# Problem with notation ?

1. Apr 26, 2013

### Mentz114

http://lanl.arxiv.org/abs/gr-qc/9611042v1

I'm baffled by this bit on page 3,
In a footnote on page 4 we are told
By this, K·K = 0 and equation 2.1 is nonsense. What have I missed ?

2. Apr 26, 2013

### martinbn

The dot notation from the footnote has parentheses as well, and it is just dot, not a cdot.

3. Apr 26, 2013

### Mentz114

Yes, thank you. What I missed was that K is not in boldface.

So r = K·K $\equiv$ KμKμ ( μ = 0,1,2,3)

Last edited: Apr 26, 2013