University of Paderborn

About: University of Paderborn is a education organization based out in Paderborn, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Computer science & Context (language use). The organization has 6684 authors who have published 16929 publications receiving 323154 citations.

Equations of state for solids under strong compression

Abstract: The historical and theoretical background for the different mathematical forms commonly used to represent equations of state (EOS) for solids is reviewed and some criteria are discussed which allow to select some specific forms, which are not only convenient mathematical forms but bring out the physical meaning of the data. Some examples are discussed with emphasis on recent experimental and theoretical data including noble gas solids, simple metals and a few metals with special “anomalies” to illustrate the differences involved in the use of different EOS forms and to point out the specific physical reasons for differences in specific EOS forms.

Møller's energy-momentum complex — Once again

Abstract: The 35-year-old problem of Moller's energy-momentum four-vector when transformed by a global Lorentz transformation is discussed again. It is argued that Moller's result is adequate from the viewpoint of general relativity and hence does not defeat his energy-momentum complex.

Nash equilibria in discrete routing games with convex latency functions

Abstract: We study Nash equilibria in a discrete routing game that combines features of the two most famous models for non-cooperative routing, the KP model [16] and the Wardrop model [27]. In our model, users share parallel links. A user strategy can be any probability distribution over the set of links. Each user tries to minimize its expected latency, where the latency on a link is described by an arbitrary non-decreasing, convex function. The social cost is defined as the sum of the users' expected latencies. To the best of our knowledge, this is the first time that mixed Nash equilibria for routing games have been studied in combination with non-linear latency functions. As our main result, we show that for identical users the social cost of any Nash equilibrium is bounded by the social cost of the fully mixed Nash equilibrium. A Nash equilibrium is called fully mixed if each user chooses each link with non-zero probability. We present a complete characterization of the instances for which a fully mixed Nash equilibrium exists, and prove that (in case of its existence) it is unique. Moreover, we give bounds on the coordination ratio and show that several results for the Wardrop model can be carried over to our discrete model.

NV centers in 3 C ,4 H , and 6 H silicon carbide: A variable platform for solid-state qubits and nanosensors

Abstract: The outstanding magneto-optical properties of the nitrogen-vacancy (NV) center in diamond have stimulated the search for similar systems. We show here that NV triplet centers can also be generated in all the main SiC polytypes. We have identified by electron paramagnetic resonance spectroscopy and first-principles calculations the axial ${\mathrm{NV}}^{\ensuremath{-}}$ pairs in $3C,4H$, and $6H$ SiC, showing polytype and lattice site-specific magnetic and optical properties. We demonstrate very efficient room-temperature spin polarization of the ground state upon near infrared optical excitation for the NV center in $3C$ SiC and axial NV centers in the hexagonal $(4H,6H)$ polytypes; the signals of basal pairs are much lower in intensity. Axial NV centers in hexagonal SiC polytypes and thus constitute unidirectional ensembles which may be useful in nanosensing applications.