# All Questions

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### What is the difference between scale invariance and self-similarity?

I always thought that these two terms are some kind of synonyms, meaning that if you have a self-similar or scale invariant system, you can zoom in or out as you like and you will always see the same ...
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### Wigner characteristic function

I came across the "representation of a Gaussian state by its Wigner characteristic function". I don't know what Wigner characteristic function is and google results are not precise enough. Neither ...
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### Conservation of energy issue with pair creation/annihilation

Question: what is the energy balance in this situation? (Fig A) Two gamma rays collided and produced an electron/positron pair $(e-/e+)$. (Fig B) 1. because all particles are accelerating ...
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### Heisenberg Uncertainty Principle at a macroscopic level

At a macroscopic level, any physics interaction would require the two objects to be "measured" against each other, but what is what each macroscopic object perceives about the other one when it ...
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### Calculate/Estimate the fractal dimention of the logistic map using box counting

This is the logistic map:. It is a fractal, as some might know here. It has a Hausdorff fractal dimension of 0.538. Is it possible to calculate/measure its fractal dimension using the box counting ...
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### Is glass a liquid?

I was told by a condensed matter physicist that glass is a liquid with a very high viscosity (it would be more precise to say that it is a supercooled liquid). The example given was that in cathedral ...
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### Center of mass of a body on an incline

I am trying to reproduce a calculation by Carre et al. (1995) in which they calculate the shape of a droplet on an incline. My issue is in the derivation of the potential energy (essentially the ...
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### Geometrical Representation Grover algorithm

I am studying the Grover algorithm and in my and others lectures, I've come across this picture. If the dimension of the computational basis is greater than 2, why does the evolution algorithm ...
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### Tensor equations in General Relativity

In the context of general relativity it is often stated that one of the main purposes of tensors is that of making equations frame-independent. Question: why is this true? I'm looking for a ...
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### Planet in which satellite(moon) and star(sun) appear together once a year

With a hypothetical system, where the moon would be always on the opposite side of the planet than the sun, in a way that the moon would only be visible at night on the planet. I don't know if this ...
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### Why Quantum correlation is not uniform in this diagram?

Following diagram is from a Wikipedia article which shows Quantum Correlation for local hidden variables and Quantum Mechanics and experiments confirm Quantum Mechanics predictions. My question is ...
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### Is it possible to detect subjective decoherence? If yes, how?

In his paper from 1994 Thomas Breuer describes a phenomenon of subjective decoherence (p. 43). I wonder whether it can be measured, and if yes, how. I also wonder whether it would allow to create an ...
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### The Univere's mass-energy and uncertainty

A virtual creation with total mass-energy = $E$ is allowed as long as that virtual creation doesn’t last longer than $E/h$. Can the uncertainty principle also be used to estimate the mass-energy in ...
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### Can a single molecule have a temperature?

A show on the weather channel said that as a water molecule ascends in the atmosphere it cools. Does it make sense to talk about the temperature of a single molecule?
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### Anyons as particles?

I'm trying to understand the basics of anyons physics. I understand there is neither a Fock space they live in (because Fock is just the space of (anti-)symmetrized tensor product state, see e.g. ...
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### How the “Standard Model” get that name? [closed]

I want to know how the Standard Model theory got such "generic" name?
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### Using the Normalization Condition with Wavefunction

I'm very confused with this problem and I was looking for some guidance. $$\psi(x) = Ae^{ikx}e^{-x^2/2a^2}$$ Use the normalization condition to find A. So I understand that you use the normalization ...
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### Finding the force of an object? [closed]

Sorry if my initial question was seen as a "homework question" but I don't really know how to go about asking this type of question. I have a feeling I have to use Newtons law but there is no ...
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### Hall conductivity from Kubo: Bulk or edge?

Using the Kubo formula, Thouless, Kohmoto, Nightingale, and den Nijs (TKNN, PRL 49 405-408 (1982)), proved that upon summing all the contributions of the filled states of an insulator, the Hall ...
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### Boundary Condition for Perfect Conductor in Uniform Magnetic Field

When I was studying the perfect conductor scattering (Section 10.1) in Jackson's book, I was confused by the calculation for magnetic dipole induced by the incident wave. He simply said like "set the ...
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### Current in AC circuit

The problem is to find the current on the capacitor. $I''$ should be correct, but I don't know how to construct the formula for $I'$. I managed to get the value for $I_c$ using Thevenin and Norton ...
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### How to derive the expression for Bose-Einstein distribution variance?

Can anyone point me to a derivation of this expression? $n_s$ is the number of bosons in a state.
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### Hexadecapole potential using point particles?

We can get monopole $1/r$, dipole $1/r^2$, quadrupole $1/r^3$ and octupole $1/r^4$ potential falloff by placing opposite point charges at the corners of a point, line, square and cube, respectively. ...
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### Tensor fields on space-time

I'm reading landau electrodynamics . For the investigation of the dynamics of a charged particle in an electromagnetic field , the author introduces a four vector potential field on spacetime . The ...