Tagged Questions
0
votes
0answers
190 views
How is the term “Born level” usually defined?
How is the term "Born level" usually defined, e.g. in talking about the $pp\to Z/\gamma^*\to e^+e^-$ cross section at Born level?
1
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0answers
65 views
Motivation For Definitions [closed]
I noticed in my physics textbook that we define certain relationships to be true. I can see how this is considerably helpful in deriving other relationships from these definitions; for instance, take ...
3
votes
3answers
190 views
What is a “Center Of Mass” issue of a Gorillapod?
I read somewhere that a Gorillapod may have "Center Of Mass" issues when used with the long lenses.
So, I wish to understand what is a "Center Of Mass" issue?
I have to clarify that I am NOT a ...
0
votes
3answers
2k views
Difference b/w Kinetics & Kinematics w/concrete example
(I know whether I understand this or not doesn't matter much to my work & study but am just curious.)
I still can't differentiate in my head kinetics and kinematics (similar thread is found but ...
3
votes
2answers
660 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.
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:
...
1
vote
1answer
239 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
320 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 ...
0
votes
1answer
276 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 ...
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
216 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 ...
3
votes
3answers
823 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" ...
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 ...
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 ...
2
votes
1answer
403 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.
1
vote
1answer
96 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)
1
vote
2answers
3k 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 ...
13
votes
7answers
1k views
What is a general definition of impedance?
Impedance is a concept that shows up in any area of physics concerning waves. In transmission lines, impedance is the ratio of voltage to current. In optics, index of refraction plays a role similar ...
