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

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2
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2answers
225 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: $\overline\Delta^+$ $\overline{\Delta^+}$ $\overline\Delta^-$ ...
2
votes
2answers
81 views

Meaning of SIS in accelerators

With reference to accelerator facilities, the term "SIS" is often used. e.g. SIS-100, SIS-300 etc. What does SIS stand for, in this context? (The last S is probably for Synchrotron) Google appears ...
1
vote
1answer
128 views

How does Dirac form this conjugate imaginary equation?

On page 30 of Dirac's book $$\xi|P\rangle = a|P\rangle\tag{12}$$ He then says Suppose we have a solution of (12) and we form the conjugate imaginary equation, which will read $$\langle ...
0
votes
1answer
70 views

Friedmann equations question

Friedmann equations for critical density is: $$\rho_c = \frac{3H^2}{8\pi G}$$ Is there any other way to write this equation? For example: $$\rho_c = \frac{3}{8\pi GH^2}$$ I saw the above form on ...
1
vote
1answer
286 views

Buoyancy / Drag Problem

Buoyancy / Drag Problem Just a little bit of help would be nice. I have a spherical particle of radius $R$ and density $\rho$, surrounded in a fluid of density $\phi$ and viscosity $\eta$. I'm ...
3
votes
1answer
180 views

Use of the term first order dependency

In a question I am doing it says: Show explicitly that the function $$y(t)=\frac{-gt^2}{2}+\epsilon t(t-1)$$ yields an action that has no first order dependency on $\epsilon$. Also my textbook ...
1
vote
1answer
460 views

Does the Sun “drag the solar system through space”?

In this video: http://www.youtube.com/watch?v=0jHsq36_NTU#t=55 at 0:55, it is claimed that "the sun is [...] dragging the planets in its wake". Is this true? My understanding is that the sun and ...
4
votes
2answers
180 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 ...
1
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0answers
81 views

Why are Lagrangian subspaces called 'Lagrangian'?

I am wondering what the special role of Lagrangian subspaces (or submanifolds) are in mechanics. Do these subspaces have some sort of special property for which we have some sort of `Lagrangian ...
3
votes
4answers
2k views

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 ...
0
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4answers
55 views

Can the term «shadow» pertain to anything else than light? [closed]

Can the term shadow pertain to anything else than light? Feel free to interpret this question in the widest sense possible.
2
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2answers
368 views

Conservation laws and continuity equations

I'm a bit messed up with conservation laws and continuity equations. This is my understanding: A conservation law describes that a physical quantity $G$ is conserved with time. It does not prevent ...
6
votes
1answer
352 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 ...
0
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1answer
60 views

Can Allan variance be generalized such that the “Oscillator model” is not presumed?

The definition of Allan variance, $\sigma^2[ \tau ]$, which relates to "stability of clocks" is described on the Wikipedia page as being derived in terms of an "Oscillator model": "The oscillator ...
19
votes
4answers
945 views

Is the Big Bang defined as before or after Inflation?

Is the Big Bang defined as before or after Inflation? Seems like a simple enough question to answer right? And if just yesterday I were to encounter this, I'd have given a definite answer. But I've ...
3
votes
3answers
503 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 ...
1
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3answers
2k views

Why is density an intensive property?

I am still trying to understand what are intensive and extensive properties. Possibly someone can give a pointer to a decent text (preferably on the web), as I am not too happy (to say the least) with ...
8
votes
5answers
2k views

Is speed an intensive property?

I remember being taught in elementary physics that while it makes sense to add volumes, masses, or heat, it makes no sense to add temperatures. As I wanted to use that to illustate some other issue, ...
2
votes
3answers
924 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 ...
2
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3answers
333 views

Configuration manifolds and constraints

In Classical Mechanics there's this notion of configuration manifold. Although I've heard about that a lot and although I often use that concept, I'm not sure I really understand them well because ...
0
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1answer
443 views

Name of battery voltage when load connected/disconnected

If I had a 3V battery, and when no load connected it reads 3.2V, and with a load 2.8V (just a hypothetical example), what is the name for these two terms, with a load or no load? I know the voltage ...
8
votes
5answers
2k views

Is 'amp' a technically invalid term?

I've been told to use the term ampere in exams and class (I'm in high school), instead of amp as it's not a valid unit, although I've been using the amp for years along with all of my friends who do ...
5
votes
2answers
360 views

Showing that Coulomb and Lorenz Gauges are indeed valid Gauge Transformations?

I'm working my way through Griffith's Introduction to Electrodynamics. In Ch. 10, gauge transformations are introduced. The author shows that, given any magnetic potential $\textbf{A}_0$ and electric ...
4
votes
3answers
800 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 ...
0
votes
1answer
33 views

What are “finely subdivided” substances?

As in the title, what does it mean for a substance to be finely subdivided, or finely grained? For example: It is only in the cases for which the ratio area/volume is very large (for example, a ...
2
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1answer
73 views

Are there more distinctive names of “null curves” with certain additional properties (absence of “chord curves”)?

In this answer (to the question "In general relativity, are light-like curves light-like geodesics?", PSE/q/76170) a particular example of a curve is discussed whose "tangent is everywhere null" and ...
2
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3answers
119 views

In terms of physics, does the phrase “time slows down” mean the same thing as “things happen more slowly?”

