Quantum Physics
Stabilizing temporal quantum-enhanced sensitivity via sub-optimal measurements
Wangsheng Zheng, Yaoling Yang and Abolfazl Bayat
In non-
equilibrium probes,
quantum-enhanced sensitivity is quantified through super-linear scaling of precision with respect to time, as a central metrology resource. However, this requires optimal measurements, which are often complex and time-dependent, making it challenging in practice. Sub-optimal measurements typically fail to retain robust super-linear scaling and show oscillations. Here, we begin by establishing a universal temporal scaling law in a general multi-parameter non-
equilibrium quantum sensing framework. Within this setting, we identify the universal behavior of the sensing precision with sub-optimal measurements which shows quadratic scaling modulated by an additional bounded oscillatory function. To remove the oscillatory part, we propose a protocol in which measurements are partitioned into different groups, each performed at different times. The collective precision obtained from this protocol stabilizes a robust quadratic scaling even for sub-optimal measurements in the multi-parameter regime. We validate our protocol through three distinct examples as well as
Bayesian estimation. Our protocol is applicable to every informative measurement and takes a key step towards practical realization of
quantum-enhanced sensitivity.
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Superconductivity
Interface engineering of spin triplet Cooper pairs for spin-valve implementation
Debashree Nayak, Abhisek Sahoo, Pratap Kumar Sahoo et al. (+1 more)
Spin singlet Cooper pairs can be converted into equal-
spin triplet pairs at a
superconductor/heavy-metal interface under suitable conditions. Under current carrying conditions, these triplet correlations can give rise to a non
equilibrium spin moment in the heavy metal through the predicted supercurrent
spin-
Hall effect. Here we demonstrate that this current induced triplet
spin moment, in conjunction with the
magnetic moment of a
ferromagnetic layer, can enable a
magnetic spin-valve response in Nb/Pt/Ni/Pt/Nb vertical nano-devices. The magnitude of this
spin-valve effect depends on the efficiency of singlet-triplet Cooper pair conversion at the Nb/Pt interface. In order to facilitate efficient triplet generation, we deliberately introduced interfacial roughness to introduce finite Rashba
spin-orbit coupling at the Nb/Pt interface and an out-of-plane component of
magnetic moment at the Ni interface. In contrast, no discernible
spin-valve response was observed in devices with smooth interfaces within measurement resolutions. Since the
magnetic moment of the Ni layer and the current-induced triplet
spin moment in the Pt layer are independently switchable using a
magnetic field and bias current, respectively, the
spin valve can be controlled via either parameters. These results demonstrates a novel approach to directly utilizing the
spin polarized triplet Copper pairs in superconducting spintronic applications.
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All authors Debashree Nayak, Abhisek Sahoo, Pratap Kumar Sahoo, Kartik Senapati
Optics
Collective cavity quantum electrodynamics in solid-state optical clocks
Karen Mamian, Georgy A. Kazakov, Thorsten Schumm et al. (+1 more)
Solid-state frequency standards are generally limited by strong decoherence, rendering conventional interrogation schemes inefficient. The $^{229}$Th
nuclear clock provides a unique and timely platform for solid-state optical metrology and
nuclear cavity
quantum electrodynamics (QED), featuring a coherence time many orders of magnitude shorter than the radiative lifetime in current experiments. Here, we propose and analyze three cavity QED-enhanced clock interrogation schemes that turn this timescale mismatch into an advantage, leveraging collective coupling of thorium
nuclei to nanophotonic modes to enable fast interrogation and detection despite the long population lifetime. We reveal the central role of collective cooperativity in determining the clock frequency instability, and derive the optimal conditions (power, working-point detuning, thorium density) for clock operation.
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All authors Karen Mamian, Georgy A. Kazakov, Thorsten Schumm, Charles Roques-Carmes
Optics
Non-Hermitian mode locking in an L-band monolithic InP dual-ring laser
Xiao Sun, Mohanad Al Rubaiee, Jue Wang et al. (+4 more)
Coupling between
laser cavities provides a means of controlling optical modes through their gain, loss, and hybridization. Here we demonstrate electrically controlled mode locking in a monolithic InP dual ring
laser operating in the L band without a dedicated saturable absorber. Independent biasing of the two rings accesses single mode emission, mode locking, and hybridized supermode operation, with a measured intermode beat frequency of 542 MHz in the latter regime. The
laser generates 7.9 ps pulses at 18.11 GHz. A coupled cavity model describes how differential nonlinear detuning modifies the modal gain loss contrast, and time domain simulations yield pulse durations and spectral widths close to those measured experimentally. In a device incorporating saturable absorbers, reverse bias enables 3.1 ps pulses and reduces the integrated timing jitter from 9.06 to 2.46 ps relative to the unbiased condition. These results connect electrical control of coupled-cavity states with picosecond pulse generation in a monolithic InP
semiconductor platform for high repetition rate optical communications and microwave photonics.
