What Does the [] of [X]t Mean in Girsanov Theorem?

[tennishaha]

http://en.wikipedia.org/wiki/Girsanov_theorem

Could anyone tell me what does the [] of [X]_t mean in the attached equation, shown in wiki's Girsanov_theorem page?

Thanks

 

[tiny-tim]

hi tennishaha!

it seems to be the quadratic variation … see http://en.wikipedia.org/wiki/Quadratic_variation"

 

[tennishaha]

thanks! :)
yes, it should be this