Papers

The Multi-Purpose Detector (MPD) experiment at NICA is designed to investigate strongly interacting matter at high net-baryon density through a broad program of heavy-ion measurements. Dielectrons constitute one of the key probes in this program, with contributions emitted throughout the entire space-time evolution of the collision. Their experimental measurement is, however, challenged by a large combinatorial background arising primarily from incompletely reconstructed photon conversions and Dalitz decays of light neutral mesons. In this work, we study the performance and capabilities of the MPD experiment for dielectron measurements using simulated minimum-bias $^{209}$Bi+$^{209}$Bi collisions at $\sqrt{s_{NN}}$ = 9.2 GeV. Electron identification is performed using the combined information from the TPC, the TOF detector and the ECal. A multilayer-perceptron classifier is used to optimize electron identification, leading to a substantial increase in electron detection efficiency relative to sequential one-dimensional selections while preserving an electron-sample purity close to unity over a broad momentum range. To address the dominant sources of combinatorial background, a pair-analysis strategy is developed that exploits partially reconstructed electron tracks. The method combines the pair opening angle, the TPC dE/dx signal, and an approximate reconstruction of the pair invariant mass to tag tracks from photon conversions and $\pi^0$ Dalitz decays at the pair level. In the mass interval 0.2 $< m_{ee}<0.7 $ GeV/$c^2$, the method improves the signal-to-background ratio by a factor of about 3.5 with the current track reconstruction algorithm. The study demonstrates the strong potential of the MPD experiment for dielectron measurements at NICA energies and highlights the importance of further improvements in low-$p_{\rm T}$ track reconstruction.

Mechanical metamaterials are materials that, by virtue of their microstructural architectures, exhibit mechanical properties not often found in nature: for example, auxetic mechanical metamaterials are materials that possess a negative Poisson's ratio in response to deforming forces. However, outside of relatively simple crystalline, lattice-based, or repeating-pattern architectures composed of mostly identical unit cells, mechanical metamaterials like auxetics are notoriously difficult to design, particularly across all three dimensions. Here we show that, for any structure that can be decomposed into triangular or tetrahedral meshes, those structures can be subjected to a simple transformation that that creates conditions within those triangular or tetrahedral simplexes that, regardless of their individual geometries, introduces a counter-rotating polygon/polyhedron mechanism that both guarantees a negative Poisson ratio and allows locally programmable mechanical properties. We apply this "shrink-and-wrap" construction to generate mechanical metamaterials from increasingly complex 3D structures, first from simple (convex) polyhedrons; then, to designs with arbitrarily large numbers of vertices and designed using constructive solid geometry (CSG) and 3D scanning; and, ultimately to 3D objects generated from videos captured by mobile phone camera – making potentially any object or geometric structure designed or found in the real world transformable into a mechanical metamaterial. We show that these monolithic auxetic constructions remain readily 3D-printable via additive manufacturing techniques. We expect this piecewise approach to designing arbitrarily complex mechanical metamaterial structures can enable numerous potential applications where programmable internal reconfigurations and/or force redirection are required across and throughout their 3D geometries.

AI agents are advancing the automation of molecular dynamics (MD) research, with the potential to accelerate discovery and design of lithium-battery electrolytes. However, whether they can autonomously complete scientifically reliable electrolyte MD studies remains insufficiently evaluated. We introduce ElectrolyteMD-Bench, which unifies dilute, high-concentration, and localized high-concentration electrolytes in a comparative study across distinct solvation regimes. The benchmark connects local coordination, ionic association, single-particle dynamics, and collective transport within one continuous research process. Agents autonomously perform system construction, equilibration, production sampling, property analysis, and interpretation under a frozen scientific model, while deciding whether to correct errors, continue sampling, or stop. We audit each study along four dimensions: simulation validity, analysis validity, evidence integrity, and outcome calibration. Across eight model–harness configurations, all 24 system runs produced valid production trajectories, yet none of the eight studies satisfied all scientific requirements. Failures included missing analyses, incorrect physical definitions or numerical implementations, insufficient statistical support, and completion claims inconsistent with retained evidence. These results expose a gap between successful MD workflow execution and reliable scientific study completion. ElectrolyteMD-Bench therefore provides a foundational test and defines a key capability threshold that autonomous electrolyte simulation must cross to advance toward computation-first materials exploration.

