448 research outputs found
On global geodesic mappings of -dimensional surfaces of revolution
In this paper we study geodesic mappings of -dimensional surfaces of
revolution. From the general theory of geodesic mappings of equidistant spaces
we specialize to surfaces of revolution and apply the obtained formulas to the
case of rotational ellipsoids. We prove that such -dimensional ellipsoids
admit non trivial smooth geodesic deformations onto -dimensional surfaces of
revolution, which are generally of a different type.Comment: 10 page
Canonical DSR
For a certain example of a "doubly special relativity theory" the modified
space-time Lorentz transformations are obtained from momentum space
transformations by using canonical methods. In the sequel an energy-momentum
dependent space-time metric is constructed, which is essentially invariant
under the modified Lorentz transformations. By associating such a metric to
every Planck cell in space and the energy-momentum contained in it, a solution
of the problem of macroscopic bodies in doubly special relativity is suggested.Comment: 11 page
Special Einstein's equations on K\"ahler manifolds
This work is devoted to the study of Einstein equations with a special shape
of the energy-momentum tensor. Our results continue Stepanov's classification
of Riemannian manifolds according to special properties of the energy-momentum
tensor to K\"ahler manifolds. We show that in this case the number of classes
reduces.Comment: 5 page
Isotropic Loop Quantum Cosmology with Matter II: The Lorentzian Constraint
The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum
cosmology coupled to a massless scalar field. As in the Euclidean case, the
discreteness of quantum geometry removes the classical singularity from the
quantum Friedmann models. In spite of the absence of the classical singularity,
a modified DeWitt initial condition is incompatible with a late-time smooth
behavior. Further, the smooth behavior is recovered only for positive or
negatives times but not both. An important feature, which is shared with the
Euclidean case, is a minimal initial energy of the order of the Planck energy
required for the system to evolve dynamically. By forming wave packets of the
matter field an explicit evolution in terms of an internal time is obtained.Comment: 19 pages, 4 figure
Blame games and democratic responsiveness
The link between opinion and policy is central to the functioning of representative democracy. Democracies are responsive to their citizens' preferences if citizens can influence governments' policy output. This article conceptualizes political blame games about policy controversies as venues of democratic responsiveness to obtain a more comprehensive understanding of the opinion-policy link in policy-heavy, conflictual democracies. The article shows how political actors convert public feedback to a policy controversy into blame game interactions, which in turn lead to political and policy responses by the government. A comparative-historical analysis of nine blame games in the United Kingdom, Germany and Switzerland reveals how institutions structure blame game interactions, and thus influence a political system's responsiveness during blame games. The analysis suggests that an important, yet neglected, expression of democratic quality of political systems is their ability to translate blame game interactions into policy responses. The study of blame games as venues of democratic responsiveness thus provides a new conceptual tool for assessing the health of representative democracies in more conflictual times
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