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Physics

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Thursday 11 June

Mesoscale and Nanoscale Physics

A micromagnetic model with bidirectional magneto-thermal coupling

Peiru Yi, Zian Xia and Weichao Yu

Most conventional micromagnetic frameworks in spin caloritronics rely on a unidirectional coupling approximation, wherein thermal fluctuations drive magnetization dynamics while the feedback of magnetic dissipation onto the thermal reservoir is neglected. Here, we establish a rigorously self-consistent bidirectional magneto-thermal coupling model by integrating the stochastic Landau-Lifshitz-Gilbert (sLLG) equation with a generalized heat transfer equation. In this closed-loop framework, the local temperature acts as a dynamical variable, and the damping-induced dissipation alongside stochastic work dynamically feeds back into the thermal bath as localized heat sources. Utilizing Ito stochastic calculus, we analytically prove that this coupled system strictly obeys the first law of thermodynamics and spontaneously recovers the correct Boltzmann statistics at equilibrium. Spatially resolved micromagnetic simulations further validate the energy exchange mechanism, capturing the finite-bath temperature reduction induced by spatial variation of magnetic moments and the modified density of states under exchange interactions. This bidirectional framework provides a robust microscopic foundation for investigating complex nonequilibrium magneto-thermal dynamics, such as the unidirectional spin-wave heat conveyer effect, paving the way for advanced spin-caloritronic applications.
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Materials Science

Conditional spinodal decomposition in Li-Mg anodes for lithium metal batteries

Leonardo Shoji Aota, Aubin Leray, Yuqi Liu et al. (+14 more)

The development of batteries with high energy density, short charging times and use of sustainable materials is critical for decarbonization. Magnesium (Mg)-based anodes for lithium (Li) metal batteries promote homogeneous Li plating, thereby avoiding the formation of Li dendrites that cause short circuits and battery failure. However, microstructural modifications induced by Li-alloying and their influence on battery operation remain elusive. Here, we unveil the previously unknown formation of an ordered B2 phase, which creates a conditional spinodal decomposition with the e̱ta}-body-centered cubic phase. Chemical fluctuations characteristic of spinodal decomposition give rise to uniformly dispersed Li-rich e̱ta}-BCC and Li-poor B2 continuous interconnected phases, with the former providing a fast diffusion pathway for Li diffusion towards the anode, hence decreasing the propensity for dendrite formation at elevated current density. This is achieved using Earth-abundant and inexpensive Mg.
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All authors Leonardo Shoji Aota, Aubin Leray, Yuqi Liu, Frederic de Geuser, Chanwon Jung, Shyam Katnagallu, Tim M. Schwarz, Alisson Kwiatkowski da Silva, Júlio César Pereira dos Santos, Eric Marchezini Mazzer, Poonam Yadav, Christoph Freysoldt, Frank Stein, Yug Joshi, Se-Ho Kim, Dierk Raabe, Baptiste Gault

General Relativity and Quantum Cosmology

Tests of general relativity at the fourth post-Newtonian order with GW230627 and GW250114

Xi-Min Liang, Yuan-Zhu Wang, Tao Zhu et al. (+2 more)

Gravitational wave (GW) observations provide an unprecedented laboratory for testing general relativity (GR) in the strong-field, highly dynamic, and relativistic regimes. Within the parameterized post-Newtonian (PN) formalisms, waveform generation tests have conventionally been limited to constraining inspiral coefficients up to the 3.5PN order. Leveraging the recent theoretical breakthrough that extended the analytical compact binary phasing to the 4.5PN order, we present the first observational constraints on these higher-order effects. Our analysis utilizes two exceptional events detected by the LIGO-Virgo-KAGRA (LVK) network: GW250114\_082203, which boasts the highest signal-to-noise ratio (SNR) recorded to date, and GW230627\_015337, which features a uniquely prolonged inspiral phase and the highest inspiral phase SNR to date. By performing Bayesian inference on the dimensionless deviation parameters ($\delta\phi_i$) associated with the 4PN and 4.5PN coefficients, we find that our results are fully consistent with the predictions of GR. While the current 90% credible intervals for the four deviation parameters are of order $\mathcal{O}(1) \text{-} \mathcal{O}(10)$, the general relativistic null values ($\delta\hat{\phi}_a= 0$) are entirely encapsulated within the bounds. This investigation establishes the first empirical baseline for 4PN and 4.5PN inspiral tests of GR, paving the way for high-precision null tests of GR with current and next-generation GW detectors.
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All authors Xi-Min Liang, Yuan-Zhu Wang, Tao Zhu, Wen Zhao, Xin Zhang

High Energy Physics (Theory)

Double copy of form factors with multiple operator insertions

Xinyue Li, Gang Yang and Guorui Zhu

Extending the double copy of scattering amplitudes to more general physical quantities involving local gauge-invariant operators is a central open question. While progress has been made in the double copy of form factors (FFs) with a single-operator insertion, it has led to two intriguing features: poles that are spurious from the FF viewpoint become physical propagators in gravity, and FFs obey hidden factorization relations on these poles. This picture is difficult to generalize to FFs with multiple operator insertions due to even more complicated spurious pole structures. We resolve this problem by introducing a "dyeing" procedure that promotes color-singlet operators to adjoint colored states, while the original FF is recovered by the inverse "bleaching" (U(1) decoupling) operation. In this new picture, the spurious poles are propagators of the dyed state, and the hidden factorization relations follow from BCJ relations of the dyed amplitudes. For multiple operator insertions, this framework uncovers a new scalar-ordering structure that survives the double copy to gravity.
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Quantum Gases

Continuum Neural Momentum Eigenstate for Variationally Solving Quasiparticles

David D. Dai and Marin Soljačić

We design the first neural quantum state for continuum particles that, for any chosen allowed momentum $\mathbf{k}$, is by construction an exact eigenstate of total momentum with eigenvalue $\mathbf{k}$. Our architecture, EVE, enables off-the-shelf VMC to solve for momentum-sector ground states. We test EVE on 2D bosons with mutual $1/r$ interactions, finding that a single unified ansatz is capable of describing four qualitatively different states: superfluid, roton, crystal, and phonon. At different densities, we extract the underlying phase of matter from the dispersion's shape. At $r_s = 20.0$, we see the roton minimum at finite $k$ expected of a superfluid. At $r_s = 100.0$, we see striking zone folding indicative of crystalline order, with periodically spaced minima representing floating crystals connected by phonon arcs in between. Using density-density correlation functions, we confirm the phase diagnoses and probe the excitations' correlation structures. Finally, we analyze the roton's phase texture and find unexpected multi-particle phase strings, formed when several vortex dipoles merge, leaving two vortices connected by a phase slip.
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High Energy Physics (Phenomenology)

