22. February 2018

**BREMEN-OLDENBURG RELATIVITY SEMINAR**University of Oldenburg

Location: |
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When: | Thursday, 22 February 2018 11:15 | |

Speaker: | Dr. Kamal Hajian (Institute for Research in Fundamental Sciences Tehran, Iran) | |

Title: | Cosmological constant is a conserved charge |

**Abstract:** The cosmological constant can (always) be considered as the on-shell value of a top form in gravitational theories. The top form is the field strength of a gauge field, and the theory enjoys a gauge symmetry. After a historical review of the cosmological constant, I will show that the cosmological constant is the charge of the global part of the gauge symmetry of the top form, and is conserved irrespective of the dynamics of the metric and other fields. In addition, I will introduce its conjugate chemical potential, and prove the generalized first law of thermodynamics which includes variation of the cosmological constant as a conserved charge. At the end, I will discuss how our new term in the first law is related to the volume-pressure term. This talk is based on the paper arXiv:1710.07904 in collaboration with Dmitry Chernyavsky.