Methane pyrolysis experiments were performed in a micro flow reactor to investigate the chemical mechanism sensitivities at elevated pressures and temperatures. The micro flow reactor used in this study provides independent control over reaction parameters. Experiments were performed at temperatures from 1400 to 1800 K and pressures from 1 to 10 bar at a fixed residence time of 60 ms. The yields of hydrogen, unreacted methane, and solid carbon were quantified for comparison to predictive models. The mass of heterogeneous depositions was also quantified. The presence of C2 and PAH species were measured by GC-MS. The results were compared to 1D simulations using a discrete sectional model for capturing the kinetics of particulate formation and surface deposition. The simulations replicated the pressure trend well at high temperatures (1800 K), but the sensitivity to temperature was in disagreement. Simulations generally found lower carbon and hydrogen yields and a stronger sensitivity to temperature than the experiment. An abundance of PAH intermediates was measured at lower temperatures and higher pressures. The simulated surface deposition rates were lower than the measured values but showed similar profiles. The results demonstrate the utility of micro flow reactors in recreating pyrolysis environments for hydrogen production from methane. The predictive capabilities of simulations could be improved by advancing the fuel decomposition and PAH formation and consumption kinetics at low temperatures and by detailed treatment of surface site density.

Societies worldwide are described as increasingly polarized, yet issue polarization – how divided a society is over political positions – has been measured almost entirely on a single left-right axis developed in Western democracies. Whether that axis describes political division elsewhere is largely untested, because no survey measures political attitudes on multiple dimensions across many countries. Here, we harmonize 1,299 items from nine cross-national survey programs and 23 national election studies to place 1.14 million people from 141 countries on four dimensions: social liberalism, economic left-right, democratic commitment, and anti-elite sentiment. A single left-right axis does not describe political division in most of the world. The median within-country correlation between a person's social and economic positions is -0.015. Societies differ instead in what they are divided about, and they do so by region. European countries divide most often over social liberalism, East Asian and Arab countries over democratic commitment, Latin American countries over economic left-right, and African countries over anti-elite sentiment. Of the 81 countries measured on all four dimensions, 39 are most divided on a dimension no left-right scale would capture. Most political disagreement lies within countries rather than between them, at 58 to 88 percent of the variance. Ideological constraint, long treated as a property of mass publics, holds in nineteen of the eighty-three we can test, most strongly in the United States at +0.70, and there it is concentrated among the politically attentive. Understanding political conflict therefore requires asking not how polarized a society is but what it is polarized about. Our released item bank and fitted parameters place respondents from any future survey on the same scale without re-estimation, once that survey's items are harmonized to the bank.

Accretion disk surrounding around compact astrophysical objects serve as a powerful laboratories for testing gravitational theories in the strong-field regimes. In this work, we systematically investigated the structural, dynamical, and thermodynamic properties of the steady-state thin accretion disk within the framework of $f(R,T)$ gravity by adopting the linear functional form $f(R,T) = R + 2\chi T$ coupled with the pressure-free dust fluid matter Lagrangian ($\mathcal{L}_m = -\rho$). We demonstrate that the modified field equations seamlessly reduce to standard General Relativity in the pure vacuum limit ($T_{\mu\nu} = 0$). Utilizing a perturbative approach for a small coupling parameter ($\vert{}\chi\vert{} \ll 1$), we derive the first-order corrections to the background Schwarzschild metric potentials, which subsequently govern the modified particle kinematics, the specific energy $E$, the specific angular momentum $L$, and the Keplerian angular velocity $\Omega$. Our analysis reveals that the geometry-matter coupling parameter $\chi$ significantly shifted towards the location of the Innermost Stable Circular Orbit ($r_{isco}$) and alters the radial energy dissipation rate $F(r)$ and the effective surface temperature profile $T(r)$ across the Shakura-Sunyaev thin disk. Furthermore, the resulting modifications in the Spectral Energy Distribution (SED) and overall radiative efficiency $\eta$ provide robust theoretical signature.

