ChangeDimension[exp, dim] changes all LorentzIndex and Momenta in exp to dimension dim (and also Levi-Civita-tensors, Dirac slashes and Dirac matrices).
See also: LorentzIndex, Momentum, DiracGamma, Eps.
Remember that LorentzIndex[mu, 4] is simplified to LorentzIndex[mu] and Momentum[p, 4] to Momentum[p]. Thus the fullowing objects are defined in four dimensions.
![[Graphics:Images/index_gr_1.gif]](Images/index_gr_1.gif)
![[Graphics:Images/index_gr_3.gif]](Images/index_gr_3.gif)
![[Graphics:Images/index_gr_5.gif]](Images/index_gr_5.gif)
This changes all non-4-dimensional objects to 4-dimensional ones.
![[Graphics:Images/index_gr_7.gif]](Images/index_gr_7.gif)
Consider the following list of 4- and D-dimensional object.
![[Graphics:Images/index_gr_9.gif]](Images/index_gr_9.gif)
![[Graphics:Images/index_gr_11.gif]](Images/index_gr_11.gif)
![[Graphics:Images/index_gr_13.gif]](Images/index_gr_13.gif)
Any explicit occurence of D (like in f(D)) is not replaced by ChangeDimension.
![[Graphics:Images/index_gr_15.gif]](Images/index_gr_15.gif)
The option Dimension of Eps must be changed too, since with the default setting Dimension->4 the arguments of Eps are automatically changed to 4 dimensions.
![[Graphics:Images/index_gr_16.gif]](Images/index_gr_16.gif)
![[Graphics:Images/index_gr_17.gif]](Images/index_gr_17.gif)
![[Graphics:Images/index_gr_19.gif]](Images/index_gr_19.gif)
![[Graphics:Images/index_gr_21.gif]](Images/index_gr_21.gif)
![[Graphics:Images/index_gr_23.gif]](Images/index_gr_23.gif)
![[Graphics:Images/index_gr_25.gif]](Images/index_gr_25.gif)
![[Graphics:Images/index_gr_26.gif]](Images/index_gr_26.gif)
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