Use this for questions relating to the proper use of physics terminology or nomenclature.
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2answers
109 views
Magnitude refers to number or number with units?
This question is about terminology for physical quantities.
When we talk about magnitude (while talking about scalars and vectors) do we refer to just number or Number along with units?
example: If ...
0
votes
3answers
2k views
Difference b/w Kinetics & Kinematics w/concrete example
(I know whether I understand this or not doesn't matter much to my work & study but am just curious.)
I still can't differentiate in my head kinetics and kinematics (similar thread is found but ...
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?
7
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2answers
235 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 ...
4
votes
3answers
171 views
What is a “measure equation” as mentioned by this TeX Users Group guide?
In this TeX Users Group (TUG) document, Typesetting mathematics for science and technology according to ISO 31/XI by Claudio Beccari, the author makes various typesetting recommendations including:
...
1
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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?
...
-1
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0answers
46 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
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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
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0answers
64 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 ...
0
votes
1answer
50 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
1answer
33 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 ...
10
votes
3answers
213 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 ...
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
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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
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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
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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.
...
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.
...
4
votes
1answer
87 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 ...
1
vote
0answers
262 views
What is a boundary condition for capacitors/dielectrics?
I am extremely confused about what boundary conditions are. One minute ago I was solving easy capacitor questions and the next minute I am being asked boundary condition questions and there is no such ...
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 ...
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
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
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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 ...
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
475 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.
...
0
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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
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0answers
186 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 ...
5
votes
1answer
57 views
Is there an established standard for naming exoplanets?
I understand that exoplanets are named by adding a lowercase letter to the a designation of the planet's parent star or stellar system, beginning with 'b' (the star itself is 'a') in order of ...
9
votes
4answers
262 views
Is the Lagrangian of a quantum field really a 'functional'?
Weinberg says, page 299, The quantum theory of fields, Vol 1, that
The Lagrangian is, in general, a functional $L[\Psi(t),\dot{\Psi}(t)$], of a set of generic fields $\Psi[x,t]$ and their time ...
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?
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0answers
207 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
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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
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2answers
161 views
What are the differences between indistinguishable and identical?
What is the difference between indistinguishable particles and identical particles?
9
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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? ...
0
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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 ...
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).
...
2
votes
2answers
122 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
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 ...
13
votes
7answers
1k views
What is a general definition of impedance?
Impedance is a concept that shows up in any area of physics concerning waves. In transmission lines, impedance is the ratio of voltage to current. In optics, index of refraction plays a role similar ...
7
votes
3answers
5k views
What exactly is the difference between radiation and convection?
Okay, so everywhere I've read, I hear the main difference is the requirement of a medium. But for example, if you take the case of heat 'radiating' from a red-hot iron, isn't that actually convection ...
3
votes
1answer
216 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 ...
9
votes
3answers
449 views
“Slightly off-shell”?
I'm not new to QFT, yet there are some matters which are quite puzzling to me. I often come across the statement that real particles (the ones we actually measure in experiments, not virtual ones) are ...
0
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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".
...
2
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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
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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.
4
votes
4answers
149 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?
