EINSTEIN, Albert.

Spielen Gravitationsfelder im Aufbau der materiellen Elementarteilchen eine wesentliche Rolle? [Do Gravitational Fields Play an Essential Role in the Structure of the Elementary Particles of Matter?] Offprint from: Sitzungsberichte der Preussischen Akademie der Wissenschaften, XX. Gesamtsitzung vom 10. April.

Berlin: Verlag der Akademie der Wissenschaften, In Kommission bei Walter de Gruyter [Reichsdruckerei], 24th April 1919.

First edition, extremely rare author’s presentation offprint (‘Überreicht vom Verfasser’), and the copy of Einstein’s son Hans Albert, of “Einstein's first attempt at a unified field theory” (Pais, Subtle is the Lord, p. 287). Once Einstein completed work on the general theory of relativity at the end of 1915, “his attention shifted to the search for a unified theory of the electromagnetic and gravitational fields, out of which he hoped to be able to explain the structure of matter. Quantum effects were to be derived from such a theory, rather than postulated ad hoc. This remained his approach for the rest of his life” (Cao, Conceptual foundations of quantum field theory, pp. 166-167). “As so often the case in relativity, the story of quantum gravity begins with Einstein himself. Soon after the final formulation of general relativity, he pointed out the need for a quantum modification of the theory. In his first paper on gravitational radiation [the 1916 paper ‘Näherungsweise Integration der Feldgleichungen der Gravitation’ (‘Approximate Integration of the Field Equations of Gravitation’)], Einstein argued that quantum effects must modify the general theory of relativity. Two years later, he reiterated this conclusion [the 1918 paper ‘Über Gravitationswellen’ (‘On Gravitational Waves’)]: ‘As already emphasized in my previous paper, the final result of this argument, which demands a [gravitational] energy loss by a body due to its thermal agitation, must arouse doubts about the universal validity of the theory. It appears that a fully developed quantum theory must also bring about a modification of the theory of gravitation.’ Einstein, writing in [the 1919 paper offered here], soon began to speculate whether gravitation plays a role in the atomistic structure of matter: ‘There are reasons for thinking that the elementary formations which go to make up the atom are held together by gravitational forces. The above reflections show the possibility of a theoretical construction of matter out of the gravitational field and the electromagnetic field alone’ In order to construct such a model of an 'elementary particle,' Einstein shows that it is necessary to modify the original gravitational field equations …The major interest of this paper is that his attention now shifted from possible quantum modifications of general relativity to the search for a unified theory of the electromagnetic and gravitational fields, on the basis of which he hoped to explain the structure of matter. Quantum effects are to be derived from such a theory, rather than postulated ad hoc. Einstein remained committed to this approach for the rest of his life: the search for a ‘natural’ mathematical extension of the general theory in the hope that such a theory would somehow explain the quantization of matter and energy” (Iyer and Bhawal, Black Holes, Gravitational Radiation and the Universe, pp. 525-526). Einstein’s work on unified field theory was inspired by James Clerk Maxwell’s success in finding a unified theory of electricity and magnetism, one of the greatest achievements of nineteenth century physics, which showed that light was a form of electromagnetic wave, and made possible modern inventios such as radio, television and the telephone. Einstein continued his attempts to devise a unified theory of gravitation and electromagnetism for the rest of his life; his contributions in this area represent about a quarter of his entire research output and half his scientific production after 1920. Although he was ultimately unsuccessful, a similar vision was realized in the decades after his death in the construction of the ‘standard model’, a unified theory of electromagnetism with the weak and strong nuclear forces (which were unknown in Einstein’s time), and efforts to incorporate gravity into the model continue to this day. RBH lists three copies. OCLC lists only one copy (none in US).

Provenance: Hans Albert Einstein (1904-73) (ink stamp and pencil notes on front wrapper). Hans Albert Einstein was a Swiss-American engineer and educator, the second child and first son of physicists Albert Einstein and Mileva Marić. He was a long-time professor of hydraulic engineering at the University of California, Berkeley.

“As early as 1909, in his fundamental paper ‘Zum gegenwärtigen Stand des Strahlungsproblems’ [‘On the current status of the radiation problem’], which resulted from a discussion with Walter Ritz Einstein remarks ‘dass des (elektrische) Elementarquantum e ein Fremdling ist in der Maxwell-Lorentzschen Elektrodynamik’ [‘that the (electrical) elementary quantum e is alien to Maxwell-Lorentz electrodynamics’]. Einstein expressed the hope that ‘die gleiche Modifikation der Theorie, welche das Elementarquantum e als Konsequenz enthält, auch die Quantenstruktur der Strahlung als Konsequenz enthalten wird’ [‘the same modification of the theory which contains the elementary quantum e as a consequence, will also contain the quantum structure of radiation as a consequence’]. Pauli (1949), in his review about ‘Einstein’s Contribution to Quantum theory,’ pointed out that though quantum theory later on deduced the quantum structure of radiation, it has not solved Einstein’s first problem, and the elementary charge ‘auch in der Quantenmechanik ein Fremdling geblieben ist’ [‘has also remained alien to quantum mechanics’]. He emphasized that just this fact had been one of the strongest arguments to Einstein against the finality of the steps leading to quantum mechanics.

