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Rong Lu

Rong Lu appears in the imported research catalog. Authorship, coauthor and topic links are available while profile ownership is still unclaimed.

ResearcherUnclaimed source record
cond-mat.mes-hallcond-mat.stat-mechquant-phApplicationsArtificial IntelligenceBiological Physicscond-mat.othercond-mat.quant-gaseess.SYMachine LearningMethodologyphysics.atom-phphysics.ins-detphysics.optics

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Published work

12 published item(s)

preprint2026arXiv

Coherent Two-State Oscillations in False Vacuum Decay Regimes

Coherent two-state oscillations are observed in numerical simulations of the one-dimensional transverse-longitudinal-field Ising model (TLFIM) within false vacuum decay regimes. Starting from the false vacuum (a nearly fully polarized ferromagnetic state), we show that in moderate-sized systems, at resonances $h\approx 2J/n$ (with longitudinal field $h$, transverse field $J$, and an integer $n$), the expected decay can give way to coherent oscillations between the false vacuum and a symmetric resonant state. The oscillation frequency, i.e., the tunneling splitting, is observed notably to exhibit a superradiant-like $\sqrt{L}$ enhancement, as confirmed by a Schrieffer-Wolff analysis. In large chains, coherence remains for $n\gtrsim L/2$ due to bubble-size blockade and is robust against stronger transverse fields; for small $n$, long-range interactions can stabilize the oscillations by lifting multi-bubble degeneracies, establishing a robust many-body coherence mechanism beyond perturbative and finite-size limits.

0 citations0 reviewsNo code linkedOpen access
preprint2026arXiv

TADI: Tool-Augmented Drilling Intelligence via Agentic LLM Orchestration over Heterogeneous Wellsite Data

We present TADI (Tool-Augmented Drilling Intelligence), an agentic AI system that transforms drilling operational data into evidence-based analytical intelligence. Applied to the Equinor Volve Field dataset, TADI integrates 1,759 daily drilling reports, selected WITSML real-time objects, 15,634 production records, formation tops, and perforations into a dual-store architecture: DuckDB for structured queries over 12 tables with 65,447 rows, and ChromaDB for semantic search over 36,709 embedded documents. Twelve domain-specialized tools, orchestrated by a large language model via iterative function calling, support multi-step evidence gathering that cross-references structured drilling measurements with daily report narratives. The system parses all 1,759 DDR XML files with zero errors, handles three incompatible well naming conventions, and is backed by 95 automated tests plus a 130-question stress-question taxonomy spanning six operational categories. We formalize the agent's behavior as a sequential tool-selection problem and propose the Evidence Grounding Score (EGS) as a simple grounding-compliance proxy based on measurements, attributed DDR quotations, and required answer sections. The complete 6,084-line, framework-free implementation is reproducible given the public Volve download and an API key, and the case studies and qualitative ablation analysis suggest that domain-specialized tool design, rather than model scale alone, is the primary driver of analytical quality in technical operations.

0 citations0 reviewsNo code linkedOpen access
preprint2023arXiv

Application of machine learning to gas flaring

Currently in the petroleum industry, operators often flare the produced gas instead of commodifying it. The flaring magnitudes are large in some states, which constitute problems with energy waste and CO2 emissions. In North Dakota, operators are required to estimate and report the volume flared. The questions are, how good is the quality of this reporting, and what insights can be drawn from it? Apart from the company-reported statistics, which are available from the North Dakota Industrial Commission (NDIC), flared volumes can be estimated via satellite remote sensing, serving as an unbiased benchmark. Since interpretation of the Landsat 8 imagery is hindered by artifacts due to glow, the estimated volumes based on the Visible Infrared Imaging Radiometer Suite (VIIRS) are used. Reverse geocoding is performed for comparing and contrasting the NDIC and VIIRS data at different levels, such as county and oilfield. With all the data gathered and preprocessed, Bayesian learning implemented by MCMC methods is performed to address three problems: county level model development, flaring time series analytics, and distribution estimation. First, there is heterogeneity among the different counties, in the associations between the NDIC and VIIRS volumes. In light of such, models are developed for each county by exploiting hierarchical models. Second, the flaring time series, albeit noisy, contains information regarding trends and patterns, which provide some insights into operator approaches. Gaussian processes are found to be effective in many different pattern recognition scenarios. Third, distributional insights are obtained through unsupervised learning. The negative binomial and GMMs are found to effectively describe the oilfield flare count and flared volume distributions, respectively. Finally, a nearest-neighbor-based approach for operator level monitoring and analytics is introduced.

