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

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Basic question concerning pure energy

Inside the core of a star thermonuclear fusion reaction fuses hydrogen atom into helium releasing massive heat/light and energy.When a blackhole eats up enough stars and gases it devours itself by ...
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1answer
47 views

What does 'channel' mean?

I see many plots like the following that graph counts per channel, I know what a 'count' is, but I don't know what a 'channel' is. Could somebody please explain to me? My guess is that it is that ...
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1answer
73 views

Is there a scientific term for star formation?

It might be my stupidity to think that many laymen terms that most people use to describe some physics phenomena usually have a scientifically accepted term or name? The process of star formation, ...
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2answers
119 views

Covariant derivative applied to a vector vs. applied to a matrix?

I know there are (say) two different definitions/representations of the covariant derivative: one is the covariant derivative applied to a vector $F$, which reads as $$DF=\partial F+iAF$$ ...
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2answers
67 views

The word 'sector' in Particle Physics

What exactly is meant when one uses the word sector in Particle Physics? As in, the Hidden Sector or the Electroweak Sector. Does it refer to a specific part of the Lagrangian? Or does it refer to ...
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2answers
78 views

How is the set of displacement operators best called?

Displacement operators $\hat D(x,p), \ \ x,p\in\mathbb{R},$ follow a composition rule $$D(x,p) D(x',p') = \exp\frac{i(px'-xp')}2 D(x+x',p+p').$$ Because of the extraneous phase factor, the set of all ...
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1answer
634 views

What is a bilateral constraint?

In the realm of mechanics/rigid body dynamics, can anyone tell me what a bilateral constraint is? Can't seem to find any information on the exact definition, just uses of it such as "considering only ...
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4answers
3k views

Catapult vs. Trebuchet

I have been looking at trebuchet designs lately, and I have noticed that most, if not all, have a sling attached to them. Without such a sling, the machine would be a catapult. In terms of the speed ...
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2answers
70 views

What does “sites” mean in the lattice language?

I acknowledge that this question is quite trivial. But in the lattice jargon, what does a $N$-sites lattice mean? it's a lattice $N\times N$ or it's a lattice with $N$ vertices? another option ...
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1answer
230 views

Does effective theory have the same meaning in particle and condensed matter physics

I have a naive question about the meaning of effective theory in particle physics and condensed matter physics. In particle physics, from what I know, the effective theory comes from the Wilsonian ...
3
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1answer
214 views

What's a pseudo-rotation?

I'm sorry for this lexical, probably extremely elementary, question. But what is a pseudo-rotation? I just read this term for the first time, in the beginning of the 4th chapter book of CFT by Di ...
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3answers
298 views

Is it time or duration? [closed]

Taking this post: "Is there a proof of existence of time?", as a starting point. Therein was mentioned that there is confusion between: "time" and "flow of time". There was a comment (of mine) that ...
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1answer
108 views

Is there a technical term for “meaningfulness” of mathematical operations?

Is there a technical term for "meaningfulness" of mathematical operations? For example, adding vectors that represent forces has a meaning regardless of the coordinate frame, but an elementwise ...
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2answers
165 views

Quantum Philosophy a la John Bell

I recently discovered this website http://www.quantumphil.org/ and wondering whether Quantum Philosophy is an actual field, or just an aspect of QM? Apologies if this is in the wrong place.
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1answer
83 views

What is the space between galactic arms called?

Is there a term referring to space that is inside the plane of a galaxy, but not part of the center/bar/arms/spurs, etc? What's the filler called? The space between two spiral arms (if it isn't a ...
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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
157 views

What does “single inclusive” mean exactly?

I thought I knew what single inclusive scattering was, but today when I went to look up a definition to check my memory, I couldn't find one. A Google search yielded no shortage of papers that use the ...
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1answer
42 views

What is the difference between a magnon and a spinon?

For a long time, I thought the terms "magnon" and "spinon" were equivalent, describing the collective spin excitation in a system. Lately, I have seen remarks in the literature that they indeed do ...
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2answers
116 views

Is internal symmetry the same as gauge symmetry?

This is more a terminology question. I have seen that some people differentiate between the two types of symmetry: internal symmetry and gauge symmetry (of a field theory). Is there a difference (in ...
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1answer
103 views

Supersymmetry definition

Can someone outline the difference between supersymmetry and supersymmetric quantum mechanics? I often hear the two used interchangeably but I'm almost certain they are not the same.
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1answer
128 views

What is meant by Proton Structure Function?

I am going to embark on a project involving deep-inelastic scattering but first I am trying to do some really basic background reading to get me up to task. My only background in particle physics is ...
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1answer
75 views

Hot Big Bang vs. Big Bang

This should hopefully be a quick one. Is there any difference between the Big Bang Theory and the Hot Big Bang Theory? Around Cambridge I hear everyone using "Hot Big Bang Theory", for example ther ...
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1answer
135 views

How to determine the order of indications of a clock?

