• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 15
  • 7
  • 1
  • 1
  • Tagged with
  • 26
  • 26
  • 9
  • 7
  • 6
  • 6
  • 5
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

The Dynamics of Semigroups of Contraction Similarities on the Plane

Stefano Silvestri (6983546) 16 October 2019 (has links)
<div>Given a parametrized family of Iterated Function System (IFS) we give sufficient conditions for a parameter on the boundary of the connectedness locus, M, to be accessible from the complement of M.</div><div>Moreover, we provide a few examples of such parameters and describe how they are connected to Misiurewicz parameter in the Mandelbrot set, i.e. the connectedness locus of the quadratic family z^2+c.<br></div>
22

Using systems theory to do philosophy: One approach, and some suggested terminology.

Ingram, David January 2007 (has links)
This thesis employs perspectives inspired by General Systems Theory to address issues in philosophy, including moral philosophy and philosophy of mind. I present an overview of a range of ideas from the study of physical systems that may be used to provide a firm physicalist foundation to explorations of some common questions in philosophy. I divide these topics into three categories: the Physical Category, the Relevance Category and the Signal Elements Category. I interpret concepts from General Systems Theory, including information and entropy, in a way that I believe facilitates their incorporation into philosophical discussion. I also explain various points arising from General Systems Theory, such as order and disorder, stability, complexity, and self-organisation, and show how ideas from these areas can be applied to certain philosophical problems. I explain relevance in terms of stability, in order to link these scientific perspectives to questions in moral philosophy. I suggest a possible physical foundation for a theory of morality, which takes the form of a variety of Utilitarianism, intended to balance the competing needs of open systems to manage entropy. Such a theory of morality must be capable of dealing with limitations arising from the physicality of information; I propose game theory as a solution to this problem. This thesis also covers issues connected to the above points regarding the nature of consciousness and communication. In particular, I examine the role of linguistic associations in consciousness; and some related features of language and other non-linear representational schemes.
23

Connectivity of Julia sets of transcendental meromorphic functions

Taixés i Ventosa, Jordi 22 September 2011 (has links)
Newton's method associated to a complex holomorphic function f is defined by the dynamical system Nf(z) = z – f(z) / f'(z). As a root-finding algorithm, a natural question is to understand the dynamics of Nf about its fixed points, as they correspond to the roots of the function f. In other words, we would like to understand the basins of attraction of Nf, i.e., the sets of points that converge to a root of f under the iteration of Nf. Basins of attraction are actually just one type of stable component or component of the Fatou set, defined as the set of points for which the family of iterates is defined and normal locally. The Julia set or set of chaos is its complement (taken on the Riemann sphere). The study of the topology of these two sets is key in Holomorphic Dynamics. In 1990, Mitsuhiro Shishikura proved that, for any non-constant polynomial P, the Julia set of NP is connected. In fact, he obtained this result as a consequence of a much more general theorem for rational functions: If the Julia set of a rational function R is disconnected, then R has at least two weakly repelling fixed points. With the final goal of proving the transcendental version of this theorem, in this Thesis we see that: If a transcendental meromorphic function f has either a multiply-connected attractive basin, or a multiply-connected parabolic basin, or a multiply-connected Fatou component with simply-connected image, then f has at least one weakly repelling fixed point. Our proof for this result is mainly based in two techniques: quasiconformal surgery and the study of the existence of virtually repelling fixed points. We conclude the Thesis with an idea of the strategy for the proof of the case of Herman rings, as well as some ideas for the case of Baker domains, which is left as a subject for a future project.
24

