Essays/Christoffel/Christoffel01

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1 Reference

'Tensor Analysis' by I. S. Sokolnikoff (Second Edition, 1964).


2 Software

NB. ... execute (ijx) ...

   9!:14 ''
j601/2006-11-17/17:05


3 Continuous Functions

There is a footnote on page 1 of the book 'Riemannian Geometry' by Luther Pfahler Eisenhart.


'When we consider any function, it is understood that it is real and continuous, as well as its derivatives of
such order as appear in the discussion, in the domain of the variables considered, unless stated otherwise.'


4 Verbs

NB. ... script (ijs) ...

NB. ... identify coordinates ...
y1=:0{]
y2=:1{]
y3=:2{]
x1=:0{]
x2=:1{]
x3=:2{]

NB. ... open boxed elements ...
b0=:>@(0{])
b1=:>@(1{])
b2=:>@(2{])
b3=:>@(3{])

NB. ... tolerant 'set zero' (see 'Essays/Tolerant Comparison') ...
tsz=:$@]$[0:`(I.@([>!.0|@]))`]},@]
ts0=:(2^_44)&tsz
tz =:ts0@:

NB. ... tolerant 'equal'    (see 'Essays/Tolerant Comparison') ...
teq=:*./@,@((b0|@:-b1)<:!.0[*b0>.&:|b1)

NB. ... verbs useful for tolerant comparison ...
nzmin  =:<./@:|@((0<!.0|)#])@,
nzmax  =:>./@:|@((0<!.0|)#])@,
nzcount=:+/@(0<!.0|)@,

NB. ... trig verbs ...
sin   =:1&o.
cos   =:2&o.
arctan=:_3&o.

NB. ... axes sum ...
axs=:ts0@((b0|:b1)+/@(*"1)"1 _ b2|:b3)


5 Transformation of Coordinates (ISS Section 19)

5.1 General
GCH0100C.jpg


5.2 Example

I.S.S. Figure 13 on page 114 shows the transformation from Cartesian coordinates (y) to Spherical coordinates (x)
in Euclidean space.


CHspherical.jpg
Figure 1: Spherical coordinates


GCH0101C.jpg


NB. ... script (ijs) ...

NB. ... equations to transform from Cartesian coordinates to Spherical coordinates ...
cx1=:%:@(*:@y1+*:@y2+*:@y3)"1
cx2=:arctan@(%:@(*:@y1+*:@y2)%y3)"1
cx3=:arctan@(y2%y1)"1
cxx=:(cx1,cx2,cx3)"1             NB. convert y coordinates to x coordinates

NB. ... equations to transform from Spherical coordinates to Cartesian coordinates ...
cy1=:(x1*sin@x2*cos@x3)"1
cy2=:(x1*sin@x2*sin@x3)"1
cy3=:(x1*cos@x2)"1
cyy=:(cy1,cy2,cy3)"1             NB. convert x coordinates to y coordinates

NB. ... from 'numeric' ...
steps=:{.+(1&{-{.)*(i.@>:%])@{:

NB. ... verbs to generate coordinates ...
s1=:steps@(0.5,10,19"_)
s2=:steps@((0.5p1%10),(0.5p1-0.5p1%10),19"_)
s3=:steps@((0.5p1%10),(0.5p1-0.5p1%10),19"_)

NB. ... generate coordinates ...
xpgen=:>@,@:(<"1)@(s1,"0 1/s2,"0/s3)
ypgen=:cyy@xpgen


6 First Derivatives of Transformation Equations

6.1 General (3 dimensions)
GCH0102C.jpg


6.2 Example
GCH0103C.jpg


NB. ... script (ijs) ...