“So, during his Berlin years, Einstein made it his task to find a synthesis of his general theory of relativity (GRT), and the then nascent quantum physics. In this connection, he attributed logical primacy to the relevant relativistic field theory, because it had reached a high degree of maturity in the (GRT). After all, Einstein’s general-relativistic gravitation theory is the first theory on the fundamentals of physics working with genuinely non-linear equations, and Einstein observed that such a nonlinearity is necessary for understanding the existence of the ‘discrete field-quanta.’ A linear theory allowing arbitrary superposition of fields would, without further restrictions in the form of boundary and uniqueness conditions, never lead to a discrete spectrum of solutions. But recourse to such restrictions means that the fields are held together by the operation of entities outside the scope of the theory …

“In Einstein’s view, the problem of incorporating the elementary particles into field physics involved the question of finding field-theoretical models of electrons and protons, which were the only known particles at that time. Einstein searched for solutions or general-relativistic field equations for the combined gravitational and electromagnetic fields representing mass and charge distributions with central symmetry, and he hoped there would emerge self-consistent solutions only for discrete values of the mass and charge parameters, i.e., for a ‘particle spectrum.’

“This ‘Einstein particle problem’ pursued ideas that had been developed already in the framework of the special theory of relativity and the Maxwell-Lorentz electrodynamics, for instance, in the nonlinear theory of the electromagnetic field by G. Mie and D. Hilbert. As an essential progress by the general-relativistic treatment, Einstein regarded the genuine nonlinearity of the field equations (which Mie and Hilbert had to introduce ad hoc) and full consideration of the particle dynamics in the sense of the general-relativistic problem of motion. The generalizations of the Maxwell equations considered by Mie and Hilbert contain a too small number of components for the integrability conditions to determine the particle dynamics, whereas the Einstein problem of motion in the GRT furnishers just this dynamics as a consequence of the integrability conditions for the field equations of gravitation. It is the GRT that, with its metric field, for the first time embraces inertia and gravity, that is, just those properties which are characteristic of all particles.

“Einstein in fact succeeded in driving self-consistent, gravitational and electromagnetic fields, which can be interpreted as particle models of that kind. But his success depended on a weakening of his own equations of gravitation which physically amounts to the introduction of an additional hypothetical cosmical field of the ‘Poincaré pressure.’ By this weakening, it becomes possible to set up self-consistent particle models with spherical symmetry for arbitrary centrosymmetric mass and charge distributions. In 1919 Einstein presented his result to the academy in his paper ‘Spielen Gravitationsfelder im Aufbau der materiellen Elementarteilchen eine wesentliche Rolle?’ His answer to the question says that, in his particle models, the electrical field energy contributes ¾ and the gravitational energy ¼ of the total energy.

“Einstein’s first discourses on the particle problem in the GRT were closely related to the 1917/18 papers in which he laid the foundations of relativistic cosmology. In his Academy report ‘Kosmologische Betrachtungen zur allgemeinen Relativitätstheorie’ [‘Cosmological considerations on the general theory of relativity’] (1917) Einstein had, by introducing the term λg_μν, with the ‘cosmological constant’ λ, extended his equations of gravitation to his cosmological equations of gravitation,

R_μν – ½ g_μνR + λg_μν = – κ T_μν . (*)

He could show that these equations permit as a particular solution with λ > 0 and constant (positive) mass density, a statical model of the universe representing a closed spheric (or elliptic) three devotional Riemannian space …

“In his paper of 1919 about the role of gravitation in the structure of elementary particles, Einstein also interpreted the cosmological constant λ as the universal ‘Poincaré’ pressure’, which, according to a hypothesis of H. Poincaré, is to guarantee the stability of Lorentz’s electrons against their own repulsion forces. Einstein’s ideas concerning this matter partly resulted from a controversial discussion with E. Schrödinger (1918) about the gravitational energy in the GRT and the structure of the energy tensor” (Treder, pp. 149-151).

Indeed, Schrödinger had pointed out another way of treating the cosmological constant: moving it from the left-hand side of equation (*), where it represents a contribution to space-time curvature, to the right-hand side, where it represents a contribution to the energy-matter distribution. Then it would correspond physically to a kind of cosmic pressure. Schrödinger believed this might be the pressure postulated by Poincaré to maintain the stability of charged particles: an electric charge on the surface of a sphere creates a force pushing outwards, so without any opposing force the charged sphere would explode outwards.

Einstein never liked the cosmological constant. In the present paper, he acknowledged that his introduction of the cosmological constant was “gravely detrimental to the formal beauty of the theory” (Cambridge Companion to Einstein, p. 257).

Boni-Russ-L. 111; Schilpp 123; Weil 106. Treder, ‘Antimatter and the particle problem in Einstein’s cosmology and field theory of elementary particles (A historical essay on Einstein’s work at the Akademie der Wissenschaften zu Berlin),’ Astronomische Nachrichten 296 (1975), pp. 149-161).

Large 8vo (254 x 182 mm), pp. 349-356. Original printed wrappers. A very fine copy.

Item #6166

Price: $3,250.00