Frankfurt Institute for Advanced Studies

About: Frankfurt Institute for Advanced Studies is a facility organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Baryon & Quark–gluon plasma. The organization has 798 authors who have published 2733 publications receiving 82799 citations. The organization is also known as: FIAS.

P3M algorithm for dipolar interactions

Abstract: An extension to the P3M algorithm for electrostatic interactions is presented that allows to efficiently compute dipolar interactions in periodic boundary conditions. Theoretical estimates for the root-mean-square error of the forces, torques, and the energy are derived. The applicability of the estimates is tested and confirmed in several numerical examples. A comparison of the computational performance of the new algorithm to a standard dipolar-Ewald summation methods shows a performance crossover from the Ewald method to the dipolar P3M method for as few as 300 dipolar particles. In larger systems, the new algorithm represents a substantial improvement in performance with respect to the dipolar standard Ewald method. Finally, a test comparing point-dipole-based and charged-pair based models shows that point-dipole-based models exhibit a better performance than charged-pair based models.

An iterative, fast, linear-scaling method for computing induced charges on arbitrary dielectric boundaries.

Abstract: Simulating coarse-grained models of charged soft-condensed matter systems in presence of dielectric discontinuities between different media requires an efficient calculation of polarization effects. This is almost always the case if implicit solvent models are used near interfaces or large macromolecules. We present a fast and accurate method (ICC⋆) that allows to simulate the presence of an arbitrary number of interfaces of arbitrary shape, each characterized by a different dielectric permittivity in one-, two-, and three-dimensional periodic boundary conditions. The scaling behavior and accuracy of the underlying electrostatic algorithms allow to choose the most appropriate scheme for the system under investigation in terms of precision and computational speed. Due to these characteristics the method is particularly suited to include nonplanar dielectric boundaries in coarse-grained molecular dynamics simulations.

Nonthermal p/π ratio at LHC as a consequence of hadronic final state interactions.

Abstract: Recent LHC data on $\mathrm{Pb}+\mathrm{Pb}$ reactions at ${\sqrt{s}}_{NN}=2.7\text{ }\text{ }\mathrm{TeV}$ suggests that the $p/\ensuremath{\pi}$ is incompatible with thermal models. We explore several hadron ratios ($K/\ensuremath{\pi}$, $p/\ensuremath{\pi}$, $\ensuremath{\Lambda}/\ensuremath{\pi}$, $\ensuremath{\Xi}/\ensuremath{\pi}$) within a hydrodynamic model with a hadronic after burner, namely the ultrarelativistic quantum molecular dynamics model 3.3, and show that the deviations can be understood as a final state effect. We propose the $p/\ensuremath{\pi}$ as an observable sensitive on whether final state interactions take place or not. The measured values of the hadron ratios do then allow us to gauge the transition energy density from hydrodynamics to the Boltzmann description. We find that the data can be explained with transition energy densities of $840\ifmmode\pm\else\textpm\fi{}150\text{ }\text{ }\mathrm{MeV}/{\mathrm{fm}}^{3}$.

Distributions of positron-emitting nuclei in proton and carbon-ion therapy studied with GEANT4.

Abstract: Depth distributions of positron-emitting nuclei in PMMA phantoms are calculated within a Monte Carlo model for heavy-ion therapy (MCHIT) based on the GEANT4 toolkit (version 8.0). The calculated total production rates of (11)C, (10)C and (15)O nuclei are compared with experimental data and with corresponding results of the FLUKA and POSGEN codes. The distributions of e(+) annihilation points are obtained by simulating radioactive decay of unstable nuclei and transporting positrons in the surrounding medium. A finite spatial resolution of the positron emission tomography (PET) is taken into account in a simplified way. Depth distributions of beta(+)-activity as seen by a PET scanner are calculated and compared to available data for PMMA phantoms. The obtained beta(+)-activity profiles are in good agreement with PET data for proton and (12)C beams at energies suitable for particle therapy. The MCHIT capability to predict the beta(+)-activity and dose distributions in tissue-like materials of different chemical composition is demonstrated.