Mon·Oct 21, 2024Monday·October 21, 2024

1. 01*

   MACK: Mismodeling Addressed with Contrastive Knowledge

   Liam Rankin Sheldon🇺🇸 · Dylan Sheldon Rankin🇺🇸 · Philip Harris🇺🇸

   The use of machine learning methods in high energy physics typically relies on large volumes of precise simulation for training. As machine learning models become more complex they can become increasingly sensitive to differences between this simulation and the real data collected by experiments. We present a generic methodology based on contrastive learning which is able to greatly mitigate this negative effect. Crucially, the method does not require prior knowledge of the specifics of the mismodeling. While we demonstrate the efficacy of this technique using the task of jet-tagging at the Large Hadron Collider, it is applicable to a wide array of different tasks both in and out of the field of high energy physics.

   hep-phcs.LGhep-exSciPost Phys.(2025)·3 citations
2. 02*

   Investigation of Mass and Decay Characteristics of the All-light Tetraquark

   Chetan Lodha🇮🇳 · Ajay Kumar Rai🇮🇳

   We investigate the mass spectra and decay properties of pions and all light tetraquarks using both semi-relativistic and non-relativistic frameworks. By applying a Cornell-like potential and a spin-dependent potential, we generate the mass spectra. The decay properties of tetraquarks are evaluated using the annihilation model and the spectator model. Potential tetraquark candidates are interpreted for quantum numbers $J^{PC}=0^{++},0^{-+},1^{-+},1^{+-},1^{--},2^{+-},2^{-+},$ and $2^{--}$. Additionally, we compare our results with existing experimental data and theoretical predictions to validate our findings. This study aims to enhance the understanding of tetraquarks in the light-light sector.

   hep-phFew Body Syst.(2024)·15 citations
3. 03*

   Degenerate scalar scenario of two Higgs doublet model with a complex singlet scalar

   Gi-Chol Cho🇯🇵 · Chikako Idegawa🇯🇵

   We study the two Higgs doublet model with a complex singlet scalar whose imaginary part acts as dark matter (DM). The scattering of DM and quarks, mediated by three CP-even scalars in this model, is suppressed when masses of CP-even scalars are degenerate; that is called the ``degenerate scalar scenario''. Based on this scenario, we show that the strong first-order electroweak phase transition (EWPT) can be achieved without conflicting with constraints from the DM relic density and the direct detection experiments. We also discuss a shift of scalar trilinear coupling from the Standard Model prediction, which could be a test of this model in collider experiments.

   hep-phPTEP(2025)·2 citations
4. 04*

   $D^0\overline{D^0}$ mixing from nonlocal condensate contributions

   Lovro Dulibić🇭🇷 · Blaženka Melić🇭🇷 · Alexey A. Petrov🇺🇸

   A significant discrepancy, spanning multiple orders of magnitude, exists between the leading order contribution to the $D^0\overline{D^0}$ mixing parameters and experimental values. This is largely due to the Glashow-Iliopoulos-Maiani (GIM) mechanism, which results in substantial suppression of the theoretical predictions. To bridge this gap, various efforts have been made to account for higher-order terms and nonperturbative effects, which, although suppressed in the operator product expansion (OPE), could potentially lead to a larger contribution by weakening the GIM cancellation through flavour SU(3) symmetry breaking. In this work, we compute the long-distance contributions of nonlocal QCD condensates within different models and, for the first time, determine the impact of the mixed condensate. Although our results still fall short of the experimental value, they represent an improvement over current theoretical estimates by an order of magnitude.

   hep-phPoS(2025)·4 citations
5. 05*

   Nature of X(3872) from recent BESIII data: Considering the universal feature of an S-wave threshold resonance

   Xian-Wei Kang🇨🇳 · Jin-Zhe Zhang🇨🇳 · Xin-Heng Guo🇨🇳

   We analyze the recent data from the BESIII collaboration on the $X(3872)$ state in the $J/\psi {\pi }^{+}{\pi }^{-}$ and $D^0{\bar{D}}^0{\pi }^0$ decay channels. The quantum number and mass of the $X(3872)$ state allow us to exploit the universal feature of the very near-threshold $D{\bar{D}}^{\ast }$ scattering in the $S$ wave. The analysis of $J/\psi {\pi }^{+}{\pi }^{-}$ data and $D^0{\bar{D}}^0{\pi }^0$ data separately as well as the combined analysis of these data together, all support the conclusion that $X(3872)$ is an extremely weakly bound charm meson molecule.

