r^2/\nu. Motivated by a recent quasi-two-dimensional experiment, we use a DLM/FD method to compute planar phase diagrams of $\Gamma(G,Re)$ at corral sizes C=3, 4.5, and 6. The planar model recovers the benchmark gap route at Re=20: an intermediate counterrotation band, a wide-gap transition to corotation, gear-ratio magnitudes of order 10^{-2}, and the observed sequence of vortex attachment, detachment, and merger. It also produces a reentrant-like gap structure with a small-gap corotation region whose relation to the experimental close-range geometric state remains unresolved. The main discrepancy is the high-Re boundary. At the experimental mid-gap transect G about 0.3, the planar gear ratio approaches zero from the counterrotating side but does not cross through Re=400; at the narrower gap G=0.22, by contrast, the planar terminal spin reverses near Re=44. Wall-traction diagnostics show that this crossing is not the experimental shear-competition mechanism: the gap-facing counterrotating arc narrows but does not collapse or deflect as in the experiment, and the reversal at G=0.22 occurs by redistribution of the integrated planar torque. The strictly planar model therefore captures the broad gap-route architecture and the existence of a Reynolds-driven spin boundary, but displaces that boundary in gap and alters its surface-stress mechanism. The remaining mismatch points to finite-depth secondary motion, end-wall stresses, and apparatus geometry as plausible contributors to the experimental shear balance.
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Chemical Physics

Symmetry and Topology in Wavepacket Dynamics near Conical Intersections

Christopher Daggett, Jonathan Rawlinson and Lukas Muechler

Whether topology directly shapes chemical dynamics remains an open question in theoretical chemistry. The issue arises because degeneracies of adiabatic electronic states can generate nontrivial topological structure, and such degeneracies are common in polyatomic molecules. Existing work has largely emphasized static characterizations and dynamical studies of low-energy, highly symmetric models. Here we develop a symmetry-based analysis of nonadiabatic dynamics in two-state conical-intersection models that is predictive without invoking topological invariants. We show that the nodal-line structures associated with dynamics near a conical intersection are robust in highly symmetric settings, but should not in general be expected to persist once the relevant symmetry is broken.
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History and Philosophy of Physics

Selling the Stock, Not the Cream: The Soviet Émigré Career Premium of the 1990s

Vitaly Pronskikh

In the early-mid 1990s, scientists emigrating from the former Soviet Union to the United States – especially physicists, engineers, chemists, and biologists – frequently secured prestigious and visible positions, including professorships, named chairs, and laboratory leadership; comparable scientists arriving after about 2000 built more modest, less visible, and often non-academic careers. Against the common view that this reflects the people – the elite having left first – this article sets aside the thin apex of Nobel- and Fields-level émigrés and examines the larger cohort of capable but non-stellar scientists, showing that similar scientists fared differently by year of arrival. The explanation therefore lies in the structure of the receiving market, not primarily in individual ability. Reading premium appointments backward from later Nobel-level recognition risks survivorship bias: celebrated successes obscure the broader demand for Soviet scientific capital. I weigh four conditions that favoured the 1990s cohort and had largely closed by the mid-2000s: technology transfer and the export of a finite, distinctive stock of Soviet expertise that commanded a career premium; the favourable immigration regime created by the Soviet Scientists Immigration Act of 1992; the surge of U.S.-trained Chinese and Indian competitors; and the securitizing aftermath of 11~September 2001. All four mattered, but technology transfer and knowledge export were primary: their premium opened the window, and their depletion – as exported knowledge was published and absorbed into global science – removed the demand on which the other factors depended. A further cross-cutting mechanism, the cultural “ghettoization” of émigrés into co-national laboratory enclaves, capped their visibility and independent advancement. The imbalance between émigré generations was structural, not personal.
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Strongly Correlated Electrons

Nonperturbative Nonlinear Hall Effect in Nonequilibrium Steady States

Lei Geng, Martin Eckstein, Lei Chen et al. (+4 more)

The nonlinear Hall effect in quantum materials has attracted broad interest, yet most existing studies focus on the weak-field, perturbative regime. Here we develop a nonperturbative approach based on nonequilibrium steady-state Green's functions for dc-field-driven lattice systems, with dissipation and interactions incorporated through self-energies beyond the constant relaxation-time approximation and interband transitions treated alongside their intraband counterparts. Applied to a two-band semimetal model, our approach provides direct access to the strong-field Hall response beyond the nonperturbative crossover where the edge of the nonequilibrium distribution reaches Berry-curvature hot spots, a regime in which constant relaxation-time estimates and Berry curvature dipole calculations become unreliable. We further demonstrate that interaction and electron-phonon self-energies within dynamical mean-field theory can substantially change the Hall signal. Our framework enables quantitative simulations of nonequilibrium nonlinear Hall phenomena and provides guidance for strong-field transport experiments.
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All authors Lei Geng, Martin Eckstein, Lei Chen, Shouvik Sur, Silke Paschen, Qimiao Si, Philipp Werner

Optics

Monolithic Integration of Piezo-Optomechanical Photonics and CMOS Electronics

Matthew Zimmermann, Aileen Zhai, Andrew J. Leenheer et al. (+10 more)

