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Physics

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Tuesday 8 September

Mesoscale and Nanoscale Physics

Probing Antialtermagnetism via Orbital-Field-Induced Spin Splitting

Zi-Ting Sun

Layer compensation can conceal spin polarization behind a spin-degenerate bulk spectrum in antialtermagnets, preventing spectroscopic identification of the underlying magnetic order. Here we show that the orbital effect of an in-plane magnetic field converts the hidden spin texture into an observable spin splitting with momentum parity opposite to that of the underlying exchange order, thereby restoring spectroscopic access. Once the parity is determined, complementary response functions in the weak-field regime further resolve its wave character. Within a minimal model, we illustrate that a sum rule over the difference of spectral functions between opposite spins isolates the momentum gradient of the form factor and differentiates hidden even-parity orders, whereas for odd-parity sectors the induced net spin polarization exhibits characteristic field-amplitude and angular dependences. These results establish orbital-field-induced spin splitting as a generic route to identifying the hidden altermagnetic order parameter without layer resolution.
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General Relativity and Quantum Cosmology

Second-order Teukolsky calculations for nonspinning, quasicircular binaries

Benjamin Leather, Andrew Spiers, Adam Pound et al. (+4 more)

Currently, the only second-order gravitational self-force calculations have been based on directly solving the perturbative Einstein equations in the Lorenz gauge. That method relied on the complete separability of the Einstein equations in a Schwarzschild background. In this paper, we present a new scheme based on the second-order Teukolsky equation. Crucially, this method promises to extend (reasonably straightforwardly) to the more realistic case of a Kerr background. Here we implement the scheme in the simplest setting of quasicircular orbits around a Schwarzschild black hole. In addition to working with the Teukolsky equation, our scheme incorporates several other advances over previous second-order self-force calculations: compactified hyperboloidal slicing, transformation to a Bondi-Sachs gauge, and a combination of spectral and variation-of-parameters methods. We also use these tools to re-examine the infrared divergences that arise in second-order Lorenz-gauge calculations, showing they are less pronounced in the Teukolsky case and completely eliminated in the Bondi-Sachs gauge. We conclude by calculating the asymptotic energy fluxes and benchmarking them against previous Lorenz-gauge calculations.
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All authors Benjamin Leather, Andrew Spiers, Adam Pound, Samuel D. Upton, Barry Wardell, Leanne Durkan, Niels Warburton

High Energy Physics (Phenomenology)

A Vector-Like Lepton Interpretation of the High-Energy Nuclear Recoil Candidate in LUX-ZEPLIN

Fatemeh Elahi and Pedro Schwaller

The LUX-ZEPLIN (LZ) experiment has recently reported a nuclear-recoil candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}\,{\rm keV}$ in an exposure of $2.84\,{\rm tonne\,yr}$. At this unusually high recoil energy, the spin-independent (SI) xenon response is strongly suppressed, motivating dark matter interactions with a harder recoil spectrum. We show that elastic spin-dependent (SD) scattering through the nonrelativistic operator $\mathcal O_4=\mathbf S_{\rm DM}\cdot\mathbf S_N$ provides a simple realization of such a spectrum. We consider singlet-doublet Majorana dark matter, for which a diagonal $Z$ coupling generates the required SD interaction. The accompanying Higgs-mediated SI interaction would generically produce too many low-energy recoils, but can be suppressed along a Higgs blind spot while retaining a nonzero $Z$ coupling. We find a region of the Higgs blind spot that simultaneously predicts an $\mathcal O(1)$ event rate in the LZ high-recoil window and reproduces the observed thermal relic abundance. The same SD interaction leads to solar capture, allowing this region to be tested independently with solar-neutrino searches. Current IceCube limits already probe part of the LZ-compatible thermal parameter space, while a viable region remains. Additional xenon exposure and improved solar-neutrino searches can therefore provide complementary tests of this interpretation.
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General Relativity and Quantum Cosmology

TARTARUS: A High-Performance Python Code for Ray Tracing in Curved Spacetimes

David F. Bambague and Alexis Larrañaga

The recent observations of the supermassive black holes M87* and Sagittarius A* by the Event Horizon Telescope collaboration (EHT) have shown the need for robust, efficient, and accessible numerical tools to model light propagation in strongly curved spacetimes. Comparing theoretical accretion models with observational data relies heavily on ray-tracing algorithms that calculate the trajectories of photons traveling from a source plasma to a distant observer. In this paper, we present TARTARUS (Tracer for Astrophysical Ray Trajectories Around Relativistic Ultra-compact Sources), a new, highly modular, and extensible Python-based framework for computing null geodesics around compact objects. By leveraging Just-In-Time (JIT) compilation via Numba, TARTARUS bridges the gap between Python's high-level accessibility and the execution speed of compiled languages like C++ or FORTRAN. The code supports multiple native solvers (including adaptive embedded Runge-Kutta pairs, a Bulirsch-Stoer extrapolator, and a Verlet scheme), event-detection mechanics for handling structural intersections (e.g. event horizons and accretion disks), and support for both analytical and numerically generated background metrics. We demonstrate the code's physical accuracy and computational efficiency through some tests, including the evaluation of the Hamiltonian constraint conservation and ray-tracing of the shadow and the Novikov-Thorne thin accretion disks around a Kerr black hole.
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Astrophysics of Galaxies

Triaxiality of the Milky Way dark matter halo and the microlensing optical depth towards the Large Magellanic Cloud