   hep-phhep-exnucl-thCPC(2025)·3 citations
6. 06*

   $\tilde{\tau }$ searches at future e${}^{+}$e${}^{-}$ colliders

   Mikael Berggren🇩🇪 · Maria Teresa Núñez Pardo de Vera🇩🇪 · Jenny List🇩🇪

   The direct pair-production of the superpartner of the $\tau$-lepton, the $\tilde{\tau }$, is one of the most interesting channels to search for SUSY in: the $\tilde{\tau }$ is likely to be the lightest of the scalar leptons, and is one of the most experimentally chalanging ones. The current model-independent $\tilde{\tau }$ limits come from LEP, while limits obtained at the LHC do extend to higher masses, but are model-dependent. The future Higgs factories will be powerful facilities for SUSY searches, offering advantages with respect to previous electron-positron colliders as well as to hadron machines. In order to quantify the capabilities of these future $e^{+}{e}^{-}$ colliders, the "worst-case" scenario for $\tilde{\tau }$ exclusion/discovery has been studied, taking into account the effect of the $\tilde{\tau }$ mixing on $\tilde{\tau }$ production cross-section and detection efficiency. To evaluate the latter, the ILD concept, originally developed for the International Linear Collider (ILC), and the ILC beam conditions at a centre-of-mass energy of 500 GeV have been used for detailed simulations. The obtained exclusion and discovery reaches extend to only a few GeV below the kinematic limit even in the worst-case scenario. The results of the detailed simulation study are then discussed in view of the experimental environment of other proposed Higgs factory projects.

   hep-phEPJ Web Conf.(2024)·3 citations
7. 07*

   Advancing Physics Data Analysis through Machine Learning and Physics-Informed Neural Networks

   Vasileios Vatellis🇬🇷

   In an era increasingly focused on green computing and explainable AI, revisiting traditional approaches in theoretical and phenomenological particle physics is paramount. This project evaluates various machine learning (ML) algorithms-including Nearest Neighbors, Decision Trees, Random Forest, AdaBoost, Naive Bayes, Quadratic Discriminant Analysis (QDA), and XGBoost-alongside standard neural networks and a novel Physics-Informed Neural Network (PINN) for physics data analysis. We apply these techniques to a binary classification task that distinguishes the experimental viability of simulated scenarios based on Higgs observables and essential parameters. Through this comprehensive analysis, we aim to showcase the capabilities and computational efficiency of each model in binary classification tasks, thereby contributing to the ongoing discourse on integrating ML and Deep Neural Networks (DNNs) into physics research. In this study, XGBoost emerged as the preferred choice among the evaluated machine learning algorithms for its speed and effectiveness, especially in the initial stages of computation with limited datasets. However, while standard Neural Networks and Physics-Informed Neural Networks (PINNs) demonstrated superior performance in terms of accuracy and adherence to physical laws, they require more computational time. These findings underscore the trade-offs between computational efficiency and model sophistication.

   hep-phcs.LG5 citations
8. 08*

   Enhancing Precision of Signal Correction in PVES Experiments: The Impact of Bayesian Analysis on the Results of the QWeak and MOLLER Experiments

   Elham Gorgannejad🇨🇦 · Wouter Deconinck🇨🇦 · David S. Armstrong🇺🇸

   The precise measurement of parity-violating asymmetries in parity-violating electron scattering experiments is a powerful tool for probing new physics beyond the Standard Model. Achieving the expected precision requires both experimental and post-processing signal corrections. This includes using auxiliary detectors to distinguish the main signal from background signals and implementing post-measurement corrections, such as the Bayesian statistics method, to address uncontrolled factors during the experiments. Asymmetry values in the scattering of electrons off proton targets in QWeak and P2 and off electron targets in MOLLER are influenced by detector array configurations, beam polarization angles, and beam spin variations. The Bayesian framework refines full probabilistic models to account for all necessary factors, thereby extracting asymmetry values and the underlying physics under specified conditions. For the QWeak experiment, a reanalysis of the inelastic asymmetry measurement using the Bayesian method has yielded a closer fit to measured asymmetries, with uncertainties reduced by 40\% compared to the Monte Carlo minimization method. This approach was successfully applied to simulated data for the MOLLER experiment and is predicted to be similarly effective in P2.

