Closed String Emission Research Articles

New D1-D5-P geometries from string amplitudes

We derive the long range supergravity fields sourced by a D1-D5-P bound state from disk amplitudes for massless closed string emission. We suggest that since the parameter controlling the string perturbation expansion for this calculation decreases with distance from the bound state, the resulting asymptotic fields are valid even in the regime of parameters in which there is a classical black hole solution with the same charges. The supergravity fields differ from the black hole solution by multipole moments and are more general than those contained within known classes of solutions in the literature, whilst still preserving four supersymmetries. Our results support the conjecture that the black hole solution should be interpreted as a coarse-grained description rather than an exact description of the gravitational field sourced by D1-D5-P bound states in this regime of parameters.

Note on light-like tachyon condensation

In this paper closed string emission and open string pair production from the light-like rolling tachyon solution are calculated in subcritical string theory in the background of a linear dilaton. The rolling light-like tachyon represents the inhomogeneous decay of unstable D-brane. The decay rate is given by the imaginary part of annulus diagram which can be calculated using the boundary state/sigma-model method. It is found that the decay rate is finite in the open string ultraviolet region and depends on tachyon profile in the open string infrared region.

ZZ brane decay inDdimensions

In this paper we consider the ZZ brane decay in a D-dimensional background with a linear dilaton and a Liouville potential switched on. We mainly calculate the closed string emission rate during the decay process. For the case of a spacelike dilaton we find a similar Hagedorn behavior, in the closed string UV region, with the brane decay in the usual 26d and 2d bosonic string theory. This means that all of the energy of the original brane converts into outgoing closed strings. In the IR region the result is finite. We also give some comments about the case that the dilaton is null.

Closed Superstring Emission from Rolling Tachyon Backgrounds

We compute the lowest components of the Type II Ramond-Ramond boundary state for the tachyon profile $T (X) = \lambda e ^{X ^ 0/\sqrt{2}}$ by direct path integral evaluation. The calculation is made possible by noting that the integrals involved in the requisite disk one-point functions reduce to integrals over the product group manifold $U (n)\times U (m)$. We further note that one-point functions of more general closed string operators in this background can also be related to $U (n)\times U (m)$ group integrals. Using this boundary state, we compute the closed string emission from a decaying unstable D$p$-brane of Type II string theory. We also discuss closed string emission from the tachyon profile $T (X) =\lambda\cosh (X ^ 0/\sqrt{2})$. We find in both cases that the total number of particles produced diverges for $p = 0$, while the energy radiated into closed string modes diverges for $p\leq 2$, in precise analogy to the bosonic case.

Dbrane Near NS5-branes: with Electromagnetic Field

We study the Dp-brane dynamics near NS5-branes with constant electromagnetic field. In the framework of effective Dirac-Born-Infeld action, we investigate the effect of the electromagnetic field on the Dp-brane dynamics. The radial motion of the Dp-brane on the transverse directions of NS5-branes can be mapped to a rolling tachyon in a constant NS B-munu background. In the near throat region, the classical motion can be identified with the rescaled hairpin. After constructing the boundary state of the rescaled hairpin, we discuss the closed string emission of the Dp-brane and find that the energy of the closed string emission is always finite in the presence of constant electric field. Taking the winding strings into account, the emitted energy is divergent, indicating that the emitted winding strings carry away most of the energy.

Solvable time-dependent model and rolling closed string tachyon

We investigate the $SL(2,\mathbb{R})/U(1)$ WZW model with level $0<k<2$ as a solvable time-dependent background in string theory. This model is expected to be dual to the one describing a rolling closed string tachyon with a timelike linear dilaton. We examine its exact metric and minisuperspace wave functions. Two point functions and the one-loop vacuum amplitude are computed and their relation to the closed string emission is discussed. Comparing with the results from the minisuperspace approximation, we find a physical interpretation of our choice to continue the Euclidean model into the Lorentzian one. Three point functions are also examined.

A time-dependent brane in a cosmological background

We study a moving D-brane in a time-dependent background. There is particle production both because of non-trivial cosmological evolution, and by closed string emission from the brane that gradually decelerates due to a gain in mass. The particular model under study is a D0-brane in an SL(2,R)/U(1) cosmology -- the techniques used extend to other backgrounds.

One-loop evolution of a rolling tachyon

We study the time evolution of the one-loop diagram in Sen's rolling tachyon background. We find that at least in the long cylinder case they grow rapidly at late time, due to the exponential growth of the timelike oscillator terms in the boundary state. This can also be interpreted as the virtual open string pair creation in the decaying brane. This behavior indicates a breakdown of this rolling tachyon solution at some point during the evolution. We also discuss the closed string emission from this one-loop diagram, and the evolution of a one-loop diagram connecting a decaying brane to a stable brane, which is responsible for the physical open string creation on the stable brane.

