Use this for questions relating to the proper use of physics terminology or nomenclature.

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2
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1answer
44 views

Is UV catastrophe same as IR catastrophe?

I am currently studying quantum physics from Serwey-jewet. Where in the topic of Planck's law, infrared catastrophe is alternatively used for UV catastrophe while explaining how Plancks constant ...
0
votes
1answer
27 views

Do gauge bosons really transform according to the adjoint representation of the gauge group?

Its commonly said that gauge bosons transform according to the adjoint representation of the corresponding gauge group. For example, for $SU(2)$ the gauge bosons live in the adjoint $3$ dimensional ...
1
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0answers
29 views

What does 'easily reversed' mean in the NIST spectral database? [on hold]

Cross posted to http://engineering.stackexchange.com/q/3303/ I'm trying to do some processing of optical emission spectra from sputtering plasmas, and am confused by what NIST means by 'easily ...
1
vote
0answers
57 views

How is the formula for the capacitance of a parallel plate capacitor derived?

I have seen in I.E. Irodov that if the permittivity is given as $\epsilon$ then we can find the capacitance as $$C = \frac{\epsilon A}{d}$$ but I wonder whether it is dimensionally correct or not and ...
-1
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1answer
34 views

Why is work done $F$ applied over a distance energy? [on hold]

Why is $E=(1/2)mv^2$ named energy? It doesn't seem intuitive to me to call it such.
0
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0answers
31 views

Does “$\mathbf r[~t~]$” correctly denote the trajectory of a point particle wrt. a reference system w/o having to decide on a particular origin?

Consider a specific geometric reference system, e.g. a specific inertial frame(1): the suitable set of point particles $\mathcal S := \{ H, J, K, ..., O, P, Q, ... \}$; and consider one other point ...
2
votes
1answer
54 views

What operation does a beam splitter apply?

What is the unitary matrix equivalent to the operation of a beam splitter? I'm asking because I've seen different matrices used and was wondering if the term is just ambiguous or if there's an agreed ...
5
votes
5answers
288 views

Is Parity really violated? (Even though neutrinos are massive)

The weak force couples only to left-chiral fields, which is expressed mathematically by a chiral projection operator $P_L = \frac{1-\gamma_5}{2}$ in the corresponding coupling terms in the Lagrangian. ...
1
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0answers
37 views

Dynamics and kinematics of quantum field theory

What is the difference between dynamics and kinematics of quantum field theory? I read that in QFT there is no possibility to keep the two things distinct because of a problem with the separability of ...
2
votes
1answer
62 views

What does “downshear” mean?

I occasionally read descriptions such as "downshear of the vortex" in meteorological publications. What does this mean?
1
vote
2answers
215 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
4
votes
3answers
406 views

In the double slit experiment what, exactly, is a slit?

I have seen and read several times about the double slit experiment, that an electron (or even a molecule (!) as I found out later) behaves like a wave that swaps over those slits. However I wonder ...
0
votes
0answers
21 views

Measurement of drag (?) tension between two surfaces

I want to know if there are (reasonably inexpensive) devices to measure the tension between two surfaces. Beware of my terminology: the first help I need is to actually formulate my question ...
1
vote
1answer
35 views

What is “forward peaking”?

In "Research and Development for a Gadolinium Doped Water Cherenkov Detector" the phrase "forward peaking" is used to describe a signal. This comes up in lots of other contexts too, but I still can't ...
1
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0answers
51 views

Is hidden symmetry the same concept as broken symmetry for the standard model?

I have recently started studying the basic ideas of symmetry and group representation in order to understand the basic principles behind the standard model. I do follow the difference between a global ...
2
votes
2answers
209 views

What is meant by “unique direction” in most of the arguments in application of Gauss' Law?

This term is really bothering me a lot. While explaining the radial direction of electric field of a uniformly charged sphere, my book writes: Notice the use of argument of symmetry. There is no ...
9
votes
3answers
13k views

Is time a Scalar or a Vector?

