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

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41 views

Can someone explain what's the difference between all these terms in “Simple Words” with their “applications”? [on hold]

I'm very confused between all these terms. Can someone explain what's the difference between Classical Mechanics, Relativistic Mechanics, Quantum Mechanics, Quantum Field Theory, ...
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1answer
14 views

Object moving with 2 linear accelerations

Say I have an object moving with an acceleration of 5 m/s$^2$. At a certain point X, due to some forces, the acceleration of the object changes from 5 m/s$^2$ to 2 m/s$^2$. Would this change in ...
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1answer
42 views

What does “Standard Model” really refer to?

I am reading the arXiv published paper by Frank Wilczek called "Physics in 100 Years". Apparently, this paper is the printed form of a talk given at Brown University earlier this year (2015). Right ...
3
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1answer
106 views

What is the difference between Chiral anomaly, ABJ anomaly, and Axial anomaly?

I get confuse with these three terms: Chiral anomaly, ABJ anomaly, and Axial anomaly. I can not find standard definition of these three. Is there anyone can describe precisely?
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1answer
63 views

What is the difference between configuration space and phase space?

What is the difference between configuration space and phase space? In particular, I notices that Lagrangians are defined over configuration space and Hamiltonians over phase space. Liouville's ...
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4answers
247 views

Is Parity really violated? (Even though neutrinos are massive)

The weak force couples only to left-chiral fields, which is expressed mathematically by a chiral projection operator $P_L = \frac{1-\gamma_5}{2}$ in the corresponding coupling terms in the Lagrangian. ...
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1answer
96 views

Simple explanation of Coherent integration radar

I have a physics background, and I'm reading some physics data analysis papers where they keep throwing around the term coherent integration. I've done the google search, but the best answer I could ...
0
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1answer
32 views

Voltage and volume, same SI symbol, how to discern between the two? [on hold]

Both are SI quantities that use the same symbol, namely $V$. It annoys me that I might be working with the wrong unit even though it's easy to see if it's voltage or volume by looking to the whole ...
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3answers
213 views

About field gradient

I read the term field gradient in most of the article about magnetic field. I search it online but most of the explanation is about the math. I wonder in physics, what the gradient field really mean? ...
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0answers
36 views

Can anybody explain about phase shift and phase spectrum terms in case of multidimensional signal?

I know about phase of a 1D signal, but when I move into higher dimensions like 2D or 3D etc, it becomes headache to grasp the concept. What do the terms "phase shift" and "phase spectrum" mean in ...
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1answer
48 views

Laplace-Beltrami vs d'Alembert operators in flat vs curved space-time

I am confused with the difference between Laplace-Beltrami (LB) and d'Alembert operators in flat/curved space-time. d'Alembert operator in flat space-time (Minkowski) is defined as $$\Box= ...
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1answer
34 views

How to compute phases of the signals?

Let us take 4 signals which are sinusoidal and periodic. Suppose you are given a phase spectrum or (/and) equation of the (main) signal only and you are said that the given (main) signal is formed of ...
5
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1answer
405 views

“Hard wall”/ “soft wall”

I have encountered those terms in various places. As I understand it, "soft wall" can correspond to a smooth cutoff of some spacetime, while "hard wall" can be a sharp one, which can be described in ...
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2answers
31 views

What does excitation in an atom mean?

This is not regarding the definition of excitation itself. What I'm having trouble with is the difference between "electron excitation" and "atom excitation". When I electron inside the atom gets ...
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0answers
10 views

Circuit providing output? [migrated]

What does it mean for a circuit to provide an output power of say 1000W? Is "circuit providing power" referring to the battery supplying energy to the external circuit, or is it referring to the power ...
3
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3answers
1k views

If an atom is fully ionized by removing all electrons, is it still an atom?

This is a question about terminology. To me, it's clear that the nucleus of an atom is still an atom. But a comment by Willie Wong at Is nature symmetric between particles and antiparticles? raises ...
3
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1answer
55 views

What is the precise definition of “cadence” in astronomy?

