Island of Stability for Consistent Deformations of Einstein's Gravity

We construct explicitly deformations of Einstein's theory of gravity that are consistent and phenomenologically viable since they respect, in particular, cosmological backgrounds. We show that these deformations have unique symmetries in accordance with unitarity requirements, and give rise to a curvature induced self-stabilizing mechanism. As a consequence, any nonlinear completed deformation must incorporate self-stabilization on generic spacetimes already at lowest order in perturbation theory. Furthermore, our findings include the possibility of consistent and phenomenologically viable deformations of general relativity that are solely operative on curved spacetime geometries, reducing to Einstein's theory on the Minkowski background.Comment: 4 pages, 3 figures, v2: discussion of phenomenology and applications added, presentation optimize

Self-Protection of Massive Cosmological Gravitons

Relevant deformations of gravity present an exciting window of opportunity to probe the rigidity of gravity on cosmological scales. For a single-graviton theory, the leading relevant deformation constitutes a graviton mass term. In this paper, we investigate the classical and quantum stability of massive cosmological gravitons on generic Friedman backgrounds. For a Universe expanding towards a de Sitter epoch, we find that massive cosmological gravitons are self-protected against unitarity violations by a strong coupling phenomenon.Comment: 1+11 pages, v2: references adde

Work Analysis with Resource-Aware Session Types

While there exist several successful techniques for supporting programmers in deriving static resource bounds for sequential code, analyzing the resource usage of message-passing concurrent processes poses additional challenges. To meet these challenges, this article presents an analysis for statically deriving worst-case bounds on the total work performed by message-passing processes. To decompose interacting processes into components that can be analyzed in isolation, the analysis is based on novel resource-aware session types, which describe protocols and resource contracts for inter-process communication. A key innovation is that both messages and processes carry potential to share and amortize cost while communicating. To symbolically express resource usage in a setting without static data structures and intrinsic sizes, resource contracts describe bounds that are functions of interactions between processes. Resource-aware session types combine standard binary session types and type-based amortized resource analysis in a linear type system. This type system is formulated for a core session-type calculus of the language SILL and proved sound with respect to a multiset-based operational cost semantics that tracks the total number of messages that are exchanged in a system. The effectiveness of the analysis is demonstrated by analyzing standard examples from amortized analysis and the literature on session types and by a comparative performance analysis of different concurrent programs implementing the same interface.Comment: 25 pages, 2 pages of references, 11 pages of appendix, Accepted at LICS 201

Analysis of the visually detectable wear progress on ball screws

The actual progression of pitting on ball screw drive spindles is not well known since previous studies have only relied on the investigation of indirect wear effects (e. g. temperature, motor current, structure-borne noise). Using images from a camera system for ball screw drives, this paper elaborates on the visual analysis of pitting itself. Due to its direct, condition-based assessment of the wear state, an image-based approach offers several advantages, such as: Good interpretability, low influence of environmental conditions, and high spatial resolution. The study presented in this paper is based on a dataset containing the entire wear progression from original condition to component failure of ten ball screw drive spindles. The dataset is being analyzed regarding the following parameters: Axial length, tangential length, and surface area of each pit, the total number of pits, and the time of initial visual appearance of each pit. The results provide evidence that wear development can be quantified based on visual wear characteristics. In addition, using the dedicated camera system, the actual course of the growth curve of individual pits can be captured during machine operation. Using the findings of the analysis, the authors propose a formula for standards-based wear quantification based on geometric wear characteristics

Analysis of the Visually Detectable Wear Progress on Ball Screws

The actual progression of pitting on ball screw drive spindles is not well known since previous studies have only relied on the investigation of indirect wear effects (e. g. temperature, motor current, structure-borne noise). Using images from a camera system for ball screw drives, this paper elaborates on the visual analysis of pitting itself. Due to its direct, condition-based assessment of the wear state, an image-based approach offers several advantages, such as: Good interpretability, low influence of environmental conditions, and high spatial resolution. The study presented in this paper is based on a dataset containing the entire wear progression from original condition to component failure of ten ball screw drive spindles. The dataset is being analyzed regarding the following parameters: Axial length, tangential length, and surface area of each pit, the total number of pits, and the time of initial visual appearance of each pit. The results provide evidence that wear development can be quantified based on visual wear characteristics. In addition, using the dedicated camera system, the actual course of the growth curve of individual pits can be captured during machine operation. Using the findings of the analysis, the authors propose a formula for standards-based wear quantification based on geometric wear characteristics

