Quantum Physics · Cross-listed from cs.LG
A hybrid quantum-classical neural network for learning to route
Marcus Rolf Peter Ritt, Alexsandro Santos da Rosa Júnior, Marcos Vinicius Reballo et al. (+2 more)
This work studies hybrid
quantum-classical neural networks for learning routing heuristics. Specifically, this paper asks whether small
quantum neural networks can replace parameter-heavy modules inside a competitive
attention-based routing model while maintaining solution quality. For the capacitated vehicle routing problem, encoder feed-forward replacement emerges as the most promising design: it reduces the number of model parameters by 56.6% while keeping the hybrid model close to the classical neural baseline at small and medium instance sizes, although the gap grows for larger instances. This work also compares to classical routing
algorithms, which remain highly competitive and often superior on the fixed Euclidean test sets. Our results therefore do not indicate
quantum advantage or solver dominance, but identify encoder feed-forward replacement as a viable hybrid-module compression strategy for neural combinatorial optimization.
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All authors Marcus Rolf Peter Ritt, Alexsandro Santos da Rosa Júnior, Marcos Vinicius Reballo, Cesar Augusto do Amaral, Fernando Augusto Caletti de Barros
Chemical Physics · Cross-listed from cs.LG
AdaptNTK: Adaptive Uncertainty Quantification and Active Learning for Neural Network Potentials
Prajwal Ananth and Shuwen Yue
Machine learning interatomic potentials bridge the gap between
quantum chemical precision and classical computational speed, enabling molecular dynamics simulations with first-principles accuracy. Their reliability is often improved through active learning, which iteratively expands the training set by identifying uncertain, out-of-distribution configurations. Existing uncertainty-quantification methods often involve a trade-off between computational cost and reliability, and generally cannot account for redundancy as an acquisition batch is assembled. Here, we introduce AdaptNTK, a single-model framework that measures uncertainty as a regularized Mahalanobis distance in empirical neural tangent kernel (NTK) feature space. With the NTK features fixed during acquisition, the uncertainty depends on the acquired configurations but not their reference labels. This allows the uncertainty to be updated recursively after each selection without retraining, reducing redundancy within an acquisition batch. On held-out rMD17 data, AdaptNTK achieves the highest mean correlations with force errors (Spearman 0.68, Pearson 0.71) and matches a three-member ensemble in error retention. In active learning experiments, AdaptNTK achieves the lowest force errors across rMD17 and Transition-1X, with particularly strong performance on transition-state configurations in Transition-1X. AdaptNTK provides a 2.6-fold speedup per Transition-1X cycle relative to the ensemble, providing efficient single-model uncertainty estimation with sequential updates for data-efficient active learning.
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General Relativity and Quantum Cosmology
Dynamical evolution of quantum mutual information in Schwarzschild spacetime
Guosen Ma, Fang Rao, Jingjing Hua et al. (+1 more)
Quantum mutual information is a fundamental quantity for characterizing correlations among
quantum systems. In this work, we investigate the dynamic
evolution of the
quantum mutual information based on Rényi-2
entropy for three-mode Gaussian states in the background of a Schwarzschild black hole. We find that the physically inaccessible mutual information increases with Hawking temperature and eventually saturates, while the physically accessible mutual information exhibits nonmonotonic temperature dependence: it first rises, reaches a peak, then declines toward a finite asymptotic value. This nonmonotonic behavior differs from the monotonic degradation typically observed for Gaussian
entanglement and steering in curved spacetime. Furthermore, we establish several constraint relations governing the distribution of mutual information among subsystems. These findings contribute to understanding the quantumness of
quantum correlations for continuous variable in Schwarzschild spacetime.
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All authors Guosen Ma, Fang Rao, Jingjing Hua, Xiaofen Huang
Solar and Stellar Astrophysics
SPIRITS 19q: Dust Production by a Subsolar-metallicity Carbon-rich Wolf-Rayet Star in NGC 2403
Sam Rose, Ryan M. Lau, Jacob E. Jencson et al. (+20 more)
We present JWST/NIRSpec IFU observations of SPIRITS 19q, the highly
dust-producing carbon-rich (WC) binary candidate located in a subsolar-
metallicity region of the nearby spiral
galaxy NGC 2403. The observations, taken in April of 2024, confirm the association of a dusty outburst observed in 2019 by the Spitzer Space
Telescope with an early-type WC
star. Using models from the Potsdam Wolf-Rayet (PoWR) LMC model grid we find that the WC
star of SPIRITS 19q likely has an especially high mass-loss rate ($\gtrsim$ 10$^{-4}$ $M_{\odot}$ yr$^{-1}$). From the flux peak of the IR transient as measured by Spitzer/IRAC as well as constraints on
dust composition and size from the JWST spectrum, we estimate a total
dust mass formed in the outburst of 6.6 $\pm$ 0.4 $\times$ 10$^{-6}$ $M_{\odot}$. Assuming a minimum orbital period of 12 years, this corresponds to a period-averaged
dust production rate of $\lesssim$ 5.5 $\times$ 10$^{-7}$ $M_{\odot}$ yr$^{-1}$. These observations suggest that even a single WC system can contribute to the
dust budget at subsolar
metallicities, and that such systems are an important source of carbonaceous
dust grains in the early universe.
