Lucio Santi

@article{lanzarotti_multi-scale_2025,

title = {A multi-scale agent-based model of aerosol-mediated indoor infections in heterogeneous scenarios},

author = {Esteban Lanzarotti and Andrea Pineda Rojas and Francisco Roslan and Leandro Groisman and Lucio Santi and Rodrigo Castro},

url = {https://doi.org/10.1080/17477778.2025.2476456},

doi = {10.1080/17477778.2025.2476456},

issn = {1747-7778},

year  = {2025},

date = {2025-01-01},

urldate = {2025-07-01},

journal = {Journal of Simulation},

volume = {0},

number = {0},

pages = {1–19},

abstract = {We present a hybrid agent-based and equation-based simulation model to study airborne infection transmission events in heterogeneous indoor spaces. Agents move between different rooms, generating evolving networked social interactions. Suspended aerosols enable both direct and indirect transmission, shaping multi-scale contagion at local (room) and global (building layout) levels within a SEIR process. This approach provides a very flexible platform for dealing with environmental and population heterogeneities. Our model reproduces well-documented real-world contagion events and analytical models in the literature over a wide range of environments (hospitals, offices, restaurants, and classrooms). The model is applied to study transmission patterns in a typical school day, exploring three heterogeneity-driven scenarios: (i) varying break-time activity intensity, (ii) localized ventilation reductions, and (iii) flexible class/break durations, uncovering emerging nonlinear system-level dynamics. Our results show that neglecting heterogeneities can lead to considerable underestimation of attack rates. Such scenarios cannot be modeled with previous agent-based frameworks.},

note = {Publisher: Taylor & Francis 

_eprint: https://doi.org/10.1080/17477778.2025.2476456},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{santi_retqss_2022,

title = {retQSS: A novel methodology for efficient modeling and simulation of particle systems in reticulated geometries},

author = {Lucio Santi and Joaquín Fernández and Ernesto Kofman and Rodrigo Castro},

doi = {10.1016/J.CPC.2021.108157},

issn = {0010-4655},

year  = {2022},

date = {2022-01-01},

journal = {Computer Physics Communications},

volume = {270},

pages = {108157},

abstract = {This work presents retQSS, a novel methodology for efficient modeling and simulation of particle systems in reticulated meshed geometries. On the simulation side, retQSS profits from the discrete-event nature of Quantized State System (QSS) methods, which enable efficient particle tracking algorithms that are agnostic of the application domain. On the modeling side, retQSS relies on the standardized Modelica modeling language, yielding compact and elegant specifications of hybrid (continuous/discrete) dynamic systems. Combined together, these features offer a sound, general-purpose framework for modeling and simulation of particle systems. We show how the state-events that arise when particles interact with a reticulated mesh are seamlessly translated into easily tractable time-events. The latter can substantially improve simulation performance in scenarios where discontinuities dominate the computational demand. We showcase the flexibility of our approach by addressing four case studies arising from different application domains. Performance studies revealed that retQSS can perform similarly to, and even outperform, well-known domain-specific particle simulation toolkits while offering a clear and sound accuracy control interface.},

note = {Publisher: North-Holland},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{santi_efficient_2021,

title = {Efficient discrete-event based particle tracking simulation for high energy physics},

author = {Lucio Santi and Lucas Rossi and Rodrigo Castro},

doi = {10.1016/j.cpc.2020.107619},

issn = {00104655},

year  = {2021},

date = {2021-01-01},

journal = {Computer Physics Communications},

volume = {258},

abstract = {This work presents novel discrete event-based simulation algorithms based on the Quantized State System (QSS) numerical methods. QSS provides attractive features for particle transportation processes, in particular a very efficient handling of discontinuities in the simulation of continuous systems. We focus on High Energy Physics (HEP) particle tracking applications that typically rely on discrete time-based methods, and study the advantages of adopting a discrete event-based numerical approach that resolves efficiently the crossing of geometry boundaries by a traveling particle. For this purpose we follow two complementary strategies. First, a new co-simulation technique connects the Geant4 simulation toolkit with a standalone QSS solver. Second, a new native QSS numerical stepper is embedded into Geant4. We compare both approaches against the latest Geant4 default steppers in different HEP setups, including a complex realistic scenario (the CMS particle detector at CERN). Our techniques achieve relevant simulation speedups in a wide range of scenarios, particularly when the intensity of discrete-event handling dominates performance in the solving of the continuous laws of particle motion.},

note = {Publisher: Elsevier B.V.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{santi_gqlink_2018,

