Questions tagged [terminology]

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

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Fluids mixture density prediction

As you know 100 ml of H2O mixed with 100 ml ethanol is not 200 ml What is the official name of this 'volume loss'? Is it possible, and if so, how, to calculate, before mixing, what the density of a ...
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370 views

Definition of anode and cathode in photoelectric effect

I've read the definition of anode which is that oxidation happens there and thus electrons are leaving the anode. In photoelectric effect we radiate the cathode which is connected to the negative ...
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Can we say $i=i_{0}\lvert\sin(\omega t+ \phi) \rvert$ is alternating current?

$$i=i_{0}\lvert\sin(\omega t+ \phi) \rvert$$ $i_{0}>0$. Can we say that the current described by the above equation is an alternating current? $$i=i_{0}\sin(\omega t+ \phi)$$ We are mostly ...
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27 views

Reciprocal of molar volume

Is there a name for the reciprocal of the molar volume of a pure substance? This question suggests molar density and this answer, concentration. However, molar density is not consistent with the use ...
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175 views

Is spacetime really not physical? [closed]

This question has nothing to do with the expansion of space or the speed of the expansion. I do understand that space expansion is not constrained by the speed of light limit, but I am not asking ...
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Why is the diamond norm called like that?

The diamond norm is a measure of the distance between two quantum channels. If $\mathcal{E}_1$ and $\mathcal{E}_2$ are two channels, then the diamond norm is defined as $$ \delta^{\diamond}(\mathcal{...
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54 views

Ghost exorcisms of fields?

In Mack's paper "D-independent representation of Conformal Field Theories in D dimensions via transformation to auxiliary Dual Resonance Models. Scalar amplitudes", he makes the following statement ...
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24 views

Latent Heat and Ordinary Heat?

We have a name for the thermal energy associated with the change of potential energy during a phase transition. Unless I'm very mistaken, we call this latent heat. Here we have $Q=mL$. But what ...
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69 views

What's the difference between repulsive Delta function and Attractive Delta Function?

What's the difference between repulsive Delta function and Attractive Delta Function? I need to clear the concept. Please note that I know what's the Delta function.
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How does the term “time-integrated flux density” apply to the effluence of a stream of atoms on a surface?

I just edited this answer to read Kapton (again from SMAD), will degrade at a rate of 2.8 μm for every $10^{24}$ atoms/m$^2$ of atomic oxygen time-integrated flux density encountered, with silver ...
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81 views

Is there a name for the unit “Ampere meter”?

Motivation: I'm doing a homework problem involving a rod sliding freely down a pair of parallel conducting rails. I've got a quantity of unit $\mathrm{A \cdot m}$ and want to know what I should name ...
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107 views

Are absorption and attenuation the same thing?

Are absorption and attenuation different words for the same thing? Wikipedia separate has articles on Absorption (Acoustics) and Accoustic Attenuation. I don't see a clear physical distinction between ...
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68 views

Is there any synonym to the “flaring out condition” of travesable wormholes?

Given the knowledge of Einstein Field Equations, the one could ask if it is possible to connect asymptotically regions of a given spacetime, such that a time-like curve is possible to transit between ...
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Historical meaning of action

In the Feynman lectures, it is stated Also, I should say that $S$ is not really called the ‘action’ by the most precise and pedantic people. It is called ‘Hamilton´s first principal function.’ Now ...
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38 views

Physics terminology: Can a light beam be displaced?

Say you have a rotating mirror and a fixed laser beam pointed towards the mirror such that the reflection of the beam changes direction. Can you say that the light beam has been displaced? Why or ...
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Why is the ångström not a metric unit? And why is the ångström spelt with the Scandinavian letters “å” and “ö”?

The website here http://unitsofmeasure.org/ucum.html tells us whether every unit is metric or not. Metric units can be multipled by a power of 10 and can be combined with a prefix. 1 ångström is ...
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Is there a noun for a material that absorbs, scatters and luminesces?

I know Luminophore is used for molecules or nanocrystals which absorbs and emit light, and Scatterer is used for materials which scatter light (elastically or inelastically). I suppose it would be ...
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415 views

What is the difference between scattering and absorption/emission?

As far as I know, scattering occurs when light excites the atoms or molecules to their higher energy state(virtual state for scattering) followed by emitting photons corresponding to energy ...
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Kinematics: Circular Motion

What is the difference between angular velocity and angular speed? Is angular velocity after one complete rotation zero? Is the magnitude of angular velocity always equal to angular speed?
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Elongation of a simple pendulum

One of the questions on this weeks question sheet asks for the maximum elongation of a simple pendulum. The pendulum is set in motion on the moon with f = 0.5Hz. What is meant by the elongation of the ...
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10 views

Use of “rate function” as rate over density

Heggie (1975) uses the term rate function to express the ratio of the rate $R$ of some event (for example the dissociation of a given binary star by the interaction with a passing field star) with the ...
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136 views

What is the difference between Motional EMF and Hall EMF?

What is the difference between Motional EMF and Hall EMF?
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What is the External force? [closed]

In a vacuum, a uniform electric field of strength $E$ is applied in the positive x-axis direction. When you carry a charged particle with a positive charge $q$ from $A$ to $B$, seek the work that the ...
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53 views

Difference between discharge tube and capacitor

I did search this on google but didn't get satisfactory results. Can you tell me difference between capacitor and discharge tube? "**Discharge tube has its gaseous medium at very low pressure but ...
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34 views

What is meant by homogeneous in $x$ in $n$'th degree?

