Check the equations 5.74, 5.75, and 5.77 for the example in section 5.4.1

Short Answer

Expert verified

Using equations for several occupied states to distinguish particles, fermions, and bosons, we calculated several occupied states.

First configurationN11=3others zeroQd=6.13!=1Qf=0Qb=1

Second configurationN5=1,N13=2:others zeroQd=6.11!.12!=3Qf=0Qb=1

Third configurationN1=2,N19=1:others zeroQd=6.11!.12!=3Qf=0Qb=1

Fourth configuration N5=N7=N17others zero Qd=6=3Qf=0Qb=1

Step by step solution

01

Define Fermions and bosons

  • Bosons are frequently connected with force carrier particles, whereas fermions are typically associated with matter.
  • Today's particle physics, however, makes it difficult to distinguish between the two ideas.
  • Under extreme conditions, weakly interacting fermions can also exhibit bosonic behavior.
02

Determining the occupied states using formulae

Need to check if equationsandgive the same result as counting states "by hand" in example in Section 5.4.1. We calculate occupied states for distinguishable particles, fermions and bosons by formulae:

Qd(N1,N2,N3,....)=N!n-1dnNnNn!Qf(N1,N2,N3,....)=n-1dn!Nn!(dn-Nn)!Qb(N1,N2,N3,....)=n-1(Nn+dn-1)!Nn!(dn-1)!

Where is number of particles in the system and is degree of degeneracy of oneparticle state. For all configurations in example and . So we have:

Qd=6n-11Nn!Qf=n-11Nn!(1-Nn)!Qf=n-1NnNn!=1

03

Calculating the occupied states

So, the number of occupied states

First configurationN11=3others zero Qd=6.13!=1Qf=0Qb=1

Second configurationN5=1,N13=2:others zeroQd=6.11!.12!=3Qf=0Qb=1

Third configurationN1=2,N19=1:others zeroQd=6.11!.12!=3Qf=0Qb=1

Fourth configurationN5=N7=N17others zerorole="math" localid="1658218029425" Qd=6=6Qf=0Qb=1

Using equations for number of occupied states for distinguishable particles, fermions and bosons, we calculated number of occupied states for example in Section 5.4.1.

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Most popular questions from this chapter

Find the average energy per free electron (Etot/Nd), as a fraction of the

Fermi energy. Answer:(3/5)EF

We can extend the theory of a free electron gas (Section 5.3.1) to the relativistic domain by replacing the classical kinetic energy, E=p2/2m,,with the relativistic formula, E=p2c2+m2c4-mc2. Momentum is related to the wave vector in the usual way: p=hk. In particular, in the extreme relativistic limit, Epc=hck.

(a) Replace h2k2n Equation 5.55 by the ultra-relativistic expression, hck, and calculateEtotin this regime.

dE=h2k22mVπ2k2dk (5.55).

(b) Repeat parts (a) and (b) of Problem 5.35 for the ultra-relativistic electron gas. Notice that in this case there is no stable minimum, regardless of R; if the total energy is positive, degeneracy forces exceed gravitational forces, and the star will expand, whereas if the total is negative, gravitational forces win out, and the star will collapse. Find the critical number of nucleons, Nc , such that gravitational collapse occurs for N>N_{C}is called the Chandrasekhar limit.

(c) At extremely high density, inverse beta decaye-+p+n+v,converts virtually all of the protons and electrons into neutrons (liberating neutrinos, which carry off energy, in the process). Eventually neutron degeneracy pressure stabilizes the collapse, just as electron degeneracy does for the white dwarf (see Problem 5.35). Calculate the radius of a neutron star with the mass of the sun. Also calculate the (neutron) Fermi energy, and compare it to the rest energy of a neutron. Is it reasonable to treat a neutron star non relativistic ally?

The density of copper is8.96g/cm3,and its atomic weight is63.5g/mole

(a) Calculate the Fermi energy for copper (Equation 5.43). Assume d = 1, and give your answer in electron volts.

EF=ħ22m3ρπ22/3 (5.43).

(b) What is the corresponding electron velocity? Hint: SetEF=1/2mv2Is it safe to assume the electrons in copper are nonrelativistic?

(c) At what temperature would the characteristic thermal energyrole="math" localid="1656065555994" (kBT,wherekBkBis the Boltzmann constant and T is the Kelvin temperature) equal the Fermi energy, for copper? Comment: This is called the Fermi temperature,TF

. As long as the actual temperature is substantially below the Fermi temperature, the material can be regarded as “cold,” with most of the electrons in the lowest accessible state. Since the melting point of copper is 1356 K, solid copper is always cold.

(d) Calculate the degeneracy pressure (Equation 5.46) of copper, in the electron gas model.

P=23EtotV=23ħ2kF510π2m=3π22/3ħ25mρ5/3

Imagine two non interacting particles, each of mass , in the one dimensional harmonic oscillator potential (Equation 2.43). If one is in the ground state, and the other is in the first excited state, calculate (x1-x2)2assuming
(a) they are distinguishable particles, (b) they are identical bosons, and (c) they are identical fermions. Ignore spin (if this bothers you, just assume they are both in the same spin state.)

(a) Write down the Hamiltonian for two noninteracting identical particles in the infinite square well. Verify that the fermion ground state given in Example 5.1 is an eigenfunction of H, with the appropriate eigenvalue.

(b) Find the next two excited states (beyond the ones in Example 5.1) - wave functions and energies - for each of the three cases (distinguishable, identical bosons, identical fermions).

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