TY - BOOK

T1 - Endeavours in Discrete Lorentzian Geometry

T2 - A Thesis in Five Papers

AU - Glaser, Lisa

PY - 2014

Y1 - 2014

N2 - To solve the path integral for quantum gravity, one needs to regularise the spacetimes that are summed over. This regularisation usually is a discretisation, which makes it necessary to give up some paradigms or symmetries of continuum physics.Causal dyn mical triangulations regularises the path integral through a simplicial discretisation that introduces a preferred time foliation.The first part of this thesis presents three articles on causal dynamical triangulations.The first article shows how to obtain a multicritical 2d model by couplingthe theory to hard dimers. The second explores the connection to Horava-Lifshitz gravity that is suggested by the time foliation and establishes that in 2d the theories are equivalent. The last article does not directly concern causal dynamical triangulations but Euclidian dynamical triangulations with an additional measure term, which are examined to understand whether they contain an extended phase without the need for a preferred time foliation.Causal set theory uses an explicitly Lorentz invariant discretisation, whichintroduces non-local effects.The second part of this thesis presents two articles in causal set theory. Thefirst explicitly calculates closed form expressions for the d’Alembertian operator in any dimension, which can be implemented in computer simulations. The second develops a ruler to examine the manifoldlikeness of small regions in a causal set, and can be used to recover locality

AB - To solve the path integral for quantum gravity, one needs to regularise the spacetimes that are summed over. This regularisation usually is a discretisation, which makes it necessary to give up some paradigms or symmetries of continuum physics.Causal dyn mical triangulations regularises the path integral through a simplicial discretisation that introduces a preferred time foliation.The first part of this thesis presents three articles on causal dynamical triangulations.The first article shows how to obtain a multicritical 2d model by couplingthe theory to hard dimers. The second explores the connection to Horava-Lifshitz gravity that is suggested by the time foliation and establishes that in 2d the theories are equivalent. The last article does not directly concern causal dynamical triangulations but Euclidian dynamical triangulations with an additional measure term, which are examined to understand whether they contain an extended phase without the need for a preferred time foliation.Causal set theory uses an explicitly Lorentz invariant discretisation, whichintroduces non-local effects.The second part of this thesis presents two articles in causal set theory. Thefirst explicitly calculates closed form expressions for the d’Alembertian operator in any dimension, which can be implemented in computer simulations. The second develops a ruler to examine the manifoldlikeness of small regions in a causal set, and can be used to recover locality

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122177773105763

M3 - Ph.D. thesis

BT - Endeavours in Discrete Lorentzian Geometry

PB - The Niels Bohr Institute, Faculty of Science, University of Copenhagen

ER -