Help with an ideal gas canonical ensemble partition function integral

In summary, the volume in this context is derived from the equation ##\int \prod_{i=1}^N\left(d^3\vec{q}_i\right)=V^N## where the ##q_i## represent position coordinates. The remaining portion involves a 3N dimensional Gaussian integral over momenta."
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AndreasC
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I'm reading Mehran Kardar's book on statistical mechanics, and it's great but super terse. I am trying very hard to understand a particular integral that is used over and over again for ideal gases, with no luck so far. Any help? I've posted a relevant picture below.
IMG_20201124_192841.jpg


Where does the volume even come from? Any help would be appreciated!
 
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AndreasC said:
Where does the volume even come from? Any help would be appreciated!

I'm not a physicist, but it looks just like ##\int \prod_{i=1}^N\left(d^3\vec{q}_i\right)=V^N## since the ##q_i## are presumably position coordinates.
 
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Infrared said:
I'm not a physicist, but it looks just like ##\int \prod_{i=1}^N\left(d^3\vec{q}_i\right)=V^N## since the ##q_i## are presumably position coordinates.
Oh, dammit, yeah, that where it comes from haha! Somehow I missed it. And then I guess the rest is just a 3N dimensional Gaussian integral over the momenta, right? Nice, that makes sense.
 

1. What is an ideal gas canonical ensemble partition function?

An ideal gas canonical ensemble partition function is a mathematical expression used in statistical mechanics to describe the distribution of particles in a system at a given temperature, volume, and number of particles. It takes into account the energy levels and degeneracies of the particles in the system.

2. How is the partition function integral calculated?

The partition function integral is calculated by integrating over all possible values of the system's energy levels, taking into account the degeneracies of those energy levels. This integral can be solved analytically for simple systems, but for more complex systems, numerical methods are often used.

3. What is the significance of the partition function integral in statistical mechanics?

The partition function integral is a fundamental concept in statistical mechanics, as it allows us to calculate important thermodynamic properties of a system such as the internal energy, entropy, and free energy. It also provides a link between the microscopic properties of particles and the macroscopic behavior of a system.

4. How does the partition function integral relate to the canonical ensemble?

The partition function integral is used in the canonical ensemble, which is a statistical ensemble that describes a system at a constant temperature, volume, and number of particles. The partition function integral allows us to calculate the probability of a system being in a particular energy state in the canonical ensemble.

5. Can the partition function integral be used for non-ideal gases?

Yes, the partition function integral can be used for both ideal and non-ideal gases. However, for non-ideal gases, additional corrections must be made to account for interactions between particles. This can make the partition function integral more complex and difficult to solve analytically.

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