High Energy Physics (Theory)
Carrollian Worldsheets on Carrollian Targets, When does ILST describe a null string theory?
M.M. Sheikh-Jabbari and H. Yavartanoo
Null string theory (NST) is a two-dimensional (2d) sigma-model on a Carrollian worldsheet with 2d diffeomorphisms, Weyl and Carroll-Weyl (CW) scalings as gauge
symmetries whereas the Isberg-Lindström-Sundborg-Theodoridis (ILST) theory on a generic target space only realizes the first two and not the CW gauge
symmetry. We show in this work that NST on the Carrollian target spaces (CTS) is well-defined if the background admits a homothetic kernel generator and that, it is described by the ILST theory on the same CTS. To this end, we formulate a minimal null string theory on CTS, starting from first principles and then discuss beyond minimal theories as deformations away from minimality. We study some classes of such deformations involving the clock one-from for ruled Carrollian spaces and/or connection on the Carrollian space. We discuss implications of this for the recently introduced null string holography. As examples CTS, we briefly discuss null strings probing black hole horizons and the null string holography in this context.
Read the full abstract ▾
Quantum Physics
Mode-tunable inter-core coupling of photon-number-resolved quantum light in a telecom multicore fiber
Chiran Wijesundara, Yasmin Sarhan, Henry Strong et al. (+3 more)
Multicore optical fibers (MCFs), developed to scale classical telecommunications, are gaining traction as a
quantum platform for high-dimensional key distribution,
entanglement, and photonic
quantum walks. So far,
quantum light has occupied these fibers only as single-mode path channels; the spatial-mode structure within each core has remained untouched. Here we operate a telecom-grade 39-core fiber far from its design wavelength, where each core supports exactly two LP mode groups (LP01, LP11), and measure heralded
photon-number states |1> and |2>, resolving the
photon number simultaneously with the intra-core spatial mode or with the core index. Displacing the launch prepares a coherent LP01-LP11 superposition whose single-sided intensity pattern shows that the intermodal phase is preserved over the fiber: a drift-resolved joint fit gives a pixel asymmetry (0.4% vs 47%) incompatible with an incoherent mode mixture. Because the two modes couple to neighboring cores at different rates (kappa_LP11/kappa_LP01 = 2.4), the launched mode content acts as a state-selectable coupling knob: the effective inter-core coupling of the passive fiber is set by the launch alone (3.9-13.1%), a tunability that otherwise requires electro-optic, thermo-optic, or mechanical reconfiguration. The propagation is
photon-number independent: the per-
photon crosstalk of heralded |2> states equals that of |1>, bounding any Fock-state dependence to |dx/x| < 6.1% (95% CL), and the imaged mode distributions of |1> and |2> agree to better than 1%. This measured linear-optics null, validated against exact Fock-space simulation, is the baseline against which genuine multiphoton interference in fiber
quantum walks must be certified; we also show how coincidence-based event selection produces spurious
photon-number-dependent crosstalk if accidentals are not subtracted.
Read the full abstract ▾
All authors Chiran Wijesundara, Yasmin Sarhan, Henry Strong, Jeffrey Cai, Dan T. Nguyen, Tim Thomay
Quantum Physics
Efficient Sampling for Many-Body Fermionic Non-Gaussianity
Ryota Matsuda, Masahiro Hoshino and Yuto Ashida
Fermionic non-Gaussianity is a key resource for universal
quantum computation, and its behavior in
quantum many-body systems has attracted growing interest. Recently, a convolution-based measure, which we call the magic Rényi
entropy (MRE), has been proposed as a resource measure of non-Gaussianity, but its evaluation is limited to small systems due to the computational cost growing exponentially with system size. In this work, we develop a perfect-sampling method to calculate the second-order MRE from
matrix product states (MPSs). Our method uses a bounded
estimator to control sampling fluctuations and a recursive sweep to draw the samples directly from the input MPS, which allows us to generate each sample with $\mathcal O(nD^3)$ time, where $n$ and $D$ denote the number of modes and MPS bond dimension, respectively. We
benchmark our method on the XXZ chain with up to $128$ sites, demonstrating that the MRE captures intricate higher-order correlations at large scales, which are inaccessible to covariance-based measures. These results provide a computational tool that quantitatively evaluates many-body fermionic non-Gaussianity by accounting for higher-order correlations.
Read the full abstract ▾
High Energy Physics (Experiment)
Search for pair-produced vector-like top quarks decaying into Lorentz-boosted top quarks and scalar bosons in proton-proton collisions at $\sqrt{s}$ = 13 TeV
CMS Collaboration
A search for pair-produced vector-like top
quarks, T, decaying into a new scalar
boson $\phi$ and a standard model (SM) top
quark is presented. The search targets events containing a
photon pair originating from the decay of one of the scalar
bosons, accompanied by all-hadronic decays of the SM top
quark pair. The analysis is optimized for boosted top
quark signatures in which the decay products of the top
quarks are reconstructed as large-radius jets. The search is based on
proton-
proton collision data at $\sqrt{s}$ = 13 TeV, collected by the CMS experiment at the CERN LHC during 2016$-$2018, corresponding to an integrated luminosity of 138 fb$^{-1}$. The search is performed for an array of T and $\phi$ masses. No significant deviation from the predicted background is observed. The largest local excess has a significance of 2.7 standard deviations, reduced to 1.5 standard deviations after accounting for the look-elsewhere effect. Upper limits at 95% confidence level are set on the product of $\mathrm{T\bar{T}}$ production cross section and the branching fraction.