   hep-phnucl-exphysics.data-an0 citations
9. 09*

   Photon conversion to axions and dark photons in magnetized plasmas: a finite-temperature field theory approach

   Nirmalya Brahma🇨🇦 · Katelin Schutz🇨🇦

   Some of the most stringent constraints on physics beyond the Standard Model (BSM) arise from considerations of particle emission from astrophysical plasmas. However, many studies assume that particle production occurs in an isotropic plasma environment. This condition is rarely (if ever) met in astrophysical settings, for instance due to the ubiquitous presence of magnetic fields. In anisotropic plasmas, the equations of motion are not diagonal in the usual polarization basis of transverse and longitudinal modes, causing a mixing of these modes and breaking the degeneracy in the dispersion relation of the two transverse modes. This behavior is captured by a $3\times 3$ mixing matrix ${\pi }^{IJ}$, determined by projecting the response tensor of the plasma ${\Pi }^{\mu \nu }$ into mode space, whose eigenvectors and eigenvalues are related to the normal modes and their dispersion relations. In this work, we provide a general formalism for determining the normal modes of propagation that are coupled to axions and dark photons in an anisotropic plasma. As a key part of this formalism, we present detailed derivations of ${\Pi }^{\mu \nu }$ for magnetized plasmas in the long-wavelength limit using the real-time formalism of finite-temperature field theory. We provide analytic approximations for the normal modes and their dispersion relations assuming various plasma conditions that are relevant to astrophysical environments. These approximations will allow for a systematic exploration of the effects of plasma anisotropy on BSM particle production.

   hep-phastro-ph.HEphysics.plasm-phJHEP(2024)·6 citations
10. 10*

    Experimental targets for dark photon dark matter

    David Cyncynates🇺🇸 · Zachary J. Weiner🇺🇸

    Ultralight dark photon dark matter features distinctive cosmological and astrophysical signatures and is also supported by a burgeoning direct-detection program searching for its kinetic mixing with the ordinary photon over a wide mass range. Dark photons, however, cannot necessarily constitute the dark matter in all of this parameter space. In minimal models where the dark photon mass arises from a dark Higgs mechanism, early-Universe dynamics can easily breach the regime of validity of the low-energy effective theory for a massive vector field. In the process, the dark sector can collapse into a cosmic string network, precluding dark photons as viable dark matter. We establish the general conditions under which dark photon production avoids significant backreaction on the dark Higgs and identify regions of parameter space that naturally circumvent these constraints. After surveying implications for known dark photon production mechanisms, we propose novel models that set well-motivated experimental targets across much of the accessible parameter space. We also discuss complementary cosmological and astrophysical signatures that can probe the dark sector physics responsible for dark photon production.

    hep-phastro-ph.COPRD(2025)·42 citations
11. 11*

    A Comprehensive Analysis of Insight-HXMT Gamma-Ray Burst Data. I. Power Density Spectrum

    Zi-Min Zhou · Xiang-Gao Wang · En-Wei Liang · Jia-Xin Cao · Hui-Ya Liu · Cheng-Kui Li · Bing Li · Da-Bin Lin · Tian-Ci Zheng · Rui-Jing Lu

