745 research outputs found
Model of macroeconomic evolution in stable regionally dependent economic fields
We develop a model for the evolution of economic entities within a
geographical type of framework. On a square symmetry lattice made of three
(economic) regions, firms, described by a scalar fitness, are allowed to move,
adapt, merge or create spin-offs under predetermined rules, in a space and time
dependent economic environment. We only consider here one timely variation of
the ''external economic field condition''. For the firm fitness evolution we
take into account a constraint such that the disappearance of a firm modifies
the fitness of nearest neighboring ones, as in Bak-Sneppen population fitness
evolution model. The concentration of firms, the averaged fitness, the regional
distribution of firms, and fitness for different time moments, the number of
collapsed, merged and new firms as a function of time have been recorded and
are discussed. Also the asymptotic values of the number of firms present in the
three regions together with their average fitness, as well as the number of
respective births and collapses in the three regions are examined. It appears
that a sort of selection pressure exists. A power law dependence,
signature of self-critical organization is seen in the birth and collapse
asymptotic values for a high selection pressure only. A lack of
self-organization is also seen at region borders.Comment: 11 figures double columns on 7 page
Andrzej Pekalski networks of scientific interests with internal degrees of freedom through self-citation analysis
Old and recent theoretical works by Andrzej Pekalski (APE) are recalled as
possible sources of interest for describing network formation and clustering in
complex (scientific) communities, through self-organisation and percolation
processes. Emphasis is placed on APE self-citation network over four decades.
The method is that used for detecting scientists field mobility by focusing on
author's self-citation, co-authorships and article topics networks as in [1,2].
It is shown that APE's self-citation patterns reveal important information on
APE interest for research topics over time as well as APE engagement on
different scientific topics and in different networks of collaboration. Its
interesting complexity results from "degrees of freedom" and external fields
leading to so called internal shock resistance. It is found that APE network of
scientific interests belongs to independent clusters and occurs through rare or
drastic events as in irreversible "preferential attachment processes", similar
to those found in usual mechanics and thermodynamics phase transitions.Comment: 7 pages, 1 table, 44 references, submitted to Int J Mod Phys
Contour lines of the discrete scale invariant rough surfaces
We study the fractal properties of the 2d discrete scale invariant (DSI)
rough surfaces. The contour lines of these rough surfaces show clear DSI. In
the appropriate limit the DSI surfaces converge to the scale invariant rough
surfaces. The fractal properties of the 2d DSI rough surfaces apart from
possessing the discrete scale invariance property follow the properties of the
contour lines of the corresponding scale invariant rough surfaces. We check
this hypothesis by calculating numerous fractal exponents of the contour lines
by using numerical calculations. Apart from calculating the known scaling
exponents some other new fractal exponents are also calculated.Comment: 9 Pages, 12 figure
Magnon-polaron and Spin-polaron Signatures in the Specific Heat and Electrical Resistivity of in Zero Magnetic Field, and the Effect of Bond Environment
, an perovskite manganite oxide,
exhibits a non trivial behavior in the vicinity of the sharp peak found in the
resistivity as a function of temperature in zero magnetic field. The
various features seen on are discussed in terms of competing phase
transitions. They are related to the bond environment depending on
the content of the crystallographic site. A Ginzburg-Landau type theory is
presented for incorporating concurrent phase transitions. The specific heat
of such a compound is also examined from 50 till 200 K. A log-log analysis
indicates different regimes. In the low temperature conducting ferromagnetic
phase, a collective magnon signature () is found as for what
are called magnon-polaron excitations. A law is found at
high temperature and discussed in terms of the fractal dimension of the
conducting network of the weakly conducting (so-called insulating) phase and
Orbach estimate of the excitation spectral behaviors. The need of considering
both independent spin scattering and collective spin scattering is thus
emphasized. The report indicates a remarkable agreement for the Fisher-Langer
formula, i.e. at second order phase transitions. Within
the Attfield model, we find an inverse square root relationship between the
critical temperature(s) and the total local strain.Comment: 19 pages, 5 figures; to be published in Phys Rev
Time dependent correlations in marine stratocumulus cloud base height records
The scaling ranges of time correlations in the cloud base height records of
marine boundary layer stratocumulus are studied applying the Detrended
Fluctuation Analysis statistical method. We have found that time dependent
variations in the evolution of the exponent reflect the diurnal
dynamics of cloud base height fluctuations in the marine boundary layer. In
general, a more stable structure of the boundary layer corresponds to a lower
value of the - indicator, i.e. larger anti-persistence, thus a set of
fluctuations tending to induce a greater stability of the stratocumulus. In
contrast, during periods of higher instability in the marine boundary, less
anti-persistent (more persistent like) behavior of the system drags it out of
equilibrium, corresponding to larger values. From an analysis of the
frequency spectrum, the stratocumulus base height evolution is found to be a
non-stationary process with stationary increments. The occurrence of these
statistics in cloud base height fluctuations suggests the usefulness of similar
studies for the radiation transfer dynamics modeling.Comment: 12 pages, 6 figures; to appear in Int. J. Mod. Phys. C, Vol. 13, No.
