1
Introduction
Abstract
In this chapter, we introduce the main motivations for studying string theory,
and why it is important to design a string field theory. After describing the
central features of string theory, we describe the most important concepts of
the worldsheet formulation. Then, we explain the reasons leading to string field
theory (SFT) and outline the ideas which will be discussed in the rest of the book.
1.1
Strings, a Distinguished Theory
The first and simplest reason for considering theories of fundamental p-branes
(fundamental objects extended in p spatial dimensions) can be summarized by the
following question: “Why would Nature just make use of point-particles?” There
is no a priori reason forbidding the existence of fundamental extended objects
and, according to Gell-Mann’s totalitarian principle, “Everything not forbidden
is compulsory.” If a consistent theory cannot be built (after a reasonable amount
of effort) or if it contradicts current theories (in their domains of validity) and
experiments, then one can support the claim that only point-particles exist. On the
other side, if such a theory can be built, it is of primary interest to understand it
deeper and to see if it can solve the current problems in high-energy theoretical
physics.
The simplest case after the point-particle is the string, so it makes sense to start
with it. It happens that a consistent theory of strings can be constructed, and that
© Springer Nature Switzerland AG 2021
H. Erbin, String Field Theory, Lecture Notes in Physics 980,
https://doi.org/10.1007/978-3-030-65321-7_1
1
Introduction
Abstract
In this chapter, we introduce the main motivations for studying string theory,
and why it is important to design a string field theory. After describing the
central features of string theory, we describe the most important concepts of
the worldsheet formulation. Then, we explain the reasons leading to string field
theory (SFT) and outline the ideas which will be discussed in the rest of the book.
1.1
Strings, a Distinguished Theory
The first and simplest reason for considering theories of fundamental p-branes
(fundamental objects extended in p spatial dimensions) can be summarized by the
following question: “Why would Nature just make use of point-particles?” There
is no a priori reason forbidding the existence of fundamental extended objects
and, according to Gell-Mann’s totalitarian principle, “Everything not forbidden
is compulsory.” If a consistent theory cannot be built (after a reasonable amount
of effort) or if it contradicts current theories (in their domains of validity) and
experiments, then one can support the claim that only point-particles exist. On the
other side, if such a theory can be built, it is of primary interest to understand it
deeper and to see if it can solve the current problems in high-energy theoretical
physics.
The simplest case after the point-particle is the string, so it makes sense to start
with it. It happens that a consistent theory of strings can be constructed, and that
© Springer Nature Switzerland AG 2021
H. Erbin, String Field Theory, Lecture Notes in Physics 980,
https://doi.org/10.1007/978-3-030-65321-7_1
1