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All authors Xiao Sun, Mohanad Al Rubaiee, Jue Wang, John H. Marsh, Stephen J. Sweeney, Anthony E. Kelly, Lianping Hou
High Energy Physics (Experiment)
Goodness-of-fit for multi-distribution neutrino cross-section measurements with shared events
Francisco Martinez Lopez, London Cooper-Troendle, Steven Gardiner et al. (+2 more)
When multiple differential cross-section measurements are extracted from a common event sample, the same events contribute simultaneously to multiple distributions. This event-sharing structure imposes exact linear constraints among the bin counts, reducing the effective dimensionality of the measurement below the total number of bins. Since the covariance
matrix obeys these inter-distribution constraints, it contains a rank deficiency. While limited numerical precision may inadvertently restore invertibility, the $\chi^{2}$ contributions along constrained dimensions will be arbitrary, yielding unphysically inflated $\chi^{2}$ values in global goodness-of-fit tests. We present the range-projected $\chi^{2}$, a test statistic that restricts the goodness-of-fit test to the subspace carrying independent statistical information, yielding a $\chi^{2}$ with $N_\text{bins} - N_\text{null}$ degrees of freedom, where $N_\text{null}$ is the number of independent constraints. We show that this rank deficiency is a predictable consequence of the event-sharing structure, and that $N_\text{null}$ decomposes into a structural contribution determined a priori from the binning geometry and a kinematic contribution that depends on the phase-space occupancy. The method is validated with an analytical toy model and a simulated
neutrino–argon cross-section measurement including unfolding and multi-source systematic uncertainties.
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All authors Francisco Martinez Lopez, London Cooper-Troendle, Steven Gardiner, Patrick Green, Tanaz Mohayai
Quantum Physics
Observable-targeted variational quantum simulation of Hamiltonian dynamics
Leonardo Zambrano, Luciano Pereira and Antonio Acín
Standard variational
quantum simulation seeks to reproduce the
evolution of the full
quantum state, although many applications require only the expectation values of a few observables. We study a variational method for pure-state
Hamiltonian dynamics that updates
circuit parameters to reproduce the
evolution of selected expectation values. An exact error identity guides the choice of observables, motivating a construction based on repeated commutators of the target with the
Hamiltonian. For Pauli observables and Pauli-rotation
circuits, the update can be estimated without ancillary
qubits or controlled operations for overlap estimation. Across six- and ten-
qubit spin, fermionic, and molecular
benchmarks, the observable-targeted update extends the median time within the target-error tolerance compared with standard variational
quantum simulation with equal shot budgets. These results show that directing the variational update toward the target observable can extend accurate simulation without increasing the measurement cost per time step.
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History and Philosophy of Physics
The wavelength of light as Thomas Young invented it
Olivier Morizot
This paper documents Thomas Young's invention of a concept which he alternately refers to as the ”magnitude”, ”breadth”, ”interval” or ”length of an undulation” of light. First, the paper highlights that Young was first to link some concept of a wavelength to a theory of optics and to assign a precise value to this length for each component of the colour spectrum. Then, it sets out an explanation of how Young made up these values. Finally, it examines the reasons why Young introduced an optical wavelength into his theory of light, insofar as these reasons might in turn shed light on why he was first to do so.
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Materials Science
III-V antiphase boundaries are not generated by Si or Ge substrate step edges
Charles Cornet, Sreejith Pallikkara Chandrasekharan, Audrey Gilbert et al. (+7 more)
We critically review recent experimental and theoretical advances on the valence- and structure-mismatched heteroepitaxy of III-V
semiconductors on group-IV substrates. We examine key aspects including wetting behavior, atomic configurations at the hetero-interface, substrate passivation, and the stability of antiphase boundaries (APBs). By synthesizing these findings with pioneering studies, we propose a refined description of antiphase boundaries formation. Our analysis shows that hetero-interface formation is dictated by substrate terrace reconstruction, demonstrating that APBs are not generated at monoatomic step edges. This generalized III-V/IV growth framework provides new insights for the integration of III-V
semiconductors on group-IV platforms and, more broadly, for valence-mismatched heteroepitaxy.
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All authors Charles Cornet, Sreejith Pallikkara Chandrasekharan, Audrey Gilbert, Milan Silvestre, Rozenn Bernard, Pascal Turban, Gilles Patriarche, Eric Tournie, Laurent Pedesseau, Jean-Baptiste Rodriguez
Fluid Dynamics
A high-order ghost-point immersed boundary method coupled with auxiliary differential equations for time-domain impedance walls
Abdoulaye Ouattara
A ghost-point immersed boundary method is coupled with auxiliary differential equations to impose a locally-reacting impedance condition on a wall that does not conform to a Cartesian grid, in the framework of the linearized Euler equations. The ghost-point reconstruction follows the normal-stencil approach: an elliptical least squares cloud of fluid nodes is used to build a high-order
polynomial along the local wall normal, which is then extrapolated onto the ghost points by one-dimensional La grange interpolation. The impedance, modeled as a massspringdamper oscillator, is advanced in time through two auxiliary state variables per ghost point, coupled to the reconstruction at every RungeKutta stage. The method is validated against exact and semi-analytical references on a flat immersed wall, a cylindrical wall reflecting an acoustic pulse, and a cylinder scattering a harmonic monopole. Convergence orders ranging from about three on the curved wall to about four and a half on the flat wall are measured, and a cross-check against an exact harmonic reference shows that a persistent offset observed against a semi-analytical reference is a property of that ref erence rather than of the coupled solver. A spectral stability analysis of the linearized semi-discrete operator further shows that the normal-stencil reconstruction reduces, without eliminating, a known instability that occurs when the immersed wall becomes tangent to the grid.
