DOCS.
644,
645 NOVEMBER
1918
687
the
generation
of
cathode
rays appealed
to
me
very
much.[3]
It
is
also
good
that
Mr.
Bär
has
taken
verification
of
the
Viennese results
firmly
in
hand.[4]
Ehrenhaft
is
still
defending
himself
heftily.[5]
Cordial
regards, yours,
Einstein.
645. From Felix Klein
Göttingen, 5
November
1918
Esteemed
Colleague,
The
vector
character
of
my no
(formula
(11)
of the
new note[1]) can
be derived
through calculation,
by working
from
the
way
the
invariant
K
is constructed.[2]
As
follows
(whereupon
I
note in advance
that
Dr.
Vermeil[3]
helped
me
very
considerably
with the
complicated calculations):
1)
The
element
Kp°
in
(11)
is
in and of itself
a
vector
component
and should be
disregarded
henceforth.
2)
dK/dguvpo
is,
because of
the
special
nature of
K,
a
term
dependent only
on
the
guv's
and hence
a
mixed
tensor
which
may
be called
Kpouv.[4]
3)
In
the third
term
of
nowhich
is
now
calledKp°ppt/we
replace
ppiJ
with
the
corresponding
covariant derivative:
4)
a?
=
p»;

(roT"
+ rT").
The
term
that
emerges,
Af
.
again
has the desired
vector
character.
The
component
of
na
remaining
to be
analyzed is:
dK
+
1
d(y/gKp
P^A^(r^
+
r^),
dga
y/g
dwp
or
arranged
otherwise, by carrying
out
the
differentiation:
PLLV
\dK%
,
Ko,d\og
yß
\
dwp w
dwp

kptvt

Kpcrr
*yti/
a
pp pi/
dK
dg;
Here,
now, according
to
Vermeil’s
calculation,
the
expression
enclosed in
braces
is
nothing
but the
covariant derivatives summed
over
p:
Kpouv,p=Bouv