Gravitational waves (GWs) can induce effective electromagnetic currents when interacting with external electric and magnetic fields, as described by linearized gravity modifications to Maxwell's equations. This coupling enables a novel detection approach for high-frequency gravitational waves (HFGWs) using axion haloscope experiments. Here we present the MAGnetic Gravitational wave Induction Experiment (MAGGIE), the first lumped-element HFGW detector proposed in Europe, designed to probe HFGWs in the kHz-MHz regime by leveraging a 14 T solenoidal magnet at the University of Hamburg. The GW-induced magnetic flux is captured by a custom-designed pickup loop optimized for the expected symmetry of the effective current. A figure-8-shaped geometry, oriented to break the azimuthal symmetry, is implemented, together with a blind-loop configuration, for real-time noise rejection and calibration. The readout scheme is tailored for continuous signals and time-domain transient searches, using waveform templates for primordial black hole (PBH) mergers. The expected experimental reach in terms of strain spectral noise density at the 40 MHz high-frequency end is projected to reach $\sim 4 \times 10^{-16}/\sqrt{\mathrm{Hz}}$ for transient searches, and in terms of strain, projected to reach $\sim 10^{-19}$ for 1 year of continuous search. This allows MAGGIE to constrain currently unexplored regions of the HFGW parameter space.

Precision cosmology is a cornerstone of modern astronomy, and upcoming wide-field photometric surveys make it crucial to develop robust, data-driven inference methods that can handle complex survey systematics without relying on closed-form likelihoods. Simulation-Based Inference (SBI) meets this need by enabling forward simulations that encode complex survey characteristics. Previous SBI analyses in supernova cosmology have used SALT2 light-curve parameters as summary statistics; however, SALT2's two-basis spectral template imposes rigid modeling assumptions, motivating a more flexible representation. In this work, we present the first application of Functional Principal Component Analysis (FPCA) light-curve parameters as summary statistics for SBI-based cosmological inference under a non-flat {\Lambda}CDM model. On identically generated simulations, FPCA+SBI yields constraints comparable to both SALT2-based SBI and explicit-likelihood analyses, while providing more robust constraints on out-of-domain simulations than SALT2. Applying the model trained on LSST-like light curves to a spectroscopically confirmed DES Year 5 supernova sample, we recover constraints consistent with those of the DES collaboration to within 0.12 {\sigma} and 0.23 {\sigma} in {\Omega}m and {\Omega}{\Lambda} respectively, establishing the method's generalizability to real survey data. By introducing host-dependent systematics through a mass-dependent dust extinction law, we find FPCA-based summary statistics implicitly encode host-dependent systematics, suggesting dedicated host modeling may be unnecessary within this framework. Combined with its previously demonstrated effectiveness for photometric classification, FPCA offers a compelling foundation for unified, data-driven pipelines capable of jointly performing supernova classification and cosmological inference for upcoming wide-field photometric surveys.

Exceptional points (EPs) are spectral singularities, but whether they can be used to control a distinct criticality of coherent interference remains largely unexplored. Here we show in nonlocal superconducting transport how spectral and interference criticalities can be controllably synchronized. In a minimal superconducting double-quantum-dot system, loss imbalance selectively drives one Bogoliubov sector through an EP. The spectral EP and the CAR-ECT interference criticality form distinct structures in control space whose relative ordering can be continuously tuned. At their synchronization point, the interference boundaries between crossed Andreev reflection (CAR) and elastic cotunneling (ECT) coalesce at the EP and bifurcate beyond it, creating a finite CAR-dominated window. The resulting interference window opens with a square-root critical law, whose exponent also governs the finite-temperature observability scale. Detuning unfolds the two criticalities, while retuning restores their intersection, establishing the synchronization as controlled rather than generic. The bifurcation is directly observable in nonlocal conductance. Our results establish exceptional points as spectral control points for independently defined interference criticalities, opening a route to non-Hermitian control of critical quantum interference.