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High Energy Physics (Phenomenology)
Comparative Study of Color Glass Condensate and Collinear Frameworks for Large-Transverse-Momentum Semi-Inclusive Deep Inelastic Scattering
Swagato Mukherjee, Björn Schenke and Shaswat Tiwari
We study the Semi-Inclusive Deep Inelastic Scattering (SIDIS) cross-section at large values of
hadron transverse momentum $P_t \gtrsim Q$, with $Q^2$ being the
photon virtuality. This kinematic regime of SIDIS allows for a collinear factorization in terms of parton distribution functions (PDFs) and collinear fragmentation functions (FFs). On the other hand, at high energies, i.e., at small Bjorken $x$, the same SIDIS process can also be factorized within the Color Glass Condensate (CGC) framework in terms of eikonal dipole amplitudes. In this work, we perform a systematic comparison of the leading-order (LO) and next-to-leading-order (NLO) collinear and the LO CGC factorizations of this process based on the COMPASS and HERA data. We further provide comparisons of these two factorization frameworks for nucleon and
nuclear large-$P_t$ SIDIS in the expected Electron Ion
Collider (EIC) kinematics. We find, within the present theoretical uncertainties, that it might be difficult to distinguish between these two factorization schemes for
nuclear SIDIS at the EIC. We also observe a significant dependence of the LO eikonal CGC predictions on the choice of longitudinal momentum fraction $x_g$, suggesting significant beyond-eikonal corrections for the EIC kinematics.
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Mathematical Physics
Batalin-Vilkovisky algebras from Ševera bicomplexes
Eugenia Boffo and Domenico Fiorenza
A Ševera bicomplex is a bicomplex $(M,d_{0},d_{1})$ whose differentials $d_{i}$ are Grothendieck differential operators of order $\leq i$ with respect to a given $A$-module structure on $M$, where $A$ is a graded commutative
algebra. One also requires that $(M,d_{0})$ admits a contracting homotopy $K$ that is a differential operator of the same order as $d_{0}$. Under suitable assumptions, the differential $d_{2}$ of the second page of the spectral sequence associated with $(M,d_{0},d_{1})$ is a Batalin-Vilkovisky operator on $E_{2}$, so that when $E_{2}$ is a free rank 1 $A$-module, the graded commutative
algebra structure of $A$ is enhanced to a Gerstenhaber
algebra structure, and the choice of a $d_{2}$-closed basis element for $E_{2}$ further enhances this to a Batalin-Vilkovisky
algebra structure. The prototypical example of this construction is Ševera's description of the Batalin–Vilkovisky
algebra structure on the
algebra of smooth functions of an odd
symplectic manifold. Throughout the whole article we look at Batalin-Vilkovisky
algebras through the lenses of Cartan calculus. Indications of a generalization to derived Cartan calculus are briefly discussed in the concluding section.
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Optics
Broadband Single-Particle Absorption Circular Dichroism Reveals Chiroptical Heterogeneity in Gold Helicoids
Rohit B. Raj, Susanna Bertuletti, Jeong Hyun Han et al. (+7 more)
Quantitative measurements of absorption circular dichroism (CD) at the single-particle level are essential for understanding how individual
chiral nanostructures dissipate optical energy, yet broadband absorptance measurements remain experimentally challenging. Here, we introduce a wavelength-tunable integrating-sphere microscope that determines the absorptance of individual nanoparticles under right- and left-circularly polarized illumination through direct optical energy balance, enabling broadband measurement of the absorption dissymmetry factor, gabs. Measurements of achiral gold nanospheres and strongly anisotropic gold nanorods establish the apparent absorption CD baseline and demonstrate minimal detectable linear-dichroism-to-circular-dichroism (LD-to-CD) leakage under the experimental conditions. Applying this approach to 87
chiral gold helicoids synthesized using L-glutathione (L-helicoids) and 96 synthesized using D-glutathione (D-helicoids) reveals mean particle-level gabs values of opposite sign, with a statistically significant difference between the two populations. Individual particles nevertheless exhibit pronounced heterogeneity in response sign, magnitude, spectral position, and line shape. More than one-third of the particles in each population display opposite-sign absorption CD responses relative to their population-average tendency. Correlative SEM analysis of the L-helicoid population further shows that opposite-sign responses persist among isolated particles exhibiting the characteristic projected helicoid morphology, indicating that aggregation and gross differences in projected morphology are insufficient to explain the observed heterogeneity. These results establish broadband single-particle absorption CD spectroscopy as a direct probe of absorptive chiroptical heterogeneity and reveal particle-specific responses obscured by ensemble averaging.
