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Norbert Straumann

Publications and source records attributed to Norbert Straumann.

42 records · Page 3Linked to original sources
arXiv1997

Zero Modes of the Dirac Operator for regular Einstein-Yang-Mills Background fields

The existence of normalizable zero modes of the twisted Dirac operator is proven for a class of static Einstein-Yang-Mills background fields with a half-integer Chern-Simons number. The proof holds for any gauge group and applies to Dirac spinors in an arbitrary representation of the gauge group. The class of background fields contains all regular, asymptotically flat, CP-symmetric configurations with a connection that is globally described by a time-independent spatial one-form which vanishes sufficiently fast at infinity. A subset is provided by all neutral, spherically symmetric configurations which satisfy a certain genericity condition, and for which the gauge potential is purely magnetic with real magnetic amplitudes.

hep-th↗
arXiv1996

On Newton-Cartan Cosmology

After a brief summary of the Newton-Cartan theory in a form which emphasizes its close analogy to general relativity, we illustrate the theory with selective applications in cosmology. The geometrical formulation of this nonrelativistic theory of gravity, pioneered by Cartan and further developed by various workers, leads to a conceptually sound basis of Newtonian cosmology. In our discussion of homogeneous models and cosmological perturbation theory, we stress the close relationship with their general relativistic treatments. Spatially compact flat models also fit into this framework.

gr-qc↗
arXiv1996

Asymptotic Behavior of the Einstein-Yang-Mills-Dilaton System for a Closed Friedmann-Lemaitre Universe

We study the coupled Einstein-Yang-Mills-Dilaton (EYMD) equations for a Fried\-mann-Le\-mai\-tre universe with constant curvature $k=1$. Our detailed analysis is restricted to the case where the dilaton potential and the cosmological constant vanish. Also assuming a static gauge field, we present analytical and numerical results on the behavior of solutions of the EYMD equations. For different values of the dilaton coupling constant we analyze the phase portrait for the time evolution of the dilaton field and give the behavior of the scale factor. It turns out that there are no inflationary stages in this model.

gr-qc↗