arXiv subjects

Minwoo Bae

Publications and source records attributed to Minwoo Bae.

5 recordsLinked to original sources

arXiv2026

Criticality of nonreciprocal phase oscillators with long-range interactions

We study noisy identical Kuramoto-Sakaguchi oscillators with phase lag $\alpha\in[0,\pi/2)$, where $\alpha>0$ induces nonreciprocal interactions. Numerical phase diagrams in the $(\sigma, \alpha)$ plane in fully-connected graphs, formed by long-range weights tuned by $\sigma$ on $d$-dimensional lattices, reveal a critical phase lag $\alpha_c$, below which spontaneous synchronization occurs. This critical phase lag decreases monotonically with $\sigma$. We characterize the critical behavior analytically using the dynamical renormalization group theory.

nlin.AO↗

arXiv2025

Controlling sternness in judging a good person who helps the bad

Recent studies on indirect reciprocity with private assessment on complete graphs suggest the possibility that one can continuously modulate the degree of segregation by controlling how to judge a good person helping a bad one. A well-known social norm called L6 judges it as bad, which eventually segregates the society into two antagonistic clusters, but if it is judged as good, the system reaches paradise where everyone likes each other. In this work, we numerically study this transition between segregation and paradise in two different settings. Firstly, in a uniform population of size $N$ where everyone regards such a donor as good with probability $p$ and bad with $1-p$, we observe paradise when $Np$ is sufficiently greater than $O(1)$. In contrast, in a heterogeneous setting where only $k$ individuals judge such a donor as good, the size difference of the clusters increases almost linearly as $k$ increases, so paradise can only be reached as $k \to N$ in a large population. Therefore, when an urgent change is needed to overcome the segregation due to L6, a small change in each and every individual's behavior is more efficient than a radical change in a fraction of the population.

physics.soc-ph↗

arXiv2025

Indirect reciprocity as a dynamics for weak balance

A social network is often divided into many factions. People are friends within each faction, while they are enemies of the other factions, and even my enemy's enemy is not necessarily my friend. This configuration can be described in terms of a weak form of structural balance. Although weak balance explains a number of real social networks, which dynamical rule achieves it has remained relatively unexplored. In this work, we show that the answer can be found in the field of indirect reciprocity, which assumes that people assess each other's behavior and choose how to behave to others based on the assessment according to a social norm. We begin by showing that weak structural balance is equivalent to stationarity when the rule is given by a norm called `judging'. By analyzing its cluster dynamics of merging, fission, and migration induced by assessment error in complete graphs, we obtain the cluster size distribution in a steady state, which shows the coexistence of a giant cluster and smaller ones. This study suggests that indirect reciprocity can provide insight into the interplay between a norm that individuals abide by and the macroscopic group structure in society.

physics.soc-ph↗

arXiv2024

Exact cluster dynamics of indirect reciprocity in complete graphs

Heider's balance theory emphasizes cognitive consistency in assessing others, as is expressed by ``The enemy of my enemy is my friend.'' At the same time, the theory of indirect reciprocity provides us with a dynamical framework to study how to assess others based on their actions as well as how to act toward them based on the assessments. Well known are the ``leading eight'' from L1 to L8, the eight norms for assessment and action to foster cooperation in social dilemmas while resisting the invasion of mutant norms prescribing alternative actions. In this work, we begin by showing that balance is equivalent to stationarity of dynamics only for L4 and L6 (stern judging) among the leading eight. Stern judging reflects an intuitive idea that good merits reward whereas evil warrants punishment. By analyzing the dynamics of Stern Judging in complete graphs, we prove that this norm almost always segregates the graph into two mutually hostile groups as the graph size grows. We then compare L4 with stern judging: The only difference of L4 is that a good player's cooperative action toward a bad one is regarded as good. This subtle difference transforms large populations governed by L4 to a ``paradise'' where cooperation prevails and positive assessments abound. Our study thus helps us understand the relationship between individual norms and their emergent consequences at a population level, shedding light on the nuanced interplay between cognitive consistency and segregation dynamics.

physics.soc-ph↗

arXiv2021

Source Independent Quantum Walk Random Number Generation

Source independent quantum random number generators (SI-QRNG) are cryptographic protocols which attempt to extract random strings from quantum sources where the source is under the control of an adversary while the measurement devices are fully characterized. This represents a middle-ground between fully-trusted and full-device independence, allowing for fast bit-generation rates with current-day technology, while also providing a strong security guarantee. In this paper we analyze an SI-QRNG protocol based on quantum walks and develop a new proof technique to show security.

quant-ph↗