Fermion Energies in the Background of a Cosmic String

We provide a thorough exposition, including technical and numerical details, of previously published results on the quantum stabilization of cosmic strings. Stabilization occurs through the coupling to a heavy fermion doublet in a reduced version of the standard model. We combine the vacuum polarization energy of fermion zero-point fluctuations and the binding energy of occupied energy levels, which are of the same order in a semi-classical expansion. Populating these bound states assigns a charge to the string. We show that strings carrying fermion charge become stable if the electro-weak bosons are coupled to a fermion that is less than twice as heavy as the top quark. The vacuum remains stable in our model, because neutral strings are not energetically favored. These findings suggests that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev

Pericarditis Constrictiva in a 10-Year-Old Boy After Influenza A Virus Infection

Pericarditis constrictiva is caused by fibrotic degeneration of the pericardium and leads to impaired diastolic ventricular filling. The diagnosis of constrictive pericarditis in children remains challenging and often requires a multimodal approach. We present a case of a pericarditis constrictiva in a 10-year old boy after influenza A virus infection. Clinicians should be aware of this complication, especially in patients with symptoms of exertional dyspnea and congestive heart failur

Hamiltonian approach to QCD in Coulomb gauge - a survey of recent results

I report on recent results obtained within the Hamiltonian approach to QCD in Coulomb gauge. Furthermore this approach is compared to recent lattice data, which were obtained by an alternative gauge fixing method and which show an improved agreement with the continuum results. By relating the Gribov confinement scenario to the center vortex picture of confinement it is shown that the Coulomb string tension is tied to the spatial string tension. For the quark sector a vacuum wave functional is used which explicitly contains the coupling of the quarks to the transverse gluons and which results in variational equations which are free of ultraviolet divergences. The variational approach is extended to finite temperatures by compactifying a spatial dimension. The effective potential of the Polyakov loop is evaluated from the zero-temperature variational solution. For pure Yang--Mills theory, the deconfinement phase transition is found to be second order for SU(2) and first order for SU(3), in agreement with the lattice results. The corresponding critical temperatures are found to be $275 \, \mathrm{MeV}$ and $280 \, \mathrm{MeV}$, respectively. When quarks are included, the deconfinement transition turns into a cross-over. From the dual and chiral quark condensate one finds pseudo-critical temperatures of $198 \, \mathrm{MeV}$ and $170 \, \mathrm{MeV}$, respectively, for the deconfinement and chiral transition.Comment: Talk given by H. Reinhardt at "5th Winter Workshop on Non-Perturbative Quantum Field Theory", 22-24 March 2017, Sophia-Antipolis, France. arXiv admin note: text overlap with arXiv:1609.09370, arXiv:1510.03286, arXiv:1607.0814

Cosmic Strings Stabilized by Fermion Fluctuations

We provide a thorough exposition of recent results on the quantum stabilization of cosmic strings. Stabilization occurs through the coupling to a heavy fermion doublet in a reduced version of the standard model. The study combines the vacuum polarization energy of fermion zero-point fluctuations and the binding energy of occupied energy levels, which are of the same order in a semi-classical expansion. Populating these bound states assigns a charge to the string. Strings carrying fermion charge become stable if the Higgs and gauge fields are coupled to a fermion that is less than twice as heavy as the top quark. The vacuum remains stable in the model, because neutral strings are not energetically favored. These findings suggest that extraordinarily large fermion masses or unrealistic couplings are not required to bind a cosmic string in the standard model.Comment: Based on talk by HW at QFEXT 11 (Benasque, Spain), 15p, uses ws-ijmpcs.cls (incl

Effects of heat and drought on carbon and water dynamics in a regenerating semi-arid pine forest: a combined experimental and modeling approach

Predicting the net effects on the carbon and water balance of semi-arid forests under future conditions depends on ecosystem processes responding to changes in soil and atmospheric drought. Here we apply a combination of field observations and soil-plant-atmosphere modeling (SPA) to study carbon and water dynamics in a regenerating ponderosa pine forest. The effects of soil and atmospheric drought were quantified based on a field irrigation experiment combined with model simulations. To assess future effects of intensifying drought on ecosystem processes, the SPA model was run using temperature and precipitation scenarios for 2040 and 2080. Experimentally increased summer water availability clearly affected tree hydraulics and enhanced C uptake in both the observations and the model. Simulation results showed that irrigation was sufficient to eliminate soil water limitation and maintaining transpiration rates, but gross primary productivity (GPP) continued to decrease. Observations of stomatal conductance indicated a dominant role of vapor pressure deficit (VPD) in limiting C uptake. This was confirmed by running the simulation under reduced atmospheric drought (VPD of 1 kPa), which largely maintained GPP rates at pre-drought conditions. The importance of VPD as a dominant driver was underlined by simulations of extreme summer conditions. We found GPP to be affected more by summer temperatures and VPD as predicted for 2080 (-17%) than by reductions in summer precipitation (-9%). Because heterotrophic respiration responded less to heat (-1%) than to reductions in precipitation (-10%), net ecosystem C uptake declined strongest under hotter (-38%) compared to drier summer conditions (-8%). Considering warming trends across all seasons (September-May: +3 °C and June-August: +4.5 °C), the negative drought effects were largely compensated by an earlier initiation of favorable growing conditions and bud break, enhancing early season GPP and needle biomass. An adverse effect, triggered by changes in early season allocation patterns, was the decline of wood and root biomass. This imbalance may increase water stress over the long term to a threshold at which ponderosa pine may not survive, and highlights the need for an integrated process understanding of the combined effects of trends and extremes

More Than Stories With Buttons: Narrative, Mechanics, and Context as Determinants of Player Experience in Digital Games

Recent research has attempted to describe meaningful experiences with entertainment media that go beyond hedonic enjoyment. Most of this research focuses on noninteractive media, such as film and television. When applied to digital games, however, such research needs to account for not only the content of the medium, but also the unique dimensions of digital games that distinguish them from noninteractive media. Experiences with digital games are shaped by the game mechanics that define the users' interaction with game content, as well as by the opportunities for social interaction that many games offer. We argue that the complex interplay of these dimensions (narrative, mechanics, and context) facilitates or inhibits meaningful user experiences in ways that are unique to digital games

Phylogenetic relationships in the “Pinnatella” clade of the moss family Neckeraceae (Bryophyta)

Peer reviewe

Dielectric function of the QCD vacuum

It is shown that the inverse of the ghost form factor in the Hamilton approach to Yang-Mills theory in Coulomb gauge can be interpreted as the color dielectric function of the QCD vacuum. Furthermore the horizon condition to the ghost form factor implies that in the infrared the QCD vacuum is a perfect color diaelectric medium and therefore a dual superconductor. The dielectric function is explicitly calculated within a previously developed variational approach, using a specific ansatz for the vacuum wave functional.Comment: 4 pages, 1 figure, revised version as published in Phys. Rev. Let