Fully Explorable Horned Particles Hiding Charge

The charge-hiding effect by a horned particle, which was studied for the case where gravity/gauge-field system is self-consistently interacting with a charged lightlike brane (LLB) as a matter source, is now studied for the case of a time like brane. From the demand that no surfaces of infinite coordinate time redshift (horizons) appear in the problem we are lead now to a completly explorable horned particle space for traveller that goes through the horned particle (as was the case for the LLB) but now also in addition to this, the horned region is fully visible to a static external observer. This requires negative surface energy density for the shell sitting at the throat. We study a gauge field subsystem which is of a special non-linear form containing a square-root of the Maxwell term and which previously has been shown to produce a QCD-like confining gauge field dynamics in flat space-time. The condition of finite energy of the system or asymptotic flatness on one side of the horned particle implies that the charged object sitting at the throat expels all the flux it produces into the other side of the horned particle, which turns out to be of a "tube-like" nature. An outside observer in the asymptotically flat universe detects, therefore, apparently neutral object. The hiding of the electric flux behind the tube-like region of a horned particle is the only possible way that a truly charged particle can still be of finite energy, in a theory that in flat space describes confinement. This points to the physical relevance of such solutions, even though there is the need of negative energy density at the throat of the horned particle, which can be of quantum mechanical origin.Comment: The new version has been accepted for publication in Classical and Quantum Gravity. Title changed to "Fully Explorable Horned Particles Hiding Charge". Horned Particles terminology is used now instead of "wormholes" to dscribe the solutions here. arXiv admin note: text overlap with arXiv:1108.373

Scaling and Formulary cross sections for ion-atom impact ionization

The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.Comment: 46 pages, 8 figure

Laser-Plasma Interactions Enabled by Emerging Technologies

An overview from the past and an outlook for the future of fundamental laser-plasma interactions research enabled by emerging laser systems

Radio-frequency discharges in Oxygen. Part 1: Modeling

In this series of three papers we present results from a combined experimental and theoretical effort to quantitatively describe capacitively coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo model on which the theoretical description is based will be described in the present paper. It treats space charge fields and transport processes on an equal footing with the most important plasma-chemical reactions. For given external voltage and pressure, the model determines the electric potential within the discharge and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used scattering and reaction cross section data are critically assessed and in some cases modified. To validate our model, we compare the densities in the bulk of the discharge with experimental data and find good agreement, indicating that essential aspects of an oxygen discharge are captured.Comment: 11 pages, 10 figure

Dynamical measure and field theory models free of the cosmological constant problem

Summary of abstract Field theory models including gauge theories with SSB are presented where the energy density of the true vacuum state (TVS) is zero without fine tuning. The above models are constructed in the gravitational theory where a measure of integration \Phi in the action is not necessarily \sqrt{-g} but it is determined dynamically through additional degrees of freedom. The ratio \Phi/\sqrt{-g} is a scalar field which can be solved in terms of the matter degrees of freedom due to the existence of a constraint. We study a few explicit field theory models where it is possible to combine the solution of the cosmological constant problem with: 1) possibility for inflationary scenario for the early universe; 2) spontaneously broken gauge unified theories (including fermions). The models are free from the well known problem of the usual scalar-tensor theories in what is concerned with the classical GR tests. The only difference of the field equations in the Einstein frame from the canonical equations of the selfconsistent system of Einstein's gravity and matter fields, is the appearance of the effective scalar field potential which vanishes in TVS without fine tuning.Comment: Extended version of the contribution to the fourth Alexander Friedmann International Seminar on Gravitation and Cosmology; accepted for publication in Phys. Rev. D; 31 page

Inefficient Quality Control of Thermosensitive Proteins on the Plasma Membrane

BACKGROUND: Misfolded proteins are generally recognised by cellular quality control machinery, which typically results in their ubiquitination and degradation. For soluble cytoplasmic proteins, degradation is mediated by the proteasome. Membrane proteins that fail to fold correctly are subject to ER associated degradation (ERAD), which involves their extraction from the membrane and subsequent proteasome-dependent destruction. Proteins with abnormal transmembrane domains can also be recognised in the Golgi or endosomal system and targeted for destruction in the vacuole/lysosome. It is much less clear what happens to membrane proteins that reach their destination, such as the cell surface, and then suffer damage. METHODOLOGY/PRINCIPAL FINDINGS: We have tested the ability of yeast cells to degrade membrane proteins to which temperature-sensitive cytoplasmic alleles of the Ura3 protein or of phage lambda repressor have been fused. In soluble form, these proteins are rapidly degraded upon temperature shift, in part due to the action of the Doa10 and San1 ubiquitin ligases and the proteasome. When tethered to the ER protein Use1, they are also degraded. However, when tethered to a plasma membrane protein such as Sso1 they escape degradation, either in the vacuole or by the proteasome. CONCLUSIONS/SIGNIFICANCE: Membrane proteins with a misfolded cytoplasmic domain appear not to be efficiently recognised and degraded once they have escaped the ER, even though their defective domains are exposed to the cytoplasm and potentially to cytoplasmic quality controls. Membrane tethering may provide a way to reduce degradation of unstable proteins