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Search Results: 1 - 10 of 10535 matches for " Hans Weber "
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NO2 Excited State Properties Revisited: An Effect of Extra Compactified Dimensions  [PDF]
Hans-Georg Weber
Journal of Modern Physics (JMP) , 2017, DOI: 10.4236/jmp.2017.811103
Abstract: Experiments on NO2 reveal a substructure underlying the optically excited isolated hyperfine structure (hfs) levels of the molecule. This substructure is seen in a change of the symmetry of the excited molecule and is represented by the two “states” \"\" and \"\" of a hfs-level. Optical excitation induces a transition from the ground state \"\" of the molecule to the excited state . However, the molecule evolves from \"\" to \"\" in a time τ0 ≈ 3 μs. Both \"\" and \"\" have the radiative lifetime τR ≈ 40 μs, but \"\" and \"\" differ in the degree of polarization of the fluorescence light. Zeeman coherence in the magnetic sublevels is conserved in the transition \"\"\"\", and optical coherence of \"\" and \"\" is able to affect (inversion effect) the transition \"\"
Resistance scaling at the Kosterlitz-Thouless transition
Mats Wallin,Hans Weber
Physics , 1994, DOI: 10.1103/PhysRevB.51.6163
Abstract: We study the linear resistance at the Kosterlitz-Thouless transition by Monte Carlo simulation of vortex dynamics. Finite size scaling analysis of our data show excellent agreement with scaling properties of the Kosterlitz-Thouless transition. We also compare our results for the linear resistance with experiments. By adjusting the vortex chemical potential to an optimum value, the resistance at temperatures above the transition temperature agrees well with experiments over many decades.
Simulating Spiraling Bubble Movement in the EL Approach  [PDF]
Andreas Weber, Hans-J?rg Bart, Axel Klar
Open Journal of Fluid Dynamics (OJFD) , 2017, DOI: 10.4236/ojfd.2017.73019
Abstract: Simulating the detailed movement of a rising bubble can be challenging, especially when it comes to bubble path instabilities. A solution based on the Euler Lagrange (EL) approach is presented, where the bubbles show oscillating shape and/or instable paths while computational cost are at a far lower level than in DNS. The model calculates direction, shape and rotation of the bubbles. A lateral force based on rotation and direction is modeled to finally create typical instable path lines. This is embedded in an EL simulation, which can resolve bubble size distribution, mass transfer and chemical reactions. A parameter study was used to choose appropriate model constants for a mean bubble size of 3 mm. To ensure realistic solution, validation against experimental data of single rising bubbles and bubble swarms are presented. References with 2D and also 3D analysis are taken into account to compare simulative data in terms of typical geometrical parameters and average field values.
Monte Carlo calculation of the linear resistance of a three dimensional lattice Superconductor model in the London limit
Hans Weber,Henrik Jeldtoft Jensen
Physics , 1996, DOI: 10.1103/PhysRevLett.78.2620
Abstract: We have studied the linear resistance of a three dimensional lattice Superconductor model in the London limit London lattice model by Monte Carlo simulation of the vortex loop dynamics. We find excellent finite size scaling at the phase transition. We determine the dynamical exponent $z = 1.51$ for the isotropic London lattice model.
Melosh Construction Of Relativistic Three-Quark Baryon Wave Functions
Xuepeng Sun,Hans J. Weber
Physics , 2001, DOI: 10.1142/S0217751X02009710
Abstract: A method for constructing a complete set of relativistic three-quark states in light front dynamics is implemented for the nucleon, N$^*$(1520) and N$^*$(1535). This approach facilitates constructing states containing virtual antiquarks. A physical interpretation is provided in terms of transition amplitudes from quark to quark-gluon or quark-Goldstone boson Fock states of chiral dynamics generated by flux tube breaking expected in QCD at intermediate distances.
Monte Carlo calculation of the current-voltage characteristics of a two dimensional lattice Coulomb gas
Hans Weber,Mats Wallin,Henrik Jeldtoft Jensen
Physics , 1996, DOI: 10.1103/PhysRevB.53.8566
Abstract: We have studied the nonlinear current-voltage characteristic of a two dimensional lattice Coulomb gas by Monte Carlo simulation. We present three different determinations of the power-law exponent $a(T)$ of the nonlinear current-voltage characteristic, $V \sim I^{a(T)+1}$. The determinations rely on both equilibrium and non-equilibrium simulations. We find good agreement between the different determinations, and our results also agree closely with experimental results for Hg-Xe thin film superconductors and for certain single crystal thin-film high temperature superconductors.