    Power Density Spectrum (PDS) is one of the powerful tools to study light curves of gamma-ray bursts (GRBs). We show the average PDS and individual PDS analysis with {\it Hard X-ray Modulation Telescope} (also named \insighthxmt) GRBs data. The values of power-law index of average PDS (${\alpha }_{\bar{P}}$) for long GRBs (LGRBs) vary from 1.58-1.29 (for 100-245, 245-600, and 600-2000 keV). The \insighthxmt\ data allow us to extend the energy of the LGRBs up to 2000 keV, and a relation between ${\alpha }_{\bar{P}}$ and energy $E$, ${\alpha }_{\bar{P}}\propto E^{-0.09}$ (8-2000 keV) is obtained. We first systematically investigate the average PDS and individual PDS for short GRBs (SGRBs), and obtain ${\alpha }_{\bar{P}}\propto E^{-0.07}$ (8-1000 keV), where the values of ${\alpha }_{\bar{P}}$ vary from 1.86 to 1.34. The distribution of power-law index of individual PDS ($\alpha$) of SGRB, is consistent with that of LGRB, and the $\alpha$ value for the dominant timescale group (the bent power-law, BPL) is higher than that for the no-dominant timescale group (the single power-law, PL). Both LGRBs and SGRBs show similar $\alpha$ and ${\alpha }_{\bar{P}}$, which indicates that they may be the result of similar stochastic processes. The typical value of dominant timescale $\tau$ for LGRBs and SGRBs is 1.58 s and 0.02 s, respectively. It seems that the $\tau$ in proportion to the duration of GRBs $T_{90}$, with a relation $\tau \propto T_{90}^{0.86}$. The GRB light curve may result from superposing a number of pulses with different timescales. No periodic and quasi-periodical signal above the 3$\sigma$ significance threshold is found in our sample.

    ↳ astro-ph.HEhep-phApJ(2024)·5 citations
12. 12*

    Structure of nuclei in dileptons production in proton-nucleus scattering

    Sergei P. Maydanyuk (1,2,3)🇨🇳 · Gyorgy Wolf (2) ((1) Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China, (2) Wigner Research Centre for Physics, Budapest, Hungary, (3) Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine)🇭🇺

    We investigate production of electron-positron pairs (dileptons) in the scattering of protons off nuclei. Focus is directed on clarifying role of nuclear interactions which make basis in mechanisms of scattering process and structure of nuclei. For that, we constructed a new model of production of dileptons, where scattering of nuclei and their structure are described on the basis of quantum mechanics. Cross sections of dilepton production are calculated in the scattering of protons on \isotope[9]{B} at energy of proton beam of 2.1~GeV. Tendency of the calculated full spectrum is in good agreement with experimental data of DLS Collaboration. Contribution of incoherent processes has a leading role in production of dileptons in comparison with coherent one. In our model calculated cross section of dileptons is sensitive to nuclear part of potential of interactions between proton and nucleus in scattering. Influence of structure of nucleus on calculations of cross sections of production of dileptons is essential. This result provides save basis for new opportunity to extract new information about structure of nuclei, nuclear part of potential from experimental data of dileptons at studied energies of proton beam.

    ↳ nucl-thhep-ph0 citations
13. 13*

    Quantum-annealing-inspired algorithms for multijet clustering

    Hideki Okawa🇨🇳 · Xian-Zhe Tao🇨🇳 · Qing-Guo Zeng🇨🇳 · Man-Hong Yung🇨🇳

    Jet clustering or reconstruction is a crucial component at high energy colliders, a procedure to identify sprays of collimated particles originating from the fragmentation and hadronization of quarks and gluons. It is a complicated combinatorial optimization problem and requires intensive computing resources. In this study, we formulate jet reconstruction as a quadratic unconstrained binary optimization (QUBO) problem and introduce novel quantum-annealing-inspired algorithms for clustering multiple jets in electron-positron collision events. One of these quantum-annealing-inspired algorithms, ballistic simulated bifurcation, overcomes problems previously observed in multijet clustering with quantum-annealing approaches. We find that both the distance defined in the QUBO matrix and the prediction power of the QUBO solvers have crucial impacts on the multijet clustering performance. This study opens up a new approach to globally reconstructing multijet beyond dijet in one go, in contrast to the traditional iterative method.

    ↳ quant-phhep-exhep-phPLB(2025)·5 citations
14. 14*

    Efficient charge-preserving excited state preparation with variational quantum algorithms

    Zohim Chandani · Kazuki Ikeda🇺🇸 · Zhong-Bo Kang🇺🇸 · Dmitri E. Kharzeev🇺🇸 · Alexander McCaskey🇺🇸 · Andrea Palermo🇺🇸 · C.R. Ramakrishnan🇺🇸 · Pooja Rao🇺🇸 · Ranjani G. Sundaram🇺🇸 · Kwangmin Yu🇺🇸

