Searcharxiv⌕ Search

arXiv subjects

Pawel Sobkowicz

Publications and source records attributed to Pawel Sobkowicz.

At least 19 recordsLinked to original sources
arXiv2025

Exploring the impact of Ti/Al on L12 nanoprecipitation and deformation behavior in CoNiFeAlTi multi-principal element alloys through atomistic simulations

Recent studies on CoNi-based multi-principal element alloys (MPEAs) have demonstrated high strength and ductility, attributed to the formation of stable L12 nanoscale precipitates. However, the fundamental mechanisms behind such impressive properties in these complex alloys are not well understood. In this work, we investigate the effects of Ti and Al concentrations on the formation of L12 precipitates in (CoNiFe)84(Al8Ti8), (CoNiFe)86(Al7Ti7), (CoNiFe)88(Al6Ti6), and (CoNiFe)94(Al4Ti2) MPEAs using hybrid molecular dynamics/Monte Carlo (MD/MC) simulations and a MEAM interatomic potential for the CoNiFeTiAl system. Additionally, we study the effect of L12 precipitation on the mechanical properties and stacking fault energy (SFE) of these MPEAs using MD. Our hybrid MD/MC simulations show that the (CoNiFe)86(Al7Ti7) alloy exhibits the highest amount of L12 nanoprecipitates. We find that L12 precipitation increases the SFE, with higher Al and Ti contents leading to greater increases. Tensile simulations reveal that L12 precipitates enhance yield strength, with alloys exhibiting higher precipitation showing increased flow stress. We also investigate dislocation-nanoprecipitate interactions with different precipitate sizes in the (CoNiFe)86(Al7Ti7) alloy. Larger nanoprecipitate sizes result in stronger dislocation pinning. Dislocations predominantly shear through 4-8 nm precipitates instead of looping around them (Orowan mechanism), enhancing strength while maintaining good ductility. Although the lattice mismatch between the L12 nanoprecipitate and the matrix is low (0.139%), the significant difference in SFE between the L12 nanoprecipitate and the matrix results in stronger dislocation pinning. This understanding can guide the design of MPEAs with tailored properties by controlling nanoscale precipitation.

cond-mat.mtrl-sci↗
arXiv2023

Quasi-localized modes in crystalline high entropy alloys

High Entropy Alloys (HEAs) are designed by mixing multiple metallic species in nearly the same amount to obtain crystalline or amorphous materials with exceptional mechanical properties. Here we use molecular dynamics simulations to investigate the role of positional and compositional disorder in determining the low-frequency vibrational properties of CrMnFeCoNi HEAs. Our results show that the expected dependence of the density of states on the frequency as $D(ω)\simω^4$ is recovered for amorphous HEAs and is also observed for partially crystallized alloys with deviations that depend on the degree of crystallization. We find that the quasi-localized vibrations are still visible in crystalline HEAs, albeit suppressed compared to the corresponding amorphous alloys. Our work offers a unified perspective to describe HEA mechanical properties in terms of their vibrational density of states.

cond-mat.dis-nn↗
arXiv2022

Dislocation plasticity in equiatomic NiCoCr alloys: The effect of short-range order

Equiatomic NiCoCr solid solutions have been recently shown to display exceptional mechanical properties, that have been suggested to be linked to nanostructural short-range order (SRO) features that may arise from thermal treatments, such as annealing or/and aging. Here, we use hybrid Monte Carlo-Molecular Dynamics simulations to gain further insights of thermal effects on the SRO formation as well as the edge dislocation plasticity mechanisms of equiatomic NiCoCr face-centered cubic solid solution. For that purpose, we utilize two well-known NiCoCr interatomic potentials, one of which displays well documented SRO, believed to be linked to experimental evidence and labeled as the Li-Sheng-Ma potential, while the other (Farkas-Caro) does not. We use these two potentials to discern short range ordering (from inherent randomness in random solid solutions) and understand how SROs influence dislocation depinning dynamics in various thermal annealing scenarios. In this context, we used robust, scale-dependent metrics to infer a characteristic SRO size in the Li-Sheng-Ma case by probing local concentration fluctuations which otherwise indicate uncorrelated patterns in the Farkas-Caro case in a close agreement with random alloys. Using relevant order parameters, we also report on the drastic increase of chemical ordering within the stacking fault region. More importantly, we find that the Li-Sheng-Ma potential leads to excellent edge dislocation depinning strength with low stacking fault width. Our findings indicate an enhanced roughening mechanism due to the SROs-misfit synergy that leads to significant improvements in dislocation glide resistance. We argue that the improvements in alloy strength have their atomistic origins in the interplay between nanoscopic SROs and atomic-level misfit properties.

