Statistical Mechanics: Microcanonical State Probability

In summary, the conversation discusses the probability distribution on a microcanonical state in an isolated system. The probability is given by p(\Gamma) = 1/K if E<H<E + ΔE and 0 otherwise, where K = \int_{\Gamma : E<H<E+ΔE} d \Gamma. When ΔE approaches 0, the probability can be simplified to p(\Gamma) = \frac{\delta (E-H)}{\int_{\Gamma : H=E} \delta(E-H)}. Additionally, using a change of variables from \Gamma to (X,a) where X are 6N-1 coordinates about the surface H=E and a is a perpendicular coordinate, the integral can be written as \int
  • #1
alejandrito29
150
0
In a aislate system, the probability on a microcanonical state [tex]\Gamma[/tex] is

[tex] p(\Gamma ) = 1/K [/tex] , if E<H<E + ΔE, and 0 on otherwise

with [tex] K = \int_{\Gamma : E<H<E+ΔE} d \Gamma [/tex]

a) Show that ΔE →0, then
[tex] p(\Gamma) = \frac{\delta (E-H)}{\int_{\Gamma : H=E} \delta(E-H)} [/tex]

b) Show that if use the change of variable [tex] \Gamma \to (X,a)[/tex], with [tex] X[/tex] are 6N-1 coordinates abaut the surface H=E, and a is a perpendicular coordinate to this surface at the point X, then

[tex] \int_D \delta (E-H) d \Gamma = \int_{D_E} \frac{ d X}{ || \frac{dH}{d \Gamma}||}[/tex]




The rules of this forums says that i says my tried, but, sincerely i don't idea abaut this problem, i think on Taylor for the question a), but i don't have result.
 
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  • #2
For the question b), i think on use polar coordinates, because the surface H=E is a sphere, but i don't arrive to the result.
 

Related to Statistical Mechanics: Microcanonical State Probability

1. What is statistical mechanics?

Statistical mechanics is a branch of physics that uses statistical methods to explain the behavior of large systems of particles, such as molecules, atoms, or subatomic particles. It helps to understand the macroscopic properties of these systems by studying the microscopic interactions between their individual particles.

2. What is the microcanonical ensemble?

The microcanonical ensemble is a statistical distribution used in statistical mechanics to describe a closed system in thermal equilibrium. In this ensemble, the system is isolated and has a fixed energy, volume, and number of particles. The probability of finding the system in a specific state is given by the Boltzmann factor, which depends on the energy of the state and the temperature of the system.

3. What is the significance of the microcanonical state probability?

The microcanonical state probability is significant because it allows us to calculate the probability of a system being in a certain state with a given energy. This is important in understanding the behavior of large systems, as it helps to determine the most probable state of the system and the fluctuations around this state. It also allows us to calculate important thermodynamic quantities, such as entropy and free energy.

4. How is the microcanonical state probability related to entropy?

The microcanonical state probability is directly related to entropy through the Boltzmann formula, which states that the entropy of a system is proportional to the logarithm of the number of microstates available to the system at a given energy. The greater the number of microstates, the higher the entropy and the more disordered the system is.

5. Can the microcanonical state probability be used to describe real-world systems?

The microcanonical state probability is a theoretical concept that can be applied to idealized closed systems. In reality, most systems are open and constantly exchanging energy and particles with their surroundings. However, the principles and equations of statistical mechanics can still be used to describe these systems by considering them as part of a larger closed system and accounting for the energy and particles exchanged with the surroundings.

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