Problem with Bose-Einstein Condensation

Click For Summary
SUMMARY

The discussion centers on the derivation of the formula for the number of particles not in the ground state in Bose-Einstein condensation, as presented in section 7.1 of Pathria's statistical mechanics. The formula is given by ## N_e=V\frac{(2\pi m k T)^{\frac 3 2}}{h^3}g_{\frac 3 2}(z) ##, where ## z=e^{\frac \mu {kT}} ##. The issue raised pertains to the behavior of the system at temperatures greater than the critical temperature (## T>T_c ##), where the user observes Bose-Einstein condensation occurring despite the theoretical framework suggesting it should only happen at temperatures below the critical threshold (## T PREREQUISITES

  • Understanding of Bose-Einstein statistics
  • Familiarity with statistical mechanics concepts
  • Knowledge of critical temperature and its dependence on particle density
  • Basic grasp of thermodynamic variables such as temperature and chemical potential
NEXT STEPS
  • Study the derivation of Bose-Einstein distribution in detail
  • Explore the implications of particle density on critical temperature in Bose-Einstein condensation
  • Investigate the behavior of quantum gases at varying temperatures and densities
  • Learn about the mathematical properties of the Riemann zeta function, particularly ## \zeta(\frac 3 2) ##
USEFUL FOR

Physicists, graduate students in statistical mechanics, and researchers studying quantum gases and phase transitions will benefit from this discussion.

ShayanJ
Science Advisor
Insights Author
Messages
2,802
Reaction score
605
In section 7.1 of his statistical mechanics, Pathria derives the formula ## N_e=V\frac{(2\pi m k T)^{\frac 3 2}}{h^3}g_{\frac 3 2}(z) ## where ## \displaystyle g_{\frac 3 2}(z)=\sum_{l=1}^\infty \frac{z^l}{l^{\frac 3 2}} ## and ## z=e^{\frac \mu {kT}} ##. This formula gives the number of particles that are not in the ground state w.r.t. the temperature.
The maximum of ## g_{\frac 3 2}(z) ## happens at ## z=1 ## and is equal to ## \zeta(\frac 3 2) ##. So whenever ## z=1 ##, ## N_e ## reaches its maximum and any other particle has to go to the ground state and ## z=1 ## happens at any ## T<T_c ##.
My problem is with ## T>T_c ##. I can calculate ## N_e ## for any temperature which gives me the capacity of the excited states at the given temperature. Now I put ## N>N_e ## particles in the energy levels and so the excited states become full and the rest of the particles have to go to the ground state and I get Bose-Einstein condensation again, this time for ## T>T_c ## which can't be right because we're supposed to have condensation only for ## T<T_c ##.
What's wrong here?
Thanks
 
Physics news on Phys.org
The critical temperature is dependent on the particle density, so if you keep the volume constant and add more particles, ##T_{c}## is going to change as well.
 

Similar threads

Replies
2
Views
6K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
10
Views
4K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
4
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 0 ·
Replies
0
Views
1K