Diffusion equation in d- dimension

AI Thread Summary
The discussion explores the concept of determining the fractional dimension 'd' of a surface or volume through the simulation of a diffusion process, represented by the equation ∂φ/∂t = DΔφ. It highlights that the diffusion behavior varies significantly with different values of 'd'. The solution for an instantaneous localized source in d-dimensional infinite media is provided, emphasizing its dependence on the diffusion coefficient D and the distance from the source. The conversation raises the intriguing question of whether physical methods could be employed to ascertain the dimensionality of surfaces or curves. Ultimately, it suggests that the dimension of space may have tangible physical implications.
mhill
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i know that idea would seem a bit weird but,

let us suppose we have a surface or volume in d- dimension, here d can be any real number (fractional dimension) the question is that we do not know what value 'd' is

\frac{\partial \phi}{\partial t} = D\,\Delta \phi

D is a diffusion (constant) coefficient and 'nabla' is the Laplacian in d- dimension.

my question is if we performed a simulation of a 'diffusion process' could we get the value of 'd' , in other words, depending the dimension of space the diffusion process is completely different.
 
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The solution for an instantaneous localized source in d-dimensional infinite media is

C(r,t)=\frac{N}{(4\pi D t)^{d/2}}\exp({\frac{-r^2}{4Dt}})

(from Baluffi's Kinetics of Materials). N is the total amount of material initially at the source, and r is the distance from the source. I've never seen it used for fractional values of d, but the idea is intriguing.
 
thanks Mapes, the idea is 'does the dimension of space have physical consequences ? ' for example i was thinking if we could determine what dimension a surface, curve would have using physical methods. :)
 
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