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

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Why can´t we call the energy released after the annihilation of a particle and its antiparticle `pure` energy? [on hold]

As a particle and its antiparticle annihilate each other a huge amount of energy is released, and no mass is left. This energy always comes in the form of force mediating particles (photons, gluons). ...
0
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0answers
26 views

Are general coordinate transformations and diffeomorphisms the same? [duplicate]

Infinitesimal diffeomorphisms $x{}^\mu \rightarrow x{}^\mu + \xi{}^\mu$ (with $\xi{}^\mu \ll 1$) change geometric objects by means of the Lie derivative, that is, $X \rightarrow X + \mathcal{L}_\xi \, ...
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0answers
18 views

What is the name of basis states of bulk k.p Hamiltonian?

A k.p Hamiltonian for a bulk material can be represented by 8x8 matrix in basis of $|S\uparrow\rangle$, $|S\downarrow\rangle$, $|X\uparrow\rangle$, $|Y\uparrow\rangle$, $|Z\uparrow\rangle$, ...
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1answer
40 views

What kind of damping is this $F = -ax|x'|$?

From Applied Mathematics by Logan: A mass hanging on a spring is <...> governed by $$mx'' = -ax|x'| - kx$$ where $-ax|x'|$ is a nonlinear damping force. I looked up "nonlinear damping" ...
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1answer
32 views

Do we mean with 'pure energy' the force-carrying particles? [on hold]

I often read, hear and talk about pure energy. What is meant by this? Does pure energy consists of the forces between matter, or the force mediating particles, like the massless photons and gluon? I ...
6
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1answer
282 views

What is meant by the term “value” of a scalar quantum field?

During the slow roll of a scalar field, the scalar field is changing its value over time. But what is meant by the term "value" of a scalar field? Since the scalar field is quantized, I don't ...
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1answer
16 views

Which of these values has larger gravitational potential? [closed]

As an example: $-65\ \mathrm{MJ/kg}$ or $-20\ \mathrm{MJ/kg}$? I understand that all gravitational potential energy is negative, and that obviously the larger value is $-20$, however I don't know if ...
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2answers
78 views

Is electromotive force really a force? [duplicate]

As far the definition goes emf of electromotive force is basically potential difference. It even has dimensions of potential. Then why is it called a force?
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2answers
38 views

Gravitation and gravity

Are gravity and gravitation the same thing? Actually I have 2 teachers at my school. One of the said that gravitation is the force of attraction between any two bodies in the universe due to their ...
0
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1answer
53 views

Is there a difference between the adjoint and conjugate?

Is there a difference between the adjoint and conjugate? I have recently started some work for a quantum field theory module and I'm wondering if there is a difference between the adjoint or conjugate ...
1
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0answers
53 views

Found a weird piece of lab equipment?

My physics teacher found a weird piece of equipment in his classroom that was dated to the 70's. The item in question has no identifying marker except for "Carolina Biological". He has contacted the ...
0
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1answer
42 views

What is the difference between habitable and Goldilocks zone?

If I am right, Habitable Zone means that a planet is on such a distance from its Star which makes it good candidate for supporting some sort of life. But then what is Goldilocks zone and how is it ...
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3answers
35 views

EMF or terminal voltage?

I have a doubt that is: What does this statement mean: "a 6 V battery". Does this mean that the EMF of the battery is 6 V or the terminal voltage of the battery is 6 V? If the battery has internal ...
0
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3answers
49 views

What does the “moment” in the moment of force or the moment of inertia refer to? [duplicate]

According to the Merriam Webster dictionary: Moment - a very short period of time Does the word "moment" in quantities like the moment of force or moment of inertia refer to this colloquial ...
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0answers
17 views

Slowly Varying Functions for Adiabatic Invariants - The Same as Karamata's?

