Questions tagged [terminology]

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

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What does “channel” mean in the context of QCD?

I am familiar with the common use for "channel" in terms of particle physics (like Mandelstam variables). What confuses me is how it's used in the following paper on QCD: C. A. Dominguez, &...
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4answers
376 views

What is the difference between “field equations” and “equations of motion”?

I come across the terms "equations of motion" and "field equations" all the time, but what is the difference? For example, general relativity is described in terms of the Einstein ...
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Why can the word “fusion” mean either “combining” or “breaking/melting” in different contexts? [migrated]

The word "fusion" is at times confusing because in a way it has two opposite meanings: Combining things together, for example "nuclear fusion". Melting/breaking things, for ...
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“Directionally” translational variance of a function(al)?

Let $f:\mathbb R^3\to\mathbb R$. We define that $f$ is transnational variance if: For any $a\in\mathbb R^3$, $f(x)=f(y) \Leftrightarrow f(x+a)=f(y+a)$. However, if $a$ is limited to be some specific ...
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1answer
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What does “continuous spacetime” mean?

I often encounter discussions, such as seen here, about whether spacetime is discrete or continuous. However, I am only familiar with continuity as being a property of functions. I saw this question ...
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How to convert GeV to AGeV? [duplicate]

The beam energy is sometimes in AGeV in collider papers. I'm stuck on how to convert AGeV to GeV.
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3answers
343 views

Really basic question on Pressure [closed]

I'm reading this book.It says: Doubling the gauge pressure does not double the amount of air in the tank. But doubling the absolute pressure does. I don't understand why...when : $\text{Absolute}\ P= ...
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2answers
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Are uniform acceleration and uniform motion the same? [closed]

Found this question from my textbook. Any answers are appreciated, thanks. :D
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Why are the number of magnetic field lines finite in a particular area?

One can draw/imagine as many unique (curved/straight) lines as he/she wants in some specified finite area (assuming that each line is unique if it doesn't overlap with another line). Then how can the ...
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What is the terminology difference between Hot, Ballistic and Thermal Electrons

In the realm of injection of electrons into a solid what are the difference between hot, ballistic and thermal electrons? Is the injected electron ballistic electron? Are they mutually exclusive terms?...
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1answer
62 views

Difference between Phenomenal and Phenomenological in the Context of Physics

I was going through a conference presentation on System of Systems Engineering. In the presentation entitled "Macroscopic Quantum Mechanics and the SoSE Design Approach", I came across a ...
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1answer
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Name for region in phase space with no outgoing or incoming flows?

I've been looking for a term online but couldnt find it: suppose we have a subset $X$ in phase space, such that for all $q\in X$, the path starting at $q$ never exits $X$ either forward or backward in ...
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What is the name of the shape of the iron core in a transformer?

I'm researching on transformers and curious to know about what this shape is called (the actual core block, ignore the wires around it).
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Is the term “heat transfer” correct?

"Heat" can be defined as: "energy in transfer to or from a thermodynamic system" (From Wikipedia). I have seen other definitions, but they all include the term "transfer"....
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1answer
188 views

Why are symmetries labelled by groups and not representations?

Physicists will say that a certain system has $G$ symmetry, where $G$ is some group, such as $SU(2)$ or $S_3$ or whatever. To show that this is the case, they will conjure up an explicit ...
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1answer
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What do $S$, $M$, and $A$ mean in quark/color theory?

From Wikipedia [...]below, and symmetric in flavor, spin and space put together. With three flavors, the decomposition in flavor is $$ \mathbf{3} \otimes \mathbf{3} \otimes \mathbf{3} =\mathbf{10}_{S}...
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What is the constant in $F=kma$ called?

I understand fully where the constant comes from and why it is defined as $k=1\ N\ kg^{-1}\ m^{-1}\ s^2$ But does it have an official name? If I were to give it a name I suppose I would maybe call it ...
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What’s the difference between ‘decimated‘ and ‘undecimated’ data?

How is ‘decimated’ data different from ‘undecimated’ data?
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What's the origin of the name“ high energy physics”?

Since the mass of elementary particles are very small, I'm wondering why we call particle physics "high energy physics", why shouldn't it be low energy physics?
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Anti-triplet representation [closed]

What is the anti-triplet representation of a group? Specifically, what is the anti-triplet representation of $SU(3)$?
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2answers
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Where does the expression “golden plate decay” come from?

The decay of $B \to J/\psi K_{S,L} $ is often referenced as "golden plate decay", for example in If there is a B-decay into a CP-eigenstate, like the golden plate decay $B \to J/\psi K_{S,L}...
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1answer
22 views

What’s the difference between FoV and IFoV?

I read that radio telescopes have “huge fields of view (FoV)”, but are unable to precisely localized objects due to their “small instantaneous field of view (IFoV)”. Apparently, somehow the size of ...
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1answer
49 views

Is there a “non-linear limit” of the Dirac equation?

I'm just going through old protocols of oral exams students wrote up. One student writes that he was supposed to derive the "non-linear limit" of the Dirac equation during the exam. Is there ...
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1answer
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What is the difference between toughness and hardness? [duplicate]

What is the difference between toughness and hardness? I came to know about some materials that have low toughness but high hardness such as ceramic tiles and glass. I want to know if it is true that ...
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What's the meaning of $\Delta E-W_{nc}=0 $?

Suppose a system of particles is subject to internal forces, some of which are conservative and some of which are non-conservative. Let $\Delta E$ be the change in mechanical energy of the system as ...
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2answers
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How come random is a wave? [closed]

In Schrodinger's theory of the atom, an electron does not move on a circular path. Its motion is in 3D and its random. It could be anywhere in space. How come they named it to wave form? If it's ...
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What does the term 'high voltage' really mean?