Self-similar dynamics are often described in terms of a single asymptotic scaling regime. Here we experimentally investigate the post-breakup recovery of a hydrodynamic interface over substantially wider temporal and spatial ranges than previously accessible. Beyond the previously identified scaling behavior, we find four successive self-similar regimes characterized by the $R_{\beta}$-scaling with $\beta=1/6$, 1/2, 1, and 2, connected by three distinct crossovers. All four regimes exhibit robust collapse near the interface tip, while geometrical dependence becomes detectable farther from the singular region. This systematic variation across space and scaling regimes is consistent with scale separation and enhanced universality closer to the breakup singularity. The characteristic scales associated with the different $R_{\beta}$-scalings become comparable at the common geometric scale $z_m \simeq R$. These findings demonstrate that self-similar dynamics can undergo multiple successive crossovers among distinct scaling regimes rather than directly approaching a single asymptotic self-similar state.

The Hildas are objects trapped in 3:2 mean-motion resonance (MMR) with Jupiter, and are a fascinating window into the Solar system's formation and evolution. We present the results of detailed dynamical integrations of 2,699 numbered asteroids in the Hilda region, following 243 clones of each Hilda for 1 Gyr under the influence of the giant planets and the Sun; 54.7% of our sample exhibit extreme dynamical stability, with all clones of 1,475 Hildas remaining trapped in the 3:2 MMR for the full 1 Gyr of our integrations. A further 408 Hildas (15.1% of the sample) see more than 50% of their clones surviving within the MMR at the end of the simulations. Of the remaining 30.2% of the population, 327 objects (12.1%) lose 50% of their clones at some point between the 100 Myr and 1 Gyr point, leading to dynamical half-lives measured in hundreds of millions of years – a result compatible with those objects being members of a once larger population of Hildas trapped since the Solar system's youth. The final 489 objects (18.12%) prove highly unstable – and may well be interlopers, captured to the Hilda population in the relatively recent past. Overall, our results suggest that the Hilda population was larger in the past, while its remarkably high stability over Gyr timescales is consistent with a primordial origin.

We study how discrete parameters which enumerate non-crossing permutations become geometric quantities in JT gravity. Analyzing non-crossing permutations on the disk together with two classes of annular non-crossing permutations, we find that under suitable continuum scaling limits the number of marked boundary points becomes the thermal boundary length, while the number of through-connections becomes a geodesic length. In this limit, the enumerations reproduce the universal low-temperature behavior of the Schwarzian theory on the disk and the orientable and orientation-reversing double-trumpet geometries. We then relate these constructions to higher-boundary non-crossing diagrams, whose continuum enumeration reproduces the JT result obtained by attaching trumpets to the top-degree part of genus-zero Weil-Petersson volumes, suggesting that the same trumpet–enumeration parameter mapping extends beyond the planar case. Together, these results establish a direct connection between non-crossing permutation enumerations and Weil-Petersson volumes with trumpets attached, a construction that plays a central role in the gravitational path integral in JT gravity, and suggest that non-crossing diagrams provide a combinatorial route to computing multi-boundary partition functions.

Sagittarius A* (Sgr A*) exhibits intermittent flaring behavior, characterized by strong enhancements in high-energy emission (infrared and X-ray). These events have been interpreted as related to the coherent orbital motion of localized regions of energized plasma - hotspots. While this framework has been quite fruitful in constraining properties of Sgr A*, it is subject to important challenges and limitations. In this brief review we discuss the recent observational and theoretical developments related to this line of research, commenting on the concerns regarding the hotspot model validity and the future perspectives.