Read the full abstract ▾
High Energy Physics (Phenomenology)
NNLO QED corrections and inelastic two-photon exchange in elastic lepton-proton scattering with McMule
Matteo Ronchi
We supplement McMule, a Monte Carlo framework that provides QED corrections up to next-to-next-to-leading order (NNLO) in the fine structure constant $\alpha$, with the inelastic two-
photon exchange (TPE) contribution, based on the data-driven dispersive calculation of Tomalak, Pasquini and Vanderhaeghen, which we extend to the $Q^2\rightarrow 0$ limit that enables applications in the low-$Q^2$ region relevant for upcoming low-energy experiments. We present results for two experimental settings: the future MAGIX@MESA experiment and the ISR@MAMI measurement. For MAGIX@MESA kinematics, the inelastic TPE is small, comparable to the
proton-side NLO corrections and subdominant to both the leptonic radiative corrections and the full NNLO QED corrections once a 1 MeV
photon-energy cut is applied. For the ISR@MAMI kinematics, NNLO QED corrections modify the radiative tail below the elastic peak at the 10% level.
Read the full abstract ▾
High Energy Physics (Theory)
On the Stability of Warped Anti-de Sitter Spaces in Supergravity
S. Maurelli, R. Noris, M. Oyarzo et al. (+3 more)
We discuss the perturbative stability of warped anti-de Sitter (WAdS$_3$) spaces in three-dimensional gauged supergravity. To this end, we first derive the analogue of the Breitenlohner-Freedman bound for a single scalar field on such a curved background. We then apply this analysis to the half-maximal $D=3$ gauged supergravity obtained from the compactification of the $D=6$, $\mathcal{N}=(1,1)$ supergravity on S$^3$. Families of three-dimensional configurations, uplifting to spaces of the form $\mathrm{WAdS}_3 \times \mathrm{WS}^3$, are found by turning on appropriate vector and scalar fields, supporting the AdS$_3$ and S$^3$ warpings, respectively. Finally, we show that the spectra of scalar fluctuations satisfy the stability criteria for each solution.
Read the full abstract ▾
All authors S. Maurelli, R. Noris, M. Oyarzo, A. Saha, H. Samtleben, M. Trigiante
Instrumentation and Methods for Astrophysics
Design, Fabrication, and Free-Space Characterization of a Two-Photon-Polymerized Nano-printed Photonic Lantern
Kyra Watts, Natasha Popenoe, Benjamin Gerard et al. (+6 more)
Photonic lanterns provide an interface between multimode optical fields and arrays of single-mode waveguides, making them promising components for modal filtering, wavefront sensing, and high-contrast astronomical instrumentation. We present the design, simulation, two-
photon-polymerization fabrication, and free-space characterization of a compact photonic lantern optimized for operation at $ 1050~\mathrm{nm} $. The device was designed to transform a multimode input into five nominally single-mode output waveguides. Eigenmode-expansion simulations in Ansys Lumerical MODE were used to optimize the lantern geometry while minimizing insertion loss and output-channel power nonuniformity. The optimized structure was fabricated using a Nanoscribe Photonic Professional GT2 two-
photon-polymerization system and developed as a standalone
polymer-waveguide component. The fabricated lantern was characterized using a free-space optical setup consisting of a $ 635~\mathrm{nm} $
laser for preliminary characterization, collimation and focusing optics, and camera-based imaging of the transmitted fields. Measurements were used to assess optical throughput, output intensity distribution, and light-guiding performance. Differences between simulated and measured results may arise from the wavelength mismatch, fabrication tolerances, material and surface-scattering losses,
alignment errors, and deviations from the idealized material and
geometric parameters used in simulation. These results demonstrate a compact, additively manufactured photonic-lantern platform and establish a pathway toward free-space-coupled astrophotonic systems for future high-contrast
exoplanet-imaging instrumentation.
Read the full abstract ▾
All authors Kyra Watts, Natasha Popenoe, Benjamin Gerard, Paul Pax, Dominic Sanchez, David Feng, C. Cole Dunn, Cari Johnston, Xiaoxing Xia
General Relativity and Quantum Cosmology
Unimodular boundary time for Regge calculus
Steffen Gielen and Sofie Ried
Henneaux-Teitelboim
gravity is a diffeomorphism-invariant formulation of unimodular
gravity that is locally equivalent to general relativity but includes an extra boundary variable, unimodular time, whose difference between hypersurfaces measures the enclosed 4-volume. In general, unimodular versions of
quantum gravity can be expected to deviate from theories based on general relativity, but a discrete path-integral formulation for Henneaux-Teitelboim
gravity has not yet been established. In this paper, we discretise Henneaux-Teitelboim
gravity using the methods of Euclidean Regge calculus. Testing this framework in a
symmetry-reduced model of Regge cosmology, we reproduce results in previous literature and demonstrate that the continuum limit can be naturally defined using unimodular time rather than proper time. Because unimodular time appears as boundary data as opposed to being a degree of freedom in the bulk, this approach allows for the comparison of general simplicial triangulations, beyond highly symmetric discretisations, to the continuum. Our work provides a first step towards a discrete path-integral formulation of Henneaux-Teitelboim
gravity and adds a new perspective on time as a boundary variable in
quantum gravity.
