A tensor-tensor theory of gravitation

One approach to a tensor-tensor theory of gravitation is proposed as an attempt to represent Mach's principle in a consistent way. In this theory the geometrodynamic properties of General Relativity are still valid, but not necessarily its field equations. Einstein's equations may be obtained as a special case.Most of this work was developed during the author's stay in the Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México 14, D. F.     

Field approach to gravitation and its significance in astrophysics

A field modification of classical gravitational theory which is analogous to the classical electrodynamics is proposed. Within its framework it is possible to account for some types of behaviour of matter occurring under certain extreme physical conditions. Especially, the energy release in quasars and pulsars may be calculated, under some plausible physical assumptions, to obtain values comparable with the observable ones. Several astrophysical effects (e.g. the occurrence of non-thermal radiation in pulsars and quasars, etc.) find reasonable explanations within this field approach to gravitation.     

Plane-symmetric vacuum in self-creation cosmology

Vacuum field equations for the static and non-static plane-symmetric metric are obtained in self-creation theory of gravitation proposed by Barber (1982). It is shown that, in both static and non-static cases, the only plane-symmetric solution in vacuum is the empty flat space-time of Einstein's theory. It is observed that this result is quite different from that of the Brans-Dicke and other scalar-tensor theories of gravitation.     

The force-free dipole magnetosphere in nonlinear electrodynamics

Quantum electrodynamics(QED) effects may be included in physical processes of magnetar and pulsar magnetospheres with strong magnetic fields. Involving the quantum corrections, Maxwell electrodynamics is modified to nonlinear electrodynamics. In this work, we study the force-free magnetosphere in nonlinear electrodynamics in a general framework. The pulsar equation describing a steady and axisymmetric magnetosphere is derived, which now admits solutions with corrections. We derive the first-order nonlinear corrections to the near-zone dipole magnetosphere in some popular nonlinear effective theories.The field lines of the corrected dipole tend to converge on the rotational axis so that the fields in the polar region are stronger compared to the pure dipole case.     

Trials and tribulations of playing the devil’s advocate

Beginning with his student days at school and college, the author describes his training at Cambridge with special emphasis on his mentor Fred Hoyle. His early experience of participating in a controversy at Cambridge played a major role in giving him the confidence to defend his scientific ideas. All through his later life he chose areas that were not part of mainstream research. These included the steady state theory and later the quasi steady state cosmology, action at a distance, noncosmological redshifts, quantum conformal cosmology, etc. After being a founding member of the Institute of Theoretical Astronomy(IOTA) at Cambridge, the author joined the Tata Institute of Fundamental Research(TIFR) in Mumbai and later moved to Pune to set up the Inter-University Centre for Astronomy and Astrophysics(IUCAA). He briefly reviews his own work and ends by pointing out the difficulties a non-conformist scientist faces in his professional life. In the conclusion, he mentions his interests in science popularization and science fiction for which he has won awards and appreciation, including UNESCO’s Kalinga Prize.     

New alternative for general relativity theory

This paper presents a scalar-tensor theory of gravitation with a flat background metric and an arbitrary coupling function. In what concerns PPN approximation as well as the speed and polarization of the weak gravitational wave, the suggested theory coincides with GR, while in the case of the strong field of gravitation it may considerably differ from GR.     

DNA sequencing and predictions of the cosmic theory of life

The theory of cometary panspermia, developed by the late Sir Fred Hoyle and the present author argues that life originated cosmically as a unique event in one of a great multitude of comets or planetary bodies in the Universe. Life on Earth did not originate here but was introduced by impacting comets, and its further evolution was driven by the subsequent acquisition of cosmically derived genes. Explicit predictions of this theory published in 1979–1981, stating how the acquisition of new genes drives evolution, are compared with recent developments in relation to horizontal gene transfer, and the role of retroviruses in evolution. Precisely-stated predictions of the theory of cometary panspermia are shown to have been verified.     

Celestial mechanics: Past, present, future

Over all steps of its development celestial mechanics has played a key role in solar system researches and verification of the physical theories of gravitation, space and time. This is particularly characteristic for celestial mechanics of the second half of the 20th century with its various physical applications and sophisticated mathematical techniques. This paper is attempted to analyze, in a simple form (without mathematical formulas), the celestial mechanics problems already solved, the problems that can be and should be solved more completely, and the problems still waiting to be solved.     

