352,095 research outputs found
Non-adiabatic transitions in multi-level systems
In a quantum system with a smoothly and slowly varying Hamiltonian, which
approaches a constant operator at times , the transition
probabilities between adiabatic states are exponentially small. They are
characterized by an exponent that depends on a phase integral along a path
around a set of branch points connecting the energy level surfaces in complex
time. Only certain sequences of branch points contribute. We propose that these
sequences are determined by a topological rule involving the Stokes lines
attached to the branch points. Our hypothesis is supported by theoretical
arguments and results of numerical experiments.Comment: 25 pages RevTeX, 9 figures and 4 tables as Postscipt file
On the complete integrability of the discrete Nahm equations
The discrete Nahm equations, a system of matrix valued difference equations,
arose in the work of Braam and Austin on half-integral mass hyperbolic
monopoles.
We show that the discrete Nahm equations are completely integrable in a
natural sense: to any solution we can associate a spectral curve and a
holomorphic line-bundle over the spectral curve, such that the discrete-time DN
evolution corresponds to walking in the Jacobian of the spectral curve in a
straight line through the line-bundle with steps of a fixed size. Some of the
implications for hyperbolic monopoles are also discussed
Optical signatures of molecular particles via mass-selected cluster spectroscopy
A new molecular beam apparatus was developed to study optical absorption in cold (less than 100 K) atomic clusters and complexes produced by their condensation with simple molecular gases. In this instrument, ionized clusters produced in a laser vaporization nozzle source are mass selected and studied with photodissociation spectroscopy at visible and ultraviolet wavelengths. This new approach can be applied to synthesize and characterize numerous particulates and weakly bound complexes expected in planetary atmospheres and in comets
- …