Next-generation photonic architectures for AI, sensing, and quantum computing require thousands to millions of reprogrammable photonic devices on a chip[1]. The monolithic integration of Electronically-backed Photonic Integrated Circuits (EPICs) allows for very high density electrical interconnection and electronic drivers that can scale with photonics. Piezo-optomechanical photonic integrated circuits (POMPICs) offer low power consumption, high speed modulation, cryogenic compatibility and broadband optical transparency from ultraviolet to infrared wavelengths[2,3], but have not been demonstrated with monolithically integrated CMOS electronics. Here, we show a fully monolithic, all-CMOS fabricated platform for POMPICs co-fabricated with commercial control electronics. 200 millimeter photonic wafers are constructed directly on completed CMOS driver wafers by back-end-of-line processing, connecting integrated piezoelectric actuators under broadband silicon nitride waveguides to a high-density digital backplane comprising >2 million electrical connections per die with 6.4x6.4 micron electrode pitch. We introduce segmented POMPIC components as Photonic Digital-to-Analog converters (PDACs) that convert low-voltage digital electronic signals to multi-bit analog optical phase and amplitude modulation, and we demonstrate parallel control of optical phase shifters, Mach-Zehnder interferometers, optical routing trees, and tunable ring resonators using a standard HDMI interface to program CMOS electronics. We test multiple reticles and perform electronic and photonic characterization across the entire wafer to establish uniformity and yield, demonstrating wafer-scale integration of POMPICs on an electronic backplane and enabling dense, scalable electronic control of piezo-optomechanical circuits.
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All authors Matthew Zimmermann, Aileen Zhai, Andrew J. Leenheer, Julia Boyle, Mayank Mishra, Daniel Dominguez, Matthew Koppa, Wolf Jehle, Christopher Panuski, Mark Dong, Gerald Gilbert, Dirk Englund, Matt Eichenfield

Soft Condensed Matter

Elasto-Hydrodynamic Propulsion of a Magnetically Actuated Filament

Sohum Kapadia, Julien Chopin and Arshad Kudrolli

We investigate the low-Reynolds-number propulsion of a slender elastic filament with a dipolar magnetic head actuated by an oscillating field in a viscous fluid by studying its strokes and net forward motion. To capture these dynamics, we employ an elasto-hydrodynamic (EH) framework that couples Euler-Bernoulli beam mechanics with resistive force theory. Unlike prescribed-kinematics models, filament shapes here emerge self-consistently from the actuation and the force and torque boundary conditions (BCs). We demonstrate that viscous boundary contributions are crucial for quantitative agreement and show that the swimming dynamics are governed by the EH length and a magneto-viscous-elastic stroke amplitude introduced here. The swimming speed is non-monotonic with increasing ratio of the swimmer length to the EH length, and is shown to reach a maximum when the swimmer length is on the order of the EH length. We further discuss the analytical limit in which the tail BCs can be described as free, and the limitations that arise when viscous contributions to the BCs are ignored.
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High Energy Astrophysical Phenomena

Magnetorotational instabilities in solids: Application to neutron-star crusts

Arthur G. Suvorov, Thomas Celora and Kostas D. Kokkotas

The magnetorotational instability can generate strong, turbulent substructure within magnetized shear flows. The efficacy of the mechanism as a function of microphysical aspects of the fluid, such as stratification and diffusivity, has been explored extensively. One aspect that has not been studied thus far, however, is whether the instability can also operate in solids. Motivated by the possibility that solid regions within planets or degenerate stars may rotate differentially with respect to liquid or gaseous layers during some phase of their life, we examine the extent to which elasticity suppresses the instability. A simplified, plane-parallel analysis reveals that only in cases where the flow is strongly sheared, such that the magnetic tension that would result from the instability in a liquid exceeds the shear modulus of the elastic cavity, can magnetic growth occur. In the context of dynamical tides in binary neutron-star mergers, this implies that the magnetic field can be amplified in the crust prior to coalescence only if the star boasts a spin frequency of $\gtrsim 300$Hz. If viscous heating weakens the crystalline structure prior to resonance, the required spin frequency is reduced.
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Instrumentation and Detectors

Towards triggerless four-dimensional detectors for High Energy Physics collider experiments

Vladimir V. Gligorov

High Energy Physics experiments at flagship colliders produce and process some of the biggest datasets on Earth, with the current generation of flagship experiments at the Large Hadron Collider producing more than a tenth of the world's total internet traffic every second. Moreover the quantities of data produced have increased exponentially over the past decades and this trend shows no sign of slowing down. In parallel, the use of picosecond timing is becoming more common in HEP detectors, enabling qualitatively new approaches to real-time processing and selections. I review the planned introduction of precision timing information into the upcoming upgrades of the CMS, ATLAS, and LHCb experiments. I discuss the ways in which the combination of timing and networking technology may enable future detectors to be designed as triggereless from the ground up, and reflect on the physics benefits of such a paradigm shift for the field.
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Quantum Physics

