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

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1answer
497 views

What's the common consensus on the meaning of “physical change”?

I'm doing a textbook problem that shows a "molecular level" view of some matter, little colored balls, before and after, and there are, among the four questions, two that say: 1) Did a physical change ...
2
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3answers
8k 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 ...
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2answers
189 views

Is an electric lamp a transducer? [closed]

Silly thought. A transducer, by definition, is a device that converts variations in one form of energy to another. An electric lamp converts electricity into visible light - the brightness may vary ...
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1answer
361 views

What is the reference spectrum?

What is the reference spectrum? I need to know how to calculate the reference spectrum of a wavelength 500nm.
0
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1answer
385 views

What is the pause called at the apex of an object's trajectory?

My apologies for such a basic question--I am a musician, not a physicist. But I cannot anywhere find the word, if one exists, that describes that elegant pause of an object such as a ball, thrown ...
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3answers
2k views

What does the dual of a tensor mean (e.g. dual stress tensor in relativistic ED)?

I know what the dual of a vector means (as a map to its field), and I am also aware of of the definition a dual of a tensor as, $$F^{*ij} = \frac{1}{2} \epsilon^{ijkl} F_{kl}\tag{1}$$ I just don't ...
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3answers
731 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?
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1answer
1k 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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2answers
1k 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 ...
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1answer
143 views

Theorem or Conjecture? [closed]

I understand the definitions "theorem" and "conjecture" in mathematics, but I wasn't sure for physics. I mean, if it's proved mathematically, it's a theorem, otherwise it's a conjecture. But for ...
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1answer
304 views

What do I call the inverse of a propagator?

Let's suppose I have a theory described by a Lagrangian as follows: $ \mathcal{L} = A_\mu \underbrace{\left( \partial^2 g^{\mu\nu} - \partial^\mu \partial^\nu + m^2 g^{\mu \nu} \right)}_{K^{\mu \nu}} ...
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2answers
2k 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?
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2answers
2k views

Definitions: 'locality' vs 'causality'

I'm having trouble unambiguously interpreting many answers here due to the fact that the terms locality and causality are sometimes used interchangeably, while other times seem to mean very different ...
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3answers
290 views

What is “A” in AGeV?

AGeV means GeV per nucleon. But why A letter is used for such a short cut? Why not NGeV, for example?
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2answers
2k views

What is Dalitz decay?

What is Dalitz decay? I know there are Dalitz $\pi^0 \to e^+ + e^- + \gamma$ decay, $w \to \pi^0 + e^+ + e^-$ decay, may be more. But is there a rule to say which decay is Dalitz and which is not? ...
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1answer
1k 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
268 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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2answers
645 views

A basic confusion about what is an atom

Wikipedia defines atom as The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. and defines electron as: The ...
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0answers
719 views

What is the relationship between Luminosity, Intensity, and Flux?

I am always confused by the terminology: In high energy particle scattering, and in particular, in the context of collider physics, what is the relationship between luminosity, intensity and flux? ...
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2answers
2k 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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1answer
1k views

What's the relation between perturbative and nonperturbative QFT?

In case of any miscommunication let me describe my understanding of the meaning of "perturbative" and "non-perturbative", and correct me if something is wrong: In a perturbatively defined QFT the ...
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2answers
468 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). ...
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3answers
602 views

Probability vs. degree of belief in facts of nature (“Plausibility”)

I just came across a line in a paper: "Assume the probability that a Lagrangian parameter lies between $a$ and $a + da$ is $dP(a) = $ [...]." This reminded me again of my single biggest qualm I have ...
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2answers
138 views

What should I call an n>4 dimensional Minkowski metric?

