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

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2answers
672 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 ...
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3answers
9k 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 ...
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2answers
360 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 ...
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3answers
343 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: ...
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1answer
39 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? ...
0
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1answer
159 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 ...
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0answers
78 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 ...
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1answer
52 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
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1answer
100 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 ...
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0answers
49 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?
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1answer
46 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
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1answer
118 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. ...
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1answer
2k 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 ...
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0answers
444 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
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2answers
88 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, ...
2
votes
2answers
7k 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
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1answer
165 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 ...
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0answers
60 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
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5answers
104 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 ...
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5answers
3k 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
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1answer
140 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
102 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?
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0answers
347 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?
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2answers
765 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
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1answer
70 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 ...
0
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1answer
134 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?
2
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0answers
51 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
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2answers
192 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 ...
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2answers
250 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? ...
4
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3answers
858 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
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2answers
200 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 ...
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2answers
290 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 ...
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7answers
3k 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 ...
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3answers
20k 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 ...
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1answer
360 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 ...
18
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3answers
893 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 ...
2
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1answer
148 views

Is shear elasticity the same as shear modulus?

I've encountered both the terms "shear elasticity" and "shear modulus". Are these the same?
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1answer
63 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.
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4answers
377 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?
0
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2answers
229 views

Why equivalence principle is principle and not law?

We can prove that the inertial mass and the gravitational mass should be the same (equivalence principle) from the $f=mg=ma$ then $g=a$, so we have equivalence law! But why we said equivalence ...
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1answer
3k views

Differentiating Propagator, Greens function, Correlation function, etc

For the following quantities respectively, could someone write down the common definitions, their meaning, the field of study in which one would typically find these under their actual name, and most ...
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3answers
91 views

Do days and months on the Moon have names?

On Earth we have various calendars, for example, Days: Monday, Tuesday, Wednesday, etc., etc. Months: January, February, March Does the Moon have names for its "daily" rotations, etc.? It sounds ...
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2answers
167 views

What is a “Trojan Moon”?

Today I read an article about Saturn's moon Helene, and it was described as a "Trojan Moon" but no further explanation was given. It was difficult to even get any context about the term from the ...
2
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2answers
101 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 ...
9
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4answers
292 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 ...
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2answers
1k views

What is Curie-Weiss temperature?

What is Curie-Weiss temperature? What is the difference between Curie-Weiss temperature and Curie temperature?
3
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1answer
123 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 ...
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8answers
1k views

What is the name of the principle saying it is meaningless to talk/ask questions that can not be measured/tested?

Watching quantum mechanics lectures and it was mentioned that it is pointless/meaningless to try to talk/question things that can not be tested/measured. Is this a principle? And if so what is it's ...
2
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2answers
153 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 ...
4
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2answers
918 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: ...