Lamb Shift of a Static Atom Facing a Rotating Surface

César D. Fosco, Fernando C. Lombardo and Francisco D. Mazzitelli

We study how the Lamb shift of a static atom is modified when a nearby planar body rotates rigidly about its normal while the atom is held at a fixed distance $a$. We derive a general formula for the shift in terms of the angularly Doppler-shifted reflection coefficients of the surface, valid for any axially symmetric planar material. Expanding the result to second order in the angular velocity $\Omega$, we identify two independent contributions associated with the orbital and spin components of the electromagnetic angular momentum. The orbital contribution, proportional to $(\Omega\rho)^2$, reproduces locally the Lamb shift induced by a surface translating at the tangential velocity $\Omega\rho$, whereas the spin contribution, proportional to $(a\Omega)^2$, originates from the rotational Doppler shift of the photon helicity and survives even on the rotation axis. We first illustrate the formalism using a graphene sheet and then apply it to finite-thickness Drude and plasma conductors and to doped semiconductors. Rotation enhances the Casimir-Polder interaction for graphene and metallic surfaces, whereas it weakens it for doped semiconductors, depending on whether the carrier plasma frequency reaches the near-field scale $1/a$. Above a threshold angular velocity, the atomic level also acquires a finite linewidth, providing a spectroscopic signature of quantum friction. Furthermore, rotation induces a novel component of the Casimir-Polder force, which is perpendicular to both the standard normal attraction and the tangential quantum-friction force.
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Exactly Solvable and Integrable Systems

Learning Lax Pairs: Revisiting the Classical Paradigm

Jimmie Adriazola, Gino Biondini, Wei Zhu et al. (+1 more)

A Lax pair $(L,P)$ is sometimes thought of as a structural certificate, in that the spatial operator $L$ carries the spectral data of an integrable system, and its isospectral evolution under $\partial_t L = [L,P]$ encodes the nonlinear dynamics. Yet, experience shows that the correspondence between equations and Lax pairs is much more nuanced than this picture suggests. Equations can admit Lax pairs that fail to encode the expected integrable structure. This paper probes that anomalous corner of the Lax pair landscape through five case studies (the Euler top, the free Schrödinger equation, the inviscid Burgers equation, the shallow water system, and the Korteweg–de Vries equation), each illustrating a different way the link to integrability can be distorted. The approach combines analytical calculations with the Sparse Identification of Lax Operators (SILO) framework, which proved useful throughout, in some cases confirming the textbook pair and in others surfacing alternatives worth understanding on their own terms. The recurring lesson across the five cases is that compatibility underdetermines the Lax representation, so that anomalous pairs are regular features of the landscape rather than pathologies. Notably, we show that a spectrally degenerate Korteweg–de Vries Lax pair, classified as fake by standard criteria, still generates the full conservation hierarchy through its operator algebra, which shows that a blunt dichotomy between true and fake Lax pairs can be too reductive.
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All authors Jimmie Adriazola, Gino Biondini, Wei Zhu, Panayotis G. Kevrekidis

Quantum Physics

Quantum nonlocal correlations of anomalous weak values

Ron Cohen, Avshalom C. Elitzur and Eliahu Cohen

Violations of Bell inequalities are a hallmark of entanglement, with only entangled states capable of exceeding classical bounds in standard Bell tests. Here we analyze anomalous weak values of the CHSH-Bell operator in pre- and post-selected (PPS) quantum ensembles, using them to define separability-constrained bounds on Bell-type nonlocal correlations in the presence of post-selection. Fixing the overlap between the pre- and post-selected states, we compare three scenarios: unrestricted boundary states, one separable boundary state, and both boundary states separable. For each case, we derive both the maximal weak value for a fixed Bell operator and the maximal bound obtained by further optimizing over all CHSH operators. Our results show that post-selection and entanglement are distinct operational resources: post-selection alone can enhance correlations, but entanglement is necessary to exceed the corresponding separable PPS bounds, and their combination yields the strongest attainable correlations. Thus the separable PPS bound plays the role of a post-selected separability benchmark, distinct from the standard Bell bound. We further show that the enhancement beyond the separable bound closely tracks the concurrence of the states that optimize the bounds, identifying entanglement as the source of the additional correlation strength. Finally, we show that nonlocal weak values provide post-selected entanglement witnesses, and we give a constructive protocol that detects every pure two-qubit source state with nonzero concurrence in the ideal state-adapted setting, even in regimes where the corresponding standard CHSH entanglement test is inconclusive. More broadly, our results motivate hybrid protocols that combine post-selection and entanglement, with possible applications to improved quantum sensing, weak-value amplification, and quantum information processing.
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Plasma Physics

Development of a thin-target hard X-ray bremsstrahlung detection system to study confined runaway electrons in Aditya-U Tokamak

Suman Dolui, Santosh Pandya, J.Kumar et al. (+23 more)

A specially shielded CdTe detector based hard X-ray (HXR) monitoring system equipped with a lead collimator has been developed and installed on the Aditya-U tokamak to investigate the dynamics of fast electrons (~20-200 keV) generated during sawtooth activity. The pre-existing HXR monitor in Aditya-U is exposed to the entire HXR bremsstrahlung emission from the plasma volume, peripheral limiters, and other structural components, which limits its ability to separately study the dynamics of lost and confined runaway electrons (REs). In contrast, the newly developed diagnostic has successfully measured the chord-averaged thin-target HXR bremsstrahlung emission encompassing the core plasma region, particularly within and around the sawtooth inversion radius. The measured HXR spectra are validated through forward modelling code that incorporates plasma parameters, confined RE characteristics, and the geometric configuration of the diagnostic system. The results confirm the capability of the developed HXR monitor to probe the fast-electron dynamics during internal plasma instabilities.
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All authors Suman Dolui, Santosh Pandya, J.Kumar, Bharat Hegde, Kaushlender Singh, J. Ghosh, Komal Yadav, Mitul Abhangi, Shishir Purohit, Minsha Shah, Laxmikanta Pradhan, Harshita Raj, R.L. Tanna, Ashok K. Kumawat, Injamul Hoque, Soumitra Banerjee, Ruchi Varshney, S. Aich, Rohit Kumar, K. A. Jadeja, K. M. Patel, M.K. Gupta, P. K. Chattopadhyay, A. Sen, Y.C. Saxena, R. Pal