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All authors Sam Rose, Ryan M. Lau, Jacob E. Jencson, Mansi M. Kasliwal, Andreas A.C. Sander, Howard E. Bond, Michael F. Corcoran, Izumi Endo, Matthew J. Hankins, Olivia C. Jones, Viraj R. Karambelkar, Astrid Lamberts, Thomas Madura, Anthony F.J. Moffat, Patrick W. Morris, Takashi Onaka, Michael E. Ressler, Noel D. Richardson, Christopher M. P. Russell, Itsuki Sakon, J. Sanchez-Bermudez, Gerd Weigelt, Peredur M. Williams
Quantum Physics
Fractal dimension predicts quantum kernel collapse in angle-encoded data
Ana Paula Appel
Angle-encoded
quantum kernels on tabular data collapse when the feature map is wider than the intrinsic dimension of the data. We propose the correlation fractal dimension D2 as an a priori
qubit budget: encode D2 coordinates chosen by FD-ASE instead of the PCA-95% width or all E attributes. On nine data sets and a statevector simulator (n= 32), a one-layer ZZ fidelity kernel at q=D2 stays geometrically alive while the same kernel at the PCA-95% width has already collapsed. The budget is map-dependent: product-state and IQP maps overshoot it; a second ZZ layer undershoots it. Packed dense-angle and re-uploading encodings still live at the fractal q, but not when PCA-95% features are stacked onto those
qubits. Shrinking the angle bandwidth moves the ZZ knee later; stretching it kills the kernel earlier. On IBM
Quantum (ibm_fez, 256 shots, n=8) the one-layer ZZ kernel at the fractal width matches the exact kernel (MAE 0.021); past that width both hardware and simulator have collapsed. The ceiling is a property of the map-data pair at a stated bandwidth, not of the classical table alone.
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Superconductivity
Comment on "Distinct Behaviors of Inner and Outer CuO$_2$ Planes in Quadruple-Layer Cuprate (Cu,C)Ba$_2$Ca$_3$Cu$_4$O$_{11 + \delta}$"
Jeffery L. Tallon
In a recent Letter, Sun et al. report photoemission spectroscopy measurements on the four-layer cuprate (Cu,C)Ba2Ca3Cu4O11 (CuC-1234) in which they resolve two superconducting gaps associated with the inner (IP) and outer (OP) CuO2 planes. CuC-1234 has a Tc as 117 K in a sample previously structurally characterized using
neutron powder diffraction. From the Luttinger sum, the beta-band of the IP was found to be heavily underdoped (p~0.07) while the OP alpha2 bonding band was strongly overdoped (p~0.25). Each revealed a gap with very different momentum and temperature dependences. A large gap on the beta band was found to close at the bulk Tc, while a smaller gap on the alpha2 band closed at 70 K. Such two-gap behavior would indicate weak-coupling between the IP and OP, resulting in a second gap-opening temperature, Tc2, and implying a two-step development of the superfluid density on cooling, first on the IPs then on the OPs. Here, we point out that the observed values of Tc and Tc2 are fully consistent with a long-standing correlation of Tc with a bond-valence sum parameter, V+, calculated from the crystallographic bond lengths. This suggests that Tc2 in the OP is entirely consistent with the local structure of the OP where the value of V+(OP) is reduced by the presence of the apical oxygens and Tc2 reduced accordingly. It is as though two largely decoupled
superconductors are present in the single 1234 compound and their individual pairing temperatures are determined by their local nearest-neighbour structure, reflecting the very short-range physics.
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Fluid Dynamics
Deforming Vortex Force Mapping for Undulating Swimmers
Xingxin Yang, Matteo Liguori, Vedang Joshi et al. (+1 more)
Undulatory propulsion is commonly interpreted through reactive added-mass loading associated with body kinematics and
vortex-induced loading, but their relative contributions to the streamwise force have not been systematically quantified across swimming kinematics. Moreover, existing
vortex-based descriptions do not resolve the signed spatial contribution of vortical flow to the streamwise force. We extend
vortex force map (VFM) attribution to deforming bodies, demonstrated for prescribed two-dimensional undulating swimmers at $Re=5000$ across a range of Strouhal numbers and dimensionless wavelengths. The deforming-body VFM organises the streamwise force as a positive reactive added-mass scale with a signed
vortex-pressure modification. Across the 80 cases,
vortex pressure opposes the reactive contribution in 76 cases. Reference-configuration maps show that the near-body
vortex-pressure contribution is consistently adverse, whereas the wake contribution changes sign across regimes and becomes favourable at high thrust. Net
vortex-pressure assistance occurs only for the high-thrust anguilliform swimmer. A matched high-thrust pair further shows that the case with the higher peak downstream velocity has the smaller signed wake contribution, demonstrating that wake intensity alone does not determine its force effect.
