Statistical Mechanics: Microcanonical State Probability

Click For Summary
SUMMARY

The forum discussion centers on the microcanonical state probability in statistical mechanics, specifically addressing the equations governing the probability \( p(\Gamma) \) in relation to energy constraints. The discussion presents two key problems: first, demonstrating that as \( \Delta E \) approaches zero, \( p(\Gamma) \) can be expressed using the Dirac delta function; second, transforming the integral of the delta function through a change of variables to relate coordinates on the surface defined by \( H=E \). The participants explore methods such as Taylor expansion and polar coordinates to tackle these problems.

PREREQUISITES
  • Understanding of microcanonical ensemble in statistical mechanics
  • Familiarity with Dirac delta function and its properties
  • Knowledge of coordinate transformations in multivariable calculus
  • Basic concepts of energy surfaces in physics
NEXT STEPS
  • Study the properties and applications of the Dirac delta function in physics
  • Learn about the microcanonical ensemble and its implications in statistical mechanics
  • Explore coordinate transformations, particularly in the context of multivariable calculus
  • Investigate Taylor series expansions and their applications in physics problems
USEFUL FOR

This discussion is beneficial for physics students, researchers in statistical mechanics, and anyone interested in the mathematical foundations of thermodynamics and energy distributions.

alejandrito29
Messages
148
Reaction score
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.
 
Physics news on Phys.org
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.
 

Similar threads

Replies
4
Views
1K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 7 ·
Replies
7
Views
4K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
2
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
4K