scholarly journals Cutkosky rules and unitarity (violation) in D-instanton amplitudes

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Ashoke Sen
Keyword(s):  
Field Theory ◽  
String Theory ◽  
Effective Action ◽  
Open String ◽  
Closed String ◽  
World Sheet ◽  
Superstring Theory ◽  
Reality Condition ◽  
Instanton Contribution ◽  
Integration Cycle

Abstract In perturbative amplitudes in quantum field theory and string field theory, Cutkosky rule expresses the anti-hermitian part of a Feynman diagram in terms of sum over all its cut diagrams, and this in turn is used to prove unitarity of the theory. For D-instanton contribution to a string theory amplitude, the cutting rule needed for the proof of unitarity is somewhat different; we need to sum over only those cut diagrams for which all the world-sheet boundaries ending on some particular D-instanton lie on the same side of the cut. By working with the closed string effective action, obtained after integrating out the open string modes, we prove that the D-instanton amplitudes actually satisfy these cutting rules, provided the effective action is real. The violation of unitarity in the closed string sector of two dimensional string theory can be traced to the failure of this reality condition. In the critical superstring theory, multi-instanton and multi anti-instanton amplitudes satisfy the reality condition. Contribution to the amplitudes from the instanton anti-instanton sector satisfies the reality condition if we make a specific choice of integration cycle over the configuration space of string fields, whereas contribution due to the non-BPS D-instantons will need to either vanish or have an overall real normalization in order for it to give real contribution. We use Picard-Lefschetz theory to argue that these conditions are indeed satisfied in superstring theories.

scholarly journals OPEN-CLOSED DUALITY: LESSONS FROM MATRIX MODEL

2004 ◽  
Vol 19 (11) ◽  
pp. 841-853 ◽  
Author(s):  
ASHOKE SEN
Keyword(s):  
Field Theory ◽  
String Theory ◽  
Matrix Model ◽  
String Field Theory ◽  
Classical Result ◽  
Open String ◽  
Closed String ◽  
Tree Level ◽  
Two Dimensional

Recent investigations involving the decay of unstable D-branes in string theory suggest that the tree level open string theory which describes the dynamics of the D-brane already knows about the closed string states produced in the decay of the brane. We propose a specific conjecture involving quantum open string field theory to explain this classical result, and show that the recent results in two-dimensional string theory are in exact accordance with this conjecture.

scholarly journals D-instantons, string field theory and two dimensional string theory

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Ashoke Sen
Keyword(s):  
Field Theory ◽  
String Theory ◽  
Matrix Model ◽  
String Field Theory ◽  
Scattering Amplitude ◽  
Two Dimensional ◽  
World Sheet ◽  
Numerical Result ◽  
Instanton Contribution ◽  
The Matrix

Abstract In [4] Balthazar, Rodriguez and Yin (BRY) computed the one instanton contribution to the two point scattering amplitude in two dimensional string theory to first subleading order in the string coupling. Their analysis left undetermined two constants due to divergences in the integration over world-sheet variables, but they were fixed by numerically comparing the result with that of the dual matrix model. If we consider n-point scattering amplitudes to the same order, there are actually four undetermined constants in the world-sheet approach. We show that using string field theory we can get finite unambiguous values of all of these constants, and we explicitly compute three of these four constants. Two of the three constants determined this way agree with the numerical result of BRY within the accuracy of numerical analysis, but the third constant seems to differ by 1/2. We also discuss a shortcut to determining the fourth constant if we assume the equality of the quantum corrected D-instanton action and the action of the matrix model instanton. This also agrees with the numerical result of BRY.

scholarly journals Gravitational Scattering Amplitudes and Closed String Field Theory in the Proper-Time Gauge

2018 ◽  
Vol 168 ◽  
pp. 07004 ◽  
Author(s):  
Taejin Lee
Keyword(s):  
Field Theory ◽  
Scattering Amplitudes ◽  
String Theory ◽  
String Field Theory ◽  
Fock Space ◽  
Proper Time ◽  
Path Integrals ◽  
Open String ◽  
Closed String ◽  
Quantized String