Mass Varying Neutrino Oscillation in Teleparallel Gravity

H. Mohseni Sadjadi and H. Yazdani Ahmadabadi

In the Cartan teleparallel formulation of gravity, a scalar field coupled to the torsion tensor can acquire an environment dependent effective mass. This gives rise to a screening effect: Inside dense bodies such as the Sun, the scalar field is suppressed, causing the mass varying neutrino mass to vary with local density. We investigate the impact of this torsion-induced screening on solar neutrino oscillations. The mechanism modifies the standard MSW resonance condition in a distinct way, leading to detectable shift in the flavor conversion probability. Using data from solar neutrino experiments (Super-Kamiokande, Borexino, SNO), we place constraints on the torsion-scalar coupling parameters. Our work provides concrete test of teleparallel gravity through mass varying neutrino oscillations.
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Mesoscale and Nanoscale Physics

Quantum charge pumping in helical systems: A comparative study of short- and long-range hopping

Leila Eslami, Santanu K. Maiti and Fatemeh Bourbour

Using the Keldysh non-equilibrium Green's function approach, we investigate charge pumping through a single-stranded helical structure described by a tight-binding model that includes either short-range hopping (SRH) or long-range hopping (LRH). While quantum pumping has been studied in various low-dimensional systems, the detailed behavior of the spectral current and the pumped dc current in helical geometries in the presence of higher-order electron hopping (beyond nearest neighbors) has not yet been systematically explored. Here, we focus on the interplay between helicity and extended hopping ranges, analyzing how they jointly control the energy-resolved and dc pumped currents under time-periodic end potentials. For LRH, the pumped dc current exhibits pronounced plateau-like regions as a function of chemical potential when energy levels are sparsely spaced – consistent with adiabatic transport – whereas SRH yields more parameter-sensitive currents without clear plateaus. The plateau stability is controlled by the drive frequency: at higher frequencies, Floquet side-band mixing destroys the plateaus, leading to oscillatory currents. The phase dependence remains nearly sinusoidal, and the current vanishes at zero phase lag, confirming the necessity of out-of-phase potentials. Crucially, in helical systems, the decay exponent $(\ell_c)$ acts as an effective structural parameter that can tune both the magnitude and sign of the pumped current, offering a geometric knob for controlling quantum pumping. Our findings not only fill a gap in the understanding of spectral and pumped currents in helical systems with extended hopping but also provide tools that can be applied to analyze similar phenomena in other chiral or quasi-one-dimensional systems.
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Mathematical Physics · Cross-listed from math.SG

Birkhoff conjecture and finite energy foliations in Hill's lunar problem

Lei Liu and Pedro A. S. Salomão

We prove Birkhoff's retrograde orbit conjecture in Hill's lunar problem by showing that the retrograde orbit bounds a disk-like global surface of section for every energy below the critical value. We also obtain a global description of the dynamics through the critical energy level by constructing finite energy foliations for energies slightly above it. The binding of these foliations consists of the retrograde orbit together with the Lyapunov orbits near the critical points. As a consequence, there exist infinitely many periodic orbits and infinitely many trajectories asymptotic to the Lyapunov orbits. The proof combines pseudo-holomorphic curve techniques with a new convexity theorem for Hill's lunar problem. More precisely, we construct an explicit global symplectic change of coordinates under which the bounded regularized component becomes strictly convex up to the critical energy level. This convexity implies strong dynamical consequences, including lower bounds for the Conley-Zehnder indices of periodic orbits, and allows the application of the Hofer-Wysocki-Zehnder theory of finite energy foliations. As a result, we obtain disk-like global surfaces of section below the critical level and $2-3-2$ foliations for energies slightly above it.
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Astrophysics of Galaxies

SIDM and CDM interpretations of the million-solar-mass lensing perturber JVAS B1938+666-$\mathcal{V}$

Xingyu Zhang and Hai-Bo Yu

A $10^6\,M_\odot$ object has recently been inferred from gravitational imaging of the strong-lensing system JVAS B1938+666, exhibiting an unusually dense inner region embedded within an extended envelope, far exceeding expectations for cold dark matter (CDM) halos. Using gravothermal fluid simulations, we show that such a structure arises naturally in self-interacting dark matter (SIDM) halos evolving into a deep core-collapse phase, where a secondary dense central core forms within an extended profile. The resulting density structure closely matches the inferred properties of the lensing object. We also demonstrate that a similar profile could be reproduced in CDM in the presence of an intermediate-mass black hole, but this requires an early-forming progenitor that subsequently loses $5$ orders of magnitude in mass through tidal stripping by the lens galaxy. Whether such a scenario can be realized in realistic cosmological environments remains an open question.
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Quantum Physics

Global Control with the Tavis-Cummings Interaction

Plato Deliyannis and Iman Marvian

We study the controllability of a system of qubits under global control, where control pulses act identically on all qubits. Specifically, we consider a collection of qubits identically coupled to a single bosonic mode, or harmonic oscillator, via the Jaynes-Cummings interaction. This collective coupling, known as the Tavis-Cummings (TC) interaction, has been realized in several quantum computing platforms, including superconducting and atomic qubit systems. Although the qubits do not interact directly with one another, they can become entangled through their common coupling to the bosonic mode. We characterize the group of unitaries that can be implemented on the joint Hilbert space of the qubits and bosonic mode using the TC interaction together with a global $z$ field $J_z$, corresponding to identical z rotations on all qubits. We show that for n>2 qubits the set of realizable unitaries is restricted by an "accidental" symmetry of the TC Hamiltonian, distinct from its "standard" U(1) and permutational symmetries. On the other hand, we find that the Hamiltonian $J_z^2$ breaks this accidental symmetry and, together with the TC interaction and $J_z$, achieves semi-universality: it allows the implementation of arbitrary unitaries that respect permutational and U(1) symmetry, up to certain constraints on the center of the group. In a companion paper, we further analyze this remarkable accidental symmetry and show that it can be understood through Schwinger's bosonic model of angular momentum.
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High Energy Physics (Experiment)

Observation of the decays $B^{+} \to \Sigma_{c}(2455)^{++} \bar{\Xi}_{c}^{\prime-}$ and $B^{0} \to \Sigma_{c}(2455)^{0} \bar{\Xi}_{c}^{\prime0}$

Belle, Belle II Collaborations: M. Abumusabh, A. Aggarwal et al. (+401 more)

