230 research outputs found
Time-dependent backgrounds of two dimensional string theory from the matrix model
The aim of this paper is to use correspondence between solutions in the
matrix model collective field theory and coupled dilaton-gravity to a massless
scalar field. First, we obtain the incoming and outgoing fluctuations for the
time-dependent backgrounds with the lightlike and spacelike boundaries. In the
case of spacelike boundaries, we have done here for the first time. Then by
using the leg-pole transformations we find corresponding tachyon field in two
dimensional string theory for lightlikes and spacelikes boundary.Comment: 10 page
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
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
Brane Intersections in the Presence of a Worldvolume Electric Field
The study of brane intersections has provided important insights into a
possible non-commutative structure of spacetime geometry. In this paper we
focus on the D1D3 system. We compare the D1 and D3 descriptions of the
interesection and search for non-static solutions of the D3D1 funnel
equations in the presence of a worldvolume electric field. We find that the D1
and D3 descriptions do not agree. We find time dependent solutions that are a
natural generalization of those found without the electric field.Comment: 10 page
Condensing Momentum Modes in 2-d 0A String Theory with Flux
We use a combination of conformal perturbation theory techniques and matrix
model results to study the effects of perturbing by momentum modes two
dimensional type 0A strings with non-vanishing Ramond-Ramond (RR) flux. In the
limit of large RR flux (equivalently, mu=0) we find an explicit analytic form
of the genus zero partition function in terms of the RR flux and the
momentum modes coupling constant alpha. The analyticity of the partition
function enables us to go beyond the perturbative regime and, for alpha>> q,
obtain the partition function in a background corresponding to the momentum
modes condensation. For momenta such that 0<p<2 we find no obstruction to
condensing the momentum modes in the phase diagram of the partition function.Comment: 22 page
Survivin antiapoptotic gene expression as a prognostic factor in non-small cell lung cancer: in situ hybridization study.
Survivin is an inhibitor of apoptosis that plays a significant role in cell cycle regulation and is important for survival prognosis in many neoplasms. Survivin expression was assessed by in situ hybridization (ISH) in 60 consecutive patients (54 males and 4 females) with NSCLC treated between 1993 and 1997. The examined patients had IIB and IIIA stage according to TNM system. In all cases the chemotherapy with cisplatin and etoposide (2 cycles) was administered prior the surgery; in patients responding to the therapy one more cycle was applied. Survivin gene overexpression was observed in 35 patients (58.3%). There was no correlation between survivin mRNA level and histological type of tumor, stage of cell differentiation, stage of disease according to TNM classification, performance status according to WHO and number of chemotherapy regimens administered (p > 0.05). However, the correlation between survivin gene expression and response to the chemotherapy was statistically significant (p = 0.04). Statistical analysis showed that median survival in patients with survivin gene overexpression was shorter (14.0 months) as compared to patients with no expression (60.0 months; p = 0.00002). In survival assessment by means of Kaplan-Meier test, 14.3% of five-year survival was achieved in the former group versus 60% in the latter (p = 0.00003). Univariate analysis (log-rank test) showed that significant independent prognostic factors in NSCLC included: stage of the disease according to TNM classification (p = 0.006), response to chemotherapy (p = 0.005) and pattern of survivin gene expression (p = 0.00003). Multivariate analysis utilizing Cox's model showed that for survival assessment the stage according to TNM, response to the chemotherapy and survivin expression estimated by means of ISH are of statistical significance (p=0.00001). The calculated predictive values showed that ISH technique was quite accurate in assessment of five-year survival. Our data show that survivin expression may be used as a prognostic factor and a target for therapy
c < 1 String from Two Dimensional Black Holes
We study a topological string description of the c < 1 non-critical string
whose matter part is defined by the time-like linear dilaton CFT. We show that
the topologically twisted N=2 SL(2,R)/U(1) model (or supersymmetric 2D black
hole) is equivalent to the c < 1 non-critical string compactified at a specific
radius by comparing their physical spectra and correlation functions. We
examine another equivalent description in the topological Landau-Ginzburg model
and check that it reproduces the same scattering amplitudes. We also discuss
its matrix model dual description.Comment: 36 pages, harvmac; acknowledgements, comments and references adde
Energy Quantisation in Bulk Bouncing Tachyon
We argue that the closed string energy in the bulk bouncing tachyon
background is to be quantised in a simple manner as if strings were trapped in
a finite time interval. We discuss it from three different viewpoints; (1) the
timelike continuation of the sinh-Gordon model, (2) the dual matrix model
description of the (1+1)-dimensional string theory with the bulk bouncing
tachyon condensate, (3) the c_L=1 limit of the timelike Liouville theory with
the dual Liouville potential turned on. There appears to be a parallel between
the bulk bouncing tachyon and the full S-brane of D-brane decay. We find the
critical value \lambda_c of the bulk bouncing tachyon coupling which is
analogous to \lambda_o=1/2 of the full S-brane coupling, at which the system is
thought to be at the bottom of the tachyon potential.Comment: 25 pages, minor changes, one reference adde
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