Recent content by Roberto Pavani

The CODATA value of ##e/m_e## comes from Penning-trap cyclotron frequency measurements (strong ##B## field). Are there any competitive determinations of the same ratio ##e/m_e## using purely electric methods (no ##B##)? For instance from LINAC kinematics or Duane-Hunt bremsstrahlung? The papers...

A.T. gave an excellent answer in post #2, but perhaps the original question was even simpler than we made it: if a clock moves fast toward Earth and I see its hands moving slowly (time dilation), does that mean I also see the clock itself moving slowly? The answer is no. Time dilation slows...

Thank you @renormalize, that's exactly the reference I was looking for. The Vento & Lacroix paper confirms that virtual monopole-antimonopole loops would contribute to ##(g-2)##, and the current precision sets ##m_{\rm monopole} > 120## GeV. This also means that future improvements in...

While working on a preprint, I noticed what seems to be a straightforward logical chain that I haven't seen stated explicitly in the literature. I'd like to understand whether (a) it's well-known but considered too trivial to state, (b) it has been discussed somewhere, or (c) there's a flaw I'm...

After some further research, I think I found one possible answer to my own question: Chamseddine & Connes (2007/2008). They derive the full SM Lagrangian, including the inter-sector couplings, from a spectral action principle on a noncommutative geometry. In that framework, L_total is not...

For those interested, the programmes I had in mind are: emergent spacetime (Barceló, Liberati, Visser), twistor theory (Penrose), noncommutative geometry (Connes), thermodynamic gravity (Jacobson). None has fully derived L_total from first principles, but they constrain the problem from...

@Dale Your questions about the interaction terms are exactly my point: "Is it true that actions are simply added across sectors?": No, and that's precisely the non-trivial step. "Is the form of the interaction terms an a priori assumption?" In the SM, yes: the gauge group and the coupling...

@renormalize I agree that "Nature obeys the Principle of Least Action" is a valid starting point. But even granting that, the *form* of L_total (which sectors exist, how they couple, which gauge group) remains empirical input. As you noted: "we can add those individual Lagrangians along with...

The connection is this: energy conservation was an empirical discovery long before we had Lagrangians. When we formalized it via Noether's theorem, we didn't *explain* why energy is conserved. We just *relocated* the mystery. The question "why is energy conserved?" became "why does L_total have...

I agree with you all. Let me clarify what I mean: I'm not questioning that energy is conserved. Noether's theorem guarantees that, once you have the total Lagrangian with time-translation invariance, total energy is conserved. What I'm saying is: there is no theorem that tells us how to...

Each sector separately has time-translation symmetry and its own conserved energy. The fact that energy can flow between sectors while the *total* is conserved is what we use as a guiding principle to write the combined action. Noether then formalizes it, but we have already used the...

Noether's theorem states that every continuous symmetry of the action of a physical system with conservative forces has a corresponding conservation law. But it means that you can write a combined action of the physical system, then the energy is conserved. But the reason you can write the...

Noether’s theorem is ok, but can be used because we assume to write a combined lagrangian that is justified by the energy conservation among sectors, so it seems circular. Was asking if there are any non-cicular explanation or if it is just an accepted principle.

The conservation of energy between gravity and Electromagnetism and Quantum Mechanics (e.g annichilation of electron and positron) We all know that the Energy is conserved, what I'm asking if for modern physics it is just a principle or a theorem.

true, but there is a big difference between: I assume the Dirac Equation for my Theory I derive the Dirac Equation from my Theory