Use this for questions relating to the proper use of physics terminology or nomenclature.
3
votes
2answers
99 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 ...
-1
votes
0answers
48 views
What is the difference between various fields of physics? [closed]
what is the difference between the fields of physics? like high energy physics, particle physics, cosmology, quantum physics, quantum mechanics, experimental physics, theoretical physics, applied ...
-1
votes
1answer
81 views
Is the speed of light related to the mass of the universe?
If the mass of the universe were cut in half, would it affect the speed of light?
Would it be twice as fast?
Would it stay the same?
Do we have instruments that are sensitive enough to measure the ...
1
vote
1answer
34 views
What is $\gamma$ in the damping equation?
$x''+\gamma x'+w_0^2x=0$
That is the general equation for damped harmonic motion. What is the term or name that describes $\gamma$?
Is it called the damping constant? I know its the ration between ...
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 ...
0
votes
0answers
42 views
What is to be considered a “body” in physics?
Well, the question says it all; is there a definition of body in physics? What is to be considered a physical object and what it cannot?
-1
votes
0answers
36 views
What is meant by cellular in the context of “cellular water”? [closed]
Paraphrased from Wikipedia:
Infrared sensing in snakes depends on a kind of natural thermography, by which tiny packets of cellular water are raised in temperature by the infrared radiation.
...
1
vote
1answer
43 views
What are “packets”?
Paraphrased from Wikipedia:
Infrared sensing in snakes depends on a kind of natural thermography, by which tiny packets of cellular water are raised in temperature by the infrared radiation.
...
1
vote
1answer
32 views
Name of a state with $d-1$ excitations, distributed uniformly among $n$ qudits
Is there a particular name for a quantum state of the form (up to the normalization):
$$\sum_{i_1+\ldots+i_n = d-1} |i_1\rangle |i_2\rangle \ldots |i_n\rangle$$
or was it studied is some papers?
...
10
votes
3answers
220 views
The notion of an adiabatic process in thermodynamics -vs- quantum mechanics
I'm confused about the terminology in the two contexts since I can't figure out if they have a similar motivation. Afaik, the definitions state that quantum processes should be very slow to be called ...
4
votes
1answer
92 views
What is the difference between Radiation and Electromagnetic Radiation
Are the two equivalent or is Electromagnetic Radiation a subset of Radiation. I am further confused by the fact that electromagnetic radiation includes both ionizing and non ionizing types of ...
0
votes
1answer
51 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 ...
1
vote
2answers
154 views
What postulate means in physics?
What does postulate mean in physics? What is their role in physical theories?
Is it possible to break physical postulates?
0
votes
1answer
83 views
What is a long-tailed distribution for physicists?
What is the most common definition of long tailed distribution for physicists? I am looking for definition and examples. Examples should have arguments why the distribution is or is not long tailed.
...
0
votes
2answers
49 views
What is “species” in the context of an electrochemical cell?
From the Wikipedia entry on Electrochemical cell (http://en.wikipedia.org/wiki/Electrochemical_cell):
An electrochemical cell consists of two half-cells. Each half-cell
consists of an electrode, ...
3
votes
0answers
102 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 ...
1
vote
0answers
45 views
Trying to speak correctly of spacetime intervals and how to compare them
Is it correct to speak of "magnitude of a spacetime interval"?
For instance, considering a pair of (distinct) events, $A$ and $B$, which are lightlike separated, is it correct to say that "the ...
2
votes
1answer
94 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 ...
1
vote
5answers
88 views
Is there a more scientific term for “obstruction of EM waves”?
When EM waves pass through things like rain and hail, they can be "obstructed" and bounced back or absorbed, rather than passing through.
I'm conducting an experiment on this effect, and wondered if ...
5
votes
5answers
478 views
Difference between theoretical physics and mathematical physics?
I'm a huge fan of mathematical physics and I know what the formal definitions of those two areas are, I've seen them. But I still get completely baffled when someone asks me to explain it simply. The ...
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.
...
7
votes
2answers
236 views
Should it be obvious that independent quantum states are composed by taking the tensor product?
My text introduces multi-quibt quantum states with the example of a state that can be "factored" into two (non-entangled) substates. It then goes on to suggest that it should be obvious1 that the ...
0
votes
1answer
77 views
Oscillon and soliton
I want to know the major difference between oscillon and soliton in terms of radiating energy with respect to time and position. And what about their localization?
0
votes
0answers
188 views
How is the term “Born level” usually defined?
How is the term "Born level" usually defined, e.g. in talking about the $pp\to Z/\gamma^*\to e^+e^-$ cross section at Born level?
