Questions tagged [terminology]

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

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2answers
518 views

What is the difference between sound and vibration?

As far as I know, the only difference between sound and vibration is that sound propagates but vibration does not. In most cases, they are the same. Please help clarify these concepts.
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45 views

System in Lieb and Yngvason's paper [closed]

I'm reading The Physics and Mathematics of the Second Law of Thermodynamics and have a question. In A. Basic concepts 1. Systems and their state spaces, the term system is formally introduced and one ...
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1answer
71 views

Transmission coefficient and transmission probability

Are transmission coefficient and transmission probability the same terms? If not, could you please explain how they are related to each other?
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2answers
54 views

What is meant by “linear” in non-equilibrium thermodynamics?

I'm trying to learn a bit about non-equilibrium thermodynamics, and am currently reading de Groot and Mazur. In it, there is a quote right in the beginning, talking about the phenomenological ...
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1answer
2k views

First quantization vs second quantization

What is the difference between first quantization and second quantization and where does the name second quantization come from?
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1answer
39 views

Einstein solid degree of freedom

I was studying from Schroeder's thermal physics book. When it talks about Einstein solids it says that they have 2 degrees of freedom thus $U=NkT$ However, I thought when we talk about Einstein ...
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1answer
126 views

Spring constant, but intrinsic to material, not rest length

If you have two metal springs that are coiled in the same way, but one is twice the length of the other, the spring constant will be half as large for the longer one. That makes sense of course. What'...
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1answer
28 views

Difference between time series and trajectory terminology

What is the difference between trajectory and time series? To me both seem the same thing. In the 3D diagram (cube picture on left of Fig.2 from the paper titled “Review and comparative evaluation of ...
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2answers
83 views

Why is particle physics called high energy physics? [duplicate]

The highest energy accelerator till date is the LHC which operates at an energy scale of perhaps 10-100 TeV. In SI units this is about $\sim 10^{-6}-10^{-5}$ Joule which is several orders of magnitude ...
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2answers
63 views

Technical question on definition of free fall

Free fall is any motion of a body where gravity is the only acceleration acting upon it. But, what if I threw an object from a certain altitude, and had two jetpacks put on it , one providing ...
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2answers
151 views

Difference between Oscillatory motion and vibratory motion

What is the difference between oscillatory motion and vibratory motion. I have read in my book that "If the amplitude of oscillatory motion is extremely small,the motion is called vibratory motion". ...
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2answers
55 views

What does 'per unit frequency' refer to?

We were discussing Kirchoff's theorem on blackbody radiation in class today and the equation was: $$e_{f}= J(f,T)$$ $e_f$ was defined as power per unit area per unit frequency. What does per unit ...
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1answer
65 views

What's the difference between canonical quantization and second quantization?

I am wondering the difference between the canonical quantization and the second quantization in quantum field theory. For example, a harmonic chain, one can write down its lagrangian density $\...
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93 views

$n$-body problem = many-body problem? [closed]

Are the terms "$n$-body problem" and "many-body problem" synonymous? Or does one refer to a numerical problem an the other to an analytical problem?
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Reversed effective force in D'Alembert's Principle [duplicate]

In D'Alembert's Principle,what is reversed effective forces and how to determine it's direction?
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24 views

What is the static exchange approximation?

In this paper, on the 4th page (and throughout), they talk about studying electron-helium scattering in the "static-exchange approximation". I have scoured the literature and have not been able to ...
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3answers
1k views

Planets and Pluto? Neptune?

If one of the rules to be a planet is that it needs to clear ALL objects from their orbit, does this also make Neptune a non-planet? Since it has thus far failed to clear Pluto from it's orbit. Or ...
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1answer
58 views

What is the difference between degree celsius and celsius degree? [duplicate]

It seems similar but can you guys please answer it that what is a specific difference between degree celsius and celsius degree?
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4answers
140 views

Is the notion of 'weight of Earth' meaningless?

I am not talking about the distinction between mass and weight, just the concept of 'weight'. In University physics (book by Young & Freedman, 14th Ed.) it is given that the weight of an object ...
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0answers
46 views

Dimension of the candela unit: What does J stand for? [migrated]

The J symbol can represent the unit of energy but it's also the symbol for the dimension of the candela (or luminous intensity). For the energy unit, it clearly comes from the family name of the ...
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1answer
62 views

Terminology for time derivative of speed (not velocity)

Is there any standard terminology for the derivative of the magnitude of velocity with respect to time (suitable for use in first-year Calculus)? The word ‘acceleration’, in its technical sense, is ...
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3answers
53 views

Is a rotating object moving or stationary?

Because it rotates in situ, its center of mass does not move, so it is static, but it is rotating, so it is not static, then is it static or moving?
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3answers
2k views

Definition of non-degenerate metric tensor

We know that a metric has a property which is called non-degeneracy. I was searching for what does that mean and saw it associated with the fact that $det(g_{\mu\nu})\neq0$. How does this relate to ...
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36 views

Is the designation “chemical reaction” right for vibrational and electronic excitation of particles?

I'm currently doing my Master's thesis, which focuses on Atmosphere Reentry Thermodynamics and Kinetics. Due to the importance of this work, I would like to use the best terms to describe any ...
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1answer
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Difference between an electron wiggler and an undulator?

Both wigglers and undulators use periodic magnetic fields applied to stored relativistic electron beams to produce intense beams of UV or X-rays that can be used in a wide range of condensed matter ...
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7answers
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Are matrices and second rank tensors the same thing?