The decay of quantum D-branes

We study the quantum decay of D0-branes in two-dimensional 0B string theory. The quantum nature of the branes provides a natural cut-off for the closed string emission rate. We find exact quantum mechanical wave functions for the decaying branes and show how one can include the effects of the Fermi sea for any string coupling (Fermi energy).

Closed String Emission from Unstable D-brane with Background Electric Field

We study the closed string emission from an unstable D$p$-brane with constant background electric field in bosonic string theory. The average total number density and the average total energy density of emitted closed strings are explicitly calculated in the presence of electric field. It is explicitly shown that the energy density in the UV region becomes finite whenever the background electric field is switched on. The energy density converted into closed strings in the presence of electric field is negligibly small compared with the D-brane tension in the weak string coupling limit.

Strings from tachyons: thec= 1 matrix reloaded

We propose a new interpretation of the c=1 matrix model as the world-line theory of N unstable D-particles, in which the hermitian matrix is provided by the non- abelian open string tachyon. For D-particles in 1+1-d string theory, we find a direct quantitative match between the closed string emission due to a rolling tachyon and that due to a rolling eigenvalue in the matrix model. We explain the origin of the double-scaling limit, and interpret it as an extreme representative of a large equivalence class of dual theories. Finally, we define a concrete decoupling limit of unstable D-particles in IIB string theory that reduces to the c=1 matrix model, suggesting that 1+1-d string theory represents the near-horizon limit of an ultra-dense gas of IIB D-particles.

UV finite brane decay

The decay of an unstable D-brane via closed string emission and open string pair production is considered in subcritical string theory with a spacelike linear dilaton. The decay rate is given by the imaginary part of the annulus, which has ambiguities corresponding to the choices of incoming closed and open string vacua. An exact expression for the full annulus diagram is computed with a natural choice of incoming vacua. It is found that the ultraviolet divergences present in critical string theory in both of these processes are absent for any nonzero spacelike dilaton. Implications for the vexing issue of the tachyon dust are discussed.

A matrix model dual of type 0B string theory in two dimensions

We propose that type 0B string theory in two dimensions admits a dual description in terms of a one dimensional bosonic matrix model of a hermitian matrix. The potential in the matrix model is symmetric with respect to the parity-like Z_2 transformation of the matrix. The two sectors in the theory, namely the NSNS and RR scalar sectors correspond to two classes of operators in the matrix model, even and odd under the Z_2 symmetry respectively. We provide evidence that the matrix model successfully reconstructs the perturbative S-matrix of the string theory, and reproduces the closed string emission amplitude from unstable D-branes. Following recent work in two dimensional bosonic string, we argue that the matrix model can be identified with the theory describing N unstable D0-branes in type 0B theory. We also argue that type 0A theory is described in terms of the quantum mechanics of brane-antibrane systems.

Opening of branes

We relate, in 10 and 11 dimensional supergravities, configurations of intersecting closed branes with vanishing binding energy to configurations where one of the branes opens and has its boundaries attached to the other. These boundaries are charged with respect to fields living on the closed brane. The latter hosts electric and magnetic charges stemming from dual pairs of open branes terminating on it. We show that charge conservation, gauge invariance and supersymmetry entirely determine these charges and these fields, which can be seen as Goldstone fields of broken supersymmetry. Open brane boundary charges can annihilate, restoring the zero binding energy configuration. This suggests emission of closed branes by branes, a generalization of closed string emission by D-branes. We comment on the relation of the Goldstone fields to matrix models approaches to M-theory.

Grassmann Algebraic Approach to the Neveu-Schwarz Model and Representation of Super-Mobius Algebra

On the basis of new integral representation proposed by Fairlie and Martin, we develop a manifestly super-gauge invariant formulation of the Neveu-Schwarz model. We show that the Fairlie-Martin representation is invariant under wider trafisformations (super-Mobius transformations) than the usual Mobius transformations. The corresponding algebra (super­ Mobius algebra) is a closed subalgebra of the super-gauge algebra. The operator formalism is reconstructed as a representation of the super-Mobius algebra. As a generalization of our formulation, we introduce closed-string emission vertices for the Neveu-Schwarz open-string which are manifestly covariant under the super-gauge transformations as well as the confotmal transformations. Finally we discuss briefly the general representation theory of .the s~per­ Mobius algebra. Unfortunately, the representation appeared in the Neveu-Schwarz model is essentially unique as the representation of the full super-gauge algebra. However, two types of_ the mass spectrum are possible.