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Covers the study of (primarily homogeneous) macroscopic systems from a heat/energy/entropy point of view. Consider also using the tag: [statistical-mechanics].

7 votes
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Does specific heat capacity depend on temperature of the substance?

As a consequence of the 3rd law of thermodynamics or more generally a finite value of residual entropy, you also need to have a vanishing of the heat capacity at low temperature. …
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6 votes
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Fugacity in the classical limit

It depends on what you are interested in. It is often more physically relevant to think at fixed number of particles rather than fixed $\mu$, so $\mu$ picks up an implicit temperature dependence. Take …
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5 votes
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Definition of the pressure in statistical mechanics

While you can choose any two independent variables as your basis function to express any quantity, you need to be careful in the choice of your variables when defining new quantities as derivatives. D …
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5 votes
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Relation between specific heats for a magnetic system

Neglecting pressure and volume, your energy is: $$ dU=TdS+HdM $$ You can therefore apply the same method by formally substituting $P\to-H$ and $V\to M$. The analogue for enthalpy is: $$ \mathcal H = U …
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4 votes

How to choose the microstates so that thermodynamical entropy coincides with statistical mec...

Actually, thermodynamic entropy depends on the definition of your system in some sense, just as the statistical entropy depends on the micro-states. The classic example is Gibbs’ paradox. If you have …
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4 votes

Taking derivative with respect to quantum canonical ensemble expectation value

On a side note, you can avoid the Trotter formula by using instead the standard interaction picture (if you are already familiar with it from previous QM courses). I will write $\partial_{x_i} = \part …
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3 votes

If boiling of water involves change in internal energy, then why does the temperature remain...

This will rather lead to the consideration of free enthalpy $G = F+pV$ which should be more familiar if you've done chemistry or thermodynamics. The discussion is essentially the same though. …
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3 votes

Quasi-static processes that are not reversible

Quasistatic processes encompass reversible processes. The inclusion is strict, because there are some irreversible quasistatic transformations. A typical example of a quasi static process would be a s …
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3 votes
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Jacobian determinants in thermodynamics and a different approach to deriving the Maxwell rel...

Question 1 Yes, you can derive this from the first law of thermodynamics. For a cyclic process $W=Q$, heat equals work. …
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3 votes

Why is entropy a quantification of the typical fluctuation of internal energy around the exp...

In the following, I'll set $k_B=1$. Usually, the fluctuations of energy are rather captured by heat capacity. This is captured by the following formula saying that heat capacity is proportional to the …
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3 votes
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Clarifying the definition of pressure in statistical physics

Actually, your question has little to do with statistical mechanics, but more about classical thermodynamics. … It typically holds in the thermodynamic limit, which is why for most applications classical thermodynamics applies. …
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3 votes

Microcanonical ensemble through Maximum Entropy method

In general, the two distributions have little to do with each other. After all, $\rho_e$ is fixed but $\rho_{mc}$ depends on the variable energy $E$. I will therefore reformulate your question as: can …
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2 votes
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Mixing identical gases in different states (Gibbs paradox)

Yes, it works without any problems. I’ll just add that you can do it all in one go by modifying the expression of your entropy: $$ S =nc_v\ln(T/T_0)+nR\ln\left(\frac{V/n}{ V_0/n_0}\right)+ns_0 $$ with …
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2 votes

Deriving total temperature of a composite system

Assuming your system is isolated you want to maximize $S$ with fixed $U$ according to the second law. More concretely, you want to maximize $S=S_A+S_B$ by only varying $U_A,U_B$ under the constraint $ …
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2 votes
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How does one "invert" derivatives for intensive variables?

The fact that the variables are intensive/extensive is irrelevant. These partial derivatives just come from differential calculus. Slight notation change, I’ll use $M$ for the magnetic moment instead …
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