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

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2answers
458 views

What is meant by thermal penetration depth?

What is meant by thermal penetration depth? I am doing a project on Thermoacoustics. while researching I came across about thermal penetration depth.I searched over the net but i didn't get a clear ...
1
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1answer
101 views

Definition of the “support” of the reduced density matrix

Some of the papers in condensed matter physics use the word "support" (space). For example, the following papers use the support especially for the reduced density matrix. ...
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0answers
39 views

Meaning of 'nuclear surface vibrations'?

Would like to know the meaning of nuclear surface vibrations as mentioned by Bohr in his paper titled 'The coupling of nuclear surface vibrations to the motion of individual nucleons'. The paper talks ...
0
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1answer
43 views

Is “approximative reduction” general knowledge to physicists?

I came across this concept called "approximative reduction", about which there are some papers, e.g. in this collection called Structure and Approximation in Physical Theories. Very briefly, it ...
2
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0answers
33 views

Nomenclature of nuclear excited states

I read in an online portal about $^{112}$Sn nucleus making a transition from $0_{g.s}^{+} \rightarrow 2_{1}^{+}$ state. Also, some higher excited states were named as $0_{2}^{+}$, $3_{1}^{-}$, etc. ...
0
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1answer
118 views

What did Feynman mean by 'energy shift' here?

I was reading Feynman's Lectures III's Chapter 10: Other Two-State Systems. There he discussed about hydrogen molecular ion having two base states: The amplitude of the molecule to go from ...
23
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5answers
3k views

Is there a rigorous definition of 'much greater than'?

I have encountered $\gg$ in many physics text books where it's used as a relation between constants or functions but in none of the text books I have read is it properly defined anywhere. If $A \gg ...
0
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2answers
70 views

Terminology for “measurable” and “hidden” realms in quantum physics

Please excuse if some of my terminology is vague, the whole point of this question is to clarify terminology. In quantum physics, one frequently encounters situations where there are some kind of two ...
4
votes
4answers
7k views

Catapult vs. Trebuchet

I have been looking at trebuchet designs lately, and I have noticed that most, if not all, have a sling attached to them. Without such a sling, the machine would be a catapult. In terms of the speed ...
0
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1answer
52 views

What is the difference between damping and friction?

What is the difference between damping and friction? Both of them slows down any moving system. So whats the conceptual difference between them?
2
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1answer
347 views

At CERN - What do you call the moment (event) particles crash together in the particle accelerator? [closed]

At CERN - What do you call the moment (event) particles crash together in the particle accelerator? At CERN they crash different particles together and measure what comes out. What is the name of the ...
2
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3answers
288 views

Difference between discretization and quantization in physics

I am just trying to understand the fundamental difference between these two concepts in physics: From discreteness of some quantity: one usually interprets it as a quantity being only able to take ...
0
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0answers
21 views

Flamant's use of mass and weight

I apologize for the stupid question, but I've consulted teachers and found their answers unsatisfactory. Professor E.Brune, in the XIX century, delivered a course on l'École des beaux-arts on ...
0
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4answers
136 views

What is the 'normal/standard' formulation of quantum mechanics called?

I know of at least three equivalent formulations of QM: The "normal/standard" one, dealing with Hilbert spaces and state vectors. The Feynman path-integral formulation. The Wigner-Weyl phase space ...
0
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1answer
63 views

What do we mean by saying that one clock had been “running slower” than another clock; or that two clocks had been “running equally”?

Several posts on this site, especially on the topic of relativity, refer to comparisons between clocks in terms of their "running"; one having "run faster" than the other, one having "run slower" than ...
0
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1answer
119 views

What is the conformal mode of a metric?

I have a problem in terminology. This article talks about the conformal mode of a physical metric. I know what a conformal transformation is. But what is the conformal mode of a metric?
3
votes
4answers
1k views

Is there a difference between Hertz and 'frames per second'?

