Recent content by graphking

Very gross understanding towards poynting, what is j and E vector?

I know my expression is bad, I should google it, but what do you say about bertrand thm?

so how to use? can't see they are relevant

right, integral in ##R^3-B_\epsilon(0)##, and use divergence thm if your are curious about the equation everypoint (specially point 0), that is Dirac delta, try to understand it as a functional like ##<\delta, \varphi>##, that is ## \int \limits_{R^3} \delta \varphi ##

can't see how to use Frobenius theorem, I think this is just a hard exercise. you can search in John lee, gtm218 for the true meaning of Frobenius theorem

Thank you all for more information from physics! I understand the real situation better. What I can provide is an interesting fact that gravity maybe fail to exist in a 2-dimension world, because it cannot be the form of r^-2, and due to bertrand theorem, if you want a force can make 2 point...

what is the situation here? if it's not rotating, the gravity formula is modified?

I have seen some of them, but I can't fully strctly understand the calculate using legendre polynomials. And as for the begining of all calculation base on small disturbing from sphere, I haven't found the proof of sphere in google, not so sure whether some journal has it

that is a new view to me, I only pretty sure it must be sphere when the object is convex, adding small part maybe not convex?

"bubbles are ball" is called isoperimetric problem in serious mathematic. In this topic, many essay were written. Here's my serious essay about "why earth ball", which has been rejected by arxiv and my mentors...... I would want to know if physicists are interest? I really think that is...

please teach me a good way to proof the isoperimetric problem in R^3

Using the lagrange multiplier is a way can only solve the isoperimetric problem in R^2, I show you the result you get in R^3: assuming the surface is z(x,y), with fixed boundary in XOY plane, then ##(z_x/(1+z^2_x+z^2_y)^{1/2})_x+(z_y/(1+z^2_x+z^2_y)^{1/2})_y \equiv -1/\lambda ##

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Why no one think of the assumption that time is R (real numbers)? Is this assumption reasonable? I saw some of you discussing 'motion', I think in Zeno's paradox he assumed the turtle and the man moving in a constant speed. Which is probably simple to define without the calculus. And besides...

No, because my GPA is low. My academic ability may not get the financial support.