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All authors Xingxin Yang, Matteo Liguori, Vedang Joshi, Juan Li
Solar and Stellar Astrophysics
Age Discrepancy in Three Galactic Cepheid Binaries
Sashwat Prasadh, Hilding R. Neilson and Nancy Remage Evans
SV Per, RW Cam, and KN Cen are
Galactic classical Cepheids found in binary systems along with B-type companions. Each system exhibits an “apparent age discrepancy", where the Cepheid appears significantly younger than its companion. We compute
stellar evolution tracks using the MESA code and compare them with these
stars on the Hertzsprung-Russell diagram to estimate the masses and the corresponding ages. We find that, for two of the systems, the companions appear to be between 1.5 times to double the age of the Cepheids, suggesting that the Cepheids may be rejuvenated merger products of two main-sequence
stars that have since evolved. We find that the third system KN Cen is consistent with single
star evolution when we reevaluate ultraviolet observations and find that the companion is hotter than previously measured. We test this idea using the MESA code for each system by evolving a single
star model and rapidly accreting mass on the main sequence to emulate a merger, and then continuing the
evolution until the model is consistent with the parameters of the Cepheids. The results are consistent with the hypothesis that the Cepheids were originally merger products. We conclude with a discussion of potential observational tests of the merger hypothesis.
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Earth and Planetary Astrophysics
An Upper Limit on Turbulent Viscosity in the Circumjovian Nebula
Konstantin Batygin and Fred C. Adams
Circumplanetary disks are open, dynamic systems sustained by a meridional circulation that draws gas and
dust from the parent nebula along nearly polar streamlines, and ultimately returns some of this material through a viscously driven, in-plane
outflow. In such a disk, the water ice line acts as a site of solid-mass accumulation: inward-drifting icy solids sublimate interior to the ice line, the resulting vapor is advected outward by the gas, and recondensation beyond the ice line resets the material to a small Stokes number. The operation of this drift-mediated loop requires the fragmentation-limited Stokes number of the mass-dominant icy aggregates to exceed the
equilibrium Stokes number at which the radial drift of solids reverses. Because the former scales inversely with the Shakura-Sunyaev viscosity parameter $\alpha$ while the latter is directly proportional to it, this requirement yields a compact upper bound on the vigor of
turbulence in the satellite-forming region. Adopting an actively heated, steady-state circumjovian disk truncated at the
tidal radius, we find a marginal bound of $\alpha\lesssim 10^{-3}$ for an icy-particle fragmentation threshold of $v_f\simeq1\,{\rm m\,s^{-1}}$ - appropriate for cold ice with sticking properties similar to silicate
dust. This bound scales linearly with $v_f$, reaching $\alpha\lesssim5\times10^{-3}$ for more adhesive, warm ice ($v_f\simeq5\,{\rm m\,s^{-1}}$). The bound carries no explicit dependence on the disk's mass flux, and is set entirely by the local thermal state, pressure gradient, and geometry of the circumjovian nebula.
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Astrophysics of Galaxies
Formation of Heavy Seed Black Holes and Little Red Dots-like Compact Clusters in Metal-enriched Star-forming Regions
Sunmyon Chon, Shingo Hirano, Ke-Jung Chen et al. (+1 more)
The origin of supermassive black holes (SMBHs) in the early Universe remains uncertain. While the classical direct-collapse scenario requires pristine gas exposed to intense Lyman-Werner (LW) radiation, recent JWST observations suggest that early growing BHs may reside in compact, metal-enriched environments. We investigate early BH formation using a cosmological radiation-hydrodynamic simulation that self-consistently follows the formation and
evolution of rapidly accreting supermassive
stars (SMSs). We find that intense LW radiation develops in clustered
star-forming regions; by the time the first heavy seed forms, the mass-weighted internal intensity has reached $J_{21}\sim1000$. Most seeds form in weakly metal-enriched gas with [Z/H]$\sim-3$ to $-2$, because the strongest LW fields occur in regions already enriched by previous
stellar feedback. All
halos above $10^9M_\odot$ in our zoom-in region host a BH more massive than $10^5M_\odot$. We construct
stellar spectra using MIST/PHOENIX libraries for normal
stars and $6000~\mathrm{K}$ blackbody spectra for bloated SMSs. Five of eight massive clusters with
stellar masses larger than $10^6~M_\odot$ exhibit intrinsically V-shaped spectra similar to those of Little Red Dots (LRDs). In the most prominent cases, luminous SMSs dominate the red optical emission, although Balmer breaks in normal
stellar populations also contribute. We also identify off-center LRD-like systems in our simulation resembling those recently reported in strongly lensed observations. Our results suggest that heavy-seed formation, compact-cluster formation, and LRD-like continuum emission are linked outcomes of clustered, weakly metal-enriched, strongly irradiated environments.