In Wikipedia it's said that time is a scalar quantity. But its hard to understand that how? As stated that we consider only the magnitude of time then its a scalar. But on basis of time we define ...
12
votes
5answers
5k views

Why and how does negative velocity exist?

Why and how does negative velocity exist? I have read on the internet about negative velocity but I still don't understand how it can even exist since time is positive and so is length. By doing some ...
1
vote
1answer
31 views

What is meant by 'a perfect dipole'?

Question What is meant by a perfect (electric) dipole? Additional information I came across the term in this question Force from point charge on perfect dipole and also in a textbook (which does ...
0
votes
1answer
40 views

Superscript on density matrix

I have been asked in homework to solve the optical bloch equation for the initial condition of $\rho_{22}=0,\rho_{12}=0$. Professor gave a hint of the general equation and let us carry it from here. ...
3
votes
2answers
101 views

Is kinetic theory part of statistical mechanics?

Some years ago from now I've seem some basic details about what was then called "kinetic theory of gases" where the study of property of gases was made by statistical considerations about the momentum ...
2
votes
2answers
39 views

Difference between a reversible change and a reversible process?

Question In thermodynamics what is the difference between a reversible change and a reversible process? Additional information I am new to the topic of thermodynamics and getting confused about ...
0
votes
0answers
15 views

Radial excitation and orbital-angular momentum excitation

Sorry. Just want to make sure, but what does radial excitation and orbital-angular excitation mean in the context of bound states? Just higher $n$ and $\ell$ quantum number?
0
votes
2answers
28 views

Is net work and total work same?

According to my text book Total Work = Delta Kinetic Energy = KEf - KEi But then work is defined to be dot product of Force (vector) and Displacement (vector). Also to my knowledge work is ...
1
vote
2answers
122 views

Friction force in rolling motion

In rolling without slipping motion we know that the friction acting is static friction and so we treat it as an unknown while solving equations of dynamics. Question: Is the static friction during ...
2
votes
1answer
62 views

Is there a scientific term for the right-hand-(grip-)rule?

To illustrate and remember the direction of rotation around an axis defined by a vector as it happens to be in some fields of physics, one can employ the right-hand-rule: (image from here) Is ...
2
votes
1answer
202 views

What was Feynman's famous formula?

In Welton(1983), Memories of Feynman, Welton mentions two formulas which he denotes as Feynman's Famous Formula (FFF) and FFF #2. Which famous formulas is he talking about? Is he maybe talking about ...
3
votes
2answers
143 views

Rigorous distinction between quasiparticles and collective excitations

I would like to hear your opinion on the question whether there is an accepted distinction between both concepts in condensed matter physics. I would tend to use the word quasiparticle for dressed ...
3
votes
2answers
149 views

What is the difference between Chiral anomaly, ABJ anomaly, and Axial anomaly?

I get confuse with these three terms: Chiral anomaly, ABJ anomaly, and Axial anomaly. I can not find standard definition of these three. Is there anyone can describe precisely?
1
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3answers
76 views

Gravitational acceleration

'What is difference between free fall acceleration g and gravitational acceleration a?***a is with subscript g.In my textbook it is written that "free fall acceleration = gravitational acceleration - ...
0
votes
0answers
43 views

What is primitive divergence?

As in the title, what is primitive divergence? How is it distinguished from normal divergence? As a followup, what is a primitive divergent graph in a theory? Some simple examples?
6
votes
1answer
175 views

Group representations as vectors and isomorphism between weights and matrix generators

This might be something basic, but it is unclear to me. So I am used to work with representations of groups as matrices. These matrices represent the structure of the Lie algebra by satisfying the ...
3
votes
1answer
86 views

What is a weak solution of the MHD equations?