We construct a covariant closed string field theory by extending recent works on the covariant open string field theory in the proper-time gauge. Rewriting the string scattering amplitudes generated by the closed string field theory in terms of the Polyakov string path integrals, we identify the Fock space representations of the closed string vertices. We show that the Fock space representations of the closed string field theory may be completely factorized into those of the open string field theory. It implies that the well known Kawai-Lewellen-Tye (KLT) relations of the first quantized string theory may be promoted to the second quantized closed string theory. We explicitly calculate the scattering amplitudes of three gravitons by using the closed string field theory in the proper-time gauge.

scholarly journals OPEN STRING ON SYMMETRIC PRODUCT

2001 ◽  
Vol 16 (04) ◽  
pp. 557-607 ◽  
Author(s):  
HIROYUKI FUJI ◽  
YUTAKA MATSUO
Keyword(s):  
Field Theory ◽  
String Field Theory ◽  
Klein Bottle ◽  
Open String ◽  
Closed String ◽  
Symmetric Product ◽  
World Sheet ◽  
Typical Structure ◽  
Light Cone Quantization ◽  
Twisted Boundary Conditions

We discuss some basic properties of the open string on the symmetric product which is supposed to describe the open string field theory in discrete light-cone quantization (DLCQ). We first derive the consistent twisted boundary conditions for Annulus/Möbius/Klein Bottle diagrams and give the explicit form of the corresponding amplitude. They have the interpretation as the long open (or closed) string amplitude but the world sheet topology viewed from the short string and from the long string is in general different. Boundary (cross-cap) states of the short string are classified into three categories, the boundary (cross-cap) states of the long string and the "joint" state which connects two strings. The partition function has the typical structure of the string field theory in DLCQ. Tadpole condition is also analyzed and gives a reasonable gauge group SO(213).

scholarly journals TACHYON DYNAMICS IN OPEN STRING THEORY

2005 ◽  
Vol 20 (24) ◽  
pp. 5513-5656 ◽  
Author(s):  
ASHOKE SEN
Keyword(s):  
Field Theory ◽  
String Theory ◽  
String Field Theory ◽  
Quantum Dynamics ◽  
Open String ◽  
Closed String ◽  
Two Dimensional ◽  
Potential Models ◽  
Conformal Field ◽  
String Background

In this review we describe our current understanding of the properties of open string tachyons on an unstable D-brane or brane–antibrane system in string theory. The various string theoretic methods used for this study include techniques of two-dimensional conformal field theory, open string field theory, boundary string field theory, noncommutative solitons, etc. We also describe various attempts to understand these results using field theoretic methods. These field theory models include toy models like singular potential models and p-adic string theory, as well as more realistic version of the tachyon effective action based on Dirac–Born–Infeld type action. Finally we study closed string background produced by the "decaying" unstable D-branes, both in the critical string theory and in the two-dimensional string theory, and describe the open string completeness conjecture that emerges out of this study. According to this conjecture the quantum dynamics of an unstable D-brane system is described by an internally consistent quantum open string field theory without any need to couple the system to closed strings. Each such system can be regarded as a part of the "hologram" describing the full string theory.

GRAVITON AMPLITUDES, EFFECTIVE ACTION AND STRING GENERATING FUNCTIONAL ON THE DISC

1989 ◽  
Vol 04 (13) ◽  
pp. 3269-3304 ◽  
Author(s):  
A.A. TSEYTLIN
Keyword(s):  
Field Theory ◽  
String Theory ◽  
General Expression ◽  
Effective Field Theory ◽  
Effective Action ◽  
Closed String ◽  
Effective Field ◽  
Generating Functional ◽  
S Matrix ◽  
String Amplitudes

We discuss some issues related to computation and renormalization of closed string amplitudes and effective action on the disc. The general expression for the O (ln ε) term in the string theory and effective field theory generating functionals for the S matrix is found. It is emphasized that in order to establish the correspondence between the string theory and the effective field theory it is necessary to compare the total coefficients of all (“local” plus “modular” and “N-dependent” plus “N-independent”) infinities present in the amplitudes. The regularized expression for the N=3 graviton amplitude on the disc is explicitly computed and it is suggested that a proper regularization is a key to a resolution of a paradox discussed previously in the literature.