cond-mat.mtrl-sci↗
arXiv2020

High Entropy Alloys as a new metaphor in sociophysics

Most of the opinion dynamics models in sociophysics have their historic origin in studies two-dimensional magnetization phenomena. This metaphor has proven quite useful, as it allowed to use well known techniques, relating individual behaviours of single spins and their interactions, to large scale properties, such as magnetization or magnetic domains creation. These physical properties were then ``mapped'' to social concepts: spin orientation to a person's views on a specific issue, magnetization to global opinion on the issue, etc. During the past 20 years, the models were significantly expanded, using more complex individual agent characteristics and even more complex types of the interactions, but the power of the metaphor remained unchanged. In the current paper we propose to use a new physical system as the basis for new ideas in sociophysics. We shall argue that the concepts and tools devoted to studies of High Entropy Alloys (HEAs) could significantly broaden the range of social concepts ``addressable'' by sociophysics, by focusing on a wider range of global phenomena, arising from atomic properties, interactions and arrangements. We illustrate the new idea by calculating a few characteristics of a simple HEA system and their possible ``mapping'' into social concepts.

physics.soc-ph↗
arXiv2019

Inequalities, chance and success in sport competitions: simulations vs empirical data

We present a new way of estimation of the role of chance in achieving success, by comparing the empirical data from 100-meter dash competitions (one of the sports disciplines with the most stringent controls of external randomness), with the results of an agent-based computer model, which assumes that success depends jointly on the intrinsic talent of the agent and on unpredictable luck. We find a small, but non-zero contribution of random luck to the performance of the best sprinters, which may serve as a lower bound for the randomness role in other, less stringently controlled competitive domains. Additionally we discuss the perception of the payoff differences among the top participants, and the role of random luck in the resulting inequality.

physics.soc-ph↗
arXiv2017

Opinion dynamics model based on cognitive biases

We present an introduction to a novel model of an individual and group opinion dynamics, taking into account different ways in which different sources of information are filtered due to cognitive biases. The agent based model, using Bayesian updating of the individual belief distribution, is based on the recent psychology work by Dan Kahan. Open nature of the model allows to study the effects of both static and time-dependent biases and information processing filters. In particular, the paper compares the effects of two important psychological mechanisms: the confirmation bias and the politically motivated reasoning. Depending on the effectiveness of the information filtering (agent bias), the agents confronted with an objective information source may either reach a consensus based on the truth, or remain divided despite the evidence. In general, the model might provide an understanding into the increasingly polarized modern societies, especially as it allows mixing of different types of filters: psychological, social, and algorithmic.

physics.soc-ph↗
arXiv2015

Semi-quantitative predictions for the Polish parliamentary elections (October 25, 2015) based on the Emotion/Information/Opinion mode

Based on an agent based model of opinion changes, described in detail in a recent paper (\arXiv:1507.00126), we attempt to predict, three months in advance, the range of possible results of the Polish parliamentary elections, scheduled for October 25, 2015. The model reproduces semi-quantitatively the poll results for the three parties which dominated the recent presidential elections and allows estimation of some variations of the electoral propaganda campaigns by the parties.

physics.soc-ph↗
arXiv2015

Breakdown of metastable political duopoly due to asymmetry of emotions in partisan propaganda

We present results of opinion dynamics simulations based on the emotion/information/opinion (E/I/O) model, applied to a strongly polarized society. Under certain conditions the model leads to metastable coexistence of two subcommunities (supporting each of the opinions) of comparable size -- which corresponds to bipartisan split found in many real world communities. Spurred by the recent breakdown of such system, which existed in Poland for over 9 years, we extend the model by allowing a third opinion. We show that if the propaganda messages of the two incumbent parties differ in emotional tone, the system may be "invaded" by a newcomer third party very quickly -- in qualitative agreement with the actual political situation in Poland in 2015.

physics.soc-ph↗
arXiv2012

Aliens on Earth. Are reports of close encounters correct?

Popular culture (movies, SF literature) and witness accounts of close encounters with extraterrestrials provide a rather bizarre image of Aliens behavior on Earth. It is far from stereotypes of human space exploration. The reported Aliens are not missions of diplomats, scientists nor even invasion fleets; typical encounters are with lone ETs (or small groups), and involve curious behavior: abductions and experiments (often of sexual nature), cattle mutilations, localized killing and mixing in human society using various methods. Standard scientific explanations of these social memes point to influence of cultural artifacts (movies, literature) on social imagination, projection of our fears and observations of human society, and, in severe cases, psychic disorder of the involved individuals. In this work we propose an alternate explanation, claiming that the memes might be the result of observations of actual behavior of true Aliens, who, visiting Earth behave in a way that is then reproduced by such memes. The proposal would solve, in natural way, the Fermi paradox.

physics.pop-ph↗
arXiv2011

Hate networks revisited: time and user interface dependence study of user emotions in political forum

The paper presents analysis of time evolution within am Internet political forum, characterized by large political differences and high levels of emotions. The study compares samples of discussions gathered at three periods separated by important events. We focus on statistical aspects related to emotional content of communication and changes brought by technologies that increase or decrease the direct one-to-one discussions. We discuss implications of user interface aspects on promoting communication across a political divide.

