Related papers: Off-shell Closed String Amplitudes: Towards a Comp…
This thesis investigates correspondences between open and closed strings. This is done on the level of coupled open-closed moduli spaces and from a string field theoretic point of view. The construction of boundary string field theory on…
Using string field theory, we argue that the tachyon potential on a D-brane anti-D-brane system in type II string theory in arbitrary background has a universal form, independent of the boundary conformal field theory describing the brane.…
We study gauge invariant operators of open string field theory and find a precise correspondence with on-shell closed strings. We provide a detailed proof of the gauge invariance of the operators and a heuristic interpretation of their…
A method to define and calculate one-loop amplitudes with an off-shell space-like, or $k_T$-dependent, gluon is presented. It introduces a practical regularization to deal with the divergencies that appear due to linear denominators, and…
We compute a class of gauge invariant observables for marginal solutions and the tachyon vacuum. In each case we find that the observables are related in a simple way to the closed-string tadpole on a disk with appropriate boundary…
We derive the $\sigma$-model tachyon $\beta$-function equation of 2-dimensional string theory, in the background of flat space and linear dilaton, working entirely within the $c=1$ matrix model. The tachyon $\beta$-function equation is…
We develop efficient algorithms for level-truncation computations in open bosonic string field theory. We determine the classical action in the universal subspace to level (18,54) and apply this knowledge to numerical evaluations of the…
We generalize to the case of compactified superstrings a construction given previously for critical superstrings of finite one loop amplitudes that are well-defined for all external momenta. The novel issues that arise for compactified…
In the cubic string field theory, using the gauge invariant operators corresponding to the on-shell closed string vertex operators, we have explicitly evaluated the decay amplitudes of two open string tachyons or gauge fields to one closed…
Cosmological solutions of the beta function equations for the background fields of the closed bosonic string are investigated at the one-loop level. Following recent work of Kostelecky and Perry, it is assumed that the spatial sections of…
We investigate the quantum structure of Witten's cubic open bosonic string field theory by computing the one-loop contribution to the open string tadpole using both oscillator and conformal field theory methods. We find divergences and a…
Recent advances in non-critical string theory allow a unique continuation of critical Polyakov string amplitudes to off-shell momenta, while preserving conformal invariance. These continuations possess unusual, apparently stringy,…
We express one-loop string amplitudes involving both open and closed strings as sum over pure open string amplitudes. These findings generalize the analogous tree-level result to higher loops and extend the tree-level observation that in…
String theory relies on spacetime supersymmetry to guarantee the existence of stable vacua. In this review, we survey two features of non-supersymmetric strings that challenge both aspects: the appearance of tachyons and worldsheet…
In the application of on-shell recursion relation to string amplitudes, one challenge is the sum over infinite intermediate on-shell string states. In this note, we show how to sum these infinite states explicitly by including unphysical…
Closed string tachyon emission from a traveling long string in Liouville string theory is studied. The exact collective field Hamiltonian in the adjoint sector of the c=1 matrix model is computed to capture the interaction between the tip…
We solve the geometry of the closed string field theory five-point vertex. Our solution is calculated in terms of quadratic Strebel differentials which are found numerically all over the relevant subspace of the moduli space of spheres with…
On-shell amplitudes are invariant under field redefinitions. Nonderivative field redefinitions have a natural interpretation as coordinate transformations on the target manifold. General field redefinitions, which may involve derivatives,…
We verify that the dilaton together with one exactly marginal field, form a moduli space of marginal deformations of closed bosonic string field theory to polynomial order five. We use the results of this successful check in order to find…
We study the fluctuation modes for lump solutions of the tachyon effective potential in p-adic open string theory. We find a discrete spectrum with equally spaced mass squared levels. We also find that the interactions derived from this…