Questions tagged [terminology]

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

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37 views

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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2answers
133 views

Is there a special name for thermodynamic process during which no work is performed?

Let $W$ denote the work done on a system during a thermodynamic process. Is there a commonly-accepted, dedicated term for a process during which $W=0$?
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4answers
377 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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11answers
31k views

What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)?

This is a confused part ever since I started learning electricity. What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? All of them have ...
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0answers
45 views

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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2answers
196 views

$B$-meson naming convention

An unbarred $B$-meson contains $\bar{b}$ (an anti-bottom quark), whereas a barred $\bar{B}$-meson contains $b$ (a bottom quark). What is the historical reason for this hellish naming convention?
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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
62 views

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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6answers
70k views

Why and how does negative velocity exist?

Why and how does negative velocity exist? I have read on the internet about negative velocity but I still don't understand how it can even exist since time is positive and so is length. By doing some ...
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3answers
1k 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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0answers
22 views

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
2k views

Difference between Oscillatory motion and vibratory motion

What is the difference between oscillatory motion and vibratory motion. I have read in my book that "If the amplitude of oscillatory motion is extremely small,the motion is called vibratory motion". ...
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1answer
134 views

Transmission coefficient and transmission probability

Are transmission coefficient and transmission probability the same terms? If not, could you please explain how they are related to each other?
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3answers
584 views

What is the definition of “Complexity” in physics? Is it quantifiable?

I don't know much about the discipline of "Complex systems studies" but I know in the field of "Statistical mechanics" there is much talk about the "Complexity of the system&...
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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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1answer
178 views

When should we consider “reverse Heisenberg” evolution of operators?

In Quantum Mechanics, the Heisenberg evolution of an observable $\hat{o}$ is defined as $$ \hat{o}(t) = U(t,0)^{\dagger} \hat{o} U(t,0) $$ where $U(t,0)$ is the unitary time-evolution operator from ...
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2answers
87 views

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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5answers
4k views

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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3answers
1k 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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2answers
60 views

What is a pseudopure state?

In the paper titled "Experimental Implementation of the Quantum Baker’s Map" by Weinstein et al. (Phys. Rev. Let. 89 (2002)), the author says something like [...] the pseudopure state corresponding ...
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6answers
7k views

What is the connection between special and general relativity?

What is the connection between special and general relativity? As I understand general relativity does not need the assumption on speed of light constant. It is about the relation between mass and ...
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0answers
19 views

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
523 views

Difference between yaw angle and slip angle

What's the difference between slip angle and yaw angle (speaking about cars)? It seems they both are the angle between the actual direction of travel and the direction towards which it is pointing.
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3answers
2k views

What is the meaning of “matter” in physics?

What is the meaning of matter in physics? By defining matter in terms of mass and mass in terms of matter in physics, are we not forming circular definitions? Please give a meaning of "matter" in ...
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1answer
23 views

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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3answers
135 views

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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1answer
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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
457 views

What is zero-order transmission spectrum?

In the paper The extraordinary optical transmission through subwavelength hole arrays by T. W. Ebbesen it is shown at particular wavelength there is a peak observed in zero order transmission spectrum....
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1answer
30 views

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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1answer
402 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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3answers
73 views

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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44 views

What’s the difference between ‘decimated‘ and ‘undecimated’ data?

How is ‘decimated’ data different from ‘undecimated’ data?
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1answer
149 views

What are the differences and similarities between dynamical tunneling and quantum tunneling?

In case of a double well potential, particle can tunnel from one well to another and this process is known as quantum tunneling or tunneling in general. I want to know about dynamical tunneling and ...
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1answer
142 views

Adiabatic Availability?

In the textbook "Thermodynamics: Foundations and Applications" by Elias P. Gyftopoulas and Gian Paolo Beretta (Dover). In chapter 5, on page 73 (section 5.3) the book says: Adiabatic availability ...
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3answers
81 views

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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2answers
43 views

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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5answers
37k views

What is the difference between electromagnet and solenoid?

What is the difference between electromagnet and solenoid? Both these terms seem as the same thing to me. The only difference that I can find seems to be that an electromagnet contains a soft iron ...
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2answers
34 views

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
31 views

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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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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2answers
969 views

Variables in calculation of drag coefficient

Okay, so I looked up drag force equation, and I found that the equation involved the drag coefficient. Then I looked up the drag coefficient, and the equation for it involved the drag force. ...
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18answers
2k views

What is an event in Special Relativity?

Lorentz transformations help us transform coordinates of one frame to that of another. For example, let the coordinates of an event in an inertial frame $S$ be $(x, t)$, then the coordinates in frame ...
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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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0answers
48 views

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
384 views

Is a bending wave transverse or longitudinal?

A bending wave in a metal bar or string is simply called a transverse wave because the macroscopic oscillation is transverse. However, paradoxically, in a frame co-moving with the atoms, the atoms are ...
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1answer
65 views

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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3answers
137 views

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