Symplectic integration approach for metastable systems

Nonadiabatic behavior of metastable systems modeled by anharmonic Hamiltonians is reproduced by the Fokker-Planck and imaginary time Schrodinger equation scheme with subsequent symplectic integration. Example solutions capture ergodicity breaking, reassure the H-theorem of global stability [M. Shiino, Phys. Rev. A, Vol 36, pp. 2393-2411 (1987)], and reproduce spatially extended response under alternate source fields.Comment: 10 pages, 5 figure

A novel quantum field approach to photoexcited insulators

In order to predict optical properties of insulating materials under intensive laser excitation, we generalized methods of quantum electrodynamics, allowing us to simulate excitation of electrons and holes, interacting with each other and acoustic phonons. The prototypical model considers a two-band dielectric material characterized by the dispersion relations for electron and hole states. We developed a universal description of excited electrons, holes and acoustic phonons within joint quantum kinetics formalism. Illustrative solutions for the quasiparticle birth-annihilation operators, applicable at short laser pulses at 0 K, are obtained by the transition from the macroscopic description to the quantum field formalism

Application of elastostatic Green function tensor technique to electrostriction in cubic, hexagonal and orthorhombic crystals

The elastostatic Green function tensor approach, which was recently used to treat electrostriction in numerical simulation of domain structure formation in cubic ferroelectrics, is reviewed and extended to the crystals of hexagonal and orthorhombic symmetry. The tensorial kernels appearing in the expressions for effective nonlocal interaction of electrostrictive origin are derived explicitly and their physical meaning is illustrated on simple examples. It is argued that the bilinear coupling between the polarization gradients and elastic strain should be systematically included in the Ginzburg-Landau free energy expansion of electrostrictive materials.Comment: 4 page

Amidst Uncertainty–or Not? : Decision-Making in Early-Stage Software Startups

Peer reviewe

Hypotheses Elicitation in Early-Stage Software Startups Based on Cognitive Mapping

Software startups develop innovative products for which there are typically no customers to refer to elicit requirements. Often, these companies develop a set of features without a better understanding of customer needs. An experiment-based approach to validate hypotheses about the customer and market could increase their chance of success or, at least, accelerate their realization of the product worthlessness. The first step of an experiment-based approach is to elicit hypotheses to guide experiments. Software startups base their products on business assumptions, but there is a lack of understanding of how these assumptions are formed and how teams could elicit hypotheses systematically. To fill this gap, we performed an empirical study consisted of two steps. First, we explored based on which assumptions startups define their products using a multiple case study. The results indicate that these companies developed their products based on founders' assumptions derived from their previous experience. Second, we investigated cognitive mapping as a tool to elicit hypotheses systematically with two software startups. The results indicate that this approach can serve as the basis of a method to elicit hypotheses in early-stage software startups

Electronic Processes in Solid State: Dirac Framework

The present paper proposes canonical Dirac framework adapted for application to the electronic processes in solid state. The concern is a spatially periodic structure of atoms distinguished by birth and annihilation of particle states excited due to interaction with the electromagnetic field. This implies replacing the conventional energy-momentum relation specific of the canonical Dirac framework and permissible for particle physics by a case specific relation available for the solid state. The advancement is a unified and consistent mathematical framework incorporating the Hilbert space, the quantum field, and the special relativity. Essential details of the birth and annihilation of the particle states are given by an illustrative two-band model obeying basic laws of quantum mechanics, special relativity, and symmetry principles maintained from the canonical Dirac framework as a desirable property and as a prerogative for the study of the particle coupling and correlation

Finding Electron-Hole Interaction in Quantum Kinetic Framework

The article presents a quantum kinetic framework to study interacting quan¬tum systems. Having the constituting model Hamiltonians of two-band semiconductor and the photoexcited electron-hole pair, their quantum kinetic evolution has been revi-sited. Solution to this nonlinear problem of electron-hole interaction is obtained making use of the self-consistency loop between the densities of photoexcited electrons and holes and the pairwise interaction terms in the constituting model Hamiltonians. In the leading order, this approach supports the required isomorphism between the pairwise interaction and the birth and annihilation operators of the photoexcited electrons and holes as a desirable property. The approach implies the Hilbert space and the tensor product mathematical techniques as an appropriate generalization of the noninteracting electron-hole pair toward several-body systems