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All authors Rohit B. Raj, Susanna Bertuletti, Jeong Hyun Han, Sepin Cho, Debapriya Pal, Nick Feldman, Ki Tae Nam, Willem L. Noorduin, A. Femius Koenderink, Erik C. Garnett
High Energy Physics (Phenomenology)
Impact of nuclear shell model uncertainties on silicon and germanium WIMP-nucleus limits
M. J. Zurowski and R. Abdel Khaleq
Dark matter (DM) direct detection searches look for
nuclear recoils as a result of weakly interacting massive particles (WIMPs) scattering off
nuclei. Calculating the rate associated with this WIMP-
nucleus elastic scattering process involves input from several components, which include the direct detection experimental response functions, the high energy physics content employed, the DM
halo velocity distribution, and the target
nuclear structure information. Uncertainties in any of these components can impact the interpretation of experimental signals, and affect analysis of rate predictions. In this work, we focus on the uncertainties present due to the
nuclear structure modelling of silicon and germanium targets, where a comprehensive set of
nuclear form factors are employed through a non-relativistic effective field theory (NREFT) formalism. We show that these uncertainties, obtained from large-scale shell model calculations, impact the
nuclear form factors and thus experimental exclusion limits for a SuperCDMS-like experiment. The impact of high energy physics content (through particle physics coefficients) on the magnitude of the
nuclear uncertainties is also explored for several WIMP-
nucleus scattering responses. Non-negligible
nuclear uncertainties are present for several direct detection
nuclear responses, indicating that
nuclear structure must be accounted for in experimental analysis and interpretation.
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Nuclear Theory
Flow plus coalescence explain hadron nuclear modification and high-$p_T$ anisotropy
Wilke van der Schee and Isobel Kolbé
It has long been a puzzle why the
nuclear modification factor in relativistic $p$Pb collisions is consistent with unity, while the high-$p_T$
elliptic flow is significantly positive. The latter is traditionally interpreted as path-length-dependent energy loss, whereas the former is consistent with zero energy loss. In this Letter, we propose that even at high $p_T$ a hard parton coalesces with a boosted thermal medium parton whose energy is correlated with the angle-dependent radial flow. We compare this flow for $pp$, $p$Pb, $p$O, OO and PbPb collision systems and conclude in particular that the $p$Pb flow is large and anisotropic. The collective medium pushes out the hard partons, and more so in $p$Pb, or in-plane, than in $pp$ collisions, or out-of-plane. The mechanism qualitatively agrees with experiment and predicts a significantly smaller
elliptic flow signal for jets than for
hadrons.
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Quantum Physics
Superconducting qubit based on altermagnets
Xue-Feng Pan, Xin-Lei Hei, Franco Nori et al. (+1 more)
Altermagnets, characterized by vanishing net magnetization and momentum-dependent
spin splitting, provide a promising platform for next-generation Josephson devices. Here, we exploit the Josephson effect in
superconductor-altermagnet-
superconductor junctions and show how to engineer prescribed current-phase relations by device design. Based on these programmable Josephson potentials utilizing altermagnetism, we propose a new class of superconducting
qubits that combine large anharmonicity with enhanced robustness against decoherence via coherent two-Cooper-pair tunneling. We show that in the $2\phi$-junction regime, this kind of
qubit is intrinsically protected against both charge and flux noise due to parity protection.
Magnetic flux can be used to precisely control the
qubit and, under appropriate bias, this architecture further suppresses charge and flux noise. Our results establish altermagnets as a versatile platform for Josephson-potential engineering and open a new route toward high-performance superconducting
qubits combining high coherence, large anharmonicity, and broad tunability.
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All authors Xue-Feng Pan, Xin-Lei Hei, Franco Nori, Peng-Bo Li
Chaotic Dynamics · Cross-listed from cs.LG
Inference of Unknown Dynamical Components Using Next Generation Reservoir Computing: From Chaotic Systems to Climate Data
Jule Budnick, Andrew Keane and Serhiy Yanchuk
We investigate next generation reservoir computing (NGRC) as a data-driven approach for inferring unseen components of dynamical systems. We compare NGRC with traditional reservoir computing (RC) using the Lorenz and Rössler system, where two unknown components are inferred from one given component. For both systems, NGRC achieves accurate results while requiring fewer training data and less computational time than RC. We identified an inverse proportional behavior between the number of time-delayed steps needed for NGRC and the temporal resolution, indicating that the physical time span covered by the delay interval is an important factor in determining the required number of delayed steps. Finally, we apply NGRC to the observational
climate data of ENSO (El Niño–Southern Oscillation) and infer one observable from the remaining variables. Despite the noise and complexity of the real-world data, the NGRC shows promising results. Our findings demonstrate the potential of NGRC for efficient inference of unseen components in both controlled dynamical systems and real-world data.
