486 research outputs found
Dynamical model and nonextensive statistical mechanics of a market index on large time windows
The shape and tails of partial distribution functions (PDF) for a financial
signal, i.e. the S&P500 and the turbulent nature of the markets are linked
through a model encompassing Tsallis nonextensive statistics and leading to
evolution equations of the Langevin and Fokker-Planck type. A model originally
proposed to describe the intermittent behavior of turbulent flows describes the
behavior of normalized log-returns for such a financial market index, for small
and large time windows, both for small and large log-returns. These turbulent
market volatility (of normalized log-returns) distributions can be sufficiently
well fitted with a -distribution. The transition between the small time
scale model of nonextensive, intermittent process and the large scale Gaussian
extensive homogeneous fluctuation picture is found to be at a 200 day
time lag. The intermittency exponent () in the framework of the
Kolmogorov log-normal model is found to be related to the scaling exponent of
the PDF moments, -thereby giving weight to the model. The large value of
points to a large number of cascades in the turbulent process. The
first Kramers-Moyal coefficient in the Fokker-Planck equation is almost equal
to zero, indicating ''no restoring force''. A comparison is made between
normalized log-returns and mere price increments.Comment: 40 pages, 14 figures; accepted for publication in Phys Rev
Lifetime distributions in the methods of non-equilibrium statistical operator and superstatistics
A family of non-equilibrium statistical operators is introduced which differ
by the system age distribution over which the quasi-equilibrium (relevant)
distribution is averaged. To describe the nonequilibrium states of a system we
introduce a new thermodynamic parameter - the lifetime of a system.
Superstatistics, introduced in works of Beck and Cohen [Physica A \textbf{322},
(2003), 267] as fluctuating quantities of intensive thermodynamical parameters,
are obtained from the statistical distribution of lifetime (random time to the
system degeneracy) considered as a thermodynamical parameter. It is suggested
to set the mixing distribution of the fluctuating parameter in the
superstatistics theory in the form of the piecewise continuous functions. The
distribution of lifetime in such systems has different form on the different
stages of evolution of the system. The account of the past stages of the
evolution of a system can have a substantial impact on the non-equilibrium
behaviour of the system in a present time moment.Comment: 18 page
The Muonium Atom as a Probe of Physics beyond the Standard Model
The observed interactions between particles are not fully explained in the
successful theoretical description of the standard model to date. Due to the
close confinement of the bound state muonium () can be used as
an ideal probe of quantum electrodynamics and weak interaction and also for a
search for additional interactions between leptons. Of special interest is the
lepton number violating process of sponteanous conversion of muonium to
antimuonium.Comment: 15 pages,6 figure
Anisotropy at the end of the cosmic ray spectrum?
The starburst galaxies M82 and NGC253 have been proposed as the primary
sources of cosmic rays with energies above eV. For energies \agt
10^{20.3} eV the model predicts strong anisotropies. We calculate the
probabilities that the latter can be due to chance occurrence. For the highest
energy cosmic ray events in this energy region, we find that the observed
directionality has less than 1% probability of occurring due to random
fluctuations. Moreover, during the first 5 years of operation at Auger, the
observation of even half the predicted anisotropy has a probability of less
than to occur by chance fluctuation. Thus, this model can be subject
to test at very small cost to the Auger priors budget and, whatever the outcome
of that test, valuable information on the Galactic magnetic field will be
obtained.Comment: Final version to be published in Physical Review
Magnetic Fields in the Milky Way
This chapter presents a review of observational studies to determine the
magnetic field in the Milky Way, both in the disk and in the halo, focused on
recent developments and on magnetic fields in the diffuse interstellar medium.
I discuss some terminology which is confusingly or inconsistently used and try
to summarize current status of our knowledge on magnetic field configurations
and strengths in the Milky Way. Although many open questions still exist, more
and more conclusions can be drawn on the large-scale and small-scale components
of the Galactic magnetic field. The chapter is concluded with a brief outlook
to observational projects in the near future.Comment: 22 pages, 5 figures, to appear in "Magnetic Fields in Diffuse Media",
eds. E.M. de Gouveia Dal Pino and A. Lazaria
Sociology Back to the Publics
This article is a reading of the `new sociology' that is mainly identified with the works of C. Wright Mills and Alvin Gouldner. Its main argument is that during the past 40 years the new sociology gave back a public face to sociology. This distinguishes it from the `old sociology' that had not been able to free itself from `private' social values. It is argued that Mills' power elite and Gouldner's coming crisis theses provided the foundation for a common enterprise among many `new sociologists' to develop a critical and public sociology that would seek to shape what Mills called the `democratic society of publics'.`New sociologists' share a critique of modern societies, namely, that though most modern societies have formal democracies, a substantial democratic social structure of publics is often lacking, due to the erosion of the public sphere by private values
Ionic and electronic structure of sodium clusters up to N=59
We determined the ionic and electronic structure of sodium clusters with even
electron numbers and 2 to 59 atoms in axially averaged and three-dimensional
density functional calculations. A local, phenomenological pseudopotential that
reproduces important bulk and atomic properties and facilitates structure
calculations has been developed. Photoabsorption spectra have been calculated
for , , and to
. The consistent inclusion of ionic structure considerably
improves agreement with experiment. An icosahedral growth pattern is observed
for to . This finding is supported by
photoabsorption data.Comment: To appear in Phys. Rev. B 62. Version with figures in better quality
can be requested from the author
A Pragmatic Assessment of Government Support for Organic Agriculture in Ireland
Drawing on a pragmatic approach, this paper provides an analysis of governmental support for organic farming in Ireland. There are varying levels of encouragement and programmes provided to farmers in their conversion from conventional to organic production, and in their maintenance of organic production. Support policies vary across regions and are linked to European Union legislation, thus it is challenging to document the many types of support in place. This research investigates relevant technical, financial, and policy support available to organic farmers in Ireland. This exploratory study develops an assessment of Ireland within eight key categories of organic agricultural support: leadership, policy, research, technical support, financial support, marketing and promotion, education and information, and future developments. Information and data from the Irish Department of Agriculture, Fisheries and Food (DAFF), the Irish Agriculture and Food Development Authority (Teagasc), and other governmental and semi-governmental agencies were utilized to assess the level of support in each category. Following the pragmatic approach, this assessment provides key findings which allow policymakers, organizations and citizens to better understand the current situation and set a path for the future development of organic farming in Ireland
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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