Quantitative understanding of human behaviors provides elementary
comprehension of the complexity of many human-initiated systems. In this paper,
we investigate the behavior of people on the $BBS$ forum by the statistical
analysis of the amounts of view and reply of posts. According to our
statistics, we find that the amounts of view and reply of posts follow the
power law distributions with different power exponent. Furthermore, we discover
that the amounts of view and reply of posts have nonlinear relationship. They
are related by power function and show us straight line in log-log plot. Based
on the estimation of slope and intercept of the line, we can characterize the
behaviors quantitatively and know that people of Chinese forum and those of
foreign forum have different preference towards replying to and viewing the
posts. At last, we analyze the burstiness and memory in replying time series.
They show some universal properties among different forum. All of them locate
themselves in the high-$B$, low-$M$ region.
Using open source data, we observe the fascinating dynamics of nighttime
light. Following a global economic regime shift, the planetary center of light
can be seen moving eastwards at a pace of about 60 km per year. Introducing
spatial light Gini coefficients, we find a universal pattern of human
settlements across different countries and see a global centralization of
light. Observing 160 different countries we document the expansion of
developing countries, the growth of new agglomerations, the regression in
countries suffering from demographic decline and the success of light pollution
abatement programs in western countries.
Economists are fond of the physicists’ powerful tools. As a popular mindset
Toolism is as old as economics but the transplants failed to produce the same
successes as in their aboriginal environment. Economists therefore looked
more and more to the math department for inspiration. Now the tide turns
again. The ongoing crisis discredits standard economics and offers the chance
for a comeback. Modern econophysics commands the most powerful tools
and argues that there are many occasions for their application. The present
paper argues that it is not a change of tools that is most urgently needed but a
paradigm change.
In this paper we argue that if we want to find a more satisfactory approach to tackling the major socio-economic problems we are facing, we need to thoroughly rethink the basic assumptions of macroeconomics and financial theory. Making minor modifications to the standard models to remove "imperfections" is not enough, the whole framework needs to be revisited.
The question on the title came through my mind one day as I keep in one hand a paper in nuclear physics and in the other hand a paper in finance and surprisingly conclude that the same formula appear in both articles*. Phenomena from apparently completely different field of research were solved with the help of same equation. Things are getting even weirder saying that the formula I was talking about is the time-independent Schrodinger equation.
The following fundamental properties are proved to be true if a financial
market is exhaustive: (i) Every event which is measurable by the price history
at time T is independent of G_t conditional on the current price history H_t,
where G_t is a superset of H_t, (ii) every event which is measurable by G_t is
independent of H_T conditional on H_t. These properties are especially useful
for asset valuation, portfolio optimization and risk management. An exhaustive
market with respect to {F_t} is free of dominance and there are no free lunches
with vanishing risk under {F_t}. Moreover, it is complete with respect to every
information flow which is contained in {F_t} and the growth-optimal portfolio
at time t is only determined by the past asset prices. This means any other
information which is contained in F_t and available to the investor at time t
is irrelevant.
We study a subset of the movie collaboration network, imdb.com, where only
adult movies are included. We show that there are many benefits in using such a
network, which can serve as a prototype for studying social interactions. We
find that the strength of links, i.e., how many times two actors have
collaborated with each other, is an important factor that can significantly
influence the network topology. We see that when we link all actors in the same
movie with each other, the network becomes small-world, lacking a proper
modular structure. On the other hand, by imposing a threshold on the minimum
number of links two actors should have to be in our studied subset, the network
topology becomes naturally fractal. This occurs due to a large number of
meaningless links, namely, links connecting actors that did not actually
interact. We focus our analysis on the fractal and modular properties of this
resulting network, and show that the renormalization group analysis can
characterize the self-similar structure of these networks.
The increasing interdependencies between the world’s technological, socio-economic, and environmental systems have the potential to create global catastrophic risks. We may have to re-design many global networks, otherwise they could turn into "global time bombs".
We present and discuss a stochastic model of financial assets dynamics based
on the idea of an inverse renormalization group strategy. With this strategy we
construct the multivariate distributions of elementary returns based on the
scaling with time of the probability density of their aggregates. In its
simplest version the model is the product of an endogenous auto-regressive
component and a random rescaling factor embodying exogenous influences.
Mathematical properties like increments' stationarity and ergodicity can be
proven. Thanks to the relatively low number of parameters, model calibration
can be conveniently based on a method of moments, as exemplified in the case of
historical data of the S&P500 index. The calibrated model accounts very well
for many stylized facts, like volatility clustering, power law decay of the
volatility autocorrelation function, and multiscaling with time of the
aggregated return distribution. In agreement with empirical evidence in
finance, the dynamics is not invariant under time reversal and, with suitable
generalizations, skewness of the return distribution and leverage effects can
be included. The analytical tractability of the model opens interesting
perspectives for applications, for instance in terms of obtaining closed
formulas for derivative pricing. Further important features are: The
possibility of making contact, in certain limits, with auto-regressive models
widely used in finance; The possibility of partially resolving the endogenous
and exogenous components of the volatility, with consistent results when
applied to historical series.
The advancement of various fields of science depends on the actions of
individual scientists via the peer review process. The referees' work patterns
and stochastic nature of decision making both relate to the particular features
of refereeing and to the universal aspects of human behavior. Here, we show
that the time a referee takes to write a report on a scientific manuscript
depends on the final verdict. The data is compared to a model, where the review
takes place in an ongoing competition of completing an important composite task
with a large number of concurrent ones - a Deadline -effect. In peer review
human decision making and task completion combine both long-range
predictability and stochastic variation due to a large degree of ever-changing
external "friction".