arXiv subjects

Daniele Notarmuzi

Publications and source records attributed to Daniele Notarmuzi.

10 recordsLinked to original sources

arXiv2026

A fast algorithm for 2D Rigidity Percolation

Rigidity Percolation is a crucial framework for describing rigidity transitions in amorphous systems. We present a new, efficient algorithm to study central-force Rigidity Percolation in two dimensions. This algorithm combines the Pebble Game algorithm, the Newman-Ziff approach to Connectivity Percolation, as well as novel rigorous results in rigidity theory, to exactly identify rigid clusters over the full bond concentration range, in a time that scales as $N^{1.02}$ for a system of $N$ nodes. We perform extensive numerical simulations with systems larger than $500$ million nodes, far beyond the previous limitations. We obtain new, precise estimates for the critical exponents, $ν=1.1694(8)$ and $D_f=1.8423(7)$, and locate the critical threshold at $p_c = 0.6602741(4)$. Besides opening the way to further accurate numerical studies of Rigidity Percolation, our work provides new rigorous theoretical insights on specific cluster merging mechanisms that distinguish it from the standard Connectivity Percolation problem.

cond-mat.soft↗

arXiv2025

Dynamics of a Bottom-Heavy Janus Particle Near a Wall Under Shear Flow

After our attention was brought to recent work by Pelargonio and Zaconne regarding the deviation of the white noise function for systems at very large shear, we have included the work as a reference of interest to our readers and clarified the definition of our Peclet number with respect to the Brownian diffusion of the particle as well as included a brief discussion of the magnitude of our shear rate compared to the bath frequency to clarify that the standard white noise applies in our system.

cond-mat.soft↗

arXiv2025

Simulating inverse patchy colloid models

Nano- to micro-sized particles with differently charged surface areas exhibit complex interaction patterns, characterized by both opposite-charge attraction and like-charge repulsion. While several successful models have been proposed in the literature to describe directional attraction, models accounting for both directional attraction and directional repulsion are much less numerous and often tailored to specific microscopic systems. Here we present a simple and versatile patchy model, where the interaction energy of a pair of particles is a sum of interactions between sites of different types located within the particle volume. We implement different formulations of this model in both a self-developed Monte Carlo code and the widely used LAMMPS Molecular Dynamics simulation software, providing basic toolkits for both simulation methods and, in the latter case, for different algorithms. By comparing physical observables and code performances, we discuss the different models, methods, and algorithms, offering insights into optimization strategies and tricks of trade.

cond-mat.soft↗

arXiv2024

Features of heterogeneously charged systems at their liquid-liquid critical point

Recently synthesized colloids and biological systems such as proteins, viruses and monoclonal antibodies are heterogeneously charged, i.e., different regions of their surfaces carry different amount of positive or negative charge. Because of charge anisotropy, the electrostatics interactions between these units through the surrounding medium are intristically anisotropic, meaning that they are characterized not only by the attraction between oppositely-charged regions but also by the repulsion between like-charged areas. Recent experiments have shown that the liquid-liquid phase separation of these systems can be driven by anisotropic electrostatics interactions, but it is not clear how the emerging aggregates are affected by charge imbalance and charge patchiness. The ability to experimentally control these two quantities calls for a theoretical understanding of their interplay, which we address here at the critical point. We consider a coarse grained model of anisotropically charged hard spheres whose interaction potential is grounded in a robust mean field theory and perform extensive numerical Monte Carlo simulations to understand the aggregation behavior of these units at the critical point. Stemming from the simplicity of the model, we address the interplay between charge imbalance and charge patchiness with the use of three parameters only and fully rationalize how these features impact the critical point of the model by means of thermodynamic-independent pair properties.

physics.comp-ph↗

arXiv2024

Liquid-liquid phase separation driven by charge heterogeneity

Globular proteins as well as recently synthesized colloids engineered with differently charged surface regions have in common a reduced bonding valence and a complex interaction pattern dominated by like-charge attraction and opposite-charge repulsion. While the impact of low functionality on the condensation of the liquid phase has been extensively studied, the combined effect of limited bonding valence and particle charge heterogeneity on the liquid-liquid phase separation has not been investigated yet. We numerically tackle this challenge in a systematic fashion by taking advantage of an efficient coarse-grained model grounded into a robust mean-field description. We consider a relatively simple surface pattern consisting of two charged polar caps and an oppositely charged equatorial belt and investigate how the interplay between geometry and electrostatics affect the critical point parameters. We find that electrostatics has a dramatic effect on the condensation of the liquid phase -- especially in the regime of large polar caps.