Reliability-Aware Power Management Of Multi-Core Systems (MPSoCs)

Long-term reliability of processors in embedded systems is experiencing growing attention since decreasing feature sizes and increasing power consumption have a negative influence on the lifespan. Among other measures, the reliability can be influenced significantly by Dynamic Power Management (DPM), since it affects the processor\u27s temperature. Compared to single-core systems reconfigurable multi-core SoCs offer much more possibilities to optimize power and reliability. The impact of different DPM-strategies on the lifespan of multi-core processors is the focus of this presentation. It is shown that the long-term reliability of a multi-core system can be influenced deliberately with different DPM strategies and that temperature cycling greatly influences the estimated lifespan. In this presentation, a new reliability-aware dynamic power management (RADPM) policy is explained

Consistency of Relevant Cosmological Deformations on all Scales

Using cosmological perturbation theory we show that the most relevant defor- mation of gravity is consistent at the linear level. In particular, we prove the absence of uni- tarity violating negative norm states in the weak coupling regime from sub- to super-Hubble scales. This demonstrates that the recently proposed classical self-protection mechanism of deformed gravity extends to the entire kinematical domain.Comment: 22 pages, 4 figure

Delocalization Enhances Conductivity at High Doping Concentrations

Many applications of organic semiconductors require high electrical conductivities and hence high doping levels. Therefore, it is indispensable for effective material design to have an accurate understanding of the underlying transport mechanisms in this regime. In this study, own and literature experimental data that reveal a power-law relation between the conductivity and charge density of strongly p-doped conjugated polymers are combined. This behavior cannot consistently be described with conventional models for charge transport in energetically disordered materials. Here, it is shown that the observations can be explained in terms of a variable range hopping model with an energy-dependent localization length. A tight-binding model is used to quantitatively estimate of the energy-dependent localization length, which is used in an analytical variable range hopping model. In the limit of low charge densities, the model reproduces the well-known Mott variable range hopping behavior, while for high charge densities, the experimentally observed superlinear increase in conductivity with charge density is reproduced. The latter behavior occurs when the Fermi level reaches partially delocalized states. This insight can be anticipated to lead to new strategies to increase the conductivity of organic semiconductors

Deciphering archeological contexts from the magnetic map: Determination of daub distribution and mass of Chalcolithic house remains

The unique size and development of prehistoric megasites of the north Pontic Cucuteni-Tripolye Chalcolithic groups (4100–3600 BCE) challenge modern archeology and paleoecology. The extremely large number of houses (approximately 3000, mostly burned) necessitates the development of multidisciplinary technologies to gain a holistic understanding of such sites. In this contribution, we introduce a novel geophysical methodology and a detailed analysis of magnetic data – including evolved modeling techniques – to provide critical information about the setup of findings, enabling a thorough understanding of the settlement dynamics, apart from invasive excavation techniques. The case study is based on data from magnetic field maps and distribution maps of the daub and pottery find categories. This information is used to infer magnetic models for each find category to numerically calculate their magnetic fields for comparison with the archeological data. The comparison quantifies the sensitivity of the magnetic measurements with respect to the distribution of the different find categories. Next, via inversion computation, the characteristic depth functions of soil magnetization are used to generate maps of magnetization from the measured magnetic field maps. To validate the inverted soil magnetization maps, the magnetic excavation models are used, providing an interpretational frame for the application to magnetic anomalies outside excavated areas. This joint magnetic and archeological methodology allows estimating the find density and testing hypotheses about the burning processes of the houses. In this paper, we show internal patterns of burned houses, comparable to archeological house models, and their calculated masses as examples of the methodology. An application of the new approach to complete megasites has the potential to enable a better understanding of the settlement structure and its evolution, improve the quality of population estimations, and thus calculate the human impact on the forest steppe environment and address questions of resilience and carrying capacity