We report the first observation of the decays $B^{+} \to \Sigma_{c}(2455)^{++} \bar{\Xi}_{c}^{\prime-}$ and $B^{0} \to \Sigma_{c}(2455)^{0} \bar{\Xi}_{c}^{\prime0}$, with significances of $6.4\,\sigma$ and $5.3\, \sigma$, respectively, including systematic uncertainties. This analysis is based on data samples containing $771.6 \times 10^{6}$ $\Upsilon(4S)$ decays collected with the Belle detector at the KEKB collider and $520.6 \times 10^{6}$ $\Upsilon(4S)$ decays collected with the Belle~II detector at the SuperKEKB collider. The branching fractions are measured to be $\mathcal{B}(B^+ \to \Sigma_c(2455)^{++} \bar{\Xi}_c^{\prime -}) = (1.69 \pm 0.31 \pm 0.12^{+1.39}_{-0.56}) \times 10^{-3}$ and $\mathcal{B}(B^0 \to \Sigma_c(2455)^{0} \bar{\Xi}_c^{\prime 0}) = (1.28 \pm 0.32 \pm 0.10^{+0.26}_{-0.22}) \times 10^{-3}$, where the first and second uncertainties are statistical and systematic, respectively, and the third arises from the uncertainties in the absolute branching fractions of $\bar{\Xi}_{c}^{-}$ and $\bar{\Xi}_{c}^{0}$ decays. This result represents the first observation of $B$-meson decays into a pair of charmed baryon-antibaryon states belonging to the same $SU(3)$ flavor sextet.
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All authors Belle, Belle II Collaborations: M. Abumusabh, A. Aggarwal, H. Ahmed, J. K. Ahn, Y. Ahn, M. Akdag, N. Akopov, S. Alghamdi, M. Alhakami, N. Althubiti, K. Amos, M. Angelsmark, N. Anh Ky, C. Antonioli, K. Arai, H. Atmacan, V. Aushev, R. Ayad, V. Babu, H. Bae, N. K. Baghel, S. Bahinipati, P. Bambade, Sw. Banerjee, M. Barrett, M. Bartl, J. Baudot, A. Beaubien, F. Becherer, J. Becker, G. F. Benfratello, J. V. Bennett, F. U. Bernlochner, V. Bertacchi, M. Bertemes, E. Bertholet, M. Bessner, S. Bettarini, V. Bhardwaj, B. Bhuyan, F. Bianchi, T. Bilka, D. Biswas, A. Bobrov, D. Bodrov, G. Bonvicini, J. Borah, A. Boschetti, A. Bozek, M. Bračko, P. Branchini, R. A. Briere, T. E. Browder, A. Budano, S. Bussino, Q. Campagna, M. Campajola, M. Carminati, G. Casarosa, C. Cecchi, P. Cheema, L. Chen, B. G. Cheon, C. Cheshta, H. Chetri, K. Chilikin, K. Chirapatpimol, H.-E. Cho, K. Cho, S.-J. Cho, S.-K. Choi, S. Choudhury, S. Chutia, J. Cochran, J. A. Colorado-Caicedo, I. Consigny, L. Corona, S. Cuccuini, J. X. Cui, E. De La Cruz-Burelo, S. A. De La Motte, G. De Nardo, G. De Pietro, R. de Sangro, M. Destefanis, S. Dey, R. Dhayal, A. Di Canto, J. Dingfelder, Z. Doležal, X. Dong, M. Dorigo, G. Dujany, P. Ecker, D. Epifanov, J. Eppelt, R. Farkas, P. Feichtinger, T. Ferber, T. Fillinger, C. Finck, G. Finocchiaro, F. Forti, B. G. Fulsom, P. Gagneja, R. Garg, A. Garmash, G. Gaudino, V. Gaur, V. Gautam, A. Gaz, A. Gellrich, G. Ghevondyan, D. Ghosh, H. Ghumaryan, R. Giordano, A. Giri, P. Gironella Gironell, B. Gobbo, R. Godang, O. Gogota, W. Gradl, E. Graziani, D. Greenwald, K. Gudkova, Y. Han, K. Hayasaka, H. Hayashii, S. Hazra, C. Hearty, M. T. Hedges, A. Heidelbach, G. Heine, I. Heredia de la Cruz, T. Higuchi, M. Hoek, M. Hohmann, R. Hoppe, P. Horak, X. T. Hou, C.-L. Hsu, T. Humair, T. Iijima, K. Inami, N. Ipsita, A. Ishikawa, R. Itoh, M. Iwasaki, P. Jackson, D. Jacobi, W. W. Jacobs, E.-J. Jang, Q. P. Ji, S. Jia, Y. Jin, A. Johnson, K. K. Joo, H. Kakuno, K. H. Kang, G. Karyan, F. Keil, C. Ketter, C. Kiesling, C. Kim, D. Y. Kim, H. Kim, J.-Y. Kim, K.-H. Kim, H. Kindo, K. Kinoshita, P. Kodyš, S. Kohani, A. Korobov, S. Korpar, E. Kovalenko, R. Kowalewski, P. Križan, P. Krokovny, T. Kuhr, Y. Kulii, R. Kumar, K. Kumara, T. Kunigo, S. Kurokawa, A. Kuzmin, Y.-J. Kwon, S. Lacaprara, Y.-T. Lai, T. Lam, J. S. Lange, T. S. Lau, R. Leboucher, M. J. Lee, P. Leo, P. M. Lewis, C. Li, L. K. Li, Q. M. Li, S. X. Li, W. Z. Li, Y. Li, Y. B. Li, Y. P. Liao, J. Libby, J. Lin, S. Lin, Z. Liptak, V. Lisovskyi, C. Liu, M. H. Liu, Q. Y. Liu, Z. Q. Liu, D. Liventsev, S. Longo, A. Lozar, T. Lueck, C. Lyu, J. L. Ma, Y. Ma, M. Maggiora, S. P. Maharana, R. Maiti, G. Mancinelli, R. Manfredi, E. Manoni, M. Mantovano, D. Marcantonio, S. Marcello, M. Marfoli, C. Marinas, C. Martellini, A. Martens, T. Martinov, L. Massaccesi, M. Masuda, T. Matsuda, D. Matvienko, S. K. Maurya, M. Maushart, J. A. McKenna, Z. Mediankin Gruberová, R. Mehta, F. Meier, D. Meleshko, M. Merola, C. Miller, M. Mirra, K. Miyabayashi, H. Miyake, R. Mizuk, S. Moneta, A. L. Moreira de Carvalho, H.-G. Moser, N. Mudgal, Th. Muller, H. Murakami, R. Mussa, M. Nakao, Y. Nakazawa, Z. Natkaniec, A. Natochii, M. Nayak, M. Neu, M. Niiyama, S. Nishida, R. Nomaru, S. Ogawa, R. Okubo, H. Ono, G. Pakhlova, S. Pardi, J. Park, K. Park, S.-H. Park, A. Passeri, S. Patra, T. K. Pedlar, L. E. Piilonen, P. L. M. Podesta-Lerma, T. Podobnik, L. Polat, A. Prakash, R. pramanik, V. Prasad, S. Prell, E. Prencipe, M. T. Prim, H. Purwar, P. Rados, S. Raiz, K. Ravindran, J. U. Rehman, M. Reif, S. Reiter, M. Remnev, L. Reuter, D. Ricalde Herrmann, I. Ripp-Baudot, G. Rizzo, S. H. Robertson, J. M. Roney, A. Rostomyan, N. Rout, G. Russo, S. Saha, G. Sanchez, D. A. Sanders, S. Sandilya, L. Santelj, C. Santos, V. Savinov, B. Scavino, J. Schmitz, S. Schneider, G. Schnell, K. Schoenning, C. Schwanda, Y. Seino, K. Senyo, J. Serrano, C. Sfienti, W. Shan, C. P. Shen, X. D. Shi, T. Shillington, T. Shimasaki, J.-G. Shiu, D. Shtol, A. Sibidanov, F. Simon, J. B. Singh, J. Skorupa, A. Soffer, A. Sokolov, E. Solovieva, S. Spataro, K. Špenko, B. Spruck, M. Starič, P. Stavroulakis, S. Stefkova, R. Stroili, M. Sumihama, M. Takahashi, M. Takizawa, U. Tamponi, S. S. Tang, K. Tanida, F. Testa, A. Thaller, D. V. Thanh, T. Tien Manh, O. Tittel, R. Tiwary, E. Torassa, F. F. Trantou, I. Tsaklidis, M. Uchida, I. Ueda, T. Uglov, K. Unger, Y. Unno, K. Uno, S. Uno, Y. Ushiroda, R. van Tonder, K. E. Varvell, M. Veronesi, A. Vinokurova, V. S. Vismaya, L. Vitale, V. Vobbilisetti, R. Volpe, M. Wakai, S. Wallner, M.-Z. Wang, A. Warburton, M. Watanabe, S. Watanuki, C. Wessel, X. P. Xu, B. D. Yabsley, S. Yamada, W. Yan, W. P. Yan, J. Yelton, K. Yi, J. H. Yin, K. Yoshihara, C. Z. Yuan, J. Yuan, L. Yuan, Y. Yusa, L. Zani, F. Zeng, M. Zeyrek, B. Zhang, X. Zhao, V. Zhilich, J. S. Zhou, Q. D. Zhou, L. Zhu, R. Žlebčík

