Recent content by Roberto Pavani

A side note: Fine (Phys. Rev. Lett. 48, 291, 1982) shows that the Bell inequalities hold if and only if a joint distribution for all observables exists. But Kolmogorov's linearity of expectation requires exactly that a common probability space. So when the joint distribution doesn't exist, isn't...

What you're describing is essentially a passive Fabry-Pérot cavity. This is actually a well-known setup — the intracavity field can be enhanced (roughly ~100× with good mirrors), but losses always set a steady-state limit. You don't get infinite accumulation. In practice, what works is...

The answers above are correct. Just adding a safety note: any laser above ~500 mW (Class 4) requires proper eye protection, not just from the direct beam, but from diffuse reflections off walls, dust scattering, and secondary reflections from ordinary surfaces. At 260W, scattered light alone...

Agreed. And more generally by Dirac's equation for relativistic particles. The entanglement is already in the formalism, no extra axiom needed. Though I suspect the OP's real question may be whether entanglement hints at something deeper beneath Schrödinger/Dirac, but that's OT here.

Yes, I think I was expressing roughly the same thing in a less rigorous way. Thank you for the precise formulation. What I was (clumsily) trying to say is: ##F = I \, \partial(\oint \mathbf{A} \cdot d\mathbf{l})/\partial x##. That's all.

It seems to me that the deformation forces are all caused by ##\nabla A## ?

You're right, I overstated the symmetry, B is not zero at the bar. My mistake. Still, I notice that explaining the force on the bar using Lorentz force has historically been non-trivial (as the McDonald paper linked by @Sagittarius A-Star shows, it requires careful analysis). Whereas...

@Dale I've found an interesting link: http://www.ampere.cnrs.fr/histoire/parcours-historique/lois-courants/force-obsolete/eng @Sagittarius A-Star you beat me in speed

The symmetry I refer to: current approaches the bar through one trough and leaves through the other, in opposite directions. These two symmetric return currents produce B fields that largely cancel at the bar's location. I agree it's not exactly zero in practice, but it becomes negligible...

I'd like to share an observation and ask if others find it compelling. Consider a current-carrying loop that tends to expand. This is usually explained by the Lorentz force (IL×B) on each segment due to the field of the other segments. Equivalently, one can describe it in terms of the...

The effect is very different between DC and AC current. With DC, if you hang with both hands, the scenario is similar to https://en.wikipedia.org/wiki/Earth_potential_rise A potential difference exists between your two hands due to the resistance of the wire segment between them. But...

Just a small note: the TV signal mentioned is DC-coupled at baseband, the asymmetry exists only because there's a ground reference. Once radiated, it's effectively AC-coupled: no DC component can propagate through an EM wave, so the energy over a full cycle is always balanced. As for treating...

As others have noted, the drift direction is phase-dependent, so it's really an artifact of the initial conditions rather than a general physical effect. If there's any real (tiny) net drift, I'd look at radiation pressure, the v × B force gives a push along the propagation direction. For a wave...

x=:doh:= 42

Very interesting discussion. I'd note that the arXiv preprint I referenced in a related thread (Hobson, Barker & Lasenby, arXiv:2605.19719), proving that no local gauge-invariant energy-momentum tensor exists for the linearised gravitational field, seems relevant here as well.