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Physics Physics

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Monday 6 July

Atomic Physics

Investigating Role of Electron Correlation Effects via Triple Excitations for Precise Evaluation of Energies and Hyperfine Structure Constants in $^{23}$Na

Vaibhav Katyal and B.K. Sahoo

Accurate determination of hyperfine structure constants in atomic systems provides important insight into the interplay of electron correlation and relativistic effects in the nuclear region. Although sodium (Na) is a relatively light atom, previous all-order relativistic many-body calculations of the magnetic dipole hyperfine constants for the low-lying states of $^{23}$Na show noticeable discrepancies with experiment. To address this, we calculate the ionization potentials and hyperfine structure constants of $^{23}$Na using relativistic coupled-cluster theory with explicit inclusion of triple excitations. We further incorporate corrections from the Breit interaction, quantum electrodynamics, and the Bohr-Weisskopf (BW) effect. Results from lower-order methods are also presented to assess the importance of different physical contributions across states. Our calculations demonstrate that contributions from the lower-order relativistic and BW effects play almost similar roles with the electron correlation effects, including triple excitations, and are essential for reconciling theoretical predictions with experimental observations. This study can also serve as a useful guide for understanding the role of triples in heavier alkali systems.
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Physics and Society · Cross-listed from nlin.AO

Steering the dynamics by controlling the temporal interaction network

Melvyn Tyloo

Many real-world coupled dynamical systems have the interaction structure and strength that evolve or adapt over time. Here, we investigate how one can control the state of a system by tuning its temporal interaction network. We present a framework based on nonlinear optimal control, where one has control over the coupling matrix of a dynamical system. We show how to obtain the gradient of the Lagrangian function of the system using the adjoint method. We then focus on a linear time-variant system for which we illustrate the framework. Finally, we explore how the states at the nodes can be steered to target trajectories, by controlling the coupling matrix, imposing various constraint on its structure. The workflow presented here can be leveraged to steer the dynamics of systems with artificial or engineered interaction that is tunable.
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Plasma Physics

Quasi mono-energetic, relativistic electron acceleration in a femtosecond, high intensity laser excited solid magnet

Trishul Dhalia, Anandam Choudhary, C. Aparajit et al. (+6 more)

The interaction of ultraintense lasers with magnetized overdense plasmas reveals a fundamentally new regime of laser-driven particle acceleration. Particle-in-cell simulations demonstrate the generation of directional, quasi-monoenergetic electrons in the MeV energy range superimposed on a broad thermal electron background with the estimated acceleration gradient of 3.6 MeV/{\mu}m, which is the highest till date. In contrast to conventional laser-plasma accelerators, which rely on underdense plasmas and are therefore constrained to relatively low plasma densities and limited beam charge, the present scheme operates in plasmas with densities orders of magnitude higher, opening new possibilities for the generation of high-flux energetic electron beams. A central result of this work is the demonstration of the excitation of electron Bernstein waves during relativistic laser interaction with magnetized overdense plasmas. The subsequent Landau damping of these electrostatic warm-plasma modes selectively transfers energy to resonant electrons, leading to the emergence of quasi-monoenergetic spectral peaks at energies that can be tuned through the applied magnetic field. To support the simulation results, we experimentally demonstrate the directional emission of energetic electrons from a simple permanent-magnet target irradiated by an ultraintense laser pulse, highlighting the practical feasibility of controlled electron-beam generation in dense plasma environments. These findings establish electron Bernstein waves as an efficient mediator of laser energy coupling in overdense plasmas and introduce a new paradigm for controlled particle acceleration and energy deposition in high-energy-density plasma systems.
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All authors Trishul Dhalia, Anandam Choudhary, C. Aparajit, Amit D. Lad, Ankit Dulat, Yash M. Ved, Rohit Juneja, Amita Das, G Ravindra Kumar

Fluid Dynamics

Nanosecond DBD-Induced Shock and Thermal Perturbations on Blunt Bodies in Hypersonic Flow

Nadav Friedman, Kostiantyn Kuzmenko, Oshri Ifergan et al. (+1 more)

Nanosecond-pulsed dielectric barrier discharge (DBD) plasma actuators were investigated on a generic blunt body in a Mach 6 Ludwieg tube to characterize the pressure and thermal perturbations relevant to hypersonic boundary-layer transition control. Complementary quiescent experiments were also conducted over ambient pressures representative of those predicted in the model nose region to isolate the influence of local thermodynamic conditions on actuator operation. Pulse-energy measurements and schlieren imaging showed that decreasing pressure reduced the deposited electrical energy per pulse, weakened the actuator-generated shock, and increased the spatial extent of the residual heated region owing to energy deposition over a larger plasma volume. Under Mach 6 Ludwieg-tube conditions, the actuator-generated shock interacted with and reflected from the detached bow shock, temporarily increasing the bow-shock stand-off distance by approximately 11%, while the residual heated region was advected downstream along the body. The schlieren images further permitted the evolution of the thermal disturbance to be distinguished from that of the actuator-generated shock. The results demonstrate two distinct perturbation mechanisms – a short-duration compression wave and a longer-lived thermal disturbance – whose relative importance is governed by the local thermodynamic conditions and which may independently promote hypersonic boundary-layer transition.
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All authors Nadav Friedman, Kostiantyn Kuzmenko, Oshri Ifergan, David Greenblatt

Geophysics

Joint Velocity Slope Diffusion Prior for Structurally Constrained Velocity Model Building