Read the full abstract ▾
Statistical Mechanics
Minimax entropy production for arbitrary processes
Mahran Yousef, Ben Ansbacher and David H. Wolpert
For any physical process, varying the initial distribution over its states will change the resulting expected
entropy production (EP). An initial distribution that minimizes the EP of a particular process is called the prior of that process. Varying the microphysical details of the process will change its prior. We consider the following question: if an engineer wants to design a system to implement a given map, what prior should they design into the system to minimize the EP for the worst-case actual distribution? We refer to the resulting optimal worst-case value as the minimax EP, and investigate how it depends only on the dynamics of the process. We derive the closed-form solution to this minimax problem when the map is deterministic. We also show that for
stochastic maps, a worst-case actual distribution can always be chosen to be a point mass on a single state, and that the associated minimax prior resembles a Boltzmann-Gibbs equation and can be found by a globally convergent numerical
algorithm. We further show that the minimax EP is the maximum uncertainty about the input that remains after observing the output. Finally, we extend the analysis to the continuous-time regime, showing that the minimax instantaneous EP diverges, while the corresponding finite-time minimax EP has a universal short-time scaling set by the largest escape rate of the dynamics.
Read the full abstract ▾
High Energy Physics (Phenomenology)
Three-loop rapidity anomalous dimension for jet-veto cross sections
Samuel Abreu, Jonathan R. Gaunt, Pier Francesco Monni et al. (+2 more)
We present the first calculation of the third-order corrections to the rapidity anomalous dimension for jet-veto cross sections. This is a crucial ingredient for the resummation of these scattering observables in key processes such as colour-singlet and heavy-
quark-pair production at
hadron colliders. More precisely, our results enable the next-to-next-to-next-to-leading logarithmic (N$^3$LL) resummation of the jet-veto cross section for colour singlet production at the LHC, with immediate phenomenological relevance. The anomalous dimension is extracted from a calculation of the three-loop soft function in soft-collinear effective field theory, and is presented as a function of the jet radius $R$ for the clustering
algorithms of the generalised-$k_t$ family. To handle the complexity associated with the clustering
algorithm, we formulate a semi-numerical computational approach. This strategy is itself a result of the paper, and can be extended to the calculation of other anomalous dimensions and soft functions at three loops.
Read the full abstract ▾
All authors Samuel Abreu, Jonathan R. Gaunt, Pier Francesco Monni, Luca Rottoli, Robert Szafron
Cosmology and Nongalactic Astrophysics
A novel, fast, and accurate code for cosmological loop calculations
Tjark Harder, Luca Amendola, Thiago S. Pereira et al. (+1 more)
We introduce neckar, a public code for the one-loop matter and
galaxy power spectrum, as well as correlation function, in the Eulerian Effective Field Theory of Large-Scale Structure (EFTofLSS). It is based on the FFTLog expansion, and is designed for fast and accurate parameter inference from large-scale structure data, making it a powerful tool for high-dimensional
Bayesian analyses of current and upcoming
galaxy surveys. neckar combines several numerical and analytical improvements, including the separation between pre-computable and cosmology-dependent contributions, a semi-analytic treatment of the Alcock-Paczynski effect for power spectrum multipoles, and an implementation of the
symmetry-based bootstrap kernels, allowing straightforward applications to a broader class of cosmological models. The code also incorporates an improved infrared resummation scheme that corrects previous implementation inaccuracies, and which led to errors of the order of 1% for the quadrupole, and of 10% for the hexadecapole at scales $k \gtrsim 0.1 h \textrm{Mpc}^{-1}$, as well as an asymptotic treatment that extends the range of accurate predictions into mildly non-linear scales $k \sim 0.4 h \textrm{Mpc}^{-1}$. This leads to relevant corrections in the correlation function around the BAO peak. Taken altogether, these improvements render neckar up to two orders of magnitude faster than similar existing codes without relying on emulators, and at the same time improving numerical accuracy. The code is written in C and is distributed with a Python wrapper for convenience.
Read the full abstract ▾
All authors Tjark Harder, Luca Amendola, Thiago S. Pereira, Miguel Quartin
Data Analysis and Statistics · Cross-listed from stat.ML
When Is Accuracy Evidence? A Unified Theory of Generalisation, Validation, and Information Fusion
JM Gorriz
K-fold cross-validation (CV) is widely used as evidence of out-of-sample performance, although folds are neither independent experiments nor equally informative under heterogeneous data. Cross Upper-Bound Validation (CUBV) replaces point-wise CV accuracy by conservative upper bounds on true risk. Here we generalise CUBV through a single exponential framework in which the moment-generating function of the generalisation gap is controlled by a cumulant envelope gamma(lambda). This yields a family of risk bounds covering Hoeffding-, Bernstein-, dependency-aware, PAC-
Bayesian, and heterogeneous source-fusion settings. For K-fold CV, dependence between fold-wise gaps is modelled through a joint sub-Gaussian proxy
matrix. Under equicorrelation, this gives an effective number of folds, Keff = K/[1+(K-1)rho], showing that increasing K does not necessarily increase statistical evidence when folds are strongly dependent. The framework is also extended to posterior distributions over predictors and weighted multi-source fusion, where weights are selected by minimising an upper bound on future risk rather than empirical error alone. Experiments with trained linear classifiers on heterogeneous
multimodal Gaussian mixtures compare K-fold CV with full-sample resubstitution plus risk correction. Bounds are evaluated by coverage and tightness. In low-dimensional small-sample settings, K-fold partitioning can increase uncertainty because individual folds under-represent minority modes, while corrected resubstitution can remain valid and tighter; this effect disappears as sample size increases. Overall, gamma-CUBV separates observed performance, uncertainty, dependence, model complexity, and confidence into explicit terms, providing a unified route from CV scores to risk statements and a principled validation criterion for heterogeneous small-sample applications such as neuroimaging.
