What does the symbol mean?

[romsofia]

http://arxiv.org/PS_cache/arxiv/pdf/1001/1001.3668v2.pdf

Equation (4), what does the symbol that looks like AND mean? I know it's not AND because it would make absolutely no sense in this case.

Thanks for any help!

 

[HallsofIvy]

That is the "wedge" operator on vectors: http://mathworld.wolfram.com/WedgeProduct.html

 

[romsofia]

Thank you very much!