# String creation and destruction

• atyy
In summary: This is a result of the fact that in cubic open Neveu-Schwarz string field theory the non-minimal variables do not have a Killing form. However, the condition that the non-minimal variables be self-adjoint is still met. In particular, the second order differential equation for the field equation is a second order linear equation in the non-minimal variables. This is a direct consequence of the fact that the non-minimal variables form a basis for the vacuum state. In a similar way, this fact can be used to show that the second order equation for the field equation is a second order linear equation in the total energy. In other words, the total energy of the theory is a linear function of
atyy
Can strings be created and destroyed (like particles)?

You mean the whole string, not the vibration?

The string worldsheet would look like a 2-sphere; I have never seen something like that, but it's a good idea.

In a path integral in QFT this would be something like a disconnected Greens function which can be eliminated.

tom.stoer said:
You mean the whole string, not the vibration?

Yes.

Yes. Whole strings are created and destroyed in string field theory.

How do these "disconnected vacuum bubbles contribute"?

Eh? I don't know much about string field theory, but I think vacuum bubble diagrams do not contribute.

But when you include interaction vertices, strings can join and split.

Ben Niehoff said:
Yes. Whole strings are created and destroyed in string field theory.

What's up with string field theory these days? It seems to have been quite popular about 5 pr 6 years ago, but at least casual browsing of arxiv doesn't seem to turn up much recent. Any good reviews you know of?

http://arxiv.org/abs/hep-th/0605202
String Field Theory
Washington Taylor (MIT, Stanford)
(Submitted on 19 May 2006 (v1), last revised 28 Jun 2006 (this version, v2))
This elementary introduction to string field theory highlights the features and the limitations of this approach to quantum gravity as it is currently understood. String field theory is a formulation of string theory as a field theory in space-time with an infinite number of massive fields. Although existing constructions of string field theory require expanding around a fixed choice of space-time background, the theory is in principle background-independent, in the sense that different backgrounds can be realized as different field configurations in the theory. String field theory is the only string formalism developed so far which, in principle, has the potential to systematically address questions involving multiple asymptotically distinct string backgrounds. Thus, although it is not yet well defined as a quantum theory, string field theory may eventually be helpful for understanding questions related to cosmology in string theory.

http://arxiv.org/abs/0901.3386
Regularizing Cubic Open Neveu-Schwarz String Field Theory
Nathan Berkovits, Warren Siegel
(Submitted on 22 Jan 2009 (v1), last revised 27 May 2009 (this version, v2))
After introducing non-minimal variables, the midpoint insertion of Y\bar Y in cubic open Neveu-Schwarz string field theory can be replaced with an operator N_\rho depending on a constant parameter \rho. As in cubic open superstring field theory using the pure spinor formalism, the operator N_\rho is invertible and is equal to 1 up to a BRST-trivial quantity. So unlike the linearized equation of motion Y\bar Y QV=0 which requires truncation of the Hilbert space in order to imply QV=0, the linearized equation N_\rho QV=0 directly implies QV=0.

Last edited:

## 1. How is a string created?

A string is created by assigning a sequence of characters within quotation marks to a variable. This can be done using various programming languages such as Java, Python, or C++.

## 2. Can a string be modified or changed?

Yes, a string can be modified or changed by reassigning a new sequence of characters to the same variable. However, depending on the programming language, strings may be immutable, meaning they cannot be modified in place and a new string must be created instead.

## 3. How is a string destroyed or deleted?

In most programming languages, strings are automatically destroyed or removed from memory once they are no longer referenced by any variable. This process is known as garbage collection. Some languages, such as C++, require manual deletion of strings using the delete keyword.

## 4. What happens when two strings are concatenated?

Concatenation is the process of combining two or more strings together. When two strings are concatenated, a new string is created with the characters of both strings. Depending on the programming language, this can be done using the addition operator (+) or specific string concatenation methods.

## 5. Can strings be compared for equality?

Yes, strings can be compared for equality using various methods such as the equals() method in Java or the == operator in Python. These comparisons check if the sequences of characters in the strings are the same.

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