2 (2002
Benford’s law predicted digit distribution of aggregated income taxes: the surprising conformity of Italian cities and regions
The yearly aggregated tax income data of all, more than 8000, Italian municipalities are analyzed for a period of five years, from 2007 to 2011, to search for conformity or
not with Benford’s law, a counter-intuitive phenomenon observed in large tabulated data where the occurrence of numbers having smaller initial digits is more favored
than those with larger digits. This is done in anticipation that large deviations from Benford’s law will be found in view of tax evasion supposedly being widespread
across Italy. Contrary to expectations, we show that the overall tax income data for all these years is in excellent agreement with Benford’s law. Furthermore, we also
analyze the data of Calabria, Campania and Sicily, the three Italian regions known for strong presence of mafia, to see if there are any marked deviations from Benford’s
law. Again, we find that all yearly data sets for Calabria and Sicily agree with Benford’s law whereas only the 2007 and 2008 yearly data show departures from the law for Campania. These results are again surprising in view of underground
and illegal nature of economic activities of mafia which significantly contribute totax evasion. Some hypothesis for the found conformity is presented
Data on the annual aggregated income taxes of the Italian municipalities over the quinquennium 2007–2011
This dataset contains the annual aggregated income taxes of all the Italian municipalities over the years 2007-2011. Data are clustered over the Italian regions and provinces. The source of the data is the Italian Ministry of Economics and Finance. The administrative variations in Italy over the quinquennium have been taken into account. Data are useful to understand the economic structure of Italy at the microscopic level of municipalities. They can serve also for making comparisons between economical aspects and other features of the Italian cities
Statistical Dynamics of Religions and Adherents
Religiosity is one of the most important sociological aspects of populations.
All religions may evolve in their beliefs and adapt to the society
developments. A religion is a social variable, like a language or wealth, to be
studied like any other organizational parameter.
Several questions can be raised, as considered in this study: e.g. (i) from a
``macroscopic'' point of view : How many religions exist at a given time? (ii)
from a ``microscopic'' view point: How many adherents belong to one religion?
Does the number of adherents increase or not, and how? No need to say that if
quantitative answers and mathematical laws are found, agent based models can be
imagined to describe such non-equilibrium processes.
It is found that empirical laws can be deduced and related to preferential
attachment processes, like on evolving network; we propose two different
algorithmic models reproducing as well the data. Moreover, a population
growth-death equation is shown to be a plausible modeling of evolution dynamics
in a continuous time framework. Differences with language dynamic competition
is emphasized.Comment: submitted to EP
Are Financial Crashes Predictable?
We critically review recent claims that financial crashes can be predicted
using the idea of log-periodic oscillations or by other methods inspired by the
physics of critical phenomena. In particular, the October 1997 `correction'
does not appear to be the accumulation point of a geometric series of local
minima.Comment: LaTeX, 5 pages + 1 postscript figur
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