Use this for questions relating to the proper use of physics terminology or nomenclature.
4
votes
1answer
3k views
What exactly is the difference between advection and convection?
After reading Wikipedia articles on advection and convection, I still cannot determine whether there is a consensus on a difference between these two terms.
Sometimes, the term convection seems to ...
0
votes
2answers
133 views
When to use $f$ and when $\nu$ signifying frequency?
When to use $f$ and when $\nu$ signifying frequency? I guess that when you mean frequency of electromagnetic wave, you use $\nu$, and $f$ otherwise?
3
votes
2answers
662 views
What is a non linear $\sigma$ model?
What exactly is a non linear $\sigma$ model? In many books one can view many different types of non linear $\sigma$ models but I don't understand what is the link between all of them and why it is ...
0
votes
1answer
345 views
Wave packets v.s. wave trains
Could someone please explain the difference between a wave packet and a wave train? I have rummaged around online but have not been able to find a definitive definition.
4
votes
3answers
271 views
Are quantum mechanics and quantum physics the same field?
What is the difference between quantum mechanics and quantum physics?
9
votes
4answers
262 views
Is the Lagrangian of a quantum field really a 'functional'?
Weinberg says, page 299, The quantum theory of fields, Vol 1, that
The Lagrangian is, in general, a functional $L[\Psi(t),\dot{\Psi}(t)$], of a set of generic fields $\Psi[x,t]$ and their time ...
7
votes
3answers
5k views
What exactly is the difference between radiation and convection?
Okay, so everywhere I've read, I hear the main difference is the requirement of a medium. But for example, if you take the case of heat 'radiating' from a red-hot iron, isn't that actually convection ...
1
vote
1answer
397 views
Definition of Free Electrons and Mobile Charges?
Could someone please give me a good definition of the following electric terms? Despite what searching I have done, I have not come across a definition that I have found clear for me to understand:
...
-2
votes
1answer
554 views
Can I just ask what these pulleys-and-constant-lengths problems are called?
I am not sure if this question is appropriate for this section, but I just want to know what these type of questions are called and when do physics majors learn them?
These problems have to do with ...
1
vote
1answer
240 views
Common Variables in Quantum Mechanics
I am an eighth grader (please remember this!!!) in need of some guidance in my school project on Quantum Mechanics, Theory, and Logic. I am attempting the create a graph of the Schrödinger Equation ...
1
vote
2answers
321 views
Does a cycle (in Simple Harmonic Motion) have to equal 2π?
So, I search for the definition of cycle and I get this in Wikipedia:
A turn is a unit of angle measurement equal to 360° or 2π radians (or ...). A turn is also referred to as a revolution or ...
5
votes
2answers
226 views
What's the difference between “evidence of a new particle” and “discovery of a new particle”?
Today’s exciting press release from Tevatron on the Higgs boson keeps its head cool and say that physicists saw a “hint” of the Higgs boson because the signal is barely above the two-sigma level. In ...
1
vote
0answers
72 views
Is putting a charged balloon up to a neutral wall polarization AND temporary induction, or just polarization?
Is putting a balloon that is charged up against a wall and having it stick polarization AND charging by temporary induction, or just polarization?
4
votes
3answers
177 views
What is a “measure equation” as mentioned by this TeX Users Group guide?
In this TeX Users Group (TUG) document, Typesetting mathematics for science and technology according to ISO 31/XI by Claudio Beccari, the author makes various typesetting recommendations including:
...
0
votes
1answer
277 views
Energy versus free-energy diagram
Energy versus free energy diagram. I haven't been able to find an adequate definition of these two terms in relation to each other. Could someone point me in the right direction, please?
From Borrell ...
4
votes
2answers
2k views
Convective and Diffusive terms in Navier Stokes Equations
My question has 2 parts:
I just followed the derivation of Navier Stokes (for Control Volume CFD analysis) and was able to understand most parts. However, the book I use (by Versteeg) does not ...
1
vote
0answers
263 views
What is a boundary condition for capacitors/dielectrics?
I am extremely confused about what boundary conditions are. One minute ago I was solving easy capacitor questions and the next minute I am being asked boundary condition questions and there is no such ...
2
votes
2answers
3k views
Are all metals good conductor of electricity?
I am writing an article for kids, which is on conductors and insulators of electricity.
If I make a statement that "All metals are electrical conductors and all non-metals are electrical insulators" ...
3
votes
1answer
217 views
What is “charge discreteness”?
I assume it is some kind of quantity. Google only made things more confusing.
I get that it has something to do with circuits.
I also get what a discrete charge is. In fact, I thought charges ...
2
votes
2answers
252 views
What does physics study?
Wikipedia definition: Physics (from Ancient Greek: φύσις physis "nature") is a natural science that involves the study of matter[1] and its motion through spacetime, along with related concepts such ...
2
votes
1answer
135 views
What is the origin of the naming convention for position functions?
In physics, position as a function of time is generally called d(t) or s(t). Using "d" is pretty intuitive, however I haven't ...
0
votes
0answers
112 views
What is the electric field part of an EM wave? Radiation field or the induction field?
Look at this image:
I wonder if the electric field is from the induction field from a vibrating electron or the radiation field? If it is from the radiation field, as I suppose, than can someone ...
5
votes
2answers
106 views
What is it called when a fluid will “jump” to grab onto an object that comes very close?
I'm doing an experiment where I bring a probe very close to a well full of fluid and then very slowly lower it to obtain some force deformation values. The material behaves very much like a fluid and ...
3
votes
3answers
827 views
What's the difference between “boundary value problems” and “initial value problems”?
Mathematically speaking, is there any essential difference between initial value problems and boundary value problems?
The specification of the values of a function $f$ and the "velocities" ...