I'm finding it difficult to find a precise definition of "cadence" in astronomy. This term is commonly used to describe the data of astronomical surveys. For instance, one of the data products for the ...
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2answers
110 views

Friction force in rolling motion

In rolling without slipping motion we know that the friction acting is static friction and so we treat it as an unknown while solving equations of dynamics. Question: Is the static friction during ...
2
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3answers
47 views

Does lithium-6 “decay” when hit by a neutron?

I am talking about the nuclear reaction $$ ^6\text{Li} + n \rightarrow\ ^4\text{He} +\ ^3\text{H} + 4.78\text{MeV} $$ A neutron hits a lithium-6 nucleus and together they form an alpha and triton ...
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3answers
43 views

What is nuclide notation referring to? Only the nucleus or the whole atom?

sorry that this is an easy question but I am just a bit confused about nuclide notation. When you say e.g. $^{240}_{94}\text{Pu}$, are you referring to the atom of $\text{Pu}$ or only its nucleus? It ...
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1answer
146 views

Does graphene have a honeycomb lattice?

In my grand ignorance I would state that graphene has a honeycomb lattice. Some tend to agree with me and some others do not. I'm curious to know what members of the SE community think is the right ...
0
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1answer
99 views

Square-Cube Law?

I've heard about something called the square-cube law. What is it? All I know of it is that it has something to do with mass of large objects and their gravitational influence.
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2answers
130 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 ...
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1answer
26 views

What does “interact via strong force” mean?

I was just wondering if the words "strong force" and "strong interaction" are interchangeable? Also, these are referring to "strong nuclear force", correct? Then what does it mean for particles to ...
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2answers
523 views

Should it be obvious that independent quantum states are composed by taking the tensor product?

My text introduces multi-quibt quantum states with the example of a state that can be "factored" into two (non-entangled) substates. It then goes on to suggest that it should be obvious1 that the ...
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1answer
42 views

What is space charge and how to calculate it?

I want to clarify the meaning of space charge. What I know is that the space charge is the total charge in a small region in space. I really confuse this in the ion beam context. Many text book says ...
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2answers
80 views

Making sense out of covariance and contravariance

I just read about co- and contravariant vectors and I am not sure that I got it right: If we imagine that we have a n-dimensional manifold $M$ then a tangent space is spanned by the vectors ...
2
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2answers
42 views

Why does one call $B$ the magnetic induction?

When one studies electrostatics we have the electric field $\mathbf{E}$. This object usually is introduced as a field produced by a configuration of charges such that the force on another charge $Q$ ...
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2answers
58 views

What is third cosmic velocity?

I have been studying Gravitation chapter and there I found one term : Third cosmic velocity which is also known as interstellar speed. So what is it ? What it really tells about? I tried to gather ...
2
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1answer
171 views

What was Feynman's famous formula?

In Welton(1983), Memories of Feynman, Welton mentions two formulas which he denotes as Feynman's Famous Formula (FFF) and FFF #2. Which famous formulas is he talking about? Is he maybe talking about ...
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2answers
189 views

Correct terminology for combined kinematic and dynamic state

The kinematic state is defined as the position and orientation in space. The dynamic state is defined as the associated velocities. What is the correct terminology for the combined kinematic and ...
3
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1answer
36 views

What's the difference between “Ohmic dissipation”, “Joule heating”, “ion drag” and “resistive heating”?

The following terms are sometimes used to refer to ... more or less ... the same thing by different people and in different contexts (electronic circuits vs. plasma physics, etc.): Ohmic ...
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1answer
167 views

Group representations as vectors and isomorphism between weights and matrix generators

This might be something basic, but it is unclear to me. So I am used to work with representations of groups as matrices. These matrices represent the structure of the Lie algebra by satisfying the ...
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3answers
111 views

What is a “Reversed Effective Force”?

