Frustrated Heisenberg antiferromagnets: fluctuation induced first order vs deconfined quantum criticality

Recently it was argued that quantum phase transitions can be radically different from classical phase transitions with as a highlight the 'deconfined critical points' exhibiting fractionalization of quantum numbers due to Berry phase effects. Such transitions are supposed to occur in frustrated ('$J_1$-$J_2$') quantum magnets. We have developed a novel renormalization approach for such systems which is fully respecting the underlying lattice structure. According to our findings, another profound phenomenon is around the corner: a fluctuation induced (order-out-of-disorder) first order transition. This has to occur for large spin and we conjecture that it is responsible for the weakly first order behavior recently observed in numerical simulations for frustrated $S=1/2$ systems.Comment: 7 pages, 3 Figures, submitted to EP

Vertex-Constraints in 3D Higher Spin Theories

We analyse the constraints imposed by gauge invariance on higher-order interactions between massless bosonic fields in three-dimensional higher-spin gravities. We show that vertices of quartic and higher order that are independent of the cubic ones can only involve scalars and Maxwell fields. As a consequence, the full non-linear interactions of massless higher-spin fields are completely fixed by the cubic vertex.Comment: 5 page

Accurate calculation of the transverse anisotropy in perpendicularly magnetized multilayers

The transverse anisotropy constant and the related D\"oring mass density are key parameters of the one-dimensional model to describe the motion of magnetic domain walls. So far, no general framework is available to determine these quantities from static characterizations such as magnetometry measurements. Here, we derive a universal analytical expression to calculate the transverse anisotropy constant for the important class of perpendicular magnetic multilayers. All the required input parameters of the model, such as the number of repeats, the thickness of a single magnetic layer, and the layer periodicity, as well as the effective perpendicular anisotropy, the saturation magnetization, and the static domain wall width are accessible by static sample characterizations. We apply our model to a widely used multilayer system and find that the effective transverse anisotropy constant is a factor 7 different from the when using the conventional approximations, showing the importance of using our analysis scheme

Analysis of Sentiments in Corporate Twitter Communication – A Case Study on an Issue of Toyota

Knowing about communication of specific issues in social media has become increasingly important for the reactive and proactive stakeholder-communication of enterprises. Tools have been designed to monitor social media sites and to aggregate data of discussions in social media. However, these tools do not consider the dynamics of discussions and are not able to reflect sentiments within these discussions. In our contribution, we address these aspects by analyzing a data set of around 730,000 Tweets published in a time frame of 19 weeks. Within this data set, we analyzed those Tweets dealing with the corporate crisis of Toyota in 2010. We classified sentiments by using a linguistic approach. In this context, we identified and investigated specific stages of communication (“quiet stages” and “peaks”). Additionally, our study concentrates on the sentiments found in Tweets of the ten most active participants of the discussion

Kinematic Effects in Quarkonia Production

We investigate energy (momentum) distributions in J/Psi photoproduction and J/Psi production in B meson decay. In particular the upper endpoint region of the spectrum is examined where the effect of soft gluon emission from the ccbar pair becomes important. Constructing a model which is consistent with the so-called shape function formalism we consider these fragmentation effects and show that the relevance of possible colour octet contributions in the photoproduction channel is still inconclusive.Comment: LaTeX, 7 pages, 3 figures, The complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints