Questions tagged [terminology]

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

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What does $f(x)$ satisfies the given equation means?

In problem 2.1 part c of Introduction to Quantum Mechanics, 3rd ed. by Griffiths and Schroeter, they ask the reader to prove that if the potential is an even function of $x$, then if $\psi(x)$ ...
GedankenExperimentalist's user avatar
3 votes
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Difference between real operators and Hermitian operators in quantum mechanics

I'm reading some lecture notes on quantum mechanics, while describing the rigid rotor in bra-ket notation, the author mentions the parity operator $\hat{P}$ acting on kets as $\hat{P} \left \lvert m \...
Andrea's user avatar
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Are vacuum energy, zero point energy and vacuum fluctuations the same thing?

im confused about the relationship between these terms, my intuition tells me that vacuum energy and zero point energy are synonymous and that they are a consequence of vacuum fluctuations. But I ...
KleinMoretti's user avatar
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Can we call numbers unidirectional vectors? [duplicate]

I have never thought so deeply about addition and subtraction. But today I noticed something. When adding or subtracting numbers, we actually apply the rules we use for vectors (for example, the ...
Bilgehan Yılmaz's user avatar
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Name of Equation $Q = \Delta P / R$

A very fundamental equation in understanding fluid flow is $Q = \Delta P / R$. When the flow is through a cylindrical pipe of constant radius, $R=8\eta L/\pi r^4$ can be substituted to give Poiseuille'...
E Tam's user avatar
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Is Principle of Least Action a first principle? [closed]

It is on the basis of Principle of Least Action, that Lagrangian mechanics is built upon, and is responsible for light travelling in a straight line. Is its the classical equivalent of Schrodinger's ...
megamonster68's user avatar
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Terminology: any specific name for the amount of something in a given volume (at a given time)?

For quantities such as electric charge, amount of substance (or number of particles), and energy, the flux of the quantity is defined as the amount of quantity flowing through a predefined surface in ...
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Dielectrics terminology

I got confused while reading about dielectrics, so basically my question is: (a) what's the difference between a (homogenous and isotropic) dielectric and (linear) dielectric? Does the first imply the ...
tensorman666's user avatar
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Constraint Equation and Equation of Motion

I was doing a question which was to find the number of generalized coordinates needed to describe a particle with the motion: $x(t)=2a\sin(\omega t) $ $y(t)=a\cos(2\omega t)$ So I solved it and found ...
Kutubkhan Bhatiya's user avatar
4 votes
4 answers
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Why do we call the Riemann curvature tensor the curvature of spacetime rather than the curvature tensor of its tangent bundle?

I was studying the mathematical description of gauge theories (in terms of bundle, connection, curvature,...) and something bothers me in the terminology when I compare it with general relativity. In ...
eomp's user avatar
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How is matter defined in physics? [duplicate]

I have heard matter defined as energy within a closed system and that any such closed system will have mass. Is this correct?
Gerry's user avatar
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What is the branch of physics that asks the question 'what was before the Big Bang'?

What is the branch of physics that asks the question 'what was before the Big Bang', assuming the Big Bang is truly what happened at the beginning of the universe? If there could be a better model ...
Bruce M's user avatar
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1 answer
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What does instantaneous velocity mean? [duplicate]

What does instantaneous velocity mean? on google it says "Instantaneous means something happens very quickly, in a single moment. It's similar to the meaning of "instant", but most ...
Intensed's user avatar
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1 answer
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Is there a difference between the spectral decomposition and the orthonormal decomposition of a matrix?

I was studying quantum information from Nielsen and Chuang's book and I got a little bit confused because sometimes they use the terms "spectral decomposition" and "orthonormal ...
Anis Younes's user avatar
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Why is this called a `Harmonic Oscillator Chain'?

Consider the following general setup: Assume have a chain of atoms (of mass $m=1$) in one dimension interacting with their nearest neighbor through a interaction potential $U$, and which are in an ...
Monty's user avatar
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Unit in unit area

Pressure is defined as force per unit area. What is the meaning of unit and why is the term unit used with area?
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What is the correct term for $\nabla\phi$? Co-vector or 1-form or both?

