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

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Physical interpretation: weighted eigenvalues of the Laplacian with a potential

I'm a mathematician with only the basic knowledge of Physics, so my question may be trivial: in this case, mercy me. :-) Let $\Omega \subseteq \mathbb{R}^N$ be a domain and let $V,m:\Omega \to ...
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3answers
2k views

Why is Higgs Boson given the name “The God Particle”?

Higgs Boson (messenger particle of Higgs field) accounts for inertial mass, not gravitational mass. So, how could it account for formation of universe as we know it today? I think, gravity accounts ...
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2answers
7k views

Is time a Scalar or a Vector?

In Wikipedia it's said that time is a scalar quantity. But its hard to understand that how? As stated that we consider only the magnitude of time then its a scalar. But on basis of time we define ...
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3answers
2k views

What sets a “Law” apart from a “Rule” or a “Principle”? [duplicate]

Basically, I understand the difference between a "Theory" and a "Theorem" but I am quite confused when it comes to "Law", "Rule" and "Principle". Can you make the differences clear to me?
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1answer
179 views

Why the speed of light is represented by $c$? [closed]

In almost every textbook, I've found that the speed of light is $c \approx 3 \times 10^8\: \mathrm{m/s}$. I wonder why it's just $c$ ?
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2answers
499 views

What does a non-perturbative theory mean?

I'm a science writer and I'm having difficulty understanding what a non-perturbative approach means. I thought I understood what perturbative meant, but in looking for explanations of ...
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4answers
2k views

Are quantum mechanics and quantum physics the same field?

What is the difference between quantum mechanics and quantum physics?
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2answers
203 views

Nomenclature of hadronic resonances

I have the Particles Physics Booklet and I noticed that the resonances that decay into a nucleon and pion are indicated by an abbreviation. For example $P_{33}$ is associated to the $\Delta (1232)$ ...
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3answers
399 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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4answers
4k 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 ...
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1answer
246 views

Nomenclature of radial solutions to the Schrodinger Equation

For the free particle with quantum number $l=0$, the regular solution to the radial Schrodinger equation is $R_0 (\rho)=\frac{\sin{\rho}}{\rho}$ while the irregular solution is $R_0 ...
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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 ...
5
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1answer
92 views

Why are “quadratures” called this way?

In quantum optics (and hence also cv quantum information), given the annihilation and creation operators of the electromagnetic fields $a$ and $a^{\dagger}$, the "position" and "momentum" operators ...
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1answer
891 views

Is there a difference between a postulate and a principle in physics?

Is there a difference between a postulate and a principle in physics? Both seem unproved statements taken as true. If thats correct, why the different names?
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1answer
56 views

Phase space appellation

Does anyone know why they called the momentum-position space the phase space in the first place? To clarify what I mean a bit more, I'll give you an example: The name configuration space for the ...
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2answers
270 views

What's the difference between “evidence of a new particle” and “discovery of a new particle”?

Today’s exciting press release from Tevatron on the Higgs boson keeps its head cool and say that physicists saw a “hint” of the Higgs boson because the signal is barely above the two-sigma level. In ...
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1answer
944 views

What does the concept of phase space mean in particle physics?

I came across the concept of phase space in statistical mechanics. How does this concept come about in particle physics? Why was it introduced and how is it used? What does it mean when ...
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2answers
121 views

Is the “dimension” in dimensional analysis the same as the “dimension” in “three spatial dimensions”?

When we talk about the dimension of a quantity (e.g. the dimension of acceleration is$[ L \ T ^ {-2}]$) are we talking about the same "dimension" as when we talk about three dimensional space? Are ...
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2answers
7k views

Convective and Diffusive terms in Navier Stokes Equations

My question has 2 parts: I just followed the derivation of Navier Stokes (for Control Volume CFD analysis) and was able to understand most parts. However, the book I use (by Versteeg) does not ...
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2answers
119 views

What is it called when a fluid will “jump” to grab onto an object that comes very close?

I'm doing an experiment where I bring a probe very close to a well full of fluid and then very slowly lower it to obtain some force deformation values. The material behaves very much like a fluid and ...
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1answer
226 views

What is the name of the temperature limit beyond which an explosion will form a mushroom cloud?