J. García-Bellido and M. R. S. Hawkins

The microlensing optical depth towards the Large Magellanic Cloud (LMC), $\tau_{\rm LMC}$, bounds the compact-object fraction of the Galactic dark matter halo, but is almost always evaluated for a spherical halo. We compute it for triaxial haloes and show that the shape dependence is carried entirely by the projection of the line of sight onto the halo principal axes: for a scale-free halo $\rho\propto R^{-\alpha}$ at fixed local density it factorises exactly as $\tau/\tau_{\rm sph}=S_\odot^{\alpha}\langle S^{-\alpha}\rangle_w$, with $S(\Omega)$ the ellipsoidal shape function. The LMC lies only $0\fdg78$ from perpendicular to the Sun-Galactic Centre line, making it a near-optimal probe of in-plane elongation and a poor probe of vertical flattening. For the halo shapes favoured by Gaia we find $\tau_{\rm LMC}/\tau_{\rm sph}=0.95$–$1.15$ at fixed local density, $1.57$ for the Law-Majewski logarithmic potential, and $0.67$–$1.54$ when the major-axis azimuth is left free. For the Einasto halo required by the declining Gaia DR3 rotation curve, truncation near $25\kpc$ is offset by the larger local density it implies and $\tau$ falls by only $7$–$15$ per cent; but the median lens distance moves inwards from $13.4$ to $8.5\kpc$, where the logarithmic slope is steep and rising, amplifying the shape sensitivity: the Gaia RR~Lyrae enhancement grows from $15$ to $23$ per cent and the orientation-free range widens to $0.62$–$1.62$. The systematic on the inferred MACHO or primordial-black-hole fraction is two-sided, of order $\pm15$ per cent for the measured shapes and a factor $2.6$ under full orientation freedom, exceeding the statistical errors of the EROS-2 and OGLE bounds.
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Other Condensed Matter

Exact Phase-Space Rotation in the Trapped Quantum Calogero Model

Akash Sarkar

We develop a microscopic phase-space description of the quantum Calogero model in the presence of an external harmonic confining potential. Building on the quantum Lax-pair structure, we construct a Hermitian Wigner operator whose expectation value obeys the exact phase-space evolution equation d_t rho + lambda d_x rho - Omega^2 x d_lambda rho = 0 for arbitrary initial states and to all orders in the interaction strength. The resulting dynamics is a rigid rotation in phase space with period 2 pi/Omega, providing a microscopic realization of the isochronous dynamics of the trapped Calogero model. We further show that the moments of the phase-space density form rotating multiplets rather than independent conserved quantities. In particular, within the quadratic sector, the unique conserved combination is proportional to the trapped Hamiltonian, providing a nontrivial consistency check of the construction. In the limit Omega -> 0, the equation reduces to the exact free-streaming equation of the untrapped model.
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Mathematical Physics

The inverse problem of time-dependent density functional theory on the torus

Asbjørn Bækgaard Lauritsen, Mathieu Lewin and Jakob Oldenburg

We prove that, for any given sufficiently regular one-particle density, there exists a unique external potential for which the solution to the many-body Schrödinger equation has this prescribed density. This implies in particular that one can exactly reproduce the time-dependent density of an interacting system using non-interacting electrons, which is at the heart of time-dependent density functional theory. Our result covers the Coulomb interaction and densities arising from extended nuclei.
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Materials Science

Time-Dependent Density Functional Theory with Coulomb Interactions

Asbjørn Bækgaard Lauritsen, Mathieu Lewin and Jakob Oldenburg

We provide the first fully rigorous justification of time-dependent density functional theory in the continuum: Given a time-dependent density, we prove that there exists an external potential, unique up to a time-dependent constant, such that the corresponding Schrödinger equation reproduces the given density. This potential can be obtained with an iteration scheme. Our argument covers Coulomb interactions and does not need any Taylor expansion in time. It instead requires analyticity in space for the density and potential, which is compatible with extended nuclei.
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Mathematical Physics · Cross-listed from math.PR

The Ding-Song-Sun inequality for a class of even ferromagnets

Omar Abdelghani, Roland Bauerschmidt, Thierry Bodineau et al. (+1 more)

Ding-Song-Sun proved the remarkable correlation inequality that the truncated two-point correlation function of ferromagnetic Ising models with arbitrary mixed-sign external field is largest when the field vanishes. This inequality has various important consequences such as log-Sobolev inequalities for Ising and $\varphi^4$ models up to and at the critical point. We extend the DSS inequality to the class of single spin measures satisfying the GHS condition. This is an important ingredient in our proof of the log-Sobolev inequality for the massless sinh-Gordon model on $\mathbb{R}^2$ in a forthcoming article.
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All authors Omar Abdelghani, Roland Bauerschmidt, Thierry Bodineau, Benoit Dagallier

Earth and Planetary Astrophysics

TEMPUS: Relativistic coordinate time scales for any solar-system body from arbitrary ephemerides

Yan Seyffert and Agnès Fienga

Precise time-scale transformations between solar-system bodies are an essential requirement for deep-space science and solar system navigation. The post-Newtonian relativistic expression relating a body-centered coordinate time TCX to the Barycentric Coordinate Time TCB depends on the gravitational environment and velocity of the target body, and must be evaluated consistently with the chosen planetary ephemerides. So far only INPOP has provided such a solution as part of its ephemerides releases, albeit only for Earth with TCG-TCB. We present TEMPUS, a tool that numerically integrates the IAU 2000 time-transformation for any solar-system body using positions and velocities from an arbitrary ephemerides. We provide a validated, ephemerides-agnostic implementation of TCX-TCB and assess its accuracy against published independent solutions. The rate $d\,\mathrm{TCX}/d\,\mathrm{TCB}$ is integrated with an Adams-Moulton order-12 predictor-corrector. The gravitational potential sum tested here includes the Sun, eight planets, Pluto, up to 343 main-belt asteroids, and 30 trans-Neptunian objects. Outputs can be stored in readable format tables of sampled values or as Chebyshev coefficient files. Comparisons are performed against the TU Dresden Klioner time solutions, the TCG-TCB solution provided with INPOP19a and INPOP21a, and the LTE440 lunar solution. For the planetary bodies TEMPUS agrees with Klioner at the $10^{-21} s\,s^{-1}$ level over 200 yr. Against the INPOP19a released TCG-TCB we also agree to the same level. The main-belt asteroids as well as the trans-Neptunian objects shift the planetary time scales at the $10^{-18} s\,s^{-1}$ level, and the choice of planetary and lunar ephemerides contributes differences on the $10^{-18} s\,s^{-1}$ level as well. TEMPUS provides a validated, ephemeris-agnostic post-Newtonian time-transformation for any solar-system body.
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Materials Science

