Microscopic diagonal entropy and its connection to basic thermodynamic relations |
| |
Authors: | Anatoli Polkovnikov |
| |
Institution: | Department of Physics, Boston University, Boston, MA 02215, USA |
| |
Abstract: | We define a diagonal entropy (d-entropy) for an arbitrary Hamiltonian system as Sd=-∑nρnnlnρnn with the sum taken over the basis of instantaneous energy states. In equilibrium this entropy coincides with the conventional von Neumann entropy Sn = −Trρ ln ρ. However, in contrast to Sn, the d-entropy is not conserved in time in closed Hamiltonian systems. If the system is initially in stationary state then in accord with the second law of thermodynamics the d-entropy can only increase or stay the same. We also show that the d-entropy can be expressed through the energy distribution function and thus it is measurable, at least in principle. Under very generic assumptions of the locality of the Hamiltonian and non-integrability the d-entropy becomes a unique function of the average energy in large systems and automatically satisfies the fundamental thermodynamic relation. This relation reduces to the first law of thermodynamics for quasi-static processes. The d-entropy is also automatically conserved for adiabatic processes. We illustrate our results with explicit examples and show that Sd behaves consistently with expectations from thermodynamics. |
| |
Keywords: | Statistical mechanics Thermodynamics Quantum dynamics Hamiltonian systems |
本文献已被 ScienceDirect 等数据库收录! |
|