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Physics

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Tuesday 6 October

General Relativity and Quantum Cosmology

Natural Quenching of Inner Viscous Torques in Accretion Disks Around Mini-Boson Stars

Sandip Dutta

The standard Novikov-Thorne model for geometrically thin accretion disks assumes a zero-torque inner boundary condition at the innermost stable circular orbit (ISCO). Relaxing this assumption to allow a finite viscous torque—driven by magnetic stresses bridging the plunging region—can significantly enhance the radiative efficiency and high-frequency spectral emission of black hole accretion flows. While this mechanism is well-established for Kerr spacetimes, its thermodynamic viability around exotic, horizonless compact objects remains largely unexplored. In this article, we investigate the application of the inner viscous torque boundary condition to a thin disk embedded in a regular mini-boson star spacetime. By numerically integrating the coupled Einstein-Klein-Gordon field equations and employing the Lense-Thirring slow-rotation approximation, we generate an exact, horizonless background that strictly satisfies the weak energy condition. We demonstrate that the topological absence of a coordinate ISCO fundamentally alters the accretion dynamics. Without a sudden geodesic plunge, stable circular orbits penetrate deep into the dense scalar core, causing the physical inner boundary of the disk to be determined dynamically by the peak of the Keplerian angular velocity. Because the specific angular momentum of the fluid approaches zero at this deep microscopic boundary, the standard viscous torque is mathematically quenched. Consequently, the enhanced radiative flux divergence typically associated with boundary torques in black holes is naturally suppressed around regular boson stars. This torque quenching offers a robust phenomenological discriminator between standard black holes and horizonless ultralight scalar structures.
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Soft Condensed Matter

Improved Density Functionals for Predicting Block Copolymer Domain Structure and Phase Behavior

Yi-Xin Liu

Phase-field models offer an efficient alternative to self-consistent field theory (SCFT), but quantitative predictions of block-copolymer phase behavior remain challenging. We develop a quadratic-connectivity entropic (QCE) density functional and its adaptive extension (AQCE). QCE combines quadratic nonlocal connectivity with a nonlinear binary relative-entropy term, while AQCE adds bounded interfacial stiffness that preserves the homogeneous response. In lamellar benchmarks, QCE gives the lowest mean profile error among the tested models and AQCE the lowest mean period error. Compared with the optimized phase-field (OPF) model fitted to SCFT force and stress data, AQCE reduces strong-segregation period and profile errors by more than fivefold and sixfold, respectively. AQCE further reproduces the topology of the SCFT phase diagram for AB diblocks, a more demanding test of free-energy rankings among competing morphologies. Because architecture enters through ideal-chain correlations, the same nonlinear construction extends to other A/B architectures. We demonstrate this transfer for symmetric linear ABA lamellae, accurately predicting their profiles, periods, and ordering threshold.
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Materials Science

Determination of Burgers-vector directions of threading edge dislocations in GaN by phase-contrast microscopy

Yukari Ishikawa, Maki Shimizu, Koji Sato et al. (+4 more)

Phase-contrast microscopy enables rapid, nondestructive observation of threading dislocations in GaN, but the relationship between dislocation contrast and the Burgers vector has not been established. Here, we demonstrate that the in-plane Burgers-vector direction of threading edge dislocations in GaN can be determined from the arrangement of bright and dark contrast in phase-contrast microscopy images. The relationship was first established for threading edge dislocations in ammonothermal GaN whose Burgers vectors were independently determined by X-ray topography and was subsequently applied to hydride vapor phase epitaxy-grown GaN. The Burgers vector predicted from the phase contrast was verified by weak-beam dark-field TEM and large-angle convergent-beam electron diffraction. For the threading edge dislocations examined, the direction obtained by rotating the direction from the minimum of the dark contrast to the maximum of the bright contrast by 90{\deg} counterclockwise coincided with the Burgers-vector direction. Analysis based on the photoelastic effect further suggests that the phase contrast primarily reflects the sum of the two in-plane normal strain components, {\epsilon}xx + {\epsilon}yy, around the dislocation. These results demonstrate that phase-contrast microscopy can be used as a nondestructive optical method for determining the in-plane Burgers-vector direction of threading edge dislocations in GaN.
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All authors Yukari Ishikawa, Maki Shimizu, Koji Sato, Kisara Matsumoto, Kazuki Ohnishi, Yongzhao Yao, Ryo Hattori

Astrophysics of Galaxies

A Graph Attention Network Framework for Simultaneous Prediction of Galaxy and Dark Matter Halo Properties in GAMA DR4

Sandeep Aashish, Abhay V Hegde, Aditya Prakash Gupta et al. (+4 more)

We develop a graph-based deep learning model, GAMANet, to predict galaxy and halo properties using the GAMA DR4 dataset. Multiple catalogues are combined to construct a unified sample of 19,469 galaxies and derive a set of photometric, spectroscopic, morphological, and environmental features. The galaxy sample is represented as a graph, with galaxies as nodes and physically motivated connections based on spatial proximity and group membership as edges. A Graph Attention Network with GATv2 layers is then used to learn information from the galaxy neighbourhood while assigning different weights to neighbouring galaxies. The model simultaneously predicts halo mass, stellar mass, and a specific star formation rate proxy. On the test set, GAMANet achieves $R^2 = 0.958$, $0.985$, and $0.982$ for halo mass, stellar mass, and SSFR proxy, respectively, with an RMSE of $0.237$ dex for halo mass. These results demonstrate that graph-based learning can extract useful information about galaxy and halo properties directly from observational data while incorporating the environmental relationships encoded in the galaxy graph.
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All authors Sandeep Aashish, Abhay V Hegde, Aditya Prakash Gupta, Ashmit Verma, Md Saif, Nishanth Kumaran, Shivang Rayat