Many papers concerning solutions to the magnetohydrodynamics (MHD) equations (eg. Osher, 1984) say that one is generally interested in finding weak solutions. Sometimes they are even called global ...
1
vote
1answer
63 views

What are “correlations”?

When working with realistic two-body hamiltonians, a direct diagonalization is almost always imposible. Thus one usually takes a procedure which yields an approximate solution. A well known approach ...
2
votes
2answers
237 views

What is the essential difference between a resonance and a particle?

Let me start by explaining my particle physics background is very patchy, so this question may not be as coherent as I would like it to be. In general terms, what is the difference between a ...
6
votes
2answers
303 views

What is the difference between a “model” and a “theory”?

In my past questions I have used the terms "model" and "theory" interchangeably. So we have statements along the lines of The Standard Model is our best theory of particle physics but I have also ...
1
vote
2answers
157 views

Locally flat coordinate and Locally inertial frame

I am having some doubts on myself regarding the above concepts in General Relativity. First, I want to point out how I understand them so far. A male observer follows a timelike worldline ($\gamma$) ...
0
votes
2answers
51 views

What does the term 'hyperbolic model' mean?

I am reading this non-linear discrete dynamical system paper. The authors mention the term hyperbolic model. What does that mean?
1
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3answers
110 views

“Complete” confusion

The word "complete" seems to be used in several distinct ways. Perhaps my confusion is as much linguistic as mathematical? A basis, by definition, spans the space; some books call this "complete" -- ...
1
vote
1answer
36 views

What is meant by “the superpotential is not renormalized”?

Reading about supersymmetry I often read the phrase because of the non-renormalization theorems the superpotential is not renormalized. I would like someone to be more explicit on what is ...
0
votes
0answers
17 views

Is there a name for the squared refractive index?

In studying wave propagation through multilayers, the squared refractive index $n^2$ is a more pertinent parameter than $n$ itself. Is there a received name for $n^2$? Of course, as long as there is ...
6
votes
3answers
365 views

Is a “shift in the meaning” of Accuracy and Precision occurring?

Accuracy and precision are among the most fundamental concepts in experimental physics, and, I always believed, completely unambiguous. Recently I found that the Wikipedia article on Accuracy and ...
2
votes
3answers
388 views

Conversion of ideal gas to real gas via $Z$ compression factor

The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
12
votes
10answers
14k views

What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)?

This is a confused part ever since I started learning electricity. What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? All of them have ...
1
vote
1answer
48 views

Is there a name for the linear quantity corresponding to the (quadratic) “interval $\Delta s^2$”?

Recently it has been affirmed here (again) that the quantity called "interval (also 'spacetime interval' or 'invariant interval')" is referring to two (in general distinct) events as arguments, such ...
1
vote
1answer
73 views

Is 'Boltzon' an accepted name for particles following Maxwell-Boltzmann (MB) statistics?

In my curriculum during one of my statistical mechanics visiting lecture classes, our teacher was referring comparatively macro particles following MB statistics as "Boltzon". But I have searched ...
1
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2answers
94 views

Why can't we precisely define physics? [closed]

While reading a textbook, I came across this statement: "A precise definition of physics is neither possible nor necessary." I was curious why it is not possible but the textbook never ...
3
votes
4answers
6k views

What is the difference between air pressure and atmospheric pressure?

I know that air pressure and temperature are inversely proportional. Now I saw in a book that "Atmospheric pressure decreases as we go higher and higher." But at greater heights the temperature ...
0
votes
1answer
23 views

Motion in oscillating field: expanding in powers of $\xi$ [closed]

I'm reading an excerpt from Landau/Lifschitz's Mechanics book about motion in oscillating fields. Two equations for the motion of a particle with mass $m$ are set out: \begin{equation} m\ddot{x} = ...
0
votes
2answers
122 views

What is the difference between configuration space and phase space?

What is the difference between configuration space and phase space? In particular, I notices that Lagrangians are defined over configuration space and Hamiltonians over phase space. Liouville's ...