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Statistical Mechanics
Optimal probing scale for current fluctuations in a Brownian gyrator
Badr Farih
A driven colloidal rotor sustains a circulating current whose fluctuations one would like to bound. Any such bound rests on how strongly the current responds to a perturbation and on how much extra dissipation that perturbation costs, so there is a well-posed question of where to push: the response per unit Onsager-Machlup cost depends on the radius at which the probe acts, and is maximised at a definite one. We answer this for the Brownian gyrator and a quadrupolar shear under a Gaussian envelope, a probe chosen so that linear response is exactly blind to it at every observation window, so that the entire signal is second order. The problem separates: the cost is radial and does not see the circulation, while the response lives in the $m=3$ angular sector, where the resolvent reduces to Kummer's equation with $b=4$ and the susceptibility is a hypergeometric function of the envelope width. Maximising the ratio gives the optimal probing radius in closed form. It is set by whichever of the system's two clocks is faster: for weak driving $r^*=1.1264\sqrt{D/\gamma}$, the thermal radius of the trap, and for strong driving $r^*=1.5563\sqrt{D/\Omega}$, the distance diffused in one radian of rotation, with the trap stiffness dropping out entirely. The crossover is at $\Omega=\gamma$. Both limits, and the prefactors, are confirmed against direct simulation.
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Instrumentation and Methods for Astrophysics
First Experimental Evaluation of Stray Light Noise Modeling of kilometers-long Beam Tube Arms of Gravitational Wave Detectors
Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto et al. (+3 more)
We present the results of the first experimental evaluation of stray light noise models for LIGO beam tube baffles. We combine the results of a testing campaign at LIGO Livingston and SIS simulations to get a model of backscatter and diffraction noise of select mid-arm baffles. Agreement to within a factor of $3-10$ is found between models and measured gravitational waHe strain. Two distinct regions of well-propagating motion were identified, at approximately $35Hz$ and $90Hz$, and these are visible in the strain signal as broadband features. Peaks with $Q \approx 100-1000$ were also found in the strain signal between $70Hz$ and$100Hz$. These are theorized to come from diffraction noise only, and are modeled using Q-factors measured from the strain. These models are also in good agreement with the strain signal. Other findings on the effect of auxiliary arm systems on stray light noise are discussed.
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All authors Emilia Chick, Timothy O'Hanlon, Hiro Yamamoto, Denis Martynov. Valery Frolov, Anamaria Effler, Antonios Kontos
Mathematical Physics · Cross-listed from math.AP
Counterexamples to Grad's conjecture
Javier Gómez-Serrano, Lukas Liehr and Mitchell A. Taylor
For each sufficiently large $N$, we construct smooth solutions of the magnetohydrostatic equations on embedded solid
tori whose regular pressure levels are nested
tori, whose
magnetic field vanishes exactly on a round
magnetic axis, and whose group of Euclidean
symmetries, even when isometries reversing the sign of the field are admitted, is exactly the cyclic group $C_N$ of rotations through multiples of $2\pi/N$. For each such $N$, these
equilibria form a smooth one-parameter family which is locally nontrivial in the
moduli space of embedded configurations and have none of the plane-reflection, axial, or helical
symmetries conjectured by Grad. A Lean 4 certification of the above results is also provided.
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Quantum Gases
From harmonic to sound-like oscillations in a quantum gas confined in a gravity compensated shell trap
Matthieu Cassus, Rishabh Sharma, Maxime Pesche et al. (+4 more)
We study the center of mass oscillations of a
quantum gas in a shell shaped trap in the presence of a vertical force opposed to
gravity. The measured harmonic frequency at the bottom of the shell is compared with an analytical formula for the trap potential including corrections beyond the rotating wave approximation. When
gravity is partially compensated, a quartic correction to the harmonic motion has to be included due to the shell
curvature. As
gravity is nearly canceled, the
quantum gas occupies a large fraction of the lower hemisphere. Driving the center of mass induces internal excitations in the
quantum gas, whose time
evolution is governed by the presence of sound waves. Relaxation processes induce a strong damping of the center of mass oscillation in this limit.
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All authors Matthieu Cassus, Rishabh Sharma, Maxime Pesche, Laurent Longchambon, Thomas Badr, Romain Dubessy, Hélène Perrin
High Energy Astrophysical Phenomena
Particle Acceleration in Stratified 2D MRI Turbulence: From Reconnection to First- and Second-Order Fermi and Shear Acceleration
Astor Sandoval, Mario Riquelme and Jorge Cuadra
Low-luminosity
accretion disks around black holes are weakly collisional, potentially enabling nonthermal particle acceleration. Local two-dimensional particle-in-
cell simulations of the stratified magnetorotational instability (MRI) in pair
plasmas by Sandoval et al. (2024; hereafter S24) revealed nonthermal populations with maximum energies proportional to the scale-separation ratio $\omega_{c,0}/\Omega_0$, where $\omega_{c,0}$ and $\Omega_0$ are the initial particle cyclotron and Keplerian frequencies, respectively. We identify the acceleration mechanisms involved and quantify their scale-separation dependence. Acceleration occurs primarily within large-scale current sheets associated with an MRI dynamo. Particles are initially injected by non-ideal electric fields during reconnection driven by plasmoid splitting, attaining energies independently of scale separation. They subsequently undergo rapid first-order
Fermi-like acceleration occurring within converging flows between newly formed, separating plasmoids. During this stage, energies grow at a rate proportional to the instantaneous non-relativistic cyclotron frequency, independently of $\omega_{c,0}/\Omega_0$. This fast acceleration rate implies a maximum energy proportional to $\omega_{c,0}/\Omega_0$. Particles then continue interacting repeatedly with plasmoids, undergoing slower, predominantly second-order
Fermi acceleration, with a subdominant contribution from shear acceleration. This stage increases particle energies by only a factor of a few over several orbits, regardless of $\omega_{c,0}/\Omega_0$. The combination of these three stages implies a maximum energy proportional to $\omega_{c,0}/\Omega_0$, explaining the scaling found by S24 and suggesting that the MRI may accelerate particles to ultrarelativistic energies in low-luminosity disks. Testing these results in three dimensions remains an important next step.
