Optical simulations of gravitational effects

[bartrocs]

I'm preparing a poster presentation on the following paper for a physics course:
http://t.co/xiCLV7Y0ZH

I do not understand how figure 4 tells us about the red/blue shift. Just from the deflections of the peaks of the airy beam, as well as the deformation, how are we able to infer that there is a red shift effect?

I tried explaining this to myself by the spatial frequency of the observed peaks, however I realized that a beam that is escaping from a gravitational well should appear red shifted, yet this seemed to imply the opposite. I then realized that we are looking at an intensity distribution, so now I am confused as to how we can infer that a red shift type effect is present

 

[jerromyjon]

This seems quite deep so I'm not sure, but I take figure 4 as the combination of blue shift then red shift which varies in a complex manner relative to beam intensity so the apparent shift would be the difference between the 2? The bottom c,d shows "centered" on 0 shift meaning no displacement, no shift, both high and low intensity beams are not shifted. I'm going to let it sink in for a while and read it again! Quite interesting!

 

[bartrocs]

In the bottom two, they've just shifted the peaks so that they line up to make stretching and squashing effect more apparent.