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Finite-temperature Field Theory - Theoretical Physics (TIFR)

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Basics of Statistical <strong>Physics</strong> and Thermodynamics<br />

Scalar fields at finite <strong>temperature</strong><br />

Interacting scalar fields<br />

Statistical QM<br />

Simple examples<br />

One degree of freedom<br />

◮ Consider one state system with E = ω, and ignore zero<br />

point energy<br />

Ĥ | n〉 = ω ˆN | n〉 = n ω | n〉<br />

◮ For bosons/fermions with chemical potential µ, obtain<br />

∞∑<br />

Z b = Tr e −β(ω−µ) ˆN = 〈n | e −β(ω−µ) ˆN 1<br />

| n〉 =<br />

1 − e ,<br />

−β(ω−µ)<br />

Z f = Tr e −β(ω−µ) ˆN =<br />

n=1<br />

1∑<br />

〈n | e −β(ω−µ) ˆN | n〉 = 1 + e −β(ω−µ)<br />

n=1<br />

◮ Taking derivatives...<br />

N b =<br />

1<br />

e β(ω−µ) − 1 , E b = ωN b<br />

N f =<br />

1<br />

e β(ω−µ) + 1 , E f = ωN f<br />

logo<br />

Aleksi Vuorinen, CERN<br />

<strong>Finite</strong>-<strong>temperature</strong> <strong>Field</strong> <strong>Theory</strong>

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