In the olden days, $\nabla\phi$ was used to be called a covariant vector (Weinberg used this language in his book Gravitation & Cosmology). But this terminology is considered bad for several ...
Solidification's user avatar
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What is the difference between granulatiion, mesogranulation, supergranulation and giant cells in sun's photosphere?

Help me understand the differences between granulation, mesogranulation, supergranulation, and giant cells and at what depth they are created.
Devesh Sharma's user avatar
6 votes
2 answers
170 views

Why is the angular momentum of photon $\hbar$ if the spin is 1?

I saw in many places that the spin of photon which is a boson is 1. Which we can write as $s=1$. I also saw that the angular momentum of a particle with spin $s$ is $\sqrt{s(s+1)}\hbar$. If both is ...
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What is the wavelength range of X-rays?

I was reading and came across the following paragraph The X-rays thus produced by many electrons make up the continuous spectrum of Figure 2-10 and are very many discrete photons whose wavelengths ...
Jack's user avatar
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What do we call a material property that has non-equal values when evaluated in opposite directions?

What do we call a material property that has non-equal values when evaluated in opposite directions? That is, if the material property $k_{ij}$ has a value of $X$ along the direction defined by the ...
Armadillo's user avatar
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What is the difference between wavefunction renormalization and field strength renormalization?

A while ago I asked a question asking what is field strength renormalization (What exactly is field strength renormalization?). I now have a better way of thinking about this, which is that it relates ...
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Are Lissajous figures SHM(s)?

Are Lissajous figures SHM(s)? I have been studying perpendicular superposition of SHM(s). And i understand that 2 shm having same angular frequency and differed by phase pi/2 when superimposed ...
Amit Rai's user avatar
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On the physical meaning of functionals and the interpretation of their output numbers

I am studying about functionals, and while looking for some examples of functionals in physics, I have run into this handout . Here are two questions of mine. 1- This handout starts as follows (the ...
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What does it mean to probe a certain energy scale?

For example, what does it mean that the LHC probe the electroweak scale, $M_{EW} \sim 10^3 GeV$? Also why is this energy called the electroweak scale?
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Can the lattice of an element with face-centered cubic (FCC) crystal structure be regarded as simple cubic (SC)?

According to Introduction to Solid State Physics by C. Kittel, An ideal crystal is constructed by the infinite repetition of identical groups of atoms. A group is called the basis. The set of ...
apadana's user avatar
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What is the proper term for the linear, surface area, and volume components in density equations?

Say one is looking at charge density. Linear charge density would be given by $$ \lambda = \frac Q \ell $$ surface charge density would by given by $$ \sigma = \frac Q A $$ and volume charge density ...
Kalcifer's user avatar
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What is a hypersurface?

What is the concept of hypersurface in general relativity? I know it could be characterized into three categories but how do we define hypersurface (in general) in physics? I didn't get what thing it ...
Talha Ahmed's user avatar
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If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?

If we change the direction of the connections in a step-down transformer, will it become a step-up transformer?
Akshat Parmar's user avatar
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3 answers
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Is Retardation and Deceleration the same thing? [closed]

Does, Deceleration always have to be Retardation? Or, can there be Deceleration without Retardation.
Kamran Noor's user avatar
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When does a theory decouple?

The question is very broad, but it seems to me that the term 'to decouple' is also used in various contexts. For example, neutrinos decouple from the photons in the early Universe, when the ...
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Difference between - & [closed]

I’m taking Introductions to Physics book. In the book on the chapter “Physics & Mathematics” there was one question where we were supposed to find the magnitude of work done from given vectors ...
Prabhas Kumar's user avatar
-1 votes
1 answer
164 views

Can you have a charge of 0 C?

