We are happy to announce that a new thematic programme with 5 focus weeks just got started at
@ESIVienna
! 🥳 Check out the details below ⏬

📅 31st July - 1st September 2023 📅
📌 Schrödinger Lecture Hall 📌

▫️ Programme description ▫️
https://esi.ac.at/events/e476/

📚 Subject: #QuantumFieldTheory at the Frontiers of the #StrongInteraction
📓Week 1: Finite-Mass and #Electroweak Effects in #gaugetheories
📕 Week 2: #Singularity Structure of Quantum Field Theory Beyond the Leading Power
📗 Week 3: #Factorization Violation and the #Space of Universal Functions
📘 Week 4: Simulation of the All Order Structure of Scattering Amplitudes
📙 Week 5: Multi-Variable Techniques for All Order Resummations in QFT

@univienna

I woke up this morning thinking about how weird the fermion generations are. Charged fermions have three discrete generation values, and those generation values are conserved under photon, gluon, and Higgs interactions, only changing under the weak interaction. But in the SM as modified to give neutrinos mass, they oscillate between generation eigenstates, and they do so spontaneously without any contributions from W interactions (since that would change their flavor to charged lepton) or AFAIK Z interactions (unless they're constantly emitting and reabsorbing Z bosons as they travel, which seems unlikely since the rotation is continuous).

That tells me that generations themselves are a broken symmetry, in the sense that a continuous degree of freedom has been constrained so that it can only take on one of three discrete values, but neutrinos experience the symmetry in its unbroken, continuous form. The fact that the weak interaction can *optionally* change generation while changing flavor indicates that the electroweak sector is involved, but AFAIK the SM does not explain why it would trigger the existence of particle generations.

(I wonder if the broken SU(2) symmetry *is* the generation. It would neatly explain why there are exactly three generations, via the well-known fact that SU(2) is a double cover of SO(3), so each generation could be an orthogonal axis on the unit sphere in R^3.)

Please tell me that someone else has noticed this? I've never seen anyone talk about it.

#physics #StandardModel #electroweak #higgs