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

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4
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2answers
665 views

In interferometry, what is the origin of the name “Airy function”?

In interferometry (specifically, in the domain of Fabry-Perot cavities), the function $$f(\phi) = \frac{1}{1 + F \sin^2 \phi},$$ which describes the shape of the resonant structure of the cavity, is ...
0
votes
1answer
23 views

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

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 $Q$ ...
0
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0answers
15 views

How did each Base Quantity get it's name? [on hold]

I've tried searching everywhere, but I can't seem to find anything related to how the quantities got named! Base Quantities: 1.Mass 2.Distance 3.Time 4.Temperature 5.Electric Current 6. Quantity of a ...
0
votes
2answers
35 views

Difference between circular motion and rotational motion

Are rotational motion and circular motion different or the same? If different then when can we say that a body is in circular motion, and when it's in rotational motion? I find several answers where ...
1
vote
0answers
33 views

What is a Fermi arc?

What is meant with a Fermi arc, for example, in the context of Weyl semimetals? Is this the just a one-dimensional Fermi surface? For example, in electron-doped graphene, the Fermi surface consists ...
9
votes
5answers
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?
2
votes
1answer
55 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
votes
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
18 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 ...
21
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2answers
2k views

Definitions: 'locality' vs 'causality'

I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
1
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2answers
240 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 ...
1
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2answers
121 views

What is a self adjusting force?

What is a self adjusting force? I searched it everywhere on internet but not got my answer and I have no other source to get its answer except this site so please help me.
0
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3answers
36 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 ...
1
vote
1answer
27 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
1k 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
votes
0answers
62 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 ...
2
votes
2answers
24 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 ...
0
votes
1answer
26 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 ...
0
votes
1answer
90 views

Second law of thermodynamics (in terms of entropy)

Is the second law of thermodynamics (in terms of entropy) for closed systems or isolated systems? I thought it must be valid for isolated systems, such as the Universe. But the book Fundamentals of ...
2
votes
1answer
19 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
210 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 ...
0
votes
2answers
99 views

What is the amplitude of a (EM) wave?

Amplitude is: Peak-to-peak amplitude is the change between peak (highest amplitude value) and trough (lowest amplitude value, which can be negative). With appropriate circuitry, peak-to-peak ...
1
vote
1answer
69 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
votes
1answer
39 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 ...
4
votes
3answers
10k 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 ...
0
votes
7answers
177 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
16 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
votes
1answer
36 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
25 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?
4
votes
0answers
86 views

Why does Wikipedia equate hidden symmetry with 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 ...
0
votes
1answer
80 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?
1
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2answers
204 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
33 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?
1
vote
1answer
76 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 ...
2
votes
1answer
5k 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 ...
-2
votes
1answer
38 views

Spin-resolved current [closed]

What is spin-revolved current? Is it the spin current?
0
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0answers
19 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 ...
5
votes
5answers
328 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. ...
2
votes
4answers
420 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 ...
0
votes
1answer
18 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
8k 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
20 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
votes
3answers
45 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
98 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 ...
1
vote
2answers
35 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
42 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 ...
0
votes
0answers
48 views

Terminology: Gauge stress?

When a material is loaded with a force, the stress at some location in the material is defined as the applied force per unit of cross-sectional area. If I have a material submerged in pressurized ...
1
vote
0answers
30 views

What are the differences between logistic map, poincaré map, attractor, phase portrait, bifurcation diagram? [closed]

What are the differences between Logistic map, Poincaré map, Attractor, Phase portrait, Bifurcation diagram Currently I became interested in chaos theory and non-linear dynamics. While ...
1
vote
1answer
50 views

What is the defintion of a current-current diagram?

Right now I am facing some Feynman diagram calculations and in the instructions I am reading the phrase current-current diagram appears quite often so I wanted to know: What is the definition of a ...
0
votes
3answers
57 views

How to tell if area is displacement or distance?

why is it not called "velocity v. time"? how do you know? If the y-value can be either positive or negative, the direction is then indicated. i think this is why it should be called velocity but ...