Read the full abstract ▾
Quantum Physics
Generalization of Transformer-Based Neural Quantum States via In-Context Learning
Zhen Qin, Qing Qu and Alfred O. Hero III
Neural
quantum states based on modern deep learning architectures have emerged as powerful representations for
quantum many-body systems. In particular,
Transformer-based neural
quantum states provide expressive models capable of capturing long-range correlations, and their empirical generalization performance has recently been demonstrated. However, a theoretical understanding of their generalization behavior remains largely unexplored. In this paper, we develop a theoretical framework to analyze the generalization properties of
Transformer-based neural
quantum states under in-context learning. We establish a rigorous inference-time generalization error bound in terms of mean squared error (MSE), showing that the pointwise prediction error decreases inversely with both the number of in-context examples and the depth of the
Transformer. We further show that the
Transformer depth required to achieve this guarantee scales only linearly with the system size–namely, the number of particles in continuous systems or the number of qudits in discrete systems. Building on this result, we extend our analysis to full
quantum states formulated as rank-one density operators, and derive MSE-based generalization bounds over both continuous and discrete domains under physical constraints. Finally, numerical simulations corroborate our theoretical analysis.
Read the full abstract ▾
Chemical Physics
Uniform instanton theory for bridge-mediated nonadiabatic tunneling
Imaad M. Ansari, George Trenins and Jeremy O. Richardson
Instanton theory provides a semiclassical approximation to nonadiabatic rate constants within a path-integral framework and captures
nuclear quantum effects such as tunneling and zero-point energy. Although the simplest reactions proceed directly from reactants to products, a number of important nonadiabatic processes involve three electronic states and react via a concerted mechanism through a virtual bridge state, also referred to as bridge-mediated tunneling or superexchange. In previous work, we have derived an instanton theory to describe such reactions using a dominant tunneling trajectory that propagates on each of the three potential energy surfaces. However, this approach is only valid when the bridge state is sufficiently low in energy. In contrast, in the high-bridge regime, the trajectories on the bridge surface become infinitesimally short, which causes the previous theory to break down. In this work, we derive the appropriate asymptotic approximation for the high-bridge regime and find that the resulting theory reduces to a two-state golden-rule instanton with an effective coupling that describes a nonresonant hop to the virtual bridge state. We further develop a uniform asymptotic instanton theory that eliminates divergences and smoothly connects the high- and low-bridge regimes. In a companion paper, we apply the method to study the quintet-to-singlet transition (via a triplet bridge) of an iron(II) complex.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
Complete Magnetic Hierarchy in Bichromatically Driven Unconventional Magnets
Pei-Hao Fu and Sayed Ali Akbar Ghorashi
We establish a general framework for engineering unconventional magnetism using bichromatic driving. We identify a sharp hierarchy: for a bichromatic drive with a generic even commensurate frequency ratio, the leading continuum $q$-wave magnet generates components only up to order $q-2$, whereas
lattice higher-gradient terms supply the missing $q-1$ and $q$ parities and complete the hierarchy through order $q$. We explicitly illustrate this new revised hierarchy on a $d$-wave altermagnet irradiated by a circularly-linearly polarized light, and show that the asymmetry of the driving field is transferred to the light-dressed electronic structure, producing momentum-asymmetric dispersions beyond the static and single-frequency limits. We further show that this band asymmetry is absent in the leading continuum expansion and originates from higher-gradient
lattice terms that are converted by the bichromatic drive into odd-in-momentum contributions. Extending the analysis to higher-order unconventional magnets, we further obtain complete
magnetic hierarchies for all $q$-parity unconventional magnets. Our results establish bichromatic Floquet driving as a general route for generating mixed-parity
magnetic hierarchies and dynamically engineering unconventional magnetism.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Forward Bayesian Inference for the Binary Black Hole Populations
Poulami Dutta Roy, Tanmaya Mishra, Achal Kumar et al. (+1 more)
We present PopCWB, a
Bayesian framework for the inference of the binary black hole (BBH) population based on the unmodeled search pipeline coherent WaveBurst (cWB). The standard population analysis takes an inverse approach by inferring the underlying population model parameters for a given set of detected events using the individual posterior samples. In PopCWB, we take a forward approach to population inference by varying population models to identify the most optimal one which describes the observed events. Rather than using event-level posterior samples, PopCWB uses a large set of simulated events reconstructed by cWB and their total mass, estimated with a machine-learning regression, to construct marginal probability distributions. These marginal probabilities are then used in the construction of the likelihood. We apply PopCWB to BBH events detected by cWB during the third observing run (O3) of the LIGO–Virgo–KAGRA detectors. We constrain an astrophysically motivated BBH population model that incorporates the effects of pulsational pair-instability
supernovae and dynamical mergers. The analysis predicts a maximum black hole mass of $\mathbf{45.5^{+5.3}_{-6.5} M_{\odot}}$ from
stellar evolution and an inferred local BBH merger rate of $\mathbf{23.1^{+11.3}_{-8.4} \, Gpc^{-3} yr^{-1}}$. We compare these results with the existing population models from the literature.