In section 49 (and 50) of Landau and Lifschitz's "Classical Mechanics", adiabatic invariants are discussed, which are related to functions which vary adiabatically or "slowly" with time. Admittedly ...
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0answers
13 views

Equivalent of the word “Attitude” for the other three DoFs [closed]

When discussing the physical state of a thing (e.g. a satellite), you can refer to its attitude state (which, to me, consists of its attitude and its derivatives/rates) and its.... non-attitude state ...
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0answers
21 views

Position, velocity, acceleration, jolt, and [duplicate]

I am familiar with the fact that $\displaystyle{\frac{dx}{dt}}=v$, $\displaystyle{\frac{dv}{dt} =a}$, and $\displaystyle{\frac{da}{dt}=J}$ where $J$ denotes the 'jolt', or jerk. Are further ...
3
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1answer
299 views

What is the meaning of “moment”?

What is the meaning of moment? I'm little confused about the word as there are some terms like moment of momentum, moment of mass, moment of force, etc. I want to know what exactly is meant by the ...
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2answers
280 views

What is meant by the term “completeness relation”

From my humble (physicist) mathematics training, I have a vague notion of what a Hilbert space actually is mathematically, i.e. an inner product space that is complete, with completeness in this sense ...
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1answer
32 views

What is the word describing the pairs: temperature and energy, chemical potential and particle number?

I keep forgetting the word describing the pairs of coupled quantities in stat. mech. e.g. inverse temperature $\beta$ and internal energy $E$ or chemical potential $\mu$ and particle number $N$. I ...
1
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1answer
19 views

Semiconductor nanostructure and heterostructure

What is the difference between compositional superlattice and doping superlattice?
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0answers
14 views

Inertial force of fluids [duplicate]

Reynold's number is the ratio of inertial force to viscous force.I also know the definition of inertial force.but where does a fluid get this force from?what are the factors responsible for this ...
0
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1answer
66 views

What is gate symmetry?

I just read this interesting interview with Frank Wilczek and he talks a couple of times about gate symmetry, without ever defining the term. This isn't a term I've come across, and google throws up ...
0
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1answer
41 views

Difference between sudden force and impulsive force? [duplicate]

What is the difference between a sudden force which continues to act on the body, and an impulsive force? What would be respective speeds of the body just after time= 0?
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0answers
34 views

What is the general definition of a quench?

I've seen the term "quench" used in many different contexts. It's easy to understand the meaning when the context has a simple physical analogue, such as lowering the temperature of a system to cause ...
1
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1answer
40 views

What is $bfr$ in this expression?

I am reading 'Fundamentals of Quantum Mechanics' by Sakir Erokoc and came across this expression in relation to transition probabilities: $$\vec p=e \langle \psi_b |bfr|\psi_a \rangle$$ Which can be ...
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26 views

Why are photonics fibers called band gap fiber?

Why are photonics fibers called band gap fibers? Do the photonic fibers guide light inside the band gap or outside? What creates the band structure?
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1answer
34 views

Symbol $p^{0}$ of particle [closed]

This is a very trivial question, but I cannot seem to find the answer anywhere in a textbook or the internet. My question is, what particle is represented by this symbol? $$p^{0}$$
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2answers
47 views

Definition of a ray?

The typical definition of a ray and the one that I was initially taught was that a ray was a line perpendicular to the wave front. However, when reading up on birefringence it seems as though there ...
4
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1answer
203 views

Regular solution vs irregular solution

My Quantum Mechanics textbook (John S. Townsend's A Modern Approach to Quantum Mechanics) mentions regular solutions and irregular solutions. It claims that regular solutions (at the origin) to the ...
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0answers
25 views

What does 'fully excited' actually mean?

In statistical mechanics you often hear the phrases such as 'when the degrees of freedom are fully excited then....'. An example would be the validity of the equipartition theorem. But what is the ...
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1answer
22 views

Bifundamental representations [closed]

Can someone give me explicit examples (in matrix form) of bifundamental representations? Illustrative would be for instance: a) SU(3) x SU(2) b) SO(4) x U(1) c) E6 x U(1) but other you may have ready ...
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34 views

Terminology for 'inferring the current state of a quantum system as it evolves and gets measured out of your control'

Suppose I hand you a quantum computer in an unknown state, but running a known program. You know the program and which part of the program is currently being executed. The program tells the computer ...
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1answer
36 views

Spectroscopy, interferometry and …?