Water, vacancies, and competing exchange interactions in Prussian blue analogues: a neutron diffraction study of field and dehydration-driven magnetic transitions

N. S. Dhami, C. V. Colin, V. Nassif et al. (+5 more)

We report a neutron diffraction study of the structural and magnetic properties of a family of ferro- and ferrimagnetic Prussian blue analogues (PBAs), $A_4$[Fe(CN)$_6$]$_{2.7}$ ($A$ = Co, Mn, Ni), Rb$_2$Ni$_4$[Fe(CN)$_6$]$_{3.3}$, and Mn$_4$[Cr(CN)$_6$]$_{2.7}$, as a function of temperature (2–450~K) and applied magnetic field. All bimetallic compounds of the Fm$\overline{3}$m family exhibit a broad diffuse feature at low scattering angle, which we identify, through comparison with the cation-stabilized Rb$_2$NiFe framework, as an intrinsic signature of correlated vacancies and their associated interstitial water. High-temperature diffraction reveals a continuous crossover from positive to negative thermal expansion in CoFe and MnFe upon dehydration, while NiFe remains structurally robust up to 450~K. At low temperature, all compounds order in a collinear ferrimagnetic state with propagation vector $\mathbf{k}=(0,0,0)$, except MnFe, which adopts a partially frustrated magnetic structure with $\mathbf{k}=(1,0,0)$. A moderate magnetic field of $B_c = 1.3$~T drives a spin reorientation in MnFe toward the collinear $\mathbf{k}=(0,0,0)$ ferrimagnetic state common to the other compounds; the same transition is independently induced by dehydration. A minimal Heisenberg model shows that this transition results from a near-compensation between antiferromagnetic Mn–Fe coupling and a geometrically frustrated antiferromagnetic Mn–Mn interaction on the face-centered-cubic Mn sublattice, placing MnFe in the vicinity of a magnetic compensation point. These results resolve a longstanding ambiguity in the interpretation of the Fe $K$-edge XMCD response of MnFe-based PBAs, and establish water content as a key parameter controlling both the structural and magnetic stability of this family of materials, with direct relevance to their use as battery electrodes.
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All authors N. S. Dhami, C. V. Colin, V. Nassif, O. Fabelo, T. Nait, A. Bleuzen, A. Bordage, V. Balédent

Quantum Physics

Restart and first detection in a lackadaisical quantum walk with flat-band localization

Debraj Das

We study stochastic and sharp restart in a one-dimensional lackadaisical discrete-time quantum walk with self-loop weight $\ell$. In the absence of restart, the dynamics has a flat band responsible for intrinsic localization and two dispersive bands supporting ballistic propagation. We compare two initially localized benchmark states: a flat-band-active state with finite flat-band overlap and a flat-band-dark state with zero flat-band overlap. For geometric stochastic restart with per-step restart probability $q$, the stationary mean-squared displacement scales as $q^{-2}$ as $q\to0$. In the same limit, the restart-site occupation probability approaches the restart-free intrinsic localized value for the flat-band-active state, whereas for the flat-band-dark state it vanishes as $q\ln(1/q)$. For power-law restart, where $p_m\propto m^{-s}$ is the probability that the waiting time to the next restart is $m$ steps, a normalized stationary site-occupation distribution exists only for $s>2$, while the stationary absolute spatial moment of order $p$ is finite only for $s>p+2$. In the regime $1<s\leq2$, at every fixed lattice site, the flat-band-active occupation converges to the intrinsic flat-band profile, while the flat-band-dark occupation tends to zero. We also consider monitored first detection with sharp restart, in which the walk is reinitialized after a fixed number $r$ of consecutive unsuccessful measurements. For fixed $r$, the mean first-detected-passage time of the flat-band-active state exhibits a minimum at an intermediate self-loop weight, whereas the flat-band-dark state approaches a ballistic detection limit as $\ell\to\infty$.
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General Relativity and Quantum Cosmology

Can the Universe Change Signature When Gravity is Dynamical?

Yaghoub Heydarzade

Can a universe undergo a regular Euclidean-Lorentzian signature transition when the gravitational coupling itself is dynamical? We address this question in scalar-tensor gravity with nonminimal coupling $F(\phi)R$. Although the spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) sector can be mapped to the Einstein frame for $F>0$ and a nondegenerate scalar redefinition, not all transition properties are frame independent. For a finite, positive, and sufficiently regular conformal factor, the existence and transverse character of the type change are preserved, whereas the extrinsic geometry is not. We therefore use the Einstein frame as a solution-generating representation and impose total geodesy in the physical Jordan frame. We construct two exactly integrable classes of solutions. In the oscillator-ghost-oscillator branch, the scalar field is stationary at the transition and Jordan-frame total geodesy follows under suitable regularity assumptions on the conformal factor. In the critical exponential-potential branch, the scalar is generically nonstationary and total geodesy instead requires \begin{equation*} H_E\big|_\Sigma = \frac12 \left( \frac{d\ln F}{d\psi} \right)_\Sigma \dot\psi_\Sigma . \end{equation*} We also distinguish this condition from the stronger smoothness requirements of a Kossowski-Kriele-type transverse metric. Finally, while the canonical Einstein-frame scalar does not allow effective phantom evolution, the dynamical nonminimal coupling can generate a locally superaccelerating Jordan-frame regime near the transition when $\left(\frac{d\ln F}{d\psi}\right)_\Sigma>0$ for the chosen oscillator branch. Thus signature change persists beyond Einstein gravity, with regularity and effective cosmological behavior remaining intrinsically frame sensitive.
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Astrophysics of Galaxies