This might be a dumb question but i am not so familiar with the word voltage: What does the textbooks really mean when they say high voltage?. Does that mean: There are more charges so more voltage, ...
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1answer
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How is called the magnitude of acceleration? [duplicate]

According to wikipedia page of velocity: The scalar absolute value (magnitude) of velocity is called speed and according to wikipedia page of acceleration: Accelerations are vector quantities (in ...
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Is there a difference between boson and bosonic?

I read about Bose-Einstein condensate consist of bosonic atoms at incredible low temperature do not obey Pauli exclusion, I am wondering what happens if it is possible to create fermionic photon for ...
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2answers
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Representations of a group

In Griffiths' Introduction to Elementary Particles (2ed), at the end of Sec 4.1, he says that an ordinary scalar belongs to the one-dimensional representation of the rotation group, $SO(3)$, and a ...
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Voltage and Resistance definition

Consider a wire of lenght $L$ and transversal area $A$ that it isn't an ideal conductor, but follows Ohm's Law. After a few computations we have $$-\Delta\phi = \rho\frac{L}{A} I $$ where $\rho$ is ...
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1answer
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Do terms like 'radiowave', 'ultraviolet', 'X-ray' mean the same thing in matter vs in vacuum/air?

I usually use terms like 'radiowave', 'microwave', 'X-ray', etc. to refer to ranges of electromagnetic (EM) frequencies ($f=2\pi/\omega$) or wavelengths ($\lambda = 2\pi/k$) in air or in a vacuum, ...
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Is orbital and wave function are same thing?

As we know that wave functions are the solution of schrodinger wave equation which contains all the information about an electron. We also tought that these wave functions are the atomic orbitals of ...
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1answer
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What is gravitational constant in this context? [closed]

I've been reading an article and it gives me the following formula: $\vec{v}_B(t) = \vec{v}_0 - \mu_sgt \hat u_0$ It governs the velocity of a ball. In its explanation, it says: The ...
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1answer
106 views

What exactly is meant by a “time-reversed Hamiltonian”

For context, I am reading this paper. Basically, the paper makes reference to "evolving with respect to the time-reversed Hamiltonian". I'm slightly unclear as to what this actually means. Here is my ...
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4answers
170 views

Terminology: Is there a good way of saying “non-quantum mechanics” physics?

Does a term for non-QM physics exist - in the sense of classical physics including relativity?
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1answer
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Is surface Tension a Scalar, Vector or a Tensor (2nd order or above)?

I am a bit confused regarding the nature of surface tension. Now, it can be defined as energy (E) per unit area (A). This basically means that surface tension (T) relates a scalar (energy E) with a ...
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5answers
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In physics, are all functions fields?

I really confused if there is a function (mostly in physics, functions represents physical quantities) which is not a field? I feel all functions in physics are fields. Is there any functions which ...
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1answer
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Why is it called the “quenched” approximation in QCD?

The quenched approximation of QCD (or other QCD-like theories) is when you basically ignore fermion loops, i.e. fermions are non-dynamical fields. For quantities that do not involve external fermion ...
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1answer
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Is there a difference between renormalization and renormalization group?

Is there a difference between renormalization and renormalization group? In his book 'Scaling and Renormalization in Statistical Mechanics', John Cardy states the following about the term ...
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1answer
28 views

A word for the tipping level of a bottle

Is there a word for the level at which a bottle needs to be filled such that if even a drop of additional liquid were in that bottle and that bottle were placed on its side on a perfectly horizontal ...
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What is a mode in electromagnetic theory [duplicate]

I am a self learner in quantum opitcs and the books they usually use the words like "single mode" and "multimodes". My question is what is a mode in electromagnetic theory ?
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1answer
36 views

$R_\xi$ gauges and the EM-field

$R_\xi$-gauges are said to be a generalization of the Lorenz gauge. I dont quite get why we add the term $$ \mathcal L_{GF} = - \frac{(\partial_\mu A ^\mu)^2}{2\xi} $$ to the Lagrangian. If i ...
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3answers
270 views

Actual meaning of refraction of light

The definition of refraction which I found on wikipedia is In physics, refraction is the change in direction of a wave passing from one medium to another or from a gradual change in the medium. ...
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What is the name and meaning of the integral of potential energy?

The paper, Significance of Electromagnetic Potentials in the Quantum Theory by Aharonov and Bohm makes reference to a term, $S$. I'm curious as to if this term has a name and to its meaning. $S$ is ...
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1answer
41 views

Kinematics: 2 dimensional vs. 3 dimensional motion

I just studied kinematics and saw "throwing a ball in air" as an example of a 2 dimensional motion. I have a doubt that if we are throwing a ball in space, it should also have a $z$ coordinate, so why ...
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25 views

What exactly is electric flux? [duplicate]

I have seen plenty of definitions and descriptions of electric flux. Most of them say it is the number of field lines per unit area. However how can there be a fixed number of field lines in a unit ...
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Question about Schrodinger equation in atomic units vs in SI units

In SI units, we see that the Schrodinger equation can be written as \begin{align} i\hbar\partial_t \Psi= \left(-\frac{\hbar^2}{2m_e}\Delta_x+V(x)\right)\Psi \end{align} whereas, in atomic units, we ...
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What is the use of $g$-factor for magnetic moment of electron?

$g$-factor is also called the spectroscopic splitting factor according to "Introduction to Solid State Physics" by Charles Kittel. So it can be presumed that it is related to the splitting of levels ...
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4answers
628 views

If velocity in forward and backward directions is positive and negative respectively, then what is it in left and right directions? [closed]

I have defined velocity in forward direction to be positive and negative in the backward direction. So what is the velocity if the body is moving right or left?

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