M.Sc Student | Marjieh Raja |
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Subject | An Entropy Current in Superspace |

Department | Department of Physics |

Supervisor | Professor Amos Yarom |

Full Thesis text |

Entropy is one of the most fundamental concepts in physics. While it is well-defined and intuitive, its effect on physical processes is surprising and far reaching. The second law of thermodynamics has repercussions on a broad spectrum of physical phenomena including phase transitions, black holes and information theory. In the context of hydrodynamics, a local version of the second law tightly constrains the transport properties of fluids. While the role of a local version of the second law is intuitively clear, its appearance in any effective theory is unanticipated. Noether's theorem guarantees that for each symmetry we will have a conserved current whose divergence equals zero and a corresponding Ward identity, but it is difficult to conceive of a mechanism which will lead to an inequality rather than an equality. In the present work we construct an entropy current using a supersymmetric formulation of the low-energy effective action for the Schwinger-Keldysh generating functional. We define an entropy current quantum mechanically by coupling it to an external source. It is given by the bottom component of an entropy current superfield which is conserved in superspace, but when restricted to real space satisfies a non-conservation law. Our analysis is valid in the probe limit which allows us to fully treat quantum fluctuations.