9 found
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  1.  18
    On the Kinematics of the Torsion of Space-Time.Friedrich W. Hehl - 1985 - Foundations of Physics 15 (4):451-471.
    On a macroscopic level we take general relativity as the appropriate theory of space-time and gravity. We will argue that, on a more microscopic level, in the Compton wavelength regime of elementary particles, there are good reasons for suspecting the presence of a torsion of space-time. A corresponding gaugetheoretical formalism related to the Poincaré group is reviewed, and the kinematical consequences of the presence of a torsion are worked out. In particular we discuss the operational meaning and the measurability of (...)
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  2.  34
    An Assessment of Evans' Unified Field Theory II.Friedrich W. Hehl & Yuri N. Obukhov - 2008 - Foundations of Physics 38 (1):38-46.
    Evans attempted to develop a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. In an accompanying paper I, we analyzed this theory and summarized it in nine equations. We now propose a variational principle for a theory that implements some of the ideas that have been (imprecisely) indicated by Evans and show that it yields two field equations. The second field equation is algebraic in the torsion and we can resolve (...)
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  3.  26
    An Assessment of Evans' Unified Field Theory I.Friedrich W. Hehl - 2008 - Foundations of Physics 38 (1):7-37.
    Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe ϑ α and a (metric compatible) Lorentz connection Γ α β . These two potentials yield the field strengths torsion T α and curvature R α β . Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe ϑ α to be proportional to four extended electromagnetic (...)
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  4.  17
    Bianchi Identities and the Automatic Conservation of Energy-Momentum and Angular Momentum in General-Relativistic Field Theories.Friedrich W. Hehl & J. Dermott McCrea - 1986 - Foundations of Physics 16 (3):267-293.
    Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The (...)
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  5.  41
    On the Chiral Anomaly in Non-Riemannian Spacetimes.Yuri N. Obukhov, Eckehard W. Mielke, Jan Budczies & Friedrich W. Hehl - 1997 - Foundations of Physics 27 (9):1221-1236.
  6.  28
    To Consider the Electromagnetic Field as Fundamental, and the Metric Only as a Subsidiary Field.Friedrich W. Hehl & Yuri N. Obukhov - 2005 - Foundations of Physics 35 (12):2007-2025.
    In accordance with an old suggestion of Asher Peres (1962), we consider the electromagnetic field as fundamental and the metric as a subsidiary field. In following up this thought, we formulate Maxwell’s theory in a diffeomorphism invariant and metric-independent way. The electromagnetic field is then given in terms of the excitation $H = ({\cal H}, {\cal D})$ and the field strength F = (E,B). Additionally, a local and linear “spacetime relation” is assumed between H and F, namely H ~ κ (...)
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  7.  9
    Progress in Metric-Affine Gauge Theories of Gravity with Local Scale Invariance.Friedrich W. Hehl, J. Dermott McCrea, Eckehard W. Mielke & Yuval Ne'eman - 1989 - Foundations of Physics 19 (9):1075-1100.
    Einstein's general relativity theory describes very well the gravitational phenomena in themacroscopic world. In themicroscopic domain of elementary particles, however, it does not exhibit gauge invariance or approximate Bjorken type scaling, properties which are believed to be indispensible for arenormalizable field theory. We argue that thelocal extension of space-time symmetries, such as of Lorentz and scale invariance, provides the clue for improvement. Eventually, this leads to aGL(4, R)-gauge approach to gravity in which the metric and the affine connection acquire the (...)
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  8.  26
    Cartan’s Spiral Staircase in Physics and, in Particular, in the Gauge Theory of Dislocations.Markus Lazar & Friedrich W. Hehl - 2010 - Foundations of Physics 40 (9-10):1298-1325.
    In 1922, Cartan introduced in differential geometry, besides the Riemannian curvature, the new concept of torsion. He visualized a homogeneous and isotropic distribution of torsion in three dimensions (3d) by the “helical staircase”, which he constructed by starting from a 3d Euclidean space and by defining a new connection via helical motions. We describe this geometric procedure in detail and define the corresponding connection and the torsion. The interdisciplinary nature of this subject is already evident from Cartan’s discussion, since he (...)
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  9. Gesetzesstrukturen in verschiedenen Wissenschaften.Friedrich W. Hehl & Christian Heinicke - 2000 - Philosophia Naturalis 37 (2):317-350.
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