Euclid: Quick Data Release (Q1) – Exploring the detailed visual morphology of galaxies in clusters

P. Mas-Buitrago, S. Kruk, D. O'Ryan et al. (+167 more)

Galaxy clusters provide unique laboratories for studying environmental effects on galaxy evolution. The morphology–density ($T$–$\Sigma$) and morphology–cluster-centric radius ($T$–$R$) relations trace how galaxy morphology is influenced by the environment, but previous studies at intermediate redshifts have been limited in both sample size and radial coverage. We use the Euclid Quick Data Release 1 (Q1) visual morphology catalogue to measure the $T$–$\Sigma$ and $T$–$R$ relations for smooth, featured-or-disc, and barred galaxies in known clusters at $0.2\leq z\leq 0.5$, extending this analysis to large cluster-centric distances ($3 R_{500c}$) and studying their dependence on stellar mass. Using photometric redshifts and stellar masses provided by Euclid, we identify 1754 cluster members within $1.5 R_{500c}$, distributed across 71 clusters. We classify the identified galaxies as smooth, featured-or-disc, or barred using the predicted vote fractions provided by the Zoobot deep learning foundation model in the Q1 visual morphology catalogue. We confirm the $T$–$\Sigma$ relation in all the stellar mass ranges studied, with a stronger influence of the cluster environment on galaxy morphology in the densest parts of the cluster and closer to the cluster centre. Beyond $1.5 R_{500c}$, the morphological segregation weakens, with featured-or-disc galaxies overtaking smooth galaxies at the lowest densities, consistent with the growing contribution of field interlopers in the cluster outskirts. For barred galaxies, we find a tentative decline of the bar fraction toward lower densities that is most pronounced for the most massive galaxies. In conclusion, our results show that the cluster environment drives a progressive transformation of galaxy morphology, with the loss of disc structure becoming more pronounced towards the cluster core, where environmental processes act most efficiently.
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All authors P. Mas-Buitrago, S. Kruk, D. O'Ryan, M. T. Nardone, A. La Marca, P. Awad, M. Baes, M. Fossati, T. Géron, Z. Ghaffari, M. Girardi, C. J. Lintott, J. G. Sorce, B. Altieri, F. Durret, V. Pettorino, B. Y. Irureta-Goyena, B. Simmons, J. Reerink, H. Domínguez Sánchez, J. H. Knapen, F. Shankar, E. Duran-Camacho, J. M. Pérez-Martínez, M. Walmsley, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, P. Battaglia, A. Biviano, M. Bolzonella, A. Bonchi, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, M. Cropper, H. Degaudenzi, G. De Lucia, H. Dole, F. Dubath, X. Dupac, S. Dusini, A. Ealet, M. Fabricius, M. Farina, R. Farinelli, S. Ferriol, P. Fosalba, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, P. Gómez-Alvarez, J. Gracia-Carpio, A. Grazian, F. Grupp, S. Gwyn, W. Holmes, I. M. Hook, F. Hormuth, A. Hornstrup, M. Huertas-Company, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, S. Maurogordato, E. Medinaceli, M. Melchior, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, E. Munari, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, W. J. Percival, A. Pezzotta, S. Pires, G. Polenta, M. Poncet, L. A. Popa, L. Pozzetti, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, B. Rusholme, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, M. Scodeggio, A. Secroun, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, A. Veropalumbo, Y. Wang, J. Weller, A. Zacchei, G. Zamorani, F. M. Zerbi, E. Zucca, J. Macias-Perez, M. Sereno

Earth and Planetary Astrophysics

Interplanetary Dust Ablation Seeds Silicate Clouds in Exoplanet Atmospheres

Sven Kiefer, Gregory J. Gosselin, Caroline V. Morley et al. (+1 more)

Interplanetary dust particles (IDPs) are present throughout the Solar System, with Earth experiencing a mass flux of roughly 100 tonnes of IDPs per day. These particles ablate in the upper atmosphere, delivering aerosols that form noctilucent and stratospheric clouds. Since IDPs are present in exoplanet systems as exozodiacal dust disks (exozodis), it is likely that exoplanets experience a constant infall of IDPs as well. In this work, we investigate the effect of IDPs on the cloud structure of gas-giant exoplanets and brown dwarfs, and determine their observability. We apply the microphysical cloud model Nimbus to the Sonora Diamondback model grid to cover a wide range of effective temperatures, surface gravities, atmospheric mixing constants, and IDP mass fluxes. Our results show that IDP infall increases cloud particle number densities, decreases cloud particle radii, and enhances silicate features in transmission and thermal emission spectra. Exoplanets with lower atmospheric mixing rates, effective temperatures, and gravity are more sensitive to IDPs. Most notably, they lead to observable silicate absorption features in colder planets where silicate clouds would otherwise not be observable. WASP-107 b is an example of such an exoplanet with observational evidence of silicate particles. Using Nimbus, we found that a 100 times Earth-like IDP mass flux with a Solar-System-like IDP composition of quartz (SiO2), enstatite (MgSiO3), and iron (Fe) can explain the observations of high altitude silicate particles in WASP-107 b.
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All authors Sven Kiefer, Gregory J. Gosselin, Caroline V. Morley, Sean P. S. Gulick

Quantum Physics

First fault-tolerant quantum memory demonstration for a generalized superfast encoding