Read the full abstract ▾
All authors Poulami Dutta Roy, Tanmaya Mishra, Achal Kumar, Sergey Klimenko
High Energy Physics (Phenomenology)
Big Bang Nucleosynthesis Constraint on $B$-mesogenesis
James M. Cline, Jonas Frerick, Sebastian A. Naja et al. (+1 more)
$B$-mesogenesis is a low-temperature baryogenesis mechanism, that uses $CP$-violation of the $B$
mesons in the standard model to fulfill the Sakharov conditions. It requires a late period of matter domination by a scalar field $\Phi$ that decays into $b\bar b$
quarks, reheating the Universe below the QCD phase transition. We investigate the impact of this mechanism on Big Bang Nucleosynthesis, with respect to the reheating temperature $T_{rh}$, and the mass of $\Phi$. Injection of
hadrons skewing
neutron/
proton interconversions are the most important effect, followed by
neutrino heating from $\Phi$ decays. For $M_\Phi\lesssim 100\,$GeV, $T_{rh}$ must be $\gtrsim 10\,$MeV.
Read the full abstract ▾
All authors James M. Cline, Jonas Frerick, Sebastian A. Naja, Yong Xu
Materials Science
Magnetic-Order-Driven Nonlinear Photocurrents in PT-Broken Antiferromagnetic MnS2 and Altermagnetic MnSe2
Fu Li, Rajyavardhan Ray, Xiaoxiong Liu et al. (+6 more)
Nonlinear photocurrent responses generally require inversion-
symmetry breaking, but its origin can be
magnetic rather than structural. In this study, we investigate the bulk photovoltaic effect in
antiferromagnetic MnS2 and altermagnetic MnSe2, two pyrite-type
semiconductors whose
magnetic ordering breaks inversion
symmetry P and its combination with time reversal PT, while the accompanying
lattice distortion is minute. We calculate the shift current (SC) and injection current (IC) responses under linearly and circularly polarized light with and without
spin-orbit coupling (SOC) and identify their
symmetry-allowed tensor components using the corresponding
magnetic and
spin point groups, respectively. Linear SC and circular IC are
symmetry-allowed in both MnS2 and MnSe2 irrespective of SOC, whereas linear IC and circular SC remain forbidden in MnS2 but become allowed in MnSe2 only when SOC is included. These results highlight the importance of SOC and the corresponding MPG analysis for a complete description of nonlinear charge photocurrents in
magnetic materials. Beyond charge responses, MnSe2 supports linear shift and circular injection
spin photocurrents in the nonrelativistic limit, whereas all
spin-photocurrent responses are forbidden in MnS2. Our findings therefore establish inversion
symmetry breaking induced by compensated
magnetic order as a route to generating and controlling nonlinear photocurrents.
Read the full abstract ▾
All authors Fu Li, Rajyavardhan Ray, Xiaoxiong Liu, Babu Baijnath Prasad, Chen Shen, Yaqian Guo, Jeroen van den Brink, Hongbin Zhang, Harish K. Singh
Cosmology and Nongalactic Astrophysics
Dark Energy Survey Year 6 Results: fast and interpretable posterior predictive checks for correlated cosmic probes
C. Doux, J. Muir, A. Ferté et al. (+59 more)
We present a fast and numerically stable framework for conducting posterior predictive distribution (PPD) tests of internal consistency in correlated cosmological probes. Our method, developed as a validation check for the Dark Energy Survey (DES) Year 6 combined analysis of weak
lensing and
galaxy clustering, employs a Gaussian-mixture model to efficiently approximate the high-dimensional PPD and introduces a scalar consistency metric, $\Delta_{\rm PPD}$, defined as the fraction of the PPD at lower probability density than the observed data. This method avoids challenges related to calibration and numerical stability that impacted PPD methods previously used in DES Year 3. After demonstrating performance with a toy model, we confirm that when applied to DES Year 3 measurements, $\Delta_{\rm PPD}$ identifies the same inter-probe tensions as published, calibrated PPD results while requiring only minutes per test. We further validate the method on several noise realizations of simulated DES Y6 analyses, demonstrating that $\Delta_{\rm PPD}$ responds coherently to injected inconsistency, while highlighting two effects which can complicate the interpretation of PPD tests for increasingly complex models. First, internal tensions that can be absorbed as shifts in nuisance parameters become more difficult to detect. Second, poorly constrained directions in parameter space can induce projection effects in PPDs for disjoint sets of observables, producing reports of tension even for consistent data. We conclude that $\Delta_{\rm PPD}$ provides a practical PPD-based diagnostic for multiprobe unblinding, to be interpreted with care alongside other validation checks. This framework has already played an important role in DES analyses and is well suited for application to forthcoming Stage-IV surveys such as LSST, Euclid, and Roman, where fast, robust internal consistency tests will be essential.