Francesco Brandolin and Tariq Alkhalifah

High-resolution velocity models are crucial for reservoir characterization and subsurface delineation. However, the band limited nature of our surface recorded data limits resolution. Utilizing well measurements to enhance the resolution of our subsurface models is an important objective. To this end, we present a diffusion-guided framework for structurally preconditioned velocity-model reconstruction from sparse well-log information. The proposed approach combines plane-wave PDE regularization, structurally preconditioned inversion, and measurement-guided diffusion posterior sampling within a unified formulation. Local structural slopes estimated through plane-wave destruction are used both to propagate well information along geological dip directions and to guide the diffusion sampling process through a joint velocity–slope generative prior. Numerical experiments on the Volve synthetic model and the Viking Graben field dataset demonstrate that the proposed framework improves structural continuity, lateral consistency, and geological realism compared with conventional structurally preconditioned inversion approaches while maintaining computationally practical inference through DDIM sampling.
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Optics · Cross-listed from cond-mat.str-el

Optical switching of antiferromagnetic domains by nonreciprocal heat current

Takeshi Hayashida, Shunsuke Izumikawa, Kenta Kimura et al. (+2 more)

What distinguishes front from back? In physics, such directionality emerges only when an underlying symmetry is broken. Antiferromagnets that inherently break both space-inversion and time-reversal symmetries provide a striking example, exhibiting nonreciprocal optical responses that depend on the direction of light propagation. Beyond distinguishing antiferromagnetic domains, we show that this nonreciprocity can deterministically create them. Using mid-infrared light, we demonstrate deterministic switching of antiferromagnetic domains in the magnetoelectric antiferromagnet LiFePO4, where illumination from opposite sides selectively stabilizes opposite domain states. Remarkably, the switching persists over a broad wavelength range rather than being confined to a narrow transition-specific spectral region, overcoming the spectral and material constraints of resonance-based optical switching schemes. The broadband switching originates from the material's intrinsic nonreciprocity through optically generated heat currents. Our results establish nonreciprocity as a general principle for deterministically controlling symmetry-broken phases with light.
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All authors Takeshi Hayashida, Shunsuke Izumikawa, Kenta Kimura, Carl S. Davies, Andrei Kirilyuk

Fluid Dynamics

A Multipurpose Thermal Convection Setup to Study Turbulent Super Structures

Hiufai Yik, Constantin Schettler, Eberhard Bodenschatz et al. (+2 more)

A thermal convection apparatus has been designed to study turbulent super structures at high Rayleigh numbers and Prandtl numbers of the order of unity. This apparatus consists of a rectangular cell with a length of $3.50\,\mathrm{m}$, width of $0.35\,\mathrm{m}$, and variable height, which is fixed at $0.70\,\mathrm{m}$ for the present study. This cell is installed inside a $5.6\,\mathrm{m}$ long pressure vessel facility, known as Göttingen Uboot, which can be filled with compressed gasses (air, helium, nitrogen, or sulfur hexafluoride) at pressures up to $19\,\mathrm{bar}$, enabling Rayleigh numbers up to $ Ra \leq 5\times 10^{12}$ and Prandtl numbers of approximately $0.7 \leq Pr \leq 0.9$. The convection cell is bounded vertically by top and bottom plates consisting of a three-layer composite structure in which a thin Lexan plate is sandwiched between highly conductive aluminum plates. This allows for spatially resolved heat flux measurements. Each plate is subdivided into four longitudinal segments that can be independently temperature-controlled to enable homogeneous temperatures and the imposition of horizontal temperature gradients at both the top and bottom boundaries. While the bottom plate is electrically heated, the top plate's temperature is regulated using temperature-controlled circulating pressurized water. The apparatus is well suited for precise heat flux measurements, with the results obtained being in good agreement with those previously reported in the literature.
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All authors Hiufai Yik, Constantin Schettler, Eberhard Bodenschatz, Umesh Madanan, Stephan Weiss

Fluid Dynamics

Estimating Hydrodynamic Coefficients for Floating Offshore Structures from Movement Data Using Physics-Informed Neural Networks

Anders Schou, Jens Visbech and Allan Peter Engsig-Karup

We present a method for estimating the hydrodynamic coefficients in the Cummins equations using time-series data from a moving body, such as a floating offshore structure. The proposed data-driven method is based on incorporating the Cummins equations governing the dynamics of a structural body interacting with water waves into a physics-informed neural network (PINN), along with available motion data. The proposed method first estimates the structure's state in terms of translational and rotational degrees of freedom, and then solves the inverse problem to determine the hydrodynamic forces acting on the body, expressed in terms of added mass, damping coefficients, and/or hydrostatic restoring. The Cummins equations are formulated as a first-order system, and both state and parameter estimation are performed using PINNs. The method is verified on the free decay of a sphere and a box. The results demonstrate that it is possible to estimate the state and hydrodynamic coefficients accurately, although accuracy depends on the volume and quality of the movement data.
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Atomic Physics

Super-molasses returns: All optical near-resonance laser cooling and trapping of neutral atoms from background vapor

Matt Himsworth, Chester Camm, Max Carey et al. (+12 more)