James Brown and Kenny Heitritter

The Generalized Superfast Encoding (GSE) is a fermion-to-qubit mapping that has error-correcting/detecting properties. To this point, all demonstrations have been relegated to error-detection only, as no fault-tolerance under circuit-level noise has been observed. Here, we introduce an even-distance $d$ constant stabilizer-weight GSE where each of $N$ modes is assigned a $d$-qubit block arranged on a ring. The resulting stabilizer generators have constant weight 4 or 6 for any even distance $d$. Furthermore, the full stabilizer set of this construction can always be partitioned into four qubit-wise commuting groups, which enables compact syndrome-extraction scheduling. We simulate quantum memory experiments under circuit-level depolarizing noise for two instances of this code, $[[48,8,6]]$ and $[[64,8,8]]$ and the threshold is observed to be $\approx 4\times10^{-3}$. This is, to our knowledge, the first fault-tolerant quantum-memory characterization of a fermion-mapping with threshold-like scaling.
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High Energy Physics (Theory)

Quantum spacetime and gravity from the IKKT matrix model: an invitation

Harold C. Steinacker

This is a concise and compact introduction to a framework for spacetime, gravity, and fundamental physics based on the IKKT matrix model, focusing on conceptual and structural aspects. The approach rests on nontrivial vacua or matrix backgrounds, which serve as 3+1-dimensional noncommutative spacetime. We discuss a specific class of backgrounds describing expanding homogeneous and isotropic FLRW spacetime, which provide a solution of the one-loop effective action with finitely many dof per volume. Perturbations of the background give rise to fields propagating on spacetime governed by a weakly-coupled gauge theory, as well as a nonstandard description of (quantum) gravity leading to some IR modifications. Maximal supersymmetry of the model is essential to ensure effective locality.
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Fluid Dynamics

ONE CYLinder: A Benchmark for Graph-Based Surrogate Modeling of Unsteady Bluff-Body Flows

Théodore Michel, Antoine Campos, Alban Dujardin et al. (+3 more)

Graph-based surrogate models offer a promising route to accelerate computational fluid dynamics (CFD) simulations on unstructured meshes. However, their development is limited by the scarcity of benchmark datasets spanning multiple flow regimes and standardized protocols for long-horizon autoregressive prediction. We introduce ONECYL (ONE CYLinder), a new benchmark for unsteady flow past a circular cylinder across laminar, transitional, and high-Reynolds-number regimes. The benchmark comprises 450 high-fidelity Variational Multiscale finite-element simulations (270,000 flow snapshots) with randomized cylinder geometries, providing time-resolved velocity and pressure fields together with mesh connectivity, geometric descriptors, Reynolds numbers, and integrated aerodynamic quantities. Beyond the dataset, ONECYL establishes a unified evaluation framework combining full-field rollout errors, virtual probes, and drag and lift predictions to assess numerical accuracy and physical fidelity. To accompany the benchmark, we develop a Graph Transformer as a reference baseline predicting velocity and pressure fields autoregressively on unstructured meshes. Using ONECYL, we investigate geometric representations and physics-based regularization across the three Reynolds-number regimes. The results show that explicitly encoding the cylinder geometry through a level-set representation consistently improves long-horizon prediction accuracy and generalization to unseen geometries, while divergence-based regularization becomes increasingly beneficial as flow complexity increases. The ONECYL benchmark and its Graph Transformer baseline provide a reproducible framework for evaluating graph-based surrogate models and establish a foundation for future research on long-horizon prediction of unsteady bluff-body flows.
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All authors Théodore Michel, Antoine Campos, Alban Dujardin, Henry Areiza, Philippe Meliga, Elie Hachem

Solar and Stellar Astrophysics

An analysis of four stellar rings

E. Paunzen, J. Florian, A. Gütl-Wallner et al. (+9 more)

About 50 years ago, one thousand ring-like structures (called stellar-rings) were discovered by Isserstedt (1968). They were believed to be groups of young stars formed by shell-like triggered star formation, which would make them excellent tracers of spiral arms, for example. Neglected for 40 years, we used highly accurate kinematic, astrometric, and photometric data to investigate the four most prominent stellar rings. The aim is to investigate if those structures are indeed physically related groups of stars. We used proper motions and parallaxes from the Gaia DR2 to calculate distances and to search for common properties. Color-magnitude diagrams using BVJHKs measurements were investigated and isochrones fitted. None of the four stellar rings consists of a physically related group of young stars. The location of stars in the line-of-sight mimics a ring-like structure on the sky. The color-magnitude diagrams are typical for an integrated field population and not for a young star cluster, for example. The currently available data are sufficient to analyze ring-like structures with a high statistical significance. This allows a new search for such structures in the Milky Way.
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All authors E. Paunzen, J. Florian, A. Gütl-Wallner, A. Herdin, E. Kralofsky, K. Leschinski, M. Mach, H.M. Maitzen, M. Prišegen, M. Rockenbauer, M. Rode-Paunzen, S. Wallner

Cosmology and Nongalactic Astrophysics

Optical Depths from the Thermal Sunyaev-Zel'dovich Effect with ACT DR6 and DESI DR1 Spectroscopic Galaxies and Optically-Selected Clusters

