612 DOCS. 588-590 JULY
1918
here,
also in conformance with
my assumptions
to
your
T£
+
tv.[5]
But
with other
demands
on me
and
reduced
productivity,
it
is
all
just
going very
slowly.
Very
truly
yours,
Klein.
589. To
Felix Klein
[Ahrenshoop,]
22 July
1918
Highly
esteemed
Colleague,
It
is
very good
that
you
want
to clear
up
the
formal
meaning
of
tva.[1]
For
I
must
admit that the
derivation of
the
energy
conservation law for
the
field
and
matter
together
seems
unsatisfactory,
from the
mathematical
point
of
view,
making
the formal characterization
of
tva
not
at all feasible.
I
would also
like
to note
that
the introduction
of
the Hamilton
function
0* for
the
guv-field
against
the
invariant
©
has
another
advantage
apart
from
plain
cal-
culational
simplicity.[2]
In Schwarzschild’s
sphere
problem[3]
it
was
demonstrated
that
at
the
surface
of
the
sphere
the
continuity
of
the
guv's,
but
not of
the
guv's,
must be
required,
which
latter
quantities
change discontinuously
at
the
bound-
ary.
Hence 0* remains
finite throughout,
even
at
the
sphere’s surface,
whereas
0
becomes infinite.
Without
the introduction
of 0* it
might
be difficult to
justify
being
able to make do with
requiring
the
continuity
of
guv
alone.
With best
regards, yours very truly,
A.
Einstein.
590.
From Hedwig
and Max Born
[Berlin,]
28 July 1918
“The
bad-this
maxim
is
firmly
fixed-
Is
always
the
good
from which
one
desists!”
Improve yourselves, you lazy
Ahrenshoopers,
and desist
no more
from
the
good,
namely,
from
writing!
Report
rather
on
what
pleasing
thoughts
the blue
sky
and
“boundless”
sea
instill in
you!
And
come
back
soon,
plump
as
dumplings,
to
the
delight
of
your
Borns.
Authors’
caption
on verso:
“Vision
by
the
lonely
and
pining
Grunewalders.”