String Theory: Preface

We develop the general theory of relativity in a formalism with extended causality that describes physical interaction through discrete, transversal and localized pointlike fields. The essence of this approach is of working with fields defined with support on straight lines and not on hypersurfaces as usual. The general relativity homogeneous field equations are then solved for a finite, singularity-free, point-like field that we associate with a `classical graviton'. The standard Einstein continuous formalism is retrieved by means of an averaging process, and its continuous solutions are determined by the chosen imposed symmetry. The Schwarzschild metric is obtained by imposing spherical symmetry on the averaged field.

https://iopscience.iop.org/article/10.1088/0264-9381/16/2/023/pdf

Discrete and finite general relativity

We introduce a classical field theory based on a concept of extended causality that mimics the causality of a point-particle Classical Mechanics by imposing constraints that are equivalent to a particle initial position and velocity. It results on a description of discrete (pointwise) interactions in terms of localized particle-like fields. We find the propagators of these particle-like fields and discuss their physical meaning, properties and consequences. They are conformally invariant, singularity-free, and describing a manifestly covariant $(1+1)$-dimensional dynamics in a $(3+1)$ spacetime. Remarkably this conformal symmetry remains even for the propagation of a massive field in four spacetime dimensions. The standard formalism with its distributed fields is retrieved in terms of spacetime average of the discrete fields. Singularities are the by-products of the averaging proccess. This new formalism enlightens the meaning and the problems of field theory, and may allow a softer transition to a quantum theory.

Discrete fields on the lightcone

The use of proper time as a tool for causality implementation in field theory is clarified and extended to allow a manifestly covariant definition of discrete fields proper to be applied in field theory and quantum mechanics. It implies on a constraint between a radiation field and its sources, valid in principle for all fundamental interactions and with a solid experimental confirmation for the electromagnetic one. Some results of its applications to an abelian classical theory (electrodynamics taken as a first example), and with the discrete field being regarded as a classical representation of the field quantum (photon) are anticipated in order to illuminate the physical meaning and the origins of gauge fields and of their symmetries and singularities. They are associated to a loss of field-source coherence.

Discrete gauge fields

Questioning the experimental basis of continuous descriptions of fundamental interactions we discuss classical gravity as an effective continuous first-order approximation of a discrete interaction. The sub-dominant contributions produce a residual interaction that may be repulsive and whose physical meaning is of a correction of the excess contained in the continuous approximation. These residual interactions become important (or even dominate) at asymptotical conditions of very large distances from where there are data (rotation curves of galaxies, inflation, accelerated expansion, etc) and cosmological theoretical motivations that suggest new physics (new forms of interactions) or new forms (dark) of matter and energy. We show that a discrete picture of the world (of matter and of its interactions) produce, as an approximation, the standard continuous picture and more. The flat rotation curve of galaxies, for example, may have a simple and natural explanation.

Gravity and Antigravity with Discrete Interactions: Alternatives I and II

We do a critical review of the Faraday-Maxwell concept of classical field and of its quantization process. With the hindsight knowledge of the essentially quantum character of the interactions, we use a naive classical model of field, based on exchange of classical massless particles, for a comparative and qualitative analysis of the physical content of the Coulomb's and Gauss's laws. It enlightens the physical meaning of a field singularity and of a static field. One can understand the problems on quantizing a classical field but not the hope of quantizing the gravitational field right from General Relativity.

Classical Fields and the Quantum Concept

What is the nature - continuous or discrete - of matter and of its fundamental interactions? The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for the validity of a mathematical description of fundamental physics in terms of continuum fields are a natural outcome of discrete fields with discrete interactions. Two demarcating points (a near and a far) define a domain where no difference between the discrete and the standard continuum field formalisms can be experimentally detected. Discrepancies, however, can be observed as a continuous-interaction is always stronger below the near point and weaker above the far point than a discrete one. The connections between the discrete scalar field and gravity from general relativity are discussed. Whereas vacuum solutions of general relativity can be retrieved from discrete scalar field solutions, this cannot be extended to solutions in presence of massive sources as they require a true tensor metric field. Contact is made, on passing, with the problem of dark matter and the rotation curve of galaxies, with inflation and the accelerated expansion, the apparent anomaly in the Pioneer spacecraft acceleration, the quantum Hall effect, high-$T_{c}$ superconductivity, quark confinement, and with Tsallis generalized one-parameter statistics as some possible manifestation of discrete interaction and of an essentially discrete world.

Discrete scalar field and general relativity

The physical meaning, the properties and the consequences of a discrete scalar field are discussed; limits for the validity of a mathematical description of fundamental physics in terms of continuous fields are a natural outcome of discrete fields with discrete interactions. The discrete scalar field is ultimately the gravitational field of general relativity, necessarily, and there is no place for any other fundamental scalar field, in this context. Part of the paper comprehends a more generic discussion about the nature, if continuous or discrete, of fundamental interactions. There is a critical point defined by the equivalence between the two descriptions. Discrepancies between them can be observed far away from this point as a continuous-interaction is always stronger below it and weaker above it than a discrete one. It is possible that some discrete-field manifestations have already been observed in the flat rotation curves of galaxies and in the apparent anomalous acceleration of the Pioneer spacecrafts. The existence of a critical point is equivalent to the introduction of an effective-acceleration scale which may put Milgrom's MOND on a more solid physical basis. Contact is also made, on passing, with inflation in cosmological theories and with Tsallis generalized one-parameter statistics which is regarded as proper for discrete-interaction systems. The validity of Botzmann statistics is then reduced to idealized asymptotic states which, rigorously, are reachable only after an infinite number of internal interactions . Tsallis parameter is then a measure of how close a system is from its idealized asymptotic state.

de Souza

Papers

Classical Fields and the Quantum Concept

Discrete fields on the lightcone

Gravity and Antigravity with Discrete Interactions: Alternatives I and II

Discrete scalar field and general relativity

Discrete fields, general relativity, other possible implications and experimental evidences