High Energy Physics (Theory)

Coherent Entanglement between Massive Oscillators from the Quantized Gravitational Field

Anom Trenggana and Freddy P. Zen

In this work, we investigate how entanglement between two massive quantum particles trapped in harmonic oscillator potentials is generated after they interact with propagating modes of the quantized gravitational field. Specifically, we consider only the entanglement arising from the coherent contribution of the gravitational field to investigate its causal structure. We employ the Feynman-Vernon influence functional approach, within which the contribution of the coherent gravitational field to entanglement generation can be traced to the commutation relation of the gravitational field. Our analysis shows that entanglement does not arise instantaneously after the interaction begins. Instead, there is a time delay proportional to the separation between the two particles before entanglement begins to develop. This result shows that the entanglement arising from the coherent contribution of the gravitational field exhibits a causal structure. The magnitude of the resulting entanglement is generally very small. However, when the initial quantum states of the two particles are prepared as separable squeezed states, the resulting entanglement can be enhanced, with the magnitude of the enhancement depending exponentially on the squeezing parameter.
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Fluid Dynamics

Longitudinal particle separation

Siluvai Antony Selvan, Rahil N Valani, Brendan Harding et al. (+1 more)

Owing to inertial effects, the flow through a three-dimensional curved duct focuses finite-sized spherical particles in the two-dimensional cross-section onto either stable equilibrium points or limit cycles. This hydrodynamic inertial focusing underpins various biomedical and industrial applications for size-based particle and cell sorting. Departing from conventional particle separation in the channel cross-section, we instead focus on particle separation in the primary flow direction, i.e., longitudinal separation. We consider a duct with an elliptical centreline and a tall rectangular cross-section. For a given particle size, the nature of the cross-sectional equilibrium points depends on the local radius of curvature of the duct, and a periodical variation of the radius of curvature can result in a periodical bifurcation behaviour along its length. In particular, a duct geometry that undergoes a periodically varying saddle-node infinite-period (SNIPER) bifurcation can be used to improve longitudinal, at the expense of cross-sectional, particle clustering. For sufficiently large particles, this longitudinal clustering weakens at higher Reynolds numbers and with decreasing eccentricity, in contrast to small particles whose longitudinal clustering remains unaffected across a wide range of geometric configurations and flow conditions. Then, ducts with smaller eccentricities enable simultaneous separation along both the flow direction and the cross-section. In contrast, for larger eccentricities, the emergence of a SNIPER bifurcation promotes more pronounced longitudinal separation while compromising cross-sectional separation. These preliminary findings suggest that elliptically wound microfluidic devices might be used for longitudinal separation of particles by size, with potential biomedical and industrial applications.
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All authors Siluvai Antony Selvan, Rahil N Valani, Brendan Harding, Yvonne M Stokes

Quantum Physics

Quantum Otto engine powered by an anisotropic Heisenberg XYZ model under independent local magnetic fields

Meiru Li, Maimaitiyiming Tusun, Fang Zhao et al. (+2 more)

We study a quantum Otto heat engine whose working substance is an anisotropic two-qubit Heisenberg XYZ model. Independent local magnetic fields are used to control each spin individually. The influence of the longitudinal coupling, anisotropy, transverse coupling, and local fields on the net work output and efficiency is systematically examined. Reducing the longitudinal coupling is found to markedly improve both the maximum work and the peak efficiency. The engine performance reaches an optimum at a particular value of the anisotropy parameter. A local work analysis clarifies how work is produced during the cycle. Because of the asymmetric local fields and the intrinsic spin-spin interaction, the two qubits play markedly different thermodynamic roles; the interaction term itself contributes crucially to the total work. We further analyze the variation of quantum entanglement, quantified by concurrence, along the cycle. The results indicate that a pronounced change in entanglement between the hot and cold isomagnetic strokes is closely correlated with the efficiency enhancement. This work offers new insight into the operating principles and control of quantum Otto heat engines.
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All authors Meiru Li, Maimaitiyiming Tusun, Fang Zhao, Hasiyatihan Abudoula, Tongcheng Wei