J. E. Moore, C. Popik, Y. Gong et al. (+66 more)

We present stacked thermal Sunyaev-Zel'dovich (tSZ) effect measurements for three samples of galaxy groups and clusters: those traced by the Dark Energy Spectroscopic Instrument Data Release 1 (DESI DR1) luminous red galaxies (LRG) and the DESI DR1 Bright Galaxy Sample (BGS), and an eROMaPPer optically-selected sample from the DESI Legacy Imaging Survey. We use the latest Atacama Cosmology Telescope DR6 (ACT)+Planck component-separated internal linear combination (ILC) Compton-$y$ maps and ACT+Planck coadded 90, 150, and 220 GHz temperature maps to extract the tSZ signal within a $\sim2'$ disk aperture for sources binned by luminosity, richness, or mass. We measure the average tSZ signal with high statistical significance, with signal-to-noise ratios surpassing 38 for LRG, 27 for BGS, and 39 for the eROMaPPer sample using the 90 GHz ACT DR6+Planck map. We conduct a detailed study of systematics and foregrounds such as dust and cosmic infrared background (CIB) contamination, which remain a core challenge for tSZ analysis. For the LRG and BGS samples, we find that dust and radio source emission dominate the tSZ signal at scales near and below the disk aperture radius. Large-scale ($R>4'$) contamination from the CIB is less significant. We mitigate these contaminants to isolate the tSZ signal and use a combination of simulated and real measurements to develop Compton-$y-$optical depth ($\bar y-\bar \tau$) scaling relations to infer optical depths, which are found to be in agreement with values measured using the pairwise kinematic SZ effect for the same tracer samples. The $\bar y-\bar \tau$ scaling relation for the eROMaPPer sample is the first such relationship to be derived directly from SZ measurements.
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All authors J. E. Moore, C. Popik, Y. Gong, Y-H. Hsu, E. M. Vavagiakis, N. Battaglia, R. Bean, D. Gruen, P. Gallardo, B. Hadzhiyska, G. Ockert, J. Aguilar, S. Ahlen, A. Aviles, F. Beutler, D. Bianchi, J. R. Bond, D. Brooks, E. Bulbul, A. Carnero Rosell, E. Chaussidon, T. Claybaugh, J. Comparat, A. de la Macorra, Biprateep Dey, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gaztañaga, Satya Gontcho A Gontcho, G. Gutierrez, K. Honscheid, M. Ishak, S. Juneau, T. Karim, R. Kehoe, M. Kluge, A. Kremin, A. Kusiak, O. Lahav, M. Landriau, L. Le Guillou, M. Manera, A. Meisner, R. Miquel, T. Mroczkowski, S. Nadathur, J. A. Newman, M. D. Niemack, H. E. Noriega, E. Paillas, W. J. Percival, F. Prada, I. Pérez-Ràfols, C. Ravoux, B. Ried Guachalla, G. Rossi, R. Ruggeri, L. Samushia, E. Sanchez, C. Saulder, D. Schlegel, J. Silber, M. Siudek, G. Tarlé, B. A. Weaver, E. J. Wollack, H. Zou

Strongly Correlated Electrons

Real-time Dyson expansion for the nonequilibrium $GW$ approximation: Correlated spectra and dependence on the reference propagator

Erik Schroedter, Jan-Philip Joost, Michael Bonitz et al. (+1 more)

Electronic spectra provide direct insight into the excitations and correlations of condensed matter systems. Their description requires electron correlations beyond mean field. In equilibrium, the $GW$ approximation has become the method of choice for many materials. Extending this approximation to nonequilibrium, however, is challenging. Full two-time $GW$ simulations within the nonequilibrium Green's functions approach scale at least cubically with propagation time, whereas improved scaling schemes such as time-local (adiabatic) approximations or the generalized Kadanoff–Baym ansatz usually retain only mean-field character in the spectra. The recently introduced real-time Dyson expansion recovers dynamical correlations in the spectrum at time-linear cost, but has so far been restricted to the second-order Born approximation with mean-field reference propagators. Here we formulate and implement the RT-DE for the nonequilibrium $GW$ self-energy with reference propagators of general form whose off-diagonal evolution is time local. In particular, we assess Hartree–Fock propagators, propagators with statically screened exchange with nonequilibrium screening, and a correlated propagator based on the Hartree–Fock GKBA. Benchmarks against exact diagonalization for a driven two-band lattice model with long-range interactions show that the mean-field and statically screened references yield the most accurate spectra, including satellite structures absent at mean-field level, whereas the GKBA-based approach best captures scattering-induced occupation dynamics, but artificially broadens and splits spectral peaks. When applied to large systems that are beyond the reach of exact methods, the scheme resolves the excitonic replica of the valence band and satellites identified as exciton shake-up, as well as their reshaping with increasing excitation density.
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All authors Erik Schroedter, Jan-Philip Joost, Michael Bonitz, Vojtech Vlcek

Materials Science

Edge-Dominated Twist Mechanics at van der Waals Interfaces

Yifan Shao, Zhaoheng Zhang, Hao Li et al. (+5 more)

Despite the pivotal role of twist in modulating physical properties at van der Waals (vdW) interfaces, the mechanics governing torsional response remain poorly understood. Here, we probe twist mechanics at homo- and heterogeneous vdW interfaces, together with their sliding behaviors within a unified experimental framework. For both systems, the peak torque scales nearly linearly with contact area, in contrast to predictions from linear elastic and rigid models. Remarkably, while the sliding friction of the two interfaces diverges by over three orders of magnitude owing to different scaling laws, the corresponding torque follows the same linear scaling and differs by only about twenty-fold. Large-scale atomistic simulations reveal an edge-dominated yielding mechanism for torsional motion, wherein elastic reconstruction shifts the effective load-bearing region toward the edges, eliminating torque from the contact interior. This mechanism contrasts with the bulk-mediated stress transmission governing translational sliding, a distinction rooted in the different loading geometries inherent to the two motion modes, where torsional loading necessitates perimeter actuation, whereas sliding enables center-driven loading. This symmetry-imposed divergence demonstrates that translational and torsional properties cannot be predicted from one another at vdW interfaces, providing critical insights for the design of dynamically reconfigurable micro- and nanoelectromechanical devices.
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All authors Yifan Shao, Zhaoheng Zhang, Hao Li, Oded Hod, Michael Urbakh, Quanshui Zheng, Xiang Gao, Deli Peng

