https://en.formulasearchengine.com/api.php?action=feedcontributions&feedformat=atom&user=2001%3A67C%3A10EC%3A3F02%3A8000%3A0%3A0%3A6AAformulasearchengine - User contributions [en]2026-04-30T01:59:59ZUser contributionsMediaWiki 1.43.0-wmf.28https://en.formulasearchengine.com/index.php?title=Thermal_quantum_field_theory&diff=12270Thermal quantum field theory2013-08-19T16:13:18Z<p>2001:67C:10EC:3F02:8000:0:0:6AA: </p>
<hr />
<div>{{Unreferenced stub|auto=yes|date=December 2009}}<br />
In [[theoretical physics]], a '''source field''' is a field <math>J</math> whose multiple<br />
:<math> S_{source} = J\Phi</math><br />
appears in the action, multiplied by the original field <math>\Phi</math>. Consequently, the source field appears on the right-hand side of the equations of motion (usually second-order [[partial differential equation]]s) for <math>\Phi</math>. When the field <math>\Phi</math> is the [[electromagnetic potential]] or the [[metric tensor]], the source field is the [[electric current]] or the [[stress-energy tensor]], respectively.<br />
<br />
All [[Green's function]]s (correlators) may be formally found via [[Taylor expansion]] of the [[partition sum]] considered as a function of the source fields. This method is commonly used in the [[path integral formulation]] of [[quantum field theory]]. The general method by which such source fields can be utilized to obtain propagators in both quantum, statistical-mechanics and other systems is outlined in the article on the [[partition function (mathematics)|partition function]].<br />
<br />
{{DEFAULTSORT:Source Field}}<br />
[[Category:Quantum field theory]]<br />
<br />
<br />
{{Phys-stub}}</div>2001:67C:10EC:3F02:8000:0:0:6AA