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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 />

Feynman rules at finite <strong>temperature</strong><br />

Thermodynamics of ϕ 4 theory<br />

Feynman rules for φ 4 theory<br />

◮ Assume massive scalar theory with L I = ϕ 4<br />

◮<br />

Graphs composed of four-ϕ vertices and propagators<br />

1<br />

D 0 (ω n , p) =<br />

ωn 2 + p 2 + m 2<br />

◮ Feynman rules almost the same as at T = 0:<br />

◮ As usual, only need to compute connected diagrams<br />

◮ Same symmetry factors, vertex functions, etc.<br />

◮ Only changes due to discrete values of p 0 :<br />

◮ In integration measure: ∫ d 4 p<br />

→ T ∑ ∫ d 3 p<br />

(2π) 4<br />

n (2π) 3<br />

◮ In vertices: δ (4) (P 1 − P 2 ) → δ n1 ,n 2<br />

δ (3) (p 1 − p 2 )<br />

◮ Question: How to evaluate the necessary sum-integrals?<br />

◮ Will be covered in more detail later...<br />

logo<br />

Aleksi Vuorinen, CERN<br />

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

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