I have some confusion about the "Reversed effective force" as it appears in the derivation of D'Alembert's principle. In Goldstein d'Alembert's principle is given as: $(F-\dot{p}) \cdot \delta r = ...
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3answers
370 views

Conversion of ideal gas to real gas via $Z$ compression factor

The ideal gas equation $PV=nRT$ can be converted into real gas equation by compression factor $Z$ i.e $PV=Z~ nRT)$. My question is what is $Z$ and how does it arise? Is $PV/nRT$ a compression ratio of ...
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0answers
23 views

What is the correct terminology for a “symplectic covariant” equation?

A Lorentz covariant equation is one that takes the same form even when a Lorentz transformation is applied to each variable. Lorentz covariance is generally made manifest by writing the equation with ...
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2answers
143 views

Locally flat coordinate and Locally inertial frame

I am having some doubts on myself regarding the above concepts in General Relativity. First, I want to point out how I understand them so far. A male observer follows a timelike worldline ($\gamma$) ...
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2answers
99 views

What are global and local gauge invariance defined as they are?

I'm sorry for the triviality of my questions. Why is $\bar{\psi} = e^{i \theta}\bar{\psi}$, where $\theta$ is a real number, used as the global gauge transformation? Why $e^{i \theta}$; what's the ...
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2answers
16k views

What is the difference between angular speed and tangential speed in a circular motion?

I was looking a long time for the way the equations of this two speeds are obtained, and i found pretty much nothing important, so can someone explain how are those obtained, and which is the ...
2
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1answer
244 views

Is there a difference between Electric and Electrostatic Field?

Is there a difference between Electric and Electrostatic Field? All I know is that they both represented with same law suppose we have a Charge placed at the Origin: ...
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2answers
245 views

Quantum hadrodynamics

What is quantum hadrodynamics? Can anybody give a proper explanation? What are the standard books and sources of information that can be found on the internet for better understanding?
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1answer
38 views

Holonomic constraints and degrees of freedom?

Can we see that a constraint can decrease the degrees of freedom of a system if and only if it is holonomic. Either way please can you explain why?
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1answer
56 views

Second law of thermodynamics (in terms of entropy)

Is the second law of thermodynamics (in terms of entropy) for closed systems or isolated systems? I thought it must be valid for isolated systems, such as the Universe. But the book Fundamentals of ...
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1answer
530 views

Name of the process that causes ice to melt under pressure and refreeze after

I remember a physics experiment from school where a wire with weights on each end was placed over a block of ice. The pressure of the wire caused the ice to melt underneath and refreeze once the ...
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0answers
16 views

What exactly is meant by “locating points in spacetime”, in the RT?

In this (presently quite popular) answer to another recent question of mine concerning foundations of the (Einstein's) theory of relativity, it is asserted that "Any observer can construct a ...
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2answers
68 views

Are the words “coincident” and “simultaneous” considered synonymous? Else, please explain the difference

In discussions, experimental and thought-experimental descriptions (especially concerning the Theory of Relativity) the words "coincident" and "simultaneous" appear, notably for instance in the ...
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1answer
62 views

What is “adjustable constant”?

This is quoted from A.P.French's Vibrations & Waves. Explicit differential form of linear harmonic oscillator is: $$ m\dfrac{d^2x}{dt^2} + kx = 0 \quad \& \quad \dfrac{1}{2} ...
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2answers
44 views

On Elementary Particles

The mass of positron and electron are same. Also their charges are equal in magnitude but opposite in nature. Then why positron is not called one of the elementary particles? Is this only because it ...
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2answers
28 views

What is the formula of power of an optical instrument?

I have searched and found that the power of a lens, with surrounding medium of refractive index $n$, is $n/f$ where $f$ is the focal length, the formula is $$n/f=(n'-n)/R1 + (n-n')/R2.$$ But in my ...
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2answers
162 views

What exactly is meant by saying that two events had been “simultaneous in an inertial frame”?

In order to address my question based on a concrete example setup let the following two separate events be given: participants $A$ and $J$ encountering each other in passing (additional participants ...