46 research outputs found
Collective Field Description of Matrix Cosmologies
We study the Das-Jevicki collective field description of arbitrary classical
solutions in the c=1 matrix model, which are believed to describe nontrivial
spacetime backgrounds in 2d string theory. Our analysis naturally includes the
case of a Fermi droplet cosmology: a finite size droplet of Fermi fluid, made
up of a finite number of eigenvalues. We analyze properties of the coordinates
in which the metric in the collective field theory is trivial, and comment on
the form of the interaction terms in these coordinates.Comment: 16 pages, 1 figure. v2: Typos corrected, JHEP styl
Rolling Tachyon Boundary State, Conserved Charges and Two Dimensional String Theory
The boundary state associated with the rolling tachyon solution on an
unstable D-brane contains a part that decays exponentially in the asymptotic
past and the asymptotic future, but it also contains other parts which either
remain constant or grow exponentially in the past or future. We argue that the
time dependence of the latter parts is completely determined by the requirement
of BRST invariance of the boundary state, and hence they contain information
about certain conserved charges in the system. We also examine this in the
context of the unstable D0-brane in two dimensional string theory where these
conserved charges produce closed string background associated with the discrete
states, and show that these charges are in one to one correspondence with the
symmetry generators in the matrix model description of this theory.Comment: LaTeX file, 37 pages; v3: references added; v4: minor change
On the S-matrix of Type 0 String Theory
The recent discovery of non-perturbatively stable two-dimensional string
backgrounds and their dual matrix models allows the study of complete
scattering matrices in string theory. In this note we adapt work of Moore,
Plesser, and Ramgoolam on the bosonic string to compute the exact S-matrices of
0A and 0B string theory in two dimensions. Unitarity of the 0B theory requires
the inclusion of massless soliton sectors carrying RR scalar charge as
asymptotic states. We propose a regularization of IR divergences and find
transition probabilities that distinguish the otherwise energetically
degenerate soliton sectors. Unstable D-branes can decay into distinct soliton
sectors.Comment: 30 pages, 6 figures, harvma
Tachyon Backgrounds in 2D String Theory
We consider the construction of tachyonic backgrounds in two-dimensional
string theory, focusing on the Sine-Liouville background. This can be studied
in two different ways, one within the context of collective field theory and
the other via the formalism of Toda integrable systems. The two approaches are
seemingly different. The latter involves a deformation of the original inverted
oscillator potential while the former does not. We perform a comparison by
explicitly constructing the Fermi surface in each case, and demonstrate that
the two apparently different approaches are in fact equivalent.Comment: 25 pages, no figure
Branes wrapping black holes as a purely gravitational dielectric effect
In this paper we give a microscopical description of certain configurations
of branes wrapping black hole horizons in terms of dielectric gravitational
waves. Interestingly, the configurations are stable only due to the
gravitational background. Therefore, this constitutes a nice example of purely
gravitational dielectric effect.Comment: 17 pages, no figures. JHEP published versio
Notes on D-branes in 2D Type 0 String Theory
In this paper we construct complete macroscopic operators in two dimensional
type 0 string theory. They represent D-branes localized in the time direction.
We give another equivalent description of them as deformed Fermi surfaces. We
also discuss a continuous array of such D-branes and show that it can be
described by a matrix model with a deformed potential. For appropriate values
of parameters, we find that it has an additional new sector hidden inside its
strongly coupled region.Comment: harvmac, 18 pages, 2 figures, references adde
Particle Production in Matrix Cosmology
We consider cosmological particle production in 1+1 dimensional string
theory. The process is described most efficiently in terms of anomalies, but we
also discuss the explicit mode expansions. In matrix cosmology the usual vacuum
ambiguity of quantum fields in time-dependent backgrounds is resolved by the
underlying matrix model. This leads to a finite energy density for the "in"
state which cancels the effect of anomalous particle production.Comment: 24 pages, 1 figure; v2: references added, minor change
The Cap in the Hat: Unoriented 2D Strings and Matrix(-Vector) Models
We classify the possible bosonic and Type 0 unoriented string theories in two
dimensions, and find their dual matrix(-vector) models. There are no RP^2 R-R
tadpoles in any of the models, but many of them possess a massless tachyon
tadpole. Thus all the models we find are consistent two-dimensional string
vacua, but some get quantum corrections to their classical tachyon background.
Where possible, we solve the tadpole cancellation condition, and find all the
tachyon tadpole-free theories.Comment: 34 pages, LaTeX; Errors corrected in some of the open string
representations in tables 1, 2 and 3. References and acknowledgments adde
Two-Dimensional Unoriented Strings And Matrix Models
We investigate unoriented strings and superstrings in two dimensions and
their dual matrix quantum mechanics. Most of the models we study have a tachyon
tadpole coming from the RP^2 worldsheet which needs to be cancelled by a
renormalization of the worldsheet theory. We find evidence that the dual matrix
models describe the renormalized theory. The singlet sector of the matrix
models is integrable and can be formulated in terms of fermions moving in an
external potential and interacting via the Calogero-Moser potential. We show
that in the double-scaling limit the latter system exhibits particle-hole
duality and interpret it in terms of the dual string theory. We also show that
oriented string theories in two dimensions can be continuously deformed into
unoriented ones by turning on non-local interactions on the worldsheet. We find
two unoriented superstring models for which only oriented worldsheets
contribute to the S-matrix. A simple explanation for this is found in the dual
matrix model.Comment: 36 pages, harvmac, 2 eps figure
Rolling tachyon solution of two-dimensional string theory
We consider a classical (string) field theory of matrix model which was
developed earlier in hep-th/9207011 and subsequent papers. This is a
noncommutative field theory where the noncommutativity parameter is the string
coupling . We construct a classical solution of this field theory and show
that it describes the complete time history of the recently found rolling
tachyon on an unstable D0 brane.Comment: 19 pages, 2 figures, minor changes in text and additional references,
correction of decay time (version to appear in JHEP.