Modular Hamiltonians, Relative Entropy and the Entropy-Area Law in de Sitter Spacetime

Explore advanced concepts in quantum field theory and general relativity through this 56-minute conference talk examining modular Hamiltonians and their applications to entropy calculations in curved spacetimes. Learn how Tomita-Takesaki theory provides a framework for computing finite entropy measures in quantum field theory, where naive entropy calculations typically diverge. Discover two recently derived examples of modular Hamiltonians: one for conformal fields in diamond regions of conformally flat spacetimes including de Sitter space, and another for low-mass fermions in diamond regions of two-dimensional Minkowski spacetime. Examine detailed calculations of relative entropy between the de Sitter vacuum state and coherent excitations in both diamond and wedge regions, with verification that results satisfy expected relative entropy properties. Investigate how thermodynamic relations determine local temperature measurements for observers in these spacetimes, and understand how coherent excitations create geometric backreaction effects. Conclude with a rigorous proof of the entropy-area law in de Sitter spacetime, connecting quantum information theory with gravitational physics through the lens of modular theory and relative entropy measures.