EINSTEIN S RESPONSE TO THE NEW DYNAMICS 451to it that Einstein's papers in Berlin were saved and sent to the Quai d'Orsay by
French diplomatic pouch. Furniture from the home on the Haberlandstrasse was
prepared for shipment (and arrived safely in Princeton some time later). Einstein
traveled. He lectured several times in Brussels; he went to Zurich, where he saw
his son Eduard for the last time; he went to Oxford, where on June 10 he gave
the Spencer lecture, which I have often quoted [El7].
Two days later, he lectured again in Oxford and on June 20 was in Glasgow
to give the first Gibson lecture, dealing with the origins of general relativity
[E20].* During a brief second visit to England, in July, he met with Churchill
and other prominent personalities. Meanwhile, offers for academic positions
reached him from several sides. Weizmann asked him to come to Jerusalem. Ein-
stein refused outright because he was highly critical of the Hebrew University's
administration. He was approached by Leiden and Oxford. Offers for chairs came
from Madrid and Paris.
In the midst of these happenings, Einstein and Mayer managed to do a little
physics and complete two papers on semivectors, which they sent from Le Goq to
Holland for publication in the Royal Dutch Academy proceedings [E21, E22].
These were sequels to a joint paper they had finished a few days before Einstein
had set off for Pasadena [E23]. This work was stimulated by Ehrenfest's insis-
tence on a better understanding of the relation between single-valued and double-
valued representations of the Lorentz group [E23]. In response, this is what they
did. Associate a 2 X 2 matrix X to a special relativistic 4-vector ACM:
each of the two columns of X transforms into itself. These columns, called semi-
vectors by Einstein and Mayer, are double-valued representations of the proper
Lorentz group; up to linear combinations they are spinors.** Not all of this was
new [K5], but it was nice work, done independently. They went on to relate semi-
*A report in The New York Times [N2] that Einstein was present at a Zionist Congress in Prague
in August is incorrect.
**The detailed connection between semivectors and spinors was discussed by Bargmann [B8].where A and B are complex 2X2 matrices. This transformation is length-pre-
serving if det^4 detfi = 1. Scale in such a way that dttA = 1; then det^4 = det5
= 1. With these constraints, Eq. 25.2 represents the general complex Lorentz
group excluding reflections; reality preservation demands that B = A'. Under the
transformation
so that detX equals the vector's (invariant length)^2. Transform X by
(25.2)(25.3_
(25.1)