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Questions tagged [terminology]

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

3
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1answer
202 views

What's the difference between linearly polarised and plane-polarised waves?

To explain polarisation, my book gives an example of a transverse wave in a string, and explains as: Since each point on the string moves on a straight line, the wave is also referred to as a ...
0
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2answers
98 views

Newton's Second Law of Motion - Net Force Vs. Velocity

I am wondering about a question regarding Newton's Second Law of Motion. For an object to have a constant velocity, it means the total net force is 0 since there is no acceleration. Does that mean ...
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1answer
82 views

What's the difference between a generating function and a generator?

Usually in physics we use the notion generator to describe the infinitesimal elements associated with any finite Lie group transformation. But in the context of the Hamiltonian formalism, all authors ...
2
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1answer
75 views

Different Schwinger-Dyson Equations

In the literature on QFT there are a lot of different equations that are all called "Schwinger-Dyson equation" so I wanted to know how are they related and if they have proper names. The first ...
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2answers
59 views

Is there a name for the un-integrated Lagrangian?

The "action" is a functional of fields and their derivatives integrated over a space-time volume. A Lagrangian is just integrated over the space dimensions. But what is the name of the thing to be ...
3
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1answer
90 views

What is energy in quantum mechanics?

Is it wrong to say energy is the expectation value of Hamiltonian? Or should I say energy is the eigenvalue of Hamiltonian?
2
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2answers
111 views

What's the name of the symmetry $ L \to L + \frac{d \Lambda}{dt}$?

In the Lagrangian formulation of Classical Mechanics, we have the freedom to add a total time derivative of an arbitrary function $\Lambda$ to the Lagrangian: $$ L \to L + \frac{d \Lambda}{dt} . $$ ...
2
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1answer
46 views

What is the relation between incompressible flow and laminar flow?

I have a small question about dynamics. My textbook shows me the velocity profile for an incompressible flow, which has a parabolic profile. Does this automatically mean it's laminar flow? I don't ...
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1answer
72 views

“Killing leaves” in General Relativity?

I now about Killing vector fields in GR but recently stumbled upon the notion of "Killing leaves" and couldn't find any simple explanation of this notion. For example, this paper writes: "integral ...
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2answers
95 views

Meaning of the term $V(x)$ in the Schrodinger equation [closed]

I'm new to quantum mechanics and I am currently trying to understand finite potential well (although my question is not specific to finite potential well ). In the Schrodinger equation, many texts ...
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1answer
34 views

What is the difference between supersymmetry and MSSM?

What is the difference between supersymmetry and MSSM? Please explain in a simple language i am just a beginner of supersymmetry
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2answers
70 views

What does Dirac mean by “proximity”?

I was reading Dirac's "The Principles of Quantum Mechanics" and on page 7 he makes the following statement: "Like the fundamental concepts (proximity, identity) which everyone must learn on his ...
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1answer
52 views

What are three-point functions?

I came across this term while I was trying to read this paper related CFT correlators. Can some please take some time out to explain what does it mean in general?
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0answers
27 views

I want to know the name of a type of cable

I was doing an experiment on photoelectric effect. The photocell had a cable from which both the anode and cathode wires came out. I was told to find out the name of the cable. here's a skillfully ...
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0answers
56 views

Is the work function a function? [closed]

The work function is the energy an electron needs to leave the metal. Why is it called a function? Its value is different for different metals, but that doesn't make it a function; density and melting ...
3
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2answers
115 views

Can magnitude be negative?

My teacher told that magnitude is the positive value of that quantity or the modulus of that quantity. he also told that vector quantities have both magnitude and direction and scalar quantities have ...
16
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2answers
2k views

Can two atoms be a crystal?

In the physics literature, you can often find the term "two-ion crystal", when talking about two ions that are confined in a e.g. Paul trap. How is this possible? Shouldn't a crystal be a structure ...
0
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1answer
103 views

What is clean limit and dirty limit?

In superconductor there has two limits, one called as clean and other one called dirty limit. But what are that meaning? What means clean and dirty? How the coherence length depends on the electron ...
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0answers
47 views

Is there a difference between false (metastable) and local equilibria?

Or is it permissible to use the terms interchangeably? If there is a difference, what is it?
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2answers
198 views

What are “large hadrons”? Are there also “small hadrons”?

The BBC News article Cern plans even larger hadron collider for physics search says: The difficulty with Cern's proposals for a larger Large Hadron Collider is that no one knows what energies will ...
2
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1answer
59 views

Meaning of ft-values in nuclear physics

What is the "physical" meaning of the ft-value for a decay channel? From what I understand, the ft-value is inversely proportional to the square of the matrix element, hence I would expect a larger ft-...
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1answer
37 views

What does the term “no slipping” mean in mechanics?

Say, I have two blocks. One block is on top of the other. Suppose friction is present everywhere. What is the condition for no slipping?
0
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1answer
57 views

What does $\mathcal{N}$ refer to in Gauge theories?

Context: I am a second-year (undergraduate) physics major applying for a summer research position. The investigator is working on Quiver Gauge Theories and in response to my inquiry email he told me ...
3
votes
4answers
616 views

What are the differences between specific latent heat and latent heat?

What are the differences between specific latent heat and latent heat? As far as I know, latent heat is the heat required or released during the change of state, without change of temperature. So ...
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2answers
66 views

Angular Momentum of a Rigid body

When defining angular momentum or rather calculating angular momentum what is the difference in the use of the terms "with respect to" , "about a point" or "in the frame of" ? Are the angular ...
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1answer
45 views

Are Generations and Families of elementary fermions one and the same?