Astrophysics of Galaxies

The Galactic centre G+0.633-0.0604 molecular cloud: A new astrochemical gold mine: I. Gas physical properties

D. San Andrés, L. Colzi, V. M. Rivilla et al. (+4 more)

In the Central Molecular Zone (CMZ), shocks play a key role in triggering star formation and driving chemical enrichment. The Sgr B2 complex is a prime template, hosting massive protoclusters (N, M, S) and the northern G+0.693 cloud, which exhibits shock-induced prestellar signatures. We report on G+0.633-0.0604, a newly identified shock-dominated and chemically rich cloud at the southern edge of Sgr B2, where the next star formation episodes are proposed. We characterise its physical properties and the shocks shaping it. We present analyses on CH$_3$CCH, CH$_3$CN, HC$_3$N, HNCO and several isotopologues of CO to infer the gas $T_{\rm kin}$ and density, using high-sensitivity spectral surveys from the Yebes 40m, IRAM 30m and APEX radio telescopes that covered ~100 GHz across the 31-275 GHz range. We also used 3 mm IRAM 30m mosaics (13'$\times$13') of Sgr B2 in HC$_3$N, HNCO and C$_2$H$_5$OH to probe G+0.633 environment. We identify three velocity components: a narrow main one (C1, $v_{\rm LSR}$~48.5 km/s; FWHM~10 km/s), and two broader, fainter components at higher velocities, C2 (~61 km/s; ~13 km/s) and C3 (~89 km/s; ~18 km/s), all showing similar properties ($T_{\rm kin}$~55-90 K, $N_{\rm H_2}$~(3-7)$\times$10$^{22}$ cm$^{-2}$, $n_{\rm H_2}$~(0.5-2.5)$\times$10$^{4}$ cm$^{-3}$) and extended distributions. C1 delineates G+0.633 physically and coincides with a peak in HNCO, supporting a shock-driven origin likely rooted in the cloud-cloud collision shaping Sgr B2 and also traced by C2, which extends north to G+0.693. C3 is kinematically unlinked and related to large-scale CMZ dynamics. Of the three, C1 may represent a very early protocluster phase, yet to be confirmed. G+0.633 thus emerges as a new shock-dominated CMZ cloud resembling G+0.693, providing another unique laboratory to investigate how shocks drive molecular complexity and regulate the onset of cluster formation in the CMZ.
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All authors D. San Andrés, L. Colzi, V. M. Rivilla, M. Sanz-Novo, S. Martín, I. Jiménez-Serra, S. Zeng

Astrophysics of Galaxies

Radiative filtering unifies broad-line phenomenology in active galactic nuclei

Mohammad Hassan Naddaf

Broad emission lines (BELs) are a defining feature of active galactic nuclei (AGNs), yet they weaken or disappear in both very low- and very high-accretion systems. These regimes are typically treated separately, and a unified physical explanation has remained elusive. Here we show that this behavior arises if line formation is governed not by the intrinsic luminosity of the central engine, but by the ionizing radiation field that survives filtering before reaching the broad-line region (BLR). In this picture, line production depends on the product of intrinsic ionizing capability and an effective transmission. Because the former increases from low accretion rates while the latter declines at high accretion rates, the effective ionizing field naturally develops a finite and non-universal window for BEL formation. This framework unifies the absence or extreme faintness of BELs in low-luminosity AGNs, LINERs, and weak-line quasars (WLQs), and accounts for the Baldwin effect and the $R_{\rm Fe}$ trend. It also necessarily implies the breakdown of standard BLR-based scaling relations in extreme accretion regimes. We show that a minimal quantitative realization reproduces this behavior across black-hole mass, accretion rate, and radiative efficiency. These results suggest that AGN emission-line phenomenology is governed by global regulation of the ionizing radiation field rather than by mere presence or condition of local gas.
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Optics

High-Beam-Quality Meta-Grating Couplers for Large Collimated Free-Space Beams on Silicon-on-Insulator

Max Schittenhelm, Sebastian Häfner, Steffen Sauer et al. (+1 more)

Photonic integrated circuits on the silicon-on-insulator (SOI) platform typically interface with free space via grating couplers, but scaling these to collimated beams with diameters beyond 100 $\mu$m requires a fundamentally different regime of extremely weak, spatially distributed coupling. While such large-area couplers have been demonstrated, their beam quality has remained largely uncharacterized, even though applications such as coupling into high-finesse resonators or trapping of cold atoms require both a large aperture and a near-Gaussian profile. This article presents an SOI meta-grating coupler that emits collimated, near-Gaussian beams of approximately 300 $\mu$m waist diameter. The design synthesizes the required emission profile from a spatially tailored coupling strength, realized by locally varying a sub-wavelength unit cell while independently setting the local emission angle. This approach achieves the very low coupling strengths required for large beams and yields a measured beam quality of $M^2 \leq 1.10$. The scheme extends directly to other target profiles, such as flat-top or higher-order modes, rendering meta-grating couplers a practical chip-to-free-space interface for mode-matching-sensitive applications.
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All authors Max Schittenhelm, Sebastian Häfner, Steffen Sauer, Stefanie Kroker

