volume | R Documentation |
The volume element in \mjseqnn dimensions
volume(n)
is.volume(K,n=dovs(K))
n |
Dimension of the space |
K |
Object of class |
Spivak phrases it well (theorem 4.6, page 82):
If \mjseqnV has dimension \mjseqnn, it follows that \mjeqn\Lambda^n(V). has dimension 1. Thus all alternating \mjseqnn-tensors on \mjseqnV are multiples of any non-zero one. Since the determinant is an example of such a member of \mjeqn\Lambda^n(V). it is not surprising to find it in the following theorem:
Let \mjeqnv_1,...,v_nv_1,...,v_n be a basis for \mjseqnV and let \mjeqn\omega\in\Lambda^n(V).. If \mjeqnw_i=\sum_j=1^n a_ijv_j. then
\mjdeqn \omega\left(w_1,...,w_n\right)=\det\left(a_ij\right)\cdot\omega\left(v_1,... v_n\right)omitted; see PDF
(see the examples for numerical verification of this).
Neither the zero \mjseqnk-form, nor scalars, are considered to be a volume element.
Function volume()
returns an object of class kform
;
function is.volume()
returns a Boolean.
Robin K. S. Hankin
M. Spivak 1971. Calculus on manifolds, Addison-Wesley
zeroform
,as.1form
,dovs
dx^dy^dz == volume(3)
p <- 1
for(i in 1:7){p <- p ^ as.kform(i)}
p
p == volume(7) # should be TRUE
o <- volume(5)
M <- matrix(runif(25),5,5)
det(M) - as.function(o)(M) # should be zero
is.volume(d(1) ^ d(2) ^ d(3) ^ d(4))
is.volume(d(1:9))
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