More on the paper that was submitted for publication which takes a newish approach to quantizing gravity, that of invoking the E8 group structure as a superset of the standard model:
“Sabine Hossenfelder at the Perimeter Institute argues that Lisi’s idea could be complementary to String Theory because string theorists were already looking at E8 in relation to the Calabi-Yau manifolds. String theorists introduced these as a way of explaining why the extra dimensions they required in their string theory were not visible to us at macro scales.
Extending Quantum Field theory into the E8 structure envisaged by Lisi would lead to a new physics very different to string theory. For one thing a component of string theory called super gravity hypothesized a set of super symmetric partners for each known particle as a way of eliminating the infinities that appear when extrapolating the theory to smaller scales. Lisi’s model predicts there are just 20 undiscovered elementary particles. Also Lisi’s model predicts the three generations of particles.”
This paper has generated a fair bit of controversy already. Besides the fact that it calls string-theory into question (or at least puts it into a new context), the most impressive thing is that it makes specific predictions of new particles. And we should know in the not too distant future whether or not this is really going to be something seminal, or if it’s just another attempt to solve a to-date intractable problem.
Read the rest here.