physics.soc-ph↗
arXiv2011

Negative emotions boost users activity at BBC Forum

We present an empirical study of user activity in online BBC discussion forums, measured by the number of posts written by individual debaters and the average sentiment of these posts. Nearly 2.5 million posts from over 18 thousand users were investigated. Scale free distributions were observed for activity in individual discussion threads as well as for overall activity. The number of unique users in a thread normalized by the thread length decays with thread length, suggesting that thread life is sustained by mutual discussions rather than by independent comments. Automatic sentiment analysis shows that most posts contain negative emotions and the most active users in individual threads express predominantly negative sentiments. It follows that the average emotion of longer threads is more negative and that threads can be sustained by negative comments. An agent based computer simulation model has been used to reproduce several essential characteristics of the analyzed system. The model stresses the role of discussions between users, especially emotionally laden quarrels between supporters of opposite opinions, and represents many observed statistics of the forum.

cs.HC↗
arXiv2010

Dynamics of hate based networks

We present a study of the properties of network of political discussions on one of the most popular Polish Internet forums. This provides the opportunity to study the computer mediated human interactions in strongly bipolar environment. The comments of the participants are found to be mostly disagreements, with strong percentage of invective and provocative ones. Binary exchanges (quarrels) play significant role in the network growth and topology. Statistical analysis shows that the growth of the discussions depends on the degree of controversy of the subject and the intensity of personal conflict between the participants. This is in contrast to most previously studied social networks, for example networks of scientific citations, where the nature of the links is much more positive and based on similarity and collaboration rather than opposition and abuse. The work discusses also the implications of the findings for more general studies of consensus formation, where our observations of increased conflict contradict the usual assumptions that interactions between people lead to averaging of opinions and agreement.

physics.soc-ph↗
arXiv2010

Dilbert-Peter model of organization effectiveness: computer simulations

We provide a technical report on a computer simulation of general effectiveness of a hierarchical organization depending on two main aspects: effects of promotion to managerial levels and efforts to self-promote of individual employees, reducing their actual productivity. The combination of judgment by appearance in the promotion to higher levels of hierarchy and the Peter Principle (which states that people are promoted to their level of incompetence) results in fast declines in effectiveness of the organization. The model uses a few synthetic parameters aimed at reproduction of realistic conditions in typical multilayer organizations.

physics.soc-ph↗
arXiv2009

Studies of opinion stability for small dynamic networks with opportunistic agents

There are numerous examples of societies with extremely stable mix of contrasting opinions. We argue that this stability is a result of an interplay between society network topology adjustment and opinion changing processes. To support this position we present a computer model of opinion formation based on some novel assumptions, designed to bring the model closer to social reality. In our model, the agents, in addition to changing their opinions due to influence of the rest of society and external propaganda, have the ability to modify their social network, forming links with agents sharing the same opinions and cutting the links with those they disagree with. To improve the model further we divide the agents into `fanatics' and `opportunists', depending on how easy is to change their opinions. The simulations show significant differences compared to traditional models, where network links are static. In particular, for the dynamical model where inter-agent links are adjustable, the final network structure and opinion distribution is shown to resemble real world observations, such as social structures and persistence of minority groups even when most of the society is against them and the propaganda is strong.

physics.soc-ph↗
arXiv2008

Peer-review in the Internet age

The importance of peer-review in the scientific process can not be overestimated. Yet, due to increasing pressures of research and exponentially growing number of publications the task faced by the referees becomes ever more difficult. We discuss here a few possible improvements that would enable more efficient review of the scientific literature, using the growing Internet connectivity. In particular, a practical automated model for providing the referees with references to papers that might have strong relationship with the work under review, based on general network properties of citations is proposed.

physics.soc-ph↗
arXiv2004

Simulations of assortative matching: complexity of cooperation emergence process

The paper studies the emergence and stability of cooperative behavior in populations of agents who interact among themselves in Prisoner's Dilemma games and who are allowed to choose their partners. The population is then subject to evolutionary pressures, based on individual payoffs from multiple encounters. A simple formula for signaling and recognition is introduced, which allows the agents to guess prospective partner strategy and to refuse the game if the predicted outcome is unfavorable. We present both algebraic formulation of the average payoffs and results of computer simulations of evolution of such society. The simulations result in surprising variety of behavior. We discuss possible interpretations of the results as well as relationship between artificial `computer time' and real time of possible social and biological systems that the model might be applied to.

cond-mat.dis-nn↗
arXiv2003

Effect of leader's strategy on opinion formation in networked societies

The work investigates the influence of leader's strategy on opinion formation in artificial networked societies. The strength of the social influence is assumed to be dictated by distance from one agent to another, as well as individual strengths of the agents. The leader is assumed to have much greater resources, which allows him to tune the way he influences the other agents. We study various strategies of using these resources to optimize the conditions needed to `convince' the whole society to leader's opinion. The flexibility of the model allows it to be used in studies of political, social and marketing influence and opinion formation.

cond-mat.dis-nn↗