    Determining the spectrum and wave functions of excited states of a system is crucial in quantum physics and chemistry. Low-depth quantum algorithms, such as the Variational Quantum Eigensolver (VQE) and its variants, can be used to determine the ground-state energy. However, current approaches to computing excited states require numerous controlled unitaries, making the application of the original Variational Quantum Deflation (VQD) algorithm to problems in chemistry or physics suboptimal. In this study, we introduce a charge-preserving VQD (CPVQD) algorithm, designed to incorporate symmetry and the corresponding conserved charge into the VQD framework. This results in dimension reduction, significantly enhancing the efficiency of excited-state computations. We present benchmark results with GPU-accelerated simulations using systems up to 24 qubits, showcasing applications in high-energy physics, nuclear physics, and quantum chemistry. This work is performed on NERSC's Perlmutter system using NVIDIA's open-source platform for accelerated quantum supercomputing - CUDA-Q.

    ↳ quant-phcs.DChep-phphysics.chem-ph4 citations
15. 15*

    Black Holes Inside and Out 2024: visions for the future of black hole physics

    Niayesh Afshordi🇨🇦 · Abhay Ashtekar🇺🇸 · Enrico Barausse🇮🇹 · Emanuele Berti🇺🇸 · Richard Brito🇵🇹 · Luca Buoninfante🇳🇱 · Raúl Carballo-Rubio🇩🇰 · Vitor Cardoso🇩🇰 · Gregorio Carullo🇩🇰 · Mihalis Dafermos🇬🇧 · Mariafelicia De Laurentis🇮🇹 · Adrian del Rio🇪🇸 and 18 other authors

    The gravitational physics landscape is evolving rapidly, driven by our ability to study strong-field regions, in particular black holes. Black Holes Inside and Out gathered world experts to discuss the status of the field and prospects ahead. We hope that the ideas and perspectives are a source of inspiration. Structure: Black Hole Evaporation - 50 Years by William Unruh The Stability Problem for Extremal Black Holes by Mihalis Dafermos The Entropy of Black Holes by Robert M. Wald The Non-linear Regime of Gravity by Luis Lehner Black Holes Galore in D > 4 by Roberto Emparan Same as Ever: Looking for (In)variants in the Black Holes Landscape by Carlos A. R. Herdeiro Black Holes, Cauchy Horizons, and Mass Inflation by Matt Visser The Backreaction Problem for Black Holes in Semiclassical Gravity by Adrian del Rio Black Holes Beyond General Relativity by Enrico Barausse and Jutta Kunz Black Holes as Laboratories: Searching for Ultralight Fields by Richard Brito Primordial Black Holes from Inflation by Misao Sasaki Tests of General Relativity with Future Detectors by Emanuele Berti Black Holes as Laboratories: Tests of General Relativity by Ruth Gregory and Samaya Nissanke Simulating Black Hole Imposters by Frans Pretorius Black Hole Spectroscopy: Status Report by Gregorio Carullo VLBI as a Precision Strong Gravity Instrument by Paul Tiede Testing the nature of compact objects and the black hole paradigm by Mariafelicia De Laurentis and Paolo Pani Some Thoughts about Black Holes in Asymptotic Safety by Alessia Platania Black Hole Evaporation in Loop Quantum Gravity by Abhay Ashtekar How the Black Hole Puzzles are Resolved in String Theory by Samir D. Mathur Quantum Black Holes: From Regularization to Information Paradoxes by Niayesh Afshordi and Stefano Liberati

    ↳ gr-qcastro-ph.HEhep-phhep-th45 citations
16. 16*

    Constrains on dark matter cross section with standard model particles from the orbital period decay of binary pulsars

    Gonzalo Agustin Lucero🇦🇷 · Argelia Bernal🇲🇽 · Juan Barranco🇲🇽 · Andres Aceña🇦🇷

    It is shown that the data from the orbital period decay of binary pulsars give strong constraints on the dark matter-nucleons cross section. The limits are robust and competitive because this new method for testing dark matter interactions with standard model particles has a minimal number of assumptions combined with the extremely high accuracy on the measurement of the decay rate of the orbital period of binary systems. Our results exclude (with 95% confidence) spin independent interactions with cross sections greater that 3.1x10-31 cm2 for a dark matter particle with mass mc2 = 1 keV and 3.7x10-31 cm2 for mc2= 1 TeV which improves by several orders of magnitude previous constraints.

