448
DOCS.
440,
441 JANUARY
1918
for
any system
that
remains infinite
at
infinity.
This
difficulty can
be avoided
by
replacing
the
boundary
condition at
infinity
with
the
condition
of closure.
But
this
condition cannot be realized
without the
supplementary term,
with the
given
structure
for
the
energy
tensor of matter.[3]
De Sitter’s
matter-free
solution
is not
admissible,
in
my
view,
because
at
in-
finity
it
is
not free of
singularities (with
the static
and
spatio-spherical
coordinate
choice,
g44 =
0
on one surface).
This
actually
means
the
localization
of
all
matter
on one
surface.[4] De
Sitter’s
consideration,
in
particular, strengthens
my opinion
that,
on
the
basis of
the additional
term,
no
guv-world
exists
without
matter
and
without
singularities.
This conduct
by
the
equations
is
required
from
the stand-
point
of
the
general
theory of relativity
(complete dependence
of
the
guv-system
on
the
matter).[5]
With best
regards,
yours truly,
A. Einstein.
441.
From Wilhelm von Siemens
Berlin W.
9,
4 Voss
Street,
21 January 1918
Board of Trustees
of
the Kaiser Wilhelm
Institute
of
Physics.
To His Honor
the
Director of
the
Kaiser
Wilhelm
Institute
of
Physics,
Professor
Einstein, locally.
The
members
of
the Board of Trustees of
the Kaiser Wilhelm Institute
of
Physics
have declared
their
approval
of
the enclosed
draft
contract
with
Dr. Erwin
F.
Freundlich,
subject to
the
omission
of
§2
as
suggested
by Privy
Councillor
Professor
Nernst.[1]
At
the
same
time,
the
Board
of
Trustees has
authorized
Your
Honor
to close
the
contract
with
Dr.
Freundlich
on
your
part.
I
humbly
look forward to
kind information
about
the final execution
as
well
as
about
where
the
funds
placed
at Dr. Freundlich’s
disposal
should be
remitted.
Chairman
of
the
Board of Trustees
von
Siemens.
Recipient’s
note: “Answered
on
1 February. E[instein]."