I'm reading about classical mechanics by Goldstein, and in the section about Hamiltonian mechanics it is stated that in the expression: $$H(q,p,t)=\dot{q}_ip_i-L(q,\dot{q}, t)$$ the Lagrangian ...
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96 views

Complex numbers in physics [duplicate]

Can someone please explain the origin of complex numbers in physical values. For instance, denoting a plane wave with Euler's identity and also the complex relative permittivity? Thank you.
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53 views

What is a quantum system?

I heard that a wavefunction applies to a quantum system. But what is a quantum system? I am new to quantum mechanics, sorry for asking a basic question.
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The difference between exact solution and analytic solution

My mother tongue is not English so I am confused with the difference between exact solution and analytic solution. Are these the same?
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What is a free parameter?

Soft question here, but I was wondering just what exactly free parameters are? I have a murky understanding on the concept but I would much appreciate someone shedding some light on the matter. Is ...
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174 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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127 views

Why is the 1-dimensional wave equation called like that when it seems to be 2-dimensional?

The wave equation in one dimension traveling along a string is: $$ \frac{∂^2y}{∂x^2} = \frac1{v^2} \frac{∂^2y}{∂t^2} $$ but this equation has 3 variables $x, y,$ and $t$, shouldn't it be in 2 ...
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In particle physics, how should we call a model with several Higgs boson : Higgs multiplet?

In Higgs physics of the Standard Model, there is only one Higgs. The Higgs belong to a Higgs doublet. After electroweak symmmetry breaking, there is only one remaining Higgs, and 3 Goldstone bosons. ...
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What's the name for “middle” principal axis of inertia?

See this question for some context about the stability of rotation of a body around different axes. I am now trying to say that the rotation around the middle axis is very unstable, without using ...
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What does topologically stable mean?

I am working on an article about skyrmion manipulation and it is written that those particles are "topologically stable particle-like spin configurations that carry a characteristic topological charge ...
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76 views

Feynman screwjack problem

What is a thread? How does he know you need to turn the handle "around" 10 times? From where does the 126 inches come from? I thought Feynman explanations were easy... Let us now illustrate the ...
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58 views

Noun for particles that are quantumly entangled

What will we call particles that are in a "quantum entanglement" kind of relationship? not looking for examples (like thingamatrons can participate theoretically in quantum entanglement); rather the ...
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54 views

Fermat's Principle: no first-order change in time?

I was reading the chapter on Fermat's principle in the Feynman lecture series. The principle is stated along these lines: "The correct statement is the following: a ray going in a certain ...
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What is recessional nonlocality?

In laymen’s terms, what is recessional nonlocality? I understand recessional means to recede or retract away, and (correct me if I’m wrong) I understand locality has something to do with quantum ...
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130 views

What are $U(n)$ or $\mathbb{Z}_2$ quantum spin liquids?

Quantum spin liquid is a state of matter in which spins are correlated and fluctuate even at zero temperature. My question is about these terms in general. When we say that a state or a quasi-...
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146 views

What is a rigid wave function?

The London equations prior to BCS that describe superconductivity require assuming the wavefunction describing the superconducting pair of electrons to be rigid. I've been looking all over trying to ...
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60 views

Method of Dimensional analysis: What does “an expression of product type” mean?

I read in the book Concepts of Physics by HC Verma in the section of Limitations of Dimensional analysis that the method of dimensions cannot lead us to the correct expression sometimes if expression ...
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Area under a velocity graph

If I took the definite integral of a velocity graph from 0 to 10 seconds, the answer would be the change in position over those 10 seconds correct? I am told by my teacher the area is change in ...
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Inclusive jets and forward jets

In several studies of experimental particles physics, I find that a process distributions of a given observable are divided into categories such as "forward-jet", "inclusive-jet" and zero-jet". I can'...
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Name for the set Displacement, Velocity, Acceleration, etc

Is there a name for the set Displacement, Velocity, Acceleration, Jerk, etc? The only name I can think of is 'Derivatives of displacement (wrt time)' which is rather long.
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140 views

Is there a name for this dimensionless quantity?

I have an equation with the nondimensional number $\Delta P L / \sigma$. Here $\Delta P$ is a characteristic pressure drop, $L$ is a characterictic length, and $\sigma$ is a characteristic surface ...
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Is there a word for the availability of a gas, normalized for pressure?

As a bit of background of what I'm getting at, consider that for the purposes of humans breathing and getting oxygen into their blood, 20% oxygen at 1 atm is equivalent to 100% oxygen at .2 atm. ...
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1answer
401 views

Einstein solid degree of freedom

I was studying from Schroeder's thermal physics book. When it talks about Einstein solids it says that they have 2 degrees of freedom thus $U=NkT$ However, I thought when we talk about Einstein ...
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65 views

What is meant by “linear” in non-equilibrium thermodynamics?

I'm trying to learn a bit about non-equilibrium thermodynamics, and am currently reading de Groot and Mazur. In it, there is a quote right in the beginning, talking about the phenomenological ...
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131 views

Difference between time series and trajectory terminology

What is the difference between trajectory and time series? To me both seem the same thing. In the 3D diagram (cube picture on left of Fig.2 from the paper titled “Review and comparative evaluation of ...
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114 views

Why is particle physics called high energy physics? [duplicate]

The highest energy accelerator till date is the LHC which operates at an energy scale of perhaps 10-100 TeV. In SI units this is about $\sim 10^{-6}-10^{-5}$ Joule which is several orders of magnitude ...

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