Quantum Physics

Quantum Data Ruler

Wangjun Lu

A ruler reads an unknown length against a calibrated scale. The quantum data ruler reads a matrix element of an unknown state against the signal of a known reference, from their ratio. It is exact for any Hamiltonian and any time, since transition operators change by a state-dependent constant times one function of time, removing the vanishing-signal limit. The readout is unbiased under dephasing and amplitude damping, and recovers the coherent ergotropy of a quantum battery that two-point measurement erases. The structure survives the classical limit as action–angle Fourier modes.
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High Energy Physics (Phenomenology)

Fully charmed tetraquarks on the Lattice with controlled errors

Zhenyu Zhang, Bing-Nan Lu, Qian Wang et al. (+1 more)

We introduce the lattice quark potential model (LQPM), which discretizes the nonrelativistic quark potential model on a periodic cubic lattice and diagonalizes the resulting many-body Hamiltonian exactly. Unlike variational approaches, which provide only upper bounds on the energy, LQPM removes this variational bias, and its remaining finite-volume uncertainty is removed by extrapolation. Formulated directly in coordinate space, the method is indifferent to the specific form of the potential and accommodates arbitrary interactions, such as including three-body forces and spin-orbit and tensor couplings, that are difficult to treat in conventional few-body approaches. As a benchmark, the charmonium and $\Omega_{ccc}$ spectra are reproduced within a few MeV of experiment. For the fully charmed tetraquark $cc\bar{c}\bar{c}$, we obtain a $J^P=0^+$ ground state at $5934.8(13)~\mathrm{MeV}$, $33.2(13)~\mathrm{MeV}$ below the $\eta_c\eta_c$ threshold, unambiguously identified as a deeply bound tetraquark whose existence is robust against the choice of potential. Such a state can decay into two dileption pairs $2(e^+e^-)$ via $J/\psi e^+e^-$, with significance similar to $X(6400)$, or about one order of magnitude smaller. Lying below the lowest strong-decay channel, it can decay only through electromagnetic and weak interactions. Our results establish exact lattice diagonalization as a controlled, systematically improvable, and broadly applicable route to multiquark spectroscopy, providing a quantitative benchmark for the strong interaction and valuable guidance for future experimental searches for exotic hadrons.
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All authors Zhenyu Zhang, Bing-Nan Lu, Qian Wang, Qiang Zhao

Optics

Microfabrication of Paul wheel trap chip in fused silica by selective laser etching

Jakub Vejrosta, Lukáš Šilhan, Mojmír Šerý et al. (+3 more)

We present a rapid, mask-free fabrication workflow for the Paul wheel trap chip based on selective laser etching (SLE) of fused silica. The complete process - femtosecond laser writing, wet-chemical etching in KOH ($\sim$230 $\mu$m/h, releasing the trap geometry from a 500 $\mu$m wafer in approximately 2 h), RF magnetron sputtering of silver electrodes, and direct femtosecond laser ablation for electrode patterning - is carried out in-house, bypassing photolithographic processing and custom shadow masks entirely. Nine chips per 4-inch wafer can be produced in a single working day, reducing the fabrication lead time by more than one order of magnitude relative to the outsourced CVD diamond design. The functionality of the fabricated wheel trap chip is confirmed by a proof-of-concept microparticle trapping demonstration, in which a single microparticle was confined continuously for 72 h at atmospheric pressure. This establishes SLE of fused silica as a rapid, economically accessible fabrication platform for Paul traps in levitated-optomechanics applications.
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All authors Jakub Vejrosta, Lukáš Šilhan, Mojmír Šerý, Tomáš Fořt, Oto Brzobohatý, Pavel Zemánek

Fluid Dynamics

Only Linear Constraints Survive Coarse-Graining: Evaluating Physics-Constrained Neural Operators on Stochastically Forced Turbulence

Michael Groom and Rafael Oliveira

A physics-informed loss adds a discretised PDE residual to the data term, but is only strictly valid if the equations being enforced are closed on the fields being fitted. This fails on coarse-grained, stochastically forced data: nonlinear terms in the PDE generally do not commute with the filter, so the coarse-grained fields do not satisfy the original equations, and driving their residual to zero encodes an implicit closure into the learned operator. Under normalised, translation-invariant filtering on a periodic domain, constant-coefficient linear constraints remain valid on the filtered grid. For the 2D incompressible Navier-Stokes equations, two such constraints are continuity and global momentum balance. We enforce these exactly by applying a closed-form projection on the output of a Fourier neural operator (FNO) at $O(N \log N)$ cost. On two-dimensional isotropic turbulence, truncated so that its forcing lies entirely beyond the cutoff wavenumber, the projection achieves a continuity error of $5.0\times10^{-7}$ against 0.51 for a plain FNO and 0.17 for a physics-informed FNO, and a global momentum balance error of $8.6\times10^{-11}$ against $7.5\times10^{-4}$ and $8.3\times10^{-4}$. The projection only costs an extra 2% of training time, and takes the fraction of rollouts whose energy remains bounded at 448 steps from 0.18 to 0.87. On resolved Kolmogorov flow, test-time optimisation costs approximately 3,300$\times$ as much per trajectory as the projection, while leaving maximum divergence three orders of magnitude higher. Nonlinear constraints can also be enforced once their unclosed terms are modelled: closing the global energy balance with a constant subgrid flux, fitted from the coarse training data alone, removes the 20.9% energy deficit that enforcing the unclosed balance produces and keeps every free-running rollout bounded over 2,000 steps.
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High Energy Physics (Theory)