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All authors Sunmyon Chon, Shingo Hirano, Ke-Jung Chen, Volker Springel
Strongly Correlated Electrons
Bound states, resonances, and their thermodynamic properties in pseudospin-1 systems with short-range impurities
E. V. Gorbar and Pavlo Sukhachov
Bound states and resonances induced by short-range
impurities modeled by circular potential wells are analyzed in the vicinity of flat and dispersive bands in gapped and gapless pseudospin-1 systems. We find that the bound and resonant states derived from the flat band show unusual characteristics originating from the multicomponent structure of pseudospin-1
fermions, which are distinct from those for pseudospin-$\tfrac{1}{2}$
fermions. Contrary to gapped Dirac systems and unlike bound states in the vicinity of the upper dispersive band, the bound states derived from the flat band occur for any value of the total angular momentum. The energies of these bound states with higher angular momentum $j$ tend to decrease with $|j|$. In addition, it is found that their wave functions are localized at the potential well edge and the localization increases with $|j|$. The signatures of the
impurity states in the local density of states are determined. Using the Anderson model for independent electrons in the disorder potential, the thermodynamic potential,
entropy density, and heat capacity are obtained. In the regime dominated by bound states derived from the flat band, the
entropy density monotonically increases with temperature and saturates, whereas the heat capacity exhibits a single maximum.
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Optics
Strong suppression of the photonic density of states in three-dimensional disordered silicon networks
Abraham Aguilar Uribe, Francisco Hernández Alejandre, Mattis Reisner et al. (+4 more)
Photonic bandgaps can open not only in crystalline dielectric materials but also in amorphous structures. Self-uniform amorphous gyroid networks have been proposed as promising disordered photonic architectures. Motivated by numerical studies, we combine direct
laser-writing lithography with advanced materials processing to fabricate these structures from high-refractive-index silicon. Spectroscopic measurements at mid-infrared wavelengths reveal pronounced transmission minima. To investigate the formation of photonic band gaps in amorphous structures, we develop polarization-resolved transmission spectroscopy that separates ballistic and multiply scattered contributions, enabling direct identification of the underlying transport regimes. We observe a strong suppression of diffuse transmission, providing direct experimental evidence for a breakdown of conventional diffuse transport associated with a strongly reduced photonic density of states. Together with large-scale numerical simulations, our results establish the presence of a deep photonic pseudogap in an amorphous three-dimensional dielectric material and open new opportunities for observing disorder-induced localization phenomena, including Anderson localization of light.
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All authors Abraham Aguilar Uribe, Francisco Hernández Alejandre, Mattis Reisner, Geoffroy Aubry, Luis S. Froufe-Pérez, Marian Florescu, Frank Scheffold
Atmospheric and Oceanic Physics
Reconciling the Lack of a Robust Anvil Cloud Amount Response to Warming
Zachary McGraw, Blaž Gasparini, Wouter Mol et al. (+1 more)
The stability-iris hypothesis proposes that tropical anvil cloud amount decreases with warming as anvils rise into environments of greater static stability. Here we show that there is no clear theoretical or simulated link between increasing static stability and anvil amount. We demonstrate analytically that identified sensitivities of static stability and pressure velocity to surface warming arise from decreasing air density aloft, which enters pressure-coordinate formulations but does not represent a process that dynamically constrains anvil formation. An ensemble of RCEMIP simulations verifies that the stability increase is robust yet arises from the air density reduction, and hence is not accompanied by a robust response in anvil amount, convectively driven water convergence into anvil levels, or the efficiency with which this convergence produces cloudiness. Overall, these findings dispel the expectation of a systematic reduction in anvil amount with warming arising from basic physical arguments.
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All authors Zachary McGraw, Blaž Gasparini, Wouter Mol, Aiko Voigt
Earth and Planetary Astrophysics
Accelerating Chemical Kinetics for Exoplanet Atmospheres using Neural Networks
Isaac Malsky, Xi Zhang, Tiffany Kataria et al. (+5 more)
Observations increasingly reveal the coupled radiative, chemical, and dynamical processes that shape
exoplanet atmospheres. Interpreting these atmospheres requires models that can capture this complexity. However, multidimensional models remain fundamentally limited by computational cost, and answering key questions requires simulating the governing physical mechanisms at speeds classical methods cannot achieve. As a result, models often rely on simplifying approximations, such as
equilibrium chemistry, even when those assumptions miss important effects. There is a pressing need for fast and accurate chemical kinetics solvers to model planetary atmospheres. Here we present a machine learning local-box chemical kinetics solver for
exoplanet atmospheres using a residual flow-map architecture. We demonstrate that this surrogate model is several orders of magnitude faster than a classical solver, achieving microsecond-scale inference while retaining percent-level accuracy. The surrogate model covers a parameter space that spans $T=300$-$3000$ K, $P=10^{-6}$-$10^{4}$ bar, $\Delta t=10^{-3}$-$10^{8}$ s, and compositions ranging from $10^{-2}$ to $10^{3}$ times
solar in both C/O ratio and
metallicity. Our model outperforms several commonly used machine learning architectures and performs robustly under the extreme stiffness characteristic of atmospheric chemistry. The machine learning framework presented here is a flexible and efficient approach to emulating state-to-state flow-map problems that commonly arise in numerical simulations.