Soft Condensed Matter

Thermomechanics of dense granular materials: a particle-scale perspective

Matthew R. Kuhn

The paper presents a broad thermomechanic framework for the isothermal rate-independent constitutive behavior of dense granular materials. The essential quantities in this framework are directly measurable in discrete element (DEM) simulations: free energy, dissipation, stress, and strain. The paper proposes that energy and dissipation are governed by two sets of internal variables: fabric variables that control the reversible stiffness and structure variables associated with internal sliding. The relevant fabric variables are identified and measured with simulations. Two hypotheses are considered for the structure variables: the macro-scale irreversible strain and an aggregate measure of the micro-scale frictional forces among sliding contacts. Both hypotheses are tested with simulations, which allow direct calculation of the internal variables. The paper then demonstrates the manner in which the measured variables are applied in incremental constitutive models. Among other findings are the following. (1) Dissipation from contact sliding is pervasive and occurs in all directions of incremental loading. (2) Contact motions are not reversed by a reversal of the strain direction, and contacts continue to slide when loading is reversed. (3) The free energy can not be assumed smoothly differentiable; instead, Gâteaux derivatives must be used with irreversible effects. (4) Basic assumptions of elastoplasticity are contravened: no region of purely reversible strain exists, no uniform yield direction exists, no uniform flow direction exists, and irreversible strain is not proportional to the projected total strain. A three-mechanism elastoplasticity model, however, closely fit the DEM results, and methods are demonstrated for quantifying the model. The results emphasize that advanced constitutive models are needed for capturing the general incremental behavior of granular materials.
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Strongly Correlated Electrons

Positive Temperature Coefficient of Anisotropy due to $d^6L$ Groundstate in $\epsilon$-Fe$_2$O$_3$

Rachel Nickel, Kurt Kummer and Johan van Lierop

Positive anisotropy temperature coefficients ($dK/dT>0$) usually arise from hybridization between magnetic 3d states and strongly spin-orbit-coupled (SOC) subsystems. Yet $\epsilon$-Fe$_2$O$_3$ shows $dK/dT>0$ (125-200~K) without an obvious SOC partner. We study pure and Cr-doped (with weakened Fe-O hybridization) $\epsilon$-Fe$_2$O$_3$ across the transition from low temperature incommensurate to high-anisotropy magnetic phases. We identify a $d^6L$ groundstate in $\epsilon$-Fe$_2$O$_3$ while reduced hybridization yields $d^6 + d^6L^2$ in the Cr-doped system, highlighting metal-ligand hybridization as a route to tune magnetic, electronic and orbitronic properties.
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High Energy Physics (Experiment)

A virtual reality extension for the Geant4 toolkit

Benjamin Jobilal, Muhammad Ansar Iqbal and Jay Hauser

Geant4 is a toolkit for simulating particle interactions in matter that is widely used in particle physics, nuclear physics, medical imaging, and astrophysics. At present, Geant4 visualizations are generally viewed on a conventional, two-dimensional computer display. To enhance immersion, we have developed G4VR, a virtual reality (VR) application that extends Geant4 with VR capabilities, providing a more intuitive and comprehensive way to understand these interactions. The user running G4VR in a headset can get detailed information about individual tracks, interactions, and energy depositions by selecting them with the hand controllers. G4VR also allows the user to examine the chronology of interactions, and includes animations of entire events as immersive movies. G4VR includes built-in event displays of several types that allow a first-time user to easily explore its various functionalities. To interface with Geant4, we have developed a new visualization driver called G4XR that allows direct integration with the Geant4 source code. This enables any Geant4 experiment to be loaded and experienced in VR seamlessly.
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Quantum Physics

Resilience Beyond the Light Cone: Error-Detected Primitives for Practical Dynamic Circuits

Kevin C. Smith, Bibek Pokharel, Satvik Maurya et al. (+1 more)

Dynamic circuits, which augment unitary operations with mid-circuit measurements and classical feedforward, can generate long-range entanglement in constant depth, enabling low-depth primitives ranging from nontrivial state preparation to many-qubit entangling gates. Escaping the light-cone constraints of unitary circuits, however, comes at a cost: these primitives typically require a number of mid-circuit measurements that scales with system size and that, together with feedforward latency, can introduce errors that degrade the long-range entanglement they rely on. Here, we alleviate this tension by showing that many such primitives, when cast into a common framework, admit an error-detection scheme that trades infidelity for postselection overhead with no additional ancillas. Our framework thus unifies and upgrades a broad class of primitives including fan-out gates, multi-qubit Pauli rotations, the preparation of W and higher-weight Dicke states, and certain non-normal matrix product states. We also introduce a reduced-depth, error-detected implementation of the Hadamard test, extending the use cases of dynamic circuits to a key algorithmic primitive. Finally, we establish the practical utility of our scheme through experiments on a superconducting quantum processor. We demonstrate the error-detected preparation of a long-range entangled Bell pair spanning a 100-qubit chain with fidelity $F=0.59\pm0.02$, surpassing the entanglement-certification threshold $F>0.5$ that the baseline dynamic-circuit implementation fails to reach ($0.39\pm0.01$). Separately, we demonstrate constant-depth preparation of W states of up to 20 qubits by consuming GHZ states of up to 40 qubits, finding absolute fidelity improvements of $\Delta F\approx 0.2$ across the largest sizes studied. Altogether, these results bring low-depth dynamic-circuit primitives within practical reach on present-day hardware.
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All authors Kevin C. Smith, Bibek Pokharel, Satvik Maurya, Maika Takita

Solar and Stellar Astrophysics

Now you see me, now you don't: Deep, long-lived obscuration events of white dwarfs by dust and debris from disintegrating planetesimals