Reheating surface volume renormalization and eternal inflation under broken scale invariance

Min-Seok Seo

Recently, Cotler, Ivo, and Maldacena have shown that under scale invariance, eternal inflation is interpreted as a failure of the reheating surface volume renormalization due to an ill-defined scaling dimension. Meanwhile, observations suggest that scale invariance is slightly broken, which is parametrized by deviation of the spectral index from unity, $\varepsilon=n_s-1$. Motivated by this, we study how the scale invariance breaking effect modifies the no-eternal inflation condition as the renormalizability of the reheating surface volume. For this purpose, we adopt two independent approaches: investigating the behavior of the normal ordered reheating surface volume operator under a shift of the curvature perturbation, and analyzing the coarse-graining structure to obtain the scaling dimension. Both approaches commonly reveal that as long as $\varepsilon$ is negative, which is consistent with observations, the fractal structure of the reheating surface volume breaks down at macroscopic scale, moderating the no-eternal inflation condition.
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Quantum Physics

Quantum telescopy with realistic anti-correlated optical fields as references

Xuan Tang and Z. Y. Ou

Quantum telescopy, proposed by Grottesman et al., uses spatially entangled single-photon states to modify HBT stellar interferometry, potentially surpassing Michelson interferometry in resolution without baseline limits. However, finite source bandwidth, non-unit efficiency, detector response times, and celestial light bandwidth all affect its effectiveness. In this work, we consider a spatially entangled singe-photon state generated by beam-splitting a practical anti-bunched photon source from resonance fluorescence, which is a common method of generating single-photon states, and evaluate the signal level in quantum telescopy with inclusion of imperfection of detection system and finite bandwidth of celestial light. Here, given the incoming light, we optimize the parameters of the anti-bunched photon source and the detector system for the best signal-to-noise ratio (SNR), which can match that of the Michelson method in the ideal case but is always smaller in the realistic case. Alternatively, weak coherent states from heavily attenuated lasers can replace the entangled single-photon state but suffer low signal level, similar to HBT method. We find that the SNR with a realistic anti-bunched source for producing the reference fields can still beat the SNR of the coherent state scheme in the weak incoming field limit. The optimized parameters for the anti-bunched source and detection system will be a guide for future experimental endeavor.
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Mesoscale and Nanoscale Physics

Ferroaxial Electronic Response to Local Lattice Rotation

Ken Uchino, Yuuki Ogawa and Satoru Hayami

We theoretically investigate electronic responses to lattice deformation in a ferroaxial system using a tight-binding model on a two-dimensional square lattice and linear response theory. While conventional elastic responses are commonly discussed in terms of symmetric strain, the displacement gradient also contains an antisymmetric component describing a local lattice rotation. Focusing on this rotational degree of freedom, we treat the symmetric strain and antisymmetric local rotation as independent perturbations and incorporate their effects microscopically through deformation-induced modulations of the electronic hopping amplitudes. We find that the local rotation induces characteristic diagonal electric quadrupoles that are distinct from those generated by the symmetric shear strain. The rotation-induced response is dominated by the intraband contribution and increases approximately linearly with the ferroaxial crystal field, vanishing in the absence of ferroaxial order. In contrast, the symmetric-shear-induced response remains finite without ferroaxial order and contains both intraband and interband contributions. These results demonstrate that the antisymmetric local rotation provides a distinct electronic response channel characteristic of the ferroaxial state.
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High Energy Physics (Theory)

Spontaneous Hawking Radiation from Dynamical Black-Hole Formation in Quantum Spin Systems

Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto et al. (+1 more)

We show that Hawking radiation spontaneously generated by dynamical black-hole formation can be realized in a local quantum spin model. Starting from the ground state corresponding to the early-time vacuum, with no initially prepared excitations, we follow the dynamics induced by the evolving geometry. In the corresponding continuum quantum field theory, Hawking particle creation is associated with nontrivial Bogoliubov mixing between the in- and out-mode decompositions. We derive the resulting renormalized local energy density in the continuum quantum field theory, which corresponds to an energy-weighted integral of the Hawking spectrum, and identify its counterpart as a local spin observable whose expectation value quantitatively reproduces the continuum prediction, including its dependence on the surface gravity. The agreement persists over a finite time window whose duration grows logarithmically with system size, revealing the crossover from universal continuum Hawking physics to lattice-cutoff dynamics. These results establish a microscopic route to quantum simulation of quantum field theory in curved spacetime, connecting field-theoretic particle creation directly to experimentally accessible many-body observables.
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All authors Shunichiro Kinoshita, Keiju Murata, Daisuke Yamamoto, Ryosuke Yoshii

High Energy Physics (Phenomenology)

