Use this for questions relating to the proper use of physics terminology or nomenclature.
3
votes
3answers
190 views
What is a “Center Of Mass” issue of a Gorillapod?
I read somewhere that a Gorillapod may have "Center Of Mass" issues when used with the long lenses.
So, I wish to understand what is a "Center Of Mass" issue?
I have to clarify that I am NOT a ...
3
votes
2answers
134 views
Do generators belong to the Lie group or the Lie algebra?
In Physics papers, would it be correct to say that when there is mention of generators, they really mean the generators of the Lie algebra rather than generators of the Lie group? For example I've ...
3
votes
3answers
266 views
What is the difference between manifest Lorentz invariance and canonical Lorentz invariance?
I often read that the Lorentz symmetry is manifest in the path integral formulation but is not in the canonical quantization - what does this really mean?
3
votes
1answer
88 views
What the name of the evacuated glass gadget with black and white vanes that turn when a light is applied?
I remember a glass device my physics teacher had at high school which
Contained some vanes mounted somehow on a vertical axis, which were all black on one side and white on the other
Was in a ...
3
votes
2answers
414 views
Differences between classical, analytical, rational and theoretical mechanics
Can you explain me what are the differences between the four following subjects?
analytical mechanics
rational mechanics
classical mechanics
theoretical mechanics
3
votes
2answers
667 views
What is a non linear $\sigma$ model?
What exactly is a non linear $\sigma$ model? In many books one can view many different types of non linear $\sigma$ models but I don't understand what is the link between all of them and why it is ...
3
votes
1answer
222 views
What is “charge discreteness”?
I assume it is some kind of quantity. Google only made things more confusing.
I get that it has something to do with circuits.
I also get what a discrete charge is. In fact, I thought charges ...
3
votes
4answers
492 views
Basic question concerning pure energy
Inside the core of a star thermonuclear fusion reaction fuses hydrogen atom into helium releasing massive heat/light and energy.When a blackhole eats up enough stars and gases it devours itself by ...
3
votes
3answers
831 views
What's the difference between “boundary value problems” and “initial value problems”?
Mathematically speaking, is there any essential difference between initial value problems and boundary value problems?
The specification of the values of a function $f$ and the "velocities" ...
3
votes
1answer
164 views
What's a pseudo-rotation?
I'm sorry for this lexical, probably extremely elementary, question. But what is a pseudo-rotation? I just read this term for the first time, in the beginning of the 4th chapter book of CFT by Di ...
3
votes
3answers
117 views
What is the meaning of the word “Principle” in Physics?
What is the meaning of the word principle in Physics?
For example in the "action principle". Is it an action law, an action equation, or an unproved assumption? (I have an idea what an action is).
...
3
votes
1answer
184 views
What are Low-lying energy levels?
I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
3
votes
1answer
506 views
What phrases describe collisions with coefficients of restitution less than zero or greater than one?
The coefficient of restitution describes the elasticity of a collision:
1 = perfectly elastic, kinetic energy is conserved
0 = perfectly inelastic, the objects move at the same speed post impact
...
3
votes
2answers
482 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:
...
3
votes
0answers
48 views
The etymology of “Umbrella Sampling” [migrated]
I am just wondering where the term Umbrella Sampling came from. Is there another meaning of literal "umbrella" in physics or mathematics?
3
votes
0answers
103 views
Meaning of spin
I'm pretty astounded that I did not hear about this sooner, but in my course on QFT our professor told us that the concept of spin can be used to mean three things:
Mechanical spin (apparently a ...
3
votes
1answer
377 views
What's a better phrase than “speed of light” for the universal spacetime speed constant? [closed]
The phrase "speed of light" is commonly used for the constant c =3E8 m/s, a feature that's "hardcoded" into the structure of spacetime. All massless waves and particles move at this speed, and it's a ...
2
votes
3answers
355 views
Opposite of Cryogenics
Cryogenics is related to very low temperatures, so, what is the term when referring to very high temperatures?
2
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2answers
107 views
Representations of Lie algebras in physics
Why is an invariant vector subspace sometimes called a representation? For example in Lie algebras, say su(3), the subspace characterized by the highest weight (1,0) is an irreducible representation ...
2
votes
2answers
162 views
What are the differences between indistinguishable and identical?
What is the difference between indistinguishable particles and identical particles?
2
votes
2answers
383 views
What the difference between “orbital” and “orbit”?
What's the difference between "ortibal" and "orbit"?
Which one should be used in physics?
In quantum mechanics, is "atomic orbital" or "atomic orbit" used?
And what about in classical mechanics? A ...
2
votes
2answers
2k views
What's the difference between constitutive laws and governing equations?
I'm studying about the finite element method in a class but I don't come from a civil engineering background. Anyways, it hasn't been made clear to me what the difference between constitutive laws and ...
2
votes
3answers
2k views
Torque vs Moment
I was wondering, why in Newtonian physics torque is called "torque" while in static mechanics they call it "moment"?
I prefer by far the term "torque", for not only it sounds strong, but also ...
2
votes
3answers
447 views
If an atom is fully ionized by removing all electrons, is it still an atom?
This is a question about terminology. To me, it's clear that the nucleus of an atom is still an atom. But a comment by Willie Wong at Is nature symmetric between particles and antiparticles? raises ...
2
votes
1answer
83 views
Why is it called “annihilation”?
The term "annihilate" literally means "turn into nothing". However, when a particle and antiparticle collide, they clearly do not turn into nothing; they simply transform into different particles.
...
