1,720,970 research outputs found
On the history of the integrative field theory: Einstein's year of unsuccessful research
No full textSymmetry transformations for the generalized Lane-Emden equation
No full textBy uncovering symmetries, this paper provides a technique for integrating the generalized Lane-Emden equation. Their existence explains why it has been possible to obtain exact solutions of the generalized Lane-Emden equation of the first kind only for particular values of parameters
Albert Einstein and Friedrich Dessauer: Political views and political practice
No full textIn this case study I compare the political views of the physicists Albert Einstein and Friedrich Dessauer between the first and second world wars, and I investigate their translation into concrete political practice. Both departed from their roles as experts in physics in favor of political engagement. The essence of Einstein's political practice seems to have been a form of political participation in exerting moral influence on people and organizations through public declarations and appeals in isolation from political mass movements. Dessauer exerted political influence both through public office (as a member of Parliament for the Catholic Center Party) and by acquiring a newspaper. The different political practice of both Einstein and Dessauer were unsuccessful in thwarting the Nazi takeover
What kind of science is cosmology?
No full textIn recent years, by theory and observation cosmology has advanced substantially. Parameters of the concordance or ACDM cosmological model are given with unprecedented precision ("precision cosmology"). On the other hand, 95% of the matter content of the universe are of an unknown nature. This awkward situation motivates the present attempt to find cosmology's place among the (exact) natural sciences. Due to its epistemic and methodical particularities, e.g., as a mathematized historical science, cosmology occupies a very special place. After going through some of the highlights of cosmological modeling, the conclusion is reached that knowledge provided by cosmological modeling cannot he as explicative and secure as knowledge gained by laboratory physics. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA. Weinhei
Weak Lie symmetry and extended Lie algebra
No full textThe concept of weak Lie motion (weak Lie symmetry) is introduced. Applications given exhibit a reduction of the usual symmetry, e.g., in the case of the rotation group. In this context, a particular generalization of Lie algebras is found ("extended Lie algebras") which turns out to be an involutive distribution or a simple example for a tangent Lie algebroid. Riemannian and Lorentz metrics can be introduced on such an algebroid through an extended Cartan-Killing form. Transformation groups from non-relativistic mechanics and quantum mechanics lead to such tangent Lie algebroids and to Lorentz geometries constructed on them (1-dimensional gravitational fields). (C) 2013 American Institute of Physics
Alternative to the Palatini method: A new variational principle
No full textA variational principle is suggested within Riemannian geometry, in which an auxiliary metric and the Levi Civita connection are varied independently. The auxiliary metric plays the role of a Lagrange multiplier and introduces nonminimal coupling of matter to the curvature scalar. The field equations are 2nd order PDEs and easier to handle than those following from the so-called Palatini method. Moreover, in contrast to the latter method, no gradients of the matter variables appear. In cosmological modeling, the physics resulting from the alternative variational principle will differ from the modeling using the standard Palatini method
A golden age of general relativity? Some remarks on the history of general relativity
No full textThis article deals with the concepts "renaissance" and "low water mark between 1925 and 1955" of general relativity suggested in the literature. By empirical data, it is shown that no such period did exist. Research on general relativity continued continuously since the 1920s interrupted only by the second world war. On a broad scale, research on general relativity started only after 1945
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