1
vote
1answer
68 views
Looking for the name of a particular device [closed]
Please move this if it's not in the right location.
I'm looking for the name of a device that I frequently see in many scenarios, specifically that of an office/library which can be described as ...
0
votes
2answers
148 views
Identifying hue, brightness and chroma of color and reaction time
If someone knows how identify hue, brightness, and chroma of color, please let me know.
I am a PhD student at Educational Linguistics UNM.
3
votes
1answer
183 views
What are Low-lying energy levels?
I am reading about some canonical transformations of the Hamiltonian (of a system consisting of an electron interacting with an ionic lattice) due to Tomanaga and Lee, Low and Pines. One of the ...
3
votes
1answer
164 views
What's a pseudo-rotation?
I'm sorry for this lexical, probably extremely elementary, question. But what is a pseudo-rotation? I just read this term for the first time, in the beginning of the 4th chapter book of CFT by Di ...
15
votes
1answer
1k views
Differentiating Propagator, Greens function, Correlation function, etc
For the following quantities respectively, could someone write down the common definitions, their meaning, the field of study in which one would typically find these under their actual name, and most ...
1
vote
1answer
81 views
Terminology question about energy
I'm looking for the appropriate term to use for what gets "used up" as potential energy is converted to heat and work. For example, some of the the energy in solar radiation is converted by ...
13
votes
4answers
2k views
Are matrices and second rank tensors the same thing?
Tensors are mathematical objects that are needed in physics to define certain quantities. I have a couple of questions regarding them that need to be clarified:
1-Are matrices and second rank tensors ...
0
votes
3answers
144 views
Equation $H(q,p)=E$ is the equation of motion or energy-conservation law?
I do not completely understand, why do we consider Hamilton–Jacobi equation $H(q,p)=E$ as equation of motion, whereas it is looks like energy-conservation law?
2
votes
1answer
233 views
How does one pronounce this particle's name?
How would you read the following particles' names in a conversation in English? I am looking for some "proper" way of doing it. Say, imagine you are reading a technical description in a semi-formal ...
1
vote
1answer
105 views
A terminological question about work and energy
Work is force applied over distance. Is it also reasonable to say that work is (the same thing as) the transfer of energy?
When work is done, the equivalent energy is transferred. But if energy is ...
2
votes
3answers
271 views
Definition of Fluctuations and Perturbations
The terms fluctuations and perturbations are frequently used in physics with different meanings. But they are confusing. Both terms seems to be same. Is there any one who can explain lucidly these ...
2
votes
1answer
177 views
Why is a gaussian fixed point called gaussian?
I know what a gaussian fixed point is, and I did read the wikipedia entry, but it wasn't helpful. It says because the probability distribution is gaussian, but what probability distribution?
0
votes
3answers
225 views
Is $f=ma$ an identity?
In his The Principles of Natural Knowledge, Alfred North Whitehead writes that famous $f=ma$ is an identity:
It has been popular to define force as the product of mass and
acceleration. The ...
2
votes
3answers
354 views
Opposite of Cryogenics
Cryogenics is related to very low temperatures, so, what is the term when referring to very high temperatures?
2
votes
1answer
968 views
What is “Quantum Levitation”?
I just found this video Controlled Quantum Levitation on a WipeOut Track
and I'm having a hard time finding the term "Quantum Levitation" used except in reference to the video.
What is the proper ...
1
vote
2answers
136 views
What will happen if we use a speed greater than light speed and find a body'motion and energy relative to it?
In Einstein's papers, he used light speed as a reference speed. What if we use a greater finite speed and do the same calculations. Won't this greater speed then be the limit.
2
votes
1answer
171 views
Why are the quarks so named?
Quarks have a variety of names (or flavours):
Up
Down
Strange
Charm
Bottom or Beauty
Top or Truth
Why do they have such odd names?
3
votes
2answers
300 views
What is a single word that describes the idea of the second time derivative of energy?
I think about position, its time derivative speed, and its second time derivative, acceleration. I would like to identify a single word that can be used as a handle for the second time derivative of ...
5
votes
1answer
57 views
Is there an established standard for naming exoplanets?
I understand that exoplanets are named by adding a lowercase letter to the a designation of the planet's parent star or stellar system, beginning with 'b' (the star itself is 'a') in order of ...
0
votes
1answer
101 views
Is reflection just a particular case of scattering?
I was talking to a colleague about optical scattering from a metallic nanoparticle, and we had a very simple doubt. If you have a particle that's small compared to the illuminated area, you can use ...
2
votes
3answers
412 views
what is it called: box potential with one infinite wall
The finite square well and the infinite square well problem are well known, however is there a reason that there is almost no reference to the one sided infinite square well?
Consider a particle ...
9
votes
3answers
451 views
“Slightly off-shell”?
I'm not new to QFT, yet there are some matters which are quite puzzling to me. I often come across the statement that real particles (the ones we actually measure in experiments, not virtual ones) are ...
2
votes
1answer
409 views
In layman's terms, what is a quantum fluctuation?
What causes it and how does it occur? If you do post some mathematics, please explain what each term means too please.
2
votes
1answer
180 views
What is deep Fresnel region?
If I understand correctly, it has something to do with autocorrelation function, but can someone give me a definition or exact explanation?
In case of scattering, if you wish to analyze pattern with ...
1
vote
1answer
97 views
Reality constraint
What is the "definition" of a reality constraint and why is it called that way?
(I mean how it is used for example in quantum field theory and string theory)
2
votes
2answers
2k views
What's the difference between constitutive laws and governing equations?
I'm studying about the finite element method in a class but I don't come from a civil engineering background. Anyways, it hasn't been made clear to me what the difference between constitutive laws and ...
