Questions tagged [definition]
The definition tag is used in situations where the question is either about how some term or concept is defined or where the validity of an answer depends on a subtle definition of some term or concept used in the question.
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What is the difference between Born approximation and tree-level processes?
The answer to this question says that Born approximation is essentially equivalent to the tree-level. This can be seen from the Feynman-diagrammatic version of Born series discussed in many NRQM ...
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What exactly are cohesive and adhesive forces?
Are cohesive and adhesive forces defined only when at least one of the interacting materials is a fluid?
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On the definition of topological order
I am currently reading the "Quantum Information Meets Quantum Matter -- From Quantum Entanglement to Topological Phase in Many-Body Systems". I am trying to understand the proper definition ...
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What is the so-called momentum density? [duplicate]
What is the so-called momentum density? I am reading the paper by Pitaevskii, in which he stated that it is well-known. He studied the nonlinear Schroedinger equation, but it seems that the concepts ...
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Is displacement vector always the shortest path?
I read that the displacement vector of a particle is the shortest path between its initial and final positions since it's a straight line joining the two points, this holds true for me till a 2D ...
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Is there a practical distinction between functions of state and functionals in thermodynamics?
In thermodynamics, and more precisely when talking about continuous systems, some sources [1, 2] introduce functionals of state:
$$F[s(x), \dots]:=\int_VdV(x)f(s(x),\dots,x)$$
In order to derive ...
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What does Density really mean? [duplicate]
We say that density is mass per unit volume and if an object has high density that means it has more amount of matter contained per unit volume but as we know mass is not the amount of matter ...
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Definition of “quasi-locality” in Wilsonian RG scheme
I’m studying about the holographic RG with this paper.
In that paper they say Wilsonian action expects quasi locality, but I’m not sure what “quasi-locality" exactly means.
If quasi-locality ...
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How were angles measured in ancient times?
What is one degree (angle measurement)? I know that we calculate one second using atomic clock, one kilogram using Planck's constant, one meter using speed of light but how do we define one degree? If ...
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What is the definition of a conformal symmetry? [duplicate]
I have been very confused by this after some recent reading. So as far as I know, a conformal transformation (according to the definition in di Francesco et. al.'s book on CFT) is an active coordinate ...
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What are regular event horizons?
I am studying uniqueness theorems of Black Holes and I often see the word "regular event horizon" instead only event horizon. Many textbooks and literature do not define this term. Please ...
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Where does the four-vector potential $A^\mu$ originate?
Now the default answer to this may be, "It has no origin because it's a definition", but let me just try to justify my concern here.
On page 842, equation (22.91) of "Modern ...
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What exactly is a brane? [duplicate]
what exactly is a brane? i know that in order to get the equations of motion of a relativistic string by varying the Nambu-Goto action one has to impose a Neumann boundary condition and a Dirichlet ...
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Pressure sensors vs. piezoelectric sensors
In simple terms, what is the difference between pressure sensors and piezoelectric sensors?
I did some google search online and could not come to a good conclusion.
Say you make a 'sensor' in the lab ...
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What stationary charges exactly mean?
When learning about magnetic fields, it is said that stationary charges do not have any effects due to magnetic fields. So when explanations are given, is the spin of the charges not considered?
And ...
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