Tensors are mathematical objects that are needed in physics to define certain quantities. I have a couple of questions regarding them that need to be clarified: Are matrices and second rank tensors ...
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1answer
66 views

If we say “an object is at rest,” can we also say “the object is moving at a constant velocity?” [closed]

If we say "an object is at rest," can we also say "the object is moving at a constant velocity?" Of course, the constant velocity would be zero, so it's mathematically sound. However, the wording ...
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1answer
41 views

What “luminosity distance” means in a general spacetime?

In the paper "Asymptotic Symmetries in Gravitational Theory" by R. Sachs from 1962, the author says the following: In analyzing gravitational fields it is sometimes useful to introduce coordinates ...
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2answers
221 views

Gruchestein Effect?

I overheard that name in a conversation, but not very clearly. I can't find anything on Google, probably because of my spelling is completely wrong. Does anybody knows about an effect with a similar ...
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3answers
2k views

Kinematic Viscosity

How would you define kinematic viscosity? What does it physically represent? Around the Internet I've found it defined as just a ratio, and that's it. I saw in an answer that I can think of it as "...
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1answer
126 views

Difference between a “mode” and a “state” in quantum mechanics?

I am studying the book Introductory Quantum Optics by Gerry & Knight at the moment and as a reader, I stumble upon their seemingly interchangable use of the tems "mode" and "state". As far as I ...
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0answers
28 views

What is meant by the vacuum structure of ABJM theory?

I was reading the paper Large $N$ behavior of mass deformed ABJM theory. It talks about the vacuum structure of the (mass deformed) ABJM thoery. What does vacuum structure mean in general or in ...
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2answers
162 views

Sound speed vs Speed of sound

Are 'sound speed' and 'speed of sound' the same thing? If not, what is the difference? If they are, could you clarify how the speed of sound applies in the below description of gaseous clouds? ...
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4answers
1k views

What is the difference between uniform velocity and constant velocity? [closed]

I think that uniform velocity implies constant speed but not constant direction. while constant velocity implies constant speed without any changes in direction. Both tell us that there's no ...
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7answers
2k views

Is the Momentum Operator a Postulate?

I've been studying the postulates of QM and seeing how to derive important ideas from them. One thing that I haven't been able to derive from them, however, is the identity of the momentum operator. ...
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What is Rectangular Simple Harmonic Motion (SHM)?

While studying Simple Harmonic Motion and Lissajous figure, I found a term called Rectangular SHM. But what is it actually? Is it something like square wave? What is the difference between Linear and ...
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1answer
128 views

What does “interference” mean when referring to quantum computation?

I keep coming across off-handed references to "interference" in the context of discussions of the unique features of quantum computers. I understand that these references may mean (or seem to mean) ...
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7 views

Terms time resolved vs. stroboscopic measurements

I use the term stroboscopic for an experiment, where the stroboscopic effect is part of the experimental setup. And I call an experiment a ...
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1answer
117 views

Have there been more distinctive names suggested for neutrino mass states $\nu_1, \nu_2, \nu_3$?

The different mass states of neutrinos are generally named $\nu_1, \nu_2, \nu_3$. By comparison, the names of quark mass states (up, ...
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5answers
31k views

What is sound and how is it produced?

I've been using the term "sound" all my life, but I really have no clue as to what sound exactly is or how it is created. What is sound? How is it produced? Can it be measured?
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1answer
34 views

Abelian and non-Abelian holonomies

I read the article Geometric Manipulation of Trapped Ions for Quantum Computation, and it mentioned “Abelian and non-Abelian geometric operations (holonomies)”. I know what is holonomy, and what is ...
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315 views

Effective Field Theories of QCD

Recently, I am studying the online course Effective Field Theory provided by MIT OCW. Prof. Stewart gives a nice picture to summarize the effective theories: As a newbie in this field (I only have a ...
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1answer
973 views

What is a Witten diagram?

Recently I heard the terminology of Witten diagram. Studying QFT, I frequently see Feynman diagrams and use them to compute scattering amplitudes, one-loop corrections and so on. In string theory ...
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62 views

Are there names for Helium (He) emission lines like the Lyman/Balmer/Paschen series in Hydrogen?

Just wondering if helium emission lines have names like hydrogen lines. For instance the Balmer series is: $$H_{\alpha}, H_{\beta}, H_{\gamma}, H_{\delta}...$$ The Lyman series is: $$L_{\alpha}, ...
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4k views

Is the Big Bang defined as before or after Inflation?

Is the Big Bang defined as before or after Inflation? Seems like a simple enough question to answer right? And if just yesterday I were to encounter this, I'd have given a definite answer. But I've ...
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1answer
48 views

What do we really mean by the word “light”? [closed]

Does the term "light" refer to any electromagnetic wave or just the visible spectrum?
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What is an electrified channel?

I've been asked to create a sketch of an electrified channel. I've never heard of this terminology before. I tried to Google it and it came up with either guitar related answers, or a few about ...
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1answer
27 views

What is the difference between longitudinal chromatic aberration and spherochromatism?

In lens design textbooks, a distinction is often made between longitudinal chromatic aberration and spherochromatism. (See for instance Kingslake's lens design book.) What is simple way to understand ...
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2answers
58 views

“Energy transfer” and “Energy transport” [closed]

Are the terms "energy transfer" and "energy transport" sometimes or always interchangeable? My own surmise is that the term "energy transfer" is slightly more general: "energy transport" refers to ...
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1answer
35 views

Pseudotensors for describing physical quantities

I have been reading about tensors from Mathematical methods for Physics and Engineering, by K.F. Riley, M.P. Hobson and S.J. Bence. And there are a couple of things i am not getting. On page 949 (...