Simulations of gamma-ray burst afterglows with a relativistic kinetic code

This paper introduces a kinetic code that simulates gamma-ray burst (GRB) afterglow emission from the external forward shock and presents examples of some of its applications. One interesting research topic discussed in the paper is the high-energy radiation produced by Compton scattering of the prompt GRB photons against the shock-accelerated electrons. The difference between the forward shock emission in a wind-type and a constant-density medium is also studied, and the emission due to Maxwellian electron injection is compared to the case with pure power-law electrons. The code calculates the time-evolving photon and electron distributions in the emission region by solving the relativistic kinetic equations for each particle species. For the first time, the full relativistic equations for synchrotron emission/absorption, Compton scattering, and pair production/annihilation were applied to model the forward shock emission. The synchrotron self-absorption thermalization mechanism, which shapes the low-energy end of the electron distribution, was also included in the electron equation. The simulation results indicate that inverse Compton scattering of the prompt GRB photons can produce a luminous TeV emission component, even when pair production in the emission region is taken into account. This very high-energy radiation may be observable in low-redshift GRBs. The test simulations also show that the low-energy end of a pure power-law distribution of electrons can thermalize owing to synchrotron self-absorption in a wind-type environment, but without an observable impact on the radiation spectrum. Moreover, a flattening in the forward shock X-ray light curve may be expected when the electron injection function is assumed to be purely Maxwellian instead of a power law.Comment: 16 pages, 11 figures, accepted for publication in A&

Simulations of gamma-ray burst afterglows with a relativistic kinetic code

Aims. This paper introduces a kinetic code that simulates gamma-ray burst (GRB) afterglow emission from the external forward shock and presents examples of some of its applications. One interesting research topic discussed in the paper is the high-energy radiation produced by Compton scattering of the prompt GRB photons against the shock-accelerated electrons. The difference between the forward shock emission in a wind-type and a constant-density medium is also studied, and the emission due to Maxwellian electron injection is compared to the case with pure power-law electrons. Methods. The code calculates the time-evolving photon and electron distributions in the emission region by solving the relativistic ki- netic equations for each particle species. For the first time, the full relativistic equations for synchrotron emission/absorption, Compton scattering, and pair production/annihilation were applied to model the forward shock emission. The synchrotron self-absorption ther- malization mechanism, which shapes the low-energy end of the electron distribution, was also included in the electron equation. Results. The simulation results indicate that inverse Compton scattering of the prompt GRB photons can produce a luminous TeV emission component, even when pair production in the emission region is taken into account. This very high-energy radiation may be observable in low-redshift GRBs. The test simulations also show that the low-energy end of a pure power-law distribution of electrons can thermalize owing to synchrotron self-absorption in a wind-type environment, but without an observable impact on the radiation spectrum. Moreover, a flattening in the forward shock X-ray light curve may be expected when the electron injection function is assumed to be purely Maxwellian instead of a power law. The flux during such a flattening is likely to be lower than the Swift/XRT sensitivity in the case of a constant-density external medium, but a wind environment may result in a higher flux during the shallow decay. &nbsp;</p

Evolutionary multi-stage financial scenario tree generation

Multi-stage financial decision optimization under uncertainty depends on a careful numerical approximation of the underlying stochastic process, which describes the future returns of the selected assets or asset categories. Various approaches towards an optimal generation of discrete-time, discrete-state approximations (represented as scenario trees) have been suggested in the literature. In this paper, a new evolutionary algorithm to create scenario trees for multi-stage financial optimization models will be presented. Numerical results and implementation details conclude the paper

Is it me or others who matter? The interplay between consumer values vis-à-vis status and affiliation motives as shapers of meat alternative interest

This study is about the role of consumers' personal values (Self-enhancement, Openness to change, Self-transcendence, and Conservation) in consumers' interest towards meat alternatives. In addition, the underlying role of two social motives, status and group affiliation are analysed. A conceptual model with hypotheses was developed and validated, and the hypotheses were tested through PLS-SEM with data from four European countries (Finland, the UK, Germany, and Sweden, total N = 3600). The results show that self-focused personal values (Self-enhancement and Openness to change) are not associated with consumers’ interest towards meat alternatives. The case is different with other-focused values. Self-transcendence had a positive connection to interest while Conservation had a negative relationship. Finally, the data suggest an underlying role of social motive status between Self-enhancement and interest and the same for group affiliation between Self-transcendence and Conservation and interest. Based on the results, strategies to support meat alternative adoption such as value activation through priming, cognition and emotion-driven marketing are proposed.© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).fi=vertaisarvioitu|en=peerReviewed

The flux distribution of the three quark system in SU(3)

We study the abelian color-flux distribution of the three quark system in the maximally abelian gauge on SU(3) lattices. The distribution of the color electric field suggests $Y Ansatz$, which might be interpreted through the dual superconductor picture as the result of the vacuum pressure in the confined phase. In order to clarify the flux structure, we investigate the color electric field in the three quark system also in the monopole part and in the photon part.Comment: 3pages, 5figures, Lattice2002(topology

Four-quark flux distribution and binding in lattice SU(2)

The full spatial distribution of the color fields of two and four static quarks is measured in lattice SU(2) field theory at separations up to 1 fm at beta=2.4. The four-quark case is equivalent to a qbar q qbar q system in SU(2) and is relevant to meson-meson interactions. By subtracting two-body flux tubes from the four-quark distribution we isolate the flux contribution connected with the four-body binding energy. This contribution is further studied using a model for the binding energies. Lattice sum rules for two and four quarks are used to verify the results.Comment: 46 pages including 71 eps figures. 3D color figures are available at www.physics.helsinki.fi/~ppennane/pics