Anmeldelse af "Krigeren, borgeren og taberen"

"Krigeren, borgeren og taberen" / af Ole Thyssen, Henrik Dahl. - 2. oplag. [Kbh.] : Gyldendal, 2006. 243 sider

Exact Periodic Solutions of Shells Models of Turbulence

We derive exact analytical solutions of the GOY shell model of turbulence. In the absence of forcing and viscosity we obtain closed form solutions in terms of Jacobi elliptic functions. With three shells the model is integrable. In the case of many shells, we derive exact recursion relations for the amplitudes of the Jacobi functions relating the different shells and we obtain a Kolmogorov solution in the limit of infinitely many shells. For the special case of six and nine shells, these recursions relations are solved giving specific analytic solutions. Some of these solutions are stable whereas others are unstable. All our predictions are substantiated by numerical simulations of the GOY shell model. From these simulations we also identify cases where the models exhibits transitions to chaotic states lying on strange attractors or ergodic energy surfaces.Comment: 25 pages, 7 figure

Primordial magnetic field and non-Gaussianity of the 1-year Wilkinson Microwave Anisotropy Probe (WMAP) data

Alfven turbulence caused by statistically isotropic and homogeneous primordial magnetic field induces correlations in the cosmic microwave background anisotropies. The correlations are specifically between spherical harmonic modes a_{l-1,m} and a_{l+1,m}. In this paper we approach this issue from phase analysis of the CMB maps derived from the WMAP data sets. Using circular statistics and return phase mapping we examine phase correlation of \Delta l=2 for the primordial non-Gaussianity caused by the Alfven turbulence at the epoch of recombination. Our analyses show that such specific features from the power-law Alfven turbulence do not contribute significantly in the phases of the maps and could not be a source of primordial non-Gaussianity of the CMB.Comment: 8 pages, 7 figures, ApJ accepted with minor changes and the explanation on the whitened derived CMB map

Electro-hydrodynamics of binary electrolytes driven by modulated surface potentials

We study the electro-hydrodynamics of the Debye screening layer that arises in an aqueous binary solution near a planar insulating wall when applying a spatially modulated AC-voltage. Combining this with first order perturbation theory we establish the governing equations for the full non-equilibrium problem and obtain analytic solutions in the bulk for the pressure and velocity fields of the electrolyte and for the electric potential. We find good agreement between the numerics of the full problem and the analytics of the linear theory. Our work provides the theoretical foundations of circuit models discussed in the literature. The non-equilibrium approach also reveals unexpected high-frequency dynamics not predicted by circuit models.Comment: 9 pages including 4 figures. Accepted for PRE

Norm inequalities for the minimal and maximal operator, and differentiation of the integral

We study the weighted norm inequalities for the minimal operator, a new operator analogous to the Hardy-Littlewood maximal operator which arose in the study of reverse Hölder inequalities. We characterize the classes of weights which govern the strong and weak-type norm inequalities for the minimal operator in the two weight case, and show that these classes are the same. We also show that a generalization of the minimal operator can be used to obtain information about the differentiability of the integral in cases when the associated maximal operator is large, and we give a new condition for this maximal operator to be weak (1,1)

Extra-Dimensions effects on the fermion-induced quantum energy in the presence of a constant magnetic field

We consider a U(1) gauge field theory with fermion fields (or with scalar fields) that live in a space with $\delta$ extra compact dimensions, and we compute the fermion-induced quantum energy in the presence of a constant magnetic field, which is directed towards the x_3 axis. Our motivation is to study the effect of extra dimensions on the asymptotic behavior of the quantum energy in the strong field limit (eB>>M^{2}), where M=1/R. We see that the weak logarithmic growth of the quantum energy for four dimensions, is modified by a rapid power growth in the case of the extra dimensions.Comment: 18 pages, 4 figures, 2 tables, several correction

Norm inequalities for the minimal and maximal operator, and differentiation of the integral

We study the weighted norm inequalities for the minimal operator, a new operator analogous to the Hardy-Littlewood maximal operator which arose in the study of reverse Hölder inequalities. We characterize the classes of weights which govern the strong and weak-type norm inequalities for the minimal operator in the two weight case, and show that these classes are the same. We also show that a generalization of the minimal operator can be used to obtain information about the differentiability of the integral in cases when the associated maximal operator is large, and we give a new condition for this maximal operator to be weak (1,1)

Exploring attitudinal factors influencing modal shift:a latent class analysis of Danish commuters

Governments advocate for a modal shift from motorized transport modes to active modes. Various political approaches can be adopted to affect travel behavior and patterns. However, interventions spread across the entire population offer limited opportunities to achieve behavioral change. Furthermore, attitude has been shown to cut across demographic characteristics and strongly influence the conducted travel behavior. Therefore, a latent class analysis including significant sociodemographic variables and value-based attitudes concerning factors influencing transport, settlement, and additional priorities was performed. The study objectively identified five classes of Danish commuters with the same preconditions in terms of commuting distance but with clear differences in attitude and transport modes. Each latent class represents a unique combination of characteristics, which indicates the need to design target group-specific interventions to optimize the chances of influencing travel behavior. In particular, a group of malcontented motorists demonstrating a high intention to change exhibit negative feelings toward car travel and thus appear to act in contravention of their attitudes. In contrast, a class of immovable motorists was found, a class of beneficial commuters and finally two cycling dominated classes of passionate cyclists and environmentalist cyclists. Finally, this study has emphasized that similar attitudes can lead to dissimilar behaviors and that the same behavior can be exhibited for various reasons. We deduced how transport mode choice is influenced by various factors, with habit as one of the strongest, as those with strong habits seem disinclined to information about alternatives and call for “harder” policy interventions. The findings emphasize the importance of targeted interventions tailored to specific commuter groups to encourage modal shifts towards sustainable transportation.</p