I've seen both terms being used in papers and it seems to me they essentially mean the same thing referring to three generations of leptons and quarks as families. Is this true or are there some ...
1
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1answer
75 views

What is 'definite' variable in QM?

I have gone through a few of the questions on the website regarding this particular query, but I have not understood what they meant. When a question says that a particle has definite momentum, are ...
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1answer
34 views

Name of measurement expressed as the sum of different units

In a paper I'm writing, I want to make a comment about errors in an old paper made when doing arithmetic with measurements expressed as as the sum of quantities with two or more different units, for ...
25
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4answers
988 views

What precisely is a *classical* spin-1/2 particle?

I was recently having a Twitter conversation with a UC Riverside Prof. John Carlos Baez about Geometric Quantization, and he said (about his work) that "Right. For example, you can get the ...
16
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3answers
2k views

Is the second law of thermodynamics a “no-go” theorem?

As defined here, there are several no-go theorems in theoretical physics. These theorems are statements of impossibility. The second law of thermodynamics may be stated in several ways, some of which ...
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1answer
117 views

Difference classical and statistical thermodynamics

What should I read to link between classical thermodynamics or engineerig thermodynamics and statistical mechanics?
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2answers
262 views

Normal force not perpendicular to the surface

In my class about mechanics i had to solve this problem, but it was never really explained. The solution is found beneath in a picture. In the solution they also calculate the angle of the normal ...
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3answers
127 views

Hooke's Law: Is the extension of a spring the same as its displacement?

This question might make no sense, but I'd like to ask it anyway. The elastic potential energy of a spring is the area under the force-extension/compression graph. The work done on a spring is ...
0
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2answers
63 views

Range of a projectile

My notes say that the range of a projectile is equal to $$\sin(2\theta)(V_0^2/g) .$$ This equation implies that a ball shot at $0$ degrees has zero range but this isn't true is it? If I kick a ...
1
vote
1answer
35 views

What's a word that encompasses both transmit and receive?

Is there a word that can be used to describe in a general sense the action of an antenna, whether transmitting or receiving? My best guess is "couple" as in coupling energy from a wire to EM wave, ...
3
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1answer
69 views

Exact form of the damped wave equation

The undamped wave equation has the standard form \begin{equation*} \frac{\partial^2 \psi}{\partial t^2}=c^2\nabla^2\psi \end{equation*} while the damped wave equation is frequenly found written in ...
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1answer
42 views

What the difference is between Størmer Verlet and regular Verlet method?

I was wondering what the difference is between the Størmer Verlet method and the regular Verlet method, if there is any.
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1answer
392 views

What is a homogeneous magnetic field?

What does it mean when one says that a magnetic field is a homogeneous magnetic field?
2
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2answers
52 views

What is the difference between “monochromatic” and “impulse” force?

In a paper I am reading (linked below), the following is stated: The transient motions of the sphere and the gas bubble in the elastic, incompressible, inviscous medium are investigated in response ...
2
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1answer
124 views

Why is the Fermi Golden rule called so?

I was studying time dependent perturbation theory and this rule came under the case of constant (weak) perturbations. I understood the rule and the derivation but what I cannot understand is that is ...
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3answers
257 views

What would be the minimum velocity of a particle performing S.H.M.?

We were asked a simple question on a test: What is the maximum and minimum velocity of a particle performing an SHM? Note here that we're talking about a generic standard SHM here. If the maximum ...
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1answer
87 views

Define System of particles [duplicate]

What really is a system in physics? In laws of motion a system contains particles with same acceleration but when I studied conservation of linear momentum i found that system is just a collection of ...
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2answers
162 views

What is an anisotropic harmonic oscillator?

I can't find any explanation of it anywhere in the internet. How is it different from an isotropic harmonic oscillator?
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2answers
61 views

Is second harmonic generation a special case of high harmonic generation?

That might be a strange question, but while I was researching for these topics, I never found an explicit statement that would answer that question. (That might be because of the different ...
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4answers
532 views

Is the term “quantum fluctuation” an aide to understanding? [closed]

I would like to ask if anyone has found a tight enough way to define the term "quantum fluctuation" so that it can become a useful rather than a misleading piece of physics terminology. Terminology ...
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1answer
100 views

Meaning of the subscripts $L,R$ for the two component Weyl spinors $\phi_{L,R}$

For a Dirac spinor $\psi$, its chiral projections are $\psi_{L,R}$ are defined as $$\psi_{R,L}=\frac{1}{2}(1\mp\gamma^5)\psi.\tag{1}$$ Acting with the chirality operator $\gamma^5$, we find $$\gamma^5\...
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2answers
250 views

What is the $\,\phi=0\,$ gauge called?

In electromagnetism textbooks, the gauges most often talked about are the Lorenz gauge and Coulomb gauge. Sometimes it's convenient to work in a gauge in which there is only the vector potential $\vec{...
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1answer
191 views

Action angle variables and Action

Action given by principle of least action ($S$) and action variable given by action angle variable theory ($J$) are same?
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1answer
112 views

Uncertainty Principle - Accuracy or Precision? [closed]

While discussing about the Uncertainty Principle, some books use the word 'accuracy' and some other books use the word 'precision'. Some even use them both interchangeably. For instance, in Griffiths' ...
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1answer
37 views

What is a quasistationary approximation

I was reading an article which states : The linear-stability analysis for this system can be performed in complete generality; but it will be best for purposes of this review to go directly to ...