Physics of Spin Casting Dilute Solutions
Stefan Karpitschka,Constans M. Weber,Hans Riegler
Physics , 2012,
Abstract: We analyze the evolution of the vertical composition profile during hydrodynamic-evaporative film thinning as it typically occurs during spin casting mixtures of non-volatile solutes and volatile solvents. We assume that the solvent dominates the hydrodynamic-evaporative film thinning. The internal spatio-temporal evolution of the composition is analyzed with a diffusive-advective approach. The analysis provides transparent physical insights into the influence of the experimental conditions on the evolution of the internal composition. We present power laws that link the process control parameters to the composition evolution, process duration, and final solute coverage. The analysis reveals a characteristic Sherwood Number as fundamental process parameter. It identifies for which stages of the process our analysis is quantitatively relevant and discloses the dominance of either diffusion or evaporation. The analysis is valid for dilute solutions e.g., for the deposition of solute (sub)monolayers. But it is also relevant for the deposition of thicker (polymer) films.
Evidence of Two Distinct Dynamic Critical Exponents in Connection with Vortex Physics
Petter Minnhagen,Beom Jun Kim,Hans Weber
Physics , 2001, DOI: 10.1103/PhysRevLett.87.037002
Abstract: The dynamic critical exponent $z$ is determined from numerical simulations for the three-dimensional (3D) lattice Coulomb gas (LCG) and the 3D XY models with relaxational dynamics. It is suggested that the dynamics is characterized by two distinct dynamic critical indices $z_0$ and $z$ related to the divergence of the relaxation time $\tau$ by $\tau\propto \xi^{z_0}$ and $\tau\propto k^{-z}$, where $\xi$ is the correlation length and $k$ the wavevector. The values determined are $z_0\approx 1.5$ and $z\approx 1$ for the 3D LCG and $z_0\approx 1.5$ and $z\approx 2$ for the 3D XY model. It is argued that the nonlinear $IV$ exponent relates to $z_0$, whereas the usual Hohenberg-Halperin classification relates to $z$. Possible implications for the interpretation of experiments are pointed out. Comparisons with other existing results are discussed.
Critical Scaling Properties at the Superfluid Transition of $^4$He in Aerogel
Marios Nikolaou,Mats Wallin,Hans Weber
Physics , 2006, DOI: 10.1103/PhysRevLett.97.225702
Abstract: We study the superfluid transition of $^4$He in aerogel by Monte Carlo simulations and finite size scaling analysis. Aerogel is a highly porous silica glass, which we model by a diffusion limited cluster aggregation model. The superfluid is modeled by a three dimensional XY model, with excluded bonds to sites on the aerogel cluster. We obtain the correlation length exponent $\nu=0.73 \pm 0.02$, in reasonable agreement with experiments and with previous simulations. For the heat capacity exponent $\alpha$, both experiments and previous simulations suggest deviations from the Josephson hyperscaling relation $\alpha=2-d\nu$. In contrast, our Monte Carlo results support hyperscaling with $\alpha= -0.2\pm 0.05$. We suggest a reinterpretation of previous experiments, which avoids scaling violations and is consistent with our simulation results.
The order topology for a von Neumann algebra
Emmanuel Chetcuti,Jan Hamhalter,Hans Weber
Mathematics , 2014,
Abstract: The order topology $\tau_o(P)$ (resp. the sequential order topology $\tau_{os}(P)$) on a poset $P$ is the topology that has as its closed sets those that contain the order limits of all their order convergent nets (resp. sequences). For a von Neumann algebra $M$ we consider the following three posets: the self-adjoint part $M_{sa}$, the self-adjoint part of the unit ball $M_{sa}^1$, and the projection lattice $P(M)$. We study the order topology (and the corresponding sequential variant) on these posets, compare the order topology to the other standard locally convex topologies on $M$, and relate the properties of the order topology to the underlying operator-algebraic structure of $M$.
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