My textbook says that there are only two types of charges: positive and negative. Then would it be correct to say that the neutron (for instance) has charge $0\ \rm C$?
Shoes's user avatar
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What is difference between normal force and reaction force? [duplicate]

according to my book the perpendicular component of reaction force is called normal force when there is contact between two bodies. I can not understand that how for example when we jump we pushes the ...
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2 answers
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What is normal force and when it acts?

what are contact forces and according to: https://www.physicsclassroom.com/class/newtlaws/Lesson-2/Types-of-Forces it says there are 6 types of contact forces. I am having doubt with applied force and ...
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1 vote
2 answers
241 views

What is a parent Hamiltonian? [closed]

The term is used throughout the literature but I was not able to find a definition or even a paper properly introducing the term. What does a Hamiltonian have to satisfy to be a parent Hamiltonian? An ...
Suppenkasper's user avatar
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What is an example of a contact force that is not a normal force?

I have a question about contact force and normal force. whenever two bodies are in contact and one body tries to push another body there will be a normal force acting between them. like when we push ...
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1 vote
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Contact terms in Schwinger-Dyson equation and Ward-identity

I am reading Weigand's notes for the derivation of Ward-identity. The Second last paragraph on page 133, says the following statement "The Schwinger-Dyson equation and the Ward-identity show ...
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Is this motion rotation or curvelinear translation?

Arrow orbit around point C like graph show. Is motion of arrow, rotation or curvelinear translation according to physics definition? What is definition and types of translation and rotation? I find ...
user707264's user avatar
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54 views

What is the verb for plasma formation?

Simple question: what is the verb for the phase change from gas (or any other "regular" state of matter) to plasma? The best thing I can think of is "ionization into a plasma" but ...
Next-Door Tech's user avatar
1 vote
1 answer
156 views

Dust solutions in general relativity

What is the precise definition of a dust solution in general relativity? If the Einstein tensor of a metric has only the first diagonal term non-zero, it that sufficient for that solution to be called ...
jay121's user avatar
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What is the literal meaning of displacement current?

I think I know what the displacement current is. But I don't know why they use the word "displacement" exactly. What is the literal meaning of "displacement" of the displacement ...
superkappy's user avatar
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1 answer
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Adjectives regarding interfaces

I'm studying X-Ray reflectivity at interfaces and the book I'm reading reads: ... The ideally flat, but graded interface, and the ideally sharp, but roughened interface, will be considered... I'm ...
chemdamned's user avatar
6 votes
2 answers
365 views

Help understanding quote on theory and knowledge in Gravitation (Misner, Wheeler, & Thorne, 2017)

I came across an interesting discussion at the start of chapter 3 of MWT Gravitation. It reads: Here and elsewhere in science, as stressed not least by Henri Poincare, that view is out of date which ...
akozi's user avatar
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Difference between Bravais lattice, point lattice and space lattice

I am good at crystallographic terminologies. Can somebody explain to me what is the difference between Bravais lattice, point lattice, and space lattice, if any?
Solidification's user avatar
1 vote
1 answer
106 views

WKB method as a Semiclassical Approach

A naive question about WKB approach. It is dubbed to be a "semiclassical" method. What is precisely mean in quantum mechanical context to be "semiclassical"? Wikipedia states that ...
user267839's user avatar
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Is Ansatz compared to Solution like Hypothesis compared to Theory?

I wonder how you would describe a correct use of the term "ansatz" in English physics literature? In German, "ein Ansatz" simply means "an approach". Could we say, in the ...
user373714's user avatar
2 votes
2 answers
394 views

Can someone explain 'virtual mass' in fluids in simple words (for a dummy/high schooler)?

so I recently came across the term 'virtual mass' and when I looked up more about it, it just gave me some stuff about fluid mechanics that I dont understand properly. My understanding of virtual mass ...
Infinite Void's user avatar
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0 answers
64 views

Terminology: angular frequency vs frequency

I am confused about the usage of the terms frequency and angular frequency in physics texts. E.g. in the book "Classical Electrodynamics" of J.D. Jackson, one considers in formula (7.3) page ...
helsto's user avatar
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4 votes
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What is altermagnetism?

Since 2022, I have come across several papers on Altermagnetism, a novel phase of matter that breaks time reversal, but without a net magnetization. It also has many other interesting properties. What ...
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