Zum Kollapsproblem in Gravitationstheorien

In competing gravitational theories the gravitational collapse is discussed by means of a simple model of a star proposed by Einstein in 1939 (point-particle cluster). In the framework of this model the existence of circular motions of test particles for all values of radii is a criterion for the avoidance of gravitational collapse. Classical theories of gravitation in which the principle of causality is postulated additionally as much as relativistic theories of gravitation are compared with respect to the collapse behaviour. It is shown that circular motions are possible for all values of radii within the inertial-free mechanics proposed by Treder.     

Thermodynamics of 4-dimensional charged black holes in Brans-Dicke-Born-Infeld gravity theory

In this work, the charged black hole solution to the Brans-Dicke gravity theory in the presence of the nonlinear electrodynamics has been investigated. To simplify the field equations, a suitable conformal transformation has been used which transforms the Brans-Dicke-Born-Infeld Lagrangian to that of Einstein-dilaton theory with new nonlinear electrodynamics field. A new class of 4-dimensional black hole solution has been constructed out as the exact solution to the Brans-Dicke theory in the presence of the Born-Infeld nonlinear electrodynamics. The physical properties of the solutions have been studied. The black hole charge and temperature have been calculated making use of the Gauss’s law and the concept of surface gravity, respectively. Also, the black hole mass and entropy have been obtained from geometrical methods. Through a Smarr-type mass formula as a function of the black hole charge and entropy the black hole temperature and electric potential, as the intensive parameters conjugate to the black hole entropy and charge, have been calculated.     

Accretion disks in bimetric theory of gravitation. A strong field test of general relativity?

The sensitivity of accretion disk models with respect to its inner boundary conditions, being located in the strong gravity region of a highly compact central body, is used to discuss a possibility of strong field tests of gravitation via compact source observations. Within the bimetric theory of gravitation the optically thin bremsstrahlung model is calculated as an example for this possibility. Using this model to describe the innermost region of the “bimetric disk”, significant differences with respect to the corresponding results in Einstein's theory were found. The more massiv and compact “bimetric disk” radiates softer with higher luminosity.     

The millisecond pulsar and neutron star structure

Rotational stability condition is applied to the PSR 1937+214 pulsar, suggesting that its rapid rotational rate may be close to the limit of rotational stability. This application implies additional bounds on the mass, radius, and moment of inertia of neutron star models, which depend on the theory of gravitation and the equation of state of cold superdense matter. Results obtained for various equations of state and theories of gravitation are used to set limits on the surface magnetic field and slow down rate of pulsar models.     

Die Absorption der Schwerkraft und das SEELIGER-YUKAWA-Potential,Akademiker W. A. AMBARZUMJAN zum 65. Geburtstag zugeeignet

In our tetrad-formulation of the gravitation theory a potential-like interaction between the gravitationpotential and the matter-tensor is postulated. In the case of a dust-like matter from this interaction results a screening of the quasi-NEWTON ian potential by the matter-density given by a SEELIGER -YUKAWA -potential with the absorptionconstant approximately. — In the cosmological case from this screening of gravitation a finite effective gravitationradius R of the universe is resulting which radius R is given by the condition for an EINSTEIN -universe 4.     

A special-relativistic approach to gravitation and its astrophysical consequences

In the framework of Rastall's conservative program for the construction of gravitation theory we present a variant of modified classical gravitation theory based on Einstein's energy-mass equivalence principle. We pursue further the special-relativistic arguments and obtain a theory for the static spherically-symmetric gravitation field that is based only on the well-established physical principles and accounts for all experimental tests known in gravitation. Some astrophysical consequences of the modified classical gravitation theory (e.g., the non-existence of black holes, the creation of real particles in a strong gravitation field) are also discussed.     

Alternative theories of gravitation in the framework of Riemannian geometry

In the framework of Riemannian geometry alternative theories of gravitation with field equations differing from Einstein's are discussed. Examples of physically acceptable alternative theories with second, third or fourth-order field equations and without or with an additional coupling constant are given.     

Self-creation cosmological solutions

The field equations for Barber's two self-creation theories of gravitation are solved for Friedmann-Robertson-Walker space times, using perfect fluid energy-momentum tensors. Barber's first theory is discussed for the radiation dominated case, whereas cosmologies according to Barber's second sefl-creation theory are constructed for vacuum-dominated, radiation-dominated, and dust-filled cases.     