J. van Roestel, S. Bhattacharjee, J. A. Guidry et al. (+22 more)

Transiting dust and debris around white dwarfs provide a direct view of planetary disruption. We report six previously non-variable white dwarfs that underwent single, deep obscuration events, including ZTF~J2327+0019, which fully disappeared for more than a year. These discoveries raise the number of confirmed debris-transit white dwarfs to 20. In addition, the systematic search of negative alerts from the Zwicky Transient Facility (ZTF), followed by photometric and spectroscopic observations, also identified three hot ($T\approx 55000$–$92000$ K) irregular variables as candidate debris hosts. The six confirmed events last weeks to years, reach transit depths of 25–100%, and show no recurrence over the 8-yr ZTF baseline. They are therefore much deeper and longer lived than the recurring, minute-scale transits typical of previously known systems. The observed reddening is consistent with dust extinction, and high-speed photometry reveals minute-scale structure in several systems, indicating rapidly moving material close to the white dwarf. ZTF~J2327+0019 also shows a simultaneous WISE infrared brightening, the first observed coincidence of infrared brightening and optical obscuration in a white dwarf. Two of the six hosts, one DAZ and one DBZ, are strongly metal enriched, with accretion rates among the highest known for their spectral types and minimum accreted masses of $3.5\times 10^{19}$ and $2\times 10^{24}$ g. We interpret the one-off transit events as collisions between planetesimal remnants and pre-existing circumstellar debris that trigger collisional cascades: short-timescale variability traces dust-producing fragments crossing the star, while slower changes trace the build-up and clearing of an optically thick dusty structure. In contrast, ZTF~J0436+5728 shows a coherent 5.910-h period, consistent with a rocky body shedding material near the tidal-disruption radius.
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All authors J. van Roestel, S. Bhattacharjee, J. A. Guidry, I. Caiazzo, T. Cunningham, J. J. Hermes, S. Torres, Z. Vanderbosch, A. J. Drake, M. Hollands, B. T. Gänsicke, K. De, T. Prince, A. C. Rodriguez, L. B. Ould Rouis, A. A. Mahabal, E. C. Bellm, M. W. Coughlin, M. J. Graham, D. Hale, G. Helou, J. C. Jaimes, M. Kasliwal, R. R. Laher, R. L. Reed

High Energy Physics (Phenomenology)

Probing the Inert Scalar Sector of the Inert Doublet Model via Vector-Boson Fusion at a Muon Collider

Abdesslam Arhrib, Es-said Ghourmin, Ayoub Hmissou et al. (+2 more)

We investigate the sensitivity of a future high-energy muon collider (MuCs) to the inert scalar sector of the Inert Doublet Model (IDM) through a comprehensive set of $2\to4$ electroweak gauge-boson fusion processes. The scalar spectrum consists of two CP-even neutral scalars: $h$ and $H$, one CP-odd neutral scalar $A$, and a pair of charged scalars $H^\pm$. We assume the neutral scalar $H$ to be the lightest inert state and the dark matter (DM) candidate, while the observed $125$~GeV Higgs boson is identified with the scalar of the Standard Model-like doublet. We consider charged Higgs pair production: $\mu^+\mu^-\to H^+H^-\nu\bar{\nu}$ induced by WW fusion, as well as the associated channels: $\mu^+\mu^-\to HH^\pm\mu^\mp\nu$ and $\mu^+\mu^-\to AH^\pm\mu^\mp\nu$, induced by $WZ$ and $W\gamma$ fusion. Owing to their Vector Boson Fusion (VBF) origin, the corresponding cross sections increase significantly with collider energy, making them particularly well suited for exploration at a high-energy MuCs. We first study the $2\to 2$ subprocesses $WW\to H^+ H^-$ and $WV\to H^+ S_i$, $V=Z, \gamma$ and $S_i=H$ or $A$ and establish the destructive interference among the contributing diagrams. After imposing theoretical consistency requirements and current experimental constraints, including those from DM and collider searches, we evaluate the corresponding signal rates at $\sqrt{s}=3$, $10$, and $20$~TeV. We further perform a detector-level Monte Carlo analysis combined with a cut-based signal-background selection. Our results demonstrate that the sensitivity to inert scalar production increases significantly with collision energy, establishing the 10 and 20~TeV MuCs stages as powerful probes of the IDM inert scalar sector.
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All authors Abdesslam Arhrib, Es-said Ghourmin, Ayoub Hmissou, Larbi Rahili, Bassim Taki

Materials Science

Zirconium Carbide as a High-Temperature Benchmark for the Beyond Quasi-Harmonic Method

Christopher M. Stanley

Molar heat capacity at constant pressure, C_p (T), is a central thermodynamic quantity in materials science, but it remains difficult to calculate accurately from first principles when anharmonic vibrational effects become important. In this work, rocksalt ZrC is used as a high-temperature benchmark for the Beyond Quasi-Harmonic (BQH) method, a prepared-supercell first-principles approach that extracts anharmonic vibrational energy directly from density-functional-theory energy evaluations. The calculated BQH molar heat capacity is compared with CALPHAD reference values, a fully anharmonic thermodynamic-integration calculation, a calculated C_v (T) curve from the present work, and a quasi-harmonic calculation. The BQH curve gives a substantial improvement beyond C_v (T) and beyond the quasi-harmonic approximation. Because ZrC is electronically conductive, an electronic heat-capacity correction was also estimated from the density of states at the Fermi level and added to the vibrational BQH result. This correction brings the calculated molar heat capacity into close agreement with the fully anharmonic theoretical benchmark through approximately 1200 K. These results show that the BQH method fully captures important anharmonic phonon contributions missing from ordinary quasi-harmonic calculations.
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Mathematical Physics

On spatial decoherence in many-body systems

Stefano Marcantoni and Marco Merkli

We study the dynamics of a many-body quantum system strongly interacting with a bosonic reservoir. The coupling is given by a potential operator for the system and it is linear in the field. We show that in the limit of infinite coupling strength the system undergoes instantaneous spatial decoherence. To resolve the decoherence process in time we consider large coupling strengths $\lambda$ and short times scaling as $t\propto \lambda^{-\alpha}$, with $\alpha\ge0$, in the limit $\lambda\rightarrow\infty$. On short time scales $\alpha>1$ the dynamics is trivial while on longer ones $0\le\alpha<1$ the decoherence is instantaneous. We show that the decoherence process is resolved exactly for $\alpha=1$, defining the fine-grained time scale $\tau=\lambda t$. We construct an approximate effective evolution map of the many-body system with controlled error estimates. Generically, the effective dynamics is markovian, but not given by a dynamical semigroup. As a physical application we give a rigorous description of the phenomenon of localization of macroscopic quantum objects in position space.
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