The common definition of "time" is a type of measurement, like size. But the sentence "size gets bigger" doesn't make any sense. Is "time slows down" an odd phrasing of "events occur more slowly" or ...
3
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4answers
1k views

Is there a difference between Hertz and 'frames per second'?

It's not uncommon that the term 'frames per second' (sometimes abbreviated as fps or FPS) is associated with, or even equated to, the unit Hertz (Hz). I'm not exactly sure how these two concepts ...
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2answers
522 views

Action and Action integral: Different kinds of variational principles

What are the difference between: the action $\int_{t_{1}}^{t_{2}}(L+H) dt$ that we use in the principle of least action, and the action integral $\int_{t_{1}}^{t_{2}}L dt$ that we use in ...
0
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2answers
64 views

What does the term 'hyperbolic model' mean?

I am reading this non-linear discrete dynamical system paper. The authors mention the term hyperbolic model. What does that mean?
8
votes
3answers
624 views

Is a “shift in the meaning” of Accuracy and Precision occurring?

Accuracy and precision are among the most fundamental concepts in experimental physics, and, I always believed, completely unambiguous. Recently I found that the Wikipedia article on Accuracy and ...
0
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2answers
93 views

Changing from potential to kinetic energy

During a conversation with a friend, I began to wonder if there's is a term for the transformation of potential energy to kinetic energy, and vice versa.Is there a term for the process of converting ...
3
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4answers
95 views

Measurement in reciprocal metres

I'm trying to name a measurement that is measured in reciprocal length, which is in a draft document for vehicle risk management. It currently says: ...
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2answers
209 views

Is fission reaction considered natural or artificial? [closed]

As I learned, nuclear fission doesn't occur without the control of a human made nuclear reactor, by hitting a neutron to a fissile isotope. Thus, the fission reaction is considedred as a part of ...
1
vote
1answer
222 views

The meaning of “heralded photon”

I am not a native English speaker, and I have just started to study physics in English. However, I came across the term heralded photon while I was reading a review article about optical quantum ...
1
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0answers
47 views

Since “coordinate time” has a very specific meaning, how to call more general parametrizations?

Recently I've learned that "coordinate time" assigned to a particular time-like spacetime path is not only required (1) to be monotonous and continuous and even differentiable wrt. the "proper time" ...
3
votes
1answer
112 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.
1
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2answers
2k views

Why is scattering vector $\vec{q}$ called vector of 'momentum transfer'?

In the world of scattering the angle at which you detect the scattered radiation is known as $q$, where $$ \vec{q} = \frac{4\pi\eta}{\lambda}\sin(\theta/2) $$ I read in a lot of books that this is ...
1
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1answer
93 views

Usage of the terms Raman, Stokes and anti-Stokes scattering

I am confused over the correct usage of the terminology for "Raman scattering", "Stokes scattering", "anti-Stokes scattering", or even "Stokes-Raman scattering" and "anti-Stokes-Raman scattering". Is ...
0
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1answer
1k views

Is there a name for a substance that is a gas at room temperature?

Is there a name for a substance that is a gas at room temperature, such as Hydrogen, Helium, Neon, Argon, Krypton, Xenon, Chlorine, Fluorine, Bromine, Nitrogen, and Oxygen. I am writing a paper where ...
2
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0answers
47 views

What does unfolding of attractor mean?

What does unfolding of attractor mean? Effect of time scales on the unfolding of neural attractors paper talks about Takens embedding theorum. It says that the embedding dimension should be large ...
1
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1answer
47 views

Totally antisymetric wavefunction: clarification about terminology

Pauli's Principle says: "The wavefunction of two identical fermions must be totally antisymmetric". I know that, for a antisymmetric wavefunction, $(-1)^L*(-1)^{S+1}*(-1)^{I+1}=-1$ "totally ...
1
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1answer
247 views

Parity of a system composed of 2 particles

I have read that for a system of 2 particles, the total parity is given by: $P=P_1 P_2 (-1)^L$ where $ P_1, P_2$= insisec parity of particle 1, 2 $L$ = relative angular moment what's the meaning ...
7
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2answers
841 views

History of the names “Feynman-gauge” & “Landau-gauge”. How arised & how settled?

Warning: Students, stay away from antiquities. The aim to learn is to survive. Hi. Today the nomenclatures Feynman gauge and Landau gauge seem established, but could you explain the history? It's ...
1
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2answers
64 views

Terminologies for moment of inertia

Perhaps someone can suggest the right terms for the following mathematical objects related to moment of inertia? A inertia tensor $I$. $$I \equiv \begin{bmatrix} I_{1,1} & I_{1,2} & I_{1,3} ...
2
votes
1answer
84 views

What is a 'height field'?

I encountered a few times the expression of 'height fields' in statistical physics, without ever reading a proper definition. My textbooks don't seem to talk about that, and googling it hasn't been ...
5
votes
1answer
62 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
155 views

What is the name for the “nothing particle”? [closed]

What is the name for a particle with zero mass, zero charge, no strong force, no weak force and has no energy?
4
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2answers
99 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 ...
3
votes
2answers
998 views

What is an “Interaction Hamiltonian”

I'm an undergraduate reading up on some quantum physics so that I can help out more in the lab that I'm working in this summer. In the book I'm reading (Shankar's "Principles of Quantum Mechanics") I ...