Physica A 389 (2010) 2637–2641
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Physica A
journal homepage: www.elsevier.com/locate/physa
Stretched exponential distribution of recurrent time of wars in China
Da-Hai Tang
a,∗
, Xiao-Pu Han
a
, Bing-Hong Wang
a,b
a
Department of Modern Physics, University of Science and Technology of China, Hefei Anhui, 230026, PR China
b
Institute of Complex Adaptive System, Shanghai Academy of System Science, Shanghai, PR China
a r t i c l e i n f o
Article history:
Received 7 October 2009
Received in revised form 4 January 2010
Available online 20 March 2010
Keywords:
Recurrent time distribution
War
Stretched exponential distribution
Non-Poisson property
Self-organized criticality
a b s t r a c t
As a killing machine and a decisive factor of history, wars play an important role in
social system. In this paper, we present an empirical exploration of the distribution of
recurrent time of wars in ancient China and find that it obeys a stretched exponential
form. The pattern we found implies that there are undetected mechanisms that underlie
the dynamics of wars. In order to explain the origin of this form, a model mainly based on
the correlation between two consecutive wars is constructed, which is somewhat similar
to the Bak–Sneppen model. The simulation results of the model are in agreement with the
empirical statistics and suggest that the dynamics of wars could relate with self-organized
criticality.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
How to understand the nature and origin of wars (conflicts) are important questions of some government management
departments and many disciplines of modern science, such as history, psychology, military and sociology. It is obvious that
wars relate with not only the past of the history, but also the future. By applying their own tools, the researchers of these
disciplines have made great achievements in almost every respect of wars: the origin of wars, evaluating wars’ influence
on society, the emergency management of conflicts, and so on. But, these researchers always unconsciously treat the war
as a single special event that can be separated from other wars, and do not pay any more attention to probe the dynamic
patterns beneath the surface of these human collective activities (wars). Then regularities in the dynamics of wars still are
not sufficiently understood. The works of Richardson and D.C. Roberts – in the 1960s, Richardson found that the frequency
versus size of wars display power law type [1], further, D.C. Roberts points out that this power law is generated by self-
organized criticality (SOC) [2], and the war can been described by the forest fire model [3] – are an excellent start that tries
to ignore the particularity of wars and theoretically explain wars for a universal principle (SOC).
Recently, through studying the timing of human activities, human dynamics [4–7], which is dedicated to finding out the
dynamics rules in human activities, have made great progress. Given the number of factors that determine the timing of
each action, ranging from work and sleep patterns to resource availability, it seems impossible to seek regularities in human
dynamics, apart from the obvious daily and seasonal periodicity. By studying the recurrent time distribution, the researchers
find that, beneath the diversity of human daily activities, there is the existence of rational decision driving human activities:
priority-based decision [4]. Then, the phenomenon that is irrelevant on the surface is unified.
Similar to a variety of factors that determine the timing of human activities, the causes of wars (conflicts) are also various:
the government’s cruel rule, foreign invasion, natural disasters, and so on. For example, while suffering serious natural
disasters, the peasants who still have to bear heavy taxes could fight with the rulers for survival, then maybe a series of wars
will be made. The traditional questions asked for understanding wars are always: who (and why) made the war, what (and
∗
Corresponding author.
E-mail addresses: tangdahai@mail.ustc.edu.cn (D.-H. Tang), bhwang@ustc.edu.cn (B.-H. Wang).
0378-4371/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.physa.2010.03.012