cond-mat.soft↗

arXiv2023

Critical avalanches of Susceptible-Infected-Susceptible dynamics in finite networks

We investigate the avalanche temporal statistics of the Susceptible-Infected-Susceptible (SIS) model when the dynamics is critical and takes place on finite random networks. By considering numerical simulations on annealed topologies we show that the survival probability always exhibits three distinct dynamical regimes. Size-dependent crossover timescales separating them scale differently for homogeneous and for heterogeneous networks. The phenomenology can be qualitatively understood based on known features of the SIS dynamics on networks. A fully quantitative approach based on Langevin theory is shown to perfectly reproduce the results for homogeneous networks, while failing in the heterogeneous case. The analysis is extended to quenched random networks, which behave in agreement with the annealed case for strongly homogeneous and strongly heterogeneous networks.

cond-mat.stat-mech↗

arXiv2021

Universality, criticality and complexity of information propagation in social media

Information avalanches in social media are typically studied in a similar fashion as avalanches of neuronal activity in the brain. Whereas a large body of literature reveals substantial agreement about the existence of a unique process characterizing neuronal activity across organisms, the dynamics of information in online social media is far less understood. Statistical laws of information avalanches are found in previous studies to be not robust across systems, and radically different processes are used to represent plausible driving mechanisms for information propagation. Here, we analyze almost 1 billion time-stamped events collected from a multitude of online platforms -- including Telegram, Twitter and Weibo -- over observation windows longer than 10 years to show that the propagation of information in social media is a universal and critical process. Universality arises from the observation of identical macroscopic patterns across platforms, irrespective of the details of the specific system at hand. Critical behavior is deduced from the power-law distributions, and corresponding hyperscaling relations, characterizing size and duration of avalanches of information. Neuronal activity may be modeled as a simple contagion process, where only a single exposure to activity may be sufficient for its diffusion. On the contrary, statistical testing on our data indicates that a mixture of simple and complex contagion, where involvement of an individual requires exposure from multiple acquaintances, characterizes the propagation of information in social media. We show that the complexity of the process is correlated with the semantic content of the information that is propagated. Conversational topics about music, movies and TV shows tend to propagate as simple contagion processes, whereas controversial discussions on political/societal themes obey the rules of complex contagion.

physics.soc-ph↗

arXiv2021

Percolation theory of self-exciting temporal processes

We investigate how the properties of inhomogeneous patterns of activity, appearing in many natural and social phenomena, depend on the temporal resolution used to define individual bursts of activity. To this end, we consider time series of microscopic events produced by a self-exciting Hawkes process, and leverage a percolation framework to study the formation of macroscopic bursts of activity as a function of the resolution parameter. We find that the very same process may result in different distributions of avalanche size and duration, which are understood in terms of the competition between the 1D percolation and the branching process universality class. Pure regimes for the individual classes are observed at specific values of the resolution parameter corresponding to the critical points of the percolation diagram. A regime of crossover characterized by a mixture of the two universal behaviors is observed in a wide region of the diagram. The hybrid scaling appears to be a likely outcome for an analysis of the time series based on a reasonably chosen, but not precisely adjusted, value of the resolution parameter.

physics.soc-ph↗

arXiv2020

Classes of critical avalanche dynamics in complex networks

Dynamical processes exhibiting absorbing states are essential in the modeling of a large variety of situations from material science to epidemiology and social sciences. Such processes exhibit the possibility of avalanching behavior upon slow driving. Here, we study the distribution of sizes and durations of avalanches for well-known dynamical processes on complex networks. We find that all analyzed models display a similar critical behavior, characterized by the presence of two distinct regimes. At small scales, sizes and durations of avalanches exhibit distributions that are dependent on the network topology and the model dynamics. At asymptotically large scales instead -- irrespective of the type of dynamics and of the topology of the underlying network -- sizes and durations of avalanches are characterized by power-law distributions with the exponents of the standard mean-field critical branching process.

physics.soc-ph↗

arXiv2018

Analytical study of quality-biased competition dynamics for memes in social media

The spreading of news, memes and other pieces of information occurring via online social platforms has a strong and growing impact on our modern societies, with enormous consequences, that may be beneficial but also catastrophic. In this work we consider a recently introduced model for information diffusion in social media taking explicitly into account the competition of a large number of items of diverse quality. We map the meme dynamics onto a one-dimensional diffusion process that we solve analytically, deriving the lifetime and popularity distributions of individual memes. We also present a mean-field type of approach that reproduces the average stationary properties of the dynamics. In this way we understand and control the role of the different ingredients of the model, opening the path for the inclusion of additional, more realistic, features.

physics.soc-ph↗