D O C U M E N T 4 2 5 O N G E N E R A L R E L A T I V I T Y 7 1 3 Published in Preußische Akademie der Wissenschaften (Berlin). Physikalisch-mathematische Klasse. Sitzungsberichte (1923): 32–38. Submitted 15 February 1923, published 12 March 1923. For a man- uscript, see Doc. 417. [1]For the role and the meaning of the metric tensor in the original formulation of the general theory of relativity, see Einstein and Grossmann 1913 (Vol. 4, Doc. 13), §§2–3, and Einstein 1914o (Vol. 6, Doc. 9), §§1–2. For a historical and systematic discussion of the role of the connection as a primary mathematical concept in the foundation of relativity theory, see Stachel 2007. [2]On the desirability of understanding an alleged Wesenseinheit between the gravitational and electromagnetic field, see also the remarks in the opening paragraph of Einstein and Grommer 1923a, p. 6 (Doc. 12). [3]In his Princeton lectures, in the discussion of covariant differentiation and of the derivation of the Riemannian curvature tensor in terms of an affine connection on the basis of the concept of par- allel transport, Einstein also credited both Levi-Civita and Weyl for the introduction of the mathemat- ical concepts (see Einstein 1922c [Vol. 7, Doc. 71], p. 45). See also a similar remark in Doc. 417 and its note 3. [4]See Weyl 1918a, 1918b. Weyl had sent proofs of the latter article to Einstein in March 1918 (see Hermann Weyl to Einstein, 1 March 1918 [Vol. 8, Doc. 472] see also its note 3 for a brief character- ization of Weyl’s unified theory as well as further references). [5]For Einstein’s objections, see, e.g., his letter to Weyl of 15 April 1918 (Vol. 8, Doc. 507). One frequently voiced argument against Weyl’s theory was the so-called measuring rod objection (“Maßstab-Einwand”) see, e.g., Einstein 1918g (Vol. 7, Doc. 8). [6]See Eddington 1921a and 1923, chap. 7, sec. 2. [7]See Eddington 1921a, p. 111. [8]For Einstein’s probable discussion with Elie Cartan about torsion and the associated asymmetric connections during his Paris visit, see Doc. 417, note 4 for calculations involving the assumption of an asymmetric connection, see Doc. 418, pp. [47], [42v]. [9]See, e.g., Einstein 1922c (Vol. 7, Doc. 71), p. 47. [10] should be , as implied by eq. (5). [11]For a discussion of Einstein’s criteria for a successful unification, see Bergia 1993 and Lehm- kuhl 2009. [12]An otherwise similar ansatz on p. [46] of Doc. 418 lacks the factor λ. [13]Compare the introduction of the quantities and on [p. 44v] of Doc. 418 see also its note 58. [14]Most of the equations on this page can also be found in Doc. 418, [p. 44v] see its note 59. [15]Doc. 417 ends with a similar comment on the spherically symmetric solutions see its note 25. [16]Einstein elaborates on this point in Doc. 430. He later retracted his claim in Einstein 1923h. [17]On 22 January 1923, Einstein entered in his travel diary “Arbeit über Gravitation und Elektri- zität endgültig aufgeschrieben” (Doc. 379, p. 29). He was aboard the Haruna Maru from 29 Decem- ber 1922 until 1 February 1923. Since Einstein would return to Berlin only on 21 March, the paper was presented to the Prussian Academy on Einstein’s behalf by Max Planck. Its abstract, as given in the Sitzungsberichte, reads: “Es wird gezeigt, wie man durch Anwendung des Hamiltonschen Prin- zips auf Grund der Eddingtonschen Auffassung zu einer vollständigen Theorie von Gravitation und Elektrizität gelangen kann, welche unserem bisherigen Wissen gerecht wird. Diese Theorie ist dadurch gegenüber den bisherigen Theorien ausgezeichnet, daß ihre Hamiltonsche Funktion nicht aus logisch voneinander unabhängigen Summanden besteht” (Preußische Akademie der Wissenschaften (Berlin). Physikalisch-mathematische Klasse. Sitzungsberichte (1923), p. 26). For further historical discussion of this paper, see Vizgin 1994, pp. 188–197 Mastrobisi 2002 Goenner 2004, sec. 4.3.2 and Sauer and Majer 2005. Skl gkl #μν fμν