Truncating the series. In section 5.2, I truncated a Taylor series abruptly; the questions below help you to justify that step.
To simplify the analysis, specify that the reservoir is a monoatomic classical ideal gas of N spinless atoms
To specify an energy eigenstate, we will need to specify N triple {n_x,n_y,n_z} in the spirit of section 4.1 There will be one quantum state per unit volume in an enlarged mathematical space of 3 N dimensions. (That statement would be literally correct if the N particles were distinguishable. The actual indistinguishability has no qualitative effect on the subsequent reasoning, and so we ignore it.) The energy E will continue to be proportional to n^2 , where is n is the “radius” vector in that space. The integral in the analog of equation (4.6), however, will contain the factor n^(3N-1) dn, for a “volume” in a space of 3 N dimensions must go as n^3N, The density of states must have the form
D(E)=constant×E^(f(N))
(a) Determine the exponent f(N); do not bother to evaluate the constant.
(b) Check your value for the exponent f(N) by computing from the partition function.
(c) To study the reservoir’s entropy, write the entropy as follows:
S_res (E_tot-E_j )=kf(N)in(1-E_j/E_tot )+part independent of E_j
Be sure to confirm this form, starting with the definition in equation (4.15). Because the reservoir is much larger than the sample, E_tot≅N×(3/2 kT), and this approximations gets better as N gets larger. Write out the first three nonzero terms in the Taylor series of the logarithm (about the 1 for the argument). Then study the limit of equation (1) as N goes to infinity. Do you find that only surviving dependence on E_j is the single term that we calculated in section 5.2?
Truncating the series. In section 5.2, I truncated a Taylor series abruptly; the questions below help you to justify that step. To simplify the analysis, specify that the reservoir is a monoatomic classical ideal gas of N spinless atoms To specify an energy eigenstate, we will need to specify N triple {n_x,n_y,n_z} in the spirit of section 4.1 There will be one quantum state per unit volume in an enlarged mathematical space of 3 N dimensions. (That statement would be literally correct if the N particles were distinguishable. The actual indistinguishability has no qualitative effect on the subsequent reasoning, and so we ignore it.) The energy E will continue to be proportional to n^2 , where is n is the “radius” vector in that space. The integral in the analog of equation (4.6), however, will contain the factor n^(3N-1) dn, for a “volume” in a space of 3 N dimensions must go as n^3N, The density of states must have the formD(E)=constant×E^(f(N))(a) Determine the exponent f(N); do not bother to evaluate the constant.(b) Check your value for the exponent f(N) by computing from the partition function.(c) To study the reservoir’s entropy, write the entropy as follows: S_res (E_tot-E_j )=kf(N)in(1-E_j/E_tot )+part independent of E_jBe sure to confirm this form, starting with the definition in equation (4.15). Because the reservoir is much larger than the sample, E_tot≅N×(3/2 kT), and this approximations gets better as N gets larger. Write out the first three nonzero terms in the Taylor series of the logarithm (about the 1 for the argument). Then study the limit of equation (1) as N goes to infinity. Do you find that only surviving dependence on E_j is the single term that we calculated in section 5.2?
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