dxdy0=:(sin@x2*cos@x3),(sin@x2*sin@x3),cos@x2
dxdy1=:((cos@x2*cos@x3)%x1),((cos@x2*sin@x3)%x1),-@(sin@x2%x1)
dxdy2=:-@(sin@x3%x1*sin@x2),(cos@x3%x1*sin@x2),0:
dxdy =:(3 3$dxdy0,dxdy1,dxdy2)"1

dydx0=:(sin@x2*cos@x3),(x1*cos@x2*cos@x3),-@(x1*sin@x2*sin@x3)
dydx1=:(sin@x2*sin@x3),(x1*cos@x2*sin@x3),x1*sin@x2*cos@x3
dydx2=:cos@x2,-@(x1*sin@x2),0:
dydx =:(3 3$dydx0,dydx1,dydx2)"1


7 Second Derivatives of Transformation Equations

7.1 General (3 dimensions)
GCH0104C.jpg


GCH0105C.jpg


7.2 Example
GCH0106C.jpg


NB. ... script (ijs) ...

d2xdydx00=:0,(cos@x2*cos@x3),-@(sin@x2*sin@x3)
d2xdydx01=:0,(cos@x2*sin@x3),sin@x2*cos@x3
d2xdydx02=:0,-@(sin@x2),0:
d2xdydx10=:(-@((cos@x2*cos@x3)%*:@x1)),(-@((sin@x2*cos@x3)%x1)),-@((cos@x2*sin@x3)%x1)
d2xdydx11=:(-@((cos@x2*sin@x3)%*:@x1)),(-@((sin@x2*sin@x3)%x1)),(cos@x2*cos@x3)%x1
d2xdydx12=:(sin@x2%*:@x1),-@(cos@x2%x1),0:
d2xdydx20=:(sin@x3%(*:@x1)*sin@x2),((sin@x3*cos@x2)%x1**:@(sin@x2)),-@(cos@x3%x1*sin@x2)
d2xdydx21=:(-@(cos@x3%(*:@x1)*sin@x2)),(-@((cos@x3*cos@x2)%x1**:@(sin@x2))),(-@(sin@x3%x1*sin@x2))
d2xdydx22=:0,0,0:
d2xdydx0 =:d2xdydx00,d2xdydx01,d2xdydx02
d2xdydx1 =:d2xdydx10,d2xdydx11,d2xdydx12
d2xdydx2 =:d2xdydx20,d2xdydx21,d2xdydx22
d2xdydx  =:(3 3 3$d2xdydx0,d2xdydx1,d2xdydx2)"1


GCH0107C.jpg


NB. ... script (ijs) ...

d2ydxdx00=:0,(cos@x2*cos@x3),-@(sin@x2*sin@x3)
d2ydxdx01=:(cos@x2*cos@x3),-@(x1*sin@x2*cos@x3),-@(x1*cos@x2*sin@x3)
d2ydxdx02=:(-@(sin@x2*sin@x3)),(-@(x1*cos@x2*sin@x3)),-@(x1*sin@x2*cos@x3)
d2ydxdx10=:0,(cos@x2*sin@x3),sin@x2*cos@x3
d2ydxdx11=:(cos@x2*sin@x3),-@(x1*sin@x2*sin@x3),x1*cos@x2*cos@x3
d2ydxdx12=:(sin@x2*cos@x3),(x1*cos@x2*cos@x3),-@(x1*sin@x2*sin@x3)
d2ydxdx20=:0,-@(sin@x2),0:
d2ydxdx21=:-@(sin@x2),-@(x1*cos@x2),0:
d2ydxdx22=:0,0,0:
d2ydxdx0 =:d2ydxdx00,d2ydxdx01,d2ydxdx02
d2ydxdx1 =:d2ydxdx10,d2ydxdx11,d2ydxdx12
d2ydxdx2 =:d2ydxdx20,d2ydxdx21,d2ydxdx22
d2ydxdx  =:(3 3 3$d2ydxdx0,d2ydxdx1,d2ydxdx2)"1



Download: File:LCH0100C.txt
Download: File:LCH0101C.txt
Download: File:LCH0102C.txt
Download: File:LCH0103C.txt
Download: File:LCH0104C.txt
Download: File:LCH0105C.txt
Download: File:LCH0106C.txt
Download: File:LCH0107C.txt




Download MoinMoin source: File:Christoffel01.ijs




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Contributed by Tom Allen