Search results for "Mathematica"
showing 10 items of 7971 documents
Errors in Monte Carlo simulations using shift register random number generators
1996
We report large systematic errors in Monte Carlo simulations of the tricritical Blume-Capel model using single spin Metropolis updating. The error, manifest as a $20\%$ asymmetry in the magnetisation distribution, is traced to the interplay between strong triplet correlations in the shift register random number generator and the large tricritical clusters. The effect of these correlations is visible only when the system volume is a multiple of the random number generator lag parameter. No such effects are observed in related models.
Seven Mathematical Models of Hemorrhagic Shock
2021
Although mathematical modelling of pressure-flow dynamics in the cardiocirculatory system has a lengthy history, readily finding the appropriate model for the experimental situation at hand is often a challenge in and of itself. An ideal model would be relatively easy to use and reliable, besides being ethically acceptable. Furthermore, it would address the pathogenic features of the cardiovascular disease that one seeks to investigate. No universally valid model has been identified, even though a host of models have been developed. The object of this review is to describe several of the most relevant mathematical models of the cardiovascular system: the physiological features of circulator…
General Systems Theory and Systems Biology
2015
We should not imagine that Systems Biology was born yesterday, indeed von Bertalanffy was a well-known supporter of the need to approach biological entities from the notion of a system. There is a tradition, dating back to early times, calling for the study of living things as a whole. Holism is no stranger to modern Systems Biology and, likewise, von Bertalanffy supported the quantitative study of the whole from the interaction of its parts.
epiModel: A system to build automatically systems of differential equations of compartmental type-epidemiological models
2011
In this paper we describe epiModel, a code developed in Mathematica that facilitates the building of systems of differential equations corresponding to type-epidemiological linear or quadratic models whose characteristics are defined in text files following an easy syntax. It includes the possibility of obtaining the equations of models involving age and/or sex groups. © 2011.
THE INFLUENCE OF CONTRARIANS AND OPPORTUNISTS ON THE STABILITY OF A DEMOCRACY IN THE SZNAJD MODEL
2004
Sznajd-Weron and Sznajd introduced a model investigating the democratic development in a closed community. This model is based on the USDF-principle ("united we stand, divided we fall"). However, it faces the problem that the system tends either to a dictatorship (i.e., 100% pro or 100% contra) or to a stalemate state (i.e., exactly 50% pro, 50% contra). Based on their model, I will show that a democratic system keeps alive due to the existence of both opportunists and persons in opposition.
Spacelike energy of timelike unit vector fields on a Lorentzian manifold
2004
On a Lorentzian manifold, we define a new functional on the space of unit timelike vector fields given by the L2 norm of the restriction of the covariant derivative of the vector field to its orthogonal complement. This spacelike energy is related with the energy of the vector field as a map on the tangent bundle endowed with the Kaluza–Klein metric, but it is more adapted to the situation. We compute the first and second variation of the functional and we exhibit several examples of critical points on cosmological models as generalized Robertson–Walker spaces and Godel universe, on Einstein and contact manifolds and on Lorentzian Berger’s spheres. For these critical points we have also stu…
A historical account on characterizations ofC1-manifolds in Euclidean spaces by tangent cones
2014
Abstract A historical account on characterizations of C 1 -manifolds in Euclidean spaces by tangent cones is provided. Old characterizations of smooth manifold (by tangent cones), due to Valiron (1926, 1927) and Severi (1929, 1934) are recovered; modern characterizations, due to Gluck (1966, 1968) and Tierno (1997) are restated. All these results are consequences of the Four-cones coincidence theorem due to [1] .
Tangent measures and densities
1995
Tangent Measures, Densities, and Singular Integrals
1995
We introduce tangent measures in the sense of David Preiss. We discuss their applications to the density and rectifiability properties of general Borel measures in ℝ n as well as to the behaviour of certain singular integrals with respect to such measures.