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Lai version of DTijk v2
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Working note by Phil dated 4.24.15 (v2) that tries to reproduce a result on pages 503-504 of Lai's text in his own notation. It uses Christoffel-like coefficients, the rotation matrices N and R, scale factors h, and expansions of a rank-2 tensor T in curvilinear basis vectors. He reaches a result close to Lai's but admits several steps are fuzzy and unproven.
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Lai's Version of (T)'ijk v2 PhL 4.24.15
I have never understood how they do this on page 503, but today I feel confident that I can translate their equations into my notation.
1. First, here is something I have shown
dn = [Γ()]kjndxj k [Γ()]kjn ≡ hn-1 [hk Γkjn – (∂jhn) δk,n]
I can rewrite this as
∂jn = [Γ()]kjnk
To simplify, lets define
Gkjn ≡ [Γ()]kjn
Then I have
(∂jn) = Gkjnk
2. Next consider ( Lai notation equations are in blue)
Lai Me
M = Mijk eiejej M = Σijk [M()]ijk ijk [M()]ijk = M'ijk
T = Tij eiej T = Σij [T()]ij ij [T()]ij = T'ij
3. So how are these M and T related? In Cartesian space I know that
(T)ijk ≡ ∂kTij ≡ Mijk assuming the idea that M = T (may not be true)
If I write this as
(T)ijk ≡ Tij;k = Mijk
then the above is a true tensor equation, and we assume orthogs, so we have this covariance triplet,
(T)ijk = Tij;k = Mijk
(T)'ijk = T'ij;k = M'ijk
(T)'ijk = T'ij;k = M'ijk
I have another expansion which from tensor doc says (J.3.1),
T = Σijk { [(T)()]ijk (hihjhk)-1} eiejek
= Σijk {(T)ijk (hihjhk)-1} eiejek
So if I can compute Lai's M'ijk I am done! I know from (E.8.20) that
M" ijk = M'ijk = Mii'Mjj'Mkk' M i'j'k' // overloaded M
Now the usual rule for going to covariant is this,
M" ijk = M'ijk = Mii'Mjj'Mkk'M i'j'k'
or
M'ijk = MiaMjbMkcMabc
But we know these two facts :
Mik = Mik = Nki = Nki // g = 1, g' = diagonal (E.9.9)
Nin = (n)i (E.8.12)
Then write Mik = Nki = (i)k so then Mia = Nai = (i)a and then
M'ijk = (i)a(j)b(k)cMabc (*)
I am trying my best to "compute M'ijk". I found in v1 doc that
T = Σij T'ij ij
(∂kT) = Σij [(∂kTij) + Taj Gika + TiaGjka ] ij
(∂cTab) = Σij [(∂cTij) + Taj Gica + TiaGjca ] [ ij]ab
= Σαβ [(∂cTαβ) + Taβ Gαca + TαaGβca ] (α)a(β)b
I could insert this in (*) above to get
M'ijk = (i)a(j)b(k)c(∂cTab)
= (i)a(j)b(k)c Σαβ [(∂kTαj) + Taj Gαka + TαaGjka ] (α)a(β)b
Replace (x)y = Nyx everywhere
M'ijk = NaiNbjNck Σαβ[(∂kTαβ) + Taβ Gαka + TαaGβka ] NaαNbβ
Then
NaiNaα = NiaNαa = δi,α using the rotation rule:
RikRjk = δi,j or Rja = Rja // "rotation" . (7.9.6)
OK, then we have
M'ijk = Σαβ [(∂cTαβ) + Taβ Gαca + TαaGβca ] NaαNbβNaiNbjNck
= Σαβ [(∂cTαβ) + Taβ Gαca + TαaGβca ] (NaαNai)(NbβNbj)Nck
= Σαβ [(∂cTαβ) + Taβ Gαca + TαaGβca ] δiαδjβNck
= Σαβ[(∂cTij) + Tij Gαca + TiaGjca ] Nck
So at least this is an answer, though probably not the right answer, but it looks close. Write as
M'ijk = Nck [(∂cTij) + Tij Gαca + TiaGjca ]
Nck ≡ Sck h'k-1 = h'k-1 Rkc
M'ijk = h'k-1 Rkc [(∂cTij) + Tij Gαca + TiaGjca ]
hk M'ijk = Rkc [(∂cTij) + Tij Gαca + TiaGjca ]
If that Rkc were not there, this would look close to page 504 top!
***************************
T = Σij T'ij ij = Σij Tij uiuj
Now apply ∂k just to the two equal expansions
Σij [(∂kTij) + Taj Gika + TiaGjka ] ij = Σij (∂kTij) uiuj
Then I avoid dealing with the strange object ∂kT. I could dot this with i'j' to get
Σij [(∂kTij) + Taj Gika + TiaGjka ] δii'δjj' = Σij (∂kTij) uiuj i'j'
or
[(∂kTi'j') + Taj' Gi'ka + Ti'aGj'ka ] = Σij (∂kTij) (ui i')(uj j')
But then
(ui i') = Σc(ui)c (i')c = (i')i
to get this strange result
[(∂kTi'j') + Taj' Gi'ka + Ti'aGj'ka ] = Σij (∂kTij) (i')i (j')j
or
[(∂kTij) + Taj Gika + TiaGjka ] = Σnm (∂kTnm) (i)n (j)m
Nin = (n)i maybe this says Nin = (n)i so Nni = (i)n
Then
[(∂kTij) + Taj Gika + TiaGjka ] = Σnm (∂kTnm) Nni Nmj
= Σnm Nni(∂kTnm)Nmj
and again this looks like a Hilbert Space rotation. Maybe somehow you get
Σnm Nni(∂kTnm)Nmj = (∂'kT'nm) = h'k (∂kT'nm)
and then somehow you get
(∂kT'nm)h'k = [(∂kTij) + Taj Gika + TiaGjka ]
and this does look like the Lai result. But my steps are all fuzzy here. End of this day.