Numerical Study Of The Complex Dynamics Of Sheared Nematogenic Fluids

Chakraborty, Debarshini 01 1900 (has links) (PDF)
In this thesis, we have tried to explain the regular and irregular(chaotic) dynamics of worm like micellar solutions on applying shear, through a detailed study of the equation of motion of a nematic order parameter tensor coupled to a hydrodynamic velocity field. We have assumed spatial variations only along one direction i.e. the gradient direction(1D model). The resulting phase diagram shows various interesting steady states or phases such as spatiotemporal chaos, temporal and spatiotemporal periodicities, and alignment of the director axis along the imposed flow field. The coupling of the orientational degrees of freedom of the order parameter with the hydrodynamic flow field holds the key to the appearance of dynamic shear bands in the system. We have solved numerically a set of coupled nonlinear equations to obtain the order parameter stress developed in the system; the magnitude of the order parameter tensor, the biaxiality parameter and the orientation of the director axis of the nemato gens under shear have also been studied in detail. To study the phase diagram obtained by time integration of the equation of motion mathematically, a stability analysis of the fixed point of motion for various parameter values has been performed so that the location of the chaotic-to-aligned phase boundary is verified. Also in the periodic region of the phase diagram, the stability of limit cycles is tested by analysing the fixed point of the corresponding Poincare map. Stability analysis of the periodic orbits leads to the observation that in the parameter space, there are regions of phase coexistence where chaotic or spatiotemporally intermittent behaviour coexists with periodic behaviour. When corrections in the imposed velocity field due to the order parameter stress were taken into account and the order parameter response was looked into at several points in the parameter space, the modified equations of motion were found to reproduce the earlier behaviour in all the different regimes if the value of a dimensionless viscosity parameter is taken to be such that the bare viscous stress overrides the order parameter stress. The phase boundaries are however different from the ones seen in the earlier model. However, for a choice of the viscosity parameter such that the order parameter stress and the bare viscous stress are comparable, we see two distinctly different attractors: a banded, periodic one that is common to both α1equalto 0, and not equal to 0 and a banded chaotic one for α1not equal to 0. Here, α1is a parameter that governs the nonlinearity in the stretching of the order parameter tensor along the direction of the applied shear. Quantitative analysis of the various chaotic attractors throws up not only positive Lyapunov exponents but also that the banded chaos is a “flip-flop” kind of chaos where the switching between two long-lived states of high and lows hear stress is chaotic, where as the behaviour in either of the two states is periodic, with either a single, isolated frequency or a bunch of harmonics. Also, the spatial correlation of the shear stress in the chaotic attractors is of much larger range than the temporal correlation, the latter being almost delta-function-like. On increasing the temperature of the system till it is above the isotropic–nematic transition temperature in the absence of shear, we find that under shear, similar attractors as those in the nematic case are observed, both for passive advection and for the full 1D hydrodynamics. This is an encouraging result since actual experiments are performed at a temperature for which the system is in the isotropic phase in the absence of shear. Thus for the 1D system, the parameter space has been explored quite extensively. Considering spatial variations only along the gradient axis of the system under shear is not enough since experiments have observed interesting behaviour in the vorticity plane in which Taylor velocity rolls were noted. Hence taking the system to 2D was necessary. Our numerical study of the 2D system under shear is incomplete because we came across computational difficulties. However, on shorter time scales we have seen a two-banded state with an oscillating interface and Taylor velocity rolls as well. The methodology used for the 2D study can also be used to reproduce the 1D results by the simple step of taking initial condition with no variation in the vorticity direction. This automatically ensures that no variation in the vorticity direction ever builds up because the equations of motion ensure that these variations in the system do not grow by themselves unless fed in at the start. Using this method, we were able to reproduce all the attractors found in the 1D calculation. Thus the 1D attractors have been observed using two different methods of calculation. Further work on the full 2D numerics needs to be done because we believe that spatiotemporally complex steady-state attractor s exist in the 2D system also for appropriate values of the parameters.
25

The Role Of Potential Theory In Complex Dynamics

Bandyopadhyay, Choiti 05 1900 (has links) (PDF)
Potential theory is the name given to the broad field of analysis encompassing such topics as harmonic and subharmonic functions, the Dirichlet problem, Green’s functions, potentials and capacity. In this text, our main goal will be to gain a deeper understanding towards complex dynamics, the study of dynamical systems defined by the iteration of analytic functions, using the tools and techniques of potential theory. We will restrict ourselves to holomorphic polynomials in C. At first, we will discuss briefly about harmonic and subharmonic functions. In course, potential theory will repay its debt to complex analysis in the form of some beautiful applications regarding the Julia sets (defined in Chapter 8) of a certain family of polynomials, or a single one. We will be able to provide an explicit formula for computing the capacity of a Julia set, which in some sense, gives us a finer measurement of the set. In turn, this provides us with a sharp estimate for the diameter of the Julia set. Further if we pick any point w from the Julia set, then the inverse images q−n(w) span the whole Julia set. In fact, the point-mass measures with support at the discrete set consisting of roots of the polynomial, (qn-w) will eventually converge to the equilibrium measure of the Julia set, in the weak*-sense. This provides us with a very effective insight into the analytic structure of the set. Hausdorff dimension is one of the most effective notions of fractal dimension in use. With the help of potential theory and some ergodic theory, we can show that for a certain holomorphic family of polynomials varying over a simply connected domain D, one can gain nice control over how the Hausdorff dimensions of the respective Julia sets change with the parameter λ in D.
26

Financial Stability, Macroeconomic Cycles and Complex Expectation Dynamics

Hartmann, Florian 07 February 2018 (has links)
The thesis tries to shed light on mechanisms that endanger the macro-financial stability of economies. For that purpose a modeling framework is set-up which allows for cyclical behavior on the macro level and does not automatically enforce monotonic convergence of the dynamics to a stable equilibrium. Thus, the assumption of rational expectation must be replaced by alternative expectation formation schemes which are more relevant from an empirical point of view. We start to put forth a modeling approach of a partial, but crucially important market for the whole economy. As we could learn from the great recession, activities in the housing market can trigger economy-wide crises when financial markets are highly interconnected and exert a lasting impact on real markets. The next step is to construct an integrated macro model which captures the interaction of real and financial markets with respect to possible destabilizing linkages. Policy instruments can work then as remedies as long as they are designed in a manner that takes account of the underlying feedback structure. Step by step the models are extended throughout the chapters by refinement of the macro-financial structure. A banking sector is introduced and many issues arising with this addition are discussed. After having addressed several configurations of the banking sector, the focus is shifted to the expectation formation of agents. Behavioral traders on the micro level then drive complex dynamics on the macro level, which eventually feedback on the distribution of different types of trading strategies. We also investigate the implications of such behavioral expectation formations for open economies. Finally, we look at potential instabilities that arise from the supply side of macroeconomies in the long run. A model with a differentiated labor market structure and an accumulation mechanism is used to display distributive cycle dynamics and their stability implications.

Page generated in 0.0545 seconds