High Energy Physics (Phenomenology)

A simple solution to the monopole problem: SU(5) GUT with symmetry breaking into special subgroup

Yu Hamada and Naoki Yamatsu

Grand unified theories (GUTs) predict the overproduction of magnetic monopoles, leading to the so-called monopole problem, which is often addressed by cosmological inflation that dilutes their abundance. However, if inflation occurs before the GUT symmetry breaking, monopoles are produced afterwards and the problem persists. This motivates the exploration of alternative mechanisms. We propose a simple solution based on the Langacker–Pi mechanism within an $SU(5)$ GUT framework with symmetry breaking into its special subgroup. In particular, after the gauge symmetry is broken to the Standard Model (SM) gauge group $SU(3)_C\times SU(2)_L\times U(1)_Y$ by the vacuum expectation value of an adjoint scalar, it is further broken to $SO(3)_C\times SO(2)_L$. This structure is naturally realized by introducing a symmetric tensor scalar, a singlet scalar, and multiple singlet fermions. During this intermediate phase, the monopoles become connected to antimonopoles by cosmic strings, which enhances their pair annihilation and reduces their abundance. Subsequently, the symmetry is restored to the SM gauge group. The restoration transition can be either first-order or second-order, depending on the model parameters. In the case of a first-order phase transition, a stochastic gravitational-wave (GW) signal is generated. For a certain region of the parameter space, the resulting signal can lie within the sensitivity of future GW experiments.
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Optics

Omnidirectional photonic chiral flatband in nonlocal membrane metasurfaces

Baohe Zhang, Jumin Qiu, Meng Qin et al. (+7 more)

Omnidirectional flat-band resonances, characterized by an enhanced photonic density of states and inherent angular robustness, are highly sought-after in integrated nanophotonic devices, particularly when integrated with chiral functionality. Here we realize such resonances in a nonlocal silicon membrane metasurface patterned with periodic square-lattice air-hole arrays. Increasing the lattice period not only compresses the Brillouin zone but, crucially, weakens the evanescent coupling between neighbouring Bloch modes associated with the same-order guided resonances. Driven by the tight-binding model in the limit of weak inter-unit-cell coupling, the pronounced band flattening of the degenerate guided resonance along both $k_{x}$ and $k_{y}$ yields, giving rise to an omnidirectional flat-band resonance. Remarkably, both numerical simulations and experiments reveal a universal route for endowing flat-band guided resonances with optical chirality through the deliberate breaking of the mirror symmetry of air holes. As a result, the omnidirectional chiral flat-band resonance emerges along both principal in-plane directions, with $Q$-factors exceeding 10$^{3}$ and circular dichroism greater than 0.9 over a wide angular range of $\pm 5^{\circ}$. Nonlinear measurements further show that the resulting resonance not only drives highly efficient third-harmonic generation but also imparts a pronounced spin-selective character to the nonlinear process. Simultaneously, the highly efficient nonlinear process also enables chirality-controlled frequency-upconversion imaging. Our results establish a general paradigm for engineering omnidirectional chiral flat-band resonances in planar silicon platforms, opening new opportunities for nonlinear nanophotonics and chiral imaging.
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All authors Baohe Zhang, Jumin Qiu, Meng Qin, Haiyan Jiang, Shuyuan Xiao, Zhiwei Zheng, Leman Kuang, Hui Jing, Xinxing Zhou, Hongju Li

Earth and Planetary Astrophysics

Ultraviolet Imaging of SR 12 c with HST/WFC3: Accretion and Variability of a Giant Planet at the End Stages of Growth

Claire O. Finley, Brendan P. Bowler, Ya-Lin Wu et al. (+12 more)

Many details of the gas accretion phase during giant planet formation remain untested. We present new 0.2$\unicode{x2013}$0.7 $\mu$m UV-through-red optical imaging of the young, wide-orbit planetary-mass companion SR 12 c from the Wide Field Camera 3 (WFC3) instrument on board the Hubble Space Telescope. SR 12 c exhibits strong accretion-related continuum excess blueward of $\sim$5000 $\unicode{x212B}$ and clear signs of the Balmer jump at 3646 $\unicode{x212B}$. We derive a total accretion luminosity of 1.65 $\pm$ $0.19 \times 10^{-5} L_{\odot}$ and a mass accretion rate of 8 $\pm$ $2\times 10^{-12}$ M$_{\odot}$ yr$^{-1}$. Based on its mass and age, SR 12 c will not grow by an appreciable amount at its current accretion rate; it is at the end stages of assembly. No accretion variability is evident between the two epochs of the WFC3 observations spanning a month-long baseline, but the H$\alpha$ emission line strength decreases by 90% compared to the reported flux from five years earlier. Combined with previous observations of SR 12 c, we assemble one of the most complete spectral energy distributions of a young giant planet to date, spanning the UV through sub-mm wavelengths (0.2$\unicode{x2013}$880 $\mu$m). This adds SR 12 c to the small yet growing sample of planets with detailed accretion and disk constraints, which together are beginning to establish the diversity of timescales and physical processes governing the formation of giant planets.
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All authors Claire O. Finley, Brendan P. Bowler, Ya-Lin Wu, Adam L. Kraus, Yifan Zhou, Yuhiko Aoyama, William Best, Ian Czekala, Catherine C. Espaillat, Katherine B. Follette, Gregory J. Herczeg, Raquel A. Martinez, Connor E. Robinson, Quang H. Tran, Kimberly Ward-Duong

Materials Science

Leveraging rapid sintering to retain metastable zirconia in copper

Wangshu Zheng, Xi Chen, Xuyang Feng et al. (+6 more)

Cermets combining metastable ceramics and ductile metals promise superior toughness and strength. However, retaining metastability often requires high-temperature sintering that coarsens microstructures and relaxes matrix constraint. Here we introduce an ultrafast high-temperature sintering (UHS) strategy to overcome this trade-off in zirconia-copper cermets. By applying Joule heating at around 100 degrees C per second to 900 degrees C with only a 20 second hold, we obtained cermets containing up to 50 weight percent of metastable austenite in zirconia at room temperature within a fine-grained and homogeneous microstructure. The rapid sintering kinetically favors semi-thermal austenite formation while suppressing copper grain growth and matrix relaxation, thereby stabilizing the high-temperature phase and simultaneously preserving microstructural refinement. This approach offers significant potential for copper-based composites in applications such as transformation toughening, self-healing, and crack detection.
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All authors Wangshu Zheng, Xi Chen, Xuyang Feng, Aiji Zou, Andrew Yun Ru Ng, Xiaoqing Wang, Zhili Dong, Qiang Guo, Chee Lip Gan