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All authors Isaac Malsky, Xi Zhang, Tiffany Kataria, Matthew Graham, Ziyu Huang, Boris Bonev, Shang-Min Tsai, Elspeth K.H. Lee
Solar and Stellar Astrophysics
The Formation of Very Close Binary Stars
Maxwell Moe
The majority of very close binaries (orbital periods P < 5 days) are in triples. Previous studies surmised that the tertiary hardened the inner binary via Kozai-Lidov cycles coupled with
tidal friction. Alternatively, the trend could be due to a common origin, e.g., more massive molecular cores and protostellar disks are more likely to fragment twice into a triple and harden the inner binary to very short periods via disk migration. Disk migration occurs during the embedded Class I protostellar phase while secular
evolution with a tertiary occurs on much longer timescales. To determine the dominant migration mechanism, I accurately measure the very close binary fractions of both late-type and early-type primaries in
star-forming environments. After combining five surveys, the late-type Class II/III T Tauri very close binary fraction is F_VCB = 2.1_{-0.5}^{+1.0}%, which is consistent with the measurement for late-type field main-sequence
stars (1.7% +/- 0.1%). More than 85% of very close late-type binaries hardened via disk migration during the Class I protostellar phase. I next measure the OGLE-III eclipsing binary (EB) fractions of young massive
stars in the LMC. The very close EB fractions of massive young
stellar objects (YSOs; F_VCEB = 8.3_{-3.2}^{+4.9}%), OB
stars near massive YSOs (4.7% +/- 0.8%), and OB
stars in small, young H II regions (6.4% +/- 1.5%) are consistent with each other and the measurement for OB
stars in slightly older clusters (4.7% +/- 0.3%). More than 90% of very close massive binaries hardened via disk migration during the embedded protostellar phase.
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General Relativity and Quantum Cosmology
Computing the energy of some timelike singularities
Fernando Ruiz Ruiz
The gravitational energies of timelike singularities in some asymptotically AdS spaces and in the Schwarzschild black hole with negative mass are explicitly computed. In all cases considered, the energy is finite and positive, depends on the geometry around the singularity, and compensates negative energy contributions from the asymptotic boundary, rendering the total gravitational energy positive. The definition used for energy is the on-shell
Hamiltonian of the physical classical action proposed by Hawking and Horowitz~\cite{Hawking-Horowitz}. To deal with the singularity, spacetime is cut off by a timelike regulating boundary surrounding the singularity that is compatible with a foliation of spacetime in constant-time slices. It is shown that the total energy of static AdS-Kasner solutions with timelike Kasner singularities is equal to the energy of the planar AdS black hole, and that the Schwarzschild black hole with negative mass has the same energy as Minkowski space.
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Nuclear Theory
What Are We Talking About When We Talk About Nuclear Reactions
Gregory Potel
This introductory Chapter will try to briefly address 1. the basic physical ingredients that determine the
nuclear spectrum and the associated energy scales; 2. the connection between the observed experimental results, typically in the form of cross sections, and the underlying
nuclear structure presented in the previous point. The nature and scope of the present Chapter is to provide a roadmap of the field of
nuclear reactions theory, and to set the stage for the more detailed discussions in the companion Chapters. The aim is to provide a conceptual framework that will allow the reader to understand how the different reaction theory approaches fit together, and how they relate to the underlying physics of
nuclear reactions. The reader will find in other chapters in this volume detailed discussions about the methods addressing two seemingly quite distinct phenomena: direct and compound
nuclear reactions. We hope that this brief Chapter will help them realize that whenever we are talking about either of these, we are talking about the same thing:
nuclear reactions.
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High Energy Physics (Experiment) · Cross-listed from cs.DC
Client-side transparent caching for remote ROOT data analysis
Dmytro Kovalskyi, Jan Eysermans, Mariarosaria D'Alfonso et al. (+1 more)
High-energy physics analyses often process the same data as physicists refine
algorithms and test new ideas. With data increasingly read from remote storage, each iteration is subject to network latency and depends on network bandwidth and shared-storage throughput, which can vary substantially under load. We present uCache (xrd-ucache), a transparent client-side cache implemented as an XRootD client plugin that requires neither server-side deployment nor changes to analysis code. It uses local storage on the analysis machine as a cache layer between the network and
memory. The cache stores only the data actually read by an analysis. It can also rebuild cached data into a branch-aligned, recompressed form, eliminating most of the input/output and decompression costs of subsequent passes. We
benchmark the cache using the Analysis Grand Challenge top
quark pair analysis on public CMS Open Data compressed with zlib and LZMA. Filling the cache adds essentially no overhead compared with a direct read. Subsequent passes are 1.6-8.8 times faster from the byte cache and 2.1-15.7 times faster from the recompressed cache. For a typical analysis, a 1 TB cache suffices for
datasets of 10-20 TB. The largest improvements occur when the remote data source is heavily loaded or geographically distant.