scholarly journals Geometry of orientifold vacua and supersymmetry breaking

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Thibaut Coudarchet ◽  
Emilian Dudas ◽  
Hervé Partouche
Keyword(s):  
Field Theory ◽  
Supersymmetry Breaking ◽  
Effective Field Theory ◽  
Scalar Potential ◽  
Open String ◽  
Closed String ◽  
Effective Field ◽  
Internal Space ◽  
Gravitino Mass ◽  
The One

Abstract Starting from a peculiar orientifold projection proposed long ago by Angelantonj and Cardella, we elaborate on a novel perturbative scenario that involves only D-branes, together with the two types of orientifold planes O± and anti-orientifold planes $$ {\overline{\mathrm{O}}}_{\pm } $$ O ¯ ± . We elucidate the microscopic ingredients of such models, connecting them to a novel realization of brane supersymmetry breaking. Depending on the position of the D-branes in the internal space, supersymmetry can be broken at the string scale on branes, or alternatively only at the massive level. The main novelty of this construction is that it features no NS-NS disk tadpoles, while avoiding open-string instabilities. The one-loop potential, which depends on the positions of the D-branes, is minimized for maximally broken, non-linearly realized supersymmetry. The orientifold projection and the effective field theory description reveal a soft breaking of supersymmetry in the closed-string sector. In such models it is possible to decouple the gravitino mass from the value of the scalar potential, while avoiding brane instabilities.

scholarly journals STRING-LOOP CORRECTIONS TO EFFECTIVE ACTION AND BLACK HOLE INSTABILITIES

1995 ◽  
Vol 10 (07) ◽  
pp. 575-585
Author(s):  
V. V. BELOKUROV ◽  
M. Z. IOFA
Keyword(s):  
Black Hole ◽  
String Theory ◽  
Effective Action ◽  
Black Hole Solution ◽  
Bosonic String ◽  
Superstring Theory ◽  
Integration Measure ◽  
String Loop ◽  
Bosonic String Theory ◽  
Closed Bosonic String

Following the ideas of Ref. 3, to account for instability of 2-D black hole solution, we discuss possible imaginary string-loop corrections to the coefficient at the Einstein term in string effective action (EA). In closed bosonic string theory, such corrections appear because of the tachyon contribution to the integration measure over the moduli. In superstring theory, several possible sources of complex one-string-loop contributions to the EA are considered. It is argued that none of them can account for complex corrections to the Einstein term in the effective action.

scholarly journals Open-closed string correspondence in open string field theory

2008 ◽  
Vol 56 (4-5) ◽  
pp. 343-351 ◽  
Author(s):  
M. Baumgartl ◽  
I. Sachs
Keyword(s):  
Field Theory ◽  
String Field Theory ◽  
Open String ◽  
Closed String

DERIVING THE FOUR-STRING AND OPEN-CLOSED STRING INTERACTIONS FROM GEOMETRIC STRING FIELD THEORY

1990 ◽  
Vol 05 (04) ◽  
pp. 659-724 ◽  
Author(s):  
MICHIO KAKU
Keyword(s):  
Field Theory ◽  
String Field Theory ◽  
Geometric Theory ◽  
Open String ◽  
Bound State ◽  
Closed String ◽  
String Length ◽  
Light Cone Gauge ◽  
New Class ◽  
Coulomb Term

One of the baffling questions concerning the covariant open string field theory is why there are two distinct BRST theories and why the four-string interaction appears in one version but not the other. We solve this mystery by showing that both theories are gauge-fixed versions of a higher gauge theory, called the geometric string field theory, with a new field, a string vierbein [Formula: see text], which allows us to gauge the string length and σ-parametrization. By fixing the gauge, we can derive the “endpoint gauge” (the covariantized light cone gauge), the “midpoint gauge” of Witten, or the “interpolating gauge” with arbitrary string lengths. We show explicitly that the four-string interaction is a gauge artifact of the geometric theory (the counterpart of the four-fermion instantaneous Coulomb term of QED). By choosing the interpolating gauge, we produce a new class of four-string interactions which smoothly interpolate between the endpoint gauge and the midpoint gauge (where it vanishes). Similarly, we can extract the closed string as a bound state of the open string, which appears in the endpoint gauge but vanishes in the midpoint gauge. Thus, the four-string and open-closed string interactions do not have to be added to the action as long as the string vierbein is included.

Sign in / Sign up

Export Citation Format

Share Document