Fractal phase structure of QCD under imaginary rotation

Rin Takada

We show that in hot QCD rotating at an imaginary angular velocity $\Omega_I$, the angular velocity selects not only the temperature of the bulk but whether charge conjugation $C$ is broken there. For QCD at temperature $T$ and imaginary quark chemical potential $\theta$, with $\Omega_I/2\pi=p/q$ in lowest terms, the bulk far from the rotation axis is in the same thermal equilibrium state as nonrotating QCD at temperature $T/q$ and imaginary quark chemical potential $\theta'=q\theta+\pi(p+q+1)$; this follows from the Euclidean boundary conditions and locality alone, and holds nonperturbatively. Consequently, even at zero quark chemical potential, the bulk is placed at the Roberge-Weiss (RW) point whenever $p$ and $q$ are both odd, and $C$ is spontaneously broken there for $T>qT_{\rm RW}$, with $T_{\rm RW}$ the RW endpoint temperature. The bulks at $\Omega_I=2\pi/3$ and $4\pi/3$, for example, are both at temperature $T/3$, yet only the former can break $C$. The set of imaginary angular velocities at which $C$ is broken has a fractal structure: raising $T$ adds rationals of ever larger denominator. At irrational $\Omega_I/2\pi$ the bulk corresponds to zero-temperature QCD at any $T$ and remains confined.
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Mathematical Physics

Convergence Without Finite Exactness in the Eigenstate Quantum Bootstrap

Ye Zhou and Daniel Keren

The eigenstate quantum-mechanical bootstrap can converge to the physical moment set while remaining nonexact at every finite order. We prove this for a one-dimensional quasi-exactly solvable sextic oscillator at explicitly known eigenvalues, including excited levels. At every finite order, the lower and upper bounds on $u^2$ remain strictly below and above its physical value, even after adjoining arbitrary finite polynomial Gram tests and all eigenstate-annihilator relations visible in the retained moment space. Hence neither side of the centered observable admits a finite sum-of-squares certificate modulo the eigenstate annihilator. The gap persists under any finite set of additional localizing constraints whose weights are strictly positive on polynomial vectors. We then prove convergence for polynomial Schrödinger operators satisfying explicit sum-of-squares confinement and derivative bounds. The eigenstate relations give moment estimates uniform in the truncation order; these yield a regular Schrödinger representation supported on the prescribed eigenspace. Finally, a four-mode extension combines this fixed-observable obstruction with feasible position moments having no positive representing measure at every finite order. At level three, this construction yields nonphysical feasible points with strictly positive definite moment matrices.
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High Energy Physics (Experiment)

Search for rare charm decays at BESIII

Xiaokang Li and for the BESIII Collaboration

The BESIII experiment searches for rare and symmetry-violating decays with the largest charmonium and threshold open-charm data samples. This contribution reviews recent searches for charmonium weak decays, charm flavour-changing neutral currents, charged-lepton flavour violation, and Bose-symmetry violation. The weak-decay searches have improved several branching-fraction limits, while studies of rare charm-meson and charmonium decays probe flavour-changing neutral currents. Searches for charged-lepton flavour violation set limits in vector and pseudoscalar meson decays and constrain effective interactions. No significant signals are found in any of these searches. The neutral-kaon limits fall below the expectations of a proposed locality scenario, and the $J/\psi$ limit approaches the scale predicted for Standard Model CP violation.
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Mathematical Physics

Pulsation of quantum walk on finite graph

Taisuke Hosaka and Etsuo Segawa

We study discrete-time quantum walks on weighted graphs, where every edge in an edge cut set is assigned a small weight $\epsilon>0$. The parameter $\epsilon$ represents the strength of the connections through the cut edges: as $\epsilon \to 0$, these connections vanish, and the graph decomposes into the connected components obtained by removing the cut edges. We refer to these weighted cut edges as weak edges. We show that, for sufficiently small $\epsilon$ and on the time scale $t=\Theta(\epsilon^{-1/2})$, the finding probabilities between the connected components are asymptotically described by a continuous-time wave equation on a reduced graph, whose vertices represent the connected components and whose edges represent the weak edges connecting them. The wave equation is governed by a symmetric weighted Laplacian determined by the reduced graph and the number of arcs contained in the components. Consequently, finding probabilities of leading-term are independent of the detailed internal structures of the components. We further show that this wave equation has the same form as Newton's equation of motion for a classical spring-mass system on the reduced graph.
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General Relativity and Quantum Cosmology

Charged soliton–black hole phase transitions in three-dimensional Einstein–Gauss–Bonnet gravity

Cendikiawan Suryaatmadja and Robert Mann

We construct a magnetic soliton by double Wick rotating the static electrically charged black hole in three-dimensional Einstein–Gauss–Bonnet gravity. We match the boundary metrics and Maxwell sources under the chosen boundary condition and compute the difference of the renormalized Euclidean actions. Because the Maxwell potential grows logarithmically at infinity, the chosen finite Maxwell boundary term changes both the fixed Maxwell source and the renormalized action. The charge contributions for both the soliton and the black hole appear with plus signs in $\Delta I^{(c_{\mathrm{fin}})}$. For the grand-canonical boundary condition $c_{\mathrm{fin}}=1$, the black-hole and soliton branches can cross with different slopes. For the example considered below, the black-hole branch satisfying the response conditions ends at a maximum temperature, and the coexistence curve has a $T\to0^+$ endpoint at two opposite values of the spatial Maxwell source. At a nonextremal crossing, the entropy difference is $S_b-S_s=S_b$. For these two static solutions, equality of both current components requires both charges to vanish.
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High Energy Physics (Theory)

