Recent content by dapias09

Thank you @UltrafastPED, would one example about a proper-time scale be the average time of reaching the thermal equilibrium?

Hi guys, In a scientific paper, I have found the following sentence: "...given the fact that the system is homogeneous in energy, or equivalently, that it has no proper time scale." I'm not sure about what the authors intend to say (what is the relation between being homogeneous in...

Thanks for answering jfizzix. That's what I wanted to discuss. Best Regards!

Hi guys, I've got a doubt concerning to the minimum mechanical work and the work-energy theorem. Consider the following Tippens' problem (8.4): A 5-kg hammer is lifted to a height of 3 m. What is the minimum required work? The answer looks very simple and inocent, W = weight times...

Ok, thank you clem.

Hi Andy, thanks for your answer. Well, my punctual question is, can I type $$ T_{ij} = (E_iE_j - \frac{1}{2}\delta_{ij}E^2) + (B_iB_j - \frac{1}{2}\delta_{ij}B^2)$$ with the dummy indices equal to $x$, $y$, $z$ as well as $r$, $\theta$, $\phi$ , or the indices of any other coordinate...

Hi guys, I would like to know if the answer given to this thread is correct https://www.physicsforums.com/showthread.php?t=457405 I got the same doubt, is the expression for the tensor given in cartesian coordinates or is it general to any orthogonal coordinate system? Thanks in advance

Thank you Jorriss, yes I realized that the hard-point gas is the same than the hard-sphere gas but in one dimension.

Hi all, what do you understand by a hard-point gas?, I mean in terms of its hamiltonian. Thanks in advance.

Thank you Tac-Tics

Hi all, I need help with something basic but I'm not sure how to handle it. The doubt is about how to consider the topology of the unit interval I=[0,1] inherited of the real line with its usual topology (intervals of the type (a,b)). I think that is just to pay attention to the definition...

Thank you lavinia. I think I got it.

Hi micromass. Thanks for your reply. I think you mean the function (x,y) → x^{2}+y^{2}-a^{2}, being a the radius of the circle. I think you said that this is a closed set because is the preimage of the zero point that is a closed set on the reals. I don't figure out why you said that now the...

Hi guys, I would like to understand why a circle (and in general a n-sphere) as a subset of R^2 (in general R^(n+1)) with the standard topolgy is considered a closed and a bounded set. I think that this can be a closed set because its complement (the interior of the circle and the rest of...

Hi all, I would like to know if somebody know the cases when we have in the space time manifold (and in general in any manifold) geodesic incompleteness. I know that a case can be a singularity in the curvature scalar (or in general, a singularity in any component of the Riemann tensor)...