Plasma Physics

Understanding Non-Gaussian Chorus Wave Statistics via the Benjamin-Feir Index

D.J. Ratliff, O. Allanson, D. Rasinskaite et al. (+4 more)

We derive an extended wave action model for equatorial chorus waves, identifying a wave activity index (a version of the Benjamin-Feir index, BFI) which indicates non-Gaussian frequency spectra emerge when BFI$>$0.5. Global maps of this index indicate the night and dawn sectors ($0<{\rm MLT}<9)$ of the magnetosphere as the primary region for non-Gaussian wave statistics to emerge. Comparisons with events measured by the Van Allen probe A demonstrate good qualitative agreement whilst identifying key aspects for model refinement. A key strength of our model that our work highlights is its ability to account for the asymmetric frequency spectra characteristic of non-Gaussian chorus. This work ultimately establishes the first wave activity index that distinguishes Gaussian and non-Gaussian wave scenarios from first principles, providing the groundwork for a threshold-based quantification for use in space weather modelling.
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All authors D.J. Ratliff, O. Allanson, D. Rasinskaite, J. Stawarz, C. E. J. Watt, S. Chakraborty, A.W. Smith

Quantum Physics

Surface code logical operations on a superconducting quantum processor

Weiping Lin, Shaojun Guo, Yuwei Ma et al. (+144 more)

Fault-tolerant quantum computation requires logical operations that manipulate encoded information while preserving quantum error-correction protection. In planar surface-code architectures, code deformation and lattice surgery provide a local, measurement-based route to such operations. Here we experimentally realize key elements of patch-based surface-code logical processing on a 107-qubit superconducting quantum processor. We first implement a reusable primitive layer comprising merge and split, patch expansion and shrinkage, and deformations mediated by domain walls and twist defects. We then compose these primitives to realize logical state routing, the logical controlled-NOT gate, and the single-qubit Hadamard and phase gates, which together form a Clifford-generating set. All operations are implemented on distance-three rotated surface-code patches with multi-round syndrome extraction and neural-network decoding, without post-selection. Our results advance superconducting surface-code experiments from protected logical memory to active, patch-based fault-tolerant logical operations.
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All authors Weiping Lin, Shaojun Guo, Yuwei Ma, Zhengzhong Yi, Kai Zhang, Jiahao Bei, Jianbin Cai, Sirui Cao, Danning Chen, Guoben Chen, Jianguo Chen, Kefu Chen, Xiawei Chen, Zhe Chen, Zhiyuan Chen, Zihua Chen, Wenhao Chu, Hui Deng, Xun Ding, Zhuzhengqi Ding, Yajie Du, Bo Fan, Daojin Fan, Yuanhao Fu, Dongxin Gao, Ming Gong, Jiacheng Gui, Cheng Guo, Lianchen Han, Tan He, Linyin Hong, Yisen Hu, He-Liang Huang, Yong-Heng Huo, Chenyan Jiang, Lei Jiang, Tao Jiang, Wei Jiang, Zuokai Jiang, Dayu Li, Dongdong Li, Jiaqi Li, Jinjin Li, Junyun Li, Shaowei Li, Wei Li, Xu Li, Yuan Li, Yuhuai Li, Futian Liang, Nanxing Liao, Jin Lin, Maliang Liu, Yancheng Liu, Haoxin Lou, Kailiang Nan, Meijuan Nie, Le Niu, Wenyi Peng, Haoran Qian, Hao Rong, Tao Rong, Yanyan Shao, Huiyan Shen, Qiong Shen, Ganlin Song, Hong Su, Feifan Su, Chenyin Sun, De Sun, Liangchao Sun, Tianzuo Sun, Yingxiu Sun, Yimeng Tan, Jun Tan, Shibiao Tang, Yueyang Tang, Wenbing Tu, Jiafei Wang, Biao Wang, Chang Wang, Chen Wang, Chu Wang, Jian Wang, Rui Wang, Shengtao Wang, Xinzhe Wang, Zhi Wang, Zuolin Wei, Gang Wu, Yulin Wu, Hongjun Xia, Shouzhong Xia, Shiyong Xie, Zhilin Xie, Liang Xiong, Jianping Xu, Yan Xu, Yu Xu, Chun Xue, Kai Yan, Xin Yan, Weifeng Yang, Xinpeng Yang, Yang Yang, Yicheng Yang, Yangsen Ye, Zhenping Ye, Jianghan Yin, Chong Ying, Jiale Yu, Qinjing Yu, Chen Zha, Shaoyu Zhan, Cha Zhang, Fang Zhang, Haibin Zhang, He Zhang, Huanmei Zhang, Kaili Zhang, Qipeng Zhang, Shijia Zhang, Wen Zhang, Xin Zhang, Yiming Zhang, Yongzhuo Zhang, Ziying Zhang, Guming Zhao, Xintao Zhao, Youwei Zhao, Zhong Zhao, Luyuan Zheng, Fei Zhou, Liang Zhou, Naibin Zhou, Chengjun Zhu, Qingling Zhu, Yongsheng Zhu, Guihong Zou, Haonan Zou, Qiang Zhang, Chao-Yang Lu, Jianxin Chen, Cheng-Zhi Peng, Fusheng Chen, XiaoBo Zhu, Jian-Wei Pan

