eprintid: 36724 rev_number: 12 eprint_status: archive userid: 9083 dir: disk0/00/03/67/24 datestamp: 2025-06-30 06:22:50 lastmod: 2025-07-01 09:30:39 status_changed: 2025-06-30 06:22:50 type: doctoralThesis metadata_visibility: show creators_name: Friedrich, Bjoern title: The Measure Problem and Challenges in String Compactifications subjects: ddc-530 divisions: i-130300 adv_faculty: af-13 abstract: The Measure Problem is a fundamental theoretical challenge that arises when studying theories al- lowing for a landscape of different vacua. String theory, with its large number of four-dimensional solutions, is a prominent example. The Measure Problem refers to the issue of how to predict the outcome of future measurements – one of the most fundamental tasks in theoretical physics. In a land- scape scenario, simple event counting is generally insufficient for making predictions. A probability measure on the space of possible measurement outcomes is required. We propose a probability mea- sure, the Local Wheeler-DeWitt Measure, based on fundamental principles of quantum mechanics and semiclassical gravity. We use this measure to predict the scale of inflation to be observed in the future, mainly focusing on the string landscape. Furthermore, we develop a general framework for studying spacetime decays to nothing and the creation of universes from nothing, involving end-of-the-world (ETW) branes. This is necessary because measurement predictions are sensitive to vacuum decay and vacuum creation rates. We explicitly construct an ETW brane for the best-understood part of the string landscape, capable of causing spacetime decay or creation processes. Finally, we propose a new mechanism for universe creation from nothing, utilizing ETW branes in purely off-shell configurations. date: 2025 id_scheme: DOI id_number: 10.11588/heidok.00036724 ppn_swb: 1929424523 own_urn: urn:nbn:de:bsz:16-heidok-367244 date_accepted: 2025-06-12 advisor: HASH(0x5608d3ce4648) language: eng bibsort: FRIEDRICHBTHEMEASURE20250613 full_text_status: public place_of_pub: Heidelberg citation: Friedrich, Bjoern (2025) The Measure Problem and Challenges in String Compactifications. [Dissertation] document_url: https://archiv.ub.uni-heidelberg.de/volltextserver/36724/1/DissertationBjoernFriedrich.pdf