Triangle Seminars
Monday, 27 Mar 2006
Branch points in the complex energy plane
Ingrid Rotter
(Max Planck Institute Dresden)
Abstract:
The Hamiltonian of an open quantum system is non-Hermitian. Its eigenvalues and eigenfunctions are complex and energy dependent. They determine the spectroscopic properties of the system. The eigenvalues may cross in the complex energy plane. The crossing points are branch points that separate the scenario with avoided level crossings from that without any crossing in the complex energy plane. Mathematically, the first case is characterized by level repulsion, the second one by widths bifurcation. The topology of the branch points is different from that of diabolic points: the geometric phase is twice the Berry phase. Physically, the branch points in the complex energy plane cause some stabilization of the system and reduce the phase rigidity of the scattering wave function.
The Hamiltonian of an open quantum system is non-Hermitian. Its eigenvalues and eigenfunctions are complex and energy dependent. They determine the spectroscopic properties of the system. The eigenvalues may cross in the complex energy plane. The crossing points are branch points that separate the scenario with avoided level crossings from that without any crossing in the complex energy plane. Mathematically, the first case is characterized by level repulsion, the second one by widths bifurcation. The topology of the branch points is different from that of diabolic points: the geometric phase is twice the Berry phase. Physically, the branch points in the complex energy plane cause some stabilization of the system and reduce the phase rigidity of the scattering wave function.
Posted by: CityU
Thursday, 30 Mar 2006
Solving the open string field theory
Martin Schnabl
(CERN)
Abstract:
I will describe a new formulation of Witten's open bosonic string field
theory based on non-standard world-sheet parametrization. The theory
dramatically simplifies and the long-searched-for tachyon vacuum can be
explicitly constructed. This allows us to find a proof for one of the
Sen's conjectures relating the energy of the tachyon solution to the
tension of the D25-brane.
I will describe a new formulation of Witten's open bosonic string field
theory based on non-standard world-sheet parametrization. The theory
dramatically simplifies and the long-searched-for tachyon vacuum can be
explicitly constructed. This allows us to find a proof for one of the
Sen's conjectures relating the energy of the tachyon solution to the
tension of the D25-brane.
Posted by: IC
K-string: a Mini Review
Adi Armoni
(Swansea)