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All authors Dmytro Kovalskyi, Jan Eysermans, Mariarosaria D'Alfonso, Christoph Paus
Earth and Planetary Astrophysics
Where planetary solids survive sublimation around young and hot white dwarfs
Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner et al. (+2 more)
All observed planetary systems orbiting single white
dwarfs have lived through the hot
stellar transition from an asymptotic
giant branch
star. In this post-nebular transition period, the initial conditions for planetary system
evolution throughout white
dwarf cooling are established. The hottest ($\gtrsim$ 20,000 K) and youngest ($\lesssim$ 20 Myr-old) white
dwarf planetary system host
stars differ significantly from their canonical older and colder counterparts by failing to support solid body accumulation in the immediate vicinity (a few $R_{\odot}$) of the white
dwarf. Here, we analyse the likely locations of both solid-body survival and the sublimated gaseous content during this pivotal epoch, and the consequences. We find that (i) reservoirs of iron-rich, rocky and water-rich asteroids of radius $R$ that later observably enrich, or pollute, the white
dwarf need to remain parked for the first tens of Myr of white
dwarf cooling beyond critical distances of (16 au)$\times(1 {\rm km}/R)^{1/2}$ (for iron), (30 au)$\times(1 {\rm km}/R)^{1/2}$ (for rock) and (130 au)$\times(1 {\rm km}/R)^{1/2}$ (for snow), (ii) sublimation acts much more quickly than radiatively-driven orbital drifts from Poynting-Robertson drag or the Yarkovsky effect, and (iii) although large asteroids ($R \approx$ 10-1000 km) that are kicked on highly eccentric orbits around newly born white
dwarfs could survive sublimation, they may fragment into debris which will sublime before the white
dwarf cools. These results support, but do not necessitate, dynamical origin scenarios of polluted white
dwarfs that feature delayed gravitational instability subsequent to the host
star's asymptotic
giant branch phase at Kuiper Belt-like distances, and beyond.
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All authors Dimitri Veras, Keiji Ohtsuki, Rafael Martinez-Brunner, Takato Nishio, Ryo Tamon
Soft Condensed Matter
Nonlinear force response of modular lattice-based metamaterials
Jochem G. Meijer, Armin Yousefi, Francois Barthelat et al. (+1 more)
Lattice-based metamaterials provide lightweight platforms where local instabilities can govern the global mechanical response, enabling applications in energy routing, vibration isolation, and impact mitigation. Although much progress has been made in controlling deformation and buckling sequences through
geometric design, the behavior of coupled nonlinear units over a large range of strain rates and their history-dependent response is less explored. Here, we investigate
lattice-based mechanical metamaterials whose nonlinear buckling behavior can be harnessed through modular architectures. By combining modular units in series, we show that their interaction gives rise to emergent force responses, including transient weakening and enhanced force attenuation, that are absent in the individual modules. Furthermore, selected designs exhibit training behavior under cyclic loading, transitioning between distinct buckling states and revealing a history-dependent mechanical response. Our results demonstrate that modular, instability-driven metamaterials can be programmed and tuned not only through geometry but also through loading history, opening new avenues for designing a nonlinear stress-response in mechanical systems.
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All authors Jochem G. Meijer, Armin Yousefi, Francois Barthelat, Heinrich M. Jaeger
Quantum Physics
Towards unsupervised representation learning for quantum data: quantum models with inference and generation
Robin Lorenz, Eric Brunner and Marcello Benedetti
With
quantum sensors, simulators and networks emerging, a future of
quantum technology may produce
quantum states as data—that is, coherently rather than as classical measurement records—thus motivating the study of suitable
quantum generalisations of modern machine learning, including the automated, unsupervised extraction of useful representations. Two ingredients are central to the latter: inference, mapping observations to latent representations, and generation, mapping latent states back to synthetic data. Both are related to each other and to joint distributions for training models by the chain-rule of classical probability theory. The fact that
quantum states however lack such universal, standard factorisation property thus poses a challenge. Here we develop a conceptual and mathematical framework for unsupervised representation learning from
quantum data. Models are joint
quantum states over visible and latent systems; state-over-time maps provide a notion of factorisation into a marginal state and inference (generation) channel; models with inference (generation) are ambiguous states—states for which such factorisation obtains—subject to a further consistency condition on extended inference maps as data extension. These stipulations are restrictive: we show that non-trivial models must feature non-linear such maps to the extended space. For three representative state-over-time maps, we completely characterise the ambiguous states, uncovering a hierarchy tied to the positive-partial-transpose (PPT) criterion from
entanglement theory. Notably, the Leifer-Spekkens construction supports inference and generation exactly for model classes of PPT states, thus allowing genuinely
quantum visible-latent correlations. We also formulate
quantum counterparts of exact and approximate inference training, explore weaker notions of data extension and sketch a future research programme.
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Mesoscale and Nanoscale Physics
V. A. S. V. Bittencourt, N. Shabala, R. M. Geilhufe et al. (+1 more)
Lattice vibrations carrying angular momentum give rise to fundamental phenomena such as the
phonon Hall effect and the Einstein-de Haas effect, offering new opportunities for manipulating angular momentum in condensed-matter systems. Generating such circularly polarized
phonons requires either the use of an external
magnetic field, or of polarized light pulses. The latter approach does not require the use of any
magnetic response of the material, but it has limitations, in particular regarding the duration of the pulse. Consequently, any effect stemming from
phonons generated by light pulses is transient. In this paper, we propose the use of a driven electromagnetic cavity as a route to generate a steady-state population of
chiral phonons. We derive a general description of cavity-
chiral phonon interaction, with a particular focus on modes of
chiral cavities. We show that, under optimized conditions, a significant effective
phonon-induced
magnetic field can be generated by means of an external drive with realistic power. Our approach is specially tailored for Gamma point
phonons with THz frequencies, and opens a new route for investigating
chiral phonons with electromagnetic cavities.