It's not uncommon that the term 'frames per second' (sometimes abbreviated as fps or FPS) is associated with, or even equated to, the unit Hertz (Hz). I'm not exactly sure how these two concepts ...
9
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6answers
2k views

If the Earth is in constant motion then why do we say that an object is in a state of rest?

I got this question as my physics class homework for tomorrow. Anyone please help me out. If Earth constantly rotates and revolves, then how can we call an object in a state of rest?
0
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1answer
45 views

Does motion with constant proper acceleration, in a flat region, necessarily mean straight hyperbolic motion?

Is motion of a participant with constant proper acceleration, in a flat region, necessarily straight, hyperbolic motion (with respect to members of any inertial system, in that region)? Or is for ...
0
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2answers
284 views

Quantum hadrodynamics

What is quantum hadrodynamics? Can anybody give a proper explanation? What are the standard books and sources of information that can be found on the internet for better understanding?
3
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1answer
9k views

What is the difference between Quantum Physics, Quantum Theory, Quantum Mechanics, and Quantum Field Theory?

What is the difference between Quantum Physics, Quantum Theory, Quantum Mechanics, and Quantum Field Theory? Are they the same subject? I believe that they are not the same subject! Maybe there is not ...
0
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1answer
456 views

What is the recommended symbol for Volumetric flow rate? [closed]

I'm currently working on a paper with a mathematician. He always writes $\dot Q$ as well as $\dot V$ for volumetric flow rate and claims both are standard notations. Till now I always used $Q$ ...
2
votes
1answer
169 views

Difference between symmetry and invariance

I'm wondering what's the real difference between symmetry and invariance in Physics? I believe that sometimes the two words are given the same meaning and some other times they are used in a different ...
0
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1answer
2k views

Definition of Free Electrons and Mobile Charges?

Could someone please give me a good definition of the following electric terms? Despite what searching I have done, I have not come across a definition that I have found clear for me to understand: ...
0
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0answers
38 views

Laser Energy Level Transitions

I am new to Laser Physics. While looking at the Energy Levels diagram for the Laser Transition of ND:YAG laser, I see energy levels labeled like 4F(3/2), 4I(15/2),.. I did not come across such energy ...
0
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3answers
71 views

Nonlocal dielectric function - what does it mean?

I'm reading this* article and in the second sentence of introduction I encountered a term I haven't heard of before. Namely: nonlocal dielectric function. What does this nonlocality mean? And how does ...
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1answer
74 views

Conventionally, how many amplitudes does a (harmonic) oscillator pass through in one full cycle? [closed]

I don't know the typical scientific convention. My book says there are 4 amplitude. But no matter where I start the oscillator , the answer is at most 3.
5
votes
4answers
2k views

What is the specific meaning of “Fourier frequency” (as opposed to simply “frequency”)?

I've noticed that many journal articles (in optics) use the phrase "Fourier frequency" to describe, well, the frequency of something. Google scholar search for "Fourier frequency". Example: ...
0
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0answers
158 views

Definition of Hamilton operator

The Hamilton operator is by definition a self-adjoint operator $H\text{: }D\left(H\right)\to\mathcal{H}$ with $D\left(H\right)\subset\mathcal{H}$ a dense linear subspace of the Hilbert space ...
3
votes
2answers
71 views

What S means in S-duality?

As I know, there are many dualities related to S-duality. For example, Montonen-Olive duality, Seiberg duality. and so on. so, I wonder that what "S" means in the term "S-duality". If this is a stupid ...
1
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1answer
31 views

Formula relating sum of values of a function to its integral

I came across the above formula in some quantum mechanics lecture notes explaining the Casimir effect. Anyone seen it before if so could you please tell me its 'name'. B refers to the Bernoulli ...
2
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1answer
29 views

Definition of a Supercluster

A group of astronomers in September 2014 redefined what classifies a supercluster. Before this, the supercluster where the Milky Way resides was the Virgo Supercluster. Now, the Virgo Supercluster ...
6
votes
1answer
351 views

What does “P-wave” mean when referring to a particle?

