12,396 research outputs found
Two-Dimensional String Theory, Topological Field Theories and the Deformed Matrix Model
In this paper the string theory is studied from the point of view of
topological field theories. Calculations are done for arbitrary genus. A change
in the prescription is proposed, which reproduces the results of the
deformed matrix model. It is proposed that the deformed matrix model is related
to a D-series Landau-Ginzburg superpotential.Comment: 20 pages, Latex CERN-TH.7155. Minor typos correcte
Creation of Strings in D-particle Quantum Mechanics
D-particle quantum mechanics in a type I' background is reviewed. It is also
discussed how a string is created when a D-particle is taken through a
D8-brane. The process is found to be dual to the creation of a D3-brane when a
NS5 and D5 brane are passed through each other.Comment: 6 pages, 2 figures. Uses espcrc2.sty. Talk given at STRINGS'9
Bacillus based biocontrol on Brassica
Many bacterial strains have been shown to mediate protection to biotic stress and promote growth of plants. Different bacteria can mediate protection in different ways e.g. by inhibition, competition or increasing plant resistance. Examples of bacteria that mediate protection to plants include different Pseudomonas, Serratia and Bacillus strains. Bacillus strains have one major advantage toward other biocontrol strains and that is the ability to form spores that are resilient against chemicals and mechanical damage. I have studied the effect of four closely related Bacillus strains on plants in two different projects, one concerned with oilseed rape (Brassica napus) and the other using Arabidopsis thaliana to allow mechanistic studies of the interaction. The bacterial strains are all classified as Bacillus amyloliquefaciens. These bacterial strains have been tested for phenological effects on plants and for plant protection towards pathogens like Alternaria brassicae, Botrytis cinerea, Leptosphaeria maculans, and Verticillium longisporum. Production of antifungal compounds by the strains and the effects on the different pathogens were investigated. Two potential candidates for biocontrol were identified. Both Bacillus strains were found to provide significant protection of oilseed rape against the four pathogens. The effects of Bacillus treatment on the B. napus transcriptome were studied using the cDNA-AFLP technique. Bacillus priming had strong systemic effects on leaf transcripts but small effects on roots. This far 65 differentially expressed plant genes have been identified due to Bacillus treatment, of which many seem related to metabolism. The effect of Bacillus seed treatment has also been studied on Arabidopsis. Significant protection was achieved also here using the same two strains toward Alternaria and Leptosphaeria as well as Pseudomonas syringae as pathogens. Arabidopsis signalling mutant studies showed that functional jasmonic acid (JA) and ethylene (Et) signalling as well as Npr1 were needed for Bacillus biocontrol. Expression levels of marker genes depending on these signalling pathways showed no increase upon Bacillus treatment, while an increase of the JA dependent marker occurred after Bacillus treated plants were infected by P. syringae. Altogether, Bacillus primed biocontrol seems to be based on induced systemic resistance (ISR)
A Matrix Model Black Hole
In this paper the matrix model deformed by a piece is
discussed. Tachyon correlation functions are calculated up to genus two using
methods similar to those for the undeformed case. The possible connection with
the two dimensional black hole is also considered. In particular, restrictions
on naked singularities imposed by the matrix model are found.Comment: 15 pages, Latex, 2 figures available on request, CERN-TH.6916/93.
Minor typos correcte
Constraining dark energy
In this paper we propose a mechanism that protects theories violating a
holographic bound suggested in arXiv:1203.5476 from developing accelerated
expansion. The mechanism builts on work on transplanckian physics, and a
non-trivial choice of vacuum states. If correct, it lends further support for
detectable signatures in the CMBR signalling new physics.Comment: 8 pages. arXiv admin note: text overlap with arXiv:astro-ph/0606474.
Minor misprints correcte
The Scattering of Strings in a Black-Hole Background
In this paper, correlation functions of tachyons in the two-dimensional
black-hole are studied. The results are shown to be consistent with the
prediction of the deformed matrix model.Comment: 10 pages, Latex, CERN-TH.7240/9
Black Hole Uncertainties
In this work the quantum theory of two dimensional dilaton black holes is
studied using the Wheeler De Witt equation. The solutions correspond to wave
functions of the black hole. It is found that for an observer inside the
horizon, there are uncertainty relations for the black hole mass and a
parameter in the metric determining the Hawking flux. Only for a particular
value of this parameter, can both be known with arbitrary accuracy. In the
generic case there is instead a relation which is very similar to the so called
string uncertainty relation.Comment: 22 pages, Changes: Additions to acknowledgements and reference
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