3 5 8 D O C U M E N T 4 2 0 J A N U A R Y 1 9 2 3 . (16) Outside of the charged masses ( ), however, equations (3) of Riemannian geometry apply again. But within the charged masses the generally covariant deriv- ative of the metric tensor does not vanish. It is here that this theory differs from the one of the independent electromagnetic field. It is highly interesting that according to the theory developed here, the two signs of electricity do not appear equivalently.[23] The reason lies in the connection between gravitational field and electromagnetic field in equation (7).[24] We shall only be able to decide whether the two invariants and will suffice to describe the electron after first calculating out the centrally symmetric static problems [25] the interesting problem is this: whether such singularity-free solutions exist for both electric signs. Singapore. January 1923.[26] 418. Calculations on Back Pages of Travel Diary [on or around 9 January 1923][1] [Not selected for translation.] 419. Fragment and Calculation on the General Theory of Relativity [ca. January 1923] [Not selected for translation.] 420. To Svante Arrhenius[1] Near Singapore, 10 January 1923 Esteemed Colleague, The news about the award of the Nobel Prize reached me via telegraph on the Kitano Maru shortly before my arrival in Japan.[2] I am very pleased—among other reasons, because the reproachful question: Why don’t you get the Nobel Prize? can gαβ μ 6 7 --( - δμ αiβ δμ βiα) + 4 7 --gαβiμ - – = [p. 9] iα 0= I1 I2