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Mesoscale and Nanoscale Physics
Observation of Kondo Effect in Rhombohedral Graphene Superlattices
Xin Liao, Qing Yin, Huiwen Wang et al. (+10 more)
Kondo effect in strongly correlated systems arises from the
antiferromagnetic coupling between itinerant conduction electrons and localized
magnetic moments, giving rise to a variety of exotic
quantum phenomena. Two-dimensional moiré superlattice systems provide a highly tunable platform featuring topological flat bands, where Wannier orbitals are spatially confined by the periodic moiré potential and serve as localized
magnetic moments, enabling the observable Kondo effect. Here we experimentally demonstrate Kondo interactions in hexalayer rhombohedral
graphene moiré superlattices through magneto-transport and temperature-dependent measurements. With increasing
magnetic field, the magnetoresistance exhibits an increase-decrease transition across a critical field B_c, while the
Hall resistance R_xy undergoes a sign reversal near B_c. Moreover, as temperature decreases, the longitudinal resistance R_xx first increases logarithmically and then decreases following a T^2 behavior, indicating a transition to heavy
fermion liquid. These behaviors can be consistently explained by the breakdown of Kondo singlets induced by either
magnetic field or temperature, which liberates carriers previously bound to localized moments, thereby enhancing conductivity and altering the dominant carrier type. Furthermore, our results demonstrate that the Kondo interaction can be continuously tuned by both carrier density n and displacement electric field D, and suggest the emergence of a Kondo insulating state. Our findings provide deep insight into the Kondo effect in moiré engineered flat-band systems, paving the path for exploring exotic correlated
quantum phases.
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All authors Xin Liao, Qing Yin, Huiwen Wang, Jing-Wei Dong, Jun-Xi Chen, Si-Li Wu, Cai-Zhen Li, Guowei Lyu, Kenji Watanabe, Takashi Taniguchi, Wei Jiang, Yu-Gui Yao, Zhi-Min Liao
General Relativity and Quantum Cosmology
Formalizing a unified dynamical system framework for $f(R)$ and $f(Q)$ gravity
Saikat Chakraborty
Going beyond the traditional Hubble-normalized framework, we formalize a unified dynamical system formulation for $f(R)$ and coincident gauge $f(Q)$
gravity using three distinct sets of dimensionless variables: (1) kinematical cosmographic parameters, (2) the dark energy equation of state parameter $w$ (with its $N=\ln a$ derivatives) and matter density abundance $\Omega_m$, and (3) theory space parameters $\{m_i\}$ characterizing the shape of the theory function. Our formulation is free of auxiliary variables, closing via three equivalent ways: (1) specifying a theory, (2) requiring a specific cosmological
evolution, or (3) requiring a specific dark energy equation of state
evolution. Each closure strategy is illustrated with explicit examples. The theory closure approach studies a case of Hu-Sawicki $f(R)$ and $f(Q)=-2\Lambda+Q+\beta\sqrt{-Q}$ models, where traditional formalisms fail. A heteroclinic trajectory from a GR-matter-dominated epoch to a late-time de-Sitter epoch is general for $f(Q)$, but sensitive to initial conditions for $f(R)$. The cosmographic and equation-of-state closure approaches compare $f(R)$ and $f(Q)$ gravities kinematically equivalent to $\Lambda$CDM ($j(z)=1$) and dynamically equivalent to $\Lambda$CDM ($w(z)=-1$). In both, GR acts as a cosmological past attractor for $f(Q)$
gravity, but not for $f(R)$.
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Fluid Dynamics
High-order immersed boundary method for subsonic aeroacoustics and compressible Navier-Stokes equationsHigh-order immersed boundary method for subsonic aeroacoustics and compressible Navier-Stokes equations
Abdoulaye Ouattara, David Marx, Christian Prax et al. (+3 more)
In computational fluid dynamics, the immersed boundary method is a classical technique to account for complex geometries when Cartesian grids are used, as is the case in finite difference methods. The present paper presents a new discrete ghost point method, which is one of the different immersed boundary methods available, for solving problems in acoustics and aeroacoustics with the linearized Euler equations or the compressible Navier-Stokes equations. This method is based on high-order schemes and a ghost point method. The flow field values at the ghost points are determined in two steps. A least-squares interpolation is first used to reconstruct the flow on a stencil of points located on the normal to the immersed boundary. Then, a 4th order Lagrangian extrapolation based on the normal stencil points adjacent to the boundary point is used to impose the boundary conditions at the immersed boundary by reconstructing the field values at the ghost points. This approach is verified and validated for the acoustical problem of a pressure pulse impinging on a cylinder. The approach is also validated for compressible flow past a circular cylinder at several Reynolds numbers.
