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Selected topics in string field theory and physics of D-branes
Vošmera, Jakub ; Schnabl, Martin (advisor) ; Erler, Theodore (referee) ; Sachs, Ivo (referee)
We discuss certain aspects of string field theory and its applications in exploring the land- scape of classical string theory vacua. We start by giving a brief overview of various tree-level string field theories, as well as of some relevant mathematical background. As a byproduct of our general discussion of observables, we present a new gauge-invariant quantity for the A∞ formulation of open superstring field theory. Putting particular emphasis on perturba- tive methods, we proceed to review in detail the construction of tree-level effective actions governing the dynamics of a certain subset of degrees of freedom. In light of recent devel- opments, we also discuss efficient methods for evaluating certain vertices of zero-momentum effective actions for open superstring and heterotic string field theories in the presence of a global N = 2 worldsheet superconformal symmetry. We show how to apply this perturbative approach to study dynamics of the D(−1)/D3 system (both with and without a B-field), while also discussing a number of more complicated Dp-brane configurations. At generic points in their moduli spaces, such bound states of Dp-branes clearly cannot be described in terms of simple Dirichlet or Neumann boundary conditions. The rest of this thesis is therefore devoted to developing analytic...
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Časově závislé procesy v teorii strun
Jiroušek, Pavel ; Schnabl, Martin (advisor) ; Novotný, Jiří (referee)
String field theory is a second quantized approach to string theory able to describe off-shell processes like transition between vacua, so-called tachyon condensation, and its dynamics. In this work, we review the necessary tools and ingredients needed to formulate such theory for open bosonic string theory. Namely, we introduce elementary conformal field theory methods and some basics of perturbative string theory. We then recognize the kinetic term of string field action from on-shell condition of the perturbative string and axiomatically introduce an algebraic structure on its Hilbert space to construct interaction terms. We briefly discuss the connection of classical string field theory solutions with various string field backgrounds and present means of reconstructing the background from a given solution by calculating the boundary state. We show that such backgrounds act like a source of open string states. We conclude by calculation of such boundary state for a solution representing light-like tachyon rolling. Powered by TCPDF (www.tcpdf.org)
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Ising Model Boundary States from String Field Theory
Rapčák, Miroslav ; Schnabl, Martin (advisor) ; Novotný, Jiří (referee)
The Ising model is widely studied model in statistical physics. In this thesis, we review methods used to solve it and we concentrate on the state at the critical temperature, where the system exhibits phase transition and can be described by means of conformal field theory (CFT). This description comes with a new insight into the problem and enables to study boundary effects. Critical behavior for systems with boundaries is often described by conformally invariant boundary conditions. Classification of all boundary CFTs still remains an open problem. We discuss methods developed recently in string field theory (SFT) proposing a new approach and we illustrate it on the Ising model. Knowing a solution to the SFT equations of motion, one can construct corresponding boundary state describing consistent conformally invariant boundary condition. We have formulated SFT for the Ising model, found new solutions numerically, and constructed corresponding boundary states. This procedure avoids solving difficult sewing constraints and results agree with exact values. Unlike the renormalization group approach, where we are limited by the g-theorem, we can construct also states with higher energy. Conformal defects and correspondence with free boson on S^1/Z_2 orbifold is also discussed. This thesis is based on...
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Selected topics in string field theory and physics of D-branes
Vošmera, Jakub ; Schnabl, Martin (advisor) ; Erler, Theodore (referee) ; Sachs, Ivo (referee)
We discuss certain aspects of string field theory and its applications in exploring the land- scape of classical string theory vacua. We start by giving a brief overview of various tree-level string field theories, as well as of some relevant mathematical background. As a byproduct of our general discussion of observables, we present a new gauge-invariant quantity for the A∞ formulation of open superstring field theory. Putting particular emphasis on perturba- tive methods, we proceed to review in detail the construction of tree-level effective actions governing the dynamics of a certain subset of degrees of freedom. In light of recent devel- opments, we also discuss efficient methods for evaluating certain vertices of zero-momentum effective actions for open superstring and heterotic string field theories in the presence of a global N = 2 worldsheet superconformal symmetry. We show how to apply this perturbative approach to study dynamics of the D(−1)/D3 system (both with and without a B-field), while also discussing a number of more complicated Dp-brane configurations. At generic points in their moduli spaces, such bound states of Dp-branes clearly cannot be described in terms of simple Dirichlet or Neumann boundary conditions. The rest of this thesis is therefore devoted to developing analytic...
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Level Truncation Approach to Open String Field Theory
Kudrna, Matěj ; Schnabl, Martin (advisor) ; Erler, Theodore (referee) ; Kishimoto, Isao (referee)
Given a D-brane background in string theory (or equivalently boundary conditions in a two dimensional conformal field theory), classical solutions of open string field theory equations of motion are conjectured to describe new D-brane backgrounds (boundary conditions). In this thesis we study these solutions in the bosonic open string field theory using the level truncation approach, which is a numerical approach where the string field is truncated to a finite number of degrees of freedom. We start with a review of the theoretical background and numerical methods which are needed in the level truncation approach and then we discuss solutions in several different back- grounds. First we discuss universal solutions, which do not depend on the open string back- ground, then we analyze solutions of the free boson theory compactified on a circle or on a torus, then marginal solutions in three different approaches and finally solutions in theories which in- clude the A-series of Virasoro minimal models. In addition to known D-branes, we find so-called exotic solutions which potentially describe yet unknown boundary states. 1
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Časově závislé procesy v teorii strun
Jiroušek, Pavel ; Schnabl, Martin (advisor) ; Novotný, Jiří (referee)
String field theory is a second quantized approach to string theory able to describe off-shell processes like transition between vacua, so-called tachyon condensation, and its dynamics. In this work, we review the necessary tools and ingredients needed to formulate such theory for open bosonic string theory. Namely, we introduce elementary conformal field theory methods and some basics of perturbative string theory. We then recognize the kinetic term of string field action from on-shell condition of the perturbative string and axiomatically introduce an algebraic structure on its Hilbert space to construct interaction terms. We briefly discuss the connection of classical string field theory solutions with various string field backgrounds and present means of reconstructing the background from a given solution by calculating the boundary state. We show that such backgrounds act like a source of open string states. We conclude by calculation of such boundary state for a solution representing light-like tachyon rolling. Powered by TCPDF (www.tcpdf.org)
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Ising Model Boundary States from String Field Theory
Rapčák, Miroslav ; Schnabl, Martin (advisor) ; Novotný, Jiří (referee)
The Ising model is widely studied model in statistical physics. In this thesis, we review methods used to solve it and we concentrate on the state at the critical temperature, where the system exhibits phase transition and can be described by means of conformal field theory (CFT). This description comes with a new insight into the problem and enables to study boundary effects. Critical behavior for systems with boundaries is often described by conformally invariant boundary conditions. Classification of all boundary CFTs still remains an open problem. We discuss methods developed recently in string field theory (SFT) proposing a new approach and we illustrate it on the Ising model. Knowing a solution to the SFT equations of motion, one can construct corresponding boundary state describing consistent conformally invariant boundary condition. We have formulated SFT for the Ising model, found new solutions numerically, and constructed corresponding boundary states. This procedure avoids solving difficult sewing constraints and results agree with exact values. Unlike the renormalization group approach, where we are limited by the g-theorem, we can construct also states with higher energy. Conformal defects and correspondence with free boson on S^1/Z_2 orbifold is also discussed. This thesis is based on...
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