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  • 165 votes cast
Mar
10
comment The central limit theorem from a path integral?
I agree it is not really a physics question. But it seems to me that in general physicists know much more about functional integration and path integrals than mathematicians, so I though I ask the question here.
Mar
10
comment Are path integrals integrals with countable or uncountable infinite dimensions?
So path integrals are understood as having uncountable/continuous infinite dimensions?
Feb
24
comment Why a day is divided by 12/24 hours? Why the number 12?
In fact 12 is the fifth en.wikipedia.org/wiki/Highly_composite_number.
Feb
11
comment Speed of gravity within a mass
Does this mean that refraction of gravitational waves by matter is also not detectable?
Feb
8
comment What is the opposite of quantization?
@CuriousOne: Why do you not write another answer then?
Feb
8
comment What is the opposite of quantization?
Bohr said, that the angular momentum should be multiples of Planck's constant: $L = n\hbar$. So if $L$ is taken as a constant taking the quantum number $n \rightarrow \infty$ basically implies $\hbar \rightarrow 0$ . Doesn't that mean that both statements are basically equivalent?
Feb
7
comment What is the point of complex fields in classical field theory?
That you for the link to the notes of Sidney Coleman. These are really helpful.
Feb
7
comment What is polarisation, spin, helicity, chirality and parity?
What about polarization?
Feb
7
comment Does a set of eigenvalues in QM correspond to a random variable in statistics?
Sorry, I overlooked this clear statement in the wall of text by Moretti: "As a matter of fact, a maximal set of pairwise commuting projectors has formal properties identical to those of classical logic: is a Boolean σ-algebra."
Feb
6
comment Does a set of eigenvalues in QM correspond to a random variable in statistics?
But ValterMoretti is talking about measurements of two observables (which as I understand don't commute in QM in general). That is not what I'm asking about. My question is much simpler and only concerns the measurement of a single observable.
Feb
6
comment Does a set of eigenvalues in QM correspond to a random variable in statistics?
The term "eigenvalue" does not appear in the answer of ValterMoretti you link to, so I think my question is different.
Feb
1
comment Is what statisticians call a “random variable” what physicists call an “observable” in QM?
Terence Tao seems to share my view "...and quantum mechanics (with physical observables taking the role of random variables, and their expected value on a given quantum state being the expectation)" (terrytao.wordpress.com/2010/02/10/245a-notes-5-free-probability)
Feb
1
comment Is what statisticians call a “random variable” what physicists call an “observable” in QM?
That is interesting. Can you put your statement about four tuples of binary random variables into a mathematical form?
Jan
29
comment What is the point of complex fields in classical field theory?
@Numrok But isn't a set of two real scalars a vector? The two scalars also have the same units and it is often said, that complex numbers can be represented as vectors.
Jan
29
comment What is the point of complex fields in classical field theory?
@Numrok I'm not sure about that point, too. The idea is that a complex number is by definition a en.wikipedia.org/wiki/Scalar_(physics) quantity, so invariant under coordinate transformation. But a vector of two real quantities is not a scalar. So it is not invariant under coordinate transformations.
Jan
22
comment Why don't antiparticles have antispin?
@ACuriousMind: Wouldn't a change in P (=parity?) imply spinning backwards?
Jan
14
comment Why is the Fourier transform more useful than the Hartley transform in physics?
@Daniel Sank: Thank you. Actually I was expecting somebody to say something along the line that a optical lens performs a Fourier transformation and not(?) a Hartley transformation, and that is why Fourier is more "physical". But your edit is very interesting, too.
Jan
12
comment Why is the Fourier transform more useful than the Hartley transform in physics?
I would love if someone could address this part of the question: "Are their any properties that make the Fourier transformation more "physical"?" .
Jan
12
comment Why is the Fourier transform more useful than the Hartley transform in physics?
@DanielSank I know that hermitian means, that the operator has real eigenvalues. What confuses me is that an operator involving the imaginary unit like $i (d/dt)$ can in fact have real eigenvalues. But maybe this leads to far away from the original question. Maybe I ask another question about this. Thank you.
Jan
11
comment Why is the Fourier transform more useful than the Hartley transform in physics?
@DanielSank Isn't the eigenvector of $(d/dt)$ simply the real exponential function $e^{x}$ ? Why is the exponential function with a complex argument be used for the Fourier transformation?