Classical Physics

Extended topological mode in a one-dimensional non-Hermitian acoustic crystal

Xulong Wang, Wei Wang and Guancong Ma

In Hermitian topological systems, topological modes (TMs) are bound to interfaces or defects of a lattice. Recent discoveries show that non-Hermitian effects can reshape the wavefunctions of the TMs and even turn them into extended modes occupying the entire bulk lattice. In this letter, we experimentally demonstrate such an extended TM (ETM) in a one-dimensional (1D) non-Hermitian acoustic topological crystal. The acoustic crystal is formed by a serie of coupled acoustic resonant cavities, and the non-Hermiticity is introduced as the non-reciprocal coupling coefficient using active electroacoustic controllers (AECs). Our work highlights the potential universality of ETMs in different physical systems and resolves the technical challenges in the further study of ETMs in acoustic waves.
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Physics and Society

Near-Term Emission Targets Need Immediate Attention in the USA

Trevor Barnes, Kamran Tehranchi, Brad Reinholz et al. (+2 more)

Given recent changes in federal climate policy, the United States is unlikely to meet its original 2030 Paris Agreement emission target of a 50-52% reduction from 2005 levels. However, rapid near-term abatement remains achievable through targeted multi-sector energy transitions. Extending the open-source energy system model, PyPSA-USA, to perform multi-sector analysis, we evaluate the primary drivers of USA energy costs and emissions though applying global sensitivity analysis. Our results suggest that fossil fuel price volatility is the dominant driver of marginal electricity and energy costs across most of the nation, however, uncoordinated state-level renewable mandates can induce localized cost spikes due to regional bottlenecks. We find that system climate impact (CO2e) is overwhelming sensitive to fugitive methane leakage rates and global warming potential assumptions. Addressing upstream methane leaks will play a crucial role in abating climate-related damages. Finally, demand-side electrification, specifically light-duty electric vehicles and service sector heating, can act as immediate levers for carbon abatement. The results of this work suggest that many of the Inflation Reduction Act's clean energy initiatives, that have since been repealed, are effective near-term solutions to reduce exposure to fossil fuel price and mitigate future financial penalties associated with the rising social cost of carbon.
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All authors Trevor Barnes, Kamran Tehranchi, Brad Reinholz, Malcolm Metcalfe, Taco Niet

Earth and Planetary Astrophysics

How Late Solid Enrichment Shapes Atmospheric Abundances in Giant Planets

Michael L. Balogh, Yuvan Sooryakumar, Sachen Gombu et al. (+4 more)

Atmospheric abundance measurements of giant exoplanets are increasingly used to infer their formation histories, motivating upcoming population studies with facilities such as the ESA Ariel mission. We present a population synthesis study of giant planet formation that combines pebble accretion, planetesimal formation with migration driven accretion, and an inheritance based chemistry model. We compare disks in which angular momentum transport is dominated either by turbulent viscosity or by magnetically driven disk winds. Wind-driven disks produce systematically more massive giant planets, but the atmospheric composition of those planets is otherwise similar to that of planets formed in viscous disks. In the absence of significant late-time solid pollution, atmospheric abundances such as C/H, O/H, and C/O retain sensitivity to the formation and migration history of simulated planets. When planetesimals efficiently enrich the envelope during migration, the abundance distributions collapse onto narrower sequences that are largely insensitive to the underlying disk accretion model. They remain correlated with formation and migration history, though with a smaller dynamic range in abundance. The resulting C/O distributions depend on planet mass in a way that agrees qualitatively well with observations, while the predicted range of C/H and O/H abundances is substantially narrower than observed. This suggests that there is a greater range in the amount of envelope pollution than represented in this simple model.
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All authors Michael L. Balogh, Yuvan Sooryakumar, Sachen Gombu, Francis J. Poulin, Pluto Jiang, Safwan Khan, Anthony Girmenia

High Energy Physics (Phenomenology)

An introduction to Hammer v2: Helicity Amplitude Module for Matrix Element Reweighting

Michele Papucci and Dean J. Robinson

The Hammer software library provides fast and efficient reweighting of large simulated datasets containing semileptonic $b$-hadron decays to any beyond Standard Model (BSM) theory, or to any form-factor description of the hadronic matrix elements. By enabling reweighting to a different underlying theoretical model after the computationally-expensive detector simulation step has already been completed, Hammer permits experimental analyses to employ forward-folding fitting strategies to recover underlying physical parameters without biases, or to properly characterize theory systematic uncertainties. This publication details upgrades to Hammer functionalities and its application programming interface (API) for version 2.x, and also provides associated documentation of the library's structure, syntactical conventions, and code flow. Substantial optimization of Hammer's internal tensor library now enables computational complexity to generically scale almost linearly with amplitude tensor rank times size rather than as a quartic, enabling reweighting into very high dimension spaces, such as the product of BSM Wilson coefficient and form factor parameter linear spaces, while also retaining Monte Carlo uncertainties. Updated Python bindings are implemented with bijective correspondence to the C++ interface, allowing full access to library functionalities.
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Physics and Society

A quantum model of opinion dynamics on networks

Weiqi Chu

Classical models of opinion dynamics represent individual opinions as scalar or vector values governed by the classical probability theory, either as deterministic quantities or random variables. This framework does not account for empirically observed phenomena such as cognitive ambivalence (where an individual simultaneously holds conflicting views) and order effects (where survey responses depend on the order in which questions are asked). We propose a quantum model of opinion dynamics in which each agent's cognitive state is represented by a density matrix that encodes both the expressed opinion and cognitive ambivalence. Survey questions become non-commuting self-adjoint operators, which provides a principled explanation for order effects. Our model also identifies quantities without classical counterparts, including quantum coherence and pairwise opinion covariances. Under a product state approximation, the quantum model reduces to the classical Friedkin–Johnsen opinion model. We test the framework on synthetic and real-world networks and observe that pairwise correlations follow network-dependent transient dynamics but converge to the same steady state regardless of the network, and that quantum coherence decays exponentially at a rate independent of the network.
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Pattern Formation and Solitons