Gravitation und weitreichende schwache Wechselwirkungen bei Neutrino-Feldern Gedanken zu einer Theorie der solaren Neutrinos

The strange non-evidence of the solar-neutrino current by the experiments of DAVIS et al. postulates a fundamental revision of the theory of weak interactions and of its relations to gravitation theory. (We assume that the astrophysical stellar models are not completely wrong.) – Our paper is based on PAULI 's grand hypothesis about the connection between weak and gravitational interactions. According to PAULI and BLACKETT the (dimensionless) gravitation constant is the square of the (dimensionless) FERMI -interaction constant and according to the hypotheses of PAULI, DE BROGLIE , and JORDAN the RIEMANN -EINSTEIN gravitational metric g_ik is fusioned by the four independent WEYL ian neutrino fields (β-neutrinos and β-antineutrinos, μ-neutrinos and μ-antineutrinos). This fusion gives four reference tetrads h_i^A(x^l) as neutrino-current vectors, firstly. Then, the metric g_ik is defined by the equation g_ik = η_AB h_i^Ah_η^B according to EINSTEIN 's theory of tele-parallelism in RIEMANN ian space-times. The relation of the gravitation field theory to FERMI 's theory of weak interactions becomes evident in our reference-tetrads theory of gravitation (TREDER 1967, 1971). – According to this theory the coupling of the gravitation potential h_i^A with the matter T_ιⁱ is given by a potential-like (FERMI -like) interaction term. In this interaction term two WEYL spinor-fields are operating on the matter-tensor, simultanously. Therefore, the gravitation coupling constant is PAULI 's square of the FERMI -constant. Besides of the fusion of the RIEMANN -EINSTEIN metric g_ik by four WEYL spinors we are able to construct a conformal flat metric ĝ_ik = ϕ²η_ik by fusion from each two WEYL spinors. (This hypothesis is in connection with our interpretation of EINSTEIN 's hermitian field theory as a unified field-theory of the gravitational metric g_ik and a WEYL spinor field [TREDER 1972].) Moreover, from the reference-tetrads theory is resulting that the WEYL spinors in the “new metric” ĝ_ik are interacting with the DIRAC matter current by a FERMI -like interaction term and that these WEYL spinors fulfil a wave equation in the vacuum. Therefore, we have a long-range interaction with the radiced gravitational constant \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {\frac{{tm^2 }}{{hc}}} $\end{document} as a coupling constant. That means, we have a long-range interaction which is 10¹⁸ times stronger than the gravitation interaction. – However, according to the algebraic structure of the conform-flat this long-range interaction is effective for the neutrino currents, only. And for these neutrinos the interaction is giving an EINSTEIN -like redshift of its frequences. The characteristic quantity of this “EINSTEIN shift” is a second gravitation radius â of each body: N = number of baryons, m = mass of a baryon.) This radius â is 10¹⁸ times larger than the EINSTEIN -SCHWARZSCHILD gravitation radius a = fM/c²: But, this big “weak radius” â has a meaning for the neutrinos, only.–The determination of the exterior and of the interior “metrics” ĝ_ik is given by an “ansatz” which is analogous to the ansatz for determination of strong gravitational fields in our tetrads theory. That is by an ansatz which includes the “self-absorption” of the field by the matter. For all celestial bodies the “weak radius” â is much greater than its geometrical dimension. Therefore, a total EINSTEIN redshift of the neutrino frequences v is resulting according to the geometrical meaning of our long-range weak interaction potential ĝ_ik = ϕ²η_ik. That means, the cosmic neutrino radiation becomes very weak and unable for nuclear reactions. Theoretically, our hypothesis means an ansatz for unitary theory of gravitation and of weak interaction. This unitary field theory is firstly based on EINSTEIN 's hermitian field theory and secondly based on our reference-tetrads theory of gravitation.     

Post-newtonian gravitational radiation from binary systems in flat space-time theory of gravitation

For a previously studied theory of gravitation in flat space-time a general formula of the gravitational radiation at large distances from a system of bodies is derived. The calculations are carried out through post-Newtonian order within this theory of gravitation. A more explicit formula is given for a binary system. It agrees with the result of general relativity.