161 research outputs found
Income distribution patterns from a complete social security database
We analyze the income distribution of employees for 9 consecutive years
(2001-2009) using a complete social security database for an economically
important district of Romania. The database contains detailed information on
more than half million taxpayers, including their monthly salaries from all
employers where they worked. Besides studying the characteristic distribution
functions in the high and low/medium income limits, the database allows us a
detailed dynamical study by following the time-evolution of the taxpayers
income. To our knowledge, this is the first extensive study of this kind (a
previous japanese taxpayers survey was limited to two years). In the high
income limit we prove once again the validity of Pareto's law, obtaining a
perfect scaling on four orders of magnitude in the rank for all the studied
years. The obtained Pareto exponents are quite stable with values around
, in spite of the fact that during this period the economy
developed rapidly and also a financial-economic crisis hit Romania in
2007-2008. For the low and medium income category we confirmed the
exponential-type income distribution. Following the income of employees in
time, we have found that the top limit of the income distribution is a highly
dynamical region with strong fluctuations in the rank. In this region, the
observed dynamics is consistent with a multiplicative random growth hypothesis.
Contrarily with previous results obtained for the japanese employees, we find
that the logarithmic growth-rate is not independent of the income.Comment: 10 pages, 7 Figure
Orientational order parameters of a de Vries–type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction
The orientational order parameters 〈P2〉 and 〈P4〉 of the ferroelectric, de Vries–type liquid crystal 9HL have been determined in the SmA* and SmC* phases by means of polarized Raman spectroscopy, and in the SmA* phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a “sugar loaf” orientational distribution in the SmA* phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries–type behavior is considered
Fuzzy-Logical model for analysis of sustainable development of fuel and energy complex enterprises
The purpose of this article is to build a mathematical model for analyzing the sustainability of the development of an enterprise in the fuel and energy complex, integrated into an information management syste
Metals in high magnetic field: a new universality class of Fermi liquids
Parquet equations, describing the competition between superconducting and
density-wave instabilities, are solved for a three-dimensional isotropic metal
in a high magnetic field when only the lowest Landau level is filled. In the
case of a repulsive interaction between electrons, a phase transition to the
density-wave state is found at finite temperature. In the opposite case of
attractive interaction, no phase transition is found. With decreasing
temperature , the effective vertex of interaction between electrons
renormalizes toward a one-dimensional limit in a self-similar way with the
characteristic length (transverse to the magnetic field) decreasing as
( is a cutoff). Correlation functions have
new forms, previously unknown for conventional one-dimensional or
three-dimensional Fermi-liquids.Comment: 13 pages + 4 figures (included
Advantages of cluster approach in managing the economy of the Russian Federation
The formation of new approaches to economic growth that will unite scientific, educational and production potentials, as well as lead to an increase in the competitiveness of enterprises, the region, the economy of the nation in general, both research and educational organizations, will have a further multiplier effect on the formation of an economy processes of a new order. This trend in the formation of modern approaches, and their successful implementation will result in the transition of the Russian economy to an economy of innovative type, more adjusted to relevant world trends and markets. The urgency of implementing cluster approaches in the development of the economy on the basis of innovative territorial clusters is dictated by the need to ensure a balanced and sustainable development of the domestic economic system through the promotion of innovation in individual territories. Such actively formed territories can now become clusters. In the modern world, clusters, with their completely different policy of realizing their activities, displaying the newest forms and competitiveness, become springboards' that help launch territories into the economy of the future. Today, the competitiveness of the economy of the region and the state depends not only on technical achievements or inventions, but also on organizational changes that contribute to the achievement by them of high commercial results, as well as on marketing innovations in the promotion and implementation of cluster policies
Parquet solution for a flat Fermi surface
We study instabilities occurring in the electron system whose Fermi surface
has flat regions on its opposite sides. Such a Fermi surface resembles Fermi
surfaces of some high- superconductors. In the framework of the parquet
approximation, we classify possible instabilities and derive
renormalization-group equations that determine the evolution of corresponding
susceptibilities with decreasing temperature. Numerical solutions of the
parquet equations are found to be in qualitative agreement with a ladder
approximation. For the repulsive Hubbard interaction, the antiferromagnetic
(spin-density-wave) instability dominates, but when the Fermi surface is not
perfectly flat, the -wave superconducting instability takes over.Comment: REVTeX, 36 pages, 20 ps figures inserted via psfig. Submitted to
Phys. Rev.
Antiferromagnetic Interactions and the Superconducting Gap Function
Spin-fluctuation-mediated superconductivity is conventionally associated with
d_{x^2-y^2} pairing. We show that a generalized model of antiferromagnetic spin
fluctuations in three dimensions may also yield a state with formal ``s-wave''
(A_{1g}) symmetry but with line nodes at k_z \approx \pm \pi / 2c. We study
this new state within both BCS and Eliashberg theories using a realistic band
structure and find that it is more stable than the d_{x^2-y^2} (B_{1g}) state
over a wide range of parameters. Thus, models of spin-fluctuation-mediated
superconductivity must consider both possibilities on an equal footing.Comment: 4 pages, RevTeX with psfig, 2 PostScript figures included in
compressed form, one color PostScript figure available by request to
[email protected] or [email protected]. Minor changes and updated
references from original postin
Singlet pairing in the double chain t-J model
Applying the bosonization procedure to constrained fermions in the framework
of the one dimensional t-J model we discuss a scenario of singlet
superconductivity in a lightly doped double chain where all spin excitations
remain gapful.Comment: 13 pages, TeX, C Version 3.
Quantum Hall Effect in Three-dimensional Field-Induced Spin Density Wave Phases with a Tilted Magnetic Field
The quantum Hall effect in the three-dimensional anisotropic tight-binding
electrons is investigated in the field-induced spin density wave phases with a
magnetic field tilted to any direction. The Hall conductivity,
and , are shown to be quantized as a function of the wave vector
of FISDW, while stays zero, where is the most conducting
direction and and are perpendicular to .Comment: 18 pages, REVTeX 3.0, 1 figure is available upon request, to be
published in Physical Review
Superconductivity in carbon nanotube ropes
We investigate the conditions in which superconductivity may develop in ropes
of carbon nanotubes. It is shown that the interaction among a large number of
metallic nanotubes favors the appearance of a metallic phase in the ropes,
intermediate between respective phases with spin-density-wave and
superconducting correlations. These arise in samples with about 100 metallic
nanotubes or more, where the long-range Coulomb interaction is very effectively
reduced and it may be overcome by the attractive interaction from the exchange
of optical phonons within each nanotube. We estimate that the probability for
the tunneling of Cooper pairs between neighboring nanotubes is much higher than
that for single electrons in a disordered rope. The effect of pair hopping is
therefore what establishes the intertube coherence, and the tunneling amplitude
of the Cooper pairs dictates the scale of the transition to the superconducting
state.Comment: 12 page
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