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

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2
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1answer
26 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 ...
3
votes
1answer
69 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 ...
0
votes
1answer
43 views

If the axis of rotation is fixed, is it ok to say clockwise torque?

I know that the direction of torque is along the axis of rotation, but would it be acceptable to say, for example considering a vertical thin rod in the x-y plane with a force acting on the bottom end ...
3
votes
2answers
262 views

Where does this term “shell” with prefix “on-/off-” come from?

Is there some historical reasons or is there a specific reason behind it? This question is connected to: Why on-shell vs. off-shell matters?
-1
votes
1answer
78 views

Looking for the name of a physical phenomenon in fluids' mechanics

I have not even an idea about how I would search for that on Google, that is why I'm trying my chance here. As electrical engineer I have no clue about fluid mechanics. We all now that when water is ...
2
votes
0answers
65 views

Is there any distinction between these products: scalar, dot, inner? [migrated]

I hope you will forgive a math question that comes up in physics contexts where language is loose. There is a product which can be defined on a vector space that takes two vectors and returns a ...
0
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2answers
62 views

What is the principle of equivalence in thermodynamics?

I've been searching for this for a while. There is a principle of equivalence in general relativity: http://en.wikipedia.org/wiki/Equivalence_principle But I need the principle of equivalence in ...
1
vote
1answer
36 views

Gravity force and dark energy [duplicate]

If gravity is a fundamental force which bends spacetime and dark energy is energy which stretches spacetime, what is the difference between the terms force and energy?
2
votes
2answers
87 views

Why “Dark Energy” is called energy instead of force?

The overly simplified explanation I'm giving myself right now is dark energy causes the opposite of what gravity does, that's why the universe is expanding. Now where gravity is a force, why dark ...
2
votes
2answers
87 views

Why is the Faraday Tensor derived from the Lorentz force?

If we start from the Lorentz force, $$\textbf{F}=q\textbf{E} +q\textbf{v}\times\textbf{B}$$ and use the four velocity u$^{\mu}$ and the four momentum p$^{\nu}$, then we get to ...
0
votes
3answers
59 views

Commutator summation notation

I have the relation $ e^L M e^{-L}=\sum_{n=0}^\infty \frac 1{n!} [L,M]_{(n)}$ where $L$ and $M$ are operators. What does the subscript $n$ after the commutator bracket denote?
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0answers
19 views

What is Fermi energy and Fermi level? [duplicate]

What is meant by Fermi level and Fermi energy? And what is the difference between the two?
4
votes
1answer
107 views

Which transformations are canonical?

Which transformations are canonical? Why do canonical transformations preserve the measure of integration in phase space?
3
votes
1answer
152 views

Why have $n$, $\ell$, $m_\ell$, $m_s$ been picked as quantum number symbols *in this order*?

I’m learning about electron configurations and don’t quite understand why $n$, $\ell$, $m_\ell$, $m_s$ have been picked as symbols for the quantum numbers. As far as I understand it, the principal ...
2
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1answer
56 views

Difference between steady state and equilibrium?

In semiconductor physics, what is the difference between steady state and equilibrium. How analysis of devices varies in these processes?
0
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2answers
65 views

Should theory be the appropriate term? [duplicate]

Should theory be the appropriate term? I mean, for example, because of the quantum field theory we have been able to find the subatomic particles that it theorized and make the Standard Model. Why ...
1
vote
1answer
97 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.
0
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0answers
47 views

Actions at a distance vs. contact interaction

The ancestors could not imagine an action at a distance (in German: "Fernwirkung"). Today physicists don't take serious its opposite anymore (in German: "Kontaktwechselwirkung"). So my first question ...
0
votes
1answer
35 views

Valley meaning explanation for foreigner

English is not my native language and I have some hard time translating this word. I was searching in couple dictionaries(both paper and online) and could not find it. Could anyone provide me ...
1
vote
1answer
20 views

Differentiating between mass number (A) and activity (A) in a nomenclature/glossary

I'm not sure if this is the best place to ask this question, but as it's related to the terminology of nuclear physics I thought it would probably be a logical place to start. I'm currently writing ...
3
votes
2answers
59 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 ...
0
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2answers
64 views

Terminology for line integral of magnetic field

One of the quantities appearing in the integral form of Maxwell's Equations is the line integral of the magnetic field around a closed loop. (The relevant equation states that this is equal to the ...
1
vote
1answer
37 views

The exact definition of conjugate momentum density

After checking various websites, I've seen the conjugate momentum density defined as either: \begin{align*} P_r ~=~ \frac{\partial \mathcal{L}}{\partial \dot{A}_r} \end{align*} or \begin{align*} P_r ...
0
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0answers
34 views

Difference between RPA and generalized RPA

The random phase approximation (RPA) is an approximation method in condensed matter physics and in nuclear physics. What is the difference between RPA and generalized RPA?
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0answers
18 views

What is “thermal undulation” in the context of lipid bilayers?