Laser cooled and trapped atoms have been the workhorse of atomic physics for the past four decades. The predominant method has been the highly versatile Magneto-Optical Trap. We describe an alternative laser trap involving a simple geometry of collimated laser beams that provides both a velocity and position dependent restoring force such that a dense cloud of cold atoms is formed. This technique produces similar atom number ($>10^6$) and density ($10^{10}$\,atoms/cm$^{3}$) to the Magneto-Optical Trap, albeit with no magnetic field. The beam geometry is compatible with conventional sub-Doppler cooling techniques, allowing the trapped cloud to be cooled to $< 10~\mu$K. We demonstrate the validity and robustness of the trap by capturing $^{87}$Rb atoms directly from the background vapor and provide a theoretical discussion of the underlying principles. This trap has many unique properties that make it highly suitable for quantum sensing, timing, and computing applications as well as a new tool in fundamental science and metrology.
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All authors Matt Himsworth, Chester Camm, Max Carey, Jack Saywell, Jonathan Woods, Vilius Atkočius, Florence Concepcion, Konstantinos Karakostas, Hannah Brady, Doruk Tan Atila, Ellie Heywood, Alex Jantzen, Andrei Dragomir, Christopher Morley, James Bateman

Instrumentation and Detectors

Detection of scintillation light in noble gases with wavelength-shifting optical fibers

S.R. Soleti, S. Torelli, G. Martínez-Lema et al. (+110 more)

Wavelength-shifting (WLS) techniques enable particle detectors based on noble gases, whose scintillation light is predominantly emitted in the vacuum-ultraviolet. We investigate WLS fibers coated with tetraphenyl butadiene (TPB) for scintillation light detection in gaseous xenon and argon at pressures up to 8.5 bar, motivated by future high-pressure xenon time-projection chambers of the NEXT program. Two detector configurations are studied: an elongated high-pressure vessel with four PTFE panels equipped with WLS fibers read by temperature-stabilized SiPMs, and a compact box-shaped detector operated at 1 bar Xe with WLS fibers read out by PMTs. Both operate with continuous gas purification. The detector response is characterized using cosmic muons and alpha particles from a $^{241}$Am source. With the SiPM setup, we measure a light collection efficiency (LCE) of ${1.18 \pm 0.01~\mathrm{(sta.)}~^{+0.07}_{-0.09}~\mathrm{(sys.)}~\%}$ for xenon and ${1.07 \pm 0.01~\mathrm{(sta.)}~^{+0.06}_{-0.08}~\mathrm{(sys.)}~\%}$ for argon. With PMT readout, we measure a LCE of ${0.45 \pm 0.01~\mathrm{(sta.)} \pm 0.05~\mathrm{(sys.)}~\%}$ in xenon, in agreement with the SiPM result once photon detection efficiency is accounted for. Average scintillation waveforms in xenon and argon are studied to assess the time structure of the emitted light. Cosmic-muon measurements yield a mean energy required to produce a scintillation photon $45\pm7~\mathrm{(sta.)}~^{+4}_{-5}~\mathrm{(sys.)}~\mathrm{eV}$ at 1.5 bar, in agreement with the literature. The results demonstrate that TPB-coated WLS fiber systems can reliably detect scintillation light in high-pressure gaseous noble detectors, with a LCE representing an upper limit for realistic large-scale TPCs, where additional photon losses from materials and fiber attenuation are expected.
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All authors S.R. Soleti, S. Torelli, G. Martínez-Lema, H. Almazán, A. Beck, A. Castillo, M. del Barrio-Torregrosa, P. Dietz, C. Echeverria, L. Gurriana, Y. Ifergan, I. Israelashvili, F. Lopez, F. Monrabal, E. Oblak, J. Pelegrin, J.G.M. Saraiva, M. Seemann, L. Arazi, J.J. Gómez-Cadenas, V. Álvarez, I.J. Arnquist, F. Auria-Luna, S. Ayet, Y. Ayyad, C.D.R. Azevedo, F. Ballester, J.E. Barcelon, J.M. Benlloch-Rodríguez, F.I.G.M. Borges, A. Brodoline, E. Church, M. Cid, X. Cid, C.A.N. Conde, C. Cortes-Parra, F.P. Cossío, R. Coupe, E. Dey, M. Elorza, R. Esteve, R. Felkai, L.M.P. Fernandes, P. Ferrario, F.W. Foss, Z. Freixa, J. García-Barrena, J.W.R. Grocott, R. Guenette, J. Hauptman, C.A.O. Henriques, J.A. Hernando Morata, P. Herrero-Gómez, V. Herrero, C. Hervés Carrete, A.F.B. Isabel, B.J.P. Jones, F. Kellerer, L. Larizgoitia, A. Larumbe, P. Lebrun, N. López-March, R. Madigan, R.D.P. Mano, A. Marauri, A.P. Marques, J. Martín-Albo, A. Martínez, M. Martínez-Vara, R.L. Miller, K. Mistry, J. Molina-Canteras, C.M.B. Monteiro, F.J. Mora, K.E. Navarro, P. Novella, D.R. Nygren, I. Osborne, J. Palacio, B. Palmeiro, A. Para, A. Pazos, M. Pérez Maneiro, M. Querol, J. Renner, I. Rivilla, C. Rogero, L. Rogers, B. Romeo, C. Romo-Luque, E. Ruiz-Chóliz, P. Saharia, F.P. Santos, J.M.F. dos Santos, I. Shomroni, A.L.M. Silva, P.A.O.C. Silva, A. Simón, M. Sorel, J. Soto-Oton, J.M.R. Teixeira, S. Teruel-Pardo, J.F. Toledo, C. Tonnelé, J. Torrent, A. Trettin, P.R.G. Valle, M. Vanga, P. Vázquez Cabaleiro, J.F.C.A. Veloso, J.D. Villamil, J. Waiton, A. Yubero-Navarro