We propose a ”stepping stone” realization of the varying Peccei Quinn (PQ) scale solution to the QCD axion isocurvature problem. In conventional implementations, suppressing isocurvature during high scale inflation requires a large inflationary PQ scale, while the subsequent evolution toward the much smaller late time vacuum can induce parametric resonance and nonthermal restoration of the PQ symmetry. We ameliorate this tension by introducing an intermediate PQ-breaking vacuum that is reached before the end of inflation, so that the later evolution to the present day PQ scale spans only a moderate hierarchy. The vacuum structure arises radiatively: a Yukawa coupling between the PQ scalar and PQ-charged fermions drives the quartic coupling negative at high scales while keeping it positive at lower scales. A positive dimension six operator then stabilizes a large field minimum, while the positive low energy quartic together with the quadratic terms generates the intermediate vacuum. We study two mechanisms in which the rolling inflaton removes the large field minimum, either by scanning a hidden non-Abelian gauge coupling or by directly scanning the Yukawa coupling. In both cases the PQ field is released toward the intermediate vacuum during inflation, after CMB modes have exited the horizon. We exhibit benchmark regions with subdominant backreaction on the inflationary sector and suppressed vacuum tunneling, and show that the construction permits substantially less hierarchical quartic and higher-dimensional couplings than conventional realizations that depend on a varying PQ scale. The underlying logic may have analogues for extra-dimensional or string axions, where the effective axion decay constant is controlled by geometric moduli, although realizing the required intermediate vacuum in a controlled modulus potential is nontrivial.

Two-dimensional superconductors test our understanding of quantum phases. Low-temperature "anomalous metal" states are widely observed where conventional theories predict only superconducting or insulating ground states. In model systems based on proximity-coupled Josephson junction arrays, the critical temperature falls far faster with decreasing normal-state conductance than predicted by existing models. Whether these observations indicate a new quantum phase, a need to refine models of disorder and fluctuations, or both remains unresolved. Using scanning magnetic susceptometry, we image the local superfluid phase stiffness $\rho_s$ in gate-tunable Josephson junction arrays consisting of epitaxial Al islands on an InAs quantum well. Across six arrays and more than two orders of magnitude in the zero-temperature phase stiffness $\rho_{s0}$, the diamagnetic critical temperature $T_{c,\varphi}$ is suppressed more strongly than can be explained solely by thermal phase fluctuations, scaling approximately as $T_{c,\varphi}\propto\rho_{s0}^{0.3}$. While $\rho_s$ is remarkably uniform at high carrier densities, at low carrier densities we find that anomalous metal transport emerges together with large-scale inhomogeneity that transport alone cannot directly detect. These results are inconsistent with a classical XY description within standard junction models, instead pointing to quantum fluctuations that suppress superconductivity throughout the superconducting phase and amplify inhomogeneity near the superconductor-insulator transition, producing anomalous metal behavior.

These notes are aimed at providing a relatively concise and self-contained introduction to anomalies in quantum field theory. A first part reviews the necessary notions of quantum field theory, in particular its functional integral formulation which we use throughout. Then we discuss in some detail how and why anomalies arise as non-invariance of the functional integral measure or through the absence of a regulator preserving all symmetries, and how they manifest themselves as current non-conservation in anomalous loop diagrams and anomalous Ward identities, or equivalently as a non-invariance of the effective action. Specifically, we deal with the so-called abelian anomaly under chiral transformations, and the so-called chiral anomaly which is a violation of non-abelian gauge invariance in the presence of chiral fermions. We perform a detailed triangle Feynman diagram computation for both cases. Then we move on to provide a brief overview of some important properties of anomalies (locality, finiteness, one-loop exactness), and how they are characterized in general by the Wess-Zumino consistency condition. We show how this condition can be reformulated in terms of BRST cohomology and how it can be solved, for arbitrary (even) space-time dimensions, by the descent equations. Finally, we briefly discuss the general relation between anomalies in arbitrary even dimensions 2n and index theorems in 2n+2 dimensions, generalizing also to gravitational anomalies. We conclude with the exhibition of the highly non-trivial anomaly cancellation in ten-dimensional IIB supergravity.

