On geometrodynamics with tetrad fields

In this paper, we extend Kucha's analysis [1] to geometrodynamics driven by sources of arbitrary spin: starting from a given matter action added to ADM's gravitational action, we derive the corresponding Hamiltonian. We next calculate the strong value of the Poisson brackets of the constraints. Our general derivation leads to Deser-Isham [9] and Dirac's results [4] when applied to the particular cases of pure geometrodynamics and geometrodynamics with a spin-1/2 field.Aspirant du Fonds National Belge de la Recherche Scientifique.     

Einstein-Maxwell null fields with a null current distribution

Null Einstein-Maxwell charge-free fields such that the propagation vector is a scalar multiple of a gradient are not determined uniquely by the geometry of the space-time. The metric for space-times admitting such exceptional fields can always be transformed to the Wyman-Trollope form. This same result follows if there is a non-vanishing null current density associated with the field.     

On the permanence of the null character of Maxwell fields

A critical review of known results about the permanence conditions for the null character of the solutions to the (vacuum) Maxwell equations, is presented. Concomitants of the electromagnetic field and the metric tensor are constructed, which give the principal directions of the field in covariant form. The known permanence conditions are generalized in order to includeall the (local) null fields; the above concomitants allow these conditions to be explicitly formulated in terms of the electromagnetic field.Supported in part by Conselleria de Cultura, Educació i Ciència de la Generalitat Valenciana.     

Colored null flags and para-Fermi fields

An inverse problem of deriving the concept of quantized fields from a certain observable conserved current is investigated. It is found that a natural framework in which to attack the problem is provided for by what we shall call Green's ansatz of null decomposition of the current. The null decomposition naturally yields a set ofcolored null flags hoisted at each space-time point, a null flag comprizing a real null vector and an associated real null six-vector, and is invariant under all permutations of colors. From the fact that to any null flag there corresponds a two-component spinor it follows that the color permutation group is extended tocolor groups O(p) orU(p), wherep is the number of null flags considered. It is shown that para-Weyl (para-Fermi) fields of orderp2 can be deduced from the (chiral) set ofp colored null flags, and that the color groupU(p) is singled out that functions as the gauge group of para-Fermi theory.     

Gravitational fields near space-like and null infinity

Near space-like infinity an initial value problem for the conformal Einstein equations is formulated such that: (i) the data and equations are regular, (ii) space-like and null infinity have a finite representation, with their structure and location known a priori, and (iii) the setting relies entirely on general properties of conformal structures.A first analysis of this problem shows that the solutions develop in general a certain type of logarithmic singularity at the set where null infinity touches space-like infinity. These singularities form an intrinsic part of the solutions' conformal structure. Conditions on the free initial data near space-like infinity are derived which ensure that for solutions developing from these data singularities of this type cannot occur.     

Einstein-Maxwell null fields with non-zero twist

It is shown that iff ^a is the propagation vector of a null Maxwell field in a space-time with metric⁰ g _ab , then it is also the propagation vector in the space-timeg _ab =⁰ g _ab +2fi _a i _b . This result, together with the Robinson metric for vacuum gravitational fields and Hughston's generalization to radiating fields, is used to set up equations for combined gravitational and electromagnetic null-fields with special reference to fields with non-zero twist.     

Third-order geometrical null symmetries of gravitational fields

The first-, the second-, and the third-order null Killing vectors in a gravitational field are explored separately. When an algebraically special Petrov-type free gravitational field isaligned with a source-free (nonnull/null) electromagnetic field, their common propagation vectorl ^a is shown to be a third-order null Killing vector field ( _{l l l} g _ab = 0, _{l l} g _ab 0). When the two fields arenot aligned, the necessary and sufficient conditions for the existence of a third-order null symmetry are obtained in Newman-Penrose formalism.     

Canonical geometrodynamics and general covariance

By extending geometrodynamical phase space by embeddings and their conjugate momenta, one can homomorphically map the Lie algebra of space-time diffeomorphisms into the Poisson algebra of dynamical variables on the extended phase space.     

Einstein-maxwell null fields and extended massless particles with helicity

The concept of extended elementary particles proposed by the author in previous papers is briefly outlined in a slightly modified form. In this framework special Einstein-Maxwell null fields are interpreted as extended massless particles with helicity. A model of extended photons is proposed.     

The Superspace of geometrodynamics

Wheeler’s Superspace is the arena in which Geometrodynamics takes place. I review some aspects of its geometrical and topological structure that Wheeler urged us to take seriously in the context of canonical quantum gravity. I dedicate this contribution to the scientific legacy of John Wheeler.     

Quantum insights from null-strut geometrodynamics

We discuss quantum insights due to the null-strut formalism. These insights deal primarily with two topics: the formalism of a theory of canonical simplicial quantum gravity based on the geometrodynamic duality of null-strut calculus, and the natural implementation of spinors and spin networks in null-strut calculus.     

Principal null directions of the neutrino and derived Maxwell fields

Bineutrino fields are constructed from neutrinos described by the two-component Weyl equation. If we demand that the bineutrino fields fulfil the set of Maxwell equations, we have a classical version of the “neutrino theory of light”. With the help of the spin coefficient formalism, it is established that the energy tensor of the neutrino fields cannot be positively definite, and that the principal null direction of the bineutrino Maxwell fields does not coincide with the principal null direction of the underlying neutrino fields.     

Canonical quantization of gravity and quantum geometrodynamics

A representation in the form of the Faddeev-Popov path integral is constructed for solving the equations of quantum geometrodynamics (QGD). It is shown that QGD is equivalent to canonical quantization of gravity in a unitary gauge. Given the state of the gravitational field on the initial Cauchy hypersurface, a wave function of closed universe is constructed so that it satisfies the QGD equations. Using the principles of canonical quantization, a probabilistic interpretation of this wave function is constructed in a fashion close to Everett's concepts of quantum mechanics.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 37–51, March, 1986.     

Topological geometrodynamics and the solar neutrino problem

A solution of the solar neutrino problem based on certain differences between T(opological) G(eometro) D(ynamics) and the standard model of the electroweak interactions is proposed. First, TGD predicts the existence of a right-handed neutrino inert with respect to ordinary electroweak interactions. Second, the generalization of the massless Dirac equation contains terms mixing differentM ⁴ chiralities, unlike the ordinary massless Dirac equation. This and the observation of anticorrelations of the solar neutrino flux with sunspot number suggest that solar neutrinos are transformed to right-handed neutrinos on the convective zone of the Sun. Third, the compactness ofCP ₂ implies topological field quantization: space-time decomposes into regions, topological field quanta, characterized by a handful of vacuum quantum numbers. In particular, there are topological obstructions for the smooth global imbeddings of magnetic fields and the decomposition of the solar magnetic field into flux tubes is predicted. Finally, every electromagnetically neutral mass distribution is accompanied by a long-rangeZ ⁰ vacuum field. If the vacuum quantum numbers inside the flux tubes of the solar magnetic field are considerably smaller than in the normal phase, theZ ⁰ electric force becomes strong and implies Thomas precession for the spin of the lefthanded component of the neutrino. As a consequence, left-handed neutrinos are transformed to right-handed ones and the process is irreversible, since righthanded neutrinos do not couple toZ ⁰.