Physics and Society · Cross-listed from q-bio.QM

Parenclitic hypergraphs and their application in personalized cancer therapy

K. K. H. Manjunatha, D. Aleja, F. Liu et al. (+16 more)

Understanding the differences between individual instances of the same complex system remains a central challenge, particularly in biological contexts. Parenclitic networks constitute a suitable means to detect deviations in correlations with respect to reference populations. Here, we introduce parenclitic hypergraphs, a general framework for identifying anomalies in higher-order correlations across arbitrary interaction orders. After validating the method on synthetic datasets and benchmark ones, we apply it to patient-derived cancer organoids, capturing temporal changes in gene expression between healthy and cancerous tissues as the disease progresses. Our approach not only reproduces known oncogenic signatures, but also reveals a previously unrecognized candidate therapeutic target. Since organoids are generated from individual patients, our method provides, for the first time, a viable protocol for personalized cancer therapy based on higher-order correlation patterns. These findings offer a novel, systems-level strategy for precision oncology grounded in complex systems theory.
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All authors K. K. H. Manjunatha, D. Aleja, F. Liu, M. Zhang, Y. Qi, L. Minati, G.-Q. Sun, S. Zhuang, C. Cai, J. Li, R. Criado, M. Romance del Rio, D. Papo, Y.-J. Ma, F. Fang, C. I. del Genio, Z. Zhao, H. Gao, S. Boccaletti

Optics · Cross-listed from quant-ph

Noise-limited secret key agreement with twin optical physically unclonable functions

Georgios M. Nikolopoulos

We investigate the use of twin optical fingerprints derived from correlated physical unclonable functions (PUFs), as a hardware-based platform for cryptographic key generation and distribution. Each fingerprint is associated with a random, yet reproducible speckle pattern, generated when coherent light is scattered by a disordered optical structure. We consider a pair of correlated optical PUFs, and study the conditions under which two honest parties can establish a common secret key, despite fabrication-induced variability and environmental noise. An explicit information-theoretic key-agreement protocol is developed, incorporating secure sketches, error reconciliation, and privacy amplification. We quantify information leakage due to public helper data, and derive lower bounds on the length of the final secret key. The analysis identifies the noise regimes in which secure key agreement is feasible, and examines the performance of both practical and near-capacity reconciliation schemes. Finally, we discuss how twin optical PUFs could be integrated into quantum key distribution (QKD) networks, as a mechanism for establishing an initial pre-shared secret key between two honest users, without relying on computational assumptions or trusted third parties.
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Optics

Focusing and light collection effects on plasma-induced frequency-resolved optical switching (PI-FROSt) traces

M. Guerras, Í. J. Sola, B. Alonso et al. (+4 more)

Plasma-Induced Frequency-Resolved Optical Switching (PI-FROSt) is a promising and recently proposed phase-matching-free technique for characterising ultrafast pulses across broad spectral ranges. We investigate the mechanisms of PI-FROSt trace formation through numerical simulations and experimental validation. The results reveal that trace characteristics are highly sensitive to the relative focusing geometry between pump and probe pulses, as well as the spatial region selected for signal collection. Depending on these conditions, the interplay between plasma defocusing and positive lens-like nonlinear effects causes either intensity depletion or enhancement in the probe beam, flipping the PI-FROSt trace. Simulations demonstrate that optimal gate stability also depends strongly on the focusing scheme and the collecting region. This study highlights that precise spatial and temporal optimisation is essential to properly exploit the benefits of this broadband pulse characterisation technique.
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All authors M. Guerras, Í. J. Sola, B. Alonso, E. Conejero Jarque, I. Lopez-Quintas, J. San Roman, A. Crego

Optics

When Reflection and Transmission Amplitude Coefficients Exceed Unity: Evanescent Waves, Resonances, and Optical Modes

Raúl de la Fuente

The reflection and transmission of propagating harmonic waves in linear optical systems have been widely discussed in the literature and are generally well understood. In passive systems involving only propagating waves, energy conservation constrains measurable quantities such as reflectance and transmittance, as well as the corresponding amplitude coefficients. However, when evanescent or damped waves are present, the reflection and transmission coefficients of the field amplitude may exhibit atypical behaviour, with the real or imaginary parts being much larger than one or even unbounded. In this study, we analyse this phenomenon in several simple optical configurations, including dielectric-metal interfaces, surface-plasmon-resonance prism couplers, plasmonic microcavities, step-index slab waveguides and prism-coupled waveguides. We demonstrate that these large amplitude coefficients naturally arise from extending reflection and transmission coefficients to evanescent or damped waves. On the other hand, they are not directly associated with measurable reflectance or transmittance and, therefore, do not conflict with energy conservation. Instead, they provide a useful formal description of resonant field enhancement, modal excitation and coupling processes in plasmonic and dielectric optical systems.
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Biological Physics

Stochastic First-Passage Theory of HIV Viral Rebound Following Latent Reservoir Reactivation