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All authors V. A. S. V. Bittencourt, N. Shabala, R. M. Geilhufe, A. Metelmann
High Energy Physics (Experiment)
Improved Threshold for Particle-Induced Magnetic Avalanche in Single-Molecule Magnets Using Fe$_8$ Molecule
Bailey Kohn, Rupak Mahapatra, Ivan Borzenets et al. (+6 more)
Extending the original work on the development of a
magnetic avalanche detector using Mn$_{12}$-ac single-molecule magnet (SMM), we report the results on a significantly lower threshold
magnetic avalanche detector using Fe$_8$ SMM. Fe$_8$ has an order of magnitude smaller relaxation time that is expected to produce at least 3 orders of magnitude lower avalanche threshold compared to Mn$_{12}$-ac. We confirm this experimentally through the detection of gamma particles with energy at least two orders of magnitude lower than the original Mn$_{12}$-ac detection demonstrated using alpha particles, limited by the experimentally available radiation source. The true threshold of avalanche may be significantly lower and will be explored with lower energy x-rays and potentially infrared
photons.
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All authors Bailey Kohn, Rupak Mahapatra, Ivan Borzenets, Lok Raj Pant, Amis Sharma, Tom Melia, Michael Nippe, Anna Schmautz, Surjeet Rajendran
Computational Physics
Mixture of Polyconvex Neural Potentials for Parametric Hyperelasticity: Towards Foundation Material Models
Steven J. Yang, Govinda Anantha Padmanabha, D. Thomas Seidl et al. (+1 more)
Hyperelastic constitutive models enable modeling large deformations in elastic solids. In common practice, a strain energy density function is prescribed in advance and model-specific parameters are calibrated from experiments. However, many applications require constitutive models for a family of related materials whose mechanical behavior varies with composition. A fixed constitutive model-form may not capture the full range of behavior across the family, while fitting separate forms does not provide a direct way to predict the response of new compositions. Recent work has developed data-driven constitutive models that learn flexible strain energy functions while incorporating key physical constraints. In this work, we propose using mixtures of convex neural potentials based on input convex neural networks as a modular and data efficient approach to modeling material families. Each potential is convex and monotonic with respect to polyconvex strain invariants, while a conditioning network maps material descriptors to mixture weights. We compare the approach with a monolithic partially input-convex neural network using experimental data from PolyJet 3D-printed materials and a synthetic Gent-type
benchmark. Across both
benchmarks, the mixture architecture generalized better to material descriptors not seen during training. In the PolyJet experimental
benchmark, we showed that the mixture architecture is less sensitive to model hyperparameters, while in the Gent-type
benchmark it generalized more reliably with sparse data in the material-descriptor space. These results suggest that representing a material family through a small set of shared convex neural potentials provides a useful structural prior for learning descriptor-dependent constitutive behavior from limited data.
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All authors Steven J. Yang, Govinda Anantha Padmanabha, D. Thomas Seidl, Nikolaos Bouklas
Instrumentation and Methods for Astrophysics
The Canadian Galactic Emission Mapper (CGEM): A Cosmic Microwave Foreground Experiment
Parham Zarei, Pedro Villalba-González, Mandana Amiri et al. (+12 more)
The Canadian
Galactic Emission Mapper (CGEM) is a 4-meter single-dish
radio telescope located at the Dominion
Radio Astrophysical Observatory (DRAO) in Penticton, Canada. CGEM is designed to map polarized
Galactic synchrotron emission across the entire northern sky at 8-10 GHz with 1 MHz frequency resolution and 0.5 degree angular resolution. Its goal is to obtain high-fidelity, low-noise maps of polarized
Galactic synchrotron radiation, at frequencies where synchrotron dominates, in order to provide a reliable template for CMB B-mode foreground cleaning. We will show on sky performance of CGEM's single-pixel azimuthally-symmetric
telescope, its coherent, dual-polarized radiometer, and show maps made from commissioning data from the first few months of operation.
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All authors Parham Zarei, Pedro Villalba-González, Mandana Amiri, Charles L. Bennett, Guinevere Berg, Mark Halpern, Gary Hinshaw, Gordon Lacy, Joshua MacEachern, Thomas J. Rennie, Shuyu van Kerkwijk, Bruce Veidt, Janet Weiland, Don Wiebe, Edward J. Wollack
High Energy Physics (Theory)
Topologically induced deformations of differential forms
J. M. Hoff da Silva, J. M. B. Matzenbacher and R. da Rocha
Motivated by deformations of
spin structures and their
geometric implications, we study a deformed exterior derivative, which is a third-order nilpotent operator. This higher-order differential structure induces an anholonomic rescaling of the local frame and leads to a bifurcation of the associated cohomological structure, with two distinct notions of closedness and exactness. We prove that the Poincaré Lemma fails in both sectors, so that closed deformed forms need not be exact even locally. We then apply the resulting framework to a four-dimensional effective field theory and show that a constant saturation of the deformation parameter can generate a hierarchy between the electroweak and fundamental Planck scales through a purely
geometric mechanism, without introducing extra spatial dimensions.