Thermodynamics and mechanical laws of causal-diamond horizons

Carlos R. Ordóñez and Gustavo Valdivia-Mera

We develop a unified thermodynamic and mechanical framework for causal-diamond horizons in Minkowski spacetime. Euclidean regularity fixes the temperature $T_D=1/(\pi\alpha)$, where $2\alpha$ is the temporal extent of the diamond. The regulated Gibbons–Hawking–York contribution gives $I_D^E=-A_0/(4G)$, with $A_0$ the area of the horizon bifurcation surface, and the vanishing equilibrium geometric energy then yields the entropy–area relation $S_D=A_0/(4G)$. For weak matter perturbations crossing a localized portion of the future horizon, a Raychaudhuri analysis relates the associated Killing-energy flux to the area response, yielding a local physical-process first law at leading order near the bifurcation surface and, for classical matter satisfying the null energy condition, a local second law. Uniform conformal surface gravity establishes the zeroth law, while zero temperature is approached only in the limit $\alpha\to\infty$, in which the finite causal horizon disappears. These results show that a coherent horizon-law structure can arise within a causal diamond, a fundamental building block of the causal structure of Minkowski spacetime. The derivation is explicit in $(2+1)$ dimensions, while the physical results retain the same form for spherical causal diamonds in $d\geq3$.
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Instrumentation and Methods for Astrophysics

Very Long Baseline Interferometry with the SKA Observatory

J. F. Radcliffe, J. Yang, Z. Paragi et al. (+131 more)

Very Long Baseline Interferometry (VLBI) is a fundamental technique that combines signals from telescopes separated by thousands of kilometres to obtain some of the highest-resolution images in astronomy. The Square Kilometre Array Observatory (SKAO) will provide sensitive elements to current VLBI arrays, enabling deep VLBI observations (including the first low-frequency VLBI capability in the Southern Hemisphere). This summary chapter outlines the science that the SKAO, when participating in a VLBI array, will achieve (such as AGN physics, explosive transient localisation, Galactic structure, and gravitational waves), and the current understanding of how VLBI with the SKAO will operate. Given that VLBI requires partnerships with other instruments, the chapter concludes with outstanding issues and considerations for the community needed to maximise the scientific return on investment in SKA-VLBI.
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All authors J. F. Radcliffe, J. Yang, Z. Paragi, O. Bayandina, C. Reynolds, C. García-Miró, T. An, M. Abada-Simon, J. N. H. S. Aditya, I. Agudo, T. Akahori, A. Alberdi, S. Anton, P. Atri, A.-K. Baczko, S. Belladitta, E. K. Bempong-Manful, R. Beswick, M. Bhardwaj, E. Bonnassieux, A. Brunthaler, C.-S. Chang, P. Charlot, S. Chen, W. Chen, X. Cheng, A. Chhipa, J. O. Chibueze, I. Cho, J. B. Climent, L. Cui, S. Curiel, F. D'Ammando, J. R. Dawson, A. Deller, H. Ding, R. Dodson, J. Drevon, F. Eppel, S. Frey, M. Garrett, M. Gawroński, J. Geng, S. Giarratana, M. Giroletti, S. Gulyaev, L. I. Gurvits, C. Hao, T. Hirota, A. J. Hedge, H. Hu, H. Imai, P. Jiang, J. de Jong, M. Kadler, B. Karimi, P. Kharb, R. Khatun, J.-Y. Kim, J. Kim, J. Kim, F. Kirsten, H. R. Klöckner, H. Kobayashi, Y. Y. Kovalev, M. Kunert-Bajraszewska, A. Kutkin, H. J. van Langevelde, J. Li, Y. Li, Y. Li, Z. Lin, D. Liu, H. Liu, K. Liu, A. Lobanov, R.-S. Lu, V. Mahatma, B. Marcote, M. Mezcua, J. Moldón, L. K. Morabito, S. E. Motta, S. Murthy, I. Natarajan, A. Njeri, J. Oh, M. Orienti, A. Osetrova, M. Pandey-Pommier, F. Panessa, J. Park, M. Pérez-Torres, L. Petrov, J. C. S. Pierce, C. Phillips, L. Ricci, M. Rioja, H. Ro, J. Röder, E. Ros, M. Rupen, K. L. J. Rygl, R. Santra, S. Silpa, T. Savolainen, G. A. S. Sundaram, P. Shastri, X. Shu, A. Słowikowska, B. W. Sohn, C. Spingola, F. Sweijen, K. Takahashi, R. Timmerman, F. Ubertosi, L. Uscanga, E. Varenius, M. Verkouter, T. Vernstrom, S. Wagner, D. Williams-Baldwin, J. Wongphechauxsorn, X. Wu, M. Xu, Y. Xu, M. K. Y{\i}ld{\i}z, Z. Yan, A. Yang, X. Yang, S. Yao, W. Yu, B. Zhang, P. van Zyl

Lattice Field Theory

Mass as pairing: an explicit Majorana mass on half of a generation does not seesaw in symmetric mass generation

