Strings In Background Fields Research Articles

More about partition function of open bosonic string in background fields and string theory effective action

We refine the relation between the renormalized partition function of the open bosonic string in background fields and the effective action. In the process, we get some leading derivative corrections to the Born-Infeld action which include all powers of the gauge field.

Noncritical strings, RG flows and holography

We derive an RG flow equation that is satisfied by the regularized partition function for noncritical strings in background fields. The flow refers to change in the position of a ``boundary'' in the liouville direction. The boundary is required to regularize the ultraviolet divergences in the partition function coming from integration over world-sheets of arbitrarily small area. From the point of view of the target space effective gravitational action that the partition function evaluates on-shell, the boundary regularizes {\it infrared} divergences coming from the infinite volume of the liouville direction. The RG flow equation that we obtain looks very much like the Hamilton-Jacobi constraint equation that an on-shell gauge-fixed gravitational action must satisfy.

Structure of the anomaly in the canonical quantization of bosonic strings in background fields

We consider the anomaly problem in the generalized canonical quantization of a bosonic string interacting with background graviton and antisymmetric tensor fields. We derive an equation for the symbol of the anomaly operator, find a solution to that equation, and establish a general form for the anomaly operator allowed by the quantization procedure.

Massive fields dynamics in open bosonic string theory

We consider the theory of the open bosonic string in massive background fields. The general structure of renormalization in investigated. A general covariant action for a string in background fields of the first massive level is suggested and its symmetries are described. Equations of motion for the background fields are obtained by demanding that the renormalized operator of the energy-momentum tensor trace vanishes.

The non-critical bosonic and spinning string in background fields

Using the Ward-Takahashi identify of the B.R.S.T current of the bosonic and spinning string in background fields, we incorporate the Liouville action in the formal path integral construction of the partition function. This construction is possible at one-loop order with respect to string and Liouville fields and for a background fields satisfying the equations of motion. In these conditions, the results of the standard perturbative treatment show that the central charge term of the operator product expansion of two stress tensors vanishes at d<26 for the bosonic string and at d<10 for the spinning string.

Superconducting cosmic strings in background fields

Superconducting cosmic strings in background fields

Local supersymmetry, superconformal algebra in two dimensions and strings in background fields

We show how the D=2 superconformal algebra emerges from the two-dimensional supergravity and develop a tensor calculus which is useful for constructing invariant actions. We apply this to the supersymmetric nonlinear σ-model in a dilaton background and show that the proper treatment of the auxiliary fields leads to a dilaton dependent four-fermion coupling. Due to this term a nonvanishing dilaton contribution to the metric ß-function emerges at the three-loop order. To this order Ricci flat spaces seem to be consistent with superconformal invariance if the dilaton background satisfies ∇ μ ∇ ν φ=0.

Conformal symmetry, unitarity, and the equations of motion for strings in background fields

We impose the constraint of the unitarity of the S-matrix on the theory of a closed bosonic string propagating in a background of some of its modes. The equations of motion for not only the massless but also for some of the massive modes of the string are thus consistently obtained in a weak field expansion. To a given order in the weak field expansion, they contain contributions to all orders in α′. We also show that conformal invariance guarantees that the S-matrix be unitary.

Polyakov strings in background fields: Wave functions and quantum cosmology

The wave functions or density matrices of superstring theories in curved spacetimes may be used to illuminate the origin and development of the very early universe. A path integral prescription for the ground state due to Hartle and Hawking has been adapted. This involves an integration over fermionic and bosonic strings with boundaries in a curved spacetime background. The wave functions and density matrices of strings in flat spacetime at zero and finite temperatures have been found this way. Some properties of strings in Calabi-Yau compactified backgrounds are also discussed.

The string in background fields and the parallelized manifold

We investigate a generalized non-linear sigma model which describes the string propagation in the presence of background fields. It is pointed out that the non-linear sigma model is generally non-renormalizable, but becomes renormalizable under a certain condition.

Strings in curved space-time: Virasoro algebra in the classical and quantum theory.

We investigate the theory of a closed bosonic string propagating in a background consisting of a condensate of its massless modes. At the classical level, the Virasoro operators and the Hamiltonian are identified and their Poisson-brackets algebra verified. The massless-mode vertex operators for a string in background fields are constructed from the requirement that they have the appropriate Poisson brackets with the Virasoro operators. In the quantum theory, a weak-field expansion of the Virasoro operators is used. The commutators of the Virasoro operators are explicitly evaluated to first order in the weak-field expansion using the Bjorken-Johnson-Low procedure. The equations of motion to first order in weak fields are seen to follow from the requirement of the closure of the Virasoro algebra on the two-dimensional world sheet.

Superconformal invariance and dilaton coupling in string theory

We consider the propagation of the supersymmetric string in background fields consisting of the metric tensor and the dilaton. Using the operator product expansion method we demonstrate that the equations of these fields are a consequence of the superconformal invariance of the string theory.

Strings in background fields: beta functions and vertex operators.

We review the conditions for consistent propagation of closed strings in background fields and discuss the connection between conformal invariance and the vanishing of the renormalization-group \ensuremath{\beta} functions for the generalized \ensuremath{\sigma} model on a curved world sheet. The \ensuremath{\beta} functions with up to four derivative terms are found to be compatible with graviton and dilaton equations of motion provided the former are computed in a nonminimal subtraction scheme. Finally, vertex operators in background fields are discussed and it is shown that the anomalous dimension operator is given by the first variation of the \ensuremath{\beta} function to all orders in \ensuremath{\alpha}'.

Strings in background fields

We formulate the propagation of strings in background fields, including the effects of metric, antisymmetric tensor, and dilaton expectation values, as well as gauge field backgrounds in the case of heterotic strings. The inclusion of background fermion fields is sketched. The equations of motion of all these fields are shown to be the consequence of (super) conformal invariance of the string.