arXiv subjects

Uwe Muench

Publications and source records attributed to Uwe Muench.

5 recordsLinked to original sources

arXiv2002

Length measurement in accelerated systems

We investigate the limitations of length measurements by accelerated observers in Minkowski spacetime brought about via the hypothesis of locality, namely, the assumption that an accelerated observer at each instant is equivalent to an otherwise identical momentarily comoving inertial observer. We find that consistency can be achieved only in a rather limited neighborhood around the observer with linear dimensions that are negligibly small compared to the characteristic acceleration length of the observer.

gr-qc↗

arXiv2000

Acceleration-Induced Nonlocal Electrodynamics in Minkowski Spacetime

We discuss two nonlocal models of electrodynamics in which the nonlocality is induced by the acceleration of the observer. Such an observer actually measures an electromagnetic field that exhibits persistent memory effects. We compare Mashhoon's model with a new ansatz developed here in the framework of charge & flux electrodynamics with a constitutive law involving the Levi-Civita connection as seen from the observer's local frame and conclude that they are in partial agreement only for the case of constant acceleration.

gr-qc↗

arXiv1998

A small guide to variations in teleparallel gauge theories of gravity and the Kaniel-Itin model

Recently Kaniel & Itin proposed a gravitational model with the wave type equation [\square+λ(x)]\vartheta^α=0 as vacuum field equation, where \vartheta^αdenotes the coframe of spacetime. They found that the viable Yilmaz-Rosen metric is an exact solution of the tracefree part of their field equation. This model belongs to the teleparallelism class of gravitational gauge theories. Of decisive importance for the evaluation of the Kaniel-Itin model is the question whether the variation of the coframe commutes with the Hodge star. We find a master formula for this commutator and rectify some corresponding mistakes in the literature. Then we turn to a detailed discussion of the Kaniel-Itin model.

gr-qc↗

arXiv1997

Volume elements of spacetime and a quartet of scalar fields

Starting with a `bare' 4-dimensional differential manifold as a model of spacetime, we discuss the options one has for defining a volume element which can be used for physical theories. We show that one has to prescribe a scalar density σ. Whereas conventionally \sqrt{|\det g_{ij}|} is used for that purpose, with g_{ij} as the components of the metric, we point out other possibilities, namely σas a `dilaton' field or as a derived quantity from either a linear connection or a quartet of scalar fields, as suggested by Guendelman and Kaganovich.

gr-qc↗

arXiv1997

A note on post-Riemannian structures of spacetime

A four-dimensional differentiable manifold is given with an arbitrary linear connection $Γ_α^β=Γ_{iα}^βdx^i$. Megged has claimed that he can define a metric $G_{αβ}$ by means of a certain integral equation such that the connection is compatible with the metric. We point out that Megged's implicite definition of his metric $G_{αβ}$ is equivalent to the assumption of a vanishing nonmetricity. Thus his result turns out to be trivial.

gr-qc↗