I am manipulating an $nxn$ metric where $n$ is often $> 4$, depending on the model. The $00$ component is always tau*constant, as in the Minkowski metric, but the signs on all components might be ...
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1answer
296 views

What does anthropic mean as in Anthropic principle? [closed]

I'm reading a book about string theory, and it describes anthropic principle. Idea is clear to me, I understand this principle describes certain constants in modern physics that are so fine tuned as ...
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2answers
668 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?
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2answers
792 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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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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0answers
672 views

de Sitter and anti de Sitter metric

Is the following correct for the distance $d$ from the origin $(0,0)$ to point $(t,x)$ in the 2-dimensional de-Sitter and anti de-Sitter spaces? Here, $t$ is time and the distance may be called the ...
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2answers
157 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 ...
6
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0answers
216 views

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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5answers
22k views

What's the difference between Fermi Energy and Fermi Level?

I'm a bit confused about the difference between these two concepts. According to Wikipedia the Fermi energy and Fermi level are closely related concepts. From my understanding, the Fermi energy is the ...
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4answers
248 views

Isotropy and Noise

If you have a field which value is just Gaussian noise plus a constant do you call it isotropic? there is no preferred direction however it is not "the same" in all directions if "the same" means ...
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1answer
551 views

Name of the process that causes ice to melt under pressure and refreeze after

I remember a physics experiment from school where a wire with weights on each end was placed over a block of ice. The pressure of the wire caused the ice to melt underneath and refreeze once the ...
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3answers
694 views

What does “nearly infinite mass” mean?

I am sure this is a silly question, but I was reading something that described the pre big-bang universe as having "nearly infinite mass." How can something be "nearly" infinite? The term seems to ...
1
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1answer
642 views

What is the difference between observer, frame of reference, and gauge?

It seems to me that there is considerable relationship between the three concepts: frame of reference, observer, and gauge. How do they overlap? My current understanding is that an observer with a ...
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0answers
289 views

Gauge invariant but not gauge covariant regularization

I'm not sure if someone's already asked this before, but I was wondering, in field theory, when we say that a certain field is gauge invariant but not gauge covariant, what does this mean? In ...
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2answers
1k views

What is “code” in “toric code”?

When I first heard people talking about using Kitaev's toric code to do topological quantum computation, I was thinking how many lines does the toric code have. Then I was told that the "code" really ...
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3answers
274 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 ...
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1answer
324 views

Spectroscopic notation $s$, $p$, $d$, $f$, $\ldots$

$s$ is sharp, $p$ for principal, $d$ for diffuse, $f$ for fundamental. Where do all those term come from? I do not see any link with the corresponding shapes.
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1answer
283 views

Is a uniformly charged conducting plate the same as a uniformly charged conducting sheet?

Is it correct that a uniformly charged conducting plate is made up of two charged conducting sheets, that is, a charged conducting plate consists of four surfaces?
5
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2answers
133 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 ...
1
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1answer
321 views

What is the difference between quantum cryptography and quantum teleportation?

Generate two entangled photons, send one to a message sender and the other to the intended receiver. Both the sender and the receiver recover the same piece of quantum information from the photons, ...
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0answers
62 views

Taylor approximation of e(v) [closed]

Relativistic mass $\displaystyle m(v)=\frac{m_o}{\sqrt{(1-(v/c)^2}}$ $m_o$ = mass of object measured at rest $c$ = speed of light ($3\times 10^8\;m/s$) $v$ = speed If the total relativistic energy ...
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3answers
17k 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
29k views

What exactly is the difference between advection and convection?

After reading Wikipedia articles on advection and convection, I still cannot determine whether there is a consensus on a difference between these two terms. Sometimes, the term convection seems to ...
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2answers
447 views

When to use $f$ and when $\nu$ signifying frequency?

When to use $f$ and when $\nu$ signifying frequency? I guess that when you mean frequency of electromagnetic wave, you use $\nu$, and $f$ otherwise?
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2answers
2k 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 ...
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1answer
699 views

Wave packets v.s. wave trains

Could someone please explain the difference between a wave packet and a wave train? I have rummaged around online but have not been able to find a definitive definition.
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4answers
4k views

Are quantum mechanics and quantum physics the same field?

What is the difference between quantum mechanics and quantum physics?