Given the description of a clock $\mathcal A$, as (1) a set $A$ of all (more than 2) distinct indications of this clock, in no particular order (where the individual indications contained in set ...
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1answer
119 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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3answers
581 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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1answer
599 views

What are Low-lying energy levels?

I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
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1answer
55 views

Is Kinetic Theory part of Statistical Mechanics?

Some years ago from now I've seem some basic details about what was then called "kinetic theory of gases" where the study of property of gases was made by statistical considerations about the momentum ...
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How can we count 17 particles in the standard model

This may be a bit of numerology, but I'd like to be able to make a statement like "There are 17 particles in the standard model" with some logical definition of a particle. But this statement is ...
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2answers
109 views

Rigorous distinction between quasiparticles and collective excitations

I would like to hear your opinion on the question whether there is an accepted distinction between both concepts in condensed matter physics. I would tend to use the word quasiparticle for dressed ...
3
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1answer
63 views

Off-diagonal terms of the Husimi $Q$ function?

The Husimi $Q$ function of a quantum state $\rho $ is defined as $ Q (\alpha)=\langle \alpha \vert \rho \vert \alpha \rangle $, where $\alpha = (x, p) $ is a phase space coordinate and $\vert \alpha ...
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0answers
84 views

What does the term 'a uniform RVB spin-liquid state' mean?

I encountered this term a uniform RVB spin-liquid state in some articles, for example, see the paragraph under Eq.(29) on page 9 in this paper. What does the word 'uniform ' mean? Simply from the ...
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0answers
621 views

Difference between inorganic and organic semiconductors: electronic structure or configuration, or?

Organic semiconductors differ from inorganic semiconductors. In organic semiconductors the molecules are held together by weak van der Waals interactions and in inorganic semiconductors by covalent ...
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1answer
678 views

What's a better phrase than “speed of light” for the universal spacetime speed constant? [closed]

The phrase "speed of light" is commonly used for the constant c =3E8 m/s, a feature that's "hardcoded" into the structure of spacetime. All massless waves and particles move at this speed, and it's a ...
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4answers
846 views

What is the Difference between a Lepton and a Fermion?

As the Title Says: I am Wondering what the Difference between a Lepton and A Fermion is. I know they both have an ½ integer spin number e.g. a electron, an atom with an odd mass number such as ...
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4answers
433 views

What is the correct term to describe matter converting into energy?

Matter and energy are related; one can convert into the other. What is it called when this happens? For example, solids melt/liquefy into liquid, and liquid vaporizes into gas. Gas condenses into ...
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1answer
265 views

At CERN - What do you call the moment (event) particles crash together in the particle accelerator? [closed]

At CERN - What do you call the moment (event) particles crash together in the particle accelerator? At CERN they crash different particles together and measure what comes out. What is the name of the ...
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5answers
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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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2answers
242 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. ...
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4answers
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Newton's first law: is his concept of (force of ) inertia still useful and used?

The force of inertia is the property common to all bodies that remain in their state, either at rest or in motion, unless some external cause is introduced to make them alter this state. That ...
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1answer
123 views

How to pronounce $\textrm{eV}\!/c^2$

It seems that $\textrm{eV}\!/c^2$ (and its multiples) is commonly used as the unit of mass in particle physics. For example, David Griffiths uses it quite naturally in Introduction to Elementary ...
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271 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
990 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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3answers
863 views

Opposite of Cryogenics

Cryogenics is related to very low temperatures, so, what is the term when referring to very high temperatures?
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64 views

What unit system does Fahrenheit belong to?

Wikipedia's page for Imperial Units does not list Fahrenheit. The corresponding page for SI Units lists Kelvin as an SI unit, and Celcius as a derived SI unit. This leads me to believe that ...
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2answers
159 views

What's the symbol for the antiparticle of the delta plus baryon?

It can't be $\Delta^-$ since that is another particle also made up of quarks (not antiquarks). I can think of four possibilities: $\overline\Delta^+$ $\overline{\Delta^+}$ $\overline\Delta^-$ ...
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3answers
217 views

What is the work done against a force?

Suppose a particle travels a path $\gamma : I\subset \mathbb{R}\to \mathbb{R}^3$ subject to a force $\mathbf{F}: \mathbb{R}^3\to T\mathbb{R}^3$, then we know that we define the work done by the force ...
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2answers
153 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 ...
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903 views

what is it called: box potential with one infinite wall

The finite square well and the infinite square well problem are well known, however is there a reason that there is almost no reference to the one sided infinite square well? Consider a particle ...
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3answers
78 views

Is wave superposition always equivalent to wave interference?

I'm confused when using these 2 words "wave superposition" and "wave interference" since their definition is very similar. So, are these 2 term the same?
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1answer
278 views

Difference in “momentum” names in Lagrangian mechanics

In the context of Lagrangian formulation of classical mechanics, the following names keep occurring in most textbooks, which confuse me a lot, are they different in any way? Momentum Generalized ...