4
votes
2answers
320 views
Amplitude of Probability amplitude. Which one is it?
QM begins with a Born's rule which states that probability $P$ is equal to a modulus square of probability amplitude $\psi$:
$$P = \left|\psi\right|^2.$$
If I write down a wave function like this ...
0
votes
1answer
96 views
What's the difference between these two formulas and how are these called?
I just want to know the differences between these two formulas:
$h = h_0 + v_0 t ± \frac{1}{2} g t^2$
and
$y = y_0 + v_{0y} t + \frac{1}{2} g t^2$
Also, how are these called in English?
0
votes
0answers
213 views
What is the correct definition of “group velocity dispersion”?
When we talk about a medium with dispersion, we can define the phase velocity $v_\phi = \omega/k$ and the group velocity $v_g = d\omega/dk$. Likewise the phase index $n = c/v_\phi$ and the group index ...
1
vote
0answers
65 views
Motivation For Definitions [closed]
I noticed in my physics textbook that we define certain relationships to be true. I can see how this is considerably helpful in deriving other relationships from these definitions; for instance, take ...
1
vote
0answers
41 views
What name would you give to the method of approximating an arbitrary magnet with many smaller dipoles?
Let's say I had an arbitrarily shaped permanent magnet, with total magnetic moment $M_{0}$. Ways to calculate the magnetic field of this magnet include an analytic solution (if one exists), as well ...
2
votes
2answers
105 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?
9
votes
2answers
230 views
Word for the star around which an exoplanet orbits:
Is there accepted nomenclature for the star around which a particular exoplanet orbits? Meaning, if I were to say "The exoplanet blah blah blah's (noun)" what noun would I put there? Sun? Star? ...
2
votes
2answers
123 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 ...
0
votes
2answers
166 views
Are probability-preserving variations of QT with respect to the Born rule mathematically possible?
Is it possible to create (m)any theoretically workable framework(s) - that do(es) produce probabilities - by taking QM and replacing the Born(-like) rule(s) with something that is not equivalent to it ...
0
votes
0answers
33 views
Term for “atmospheric ricochet” due to wrong “angle-of-attack”
I watched "Apollo 13" yesterday, and they had the "angle-of-attack" problem that had to be manually solved, to prevent the ship from "ricochet[ing] off the atmosphere like a rock skipping off a pond".
...
4
votes
4answers
150 views
What is the term for hose fluctuating movements during flow?
What do we call it when water flowing through a flexible hose causes it to act like snake movements if the hose were disturbed?
Can this movement be explained by the Coriolis force?
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 ...
8
votes
4answers
231 views
What makes an equation an 'equation of motion'?
Every now and then, I find myself reading papers/text talking about how this equation is a constraint but that equation is an equation of motion which satisfies this constraint.
For example, in the ...
2
votes
1answer
71 views
Is shear elasticity the same as shear modulus?
I've encountered both the terms "shear elasticity" and "shear modulus". Are these the same?
0
votes
2answers
222 views
What is Curie-Weiss temperature?
What is Curie-Weiss temperature? What is the difference between Curie-Weiss temperature and Curie temperature?
6
votes
1answer
275 views
Is Pauli-repulsion a “force” that is completely separate from the 4 fundamental forces?
You can have two electrons that experience each other's force by the exchange of photons (i.e. the electromagnetic force). Yet if you compress them really strongly, the electromagnetic interaction ...
3
votes
3answers
116 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).
...
0
votes
2answers
214 views
Are the intersections of past and future light cones spacelike?
Given a timelike reference worldline (not necessarily geodesic), we can define light-cone coordinates $\tau^+$ and $\tau^-$ so that the 3-D hypersurfaces of constant $\tau^+$ are past light cones of ...
2
votes
2answers
96 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 ...
0
votes
1answer
52 views
Reason for the convention about polarization states
I'd like to know if there is a special reason for limiting convention of polarization state to waves that can be split in just two components of equal frequency.
1
vote
3answers
243 views
Long/short-range interaction
A potential of the form $r^{-n}$ is often considered long-range, while one that decays exponentially is considered short-range.
Is this characterization simply relative/conventional, or is there a ...
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 ...
2
votes
1answer
65 views
What is the name for the whistling “musical” sounds that change stepwise in pitch when a hollow tube is spun like a lasso?
You have likely heard those sounds, science museums sometimes sell Flexible plastic tubes you can whirl like a lasso. The air rushing by the end of the tube causes these sounds, which are admitted in ...
2
votes
3answers
176 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?) ...
0
votes
3answers
142 views
Is it true that an isolated fundamental particle does not decay?
Is it true that an isolated fundamental/elementary particle does not decay?
It seems logical to me.