Mesfin Asfaw Taye

In our earlier work, we modeled the stochastic initiation of HIV rebound by treating latent-cell reactivation as a Poisson-driven process during antiretroviral-therapy (ART) washout, immune modulation, and therapeutic perturbation~\cite{Taye2025CM}. That framework characterized activation survival, cumulative hazards, waiting-time laws, and expected viral-load trajectories. However, the endpoint observed in analytical treatment interruption (ATI) studies is not the hidden time of first successful reactivation. It is the first time at which plasma virus exceeds an assay-defined detection threshold. Here we reformulate post-treatment rebound as a stochastic first-passage problem, with $T_{\rm reb}=\inf\{t\ge t_w:V(t)\ge V_{\rm det}\}$. Successful reactivation events arrive with a time-dependent intensity, and each event seeds an exponentially expanding viral lineage. The total plasma viral load is therefore a Poisson shot-noise process, and rebound corresponds to its first threshold crossing. In the rare-reactivation regime, this crossing is dominated by the earliest successful lineage. Rebound timing then separates into two components: a stochastic waiting time for reservoir reactivation and a deterministic growth delay to detectability. This separation gives a shifted-hazard survival law and yields closed-form rebound-time distributions for constant activation, ART-washout-dependent activation, immune-periodic activation, Cox-process activation, and heterogeneous-reservoir activation. The same formulation also provides a likelihood suitable for the interval-censored sampling structure of ATI trials.
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Plasma Physics · Cross-listed from astro-ph.CO

Collisionless damping of the gravitational instability in fuzzy dark matter: spectral shape and quantum-to-thermal crossover

Yosuke Matsumoto, Kohji Yoshikawa and Naoki Yoshida

We present a quantum-kinetic linear theory of the gravitational instability in the context of fuzzy dark matter universe. Starting from the Wigner transport equation, we apply Landau's approach to the linearized Wigner–Poisson system and derive a kinetic dispersion relation that incorporates quantum effects exactly by introducing the plasma dispersion function. The growth rate as a function of wavenumber is characterized by a dimensionless quantum-to-thermal ratio $\alpha = k_{\mathrm{qJ}}/k_{\mathrm J}$, where $k_{\mathrm{qJ}}$ and $k_{\mathrm J}$ represent the quantum and thermal Jeans wavenumbers, respectively. We derive an analytic expression for the spectral slope at the cutoff wavenumber, revealing that the spectral shape undergoes a sharp transition across $\alpha \sim 0.5$. This implies a crossover from a thermally dominated kinetic regime, in which collisionless damping occurs via phase mixing and Landau resonance, to a regime dominated by quantum pressure. By applying these results to fuzzy dark matter, we show that the cutoff scale and its spectral shape depend sensitively on both the particle mass and the initial velocity dispersion, suggesting a method for simultaneously constraining these parameters through observations of the matter power spectrum. This framework provides a theoretical basis for future studies on the transition from early-phase thermal states to the formation of Bose-Einstein condensates in galactic structures.
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Optics

Ultra-high-speed line-scan Raman imaging

Qingyi Wu, Xusheng Tang, Francesco Masia et al. (+7 more)

Raman spectroscopic imaging has emerged as a potent tool due to its non-invasive nature and capability for chemical composition analysis. Line-scan Raman spectroscopy accelerates imaging speed by two orders of magnitude compared to point detection Raman methods. However, further enhancements in imaging speed were constrained by the readout speed of typically used charge-coupled device (CCD) spectroscopic detectors. We developed an ultra-fast line-scan Raman imaging technique based on recently available complementary metal-oxide-semiconductor (CMOS) detectors with low cost and read noise, and fast readout during exposure combined with a global shutter. Employing a high-efficiency transmissiongrating imaging spectrometer, we demonstrate imaging speeds up to two orders of magnitude faster than traditional line scan Raman imaging techniques and up to four orders of magnitude faster than point scan Raman methods, achieving Raman imaging up to 80 kHz spectral rate. We demonstrate that this technology is applicable to a variety of samples, including microplastics, biological cells, and tablets, creating images in an extremely short time frame, showcasing exceptional detection capabilities and the ability to reveal detailed information.
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All authors Qingyi Wu, Xusheng Tang, Francesco Masia, Peng Liang, Hao Peng, Lindong Shang, Yuntong Wang, Yue Qu, Wolfgang Langbein, Bei Li

Chemical Physics

Anomalous Peak Formation in the Second Stability Zone of Quadrupole Mass Filters: Role of Non-linear Resonances Induced by Single Rod Defects

Archisman Sinha, Pintu Mandal and Nabanita Deb

Operating a quadrupole mass filter (QMF) within its second stability zone offers superior mass resolving power but introduces extreme sensitivity to structural imperfections. While symmetric misalignments are well-documented, this work combines analytical modeling with SIMION trajectory simulations to investigate the unaddressed electrodynamic impact of a completely localized, asymmetric defect on a single rod. Unlike diagonally symmetric perturbations, which reduce the four-fold rotational symmetry to two-fold symmetry while maintaining a smooth stability landscape, a single-rod defect breaks the remaining symmetry, giving rise to pronounced transmission ridges within the second stability zone. Spatial multipole expansion reveals that this structural breakdown injects odd-parity harmonics – dominated by the hexapole A3 field – which couple the orthogonal transverse equations of motion. By tracking secular indices through explicit zone-II Floquet projection mappings, we demonstrate that these asymmetric fields drive destructive, higher-order nonlinear secular resonances. Ions traversing these precise parametric coordinates undergo rapid amplitude growth and collide with adjacent electrodes, establishing critical geometric tolerance frameworks and operating conditions for high-performance mass spectrometry.
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Physics and Society