    ↳ astro-ph.HEhep-ph2 citations
17. 17*

    Chiral gauge theories, generalized anomalies and breakdown of the color-flavor-locked center symmetry

    Stefano Bolognesi🇮🇹 · Kenichi Konishi🇮🇹 · Andrea Luzio🇮🇹 · Matteo Orso🇮🇹

    We study the strong-interaction dynamics of a class of $4D$ chiral $SU(N)$ gauge theories with a fermion in a symmetric second-rank tensor representation and a number of fermions in an anti-antisymmetric tensor representation, extending the previous work on chiral gauge theories such as the Bars-Yankielowicz and the generalized Georgi-Glashow models. The main tool of our analysis is the anomalies obstructing the gauging of certain 1-form color-flavor-locked center symmetry, together with some flavor symmetries. The matching requirement for these mixed-anomalies strongly favors dynamical Higgs phases caused by bifermion condensate formation, against a confinement phase with no condensates and no symmetry breaking, or a confinement phase with multifermion color-singlet condensates only. Dynamical gauge symmetry breaking and the spontaneous breaking of a $U(1)$ symmetry caused by such condensates mean that the color-flavor-locked 1-form center symmetry itself is lost in the infrared. One is led to a solution, if not unique, which satisfies fully the conventional as well as the new, generalized 't Hooft anomaly matching requirements.

    ↳ hep-thhep-lathep-phJHEP(2025)·4 citations
18. 18*

    Regulator-independent equations of state for neutron stars generated from first principles

    J. M. Alarcón🇪🇸 · E. Lope-Oter🇪🇸 · J. A. Oller🇪🇸

    We study the equation of state (EoS) of a neutron star (NS) accounting for new advances. In the low energy density, $n\le 0.1n_s$, with $n_s$ the saturation density, we use a new pure neutron matter EoS that is regulator independent and expressed directly in terms of experimental nucleon-nucleon scattering data. In the highest-density domain our EoS's are matched with pQCD to $\mathcal{O}({\alpha }_s^3)$. First principles of causality, thermodynamic consistency and stability are invoked to transit between these two extreme density regimes. The EoS's are further constrained by the new measurements from PREX-II and CREX on the symmetry energy ($S_0$) and its slope ($L$). In addition, we also take into consideration the recent experimental measurements of masses and radii of different NSs and tidal deformabilities. A band of allowed EoS's is then obtained. Interestingly, the resulting values within the band for $S_0$ and $L$ are restricted with remarkably narrower intervals than the input values, with $32.9\le S_0\le 39.5\text{MeV}$ and $37.3\le L\le 69.0\text{MeV}$ at the 68\% CL. The band of EoS's constructed also allows possible phase transitions (PTs) for NS masses above 2.1~$M_{\odot }$ at 68\% CL for $n>2.5n_s$. We find both long and short coexistence regions during the PT, corresponding to first and second order PTs, respectively. We also generate the band of EoS's when excluding the astrophysical observables. This is of interest to test General Relativity and modified theories of gravity. Our band of EoS's for NSs can be also used to study other NS properties and dark matter capture in NS.

    ↳ nucl-thastro-ph.HEhep-phPRD(2025)·10 citations
19. 19*

    Does the oscillatory behavior of the Momentum Spectrum depend on the basis in the Post-Transient Stage?

    Deepak Sah🇮🇳 · Manoranjan P. Singh🇮🇳

    Pair creation by a spatially homogeneous, time-dependent electric field is studied within the framework of scalar quantum electrodynamics. We employ the standard Bogoliubov transformation approach to compute the single-particle distribution function in an adiabatic basis. We analyzed the distribution function of created particles in two different adiabatic bases (related by a unitary transformation). A novel dynamical scaling is observed while analyzing the oscillatory momentum spectrum of the pairs created by the Sauter pulsed field at intermediate times, calculated using the two adiabatic bases. In these bases, the same oscillatory momentum spectra are observed but at different times. However, when we scale the time by the point marking the end of the transient stage of dynamical evolution for each case of central momentum, the respective momentum spectra overlap. Furthermore, we study the time evolution of the momentum spectrum in the multi-photon regime and find that the spectra show a multi-modal profile structure at finite times for both choices of basis.

    ↳ quant-phhep-phhep-thphysics.plasm-ph0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.