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All authors Abdoulaye Ouattara, David Marx, Christian Prax, Véronique Fortunée, Manuel Diaz, Peter Jordan
Optics
Phase fields in momentum space of photonic crystal slabs
Chuanlin Li, Aobo Ren and Jiang Wu
Optical phase modulation is of great significant importance in fields such as optical communication, information processing, and precision measurement. Compared with real-space modulation, momentum-space phase modulation has distinct advantages: it is free from structural center constraints, supports unlimited mode capacity, and possesses intrinsic topological protection. This inherent flexibility and scalability allow practical applications systems to operate without stringent optical
alignment while providing a large number of independent control channels, thereby advancing the development of high-performance, highly integrated optical systems. Photonic
crystal slabs, with their open boundary periodicity and capabilities for momentum-space optical field manipulation, have become a crucial platform for research on momentum-space phase fields. Based on polarization orthogonal decomposition and the scattering
matrix within temporal coupled-mode theory, this paper systematically elucidates the generation mechanisms of both two-dimensional momentum-space phase fields, including phase
vortices, phase gradients, and phase difference, and multidimensional synthetic momentum-space phase fields in photonic
crystal slabs, and reviews recent research and application progress in this area. Finally, the development status, advantages, and possible breakthroughs in the field of momentum-space phase fields are summarized and prospects for future work are discussed.
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Astrophysics of Galaxies
CAVITY: Calar Alto Void Integral-field Treasury surveY: II. Second public data release
B. Bidaran, A. Jiménez, R. García-Benito et al. (+30 more)
Studying
galaxy evolution under the unique environmental conditions of
cosmic voids provides an opportunity to disentangle the role of the large-scale environment in shaping mass assembly (both baryonic and dark matter), regulating
galaxy physical properties, and driving the transformation from
star-forming to quiescent systems. We present the second public data release (DR2) of the Calar Alto Void Integral-field Treasury Survey (CAVITY), an ongoing legacy programme designed to study void
galaxies (VGs) across a range of nearby ($0.005 \leq z \leq 0.050$) voids with different sizes and dynamical stages, providing 200 science-grade optical integral-field spectroscopy (IFS) data cubes. By doubling the number of
galaxies relative to DR1 while maintaining the same selection criteria, DR2 significantly increases the
dataset's statistical power, enabling more robust characterization of
galaxy properties and their correlations with environment. The observations were obtained with the PMAS/PPAK spectrograph on the 3.5-m Calar Alto
telescope using the V500 configuration, covering the optical spectral range of 3745-7500 A at a resolution of 6 A (FWHM). The DR2 VG sample spans a broad range of
stellar masses, morphologies, colours, and gas ionisation properties. We describe the sample selection, observing strategy, data reduction pipeline, quality-control procedures, and the public access to the CAVITY
datasets and associated ancillary data on the survey's database. In addition, we present a characterisation of the large- and local-scale environments of CAVITY
galaxies, showing that the 15 surveyed voids encompass a wide variety of sizes,
galaxy richness,
galaxy populations, and local structures, including
galaxy groups. This release comprises 200 IFS data cubes, publicly available together with the master catalogues at the survey's dedicated webpage: https://cavity.caha.es/data/dr2/.
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All authors B. Bidaran, A. Jiménez, R. García-Benito, M. Argudo-Fernández, M. Alcázar-Laynez, S.B. De Daniloff, S. Duarte Puertas, D. Espada, E. Florido, Y. K. González-Koda, I. Pérez, T. Ruiz-Lara, L. Sánchez-Menguiano, G. Torres-Ríos, P. Vásquez-Bustos, S. Verley, A. Zurita, M. A. Canossa-Gosteinski, A. M. Conrado, H. M. Courtois, I. del Moral-Castro, J. Falcón-Barroso, A. Ferré-Mateu, M. Hernández-Sánchez, A. Lugo-Aranda, S. Subramanian, P. Villalba-González, L. Galbany, R. M. González Delgado, R. F. Peletier, S. F. Sánchez, R. van de Weygaert, A. Fernández-Martín
Medical Physics
A digital-twin framework for forecasting treatment-day imaging with contour uncertainty in adaptive proton radiotherapy
Yizhou Wu, Jie Ding, Justin Roper et al. (+6 more)
Head-and-neck anatomy changes over a six-to-seven-week
proton course, and the anatomy of a later week cannot be imaged when the plan is made. We present a digital-twin framework that forecasts a patient's treatment-day anatomy as an ensemble of predicted CTs with propagated contours and quantifies the uncertainty of the forecast contours. The twin is a library of previously treated patients with planning and weekly quality-assurance CTs (QACTs), made patient-specific by a two-step foundation-model deformable registration: a cross-patient field carries each library patient onto the current patient, and a longitudinal field, estimated in the current patient's frame, carries that patient's planning-to-QACT change onto the current patient's own planning CT. A library of 302 observations from 88 patients yields about 300 replicates per patient, each a deformation that occurred in a treated patient. The dispersion of the propagated contours, resolved by outward normal, is six-direction contour uncertainty in millimeters. This is uncertainty in the input to the forecast, which library patient the current patient follows, rather than in model parameters, and it is unchanged when the registration engine is exchanged. On ten patients with clinician contours on two QACTs, the library alone fixes the anisotropic shape of the uncertainty (4.5 to 6.2 mm); the first QACT narrows it by a factor of 3.2 to 3.6 without a contour being drawn; an approved contour improves the center but not the width. The estimate orders directions correctly but is not Gaussian-calibrated. A clinical target volume expansion is worked out as one application.