Bursty Arrivals, Smooth Sojourns: Non-Poissonian Temporal Dynamics in a Logistics Warehouse

Alfonso de Miguel-Arribas and Yamir Moreno

Warehouses are central nodes in logistics networks: they buffer material flows, synchronize heterogeneous actors, and absorb temporal mismatches between inbound and outbound operations. Yet most warehouse analyses still rely on aggregate performance indicators or on queueing assumptions in which event timing is stationary and approximately memoryless. Here we use one month of high-resolution pallet-level data from a large Spanish warehouse to characterize arrivals, departures, and outbound residence times from a statistical-physics perspective. Inter-arrival and inter-departure times are strongly heterogeneous and compatible with heavy-tailed, non-Poissonian behavior, whereas outbound sojourn times are more naturally described by a log-normal distribution, suggesting constrained service mechanisms with a characteristic operational scale. Disaggregation by logistics flow reveals systematic differences in burstiness, memory, and distributional similarity. A renewal-based aging analysis uncovers recurrent weekly accumulation and clearance cycles in the outbound buffer zone. Finally, a Little's-Law-inspired activity–sojourn scaling identifies two operational regimes: a near-linear baseline under regular turnover and a reproducible off-baseline branch associated with weekend accumulation and Monday dispatches. These results provide a compact diagnostic framework for temporal complexity in warehouse operations and show how limited but high-resolution industrial data can reveal operational structure invisible to aggregate throughput statistics.
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Plasma Physics

Deep Learning Models for ADITYA-U MHD Equilibrium

Udaya Maurya, Suman Aich, Indranil Bandyopadhyay et al. (+1 more)

This work presents deep learning models to predict magnetohydrodynamic equilibrium parameters and profiles for the ADITYA-U tokamak. A synthetic free-boundary equilibrium dataset consisting of 100,760 cases was generated using the pyIPREQ Grad-Shafranov solver, with inputs derived from 766 ADITYA-U plasma discharges and constrained to experimentally relevant circular limiter plasmas near the flat-top phase. Several deep learning approaches were investigated for predicting scalar equilibrium quantities, one-dimensional safety factor profiles and two-dimensional poloidal flux profiles. These approaches included Dense neural networks, principal component analysis based reduced-order models, one-dimensional and two-dimensional convolutional neural networks, and physics-informed neural networks incorporating Grad-Shafranov residual constraints. In addition, an inverse model was developed to estimate poloidal field coil currents from desired plasma equilibrium conditions. The results demonstrate that key equilibrium parameters and profiles can be accurately estimated within the operational domain represented by the dataset. The developed models provide a computationally efficient alternative to conventional equilibrium estimation and can be useful for real-time plasma control, rapid equilibrium analysis, and experimental planning in ADITYA-U operations.
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All authors Udaya Maurya, Suman Aich, Indranil Bandyopadhyay, Daniel Raju

Instrumentation and Detectors

Red Pitaya DAQ for fast neutron detection: a scalable, compact and low-cost solution

Dzmitry Kazlou, Roman Bergert, Hans-Georg Zaunick et al. (+1 more)

In this work, we present the initial results of a compact fast-neutron detection system based on the EJ-276D plastic scintillator, a dual-channel readout using two silicon photomultipliers (SiPMs) with complementary cell geometries, and a data acquisition (DAQ) system built on the StemLab Red Pitaya FPGA platform. The system combines the pulse shape discrimination (PSD) capability of EJ-276D with custom, cost-effective analog front-end electronics and open-source DAQ firmware. Unlike traditional systems relying on bulky photomultiplier tubes or liquid scintillator detectors, our design is portable and scalable. It achieves a Figure of Merit of 1.61 in the 2.75–3.0\,MeV$_{ee}$ energy range, comparable to established setups, while requiring only a single +5\,V USB power source. The results demonstrate the potential of this approach for in-situ neutron detection in mixed radiation fields, with the FPGA programmability of the Red Pitaya enabling straightforward adaptation to diverse academic and industrial applications.
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All authors Dzmitry Kazlou, Roman Bergert, Hans-Georg Zaunick, Kai-Thomas Brinkmann

Biological Physics

Relativistic PBTE:Biological Proper Time Along the Worldline

Mesfin Asfaw Taye

Biological aging is conventionally indexed by chronological time, yet every organism is a physical system tracing a worldline through spacetime, so the time available to its metabolism is not coordinate time $t$ but relativistic proper time $\tau$. Building on the established Principle of Biological Time Equivalence (PBTE), whose thermodynamic foundation and aging dynamics are taken here as prior results \citep{TayeBook2026,TayeAging2026,TayeCardiac2026}, we ask how internal physiological time relates to the proper time of physics. The central result is that biological age is an entropy-production functional evaluated along the proper-time worldline, \begin{equation*} A_PBTE=\frac{1}{\Sigma_ref}\int_{\tau_0}^{\tau_1}\dot\Sigma_p(\tau)\,d\tau, \qquad \frac{dA_PBTE}{dt}=\frac{\dot\Sigma_p}{\gamma\,\Sigma_ref}, \end{equation*} where $\dot\Sigma_p$ is entropy production per unit proper time in the local rest frame and $\gamma$ the Lorentz factor.
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Instrumentation and Detectors

A CubeSat Electronics System for Dual-Satellite Coordinated Soft X-Ray Polarimetry

Lirong Xie, Shiqiang Zhou, Kai Chen et al. (+12 more)