Fluctuation–response relations (FRRs) provide a fundamental relation between spontaneous fluctuations and the linear response to external perturbations, yet their validity in non-equilibrium systems remains an open problem. In a general class of noisy, finite-size, mean-field models of coupled phase oscillators, we reveal two types of FRRs in the incoherent phase below the synchronization transition. The first, corresponding to the infinite-size limit (I-FRR), involves the convolution between the external force and the correlation function in the time domain. The second, the finite-size counterpart (F-FRR), is governed by finite-size fluctuations and carries a correction factor: a spectrum function whose roots correspond to eigenvalues, or Landau poles, of the linear operator. The finite-size fluctuations are suppressed in the weak-coupling or strong-noise limits, and F-FRR reduces to I-FRR. Our analytical findings are verified by extensive numerical simulations.

We present molecular dynamics simulation results for an ultracold $^{40}$Ca plasma in a constant, homogeneous magnetic field. The magnetic field induces a significant spatial separation of charges. Furthermore, a significant fraction of the electrons escapes from the region bounded by the ions, in contrast to the case of plasma expansion into a vacuum. This leads to the formation of a quasineutral plasma core containing the remaining electrons and surrounded by an outer, thick ion shell, where the ion density drops sharply. Anisotropy in the ion kinetic energy is also observed, depending on the direction of ion motion relative to the magnetic field lines. The simulation results are in agreement with experimental data on ion dynamics.

Parity violation in the early Universe may lead to a chiral gravitational wave background. We show that, for finite-time parity-violating sources, the low-frequency tail of the generated chiral gravitational wave background is universally unpolarized, and that the chirality fraction decreases linearly with frequency. Our result generally applies to any parity-violating gravitational-wave source that appears quadratically in the wave equation. We consider both Gaussian sources and explicit trispectrum templates. We attribute the lack of chirality of the low-frequency tail to the fact that, on large scales, gravitational wave generation is almost equally inefficient for both helicities.

Quantum computing offers a new, orthogonal direction for investigating fundamental physics, extending beyond classical numerical methods and conventional observables. Realizing this potential requires directly confronting the noise limiting currently available quantum computers. Progress rests on advancing algorithms, interpreting their results, and managing their errors together. This thesis presents several advancements in the use of quantum simulation and quantum information to probe fundamental physics. The first is in the use of quantum computers to simulate collisions in quantum field theories. Central to these simulations are new wavepacket preparation, time evolution, and error mitigation techniques, which allow for simulations with some of the largest effective circuit volumes to date. These methods enable the first quantum simulation providing numerical evidence for inelastic particle production, a key process in fundamental physics. The second advancement centers on the role quantum-information-theoretic quantities play in physical processes. Beyond mere correlations with the physics of the process, entanglement and magic are shown to probe the interactions present in scattering and hadronization dynamics. A precision study requires a complete quantification of algorithmic and hardware uncertainties, an outstanding goal as quantum simulations mature. The third advancement in this thesis addresses error management. A framework minimizing the effect of algorithmic errors in analog quantum simulations is presented. In a step toward fault tolerance, error detection in encoded quantum simulations is shown to improve estimation of local observables relative to unencoded runs. Together, the developments in this thesis mark practical progress toward fault-tolerant quantum simulations of fundamental physics capable of scientific discovery.

We present a new tool for generating simulated point spread functions (PSFs) in the Wide Field Instrument (WFI) of the Nancy Grace Roman Space Telescope. The simulation tool is physics forward, and performs a raytrace of the optical system of the instrument to compute the PSF, while also accounting for various detector effects. The tool also has the capability to add perturbations to the optical system and detectors. We explore several applications of the tool that may arise during the commissioning of the telescope, including optical ghosts, measuring the optical aberrations from diffraction spikes, and studying the effect of mirror polarization.