What is thermal undulation in the context of lipid bilayers? Is it another word for "thermal fluctuation"?
0
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1answer
32 views

Single-channel vs multi-channel scattering

I am studying quantum scattering and stumbled upon the "scattering channel" and "single- and multi-channel scattering" terms. However, I didn't manage to find any sufficiently formal definitions of ...
4
votes
2answers
58 views

Definition of quantum anharmonicity

I have been reading research papers in mathematical physics for some months now, and I've seen the the term "anharmonic oscillator" quite frequently. At first I assumed that given a Schrodinger ...
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1answer
25 views

Equivalent temperature: laser and cell containing Rb

What's the meaning of "equivalent temperature" related to a cell containing rubidium and crossed by laser?
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0answers
154 views

Morphisms between chiral CFTs

This is a question about terminology. Given two vertex algebras $V_1$ and $V_2$ (= chiral CFTs), there are two kinds of maps $V_1\to V_2$ that one might want to consider. 1) Morphisms of VOAs that ...
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votes
1answer
52 views

What is a phrase for testing for a certain result? [closed]

Is there a word or phrase for when someone is testing for a certain result thereby skewing his findings?
5
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1answer
155 views

Why the speed of light is represented by $c$? [closed]

In almost every textbook, I've found that the speed of light is $c \approx 3 \times 10^8\: \mathrm{m/s}$. I wonder why it's just $c$ ?
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2answers
223 views

What does the magnitude of the acceleration mean?

I am a little confused as to what the magnitude of acceleration is and what it means.
0
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0answers
21 views

Is there a generic term for orbital groups such as $e_g$ and $t_{2g}$?

I am looking for a generic term for sets of atomic orbitals (viz. spherical harmonics) which are grouped by crystal symmetry. The most familiar examples would be $e_g$ and $t_{2g}$ (in cubic ...
3
votes
1answer
99 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 ...
4
votes
3answers
156 views

Defining left and right independent of a human body?

Is it possible to define right and left independent of the asymmetric human body? I am unable to think of such a definition without circular reasoning. Example: If you are facing east, your left ...
2
votes
1answer
51 views

Any difference between “Mueller matrix” and “Scattering matrix”?

I find in some references 4x4 Mueller matrix and in other references 4x4 Scattering matrix. Are they different or identical? If they are different, I would like to know the book or any research ...
0
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3answers
68 views

Meaning of invariable

Invariable means which is not variable i.e. can't be changed. Recently I have seen a sentence when reading a chapter based on measurement: The accepted standards must be accessible to those who ...
5
votes
1answer
78 views

Why are “quadratures” called this way?

In quantum optics (and hence also cv quantum information), given the annihilation and creation operators of the electromagnetic fields $a$ and $a^{\dagger}$, the "position" and "momentum" operators ...
1
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3answers
67 views

Direction of motion

What does the term direction of motion actually mean? Is it a direction where a particle is moving or the direction of its velocity? For example, what is the direction of motion of a projectile in ...
0
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0answers
21 views

Origin of the names for the decay chains

Is there any reason for the names of the decay chains? As shown in this chart (larger version here): only the Thorium chain starts on an isotope of the element it takes its name from, and it can ...
3
votes
2answers
86 views

Why is it tension in surface tension?

Why is it called surface tension not surface compression?
0
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1answer
101 views

A basic question: what is accelerating voltage? [closed]

Or would it be acceleration voltage? Acceleration sounds like it makes more sense, but my paper says accelerating. What are possible ways you could go about calculating it?
-1
votes
1answer
70 views

Relativistic momentum and mass [duplicate]

Is there even a relativistic mass or just relativistic momentum? How does one reason to prefer one over another? What is the problem with saying a hot gas will have more mass/inertia to it?
2
votes
0answers
49 views

What is the 1/2 spin analog of the graviton called?

In some supergravities you have the gravition, gravitino, graviphoton and graviscalar. Each is analogous to each other in only sharing gravitational properties and nothing else. They differ by spin ...
4
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1answer
188 views

What is the difference between the words transparent and translucent?

Merriam Webster defines transparent as: Having the property of transmitting light without appreciable scattering so that bodies lying beyond are seen clearly. And translucent as: ...
0
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2answers
493 views

What are virtual objects, Reflection of light? [duplicate]

While studying reflection through a plane mirror, I have been told that when the object is real the image will be virtual and the image will be real while the object is virtual. What are virtual ...
1
vote
4answers
139 views

Space-like and time-like: where do the names come from?

Space-like separated events are events that, in a well-chosen reference frame, can take place at the same time but never happen at the same location. On the other hand for time-like events, one can ...
2
votes
1answer
72 views

Name for thermodynamic derivative $dP/dT|_V$?

While trying to express the isoentropic sound speed as partial derivatives of $V$ and $T$ only I end up, as part of the longer expression with $dP/dT|_V$ (which according to a Maxwell relation is the ...
3
votes
1answer
43 views

What is a Nyquist edge?

I've come to this sentence and I don't understand the term Nyquist edge. Because observing in the FM band is not feasible, a sampling frequency of 200 MHz has been chosen for most of the receiver ...
6
votes
1answer
71 views

What is “kinematic inversion” (from geophysics) in mathematical terms?

I am a mathematician working on a seismic imaging problem, and am currently (attempting to) read some geophysics papers (this one (Ruiz, Madariaga 2011) and this one (Di Carli, Francois-Holden, ...