A resonance in phonons scattering off a kink in the absence of a Peierls-Nabarro potential

Danial Saadatmand, Arpine Piloyan, David Amundsen et al. (+1 more)

We investigate the interaction of small-amplitude waves called phonons, with an initially static kink in an exceptional discretization of the $\phi^4$ model that is free of the Peierls-Nabarro potential. Phonons are generated by a localized harmonic source and scattered from one side of the kink. By computing the transmission and reflection coefficients over the entire phonon band, we demonstrate that the scattering properties depend strongly on the lattice spacing. In the weak-discreteness regime ($h<1$), the kink is nearly transparent and phonons are transmitted through it over most of the phonon spectrum. In contrast, for strong discreteness ($h>1$), significant reflection emerges even though the corresponding continuum $\phi^4$ kink is reflectionless. We further show that depending on the frequency of the incoming phonons, the kink experiences negative radiation pressure and is accelerated toward the incoming phonons for all lattice spacings considered, and this effect is much stronger for the strong discretness. The frequency dependence of the kink velocity and energy transfer is explained in terms of resonances associated with Doppler-shifted phonon frequencies and extrema of the phonon group velocity. Our results reveal that strong lattice discreteness can qualitatively modify phonon-kink interactions even in systems where the static Peierls-Nabarro potential is absent.
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All authors Danial Saadatmand, Arpine Piloyan, David Amundsen, Aliakbar Moradi Marjaneh

Geophysics

How effective normal stress oscillations advance failure in fault gouge: frequency dependence, non-failure window, and the role of dilation

Pritom Sarma, Einat Aharonov, Renaud Toussaint et al. (+1 more)

Cyclic pore-pressure or normal stress variations arise both in relation to natural earthquakes and in engineered subsurface systems, yet their effect on fault stability remains poorly constrained at the grain scale. Here we numerically model, using a coupled Discrete Element–fluid dynamics model, the response of a sheared, fluid-saturated or dry, gouge-filled fault to effective normal stress oscillations over a wide frequency range (0.5-10000 Hz). The effective normal stress is oscillated either by cycling the pore-pressure or by directly cycling the normal stress, while keeping the stress state below the Mohr-Coulomb threshold measured in continuous loading. Despite this sub-critical loading, we observe failure across most frequencies, with a non-monotonic frequency dependence. A distinct non-failure window emerges at intermediate frequencies (30-200 Hz), bounded by failure at both lower and higher frequencies; the system exhibits four regimes from cyclic failure-and-arrest to continuous sliding. Pore-pressure and normal stress oscillations produce the same regime structure, confirming that they act as equivalent forcings via Terzaghi's principle, with fluid coupling adding only a delay due to dilatant hardening. Sub-critical failure arises from dilation-induced strength deterioration via two mechanisms: (i) low-frequency cycles allow sufficient time for shear-driven ratcheting dilation, while (ii) high-frequency cycles induce dynamic dilation (acoustic fluidization) via amplified seepage forces, stress gradients and inertial forces. The intermediate non-failure window represents the gap between these mechanisms. These results identify frequency as a controlling parameter for failure in granular materials, with implications for dynamic earthquake triggering and cyclic injection protocols.
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All authors Pritom Sarma, Einat Aharonov, Renaud Toussaint, Stanislav Parez

Mathematical Physics

Small Denominators and Subresonant Accumulation in Weakly Nonlinear Dispersive Dynamics

P.Yu. Astafieva and O.M. Kiselev

We study a small-denominator mechanism in weakly nonlinear dispersive dynamics. After Fourier decomposition, a nonlinear dispersive equation becomes an infinite system of weakly coupled oscillators. Higher-order correction terms may then contain infinite families of nonresonant Fourier interactions whose detunings tend to zero. Such families do not produce exact secular terms, but their accumulated contribution may grow as a power of time. We call this effect subresonant accumulation. The rigorous part of the paper is the analysis of a model forced oscillator and of an abstract subresonant Duhamel sum. If the detuning and coefficients have the form $\Delta_n\sim c n^{-p}$ and $B_n\sim b n^{-\kappa}$, then the accumulated contribution grows as $t^{1-\alpha}$, where $\alpha=(\kappa-1)/p$. We then show how this mechanism appears in a quartic Fourier family for the Klein–Gordon dispersion law. For the full nonlinear partial differential equation we formulate a conditional approximation result: provided that all remaining resonant and almost resonant interactions are controlled, the subresonant term gives the leading long-time correction.
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Mathematical Physics

Parent Hamiltonians of Ergodic Matrix Product States

Owen Ekblad, Eloy Moreno-Nadales, Eric B. Roon et al. (+1 more)