Quantum Physics

Quantum walk-based optimisation for capacitated vehicle routing with homogeneous and heterogeneous fleets

Edric Matwiejew, Aidan Smith, Callum Neill et al. (+3 more)

The capacitated vehicle routing problem (CVRP) is an appealing candidate for quantum optimisation due to its combinatorial complexity and practical importance. However, the problem's constrained search space poses a challenge for such quantum algorithms. We introduce a quantum walk-based optimisation algorithm (QWOA) for the CVRP with homogeneous or heterogeneous vehicle fleets, addressing this challenge through a continuous-time quantum walk over a product space that coincides with combinatorial structures intrinsic to the CVRP solution space. Relative to the prior QWOA-based formulation, this approach reduces the per-layer gate complexity from $\mathcal{O}(n^{3}\log n)$ to $\mathcal{O}(n^{2}\log n)$ and supports a circuit parameterisation schedule generated by a fixed number of classical parameters. Exact state-vector simulation on instances with up to $n=8$ customers and $K=3$ vehicles demonstrates improved convergence to low-cost solutions using markedly fewer objective function evaluations, with the advantage broadening as problem size increases. These results identify structured product-space walks as a promising tool for optimisation over constrained combinatorial spaces.
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All authors Edric Matwiejew, Aidan Smith, Callum Neill, Paulo Santos, Ugo Varetto, Jingbo Wang

Optics

Candidate overtone shear horizontal SAW resonators in thin-film lithium niobate for intermodal acousto-optic modulation

Wenbing Jiang, Xuankai Xu, Yu Guo et al. (+5 more)

The merits of thin-film surface acoustic wave (SAW) devices are pivotal to develop the high-performance intermodal acousto-optic modulators. In this work, we have proposed shear-horizontal (SH) SAW resonators for anticipated intermodal acousto-optic modulation on the thin-film lithium niobate platform. Through optimization of the cut angle of LN films, the SAW wavelength, and the thickness of interdigital transducer (IDT) electrodes, the calculated acousto-optic overlap factors utilizing SH0 modes are improved by more than an order of magnitude compared with those of Rayleigh modes. Furthermore, we have fabricated and characterized three kinds of proof-of-principle SH0 mode devices without/with grating reflectors. The electromechanical coupling coefficients (keff^2) and quality factors (Q) in the overtone resonators with grating reflectors are systematically evaluated, featuring the highest Q of 843 with the compromised keff^2 of 0.96%-4.72%. The results reveal that the temperature coefficients of frequency (TCF) of Rayleigh modes vary across various overtones, whereas the SH0 modes exhibit TCFs in the range of 32.3-68.9 ppm/C. Our fabricated SH0-mode overtone resonators demonstrate the capability of operating at power levels up to 29 dBm without electrode damage, offering a promising paradigm for robust and high-efficiency intermodal acousto-optic modulators with potential applications in integrated optical signal processing, microwave photonics,and quantum information technologies.
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All authors Wenbing Jiang, Xuankai Xu, Yu Guo, Boyu Zhang, Lihui Jin, Xiao Chen, Tao Wu, Libing Zhou

Astrophysics of Galaxies

Supermassive Black Hole Assembly from Heavy Seeds with Dynamical Friction in the BRAHMA Simulations: Implications for JWST, LISA, and the Local Universe

Aklant K. Bhowmick, Laura Blecha, Paul Torrey et al. (+8 more)

The JWST discoveries of supermassive black holes (BHs) at $z \gtrsim 5$ may provide key insights into their seeding origins. Using new $[18{-}72~\rm Mpc]^3$ BRAHMA cosmological simulations, we investigate how variations in heavy-seed prescriptions, coupled with a subgrid dynamical friction model, shape BH populations at $z \sim 5$ and $z \sim 0$. We consider two "lenient” seed models, in which all halos containing sufficient dense & metal-poor gas form $\sim10^4$ and $\sim10^5~M_{\odot}$ seeds, and a "strict” seed model, in which $\sim10^5 M_{\odot}$ seeds form only under additional constraints motivated by direct collapse black hole formation. By $z \sim 5$, all models produce $M_*-M_{\rm BH}$ relations broadly consistent with the observed local Universe for $M_*\gtrsim10^9~M_{\odot}$ galaxies, but only the lenient scenarios generate systems near the upper envelope of the observed local scatter. In galaxies hosting $M_{\rm BH} \sim 10^8$-$10^9~M_{\odot}$ BHs, lenient production of $\sim10^5~M_{\odot}$ seeds also produces multiple overmassive systems with $M_{\rm BH}/M_* \gtrsim 0.01$. Although their growth is dominated by seeding and mergers, these systems reach luminosities of $\sim10^{43}$-$10^{45}\mathrm{erg s^{-1}}$, comparable to those inferred for JWST-detected BHs. As a key observational signature, the lenient seed models yield merger rates of $\gtrsim100\mathrm{yr^{-1}}$ and near-unity local BH occupation fractions even in galaxies with $M_* \lesssim 10^7~M_{\odot}$. In contrast, the strict seed model produces merger rates of only $\sim1\mathrm{yr^{-1}}$ and local occupation fractions of $\lesssim10\%$ for galaxies with $M_* \lesssim 10^8~M_{\odot}$. Future gravitational-wave event rates and measurements of local BH occupation fractions will therefore provide strong constraints on the dominant pathways responsible for high-redshift BH assembly.
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All authors Aklant K. Bhowmick, Laura Blecha, Paul Torrey, Luke Zoltan Kelley, Rachel S. Somerville, Rainer Weinberger, Priyamvada Natarajan, Tiziana Di Matteo, Lars Hernquist, Mark Vogelsberger, Alex M. Garcia

High Energy Astrophysical Phenomena

Constraining inhomogeneities and asymmetries in SNe, FBOTs, and other high-energy transients from unresolved radio observations

Fabio De Colle, Rosa L. Becerra, Lizeth A. Meza et al. (+7 more)