Piotr S. Topa

A fermion mass pairs a field with a partner of conjugate charge: elementary (Higgs-Dirac), self-conjugate (seesaw) or a three-fermion composite (symmetric mass generation, SMG). We give half of a Spin(10)-like generation an explicit Majorana mass in a four-dimensional SMG model and ask what the other half does in a phase with no condensate. With the source on, every mass-type term of the unsourced half averages to zero under the symmetry group of the sourced action, so a light mass term, and a seesaw's light-heavy mixing, requires a spontaneously broken symmetry; exact on the lattice and a general proposition. The source is colour-democratic (a Delta_R-type mass on every flavour's right-handed taste doublet); the single-nu_R split lies outside the positivity class used but inside the symmetry statement. Measured up to 8^4: (i) in the symmetric-gap phase, with the source screened to at most 1.1% of free, the unsourced half's single-fermion readout stays at 0.3% of free while its pair susceptibility rises from 0.2% to 1.2-1.7% at h=2; on like mode sets it falls with the volume, on (4^4,8^4) no inequivalent light mass channel grows faster than free, and symmetry breaking is not resolved at L<=8; (ii) at the critical point the explicit mass collapses the critical sigma channel and moves the light half toward free as a saturating crossover, not a power law; direction tests (MIXED by their pre-registered letter) are consistent with a critical coupling rising with the mass; y_c(h) is not located. Pole versus zero of the light propagator at p->0 is not measured. The outcomes are readings after pre-registered tests that mostly returned no verdict. Also: no first-order signature of the merged transition at L<=8, a Z_4-odd response handed to a lattice composite, and flavour democracy of the positivity class. Every claim has an evidence class and a runnable check.
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Mesoscale and Nanoscale Physics

Theory of Magic Angles in Twisted Bilayer Graphene: from Non-Abelian Gauge Fields to Flat Bands

Leonardo A. Navarro-Labastida and Gerardo G. Naumis

At a discrete set of “magic” twist angles, twisted bilayer graphene develops two bands at charge neutrality that are almost perfectly flat. We present a unified theory of this phenomenon within the chiral continuum model. The central object is the square of the chiral Hamiltonian, a $2\times2$ Schrödinger operator for an electron moving in a non-Abelian $SU(2)$ pseudo-magnetic field generated by the interlayer tunneling. From it we derive an energy sum rule in which the interlayer coupling splits into a bounded overlap channel and an unbounded current channel; their different scaling with the coupling $\alpha$ explains why the first magic angle is qualitatively different from the rest. The asymptotic rule $\alpha_{m+1}-\alpha_m\to3/2$ follows from a rescaling of the moiré potential together with its three-cell magnetic periodicity, with the two parity families of zero modes each repeating with period $3$ and interleaved with each other. Near the AA point the zero-mode problem becomes a lowest-Landau-level problem in an effective field $B_{\rm eff}=3\alpha$, so that the high-order zero modes are coherent Landau states of width $1/\sqrt{3\alpha}$ whose guiding centres converge to $\pm(\pi/3) q_\mu$, with kinetic and confinement energies in equipartition. Deforming the coupling into an Abelian one removes the magic-angle sequence, which shows that the non-Abelian structure is essential. Between consecutive magic angles, band inversions at $\Gamma$ and $M$ produce phases with Chern numbers $C=\pm2$, and the quantum metric reaches a sharp maximum at $\theta\approx0.43^\circ$, identifying a promising regime for correlated and topological phases beyond the first magic angle.
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Statistical Mechanics · Cross-listed from math.PR

Shape theorem for excited random walks on the integer lattice

Tuan-Minh Nguyen

We study the limit shape of the range of the random walk excited to the center on $\mathbb Z^d$, with $d\geq2$. A cookie is placed at each nonzero vertex. On its first visit to such a vertex, the walker consumes the cookie and takes its next nearest-neighbor step with a bias toward the origin. On a visit to the origin, or on later visits to a nonzero vertex, no cookie is available and the walker moves to a neighbor uniformly at random. We prove that the set of vertices visited up to time $n$, rescaled by $n^{-1/(d+1)}$, converges in probability in Hausdorff distance to an explicit $\ell^1$ ball. This answers a question raised by Kozma (2007).
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Mesoscale and Nanoscale Physics

Bichargon Hall Effect

Ping Tang

The conventional Hall effect arises from the transverse deflection of mobile electronic charge carriers in conductors. Here, we predict a bosonic charge Hall effect in charge-ordered insulators mediated by bichargons, collective bosonic excitations of charge order carrying quantized electric charges $\pm 2e$. In contrast to conventional electronic carriers, a thermally excited bichargon gas does not support dc electrical conduction in response to an external electric field despite its constituents carrying finite electric charges. We show that a temperature gradient can instead drive a diffusive flow of thermal bichargons, while an out-of-plane magnetic field deflects the oppositely charged bichargons in opposite transverse directions via the Lorentz force, leading to a finite Hall charge current and opposite charge accumulations at the sample edges. Our results broaden the paradigm of charge Hall transport beyond conventional electronic conductors, establishing that a charge Hall response can emerge in an electrically insulating system through charged bosonic quasiparticles.
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Fluid Dynamics

Direct numerical simulations of multi-layer Rayleigh-Taylor instability under asymmetric interfacial density stratification