0 citations0 reviewsNo code linkedOpen access
preprint2022arXiv

Should univariate Cox regression be used for feature selection with respect to time-to-event outcomes?

IMPORTANCE: Time-to-event outcomes are commonly used in clinical trials and biomarker discovery studies and have been primarily analyzed using Cox proportional hazards models. But it's unclear which statistical models should be recommended for feature selection tasks when time-to-event outcomes are of the primary interest. OBJECTIVE: To explore if Gaussian regression of log-transformed survival time could outperform Cox proportional hazards models in feature selection. DESIGN: In this simulation study, the true models are multivariate Cox proportional hazards models with 10 covariates. For all feature selection comparisons, it's assumed that only 5 out the 10 true features are observed/measured for all model fitting, along with 5 random noise features. Each sample size and censoring rate scenario is explored using 10,000 simulation datasets. Different statistical models are applied to the same dataset to estimate feature effects. Model performance is compared using sensitivity, specificity, and accuracy of effect size ranking. RESULTS: When features are independent and the true models are multivariate Cox proportional hazards models, Gaussian regression of log-transformed survival time (response variable) with only two covariates outperformed both the univariate Cox proportional hazards model and logistic regression in feature selection, in terms of not only higher sensitivity, comparable specificity, but also higher accuracy of effect size ranking, regardless of the sample size and censoring rate values. CONCLUSIONS AND RELEVANCE: This study demonstrates the importance of including Gaussian regression of log-transformed survival time in feature selection practice for time-to-event outcomes.

0 citations0 reviewsNo code linkedOpen access
preprint2015arXiv

Resonant Scanning with Large Field of View Reduces Photobleaching and Enhances Fluorescence Yield in STED Microscopy

Photobleaching is a major limitation of superresolution Stimulated Depletion Emission (STED) microscopy. Fast scanning has long been considered an effective means to reduce photobleaching in fluorescence microscopy, but a careful quantitative study of this issue is missing. In this paper, we show that the photobleaching rate in STED microscopy is slowed down and fluorescence yield is enhanced by scanning with high linear speed, enabled by the large field of view in our custom-built resonant-scanning STED microscope. The effect of scanning speed on photobleaching and fluorescence yield is more remarkable at higher levels of depletion laser irradiance, and virtually disappears in conventional confocal microscopy. With a depletion irradiance of >0.2 GW$\cdot$cm$^{-2}$ (time average), we were able to extend the fluorescence survival time of the Atto 647N dye by ~80% with an 8-fold wider field of view. We confirm that STED Photobleaching is primarily caused by the depletion light acting upon the excited fluorophores. Experimental data agree with a theoretical model. Our results encourage further increasing linear scanning speed for photobleaching reduction in STED microscopy.

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

Generating an effective magnetic lattice for cold atoms

We present a general scheme for synthesizing a spatially periodic magnetic field, or a magnetic lattice (ML), for ultracold atoms using pulsed gradient magnetic fields. Both the period and the depth of the artificial ML can be tuned, immune to atomic spontaneous emission often encountered in optical lattices. The effective Hamiltonian for our 2-dimensional ML has not been discussed previously in condensed matter physics. Its band structures show interesting features which can support topologically nontrivial phases. The technical requirements for implementing our protocol are readily available in today's cold atom experiments. Realization of our proposal will significantly expand the repertoire for quantum simulation with ultracold atoms.

