D O C . 1 3 C O M M E N T O N M Y P A P E R 3 5 Published in Preußische Akademie der Wissenschaften (Berlin). Physikalisch-mathematische Klasse. Sitzungsberichte (1923): 76–77. Submitted 12 April 1923, published 15 May 1923. A manuscript is also available ([1 028]). [1]Einstein 1923e (Vol. 13, Doc. 425). [2]In the manuscript, the word “formal” is interlineated. [3]For the significance of the symmetry condition, see “On the General Theory of Relativity” (Vol. 13, Doc. 417), note 4, and Einstein 1923e (Vol. 13, Doc. 425), note 8. [4]The point of the approach is to start from a manifold that is from the outset only endowed with a symmetric affine connection . A metric field is then derived as the symmetric part of the sec- ond-rank curvature tensor multiplied by some scale factor λ see Einstein 1923e (Vol. 13, Doc. 425), eqs. (11), (12). [5]This result was obtained in the calculations contained in Einstein’s Japan Travel Diary (see Vol. 13, Doc. 418, [p. 44v]), and published in Einstein 1923e (Vol. 13, Doc. 425), eq. [24]). [6]The field equations (13) can be found on [p. 43] of the Japan Travel Diary (Vol. 13, Doc. 418), but are not given explicitly in Einstein 1923e (Vol. 13, Doc. 425). There it is only indicated how eq. (14) would be obtained from eq. (4), and the gravitational part is only discussed for the special case of vanishing electromagnetic field. The electromagnetic part of (13) is given in Einstein 1923e (Vol. 13, Doc. 425), eq. (24), and discussed for the approximate case of weak fields. [7]The variational integral (14) was written down together with the field equation (13) on [p. 43] of Vol. 13, Doc. 418. It is also investigated in the calculations of Doc. 31. [8]Einstein had written: “It is remarkable that according to this theory the positive and negative electricity cannot only be different with respect to the sign” (“Bemerkenswert ist, daß nach dieser Theorie die positive und negative Elektrizität keineswegs bloß dem Vorzeichen nach verschieden sein können” Einstein 1923e [Vol. 13, Doc. 425], p. 38). In a letter to Arthur S. Eddington of 14 February 1923 (Vol. 13, Doc. 430), Einstein elaborated on the argument. A very similar argument for the invari- ance of the theory against a change of based on the invariance of was given by Weyl in Doc. 36. [9]The manuscript ends with the deleted sentence: “Letzteres ist der Zweck dieser Notiz.” Γμν α rik ϕkl Rkl gkl ϕkl +=
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