We show that the inert doublet dark matter can reconcile the purported LZ direct detection signal and IceCube constraints. The preferred dark matter mass is 11.3–20.3~TeV, an order of magnitude heavier than the standard higgsino target. The smaller number density at a high mass can reproduce the LZ event given the exponential sensitivity to the velocity, while suppressing the capture rate in the Sun because of the higher infall velocity. On the other hand, the high mass requires a large coupling between the inert doublet and Higgs boson to have the correct annihilation cross section for the freeze-out. There is about an order of magnitude of validity range below the Landau pole, beyond which a UV completion is needed. Electroweak precision observables are below the experimental limits despite the large coupling.

Quantum generative models are often motivated by circuit families whose output distributions are believed to be classically hard to sample from. When such models are trained on ordinary classical datasets, however, this hardness does not automatically transfer to the unknown data-generating distribution. We show that transferring sampling hardness via total-variation closeness from a quantum model to an unknown source requires certifying a global relation between the two distributions, thereby reducing the problem to distribution certification. Combining this reduction with existing certification lower bounds yields an exponential sample requirement for the high-entropy distributions relevant to many sampling-hardness proposals. Consequently, polynomially many samples cannot, in general, justify attributing sampling hardness to an unknown data-generating distribution. Moreover, even classically trivial distributions, such as the uniform distribution and product distributions, require exponentially many samples to certify in the absence of structural assumptions. Our results clarify the role of sampling hardness in quantum generative modeling and distinguish generator-level hardness from source-level hardness when learning from ordinary datasets.

Due to strong spin-orbit coupling, large Landé $g$-factor, and a highly transparent interface, the two-dimensional electron gas (2DEG) in InAs quantum wells provides an ideal platform for the exploration of topological superconductivity in hybrid semiconductor-superconductor heterostructures. Reduction of disorder in the semiconductor remains a primary challenge to the disambiguation of subtle interaction effects. Here we demonstrate very high mobility InAs 2DEGs grown on insulating InP substrates. Utilizing a convex compositional grading profile in an InAlAs metamorphic buffer we demonstrate InAs quantum wells with thickness greater than 10 nm without need of Ga-containing cladding layers. We examine structural and electrical transport properties of these heterostructures. Advances in the design of the metamorphic InAlAs buffer result in low-temperature electron mobility exceeding $1.7\times10^6$ cm$^2$ V$^{-1}$ s$^{-1}$ at 2DEG density $\leq3.2\times10^{11}$ cm$^{-2}$, the highest value yet reported for this material system.

Origami structures typically have a multiplicity of folded states that are connected to a flat sheet, making the folding protocol for specific end shapes challenging to design and deploy. Here, we introduce reprogrammable origami hinges that use bistable buckled shims to reversibly control their preferred folding direction. A shim embedded across a hinge produces an asymmetric torque-angle response that favors either mountain or valley folding. Switching the shim between its two stable states reverses this response, allowing the folding direction of each hinge to be reprogrammed after fabrication. By independently controlling the states and geometries of the shims, we enable a single origami sheet to access multiple folding branches and transform into prescribed three-dimensional shapes. We further introduce self-switching hinges in which folding causes the shims to snap between their stable states. These elements allow the sheet to reprogram its folding pathway under global mechanical inputs applied to the boundaries. Our approach embeds both shape selection and transition rules directly within the mechanics of the hinges, providing a versatile framework for creating multifunctional, deployable, and reconfigurable structures.

Particle accelerators have carried fundamental physics to remarkable precision, but the Planck scale remains fifteen orders of magnitude beyond any foreseeable collider. We argue that this impasse is not a temporary shortfall but an insurmountable one. The way out runs through condensed matter physics: laboratory tests of generalized uncertainty relations, analog systems, and — most provocatively — frameworks in which spacetime itself is a condensate. We review the string-loop picture, in which quantization turns the world sheet into a three-dimensional fractal, the corpuscular description of black holes as self-sustained graviton condensates, and the phase-transition structure connecting the Riemannian phase to a pre-geometric one. The conclusion is deliberately provocative: the question of quantum gravity is no longer a question of energy, but of crossing the bridge.