0 citations0 reviewsNo code linkedOpen access
preprint2014arXiv

PT-Symmetry in Non-Hermitian Su-Schrieffer-Heeger model with complex boundary potentials

We study the parity- and time-reversal PT symmetric non-Hermitian Su-Schrieffer-Heeger (SSH) model with two conjugated imaginary potentials $\pm iγ$ at two end sites. The SSH model is known as one of the simplest two-band topological models which has topologically trivial and nontrivial phases. We find that the non-Hermitian terms can lead to different effects on the properties of the eigenvalues spectrum in topologically trivial and nontrivial phases. In the topologically trivial phase, the system undergos an abrupt transition from unbroken PT-symmetry region to spontaneously broken $\mathcal{PT} $-symmetry region at a certain $γ_{c}$, and a second transition occurs at another transition point $γ_{c^{'}}$ when further increasing the strength of the imaginary potential $γ$. But in the topologically nontrivial phase, the zero-mode edge states become unstable for arbitrary nonzero $γ$ and the $\mathcal{PT}$-symmetry of the system is spontaneously broken, which is characterized by the emergence of a pair of conjugated imaginary modes.

0 citations0 reviewsNo code linkedOpen access
preprint2002arXiv

Spin tunneling properties in mesoscopic magnets: effects of a magnetic field

The tunneling of a giant spin at excited levels is studied theoretically in mesoscopic magnets with a magnetic field at an arbitrary angle in the easy plane. Different structures of the tunneling barriers can be generated by the magnetocrystalline anisotropy, the magnitude and the orientation of the field. By calculating the nonvacuum instanton solution explicitly, we obtain the tunnel splittings and the tunneling rates for different angle ranges of the external magnetic field ($θ_{H}=π/2$ and $π/2<θ_{H}<π$). The temperature dependences of the decay rates are clearly shown for each case. It is found that the tunneling rate and the crossover temperature depend on the orientation of the external magnetic field. This feature can be tested with the use of existing experimental techniques.

0 citations0 reviewsNo code linkedOpen access
preprint2001arXiv

Spin-phase interference, coherent superposition, and quantum tunneling at excited levels in nano-antiferromagnets

The spin-phase interference effects are studied analytically in resonant quantum tunneling of the Néel vector between degenerate excited levels in nanometer-scale single-domain antiferromagnets in the absence of an external magnetic field. We consider a model for mesoscopic antiferromagnets with uncompensated excess spins for the more general structure of magnetic anisotropy, such as biaxial, trigonal, tetragonal and hexagonal crystal symmetry. This study provides a nontrivial generalization of the Kramers degeneracy for double-well system to coherently spin tunneling at ground states as well as low-lying excited states in AFM system with $m$-fold rotational symmetry around the $\hat{z}$ axis. The energy level spectrum and the thermodynamic properties of magnetic tunneling states are found to depend significantly on the parity of the excess spins at sufficiently low temperatures. Possible relevance to experiments is also discussed.

0 citations0 reviewsNo code linkedOpen access
preprint2000arXiv

Field-dependent quantum nucleation of antiferromagnetic bubbles

The phenomenon of quantum nucleation is studied in a nanometer-scale antiferromagnet with biaxial symmetry in the presence of a magnetic field at an arbitrary angle. Within the instanton approach, we calculate the dependence of the rate of quantum nucleation and the crossover temperature on the orientation and strength of the field for bulk solids and two-dimensional films of antiferromagnets, respectively. Our results show that the rate of quantum nucleation and the crossover temperature from thermal-to-quantum transitions depend on the orientation and strength of the field distinctly, which can be tested with the use of existing experimental techniques.

0 citations0 reviewsNo code linkedOpen access
preprint2000arXiv

Phase interference of spin tunneling in an arbitrarily directed magnetic field

We present an exact analytic study on the topological phase interference effect in resonant quantum tunneling of the magnetization between degenerate excited levels for biaxial ferromagnets in an arbitrarily directed magnetic field. We show that the topological phase interference effect depends on the orientation of the field distinctly. The transition from classical to quantum behavior is also discussed.

0 citations0 reviewsNo code linkedOpen access
preprint2000arXiv

Resonant quantum coherence of magnetization at excited states in nanospin systems with different crystal symmetries

The quantum interference effects induced by the Wess-Zumino term, or Berry phase are studied theoretically in resonant quantum coherence of magnetization vector between degenerate excited states in nanometer-scale single-domain ferromagnets in the absence of an external magnetic field. By applying the periodic instanton method in the spin-coherent-state path integral, we evaluate the low-lying tunnel splittings between degenerate excited states of neighboring wells. And the low-lying energy level spectrum of m-th excited states are obtained with the help of the Bloch theorem in one-dimensional periodic potential.

0 citations0 reviewsNo code linkedOpen access