Universe or Multiverse? by group of authors..Recent developments in cosmology and particle physics, such as the string landscape picture, have led to the remarkable realization that our universe - rather than being unique - could be just one of many universes. The multiverse proposal helps to explain the origin of the universe and some of its observational features. Since the physical constants can be different in other universes,

 the fine-tunings which appear necessary for the emergence of life may also be explained. Nevertheless, many physicists remain uncomfortable with the multiverse proposal, since it is highly speculative and perhaps untestable. In this volume, a number of active and eminent researchers in the field - mainly cosmologists and particle physicists but also some philosophers - address these issues and describe recent developments. The articles represent the full spectrum of views, providing for the first time an overview of the subject. They are written at different academic levels, engaging lay-readers and researchers alike.

Table of Contents

Part I. Overviews:
1. Introduction and overview Bernard Carr
2. Living in the multiverse Steven Weinberg
3. Enlightenment, knowledge, ignorance, temptation Frank Wilczek
Part II. Cosmology and Astrophysics:
4. Cosmology and the multiverse Martin J. Rees
5. The anthropic principle revisited Bernard Carr
6. Cosmology from the top down Stephen Hawking
7. The multiverse hierarchy Max Tegmark
8. The inflationary universe Andrei Linde
9. A model of anthropic reasoning: the dark to ordinary matter ratio Frank Wilczek
10. Anthropic predictions: the case of the cosmological constant Alexander Vilenkin
11. The definition and classification of universes James D. Bjorken
12. M/string theory and anthropic reasoning Renata Kallosh
13. The anthropic principle, dark energy and the LHC Savas Dimopoulos and Scott Thomas
Part III. Particle Physics and Quantum Theory:
14. Quarks, electrons and atoms in closely related universes Craig J. Hogan
15. The fine-tuning problems of particle physics and anthropic mechanisms John F. Donoghue
16. The anthropic landscape of string theory Leonard Susskind
17. Cosmology and the many worlds interpretation of quantum mechanics Viatcheslav Mukhanov
18. Anthropic reasoning and quantum cosmology James B. Hartle
19. Micro-anthropic principle for quantum theory Brandon Carter
Part IV. More General Philosophical Issues:
20. Scientific alternatives to the anthropic principle Lee Smolin
21. Making predictions in a multiverse: conundrums, dangers, coincidences Anthony Aguirre
22. Multiverses: description, uniqueness and testing George Ellis
23. Predictions and tests of multiverse theories Don N. Page
24. Observation selection theory and cosmological fine-tuning Nick Bostrom
25. Are anthropic arguments, involving multiverses and beyond, legitimate? William R. Stoeger
26. The multiverse hypothesis: a theistic perspective Robin Collins
27. Living in a simulated universe John D. Barrow
28. Universes galore: where will it all end? Paul Davies
Index.