Abhijeet Guha, Prasoon Suchandra and Aditi Sengupta

Direct numerical simulations of thermally stratified multi-layer Rayleigh-Taylor instability are performed to investigate the influence of interfacial Atwood number (At) on instability growth, interfacial coupling, turbulent mixing, and spectral characteristics. A fully compressible, three-dimensional, high-fidelity Navier-Stokes solver has been used to simulate ten cases spanning a broad range of interfacial $At$ to examine the evolution of coupled instability dynamics. The configuration consists of three superposed fluid layers with unstable density stratification across two interfaces generated through temperature variations. The temporal evolution of the flow is characterized using the maximum vorticity, mixing-layer growth, density fluctuations, turbulent kinetic energy, and energy partitioning between gravitational potential energy, TKE, and dissipation. The instability evolution is shown to proceed through distinct onset, quasi-exponential growth, and nonlinear saturation stages for all configurations. Increasing interfacial At leads to earlier instability onset, enhanced vorticity amplification, and accelerated development of turbulent mixing layers. The weakly stratified configurations exhibit dynamics resembling effectively single-interface RTI, whereas the strongly stratified cases develop two simultaneously active mixing layers that subsequently interact and merge into a coupled turbulent region. The wall-normal distributions of density fluctuations and TKE demonstrate progressive broadening of the mixing region and increasing redistribution of turbulent activity with increasing stratification strength. The late-stage spectra exhibit an approximate -11/5 scaling over an intermediate range of wavenumbers, consistent with buoyancy-dominated turbulent transport.
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Astrophysics of Galaxies

The Role of the Cosmic Web in Galaxy Evolution Across 0.4<z<4

Sina Taamoli, Bahram Mobasher, Hossein Hatamnia et al. (+12 more)

We investigate the dependence of stellar mass and star formation activity on the topology of hosting large-scale structures using mass-complete galaxy samples in four redshift bins spanning from z = 0.4 to z = 4 using the COSMOS2020 catalog. Cosmic web components (clusters, filaments, and field) are identified by applying the Multiscale Morphology Filter to galaxy density maps, and group memberships (central, satellite, isolated) are assigned to each galaxy by the Friends of Friends (FoF) algorithm. Out to z < 1, we find that stellar mass increases toward denser structures, driven primarily by central and satellite galaxies, with differences up to ~0.35 dex between field and clusters. At these redshifts, star formation rate (SFR) is suppressed by ~0.1 dex in clusters compared to field galaxies, particularly for centrals, while the SFR of star-forming galaxies shows a much weaker dependence on the type of host structure, indicating that the quenched population primarily drives the observed environmental dependence. Specific SFR (sSFR) shows the strongest decline for centrals in clusters at z<1, consistent with enhanced quenching in dense environments. At 1<z<2, star formation activity becomes largely independent of environment, suggesting a transitional regime in the role of large-scale structure. At z>2, we observe a mild increase in SFR (~+0.1 dex) and sSFR (~+0.13 dex) from field to cluster galaxies, pointing to a possible reversal of environmental trends during early cosmic epochs. These results highlight the evolving influence of environment on galaxy evolution and set the stage for deeper investigations with upcoming wide-field surveys.
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All authors Sina Taamoli, Bahram Mobasher, Hossein Hatamnia, Nima Chartab, John R. Weaver, Ghassem Gozaliasl, Anton M. Koekemoer, Caitlin M. Casey, Jeyhan S. Kartaltepe, Aryana Haghjoo, Olivier Ilbert, Henry J. McCracken, David B. Sanders, Nicholas Scoville, Sune Toft

Mathematical Physics

A mathematical analogy between certain hollow vortex and bubble flows - existence, uniqueness, and identical boundary shapes

Valentin D. Kunz, Saleh Tanveer and Darren G. Crowdy

We study two physically distinct steady free-boundary problems in a two-dimensional inviscid fluid: a hollow vortex in a constant-vorticity flow subject to simple shear, third order and linear strain at infinity, without surface tension, and an irrotational flow past a constant-pressure bubble subject to surface tension, linear strain, and circulation at infinity. Building on the mathematical vortex-bubble correspondence recently developed by Crowdy and Tanveer, we show that both problems are linked by a common mathematical formulation. For the vortex problem, we extend the sequence-space fixed-point approach of Crowdy and Tanveer to obtain new local existence, uniqueness, and analyticity results. For the bubble problem, we develop a separate existence theory, reducing it to a nonlinear singular integral operator fixed-point problem and deriving a scalar solvability condition that defines a realanalytic surface in the physical parameter space. On this surface we obtain locally unique bubble solutions with real-analytic boundaries and holomorphically extendible velocity fields. Finally, we prove that the scalar solvability condition is equivalent to a functional conformal mapping identity. The scalar condition between the parameters is enough for the vortex and bubble problems to have the same free-boundary shape, despite their different exterior flows.
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Fluid Dynamics

Airborne liquid marble: Evaporation dynamics of liquid marble in acoustic levitation

Keigo Noro, Xiao Ma and Koji Hasegawa

Liquid marbles (LMs), droplets encapsulated by hydrophobic particles, allow for non-wetting manipulation and containerless handling, making them well-suited for applications such as microreactors. When integrated with acoustic levitation, the LMs serve as contact-free reaction platforms. However, the complex behaviours associated with acoustic fields, including deformation, internal flow, and evaporation, remain insufficiently understood. This study investigates the evaporation dynamics of acoustically levitated LMs. Simultaneous visualisation of the droplet morphology and surrounding vapour concentration fields was achieved using backlighting and the Background-oriented Schlieren (BOS) method. At intermediate relative humidity (RH = 40%), the evaporation rates and vapour distributions of LMs closely resembled those of pure water droplets, indicating that the particle shell exerts minimal influence under these conditions. Conversely, significant differences were observed at high- and low-humidity, attributable to the evaporation resistance and interfacial properties introduced by the hydrophobic particle layers. Furthermore, although pure water droplets maintained a quasi-spherical shape, LMs demonstrated progressive flattening over time, suggesting mechanical constraints imposed by the particle shell. These findings provide new insights into the coupled evaporation and deformation behaviours of LMs in acoustic fields, informing the design of contamination-free microfluidic and microreactor systems.
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Quantum Physics