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All authors Yizhou Wu, Jie Ding, Justin Roper, Minglei Kang, Yuheng Li, Sibo Tian, David S. Yu, Xiaofeng Yang, Chih-Wei Chang
Solar and Stellar Astrophysics
The Role of Non-local Thermal Transport in Flare-Driven Chromospheric Evaporation
Thomas Parmenter, Tony Arber, Sergey Belov et al. (+1 more)
Thermal conduction plays an important role in energy transport during
solar flares.
Flares heat the
solar atmosphere to tens of MK which, combined with mean free paths in excess of 1Mm, can cause the heat flux to become non-local. We use the magnetohydrodynamic Lare2d code to simulate a reconnective heating event with three different thermal conduction models: classical Spitzer-Harm (SH) along the
magnetic field, local transport with a heat flux limiter (FL), and the non-local Schurtz, Nicolai, Busquet (SNB) model which is routinely used in
laser-
plasma codes and has been bench- marked against full Vlasov-Fokker-Planck treatment. The
evolution of the atmosphere post heating is compared between simulations using each of these models. Due to a supressed heat flux, SNB gives rise to significantly higher peak temperatures than SH. Further, with SNB transport chromospheric evaporation occurs later and has stronger extreme ultraviolet emission intensity. FL simulations have similar temperature
evolution and chromospheric evaporation to SNB, however different values of the flux limiter work best for peak temperature, downflow velocity and EUV emission intensity, and so there is no one optimal value for all cases. We conclude that the SNB model provides a practicable solution to incorporate non-local thermal transport at MHD scales, which will be crucial to improve the realism and accuracy of the next generation of
solar flare simulations.
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All authors Thomas Parmenter, Tony Arber, Sergey Belov, Tom Goffrey
Statistical Mechanics
Lowest-known Energy Configuration of $N=100\,000$ Coulomb Charges in a Disk: Breaking the $10^{5}$ Barrier
Georgiy K. Lavrov and Eduard G. Nikonov
We report the first calculation of the lowest-known energy configuration for $N=100\,000$ classical point charges confined to a disk and interacting via the $1/r$ Coulomb potential - a system size never before achieved for the Thomson problem in a disk, more than doubling the previous record of $N=40\,886$ reported by Amore and Zarate. An adaptive defect-targeting subdomain optimization strategy yields an approximately linear growth of the wall-clock time per cycle with $N$; for $N=100\,000$ a single $24$-core CPU workstation without GPU acceleration required $\approx31$ hours. The energy $E_{\min}=7.80466624157\times10^{9}$ deviates from the standard empirical asymptotic expansion by only $2.525\times10^{-7}$. We demonstrate that this remarkable agreement provides a stringent test of the rigorous next-order asymptotic theory for Riesz interactions, while the residual deviation is consistent with an $O(N^{4/3})$ boundary-layer correction whose absence from the standard fitting basis biases the empirical $N^{3/2}$ coefficient away from its exact crystalline value, thereby tying the deviation to the two-dimensional crystallization
conjecture. Bond-orientational order analysis reveals a polycrystalline bulk threaded by radial grain boundaries, establishing a new
benchmark for two-dimensional Coulomb systems.
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Strongly Correlated Electrons
Rapidly prototyping kagome flat band physics with acoustic metamaterials
Jiatong Yang, Benjamin H. November, Yiting Huang et al. (+3 more)
Flat bands with vanishing group velocity and quenched kinetic energy provide fertile ground for correlated states and exotic phenomena such as unconventional superconductivity. Yet, engineering and characterizing flat bands in
quantum materials is time-consuming and costly, limiting the exploration of the vast design space of possible flat band systems. Acoustic metamaterials offer an accessible alternative: they can be easily simulated, cheaply fabricated, and quickly measured. Here we present a complete workflow to rapidly prototype flat band systems using acoustic metamaterials. Our design directly implements a tight-binding model using air cavities as
lattice sites connected by channels that control hopping, allowing it to generalize to diverse
lattice geometries. Using the kagome
lattice as a proof-of-concept, we demonstrate excellent agreement between tight-binding theory, finite-element simulations, and experimental measurements. We then design a family of extended kagome
lattices whose added sites cancel successively longer-range hopping, flattening the flat band. With fabrication and measurement requiring hours rather than months and a total cost orders of magnitude lower than
quantum materials, our approach enables rapid iteration through candidate
lattices, facilitating the discovery of new flat band physics in
quantum materials.
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All authors Jiatong Yang, Benjamin H. November, Yiting Huang, S. Minhal Gardezi, Harris Pirie, Jennifer E. Hoffman