The departure of Ms Wolowitz abruptly solved a jealousy-ignited argument between Stewart and Howard revolving around the furniture from the Wolowitz house.
Also, if you missed that, Penny learned that she's been getting tests from Amy who was comparing her intelligence to the intelligence of the chimps. Penny did pretty well, probably more so than Leonard.
But the episode began with the twist described in the title. Barry brought a bottle to Amy because she had previously helped him with a paper that Kripke wrote and that was apparently very successful.
Kripke revealed that the paper was on the wight-cone quantization (I suppose he meant light-cone quantization) of string theory.
It's funny because some of my most well-known papers were about the light-cone quantization (in particular, Matrix theory is a light-cone-quantized description of string/M-theory), and I've been a big fan of this (not terribly widely studied) approach to string theory since 1994 when I began to learn string theory at the technical level. There are no bad ghosts (negative-norm states) or local redundancies in that description (well, except for the \(U(N)\) gauge symmetry if we use the matrix model description) which is "very physical" from a certain perspective.
Throughout the episode, Sheldon was jealous and unhappy that he had left string theory. Penny was trying to help him to "let it go"; this effort turned against her later. Recall that in April 2014, the writers turned Sheldon into a complete idiot who had only been doing string theory because some classmates had been beating him with a string theory textbook and who suddenly decided that he no longer considered string theory a vital branch of the scientific research.
The yesterday's episode fixed that harm to string theory – but it hasn't really fixed the harm done to Sheldon's image. Nothing against Kripke but the path that led him to write papers to string theory seems rather bizarre to me. When he appeared in the sitcom for the first time, I was convinced that we had quite some data that he was just some low-energy, low-brow, and perhaps experimental physicist. Those usually can't write papers on light-cone-quantized string theory.
But the writers have gradually transformed the subdiscipline of physics that Kripke is good at (this was not the first episode in which Kripke looked like a theoretical physicist). Of course, this is a twist that I find rather strange and unlikely but what can we do? Despite his speech disorder and somewhat obnoxious behavior, we should praise a new string theorist. Welcome, Barry Kripke. ;-)
Adopt your own Greek for €500!
He will do everything that you don't have time to do:
* sleep until 11 am
* regularly have coffee
* honor siesta after the lunch
* spend evenings by sitting in the bar
You will finally have the time to work from dawn to dusk.