When applied to Web SSO, Einstein's Theory of Special Relativity predicts that the advantages to users are minimal at best.
Consider two users Alice & Bob, both of whom having successfully simultaneously authenticated to the same IDP, are hoping to browse to the same service provider. Alice will avail herself of SSO from the IDP, while Bob will get there the old fashioned way, i.e. use his bookmark for the SP and once there, log in with is password.
It's undeniable that, using SSO, Alice will get to the SP before Bob. But there is a trade-off for her.
Special relativity constrains Alice's combined motion through space & time (specifically that their sum must exactly equal the speed of light). As Alice is 'travelling' faster than Bob, her motion through time must slow down to compensate - and time will consequently be slower for Alice.
Initial calculations show that any actual speed advantage for Alice will be almost exactly negated by her perception of the SSO taking longer than it actually does - this a result of the time dilation.
I call this the 'Theory of Special Redirectivity'.