Read the full abstract ▾
All authors C. Doux, J. Muir, A. Ferté, M. Raveri, D. Sanchez Cid, N. Weaverdyck, E. J. Baxter, W. d'Assignies, T. Karwal, A. Amon, D. Anbajagane, F. Andrade-Oliveira, M. R. Becker, J. Blazek, A. Carnero Rosell, C. Chang, J. M. Coloma-Nadal, M. Crocce, J. DeRose, S. Dodelson, G. Giannini, E. Krause, E. Legnani, N. MacCrann, J. Mena-Fernández, A. Porredon, J. Prat, C. Preston, M. Rodriguez-Monroy, P. Rogozenski, R. Rosenfeld, S. Samuroff, E. Sanchez, I. Sevilla-Noarbe, M. Soares-Santos, C. To, M. A. Troxel, M. Yamamoto, B. Yin, J. Zuntz, S. Allam, M. Aguena, D. Bacon, D. Brooks, R. Camilleri, R. Cawthon, L. N. da Costa, S. Desai, P. Doel, K. Glazebrook, K. Honscheid, D. Huterer, K. Kuehn, J. L. Marshall, R. Miquel, M. Paterno, A. A. Plazas Malagón, M. Smith, E. Suchyta, D. L. Tucker, V. Vikram, J. Weller
Quantum Physics
Lucio De Simone, Lorenzo Capra, Arthur Vesperini et al. (+3 more)
Quantum entanglement is a fundamental resource in
quantum information theory, yet its general characterization and quantification remain challenging, especially in multipartite systems. In this work we investigate
entanglement from a
geometric perspective, focusing on the Riemannian structure induced by the Fubini–Study metric on the projective
Hilbert space of multi-
qubit quantum states. By exploiting the local-
unitary invariance of this metric, we derive the
entanglement distance (ED), a
geometric measure that quantifies
entanglement as an obstruction to locally minimizing the sum of squared Fubini–Study distances generated by local operations. We analyze the properties of ED for pure multi-
qubit states and discuss its behavior under local operations and classical communication. In particular, we show that ED reproduces established
entanglement measures in well-defined and restricted settings. For pure states of two
qubits, ED reduces to an exact monotone function of the concurrence and, independently, to an explicit monotone function of the
entropy of
entanglement. These results provide a clear
geometric interpretation of standard bipartite
entanglement measures within the present framework, while highlighting the limitations of such correspondences beyond the two-
qubit case.
Read the full abstract ▾
All authors Lucio De Simone, Lorenzo Capra, Arthur Vesperini, Leonardo Rossi, Loris Di Cairano, Roberto Franzosi
Chemical Physics
Electronic Density versus Geometry for Machine-Learned Molecular Absorption Spectra
Siddharth Dhanpal, Peter Elliott, Paolo Emilio Trevisanutto et al. (+2 more)
Molecular optical absorption spectroscopy provides a direct probe of electronic structure and is widely used for molecular identification, interpretation of photophysical behaviour, and planning of spectroscopy experiments. Calculating the absorption spectra using first-principle excited-state methods, however, is computationally demanding, at least compared to ground-state calculations, which limits their routine application across large molecular sets. Machine-learning (ML) surrogates can reduce this cost and allow rapid spectral prediction. However, their performance depends strongly on how molecular information is represented. Here, we compare using the ground-state electron density versus the molecular geometry as inputs to a ML model for predicting absorption spectra, for a training set of 6874 molecules selected from the QM7
dataset. For each of these molecules, the density was calculated using density functional theory (DFT) and the absorption spectrum was calculated using linear-response (LR) time-dependent DFT (TDDFT). Utilizing the ground-state density as the input to the ML model is motivated by the Hohenberg-Kohn and Runge-Gross
theorems, and the fact that the ground-state density encodes information about bonding, charge localisation, and electronic delocalisation. Hence, it may be a more judicious starting point for the ML model compared to the geometry, as it effectively decouples the chemistry of the ground-state. The question we test is whether the benefits of using the density outweigh the (notprohibitive) penalty of requiring an additional single-point DFT calculation for the density. We find that the density-based convolutional neural network achieves a validation correlation of 0.9926, compared with 0.9795 for the best geometry-based graph model, reducing the residual decorrelation, by approximately 64%.
Read the full abstract ▾
All authors Siddharth Dhanpal, Peter Elliott, Paolo Emilio Trevisanutto, Alin M. Elena, Gilberto Teobaldi
Quantum Physics
An exact semidefinite characterization of the stoquasticity cone of permutationally invariant Bell operators
Jan Li, Owidiusz Makuta, Evert van Nieuwenburg et al. (+1 more)
Bell correlations have been detected in atomic ensembles ranging from hundreds to hundreds of thousands of particles, witnessed by the permutationally invariant (PI) Bell operators. For all the operators realized so far, the maximally violating state can be brought, in a suitable basis, into a nonnegative-amplitude form. In that basis, the Bell operator is stoquastic. The coefficients parametrising these operators that at the same time lead to stoquasticity form a convex cone, the so-called stoquasticity cone. Its characterization had remained open beyond two-body operators, as for many-body operators the number of inequalities grows with the system size $n$. In this work we show that, in the thermodynamic limit, the stoquasticity cone admits an exact semidefinite characterization, valid at any operator order. The key observation is that, along each off-diagonal, the
matrix elements are the values of a single univariate
polynomial. Being univariate, this condition is equivalent to a linear
matrix inequality, with no relaxation hierarchy. Therefore, deciding stoquasticity becomes a single semidefinite feasibility problem. As its lowest-degree instances, this description recovers the known three-hyperplane characterization for two-body operators and yields, for three-body operators, a curved boundary.
