What are B mode and E mode signals?

[man@SUT]

I've read an article in nature and found technical words "B mode signal" and "E mode signal". I don't understand what they are. In a website, they say it's like the electromagnetic field line but I'm still not clear.

I also don't understand what k means in " the linear greyscale shows the E-mode lensing convergence field k(Kappa)". I think it's also the technial word.

The article is about the dark matter maps.

 

[hellfire]

I do not know the details but this is known as E-B mode decomposition. Basically the E-mode is a measure of the stretching (shear) of the light source that is weak lensed. This mode is curl free and is generated by gravitational effects. As far as I know the other mode maps, the B-mode maps, are the noise components that cannot be identified with the gravitational physics of the lens.

You may want to read this article about gravitational lensing basics:
http://astro.berkeley.edu/~jcohn/lens.html

And this one about E-B mode decomposition (end of the page):
http://www.lsst.org/Science/Cosmic_Shear.shtml

 

[man@SUT]

Thank you very much, Mr Hellfire.

I'll try to search again from those links.