Use this URL to cite or link to this record in EThOS:  http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598293 
Title:  Instabilities in nonperturbative string theory  
Author:  Dasgupta, T.  
Awarding Body:  University of Cambridge  
Current Institution:  University of Cambridge  
Date of Award:  2001  
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Abstract:  
In chapter 3 the relation between two different classes of perturbative nonBPS bispinor states of heterotic string theory and certain nonperturbative nonBPS Dbrane states of the dual type I' theory is exhibited. The domains of stability of these states as well as their decay products in both theories are determined and shown to agree with the duality map. In chapter 4 the effects of the nonBPS Dinstanton in type I theory and its Mtheory origin is described. The starting point is the treelevel amplitude for the scattering of two gauge particles in the HořavaWitten formulation of Mtheory. At low momenta this exactly reproduces the corresponding treelevel scattering amplitude of the E_{8} x E_{8} heterotic string theory. After compactification to nine dimensions this amplitude is used to describe the scattering of two massive SO(16) spinor states. The nonBPS Dinstanton component of this amplitude is explicitly determined from this expression. In chapter 5 the renormalization group method is used to study tachyon condensation on bosonic D25brane. The decay of the D25brane is controlled by a nearby IR fixed point representing D24branes. The boundary entropy corresponding to the D24brane tension is calculated in leading order in perturbation theory and agrees with the expected result to an accuracy of 8%. Multicritical behaviour of the IR theory suggests that the end point of the flow represents a configuration of two D24branes. An analogy with Kondo physics is discussed. Chapter 6 ongoing developments in the context of little string theory and matrix theory.


Supervisor:  Not available  Sponsor:  Not available  
Qualification Name:  Thesis (Ph.D.)  Qualification Level:  Doctoral  
EThOS ID:  uk.bl.ethos.598293  DOI:  Not available  
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