arXiv subjects

Janek Kozicki

Publications and source records attributed to Janek Kozicki.

5 recordsLinked to original sources

arXiv2026

Integral Hilbert spaces and the dynamics of loop quantum cosmos

Polymer quantization program applied in Loop Quantum Gravity/Cosmology leads to nonseparable Hilbert spaces. Commonly, one sidesteps this problem by singling out and working with a separable superselection sector. This is however often no longer accessible in more involved models beyond isotropic ones. In an alternative approach one builds a separable Hilbert space as an integral over all available sectors. Here we test the dynamics following from the latter on the example of a flat isotropic Universe admitting negative cosmological constant and a massless scalar field. There, numerical evolution of (initially) semiclassical states shows that there is no relevant difference in their long term semiclassicality properties in comparison to those in a single sector approach. Further, the older (problem-specific) numerical methods are compared against an application of more common and more efficient standard tools (eigen library).

gr-qc↗

arXiv2023

Very accurate time propagation of coupled Schrödinger equations for femto- and attosecond physics and chemistry, with C++ source code

In this article, I present a very fast and high-precision (up to 33 decimal places) C++ implementation of the semi-global time propagation algorithm for a system of coupled Schrödinger equations with a time-dependent Hamiltonian. It can be used to describe time-dependent processes in molecular systems after excitation by femto- and attosecond laser pulses. It also works with an arbitrary user supplied Hamiltonian and can be used for nonlinear problems. The semi-global algorithm is briefly presented, the C++ implementation is described and five sample simulations are shown. The accompanying C++ source code package is included. The high precision benchmark (long double and float128) shows the estimated calculation costs. The presented method turns out to be faster and more accurate than the global Chebyshev propagator.

physics.chem-ph↗

arXiv2023

Optimization of the Femtosecond Laser Impulse for Excitation and the Spin-Orbit Mediated Dissociation in the NaRb Dimer

We study the dynamics of multiple coupled states under the influence of an arbitrary time-dependent external field to investigate the femtosecond laser-driven excitation and the spin-orbit mediated dissociation in the NaRb dimer. In this process, the dimer is excited from the ground triplet state $1^3Σ^+$ to the $1^3Π$ state using the femtosecond laser impulse and the spin-orbit coupling between the $1^3Π$ and $2^1Σ^+$ states results in the singlet-triplet transition. The laser impulse parameters are optimised to obtain maximum yield in electronic states correlating with the first excited atomic asymptote. We observe the detailed population statistics and power-law decay of these states. Finally, the analysis of the population oscillations allows us to determine the optimal time delay for dumping the molecule to its absolute ground state.

physics.chem-ph↗

arXiv2023

Yade Documentation

Yade is an extensible open-source framework for discrete numerical models, focused on the Discrete Element Method. The computation parts are written in c++ using a flexible object model and allowing independent implementation of new algorithms and interfaces. Python is used for rapid and concise scene construction, simulation control, postprocessing and debugging. Yade is located at yade-dem.org, which contains this documentation. Development is kindly hosted on launchpad and GitLab ; they are used for source code, bug tracking and source downloads and more. Building, regression tests and packages distribution are hosted on servers of the Grenoble Geomechanics group at Laboratoire 3SR, UMS Gricad and Gdańsk University of Technology. Yade supports high precision calculations and Python 3. The development branch is on GitLab.

physics.comp-ph↗

arXiv2021

Implementation of high-precision computation capabilities into the open-source dynamic simulation framework YADE

This paper deals with the implementation of arbitrary precision calculations into the open-source discrete element framework YADE published under the GPL-2+ free software license. This new capability paves the way for the simulation framework to be used in many new fields such as quantum mechanics. The implementation details and associated gains in the accuracy of the results are discussed. Besides the "standard" double (64 bits) type, support for the following high-precision types is added: long double (80 bits), float128 (128 bits), mpfr_float_backend (arbitrary precision) and cpp_bin_float (arbitrary precision). Benchmarks are performed to quantify the additional computational cost involved with the new supported precisions. Finally, a simple calculation of a chaotic triple pendulum is performed to demonstrate the new capabilities and the effect of different precisions on the simulation result.

physics.comp-ph↗