Artificially generated muon beams, with tunable parameters, are highly valuable in imaging objects that are opaque to any other scanning technique. Lower-energy muon beams are currently produced at accelerator facilities, while higher energies have only recently been observed as a result of the interaction of laser-wakefield-accelerated electrons and solid targets. This work focuses on using muography imaging detectors to measure the profile of a muon beam generated via the Bethe-Heitler process and to perform muon imaging in an experimental setup extending up to 42 meters from the muon source. By comparing the data with Monte Carlo simulations, we confirm that the measured beam profile and object imaging are consistent with artificially produced muons of energy of a few GeV. To our knowledge, this represents the first demonstration of imaging dominated by an artificial, laser-driven muon beam.

We develop an explicit plane-wave (PW) $\times$ photon-Fock approach to the quantized, velocity-gauge Pauli–Fierz Hamiltonian for periodic, first-principles calculations: because the quantized vector potential is spatially uniform, the light–matter coupling reduces to an operator-valued shift of the crystal momentum, $K\to K+\hat{\mathbf A}/c$, and the existing plane-wave machinery of ordinary solid-state DFT is reused essentially unchanged. This PW$\times$Fock construction puts first-principles cavity QED of periodic solids on the same footing as the Fock-space coupled-cluster and configuration-interaction methods already developed for molecules, opening hitherto inaccessible systems—materials in a linear or chiral cavity, in particular—to first-principles plane-wave calculations. We illustrate the method with monolayer graphene in linear and chiral cavities, obtaining a polarization-selective Haldane gap together with the corresponding density-of-states, real-space, and circular-dichroism optical signatures. A full Brillouin-zone Berry-curvature calculation confirms the topological character of the chiral-cavity gap directly: the occupied manifold carries a quantized Chern number that steps through a non-monotonic sequence, $C=1\to3\to{-1}\to1\to2\to{-1}\to1$, with two narrow, sign-reversed windows—a property of extended, vacuum-dressed matter with no counterpart in a finite molecular system.

In scientific machine learning, $\Delta$-learning trains models on residual errors relative to physical baselines, assuming that more accurate baselines with smaller residual scales inherently improve downstream performance. Here, we demonstrate that residual scale alone is an insufficient heuristic for learnability. Evaluating molecular graph neural networks on total energy targets, we show that complex local descriptor baselines can yield small residual targets that are disproportionately rough within architecture-informed proxy spaces and harder to learn relative to their scale. Conversely, semi-empirical baseline reduces both scale and normalized roughness, improving in-domain and out-of-domain prediction. We introduce scale-normalized graph Dirichlet roughness ($D_{\text{IQR}}$) as a pre-training diagnostic for residual learnability and establish baseline complementarity as a core target-design principle, elevating target space formulation alongside model architecture as a key axis for scientific machine learning.

In genuinely rotating holographic backgrounds, Wilson-loop observables are usually constructed for a quark–antiquark pair static with respect to the rotating plasma. We investigate how this choice affects the heavy-quark sector by comparing two descriptions of the same rotating geometry: a corotating frame, in which the pair is static with respect to the plasma, and a static frame, in which it is static with respect to the static observer. We consider an equal-rotation Myers–Perry black hole in asymptotically global AdS and study Wilson loops oriented longitudinally and transversely to the rotation. We analyze the effective string tension, physical quark–antiquark separation, and heavy-quark potential at fixed thermodynamic temperature measured in the corresponding frame. We find a strong frame dependence of the rotational response. In the corotating frame, the longitudinal and transverse configurations respond qualitatively differently: rotation can either decrease or increase the separation and effective string tension, depending on orientation and, for the latter, on the bulk position and parameter range. The heavy-quark potential increases with angular velocity in both orientations. In the static frame, by contrast, the effective tension, physical separation, and maximal separation decrease with angular velocity in both orientations, while the heavy-quark potential increases. Thus, the anisotropic response is substantially stronger in the corotating frame, both qualitatively and quantitatively. In both frames, rotational modifications generally become less pronounced at higher temperature. These results show that the frame in which the quark pair is static is an essential part of the physical specification of Wilson-loop observables in rotating holographic systems.