Table Of ContentJan Louis
With String Theory
to the Big Bang
A Journey to the Origin
of the Universe
essentials
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Jan Louis
With String Theory to
the Big Bang
A Journey to the Origin
of the Universe
Jan Louis
Fachbereich Physik
Universität Hamburg
Hamburg, Germany
ISSN 2197-6708 ISSN 2197-6716 (electronic)
essentials
ISSN 2731-3107 ISSN 2731-3115
Springer essentials
ISBN 978-3-658-35849-5 ISBN 978-3-658-35850-1 (eBook)
https://doi.org/10.1007/978-3-658-35850-1
This book is a translation of the original German edition „Mit der Stringtheorie zum Urknall“ by
Louis, Jan, published by Springer Fachmedien Wiesbaden GmbH in 2021. The translation was
done with the help of artificial intelligence (machine translation by the service DeepL.com). A
subsequent human revision was done primarily in terms of content, so that the book will read
stylistically differently from a conventional translation. Springer Nature works continuously to
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support the authors.
© Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2021
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What You Can Find in This essential
• An introduction and overview of the state of the art in cosmology, particle
physics and string theory.
• A short version of the history of our universe—from established facts to a
selection of speculations.
v
Preface
The whence and the whither have always occupied and inspired people. Today
we are able to describe the history of the universe scientifically with impressive
accuracy. With very few assumptions, it is possible to reconstruct this history
from about 0.00000001 seconds after the Big Bang until today. The interplay of
cosmology, general relativity, particle physics and quantum theory is the key to
this success. Only the beginning, the Big Bang itself, has so far eluded the estab-
lished laws of physics. The closer we get to it, the more speculative the situation
becomes.
In this book, we want to take the reader on a journey to the Big Bang and learn
about the various physical theories, observations and discoveries along the way.
In the process, string theory will also be presented as a possible candidate for an
all-encompassing physical theory that has the potential to explain the Big Bang.
Its sometimes spectacular predictions, such as additional spatial dimensions or
parallel universes, will also be discussed.
Who is this book written for, or who would we like to invite on this journey?
Anyone can go and we hope that everyone will enjoy it. However, some basic
knowledge of natural science is certainly useful from time to time.
The book would not have been possible without the critical and support-
ive comments of Wilfried Buchmüller, Ilka Flegel, Nicola Gaedicke, Sarah
Gottschalk, Michael Grefe, Wiebke Kircheisen, Norbert König, Christian Kühn,
Margit Maly, and Alexander Westphal. Thank you very much.
Jan Louis
vii
Contents
1 Introduction ................................................ 1
2 The Expanding Universe ..................................... 5
2.1 The Observation ......................................... 5
2.2 The Theoretical Description: Einstein’s
General Theory of Relativity ............................... 9
3 The Building Blocks of Matter ................................. 13
3.1 The Geiger-Marsden-Rutherford Experiment .................. 13
3.2 The Quantum Theory ..................................... 14
3.3 Particle Accelerators ...................................... 16
3.4 The Standard Model of Particle Physics ...................... 17
4 The Big Bang Theory: The Standard Model of Cosmology ......... 23
4.1 The Formation of Hydrogen and Helium ...................... 24
4.2 The Cosmic Background Radiation .......................... 24
4.3 Dark Matter ............................................ 26
4.4 The Formation of Stars and Galaxies ......................... 27
4.5 Black Holes ............................................ 27
4.6 Gravitational Waves ...................................... 28
5 String Theory ............................................... 31
5.1 The Necessity of a Quantum Gravity ......................... 31
5.2 The Basic Idea of String Theory ............................ 32
5.3 Open Questions of String Theory ............................ 34
5.4 Additional Spatial Dimensions ............................. 38
5.5 String Theory and Mathematics ............................. 40
ix
x Contents
5.6 Unification: Extensions of the Standard Model ................. 41
5.7 String Theory and Dark Energy ............................. 42
6 The Very Early Universe from the Big Bang to 10 10 seconds ....... 43
−
6.1 Post-Planck Era and Inflation ............................... 43
6.2 With String Theory to the Big Bang: The Planck Era ............ 45
7 Summary and Outlook ....................................... 49
Further Reading ............................................... 53
1
Introduction
People have always tried to understand what can be seen in the sky. This has led
to the development of astronomy—the science of the universe and the celestial
bodies within it. Human curiosity paired with the fascination of the overwhelm-
ing sight of the night sky founded and fueled this branch of science. A widely
assumed connection to religious and cultural aspects added to the interest. And
then, of course, there were more practical motivations, such as safe navigation on
the high seas, which made astronomy socially and politically necessary.
At first, people observed the universe with only their eyes, then later aids such
as the telescope were invented, and today large telescopes are used on high moun-
tains in remote corners of the earth. Moreover, not only visible light but any radi-
ation that reaches us from space is studied. Almost routinely, telescopes are now
sent into space to record and analyze the radiation received without the perturba-
tion of the Earth’s atmosphere. This has resulted in an impressive knowledge of
the universe.
What exactly do we see? With the naked eye we can see stars, planets and, in
isolated places on Earth, the Milky Way. It is a so-called spiral galaxy, compa-
rable to the galaxy shown in Fig. 1.1. Indeed, observation of the universe with
telescopes reveals that almost all stars are organized into galaxies, and galaxies
in turn are part of clusters of galaxies. However, stars, galaxies and galaxy clus-
ters are not evenly distributed in the universe, but are arranged in a large-scale
structure.
The observation of the universe has always been closely linked to the question
of the “where from” and “where to” of mankind. Can we understand how the uni-
verse came into being and why it looks the way it does today? Can we explain,
for example, the large-scale structure of the universe or the formation of stars or
© Springer Fachmedien Wiesbaden GmbH, part of Springer Nature 2021 1
J. Louis, With String Theory to the Big Bang, essentials,
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