Synchrotron emission in high-energy transients is produced by relativistic electrons accelerated by shocks. As high-energy transients are often unresolved even on angular scales probed by very long baseline interferometry, it is difficult to obtain a full picture of the ejecta and circumstellar medium (CSM) properties that are probed by the radio synchrotron emission. Radio spectra of high-energy transients frequently show optically thick slopes shallower than the standard $F_\nu \propto \nu^{5/2}$ expected from synchrotron self-absorption (SSA) models, or broader spectra near the self-absorption frequency. Such deviations are often interpreted phenomenologically, without providing clear insights into the structure of the emitting region. We show how information on the homogeneity and symmetry of the emitting region can be directly inferred from SSA spectra, even when the source is unresolved. We discuss the circumstances under which inhomogeneities in the emitting region can change the spectrum below the self-absorption frequency, causing it to follow a different slope. We examine which parameters can be constrained from observations and which remain degenerate. We apply this method to the stripped-envelope supernova (SN) 2016coi and to the fast blue optical transient (FBOT) AT2018cow, showing that SSA spectra constrain the degree of inhomogeneity in these systems, providing strong evidence for inhomogeneities in the emitting region in the SN 2016coi, and asymmetry in the case of AT2018cow, and we infer the characteristics of the emitting region. When well sampled spectra are available, our method can be applied as a general, model-independent, inference method. This approach can be used to constrain inhomogeneities in a variety of unresolved high-energy astrophysical transients, including SNe, FBOTs, tidal disruption events and gamma-ray bursts.
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All authors Fabio De Colle, Rosa L. Becerra, Lizeth A. Meza, Nayana A.J., James K. Leung, Luca Izzo, Raffaella Margutti, Gerardo Urrutia, Enrique Moreno-Méndez, Leonardo García-García

Instrumentation and Methods for Astrophysics

Connecting Polarization to Exoplanet Yield Calculations for HWO

Jaren N. Ashcraft, Scott D. Will, Maxwell A. Millar-Blanchaer et al. (+6 more)

The Habitable Worlds Observatory (HWO) aims to enable the detection and characterization of Earth-like planets around Sun-like stars to search for possible signs of life elsewhere in our universe. This requires an incredibly sensitive coronagraph instrument that suppresses the light from the star by a factor of 10 billion, which must contend with error terms that have not previously limited high-contrast instrumentation at lower levels of starlight suppression. Polarization aberrations are one such source of error that is particularly problematic for coronagraphy on a large space telescope. Optical rays in large, compact astronomical observatories can have large changes in angle of incidence over the beam, which induce polarization aberrations that decrease sensitivities to faint signals at small angular separations. Limiting variation in angles of incidence along the optical path could lead to longer, less stable observatories. This could negatively impact the total number of exo-Earths HWO would be able to detect. This study links open-source physical optics modeling tools to an exoplanet yield optimizer to understand how polarization aberrations influence science return for HWO. We also explore how polarization aberrations scale with change in angle of incidence, which could drive the primary-secondary mirror distance and overall observatory stability. In the visible, we find that decreasing the EAC-1 barrel from 16m to 12m results in $\approx 10^{-10}$ contrast at the IWA where we expect exo-Earths to be. In the UV we appear to be less sensitive to polarization because exo-Earths are farther from the IWA. We also find a limited range over which the design reference mission of EAC-1 can be optimized to compensate for polarization aberrations using altruistic yield optimization. We then report on mitigation strategies to minimize the presence of polarization aberrations in HWO.
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All authors Jaren N. Ashcraft, Scott D. Will, Maxwell A. Millar-Blanchaer, Breann Sitarski, Christopher C. Stark, Ewan S. Douglas, John Krist, Brian Kern, Manuel Quijada

Data Analysis and Statistics

Interpretable model-free inference of parametric variation across time-series data through large-scale feature extraction

Ben D. Fulcher, Carl H. Lubba, Giorgio F. Gilestro et al. (+2 more)

Here we address the problem of estimating the dimensionality and nature of parametric variation in an unknown generative process directly from time-series data, without specifying or fitting a model. In particular we suppose that inter-instance variation in collections of time series is caused by parametric variation in the generating model. We hypothesize that, given a sufficiently large library of time-series features, low-dimensional parametric variation will manifest as low-dimensional structure in feature space, enabling interpretable estimators of the underlying degrees of freedom to be constructed. We test our hypothesis using a library of over 7000 diverse and interpretable time-series statistics and thirteen simulated systems with known parametric variation, spanning linear stochastic processes, nonlinear oscillators, and chaotic dynamics. Our unsupervised, data-driven approach often reconstructs the underlying parametric variation across this extensive range of simulated dynamical systems while also yielding interpretable estimators for each underlying dimension. Applied to the movement dynamics of 1143 fruit flies, we use this method to extract biologically meaningful components corresponding to sex and circadian rhythmicity. Our results pave the way for much-needed data-driven methods to bridge the gap between interpretable theoretical understanding of dynamics and the large and complex datasets that characterize modern scientific problems.
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All authors Ben D. Fulcher, Carl H. Lubba, Giorgio F. Gilestro, Simon R. Schultz, Nick S. Jones

High Energy Astrophysical Phenomena

Data-driven modeling of Galactic diffuse emission with multi-wavelength observations

Xi Liu, Xiaodong Li, Sujie Lin et al. (+4 more)

We present a data-driven investigation of Galactic diffuse emission. Using multi-frequency Planck radio/microwave maps (30-857 GHz) and Fermi-LAT gamma-ray data (50 MeV-814 GeV), we construct a nonlinear mapping between radio emission and gamma-ray intensity through supervised machine learning. Our models achieve high predictive accuracy (R^2 > 0.90 in the 0.1-10 GeV range), demonstrating that multi-frequency radio observations encode sufficient information to reconstruct both spatial morphology and spectral properties of diffuse gamma-ray emission. By analyzing model performance across different frequency bands and spatial regions, we identify high-frequency radio bands as the dominant predictor, providing direct empirical support for the hadronic origin of Galactic 0.1-10 GeV gamma rays, while low-frequency radio bands for the leptonic origin above 10 GeV. Residual maps reveal coherent large-scale structures, including Loop I and III, highlighting regions where standard interstellar emission models are incomplete or biased. Compared with the GALPROP model, our machine learning approach yields a higher R^2=0.95 and lower mean absolute relative error (14.7%) in the inner Galactic disk and the Galactic center region. Our results illustrate that machine learning serves as a physically interpretable tool for multi-messenger astrophysics, providing a data-driven baseline for separating non-standard emission components and deriving new constraints on cosmic-ray propagation and interstellar medium structure.
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All authors Xi Liu, Xiaodong Li, Sujie Lin, Yihan Liu, Chengyu Shao, Lili Yang, Le Zhang

Exactly Solvable and Integrable Systems

Calculation of solitons derived from quivers

Takashi Ichikawa

We associate each quiver with soliton solutions of nonlinear integrable systems containing the KP and Toda hierarchies. We give an explicit and computable formula of these soliton solutions which are regarded as universal ones obtained by degenerating quasi-periodic solutions.

