Field dynamics and kink-antikink production in rapidly expanding systems

Field dynamics in a rapidly expanding system is investigated by transforming from space-time to the rapidity - proper-time frame. The proper-time dependence of different contributions to the total energy is established. For systems characterized by a finite momentum cut-off, a freeze-out time can be defined after which the field propagation in rapidity space ends and the system decays into decoupled solitons, antisolitons and local vacuum fluctuations. Numerical simulations of field evolutions on a lattice for the (1+1)-dimensional $\Phi^4$ model illustrate the general results and show that the freeze-out time and average multiplicities of kinks (plus antikinks) produced in this 'phase transition' can be obtained from simple averages over the initial ensemble of field configurations. An extension to explicitly include additional dissipation is discussed. The validity of an adiabatic approximation for the case of an overdamped system is investigated. The (3+1)-dimensional generalization may serve as model for baryon-antibaryon production after heavy-ion collisions.Comment: 18 pages, 7 figures. Two references added. New subsection III.E added. Final version accepted for publication in PR

Direct frequency comb measurements of absolute optical frequencies and population transfer dynamics

A phase-stabilized femtosecond laser comb is directly used for high-resolution spectroscopy and absolute optical frequency measurements of one- and two-photon transitions in laser-cooled \rb atoms. Absolute atomic transition frequencies, such as the 5S$_{1/2}$ F=2 \ra 7S$_{1/2}$ F"=2 two-photon resonance measured at 788 794 768 921(44) kHz, are determined without \textit{a priori} knowledge about their values. Detailed dynamics of population transfer driven by a sequence of pulses are uncovered and taken into account for the measurement of the 5P states via resonantly enhanced two-photon transitions.Comment: 5 pages, 4 figures, submitte

A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut f\"ur Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\"ur Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.Comment: 9 pages, 2 figures; Solar Physics 277 (2012

Cool Stars and Space Weather

Stellar flares, winds and coronal mass ejections form the space weather. They are signatures of the magnetic activity of cool stars and, since activity varies with age, mass and rotation, the space weather that extra-solar planets experience can be very different from the one encountered by the solar system planets. How do stellar activity and magnetism influence the space weather of exoplanets orbiting main-sequence stars? How do the environments surrounding exoplanets differ from those around the planets in our own solar system? How can the detailed knowledge acquired by the solar system community be applied in exoplanetary systems? How does space weather affect habitability? These were questions that were addressed in the splinter session "Cool stars and Space Weather", that took place on 9 Jun 2014, during the Cool Stars 18 meeting. In this paper, we present a summary of the contributions made to this session.Comment: Proceedings of the 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Eds G. van Belle & H. Harris, 13 pages, 1 figur

Laser frequency combs for astronomical observations

A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at about 1.5 micrometers - beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.Comment: Science, 5th September 2008. 18 pages, 7 figures (7 JPG files), including Supporting Online Material. Version with higher resolution figures available at http://astronomy.swin.edu.au/~mmurphy/pub.htm

Chiral recognition for the complexation dynamics of β-cyclodextrin with the enantiomers of 2-naphthyl-1-ethanol

The focus of this study is to understand the origin of the chiral recognition for a host–guest system containing complexes with different stoichiometries. Each enantiomer of 2-naphthyl-1-ethanol forms two different 1:1 complexes with β-cyclodextrin, leading to the formation of three different 2:2 complexes. One of these 2:2 complexes leads to excimer emission of the guest. Fluorescence studies were employed to determine the binding isotherms for the 1:1 and 2:2 complexes. No chiral discrimination was directly observed for the formation of the 1:1 complexes, while higher equilibrium constants (29% from binding isotherms and 40% from kinetic studies) were observed for the formation of the 2:2 complexes with (R)-2-naphthyl-1-ethanol when compared to the formation of the 2:2 complexes formed from (S)-2-naphthyl-1-ethanol. The relaxation kinetics was studied using stopped-flow experiments. The formation of the 2:2 complexes was followed by detecting the excimer emission from one of the 2:2 complexes. The relaxation kinetics was faster for (S)-2-naphthyl-1-ethanol, where a higher dissociation rate constant, by 47%, was observed, suggesting that the chiral discrimination occurs because the interaction between two cyclodextrins is more favorable for the complexes containing (R)-2-naphthyl-1-ethanol when compared to (S)-2-naphthyl-1-ethanol. The same overall equilibrium constants were observed for the 1:1 complexes with both enantiomers showing that at a given cyclodextrin concentration the sum of the two types of 1:1 complexes is the same for both enantiomers. However, analysis of the binding isotherms indicates that the ratio between the two different 1:1 complexes for each enantiomer was different for (R)- and (S)-2-naphthyl-1-ethanol

Self-Consistent Pushing and Cranking Corrections to the Meson Fields of the Chiral Quark-Loop Soliton

We study translational and spin-isospin symmetry restoration for the two-flavor chiral quark-loop soliton. Instead of a static soliton at rest we consider a boosted and rotating hedgehog soliton. Corrected classical meson fields are obtained by minimizing a corrected energy functional which has been derived by semi-classical methods ('variation after projection'). We evaluate corrected meson fields in the region 300 MeV \le M \le 600 MeV of constituent quark masses M and compare them with the uncorrected fields. We study the effect of the corrections on various expectation values of nuclear observables such as the root-mean square radius, the axial-vector coupling constant, magnetic moments and the delta-nucleon mass splitting.Comment: 19 pages, LaTeX, 7 postscript figures included using 'psfig.sty', to appear in Int.J.Mod.Phys.

Constructing Effective Customer Feedback Systems -- A Design Science Study Leveraging Blockchain Technology

Organizations have to adjust to changes in the ecosystem, and customer feedback systems (CFS) provide important information to adapt products and services to changing customer preferences. However, current systems are limited to single-dimensional rating scales and are subject to self-selection biases. This work contributes design principles for CFS and implements a CFS that advances current systems by means of contextualized feedback according to specific organizational objectives. It also uses blockchain-based incentives to support CFS use. We apply Design Science Research (DSR) methodology and report on a longitudinal DSR journey considering multiple stakeholder values. We conducted expert interviews, design workshops, demonstrations, and a four-day experiment in an organizational setup, involving 132 customers of a major Swiss library. This validates the identified design principles and the implemented software artifact both qualitatively and quantitatively. Based on this evaluation, the design principles are revisited and conclusions for the construction of successful CFS are drawn. The findings of this work advance the knowledge on the design of CFS and provide a guideline to managers and decision makers for designing effective CFS