Matrix product states (MPS) are quintessential examples of frustration-free gapped ground states of local interactions called parent Hamiltonians. In this work, we investigate parent Hamiltonians for a class of ergodic matrix product states (EMPS), which are MPS defined by site-dependent random tensors $\{X_j^{[k]}\}_{j=1}^D$ which are homogeneously distributed at every site $k$ in the spin chain. Here, the EMPS are not translation-invariant but rather statistically translation-invariant. Under a mild injectivity assumption, we show the thermodynamic limit of an EMPS is the unique frustration-free ground state of a parent Hamiltonian on the whole spin chain, which, depending on the statistical properties of the EMPS, may or may not be finite-range. In contrast to the translation-invariant regime, these Hamiltonians need not be gapped. Nevertheless, applying the martingale method while keeping track of local statistics gives conditions for a gap, in addition to pointing towards why there need not be a gap in general. We include examples of EMPS both with and without spectral gaps to illustrate our results.
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All authors Owen Ekblad, Eloy Moreno-Nadales, Eric B. Roon, Jeffrey H. Schenker

High Energy Physics (Phenomenology)

The theory of electric dipole moments: the view from below

Jordy de Vries

Permanent electric dipole moments (EDMs) of nucleons, nuclei, atoms, and molecules are among the most sensitive probes of CP violation beyond the Standard Model and are intimately connected to the strong CP problem and the origin of the matter-antimatter asymmetry of the universe. This review presents the theory of EDMs from the bottom up, tracing the chain of connections that links CP-violating interactions at level of elementary particles to observable EDMs across a wide range of systems. Starting from a general CP-odd effective Lagrangian at the quark-gluon level comprising the QCD theta term, quark EDMs and chromo-EDMs, the Weinberg operator, and CP-odd four-fermion interactions, I show how chiral perturbation theory organizes the nonperturbative QCD dynamics into a small set of hadronic low-energy constants, whose relative sizes are determined by the chiral representation of the underlying source. These hadronic interactions feed into calculations of nuclear EDMs and Schiff moments, which in turn enter atomic and molecular structure calculations that connect to experimentally accessible observables in diamagnetic and paramagnetic systems. Special attention is given to the recently identified sensitivity of paramagnetic systems to hadronic CP violation, which opens a new and relatively unexplored window on the quark-gluon sector. The complementarity of the full EDM portfolio including the neutron, light nuclei, atoms, and molecules, and the role of theory in disentangling the underlying source of CP violation is discussed throughout.
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Mesoscale and Nanoscale Physics

Resonant cooling of nuclear spins by optically-oriented holes in MAPbI$_3$ perovskite crystals

Mladen Kotur, Dmitri R. Yakovlev, Nataliia E. Kopteva et al. (+3 more)

Resonant cooling of nuclear spins by photogenerated spin-oriented holes is demonstrated for MAPbI$_3$ perovskite crystals. It is evidenced by Hanle-effect measurements under helicity-modulated excitation with variable frequency. The resonance position in magnetic field shifts toward higher fields with increasing modulation frequency. The invariance of the Hanle curve upon in-plane sample rotation is consistent with the involvement of $^{207}$Pb nuclei with spin $I = 1/2$, which do not exhibit quadrupolar splitting. The shape of the resonance feature in the Hanle curve reveals that the nuclear spins are cooled by carriers with a negative $g$-factor, consistent with holes. The resonance fields associated with the modulation frequencies exceed the half-width of the weakly localized hole contribution to the Hanle curve, indicating that strongly localized holes are the primary carriers responsible for the nuclear spin cooling.
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All authors Mladen Kotur, Dmitri R. Yakovlev, Nataliia E. Kopteva, Bekir Turedi, Maksym V. Kovalenko, Manfred Bayer

Mesoscale and Nanoscale Physics

Fabrication of high-quality topological insulator nanodevices from bulk-insulating air-sensitive Sb-Bi$_2$Se$_3$

Linh T. Dang, Ayushi Solanki, Yongjian Wang et al. (+2 more)

High-quality topological insulator (TI) materials are essential for the realization and detection of Majorana bound states (MBSs) in TI-superconductor hybrid platforms. Widely used compensated TIs exhibit substantial disorder and charge inhomogeneity, which may be detrimental for Majorana devices. In this regard, Sb-substituted Bi$_2$Se$_3$ (SBS) is promising, because it is non-compensated and yet achieves very low bulk carrier density. We systematically investigate the impact of thermal processing during microfabrication on the transport properties of SBS. We developed a room-temperature fabrication protocol that preserves the low carrier density of exfoliated SBS upon fabrication of Hall bar and nanowire devices as evidenced from the observation of quantum interference oscillations in nanowires, a large gate tunability, and clear signatures of weak antilocalization (WAL).
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All authors Linh T. Dang, Ayushi Solanki, Yongjian Wang, Oliver Breunig, Yoichi Ando

Strongly Correlated Electrons

Interacting quantum geometry from dressed parametric vertices

Alejandro S. Miñarro and Gervasi Herranz

Quantum geometry has emerged as a powerful framework for understanding topological, optical and transport phenomena, revealing connections between the quantum geometric tensor (QGT) and linear response functions. Building on these developments, recent works formulate quantum geometry so that the parameter space is extended from the Brillouin zone to the space of external perturbing fields that modify the ground state. Here we develop a self-consistent diagrammatric route to determine the QGT for generic parameter spaces, including collective fluctuations or structural distortions. With this in view, we generalize previous approaches to build the geometric tensor from interacting vertex correlations that provide the spectral metric and curvature. The formalism presented here extends the interaction-dressed vertex approach (previously applied to electromagnetic responses in momentum space) to collective electronic and structural deformation fields, complementing ongoing efforts to quantify many-body contributions to quantum geometry.
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