1. ### I Question about the Equivalence Principle (locally flat spacetimes)

Hi all, I have ran into some confusion about the equivalence principle; perhaps I should state what I understand and then proceed to ask questions. It is my understanding that the equivalence principle states that spacetimes are locally Minkowski, and so the rules of SR apply in that locality...

Suppose an observer (O) sees a traveler (T1) pass by at time t=0, moving a speed 3c/5. Five years later (according to O), T1 returns. If we assume that T1 traveled at 3c/5 for half the journey and instantaneously reversed direction, returning at the same speed, we can calculate that T1 aged only...
3. ### I Is Simultaneity still alive in QM?

In Classical Mechanics, according to SR, the concept of simultaneity is dead, a meaningless concept. But in QM, entanglement implies that some limited form of simultaneity exists. If we have two particles correlated due to entanglement, a measurement of one particle immediately gives us the...
4. ### Speed and direction of b and anti-b quark

Homework Statement A Higgs particle of mass M is moving in the z-direction with speed $\Beta_H$c compared to the lab system. It decays to a b-quark ans anti-b quark, each of mass m. What is the speed and direction of the b-quark compared to the lab-system, if the Higgs system, (a) it is emitted...
5. ### Does this ANN make Benjamins?

I'm attempting to use a artificial neural network to store a fuzzy floating point variable. While writing the code, I became somewhat creative. I used the idea of an Set Reset Latch and statistically translated the hardware SR-latch into an artificial neural network. My mathematical goal is to...
6. ### I Rolling Rings in SR

This post is about the methodology required to produce the Fig. 9 Part C “optical appearance” plot as calculated by Øyvind Grøn in "Space geometry in rotating reference frames: A historical appraisal". http://areeweb.polito.it/ricerca/relgrav/solciclos/gron_d.pdf In 2014 I contributed to a...
7. ### B Why do we need the concept of "event" in SR

Event is anything which can be located by (x,y,z,t). We don't need this concept in Galilean transformation. I was first introduced to the concept in the beginning of Special relativity. I haven't understood the significance of this concept till now. Can anyone please illustrate me using an...
8. ### Trouble with 2 step velocity transformation in SR

Homework Statement Given: An object at rest with respect to an inertial reference frame S. 2 other inertial reference frames S' and S''. S' has velocity (vx, vy) = (-.6c, 0) with respect to S. S'' has velocity (vx, vy) = (-.6c, +.6c) with respect to S. Assumptions: If I transform my...
9. ### I QFT in Euclidean or Minkowski Spacetime

Forgetting for the moment about curved spacetime, does the relativistic QFT in use today by experimental physicists live in Euclidean spacetime or Minkowski spacetime. Thanks in advance.
10. ### I Help with Anti-Relativity activist

I’m looking for feedback with respect to an SR “paradox”. I’ve gotten myself into a dialog with an Anti-Relativity activist. I know I’ll hate myself in the morning but I thought I would at least make an attempt at explaining this “paradox”. You may be familiar with it. It goes like this...
11. ### I Proper mapping of the second postulate into math

The second postulate of SR is telling us that light always travels at C in a vacuum(absent of gravity) measured by any observer independent of the source or inertial frame the observer is measuring the light from. However, light is made up of photons which do not travel like ping pong balls in...
12. ### Inverse Compton Scattering

Hello all, i'm just doing some practice for an upcoming exam and came upon this question in my notes: One experimental way to generate very high energy photons is to ”collide” a laser beam against an electron beam, the photons that recoil in the direction parallel to the electron beam will have...
13. ### I The Debroglie Relation and SR?

The function ei(p.r – Et) is the central player in non-relativistic QM. Yet the expression (p.r – Et) is the Minkowski inner product of the space-time four-vector, (t,r), and the four-momentum (E,p) and as such is Lorentz invariant. According to Feynman, De Broglie realized the relativistic...
14. ### Schwarz Inequality is your friend

I would like to show you how to use Schwarz inequality to prove some important general theorems and solve problems about vectors in Minkowski spacetime. Okay, Schwarz inequality states that \left| U^{k}V^{k}\right| \leq \sqrt{(U^{i})^{2}(V^{j})^{2}}. \ \ i,j,k =1,2,3 \ \ \ (1) And, the...