222 DOC. 10 RESEARCH NOTES

[43](p1

and

cp2

are

defined

on

[p. 16].

[44][Eq.

47] and

[eq.

48]

are

identities

produced

by

twice

differentiating

the

identity

yiKgiK

=

4, to

be

used

in

finding

an

alternative

expression

for

cp2.

[45]The term "gravitation

tensor"

suggests

that Einstein

is

seeking

a

tensor,

formed from

the metric

gik

and its derivatives,

for

gravitational

field

equations.

This

interpretation

is

prob-

lematic, however,

because

[eq.

49]

contains

only

first-order derivatives of the

metric,

which

makes

it

unsuitable for

gravitational

field

equations.

An

alternative

reading

is

that

[eq.

49]

is

a

candidate for the

stress-energy tensor

of the

gravitational field,

in

accordance with the older

usage

of the

term

"tensor" for second-rank

structures representing stress-energy-momentum.

The

divergence

[eq.

50]

would then

figure

in

the

energy-momentum

conservation

law.

[p.

18]

[connects

p. 17]

-p2

=

I

d

(

G

a+\

2

?/kTi

3Y"

x

«+,)G*+5

I

StetV

dg

po

V

dx.

1

^Yjk

^£po

a+^

d

3Y,k

^

=

(O+1)C°*5X«IKT Y

---I- G

X

I

8i«Y

dxv

dx

dx dx

v /

Selbstverst.,

weil

dG/dxv

Vektor zweiter

Art.

dx

Subst.

müssen

mehr

eingeschränkt

werden

"

/ /

J /

d

d [46]

^r^o^vpYa)(KidKKe^8e^

dx

Ke'Tfe'e')

[eq. 51]

Yl

171

Im

=

Zjhmdxl

Y, dxm

+

Transformation unendlich klein

1

K-e

i=5' k=e'