Abstract

Relativistic localizing systems that extend relativistic positioning systems show that pseudo-Riemannian space-time geometry is somehow encompassed in a particular four-dimensional projective geometry. The resulting geometric structure is then that of a generalized Cartan space (also called Cartan connection space) with projective connection. The result is that locally non-linear actions of projective groups via homographies systematically induce the existence of a particular space-time foliation independent of any space-time dynamics or solutions of Einstein’s equations for example. In this article, we present the consequences of these projective group actions and this foliation. In particular, it is shown that the particular geometric structure due to this foliation is similar from a certain point of view to that of a black hole but not necessarily based on the existence of singularities. We also present a modified Newton’s laws invariant with respect to the homographic transformations induced by this projective geometry. Consequences on galactic dynamics are discussed and fits of galactic rotational velocity curves based on these modifications which are independent of any Modified Newtonian Dynamics (MOND) or dark matter theories are presented.

Highlights

  • In this paper, we present consequences of a local projective geometry of spacetime

  • The local spacetime geometry is Euclidean and the changes of scale are due to the additional transformations that allow to pass from the Poincaré group to the Weyl group

  • The fits presented in this paper, based on the modified Newton’s laws (31) were obtained from very simplified data and data processing

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Summary

Introduction

We present consequences of a local projective geometry of spacetime. This geometry is strongly suggested based on only purely metrological characteristics of systems of relativistic localization of events in spacetime [1,2,3]. As a result, considering in particular the normal Riemann coordinates that always exist on a (pseudo-)Riemannian manifold, any change of Riemann normal coordinates attached to a given fixed point is no longer only linear but can be homographic The mathematical formalism was presented in a very little synthetic form and difficult to access except for some mathematicians in the field This projective geometry that relativistic localizing systems unveil is truly inherent in spacetime and somehow superimposes itself on the underlying pseudo-Riemannian geometry. We conclude in the last section in which we indicate in particular other motivations that led to the publication of this note

Some Elements of Terminology
The Homographies on Projective Space
The Hyperbolic and “Pseudo-Hyperbolic” Spaces
The Foliations
A Particular Discontinuous Projectively Invariant Lorentzian Metric
Introduction—Invariance of Families of Tensors or Tensors Fields
General Framework for Invariant Projective Vector Fields
Invariant Projective Vector Fields on Ω
A Particular Modified Newton’s Law
The Isotropic Class
The Anisotropic Class
Interpretation of Times and Distances
Modified Newton’s Laws
The Modified Anisotropic Newton’s Law
The “Central Zone” and a Structure Similar to a Black Hole
The Fits of Rotational Velocity Curves and the Fitting Procedure
Conclusions
Results

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