title = {GQLink: An implementation of Quantized State Systems (QSS) methods in Geant4},

author = {Lucio Santi and Federico Bergero and Soon Yung Jun and Krzysztof Genser and Daniel Elvira and Rodrigo Castro},

doi = {10.1088/1742-6596/1085/5/052015},

issn = {17426596},

year  = {2018},

date = {2018-01-01},

journal = {Journal of Physics: Conference Series},

volume = {1085},

number = {5},

abstract = {Simulations in high energy physics (HEP) often require the numerical solution of ordinary differential equations (ODE) to determine the trajectories of charged particles in a magnetic field when particles move throughout detector volumes. Each crossing of a volume interrupts the underlying numerical method that solves the equations of motion, triggering iterative algorithms to estimate the intersection point within a given accuracy. The computational cost of this procedure can grow significantly depending on the application at hand. Quantized State System (QSS) is a recent family of discrete-event driven numerical methods exhibiting attractive features for this type of problems, such as native dense output (sequences of polynomial segments updated only by accuracy-driven events) and lightweight detection and handling of volume crossings. In this work we present GQLink, a proof-of-concept integration of QSS with the Geant4 simulation toolkit which stands as an interface for co-simulation that orchestrates robustly and transparently the interaction between the QSS simulation engine and aspects such as geometry definition and physics processes controlled by Geant4. We validate the accuracy and study the performance of the method in simple geometries (subject to intense volume crossing activity) and then in a realistic HEP application using a full CMS detector configuration.},

note = {Publisher: IOP Publishing Ltd},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{santi_co-simulation_2018,

title = {A Co-simulation technique for efficient particle tracking using hybrid numerical methods with application in high energy physics},

author = {Lucio Santi and Rodrigo Castro},

doi = {10.1109/WSC.2018.8632200},

issn = {08917736},

year  = {2018},

date = {2018-01-01},

journal = {Proceedings - Winter Simulation Conference},

volume = {2018-Decem},

pages = {1322–1333},

abstract = {Particle tracking in physical systems is a well known simulation challenge in many domains. In particular, High Energy Physics (HEP) demand efficient simulations of charged particles moving throughout complex detector geometries in a magnetic field. Quantized State Systems (QSS) is a modern family of hybrid numerical methods that provides attractive performance features for these problems. Its state-of-the-art implementation is the general-purpose QSS Solver toolkit. Meanwhile, Geant4 is the most widely used platform for computational particle physics, embedding vast amounts of physics domain knowledge. Yet, Geant4 relies rigidly on classic discrete time numerical methods. In this work we present a robust co-simulation technique to apply QSS in the simulation of HEP experiments, thus leveraging the best of both toolkits. We obtained speedups of up to three times in synthetic, yet representative scenarios, and a competitive performance in a difficult benchmark modeled after the Compact Muon Solenoid (CMS) particle detector at CERN.},

note = {ISBN: 9781538665725 

Publisher: Institute of Electrical and Electronics Engineers Inc.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{santi_application_2017,

title = {Application of State Quantization-Based Methods in HEP Particle Transport Simulation},

author = {Lucio Santi and Nicolás Ponieman and Soon Yung Jun and Krzysztof Genser and Daniel Elvira and Rodrigo Castro},

doi = {10.1088/1742-6596/898/4/042049},

issn = {17426596},

year  = {2017},

date = {2017-01-01},

journal = {Journal of Physics: Conference Series},

volume = {898},

number = {4},

abstract = {Simulation of particle-matter interactions in complex geometries is one of the main tasks in high energy physics (HEP) research. An essential aspect of it is an accurate and efficient particle transportation in a non-uniform magnetic field, which includes the handling of volume crossings within a predefined 3D geometry. Quantized State Systems (QSS) is a family of numerical methods that provides attractive features for particle transportation processes, such as dense output (sequences of polynomial segments changing only according to accuracy-driven discrete events) and lightweight detection and handling of volume crossings (based on simple root-finding of polynomial functions). In this work we present a proof-of-concept performance comparison between a QSS-based standalone numerical solver and an application based on the Geant4 simulation toolkit, with its default Runge-Kutta based adaptive step method. In a case study with a charged particle circulating in a vacuum (with interactions with matter turned off), in a uniform magnetic field, and crossing up to 200 volume boundaries twice per turn, simulation results showed speedups of up to 6 times in favor of QSS while it being 10 times slower in the case with zero volume boundaries.},

note = {Publisher: Institute of Physics Publishing},

keywords = {},

pubstate = {published},

tppubtype = {article}

}