Mathematical Physics · Cross-listed from math.AP

Optimal minimax formula for bounds on ensemble averages of statistically stationary three-dimensional Navier-Stokes flows

Anne Bronzi, Cecília F. Mondaini and Ricardo M. S. Rosa

We establish an optimal upper bound formula for ensemble averages of flow quantities associated with the three-dimensional incompressible Navier-Stokes equations. The formula takes the form of a minimax problem, extending the framework developed by Tobasco, Goluskin, and Doering (2018) for finite-dimensional systems and by Rosa and Temam (2022) for the two-dimensional Navier-Stokes equations. The lack of global well-posedness for the 3D case presents a significant challenge, which we overcome by working within the space of Foias-Prodi stationary statistical solutions. The minimax formula is derived by exploiting suitable compactness and continuity properties of specific subspaces of probability measures under the weak topology of the phase space. A distinguishing feature of our result is the characterization of the maximizing measures: unlike the previous cases, the optimal bounds in 3D are achieved on extreme points that are specific convex combinations of at most two Dirac delta measures, instead of exactly one, a structure that naturally appears from the constraints given by the mean energy dissipation inequalities in the characterization of the Foias-Prodi stationary statistical solutions.
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Medical Physics · Cross-listed from eess.IV

Acquisition state behaves as a structured, measurable variable governing lung-nodule AI: kernel-driven measurement instability and noise-driven detection fragility, invisible to DICOM metadata

Daniel Soliman

AI governance for medical imaging is formalizing: the 2026 ACR-SIIM Practice Parameter recommends local acceptance testing and ongoing drift monitoring, and the ACR Assess-AI registry monitors AI outputs using DICOM metadata for context. We argue that a necessary, currently unmonitored layer sits beneath output metrics: whether incoming studies remain within the acquisition envelope a model was validated on. Using a LUNA16-trained MONAI RetinaNet lung-nodule detector, we test whether acquisition state behaves as a structured, measurable variable. On real paired CT differing only in reconstruction kernel (NLST B30f vs B80f), kernel alone shifted AI-measured diameter and flipped a Fleischner size category in 5.2% (8 of 155) of nodules at fixed patient and acquisition, while detection confidence was unchanged (Wilcoxon p=0.22). Under controlled LIDC-IDRI perturbations the effects dissociated by axis: the noise axis degraded detection confidence (p=5.9e-32, concentrated in nodules under 6 mm) but not measurement, while the frequency/kernel axis corrupted measurement (p=8.6e-13) but not detection. A 4-feature pixel fingerprint recovered reconstruction identity (patient-level AUC about 0.95 on real CT, 0.995 on a QIBA phantom) where the ConvolutionKernel DICOM tag was uninformative (identical labels across reconstructions). The kernel axis transported across four manufacturers (leave-one-vendor-out AUC 0.94-0.98, matching the within-vendor ceiling). Acquisition state thus maps to distinct AI failure modes, frequency content to measurement reliability and noise to detection sensitivity, and is not recoverable from metadata. Acquisition-aware, input-side validation is the missing layer for the acceptance-testing and drift-monitoring requirements now entering imaging-AI accreditation.
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Cosmology and Nongalactic Astrophysics

Geometric obstruction to resolving the Hubble tension: orthogonality of scale and shape in distance measurements

Zhihuan Zhou, Zhuang Miao, Sheng Bi et al. (+2 more)

We identify a geometric obstruction to resolving the Hubble tension by combining early-time sound-horizon reduction with late-time smooth dark energy. Within $\Lambda$CDM, the BAO–SN matter-density gap $\Delta\Omega_m = 0.037$ is exactly invariant under the sound-horizon rescaling $\alpha \equiv r_s^{\rm mod}/r_s^{\Lambda{\rm CDM}}$, and late-time $w(z)$ deformations cannot eliminate this gap either: reconciling the two datasets requires opposite deformations – phantom ($w < -1$) for BAO, quintessence ($w > -1$) for SN at $z < 0.5$ – an anti-alignment quantified by $\cos\theta = -0.97$ in $w(z)$ space. A full MCMC analysis of DESI DR2 BAO, Planck plik\_lite, and Pantheon+ bears this out: the optimal $\alpha^* = 0.992$ ($0.8\%$ $r_s$ reduction) brings the joint fit to $H_0 = 70.3 \pm 0.3\;\mathrm{km\,s^{-1}\,Mpc^{-1}}$, still $3.2\sigma$ below SH0ES, with the inter-dataset tension reduced but not removed. The obstruction reflects not a shortage of model freedom but an irreducible disagreement between probes. The deformation space $\{\alpha, \beta_{\rm damp}, w(z)\}$ already spans $93\%$ of the $\Omega_m$ response direction; nonetheless BAO and SN constrain $\Omega_m$ through independent channels and disagree, while the residual $H_0$ deficit, anchored by the local distance ladder, resides in the absolute distance scale that $w(z)$ reshapes but cannot rescale.
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All authors Zhihuan Zhou, Zhuang Miao, Sheng Bi, Chaoqian Ai, Hongchao Zhang

General Relativity and Quantum Cosmology

Strong deflection limit-analysis using Picard-Fuchs equation in Einstein-Maxwell-Dilaton spacetime

Tadashi Sasaki

We consider the deflection of light by a spherically symmetric and electrically charged black hole solution in the Einstein-Maxwell-Dilaton theory with specific values of the dilaton coupling constant where the deflection angle can be represented as elliptic integrals. We show that the deflection angle as a function of two dimensionless variables $(s,z)$, which are related to the background charge and the impact parameter, respectively, satisfies a system of 2nd-order linear partial differential equations called the Picard-Fuchs (PF) equations. For each case of the dilaton coupling, the PF equations lead to 1st-order ordinary differential equations with respect to the variable $s$ for the constants $\bar{a}$ and $\bar{b}$ in the log-formula for the strong deflection limit. Using the Hamiltonian system associated with Painlevé VI equations, which holds as a result of the integrability of the PF equations, we solve the equations for $\bar{a}$ and $\bar{b}$. By requiring consistency with the Schwarzschild case in the zero-charge limit, $\bar{a}$ and $\bar{b}$ for nonzero charge are uniquely determined.
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