Vacuum decay in the presence of gravity

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2020 Tutor: Jaume Garriga TorresIn this paper, two mechanisms for vacuum decay in field theory are compared. First, using the Coleman-de Lucia method, the transition probability between two non-degenerate vacua is computed. Then this calculation is repeated according to the newly proposed yover method. For this purpose, a numerical simulation is used which solves Einstein's equation for a spherically symmetric metric and with a scalar field as a source. The obtained result shows the yover decay is dominant for a certain parametric range and it has a larger probability of upward transitions relative to Cd

Worldsheet from worldline

We take a step toward a "microscopic" derivation of gauge-string duality. In particular, using mathematical techniques of Strebel differentials and discrete exterior calculus, we obtain a bosonic string worldsheet action for a string embedded in d+1 dimensional asymptotically AdS space from multi-loop Feynman graphs of a quantum field theory of scalar matrices in d-dimensions in the limit of diverging loop number. Our work is building on the program started by 't Hooft in 1974, this time including the holographic dimension which we show to emerge from the continuum of Schwinger parameters of Feynman diagrams.Comment: 5 pages + supplementary material, 4 figure

Holographic entanglement as nonlocal magnetism

The Ryu-Takayanagi prescription can be cast in terms of a set of microscopic threads that help visualize holographic entanglement in terms of distillation of EPR pairs. While this framework has been exploited for regions with a high degree of symmetry, we take the first steps towards understanding general entangling regions, focusing on AdS$_4$. Inspired by simple constructions achieved for the case of disks and the half-plane, we reformulate bit threads in terms of a magnetic-like field generated by a current flowing through the boundary of the entangling region. The construction is possible for these highly symmetric settings, leading us to a modified Biot-Savart law in curved space that fully characterizes the entanglement structure of the state. For general entangling regions, the prescription breaks down as the corresponding modular Hamiltonians become inherently nonlocal. We develop a formalism for general shape deformations and derive a flow equation that accounts for these effects as a systematic expansion. We solve this equation for a complete set of small deformations and show that the structure of the expansion explicitly codifies the expected nonlocalities. Our findings are consistent with numerical results existing in the literature, and shed light on the fundamental nature of quantum entanglement as a nonlocal phenomenon.Comment: 28 pages, 5 figure