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Jun
4
answered Turning points of particle
Jun
4
answered Can we assume black hole is just two big stars revolving around each other?
May
15
comment What is the length dimension in critical phenomena?
Hm, I had $\xi$ defined as $$\xi^2=\frac{\int_0^\infty r^2G(r)}{\int_0^\infty G(r)}$$ But anyway, I know the expression of the correlation function in the three regimes, I just fail to see why I should expect values that don't depend on the size of the system for dimensionless variables. Thank you for answering
May
15
comment What is the length dimension in critical phenomena?
@MengCheng I think it's the word length that confused me, sorry. For example the Binder cumulant as defined in the previous question ($\langle m^4\rangle/\langle m^2\rangle^2$) is dimensionless, why should it be better that $\xi/L$ to find the critical point?
May
15
comment What is the length dimension in critical phenomena?
@Danu Well, I know what a dimesionless variable is. I just don't know how that applies. If a quantity is dimensionless, then in a scale invariant system, it should not depend on size. Is that it? Why? And if so, should any dimensionless quantity I could build behave that way? For example, if the susceptibility goes like $\chi\sim L^{\gamma/\nu}$, then $\chi/L^{\gamma/\nu}$ behaves that way although it has dimensions.
May
15
asked What is the length dimension in critical phenomena?
May
15
comment How to interpret a null critical exponent?
@MengCheng Ok, thank you
May
15
comment How to interpret a null critical exponent?
And is there any deeper reason for it instead of being just because the $\log$ function diverges slower than any power?
May
15
asked How to interpret a null critical exponent?
May
9
answered Density of particles in hexagonal lattice
May
9
revised Density of particles in hexagonal lattice
edited title
May
9
asked Density of particles in hexagonal lattice
Apr
29
asked Sum in the reciprocal lattice
Feb
16
awarded  Organizer
Feb
15
answered Does light itself experience time dilation?
Feb
7
awarded  Citizen Patrol
Feb
4
comment How the torque/moment-of-force can be mathematically defined?
Yes it is, they are not being added, they are being multiplied. Do you have any trouble multiplying distance with the inverse of time to get a speed? This is the same thing.
Feb
4
comment How the torque/moment-of-force can be mathematically defined?
Well... you are not adding position and force which wouldn't make sense. You're multiplying them, which produces a new unit Newton*meter. Mathematically, they both belong to $\mathbb R^3$, so they belong to the same space and that product is perfetly well defined.
Jan
29
comment Why does choosing a time break covariance?
Some simple example would be greatly appreciated, I think that would trigger my understanding. Thank you for your answer by the way.
Jan
29
comment Why does choosing a time break covariance?
That is exactly my question, in which point of defining canonical momentum or legendre transforming the lagrangian do you fix a time? Couldn't you just define the momentum to be $\partial\mathcal L/\partial\dot\phi$, with the dot representing any parametrization of time in minkowsky space?