Addressing the unique requirements for a wide field of view and rapid response in soft X-ray polarization measurements of transient sources such as gamma-ray bursts, this paper proposes the design of a high-reliability CubeSat payload electronics system for dual-satellite cooperative observation. The system employs a Gas Microchannel Pixel Detector (GMPD) and a Topmetal-L sensor as its core components, forming a highly integrated, low-noise payload hardware platform. It achieves a field of view of 90$^\circ$ $\times$ 90$^\circ$, a sensitive area of 3.69 cm$^{2}$, and a power consumption of less than 6 W, operating within an energy range of 2–10 keV. The system incorporates autonomous high-voltage (HV) ramp-up/ramp-down control and a dual-protection mechanism based on count rate and discharge events, enabling in-orbit responses to risks such as the South Atlantic Anomaly and solar particle events. It also supports single-event upset detection and recovery, as well as in-orbit firmware upgrades. The communication interface adopts a redundant primary/backup Controller Area Network (CAN) bus design, with measured channel switching times of less than 100 ms, meeting the demands for real-time command interaction in dual-satellite coordination. By utilizing a large-array pixel sensor with region-of-interest readout and integrating an in-orbit track compression algorithm, the system significantly reduces data storage and downlink transmission resource burdens. Ground tests demonstrate an equivalent noise charge of 22.35 e$^{-}$, HV monitoring linearity better than $\pm$0.5%, and an output range extending to -5 kV. Thermal vacuum cycling tests show no performance degradation after five cycles between -5 $^\circ$C and 40 $^\circ$C. This work demonstrates the system's capability for autonomous observation, intelligent coordination, and reliable operation in complex space environments.
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All authors Lirong Xie, Shiqiang Zhou, Kai Chen, Zuke Feng, Difan Yi, Ran Chen, Ruinan Fan, Cheng Lian, Ziyi Zhang, Siying Liu, Dong Wang, Xiangming Sun, Enwei Liang, Huanbo Feng, Hongbang Liu

Chemical Physics

Combinatorial Compression in Nucleobase Self-Assembly Governed by Seeding Kinetics

Yael Kapon, Rotem Edri and Moran Frenkel-Pinter

Crystallization from chemically complex mixtures is governed not only by thermodynamic stability but also by kinetic competition among structurally related components during nucleation and growth. When multiple compatible molecules compete for incorporation into early nuclei, the number of possible local recognition motifs can expand, delaying access to productive crystalline pathways. Here, we investigate this effect using supersaturated aqueous mixtures of the canonical nucleobases adenine (A), thymine (T), and uracil (U) as a minimal model for competitive supramolecular crystallization. Time-resolved turbidity measurements showed that ternary A+T+U mixtures crystallize more slowly and less efficiently than selected binary systems, despite containing individually crystallizable components. This inhibition is consistent with competition-induced kinetic frustration, where structurally similar hydrogen-bonding partners compete during early nucleation, delaying formation of a productive crystalline nucleus. We then show that preformed A+T crystalline seeds rescue ordered growth from the ternary mixture. Seeding sharply reduces the lag time, increases the apparent nucleation/onset rate, and redirects the solid product toward the A+T crystalline pathway, as confirmed by HPLC. Thus, the seed acts not only as a nucleation accelerator but as a selector of molecular composition and assembly trajectory within a multicomponent solution. We describe this process as kinetic compression: the reduction of accessible supramolecular assembly pathways through amplifications of selected productive growth pathways. These findings establish seeded crystallization as a mechanism for selecting compositional pathways in competitive molecular mixtures and suggest a physical route by which ordered molecular subsets can emerge from chemically complex environments.
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Chemical Physics

Hidden Gauge Freedom in Complex-Pole Hierarchical Equations of Motion

Tianchu Li and Andrés Montoya-Castillo

While complex-pole hierarchical equations of motion (HEOM) have dramatically expanded the reach of numerically exact quantum dynamics simulations of open quantum systems, they suffer from numerical instabilities rooted in the non-Hermitian structure of their Liouvillian. Yet, the origin of this structure remains obscure. Here, we report a previously unknown gauge freedom in complex-pole HEOM: a continuous family of analytically equivalent Liouvillians, all encoding the same bath correlation function, whose numerical properties vary dramatically. This gauge controls both the eigenspectrum and non-normality of the hierarchy generator, revealing spectral divergence and non-normal error amplification as two distinct instability mechanisms. By optimizing this gauge, we introduce GO–HEOM, which eliminates divergences in strongly coupled Brownian oscillator environments and extends numerically exact simulations of sub-Ohmic dynamics – including through the delocalized-to-localized quantum phase transition – to previously inaccessible coupling strengths. Because this gauge transformation is independent of the bath-correlation decomposition scheme, our GO–HEOM becomes a general, broadly compatible strategy for accessing numerically exact quantum dynamics of open quantum systems over arbitrary coupling and highly non-Markovian regimes.
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Biological Physics

Biological Time, Evolutionary Optimization, and Gauge Coherence: A Thermodynamic Synthesis of the Principle of Biological Time Equivalence

Mesfin Asfaw Taye

Biological theory usually treats time as an external chronological variable against which growth, aging, and ecological change are parametrized. Yet living systems also generate an internal measure of duration through physiological cycling and irreversible entropy production, and the regularities of allometric lifespan scaling, biological clocks, life-history evolution, ecological synchronization, and disease are ordinarily studied in isolation rather than within a single thermodynamic internal-time framework. The Principle of Biological Time Equivalence (PBTE) proposes such a framework.
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Atomic Physics

