Adiabatic accessibility
Adiabatic accessibility denotes a relation between the different states of a thermodynamic system. The coined by Constantin Carathéodory in 1909 term " adiabatic accessibility " was taken up in 1999 by Elliott Lieb and Jakob Yngvason in their axiomatic foundations of thermodynamics. With the help of the concept of adiabatic accessibility can define the entropy without taking the concepts of " heat " or the " temperature" to help and without using information about the microscopic structure of matter.
A state Y of a thermodynamic system is known from the state X of the same system as adiabatic reachable if it is possible to run the system with the aid of an " apparatus ", and a weight in the context of a process from the state X in the state Y, where the apparatus returns to the state at the end of the process that they had at the beginning of the process. The weight must it have changed its position in the gravitational field.
For example, if the system has a certain amount of water in the state of X is present, the water in the form of snow and the state of Y in the liquid form, Y is adiabatic reached from X. It then writes, pronounced " X, is Y". For example, an on- a yarn weight of a roll, from which the yarn unwinds, driving a mechanical stirrer which causes the snow to melt. Conversely, X is Y not adiabatically accessible, which combined with the notation ("X is true before Y") is expressed.
Two states that are mutually adiabatically accessible, hot adiabatic equivalent.
Entropy is then defined as a function of the system state such as part of the fa- Yngvason theory that