2
votes
2answers
104 views
May molecules of ideal gases have an inner structure?
The following question is probably very elementary:
whether molecules of ideal gases may have optic properties?
As far as I understand, when one discusses optic properties, one assumes that molecules ...
2
votes
2answers
78 views
Terminology for opposite null lines
Is there a name for two null lines that lie on the opposite sides of the null cone? Each line can be obtained from the other by reflection in the axis of the null cone (the time-axis). In terms of ...
2
votes
1answer
171 views
Why are the quarks so named?
Quarks have a variety of names (or flavours):
Up
Down
Strange
Charm
Bottom or Beauty
Top or Truth
Why do they have such odd names?
2
votes
3answers
412 views
what is it called: box potential with one infinite wall
The finite square well and the infinite square well problem are well known, however is there a reason that there is almost no reference to the one sided infinite square well?
Consider a particle ...
2
votes
4answers
896 views
What is a correct and simple definition of quantum physics?
Is it correct to define Quantum Physics as the study of Physics in sub-atomic scale? Does Quantum Physics studies something else other than sub-atomic phenomena?
This may be a very stupid question ...
2
votes
2answers
125 views
Curved space or curved spacetime?
As I understand it, you can have time + flat space = curved spacetime.
So, when one is trying to emphasise that there is a curvature to the space, is it more technically correct to say curved space ...
2
votes
3answers
911 views
What is the difference between Raman scattering and fluorescence?
What is the difference between Raman scattering and fluorescence?
Both phenomena involve the emission of photons shifted in frequency relative to the incident light, because of some energetic ...
2
votes
2answers
3k views
Are all metals good conductor of electricity?
I am writing an article for kids, which is on conductors and insulators of electricity.
If I make a statement that "All metals are electrical conductors and all non-metals are electrical insulators" ...
2
votes
2answers
252 views
What does physics study?
Wikipedia definition: Physics (from Ancient Greek: φύσις physis "nature") is a natural science that involves the study of matter[1] and its motion through spacetime, along with related concepts such ...
2
votes
1answer
975 views
What is “Quantum Levitation”?
I just found this video Controlled Quantum Levitation on a WipeOut Track
and I'm having a hard time finding the term "Quantum Levitation" used except in reference to the video.
What is the proper ...
2
votes
1answer
98 views
Moose Models (Purpose, Examples)
A problem set for my QFT class is titled "Moose Models" and deals with the moose model for a gauge symmetry of $U(1)\times U(1)$. I was wondering if I could get an explanation of what a Moose Model ...
2
votes
3answers
177 views
Weightlessness by a parabolic flight
Do you actually achieve weightlessness during a parabolic flight? Because I believe I heard somewhere did you achieve 'near-weightlessness' and not 'weightlessness' (if this is true, why is this?) ...
2
votes
2answers
204 views
Should the term Watt's Law be used?
I'm revising some electrical curriculum for a technical training program. In the curriculum students have to calculate values using Ohm's law and the equation Power = Current * Voltage (or P = IV).
...
2
votes
2answers
304 views
Where do the terms microcanonical, canonical and grand canonical (ensemble) come from?
Where do the terms microcanonical, canonical and grand canonical (ensemble) come from?
When were they coined and by whom? Is there any reason for the names or are they historical accidents?
2
votes
1answer
413 views
In layman's terms, what is a quantum fluctuation?
What causes it and how does it occur? If you do post some mathematics, please explain what each term means too please.
2
votes
2answers
359 views
What is the difference between parallel universe and multiverse?
What is the difference between parallel universe and multiverse? Is it parallel universe or universes?
2
votes
1answer
135 views
What is the origin of the naming convention for position functions?
In physics, position as a function of time is generally called d(t) or s(t). Using "d" is pretty intuitive, however I haven't ...
2
votes
1answer
233 views
How does one pronounce this particle's name?
How would you read the following particles' names in a conversation in English? I am looking for some "proper" way of doing it. Say, imagine you are reading a technical description in a semi-formal ...
2
votes
3answers
273 views
Definition of Fluctuations and Perturbations
The terms fluctuations and perturbations are frequently used in physics with different meanings. But they are confusing. Both terms seems to be same. Is there any one who can explain lucidly these ...
2
votes
1answer
177 views
Why is a gaussian fixed point called gaussian?
I know what a gaussian fixed point is, and I did read the wikipedia entry, but it wasn't helpful. It says because the probability distribution is gaussian, but what probability distribution?
2
votes
1answer
180 views
What is deep Fresnel region?
If I understand correctly, it has something to do with autocorrelation function, but can someone give me a definition or exact explanation?
In case of scattering, if you wish to analyze pattern with ...
2
votes
1answer
110 views
What does “single inclusive” mean exactly?
I thought I knew what single inclusive scattering was, but today when I went to look up a definition to check my memory, I couldn't find one. A Google search yielded no shortage of papers that use the ...
2
votes
1answer
49 views
Is symplectic form in Hamiltonian mechanics a physical quantity?
Is symplectic form $dp_i \wedge dq_i$ in Hamiltonian mechanics a physical quantity? It feels to me to be something different than say energy, momentum or mass. Like just certain structure.
The real ...
2
votes
1answer
72 views
Is shear elasticity the same as shear modulus?
I've encountered both the terms "shear elasticity" and "shear modulus". Are these the same?
2
votes
2answers
98 views
SI units with more than one prefix in fractions
Is it (in the view of SI) correct to note units with more then one prefix? I discuss this since several months with friends, but we could not find a proper source for our statements yet.
Examples for ...