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Nuclear Theory
Symmetry-Reduced Variational Quantum Simulation of the $U(5)\rightarrow SU(3)$ Quantum Phase Transition in the Interacting Boson Model
Faisal Etminan
The spherical-to-deformed
quantum phase transition of the Interacting
Boson Model (IBM) is investigated using the variational
quantum eigensolver (VQE). The $U(5)$–$SU(3)$ transitional
Hamiltonian is studied with $\chi=-\sqrt{7}/2$. We develop a
symmetry-preserving, minimum-
qubit VQE framework for collective
nuclear models, achieving a substantial reduction in
qubit requirements without compromising the finite-size
quantum-phase-transition physics. The transition is characterized through the normalized $d$-
boson occupation and ground-state energy derivatives. Finite-size results are found to approach the analytic critical point $\xi_c=8/17\simeq0.470588$, with an independent order-parameter extrapolation yielding $\xi_\infty=0.46986(61)$. The VQE reproduces ground-state energies and structural observables to numerical precision. These results demonstrate the potential of
symmetry-reduced VQE for efficient
quantum simulations of collective
nuclear dynamics and
quantum phase transitions.
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Quantum Physics
Spatial correlations of photons interacting via transverse Rydberg blockade
Bankim Chandra Das, Daniil Svirskiy, Matthias Metternich et al. (+3 more)
We develop a theory of the transverse spatial dynamics of two interacting
photons in a Rydberg nonlinear medium. Extending the well-studied one-dimensional case, we explore both longitudinal and transverse correlations of
photons propagating as Rydberg polaritons. We identify distinct behaviors and scaling laws for these correlations, arising from fundamentally different mechanisms in the two directions: diffraction for transverse correlations and
diffusion for longitudinal correlations. We develop a model incorporating a Gaussian optical beam and an inhomogeneous atomic density distribution, from which we derive quantitative predictions for correlation functions in both directions. We further show that the propagation equations can be reduced to a single Schrödinger-like equation, allowing approximate solutions that are supported by full numerical results. Our findings indicate that the transverse correlation length is determined primarily by the blockade radius, whereas the longitudinal correlation length is limited by bandwidth. These results establish transverse Rydberg blockade as a distinct and measurable correlation mechanism and show that spatial
photon correlations provide a direct means of measuring the blockade radius.
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All authors Bankim Chandra Das, Daniil Svirskiy, Matthias Metternich, Wolfgang Alt, Sebastian Hofferberth, Ofer Firstenberg
High Energy Physics (Theory) · Cross-listed from math.QA
Algebra objects in direct limit completions of compact Lie group duals and the classification of $c=1$ vertex operator algebras
Sebastiano Carpi, Tiziano Gaudio and Luca Giorgetti
Let $G$ be a complex reductive affine algebraic group with its symmetric tensor category $\mathcal{C}_G$ of finite-dimensional rational representations. We prove that every simple commutative
algebra object with at most countable dimension in the direct limit completion $\operatorname{Ind}(\mathcal{C}_G)$ of $\mathcal{C}_G$ is isomorphic to the
algebra $\mathcal{O}(G/H)$ of regular functions on the homogeneous space $G/H$, for some reductive algebraic subgroup $H$ of $G$. Then we apply this result to the theory of vertex operator
algebra extensions. In particular, assuming the strong rationality of the $ \operatorname{A}_5$-orbifold of the vertex operator
algebra $V_{\mathcal{L}_2}$ associated with the rank-one root
lattice $\mathcal{L}_2:= \sqrt{2}\mathbb{Z}$, we classify all the not necessarily rational simple CFT type preunitary vertex operator
algebra extensions of the simple
unitary Virasoro vertex operator
algebra $L(1,0)$ with central charge $c=1$ satisfying a certain spectrum condition. This result is the vertex operator
algebra analogue of a conformal net result by Feng Xu. Every strongly rational preunitary vertex operator
algebra extension of $L(1,0)$ satisfies the above spectrum condition because of the congruence subgroup modularity property of its characters. As a consequence, we get a complete classification result for strongly rational $c=1$ vertex operator
algebras, up to the strong rationality of $V_{\mathcal{L}_2}^{\operatorname{A}_5}$.
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Quantum Physics
Generation of multicomponent Schrödinger cat states in schemes with measurement of Gaussian states
E. A. Nesterova and S. B. Korolev
In this work, we propose a scheme for generating superpositions of Fock states whose numbers differ by four or eight. The proposed protocol is based on
photon-number-resolving measurements on multimode Gaussian states. We compare of the generated states with multicomponent Schrödinger cat states. We evaluate the fidelity and determine how it scales with the number of detected particles. Furthermore, we derive the optimal configuration for the generation such states.
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