February 11, 2005 12:22 CET
PROOF OF THE TETRAD POSTULATE FROM
FUNDAMENTAL MATRIX INVERTIBILITY OF THE TETRAD.
Note that this proof is valid for the vielbein of any dimension,
in four dimensions it becomes the vierbein or tetrad. The Leibnitz
Theorem holds for covariant differentiation as discussed by Carroll.
It is nice to see that the Leibnitz Institute of the Bavarian Academy
of Sciences in Munich has visited www.aias.us many times. The tetrad
postulate is more properly the Cartan tetrad postulate. It is the
geometrical basis of the Evans wave equation and Evans Lemma of geneally
covariant unified field theory. Fuller details of the different
proof of the tetrad postulate is given in the appendices of my new book.
MWE
http://www.atomicprecision.com/new/atetradpostulatefromfirstprinciples.pdf
with comments (in blue) by Gerhard W. Bruhn, Darmstadt University of Technology
Consider the following basic properties of the tetrad:
qνb qbν = 1 (1)
WRONG! The result of that double summation is dimension dependent. In spacetime
of dimension 4 we obtain:
qνb
qbν
=
q0b
qb0
+
q1b
qb1
+
q2b
qb2
+
q3b
qb3
= 1 + 1 + 1 + 1 = 4.
Without consequences.
qμa qaμ = 1 (2)
WRONG! see (1). Again without consequences.
qaμ qνa = δνμ (3)
qμa qbμ = δba (4)
where δνμ and δba are the Kronecker deltas. We now differentiate eqs. (1) to (4) covariantly using the Leibnitz Theorem:
qbν Dρqνb + qνb Dρqbν = 0 (5)
qμa Dρqaμ + qaμ Dρqμa = 0 (6)
qaμ Dρqνa + qνa Dρqaμ = 0 (7)
qμa Dρqbμ + qbμ Dρqμa = 0 (8)
Rearranging dummy indices in eqn. (5) (a → b, μ → ν)
Really executed: (b → a, ν → μ) in the left summand of (5). OK.
qaμ Dρqμa + qνb Dρqbν = 0 (9)
Rearranging dummy indices in eqn. (8) (μ → ν)
Really executed: (μ → ν) in the right summand of (8),
then both summands swapped. OK.
qbμ Dρqμa + qνa Dρqbν = 0 (10)
Multiply equ. (9) by qμa
Dρqμa + qμa qνb Dρqbν = 0 (11)
Multiply equ. (10) by qμb
Dρqμa + qμb qνa Dρqbν = 0 (12)
It is seen that equ. (11) is of the form:
x + a y = 0 (13)
and equ. (12) is of the form
x + b y = 0 (14)
where
a ≠ b . (14)
The only possible solution is:
x = 0 . (15)
y = 0 . (16)
This means
Dρqμa = 0 (17)
Dρqνb = 0 . (18)
Equ. (18) is the tetrad postulate of Cartan.
It is true for all connections because no restriction on
the connection is used in deriving it.
It's true: That «proof» contains no restrictions on the connections. However, regrettably, it contains a (nice!) flaw of thinking. Why? So think about the question which is the value of y. You cannot answer that question, because the terms ay and by are no single products but sums of 16 (in the case of 4 dimensions) summands each of which contains a factor Dρqbν (ν, b = 0, 1, 2, 3). Therefore the eqns. (13),(14) are not two equations for two unknowns, but 16 unknowns are involved. And 2 equations for 16 unknowns do not determine the unknowns uniquely. Hence solutions ≠0 exist. Sorry, Myron.