Read the full abstract ▾
All authors Jan Li, Owidiusz Makuta, Evert van Nieuwenburg, Jordi Tura
Materials Science
Recrystallization as a tool to characterize and control the properties of cold sprayed materials: case study on 316L steel
Petr Haušild, Jaroslav Čech, Petr Králíček et al. (+2 more)
Owing to the unique buildup mechanisms, recrystallization in cold sprayed materials significantly differs from that in conventional counterparts. In this study, the relationship between deformation-induced microstructural heterogeneity, recrystallization behavior, and mechanical properties of cold sprayed materials was investigated using EBSD and nanoindentation. The 316L stainless steel was selected as a model material. The deposit was characterized in its as-sprayed condition and after annealing at temperatures between 900 and 1100 K. Thermomechanical estimates suggest that locally, temperature can rise over 1000 K and very high dislocation densities (up to 1017 m-2) form at particle boundaries during impact, providing a strong driving force for subsequent recrystallization. The EBSD observations confirmed the intense defect accumulation and grain fragmentation localized near the particle interfaces. Recrystallization initiated preferentially in these highly strained areas after annealing at 1000 K and progressed with increasing temperature and holding time, leading to complete recrystallization after 1 h at 1100 K. The recrystallized grain-size distribution was well described by a heavy-tailed log-normal distribution, which indicates extremely heterogeneous strain partitioning generated during particle impacts. Nanoindentation measurements showed that the high hardness of the cold sprayed deposit remained largely unchanged after annealing at 900 K but gradually decreased as recrystallization progressed. We further demonstrate that controlled post-spray recrystallization can serve as a powerful tool for characterizing deformation during deposition and for tailoring the microstructure and mechanical properties of cold-sprayed materials.
Read the full abstract ▾
All authors Petr Haušild, Jaroslav Čech, Petr Králíček, Tomáš Heller, Jan Cizek
Plasma Physics
Hong Qin
The susceptibility tensor of a homogeneous collisionless magnetized
plasma possesses parity-time (PT)
symmetry. For a stationary gyrotropic
equilibrium, with the wave vector $\mathbf{k}$ and the
equilibrium magnetic field $\mathbf{B}_0$ in the $x$–$z$ plane, the kinetic response satisfies $\chi(\omega^*,\mathbf{k})=R\chi(\omega,\mathbf{k})^*R$, where $R=\operatorname{diag}(1,-1,1)$. We show that the susceptibility PT-
symmetry is a reduced-response-space manifestation of PT
symmetry of the underpinning kinetic system. We identify parity $P$ and time reversal $T$ on the electromagnetic kinetic eigenmode space and show that the
Hamiltonian operator $\mathcal{H}_{\mathrm{VM}}$ of the linearized Vlasov–Maxwell system is PT-symmetric, satisfying $PT\mathcal{H}_{\mathrm{VM}}(PT)^{-1}=\mathcal{H}_{\mathrm{VM}}$. The PT
symmetry of the homogeneous magnetized Vlasov–Poisson eigenproblem is also established. Many kinetic instabilities associated with nonmonotonic distributions, rings, loss cones, and resonant energetic-particle populations are fundamentally spontaneous PT-
symmetry breaking, which is achieved through and only through Krein collisions. Three examples demonstrate distinct utilities of this analysis. Definite-sign cyclotron residues protect thermal Bernstein modes from spontaneous PT-
symmetry breaking. The nonmonotonic Dory–Guest–Harris distribution permits sign-indefinite residues and Krein collisions, for which we derive an analytical instability threshold and growth rate. The recently discovered mode-pole resonance instability provides a distinct realization of spontaneous PT-
symmetry breaking and illustrates how PT
symmetry can guide the discovery of kinetic instabilities with applications to fusion energy. These results establish PT
symmetry as a structural principle of
plasma waves and instabilities and open new directions for studying spectral
topology in kinetic
plasmas.
Read the full abstract ▾
Solar and Stellar Astrophysics
The origin of dispersion in the wind mass-loss rate–luminosity relation of massive O stars
Jiri Krticka and Iva Krtickova
Stellar winds of hot
stars are accelerated by the radiative force that mainly comes from the line transitions of heavy elements. As a result, the wind mass-loss rate is expected to scale mostly with the
stellar luminosity. This scaling clearly emerges from the observational analysis of O
stars and their winds, but with substantial scatter. The origin of this scatter is unclear. Part of the scatter of the observational relation between the hot
star wind mass-loss rate and luminosity may originate from the sensitivity of the mass-loss rate to other
stellar parameters besides the luminosity, such as the effective temperature, mass, and
metallicity. We tested this possibility using our wind models. We calculated tailored wind models for
stellar parameters corresponding to selected individual O
stars from the Large Magellanic Cloud as derived from a previous analysis. To model the wind, we used our global wind code that calculates the radiative force from the solution of the radiative transfer equation in the comoving frame. Wind models calculated for particular
stellar parameters reproduce the observational mass-loss rates better than simple scaling relations derived from model grids. This indicates that the dependence of the mass-loss rate on the other
stellar parameters except the luminosity might explain part of the dispersion in the relation between the mass-loss rate and luminosity. However, some dispersion still remains, which might indicate that wind variability is another source of the dispersion.
