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6

The term rest mass is a poor one because it implies it's the mass measured in the rest frame. But photons have no rest frame, and indeed any particle subject to some form of confinement has a $\Delta p\gt 0$ so its rest frame is somewhat poorly defined. The modern term is invariant mass, which is simply the mass in the equation for the total energy: $$ E^2 ...


5

Let me preface by saying that "coupling" is a favorite physicist word that is perhaps best described linguistically than rigorously; it's deployed in a few different situations. In general, we say that a coupling exists in quantum mechanics if the evolution of one part of the system depends on another quantity, which could be either classical or quantum. I'...


4

Pseudoscalar and vector are terms that indicate the total spin and parity of the resonance. Pseudoscalar particles have spin 0 and parity -1, while vector particles have spin 1 and parity -1. The Particle Data Review lists your particles as: $D^\pm\qquad\qquad\qquad\quad 0^-$ $D^0\qquad\qquad\qquad\quad 0^-$ $D^*(2007)^0\qquad \qquad 1^-$ $D^*(2010)^\pm\...


4

Online data analysis is cursory analysis done as the data is collected. It is often used for the purpose of selecting which events to save to disk or tape to be analyzed later (an event "filter"). Given that the current CERN experiments will be taking, in the next run, data at rates exceeding a terabyte per second, this notion is essential. In fact, the ...


3

"Normal" in the context of oscillators simply means "periodic" – periodic solutions and the frequencies and other aspects associated with them. It's like in "he breathes normally" – the breathing seems to be periodic. "Quasinormal ones" are those whose time dependence is $\exp(-\Gamma t) \sin (\omega t)$, i.e. they have some exponential decrease aside from ...


3

There is something famously called "Feynman's famous formula", which comes up in QFT calculations, which I imagine must be the second FFF referred to in Welton's account. It reads: $$\frac1{a_1 a_2 \ldots a_n} = \int_{x \in \Delta^{n-1}} \frac1{(\sum_{i=1}^n a_i x_i)^n} d\sigma$$ where $\Delta^{n-1}$ denotes the simplex $\{x = (x_1, \ldots, x_n) \in \...


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That's the Gertsenshtein effect. It is the theory that light passing through a strong magnetic field will produce a gravitational wave.


2

In optics a "ray" is the direction of propagation of the classical electromagnetic wave. The term "ray' used for particles, as "cosmic rays" , and "gamma rays" are associated with this directional definition, from the times when it was clear that the phenomena followed straight lines like optical rays, before the differentiation into the particles we know ...


1

An internal symmetry is a transformation acting only on the fields, therefore not transforming spacetime points, and leaving the lagrangian or the physical results invariant. Example of internal symmetries are gauge symmetries. These are local symmetries, which means the transformations are in general spacetime dependent in the sense they are, in general, ...


1

I think "normal" means also "proper to the system", i.e., existing after the system ceased to experience an external force.


1

For the simple hydrogen atom there exists a ground state, then there are energy levels where an excited electron can reside, and then there is the zero energy level, so yes, there is a name in this case. From the zero energy level the maximum energy is given up, when the electron falls to the ground state, so it is the highest potential energy state.



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