Pending Evolution of Grammars

The classic approach to grammar manipulation is based on instant processing of grammar edits, which limits the kinds of grammar evolution scenarios that can be expressed with it. Treating transformation preconditions as guards poses limitations on concurrent changes of the same grammar, on reuse of evolution scripts, on expressing optionally executed steps, on batch processing and optimization of them, etc. We propose an alternative paradigm of evolution, where a transformation can be scheduled for later execution based on its precondition. This kind of extreme evolution can be useful for expressing scenarios that are impossible to fully automate within the classic or the negotiated transformation paradigms

Parity nonconservation effect in the resonance elastic electron scattering on heavy He-like ions

We investigate the parity nonconservation effect in the elastic scattering of polarized electrons on heavy He-like ions, being initially in the ground state. The enhancement of the parity violation is achieved by tuning the energy of the incident electron in resonance with quasidegenerate doubly-excited states of the corresponding Li-like ion. We consider two possible scenarios. In the first one we assume that the polarization of the scattered electron is measured, while in the second one it is not detected.Comment: 13 pages, 3 figures, 2 table

Language Convergence Infrastructure

The process of grammar convergence involves grammar extraction and transformation for structural equivalence and contains a range of technical challenges. These need to be addressed in order for the method to deliver useful results. The paper describes a DSL and the infrastructure behind it that automates the convergence process, hides negligible back-en

Relativistic mask method for electron momentum distributions after ionization of hydrogen-like ions in strong laser fields

Wavefunction-splitting or mask method, widely used in the non-relativistic calculations of the photoelectron angular distributions, is extended to the relativistic domain within the dipole approximation. Since the closed-form expressions for the relativistic Volkov states are not available within the dipole approximation, we build such states numerically solving a single second-order differential equation. We calculate the photoelectron energy spectra and angular distributions for highly charged ions under different ionization regimes with both the direct and the relativistic mask methods. We show that the relativistic mask method works very well and reproduces the electron energy and angular distributions calculated by the direct method in the energy range where both methods can be used. On the other hand, the relativistic mask method can be applied for longer laser pulses and/or higher photoelectron energies where the direct method may have difficulties