708 research outputs found
Gradient Pattern Analysis of Cosmic Structure Formation: Norm and Phase Statistics
This paper presents the preliminary results of the characterization of
pattern evolution in the process of cosmic structure formation. We are applying
on N-body cosmological simulations data the technique proposed by Rosa, Sharma
& Valdivia (1999) and Ramos et al. (2000) to estimate the time behavior of
asymmetries in the gradient field. The gradient pattern analysis is a well
tested tool, used to build asymmetrical fragmentation parameters estimated over
a gradient field of an image matrix able to quantify a complexity measure of
nonlinear extended systems. In this investigation we work with the high
resolution cosmological data simulated by the Virgo consortium, in different
time steps, in order to obtain a diagnostic of the spatio-temporal disorder in
the matter density field. We perform the calculations of the gradient vectors
statistics, such as mean, variance, skewness, kurtosis, and correlations on the
gradient field. Our main goal is to determine different dynamical regimes
through the analysis of complex patterns arising from the evolutionary process
of structure formation. The results show that the gradient pattern technique,
specially the statistical analysis of second and third gradient moment, may
represent a very useful tool to describe the matter clustering in the Universe.Comment: Accepted for publication in Physica
Nonextensivity and Galaxy Clustering in the Universe
We investigate two important questions about the use of the nonextensive
thermostatistics (NETS) formalism in the context of nonlinear galaxy clustering
in the Universe. Firstly, we define a quantitative criterion for justifying
nonextensivity at different physical scales. Then, we discuss the physics
behind the ansatz of the entropic parameter . Our results suggest the
approximate range where nonextensivity can be justified and, hence, give some
support to the applicability of NETS to the study of large scale structures.Comment: 8 pages, written version of a talk presented in the International
Workshop on Trends and Perspectives on Extensive and Non-Extensive
Statistical Mechanics. Accepted for publication in Physica
Chaotic scalar fields as models for dark energy
We consider stochastically quantized self-interacting scalar fields as
suitable models to generate dark energy in the universe. Second quantization
effects lead to new and unexpected phenomena is the self interaction strength
is strong. The stochastically quantized dynamics can degenerate to a chaotic
dynamics conjugated to a Bernoulli shift in fictitious time, and the right
amount of vacuum energy density can be generated without fine tuning. It is
numerically observed that the scalar field dynamics distinguishes fundamental
parameters such as the electroweak and strong coupling constants as
corresponding to local minima in the dark energy landscape. Chaotic fields can
offer possible solutions to the cosmological coincidence problem, as well as to
the problem of uniqueness of vacua.Comment: 30 pages, 3 figures. Replaced by final version accepted by Phys. Rev.
Adaptive Effects of Static Muscular Strength Training
The trend towards mechanization of tasks involving manual labor has increased the importance of static muscular activity (isometric contractions). Information about the physiological reaction to static muscular activity has been increasing rapidly over the last few decades, but little information has been developed on the adaptive responses to chronic exposure to static muscular activity. This paper reports the results of an experiment on adaptive cardiovascular changes to a five week training program in which the % MVC was maintained at 50% for the entire program, i.e., weekly adjustments were made for increases in strength. The only significant change in the cardiovascular response to the training program was an increase in the rate at which the heart rate increased during periods of contraction. The average level of heart rate, systolic blood pressure and diastolic blood pressure did not change with training. Neither the systolic or diastolic blood pressure modified their rates of change due to training. Significant changes in strength and endurance hold capacity were also noted.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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
On the reliability of a simple method for scoring phenotypes to estimate heritability: A case study with pupal color in Heliconius erato phyllis, Fabricius 1775 (Lepidoptera, Nymphalidae)
In this paper, two methods for assessing the degree of melanization of pupal exuviae from the butterfly Heliconius erato phyllis, Fabricius 1775 (Lepidoptera, Nymphalidae, Heliconiini) are compared. In the first method, which was qualitative, the exuviae were classified by scoring the degree of melanization, whereas in the second method, which was quantitative, the exuviae were classified by optical density followed by analysis with appropriate software. The heritability (h2) of the degree of melanization was estimated by regression and analysis of variance. The estimates of h 2 were similar with both methods, indicating that the qualitative method could be particularly suitable for field work. The low estimates obtained for heritability may have resulted from the small sample size (n = 7-18 broods, including the parents) or from the allocation-priority hypothesis in which pupal color would be a lower priority trait compared to morphological traits and adequate larval development
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