Read the full abstract ▾
Quantum Physics
Fault tolerance of quantum circuits with tensor networks and symplectic geometry
Soham Ghosh, Holger Boche and Andrew Tanggara
We develop an operator-algebraic framework for analyzing fault tolerance in
quantum circuits and establish necessary and sufficient conditions for exact recovery of the ideal computation under a prescribed noise model. For prescribed
circuit families and noise models, we derive a semidefinite program (SDP) based test whose infeasibility certifies that there does not exist any recovery map restoring its intended operation. For non-adaptive stabilizer
circuits, analyzing the stabilizer
symmetries of its components with
symplectic geometry, we obtain closed-form detection and logical-effect
matrices that characterize
circuit distance algebraically. Applied to a finite Hastings–Haah honeycomb Floquet-code
circuit, these
matrices certify the dynamical encoding of two logical
qubits and distance four under Pauli noise including measurement errors. Using these
matrices, we then derive MacWilliams identities for
circuit weight enumerators and obtain linear-programming (LP) upper bounds on
circuit distance. Output-code constraints give additional Singleton-like bounds. Under independent and identically distributed (i.i.d.) depolarizing noise, the weight enumerators determine decoder failure probabilities and yield upper bounds on
circuit pseudothresholds. Finally, we derive LP distance bounds for families of flag syndrome-extraction
circuits specified by their CNOT orderings, by incorporating the $t$-flag criterion as additional linear constraints to the distance-bounding LP. An analytical CSS Hamming-code
benchmark yields a tight distance-three bound attained by the Chao–Reichardt one-flag construction.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Guide field effects on particle acceleration in three-dimensional relativistic magnetic reconnection
Despina Karavola, Lorenzo Sironi and Maria Petropoulou
Relativistic
magnetic reconnection is a key mechanism for particle acceleration in astrophysical
plasmas. Recent 3D particle-in-
cell simulations have shown that, for weak guide fields, particles can be accelerated at nearly the maximal rate by escaping the reconnected
plasma and gaining energy from the large-scale upstream electric field. Here, we investigate whether this fast acceleration channel persists as the guide field becomes comparable to the reconnecting field. We perform 3D simulations of relativistic pair-
plasma reconnection, complemented by corresponding 2D runs, using open boundaries along the reconnection
outflows to establish a quasi-steady state. We find that increasing the guide field strength reduces the reconnection rate and causes energetic particles to become more closely aligned with the local
magnetic field. In 3D, the fast acceleration channel—absent in 2D—persists across the full range of guide fields investigated, but involves a progressively smaller fraction of particles as the guide field increases. Consequently, stronger guide fields produce steeper particle energy spectra and lower maximum Lorentz factors.
Read the full abstract ▾
Materials Science
Floquet density response in laser-assisted fast-electron scattering from solids
Sascha Schäfer, Richard Korytár and Ferdinand Evers
We extend the Bethe–Floquet formalism of Joachain and coworkers, originally developed for
laser-assisted electron–atom collisions, to inelastic scattering of fast electrons from a many-body condensed-matter target in a time-periodic light field. At first order in the projectile–target interaction, the general Floquet–
Fourier cross section separates into exact
laser-dressed projectile kernels and a
matrix-valued Floquet density response of the target. For spatially structured or translationally non-invariant systems, the latter is the bi-momentum Floquet structure factor; its momentum diagonal defines the Floquet generalization of the dynamic structure factor, constrained by Hermiticity, positivity, and sum rules. As a controlled realization of the general projectile kernel, an eikonal–Volkov approximation for slowly varying inhomogeneous fields yields a finite-momentum-resolution convolution of the target response. In the homogeneous-field dipole limit, the projectile kernel reduces to Bessel-function sidebands and the cross section takes the familiar Bethe–Floquet form. The Floquet density correlator separates exactly into the outer product of the pump-induced coherent mean density and connected fluctuations. In the straight-trajectory nonrecoil limit, the coherent, target-elastic sector defines the weak-coupling PINEM amplitude; repeated coherent insertions generate the PINEM Bessel ladder, with an explicit no-double-counting prescription for combining this channel with connected losses. As worked examples, we evaluate the connected, target-changing cross section analytically for a metal in the Drude and diffusive limits, recovering Bessel-weighted plasmon-loss and diffusive combs, and for a driven two-level model that exhibits off-diagonal Floquet coherences through Bessel-channel interference.
Read the full abstract ▾
Instrumentation and Detectors
Controlled-illumination smartphone imaging for quantitative turbidity measurement and cross-device transfer
Sebastian Olivares, Addles Castillo, Patricia Velasquez et al. (+2 more)
Smartphone imaging could provide a low-cost turbidity measurement method if illumination and acquisition geometry are controlled. We evaluated a 3D-printed enclosure with fixed illumination and a submerged optical target using 162 milk-based suspensions spanning 0.16–50.2 nephelometric turbidity units (NTU), with a portable turbidimeter as the reference. An EfficientNetB0 regression model evaluated using repeated five-fold grouped cross-validation achieved a mean absolute error (MAE) of 1.208 NTU and $R^2=0.9816$, indicating that predictions followed the reference measurements closely. The MAE was 0.335 NTU below 1 NTU and 0.449 NTU from 1 to below 5 NTU; classification accuracy at the operational 5-NTU threshold was 0.9753. When applied without retraining to 103 paired images from a second smartphone, prediction error remained comparable to that on the development smartphone below 10 NTU, but turbidity was increasingly underestimated at higher values. The results demonstrate the measurement performance attainable with a controlled smartphone acquisition system, quantify an important device-dependent transfer limitation, and motivate standardized multi-device acquisition and prospective natural-water validation.
Read the full abstract ▾
All authors Sebastian Olivares, Addles Castillo, Patricia Velasquez, Roxana Arce, Nicolas Richardson
Quantum Physics
Subdimensional linear-optical quantum computation: from qudit resource states to qubit quantum computation
Tomohiro Yamazaki
In this paper, we propose a linear-optical
quantum computation scheme that starts from high-dimensionally entangled qudits but performs
quantum computation on
qubits defined in their subspaces. This approach enables us to increase the success probability of linear-optical fusions from $50\%$ to $1-1/d$ for qudits of dimension $d$ without relying on existing approaches using ancilla
photons and
quantum codes. In particular, we show that a 2D cluster state of
qubits can be generated from 5-qudit 1D cluster states using pairwise fusion gates while preserving their boosted success probability. We numerically demonstrate that this approach can improve the loss tolerance of a percolation-based scheme while keeping the
photon number per resource state constant.
Read the full abstract ▾