Recent content by lerus

Thank you, I think I understood at last. Energy will flow from hotter body to colder, as it should. If temperature of one of the bodies is ##0##, this body will be able to extract energy from any other body. It means that we created Perpetual Motion Machine, which is not possible. Thank you...

I'm sorry, probably I was not able to ask question properly. I didn't want to suggest Perpetual Motion Machine. I wanted to ask - is it possible to determine which volt-ampere characteristics are allowed by 2nd law of thermodynamics and which are not?

Thank you for your answer. I agree, but just ##V=0## is not enough to extract work. It's a combination of ##V=0## and ##I=0## that extracts work. Is it correct that ability to extract work from thermal noise contradicts to the second law of thermodynamics? And one more question, sorry. Does...

I think resistance is a coefficient between current and voltage $$V = I R$$ for extreme cases if ## R=0## it means that always ##V=0## and if ##R=\infty## it means that always ##I=0##

I agree, probably "semi mirror" that reflects all light that goes for instance from right to left but transparent for light that goes from left to right

Perfect diode is a device which electrical resistance is ##R = 0## , when ##V > 0## and ##R=\infty## when ##V<0##

Thank you, are there other devices that are not allowed for the same reason?

Can we say that it is not possible to create a perfect diode because otherwise it is possible to create device that violates 2 law of thermodynamics?

I was talking about formula for gammas. But I need to think a bit more before asking questions. Thank you.

Thank you. You described better than I could describe myself. And, yes , you are right I still need this formulae for covariant derivative $$A_{\alpha\beta;\gamma} = A_{\alpha\beta,\gamma} - A_{\alpha\sigma}\Gamma^{\sigma\beta\gamma} - A_{\beta\sigma}\Gamma^{\sigma\alpha\gamma}$$ I also need the...

Thank you for your answer. We can repeat this for any point, isn't it enough?

Thank you for your answer, I actually used LaTeX and in preview everything looked OK, but when I posted, something happened. Sorry... Did I understand correctly that that this formulae ##A_{\alpha \beta ; \gamma} = A_{\alpha \beta , \gamma} - A_{\sigma \alpha }\Gamma^{\sigma}_{\beta \gamma} -...

I'm reading "Problem Book In Relativity and Gravitation". In this book there is a problem 7.5 Show that metric tensor is covariant constant. To prove it, authors suggest to use formulae for covariant derivative: Aαβ;γ=Aαβ,γ−AσαΓβγσ−AσβΓαγσ after that they write this formulae for tensor g and...

Thank you, very interesting article. It is possible to argue with some of the statements made there, but still very interesting. Thank you.

Thanks a lot for example, I think I understand it better now If variables ##x, y, z## were independent then ## \left( \frac {\partial w} {\partial x} \right)_y \equiv \left( \frac {\partial w} {\partial x} \right) _z## but if ##x, y, z## are not independent, then ## \left( \frac {\partial w}...