Recent content by parsifal

Well, I don't have a clue on where to put this, but I'll go with this because solitons are a physical phenomenom, too. But I'll guess this is a wrong place for this anyway, so I apologize in advance. Anyway, could somebody help me understand the box-ball soliton system (soliton, specifically...

No answers. It's not my intention to be impatient, however. Instead, I was wondering if this whole "equivalency of graphs" is not as widely known as I though. My friend majoring in math has never heard of it, and it was actually presented to me on a physics course (not that this is a proof of...

Homework Statement Two graphs defined for a two dimensional torus: f_1(t) = (\frac{1}{\sqrt{2}}(a\ +\ b\ sin\ t),\frac{1}{\sqrt{2}}(a\ +\ b\ sin\ t),b\ cos\ t),\ t \in (-\frac{\pi}{2},\frac{\pi}{2}) f_2(t) = (a\ cos(t+\frac{\pi}{4}),a\ sin(t+\frac{\pi}{4}),b),\ t \in...

The task is to find the remainder of the equation: \frac{18^2+2^{100}}{11} Now I know that if a \equiv b\ (mod\ m),\ c \equiv d\ (mod\ m) \Rightarrow a + c \equiv b +d\ (mod\ m) and ac \equiv bd\ (mod\ m) so 18^2 \equiv b\ (mod\ 11) \Rightarrow \frac{18^2}{11}=29.454545... \Rightarrow...

I've got some difficulties trying to understand the equation of state derived from Friedmann equations. I'd greatly appreciate it if someone walked me through this. Now if the equation of state is stated as: \Large \dot{\rho}+(3\rho +p)\frac{\dot{R}}{R}=0 \ \ |p=\omega \rho Then (in the case...

I guess I was trying to do it the hard way, for some unclear reason. I didn't understand that the solution you suggested would do. Thanks for the answer!

I need to write Schwarzschild Metric, that is in spherical coordinates, into the form that has the metric tensor. Now, if the first the term of the metric is: \Large (ds)^2=f(r)c^2dt^2-... and x0=ct, then the first component gij of the metric tensor g is supposed to be: \Large...

Oh, of course. Many thanks. However, I fail to understand the solution. Why is the area of the whole sphere around the electrode taken into the computation? I mean: if an electron tries to get from point a on the surface of the electrode to point b somewhere in the ground, what does this have...

I'm not sure of the proper term here, but I'd guess it is either earth, ground or grounding resistance. The task is to compute this grounding resistance for a sphere electrode (radius a) in a ground (conductivity sigma). The definition given for grounding resistance "between the surface of the...

Ok, I think I can carry on from that. Thank you!

I'm trying to solve y, so I have to solve z in terms of x first and then substitute it in the equation y=z*x^2.

y' = 2y/x + x cos (y/x^2), with y=z*x^2 => y' = 2zx + x cos z and y=z*x^2 => y' = 2zx + x^2 * dz/dx So that leaves x^2 * dz/dx = x cos z => dz/cos z = dx/x I integrate both sides so that: sec z + tan z = x + C But I don't have a clue on how to get past that point. Should I start...

I don't know if this should be posted here, and I doubt if anyone can actually write anything genuinely illuminating, but I'll post it anyway, as self-treatment at least. To me it is a career question, and a very fundamental one too. Most of you probably don't have these kind of problems, as...