Demonstration of Parallel Multi-QPU Execution for Fragment-Based Quantum Chemistry Using On-Premises Hardware

Nils Herrmann, Mariam Akhtar, Luke W. Bertels et al. (+21 more)

Fragment molecular orbital (FMO) quantum chemistry offers a natural route to parallel quantum computing: large molecular calculations can be decomposed into smaller quantum subproblems that can, in principle, run concurrently. Their practical benefit on real quantum hardware, however, has remained unclear. We demonstrate parallel FMO calculations on three room-temperature diamond-based 'Quoll' quantum computers installed on-site at the Oak Ridge Leadership Computing Facility. Helium clusters (He$_{n}$, $n=2,4,8,10,14$) served as a testbed for total energy calculations using the Quantum Wave Function Sampler (QWFS), a selected configuration interaction (SCI) approach. We compare two execution modes: synchronous shot-parallel execution, in which quantum processors jointly sample QWFS circuits and combine their SPAM-corrected counts into a single probability distribution; and asynchronous fragment-parallel execution, in which processors independently evaluate FMO fragments using device-specific optimized circuits. Both modes increase quantum sampling throughput without systematic loss of accuracy. The three-QPU shot-parallel workflow reaches a parallel efficiency of $93.60\%$, while the fragment-parallel workflow achieves a measured efficiency of $75.01\%$, increasing to $95.17\%$ when excluding the non-useful idle time associated with non-interruptible submitted jobs. In both cases, the assembled FMO-QWFS energies remain chemically accurate compared to the classical ideal. These results provide a proof-of-concept demonstration that parallel quantum execution can improve the practical throughput of quantum chemistry workflows on prototype hardware, motivating the development of future HPC environments with many fault-tolerant quantum processors operating as a distributed resource for molecular and materials simulation.
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All authors Nils Herrmann, Mariam Akhtar, Luke W. Bertels, Leigh Cameron, Raymond Chan, Lei Cheng, Daniel Claudino, Mark de Burgh, Simon Gemmell, Rugang Geng, Geoff Gillett, Travis Humble, Stephan Irle, John P. McMahon, Christian Ortiz, Florian Preis, Andreas Sawadsky, Bianca Sawyer, Reuben Singer, Sai Meghana Tunikipati, Cameron Walters, Lachlan Whichello, Adam Zegelin, Marcus W. Doherty

Quantum Physics

When Expressivity Is Not Enough: Discrete Routing Geometry in Variational Quantum Circuits

Yu Wang

Finding useful variational quantum circuits requires more than representational capacity: training must also have access to directions that improve the objective. We study how discrete CNOT routing shapes both capacity and local accessibility. For circuits built from CNOT and arbitrary one-qubit gates, we separate binary routing matrices from continuous rotations to relate global capacity to local tangent accessibility. An exact finite-field formula for the operator Schmidt rank of a CNOT block and cumulative multiblock bounds yield capacity constraints and a Bell-pair fidelity obstruction. Locally, routing propagates generators into a routing-dependent tangent space, so all parameter gradients can vanish even when the ambient objective gradient is nonzero; frame bounds distinguish loss of gradient coverage from poor conditioning. A routing-conditioned identity insertion preserves the current unitary, state, loss, and existing gradients while adding new tangent directions. Candidate-only and incremental projection scores provide local criteria for ranking insertions. Exact-statevector tests show strong short-horizon score-descent correlations on controlled Bell tasks and effective equal-cost selection on connected Heisenberg chains up to twelve qubits, with complementary TFIM selector controls. A broader TFIM routing ensemble exhibits routing-dependent near-stagnation. Together, these results connect representational capacity, local accessibility, and same-point repair through a common discrete routing description. An architecture need not remain fixed during training: task-dependent geometric information can guide the opening of new descent directions while preserving the learned circuit at insertion. This provides a concrete local approach to a broader problem: how useful quantum circuits can be discovered from the information a task supplies.
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Mathematical Physics

Spontaneous symmetry breaking at any temperature in a local one-dimensional model

Andrew Lucas

We present a one-dimensional classical statistical physics model on an infinite lattice with nearest-neighbor interactions and local state space $\mathbb{Z}^2$, with a “helical" symmetry group $\mathbb{Z}^2\rtimes \mathbb{Z}$ mixing flavor symmetry with spatial translation. For any $0<\beta<\infty$, we construct an uncountable infinity of DLR (Gibbs) states parameterized by $\mathbb{R}^2$, with a free $\mathbb{Z}^2$ flavor symmetry group action; as such, we interpret the model as exhibiting spontaneous symmetry breaking at any temperature. The most general DLR state we construct is interpreted as an infinite sequence of localized domain walls separating a pair of asymptotic “symmetry sectors". Although any normalizable Gibbs state necessarily breaks a countably infinite freely-acting symmetry group, a natural regularization of the problem to (arbitrarily) large but finite systems with periodic boundary conditions has measure concentration in disjoint and far-separated symmetry-related clusters in the (now unique) Gibbs state, which justifies our interpretation of spontaneous symmetry breaking on the infinite line. A modification of the model with local state space $\mathbb{R}^2$ must break a continuous helical symmetry at any temperature. This is not a contradiction with the Mermin-Wagner Theorem, because this continuous helical symmetry is non-compact and does not commute with translation.
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