# PhysiXxx

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bio website uk.wikipedia.org/wiki/… location Kiev, Ukraine age 19 member for 1 year, 10 months seen Nov 16 '13 at 20:40 profile views 516

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 Dec12 awarded Revival Oct20 comment How do you prove the second law of thermodynamics from statistical mechanics? @BenCrowell . The Loschmid's paradox refers to incompatibility of mechanical and statistical results about symmetry of time inversion. "My" derivations don't contain mechanical description of system, so also it don't contain "time-symmetric assumption". It don't contain any assumptions about time inversion. And finally, if system is closed, the "way back" in time for it is depressed. If it isn't so, please specify where exactly did I go wrong. Oct20 comment How do you prove the second law of thermodynamics from statistical mechanics? @BenCrowell . I didn't use dynamics equations; I only used distribution function. Therefore there is nothing contradictory, so the explanation doesn't lead to Loschmidt's paradox. Oct20 comment How do you prove the second law of thermodynamics from statistical mechanics? @BenCrowell . So, if in initially state (which corresponds to initially moment of time) the closed system wasn't in equilibrium (it must be non-closed before initial moment, of course), it is the most possible that it goes to the state with monotonic increase of entropy, i.e., to the equilibrium state. It leads to the statement $\frac{dS}{dt} \geqslant 0$. Oct20 comment How do you prove the second law of thermodynamics from statistical mechanics? @BenCrowell . But the possibility $dP(E)$ for system is the product of possibilities $dP_{i} \approx exp(S_{i}(\langle E_{i}\rangle))$ of small subsystems. If the system isn't at equilibrium, the energies $\langle E_{i}\rangle$ of it's subsystems may be interpreted as variable energies, by which the equilibrium is established. The greatest probability is reached when $S = S_{max}$. Oct20 comment How do you prove the second law of thermodynamics from statistical mechanics? @BenCrowell . I don't understand why the second statement isn't the consequense of the first. Let's have non-equilbium closed system with energy $E$. We can share it out on small quasiclosed subsystems with energies $E_{i}, \quad \sum_{i}E_{i} = E$. Small subsystems reach an equilibrium (which may be escribed as the state with maximum entropy, which is a consequence of a definition of equilibrium) faster, than system. I.e., there is possible a case when there is an equilibrium in subsystems, but there isn't an equilibrium along the subsystems. So all system isn't in equilibrium. Oct20 revised How do you prove the second law of thermodynamics from statistical mechanics? added 193 characters in body Oct20 answered How do you prove the second law of thermodynamics from statistical mechanics? Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors deleted 1 characters in body Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors added 46 characters in body Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors added 46 characters in body Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors added 21 characters in body Oct19 comment Infinitesimal transformations and Poisson bracket for Dirac spinors @DavidZ . Thank you, I'll fix it. Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors deleted 1 characters in body Oct19 comment Infinitesimal transformations and Poisson bracket for Dirac spinors @DavidZ . I meaned hermitian conjugate to $\Psi$ bispinor. So Dirac conjurated bispinor is $\bar \Psi = \Psi^{+}\gamma^{0}$. Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors added 63 characters in body Oct19 revised Infinitesimal transformations and Poisson bracket for Dirac spinors added 385 characters in body Oct19 asked Infinitesimal transformations and Poisson bracket for Dirac spinors Oct19 comment Stress-energy tensor. Why this general form? The tensor you wrote refer to the tensor of homogeneous isotropic continuum. According to that, it can depend only on metric and speed tensor combinations. Oct19 revised How to introduce generating function in Hamiltonian formalism for field theories? deleted 6 characters in body