Consider the case of a Michelson 'Interferometer', from what I have read: If you measure the output as a function of mirror separation that's interferometry. If you measure the output as a function ...
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3answers
151 views

“Randomness” versus “uncertainty”

Highly rated PhysicsSE contributor @CuriousOne regularly makes the following claim about quantum mechanics (e.g. here): There is no randomness in quantum mechanics, there is only uncertainty. I ...
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0answers
30 views

Ampere right hand screw rule or Maxwell screw rule is the more correct name of the right hand grip rule?

Wikipedia states ampere right hand screw rule Some textbooks state maxwell screw rule Which one is the more correct name in representing the (colloquial) Right hand grip rule?
4
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1answer
291 views

What's the difference between the diffeomorphism invariance and reparametrization invariance?

Can somebody tell me what's the difference between the diffeomorphism invariance and reparametrization invariance?
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1answer
41 views

Speed of light in vacuum in special relativity

In special relativity, the speed of visible light is defined as a constant. But visible light is only a small part of the electromagnetism field. So why?
0
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1answer
41 views

Physical meaning of Phase matching

Can anyone help me understand what exactly is meant by phase matching? I want to know whether momentum can be conserved only under phase matching condition or phase matching condition ensures momentum ...
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2answers
46 views

Difference between scattering and refraction?

I while back I learnt that when light is incident on a dipole the dipole will scatter the light, and when it is incident on a material of a different refractive index then the light refracts. From the ...
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0answers
40 views

Are there any symbols left? [closed]

I have looked through most of the symbols used in physics and math. It seems like there are none left in the alphabet and the greek alphabet. Are we screwed if we find a new constant? Edit: How do ...
0
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3answers
59 views

What are the units for tenths-of-a-millimeter?

I'm seeing all kinds of mixed representations for what is a SI unit that doesn't seem to be easily representable with the Latin prefixes. Generally I stick one of the nominal ones and scale my plots ...
0
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1answer
14 views

Does the Schottky Barrier only happen at Metal Semiconductor Interfaces?

Most references that I have come across refer to the Schottky Barrier in the setting of Metal and Semiconductor Interface. Would it be correct to use the term Schottky Barrier to refer to the mismatch ...
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0answers
18 views

Water maintains equal level in connected vessels. What is this property called? [closed]

How water maintains same level in connected tubes or vessels? Is this a specific property?
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2answers
3k views

Why is the cut off mass for massive stars 8 solar masses? Why can't it be 10-11 solar masses or so?

I know that stars having a mass greater than or equal to 8 solar masses are termed "massive stars". But why is the cut-off 8 solar masses?
7
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2answers
430 views

What is the difference between “additive” quantum numbers and “multiplicative” quantum numbers?

What is the difference between "additive" quantum numbers and "multiplicative" quantum numbers? I think that this may have something to do with P and C Symmetry groups, but I may be mistaken. I’m ...
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1answer
69 views

What is the difference between the Lorentz force and the ponderomotive force? [closed]

I understand that Lorentz force is due to motion of moving charged particle in a magnetic field, and I imagine that ponderomotive force is mechanical version analogy to a person surfing on a wave ...
0
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1answer
45 views

What is the meaning of 'physical gauge'?

What does it mean for a gauge to be a physical gauge in your gauge choice of the theory, and why is it called the "physical gauge"?
5
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1answer
103 views

What do we exactly mean by a “topological object” in physics?

I have been working on topological defects like monopoles, etc. for some time. One think that I have not been able to understand is the physical meaning of the phrase "topological object". I have ...
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2answers
446 views

What is “Dynamical phase transition”?

What is "Dynamical phase transition"? It is a fancy notion now. But what exactly does it mean? What is the difference between it and the conventional phase transition?