Hydrogenic rotational levels with spin-0 or spin-1/2 constituent particles

Vojtěch Patkóš, Mateusz Pańtak and Krzysztof Pachucki

We employ nonrelativistic quantum electrodynamics with a unified description of two-body systems with spin-0 or spin-1/2 constituents, arbitrary masses, and arbitrary magnetic moments in rotational states with $L>1$, to present state-of-the-art theoretical predictions for muonic, kaonic, and antiprotonic atoms that have recently been measured or are targeted by upcoming experiments. We show that the theoretical accuracy can further be improved, opening the possibility of using precision spectroscopy of muonic and hadronic atoms for high-accuracy determinations of nuclear charge radii and nuclear electric dipole polarizabilities, and for testing the existence of hypothetical long-range hadronic interactions.
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Chemical Physics

Resolving the inverse problem in pulse response analysis of TAP reactors

Anjali Aleria, Evgeniy Redekop, A. K. Suresh et al. (+1 more)

Pulse experiments in the temporal analysis of products (TAP) reactor are one of the most important methods for studying transient kinetics of gas-solid catalytic reactions. The Y-procedure (Yablonsky et al., Chem. Eng. Sci. 62, 6754, 2007) is a model-free analysis framework for inferring the relationship between the reaction-rate $R$ and the reactant concentration $C$ from measurements of the outlet flux of gas. While elegant in conception, its application is hindered by the amplification of measurement noise that results from having to backtrack diffusive transport from the outlet to the reaction zone. Here, we explicitly recognize the inverse problem inherent in the Y-procedure and treat it using well-developed tools from the field of inverse problems. While previous implementations of the Y-procedure used Fourier-based filtering, we do not pre-process the measurements with an ad hoc noise-filter. Instead, we use a basis of localized square pulses to formulate a discrete inverse problem, whose regularized solution is obtained via the truncated singular value decomposition (TSVD) method. This method requires one to select a cutoff mode number; while we show how the choice of this regularization parameter can be guided by a Picard plot, we also develop an objective selection strategy for state defining experiments, for which $R(C)$ is a single-valued function. We apply our proposed inverse-problem approach to synthetic data corresponding to linear and nonlinear reactions and compare the results with the Fourier-filtration method. The former produces better reconstructions of the $R$ vs $C$ relationship, especially for nonlinear reactions. Our work facilitates the automation of pulse response analyses and enables the application of other discrete inverse-problem techniques, such as Tikhonov regularization or machine-learning methods.
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All authors Anjali Aleria, Evgeniy Redekop, A. K. Suresh, Jason R. Picardo

Plasma Physics

On the electromagnetic effects of collisionless trapped-electron modes

Yao Yao, Haotian Chen, Yang Chen et al. (+2 more)

We present a linear gyrokinetic theory for the electromagnetic collisionless trapped-electron mode (CTEM). It is found that the weak electromagnetic effects of CTEMs originate from the particle dynamics. Theoretical analysis reveals that the kinetic and fluid-like components of the trapped-electron parallel current cancel at leading order. The ion parallel current is also negligible due to the weak ion transit resonance. Consequently, the perturbed parallel current in the electromagnetic CTEM is dominated by passing electrons. We demonstrate that these characteristics of particle dynamics decouple the CTEM from the shear Alfvén wave branch, rendering the electromagnetic effects subdominant. Both eigenmode analyses and gyrokinetic simulations validate these findings.
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All authors Yao Yao, Haotian Chen, Yang Chen, Jiquan Li, Xuru Duan

Applied Physics · Cross-listed from cond-mat.mes-hall

On the $\mathrm{In_{x}Ga_{1-x}As}$ channel noise in InP HEMTs from 4 K to 300 K

Junjie Li, Justin H. Chen, Austin J. Minnich et al. (+1 more)

The InP high-electron-mobility transistor (HEMT) is indispensable for low-noise amplifiers (LNAs) in radio astronomy and quantum computing. The composition of the $\mathrm{In_{x}Ga_{1-x}As}$ channel in InP HEMT is known to influence the LNA noise performance. However, the various physical mechanisms responsible for noise generation are not fully characterized and understood. Here, we investigate the $\mathrm{In_{x}Ga_{1-x}As}$ channel noise from 4 K to 300 K for 100-nm gate-length InP HEMTs with channel indium content of 53%, 60% and 70%. Channel noise was quantified by extracting the equivalent drain noise temperature $\mathit{T}_{d}$ using both on-wafer and LNA-based measurements, covering 40-300 K and 4-40 K, respectively. The 60% indium channel InP HEMT exhibited the lowest channel noise across the full temperature range. The $\mathit{T}_{d}$ extracted from on-wafer characterization was found to obey a parabolic temperature dependence which predicted the $\mathit{T}_{d}$ at 4 K for all InP HEMTs in good agreement with LNA-based measurements. By expressing the channel noise as the sum of one thermal and one excess noise term, it was found that the former increased linearly with ambient temperature and dominated at 300 K. The channel noise at 4 K was determined by the excess noise term and exhibited a non-monotonic dependence on the channel indium content in the InP HEMT. The results suggest that the excess noise in the InP HEMT originates not only from temperature-independent shot noise but also from impact ionization and real-space transfer noise.
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All authors Junjie Li, Justin H. Chen, Austin J. Minnich, Jan Grahn