In scattering theory, P wave means $l=1$, where $l$ is the azimuthal quantum number. However, what does P wave mean when referring to particle states? For example, in this paper (arXiv link), the ...
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1answer
279 views

Meaning of the term 'bulk'

I have recently started reading literature on 2 dimensional systems in Condensed matter. While reading, I frequently came across the word 'bulk'. Sometimes it referred to 2-D and sometimes to 3-D. I ...
0
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1answer
49 views

What is the $D_{x^2-y^2}$ symmetry/channel/instabilitied referred to with regards to super-conductivity?

I have been reading various articles on Renormalization group where they compute the flow of some parameter which becomes increasingly attractive and then say that parameter is responsible for Cooper ...
8
votes
3answers
31k views

What is difference between homogeneous vs isotropic material?

When we say a material is isotropic? When properties such as density, Young's modulus etc. are same in all directions. If these properties are direction dependent, then we can say that the material is ...
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7answers
918 views

What is inertia of a body?

The definition of inertia is "Inertia is the resistance offered by the body whenever its state of motion is changed." What is inertia of a body? Is inertia actually a force exerted by the body? If ...
0
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0answers
29 views

Rolling drag and action-reaction forces

I do not understand the two factors acting on the car during driving, they are Rolling drag which it is rolling resistance and action-reaction forces. If the Rolling friction reduces the the car ...
-2
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1answer
135 views

Tension in the string produced due to pulling vs pushing

I know that tension is produced when we pull the rope, but what if we push it? What would that be called? Is that tension too? Negative tension?
0
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0answers
27 views

Optical path length and extremum time taken in Fermat's principle [duplicate]

Could someone please explain what is meant by stationary optical path length and extremum time taken in Fermat's principle?
0
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2answers
50 views

In stellar astrophysics, what is the difference between protostellar disk and circumstellar disk?

I have noticed both the terms "protostellar disk" and "circumstellar disk" in the stellar astrophysics and exoplanet literature. What exactly is the difference?
-2
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1answer
44 views
1
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0answers
39 views

What is the difference between Reissner-Nordstrom (RN) black hole and dyonic black hole?

A RN black hole is a black hole with electric charge, and a dyonic black hole with both electric charge and magnetic charge. My Questions: Is the above statement correct? Is the charges the unique ...
0
votes
1answer
26 views

Correct terminology for when neutral atom is ionized due to an electric field?

An electric field will cause an induced dipole in neutral atoms when present - I presume that if the field were strong enough the magnitude of the polarization could exceed a critical length and cause ...
7
votes
4answers
9k views

What is “pure energy” in matter-antimatter annihilation made of?

I used to read the term "pure energy" in the context of matter-antimatter annihilation. Is the "pure energy" spoken of photons? Is it some form of heat? Some kind of particles with mass? ...
0
votes
1answer
45 views

Does “converge” mean intersecting and producing image when we are taking about convex lenses?

After reading the chapter on convex lens, I saw several places where "converge" is used. In the very beginning of the chapter, my book says "converging lenses bring light together". So I thought ...
0
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3answers
61 views

Wavelength vs Wavenumber etiquette

When am I supposed to use the terminology of EM "wavenumber", instead of "wavelength" (or frequency)? The concepts of wavelength and frequency are no problem for me, but wavenumber (number of ...
2
votes
2answers
124 views

What is high energy physics?

Is high energy physics the same as particle physics? Does research in high-energy physics include things like quantum gravity, string theory and quantum field theory? Is unifying the four ...
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2answers
127 views

Why do people say “finite temperature” instead of “nonzero/positive temperature”? [duplicate]

This question is about terminology. The term "finite temperature" is often used to mean positive temperature, or equivalently finite inverse temperature $\beta = 1/T$. It seems to me that better ...
1
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1answer
70 views

Is harmonic oscillator continuous variable system?

In the literature I have seen that the notions "our system is continuous variable system", "Hilbert space of our system is infinite" were used as if they were equivalent. For example for harmonic ...