Many months ago I saw a picture that was taken many years ago of an explosion, possibly in the Atlanta area. If I recall the explosion was caused by fuel in railroad cars. However, the explosion ...
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1answer
48 views

Vacuums and free space

Do physicists use the terms "vacuum," "quantum vacuum," and "free space" synonymously? For example, I have read that based on conservation arguments, the spontaneous splitting of a photon into an ...
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1answer
70 views

Meaning of the 'deep lattice limit' and 'shallow lattice limit'?

In condensed matter literature, at many places, the phrase 'deep lattice limit' is used. Please tell what is the deep lattice limit and the shallow lattice limit?
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1answer
325 views

“Hard wall”/ “soft wall”

I have encountered those terms in various places. As I understand it, "soft wall" can correspond to a smooth cutoff of some spacetime, while "hard wall" can be a sharp one, which can be described in ...
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2answers
863 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.
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73 views

What does “P-wave” mean when referring to a particle?

In scattering theory, P wave means $l=1$, where $l$ is the azimuthal quantum number. However, what does P wave mean when referring to particle states? For example, in this paper (arXiv link), the ...
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3answers
687 views

Definition of a year

Is there an acceptable definition of a year (in number of days)? Google Calculator: https://www.google.com/search?q=seconds+in+1+year returns 3.15569e7 seconds and then ...
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2answers
317 views

Where does this term “shell” with prefix “on-/off-” come from?

Is there some historical reasons or is there a specific reason behind it? This question is connected to: Why on-shell vs. off-shell matters?
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3answers
266 views

How is a bound state defined in quantum mechanics?

How is a bound state defined in quantum mechanics for states which are not eigenstates of the Hamiltonian i.e. which do not have definite energies? Can a superposition state like ...
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2answers
2k 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
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3answers
562 views

Nomenclature: Yang-Mills theory vs Gauge theory

If you're writing about a theory with Yang-Mills/Gauge fields for an arbitrary reductive gauge group coupled to arbitrary matter fields in some representation, is it best to call it a Yang-Mills ...
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3answers
195 views

Defining left and right independent of a human body?

Is it possible to define right and left independent of the asymmetric human body? I am unable to think of such a definition without circular reasoning. Example: If you are facing east, your left ...
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3answers
350 views

What are the differences between indistinguishable and identical?

What is the difference between indistinguishable particles and identical particles?
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1answer
599 views

What is the difference between the words transparent and translucent?

Merriam Webster defines transparent as: Having the property of transmitting light without appreciable scattering so that bodies lying beyond are seen clearly. And translucent as: ...
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215 views

What is the meaning of “CW” in LASER?

I am reading a user's manual, and the word appears here. At first, I think "CW" means "center wave". But later, I find that the meaning of "CW" is "continuous wave". It makes me confused. ...
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4answers
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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 ...
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4answers
403 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?
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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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1answer
150 views

Which transformations are canonical?

Which transformations are canonical? Why do canonical transformations preserve the measure of integration in phase space?
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3answers
1k 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). ...
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3answers
2k 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" ...
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2answers
79 views

Definition of quantum anharmonicity

I have been reading research papers in mathematical physics for some months now, and I've seen the the term "anharmonic oscillator" quite frequently. At first I assumed that given a Schrodinger ...
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2answers
113 views

Why is it tension in surface tension?

Why is it called surface tension not surface compression?
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1answer
45 views

Why is the specific notation used for term symbols useful?

This has bugged me for a long time. Term symbols describe electronic states of atoms which have well-defined total electronic angular momentum $J$ as well as total spin and orbital angular momenta ...
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1answer
194 views

What do you call the period after sunrise when the sky is bright?

At sunrise, the sky isn't actually up in the sky yet. Twilight occurs before sunrise, then at sunrise the leading part of the sun crosses the horizon. But, the sky isn't bright yet. It takes some time ...
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4answers
1k views

Work done by the Magnetic Force

The magnetic part of the Lorentz force acts perpendicular to the charge's velocity, and consequently does zero work on it. Can we extrapolate this statement to say that such a nature of the force ...
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2answers
590 views

The definition of “frequency” in different contexts

I have been doing some research on all kinds of sound-related topics lately and have been a bit confused by the different uses of the term "frequency". Of course, the most general meaning of frequency ...
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3answers
983 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: ...
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1answer
1k 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 ...
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3answers
5k views

What is a virtual ground?

What is a virtual ground? I would like to know what it is.