Entropy Production of Doubly Stochastic Quantum Channels

We study the entropy increase of quantum systems evolving under primitive, doubly stochastic Markovian noise and thus converging to the maximally mixed state. This entropy increase can be quantified by a logarithmic-Sobolev constant of the Liouvillian generating the noise. We prove a universal lower bound on this constant that stays invariant under taking tensor-powers. Our methods involve a new comparison method to relate logarithmic-Sobolev constants of different Liouvillians and a technique to compute logarithmic-Sobolev inequalities of Liouvillians with eigenvectors forming a projective representation of a finite abelian group. Our bounds improve upon similar results established before and as an application we prove an upper bound on continuous-time quantum capacities. In the last part of this work we study entropy production estimates of discrete-time doubly-stochastic quantum channels by extending the framework of discrete-time logarithmic-Sobolev inequalities to the quantum case.Comment: 24 page

Relative Entropy Convergence for Depolarizing Channels

We study the convergence of states under continuous-time depolarizing channels with full rank fixed points in terms of the relative entropy. The optimal exponent of an upper bound on the relative entropy in this case is given by the log-Sobolev-1 constant. Our main result is the computation of this constant. As an application we use the log-Sobolev-1 constant of the depolarizing channels to improve the concavity inequality of the von-Neumann entropy. This result is compared to similar bounds obtained recently by Kim et al. and we show a version of Pinsker's inequality, which is optimal and tight if we fix the second argument of the relative entropy. Finally, we consider the log-Sobolev-1 constant of tensor-powers of the completely depolarizing channel and use a quantum version of Shearer's inequality to prove a uniform lower bound.Comment: 21 pages, 3 figure

Detections and Constraints on White Dwarf Variability from Time-Series GALEX Observations

We search for photometric variability in more than 23,000 known and candidate white dwarfs, the largest ultraviolet survey compiled for a single study of white dwarfs. We use gPhoton, a publicly available calibration/reduction pipeline, to generate time-series photometry of white dwarfs observed by GALEX. By implementing a system of weighted metrics, we select sources with variability due to pulsations and eclipses. Although GALEX observations have short baselines (< 30 min), we identify intrinsic variability in sources as faint as Gaia G = 20 mag. With our ranking algorithm, we identify 49 new variable white dwarfs (WDs) in archival GALEX observations. We detect 41 new pulsators: 37 have hydrogen-dominated atmospheres (DAVs), including one possible massive DAV, and four are helium-dominated pulsators (DBVs). We also detect eight new eclipsing systems; five are new discoveries, and three were previously known spectroscopic binaries. We perform synthetic injections of the light curve of WD 1145+017, a system with known transiting debris, to test our ability to recover similar systems. We find that the 3{\sigma} maximum occurrence rate of WD 1145+017-like transiting objects is < 0.5%.Comment: 17 pages, 13 figure

Polarized lepton nucleon scattering - summary of the experimental spin sessions at DIS 99

This paper summarizes the contributions to the experimental sessions on polarized lepton nucleon scattering at the DIS 99 workshop. Results are reported about the flavor decomposition of the quark polarization, a first direct measurement of a positive gluon polarization, the observation of a double-spin asymmetry in diffractive rho production, the polarization of lambda hyperons, the observation of transverse single-spin asymmetries and the measurement of the Gerasimov-Drell-Hearn sum rule. Prospects of future fixed target and collider facilities are discussed.Comment: 8 pages, 5 figures, Proc. of the 7th Int. Workshop on Deep Inelastic Scattering and QCD (DIS99), Zeuthen, Germany, April 19-23, 1999, to appear in Nucl. Phys. B (Proc. Suppl.

Eclipsing binary and white dwarf features associated with K2 target EPIC251248385

White dwarfs, remnants of Sun-like stars which have completed their evolution, are one of the most common types of stars in space. Despite this, very few white dwarfs have been observed in transiting or eclipsing systems, and only two planetary systems around white dwarfs are currently known, thus motivating a search for white dwarfs with transits or eclipses as seen by the Kepler telescope. A systematic search of K2 white dwarf targets revealed one candidate with regular eclipses, but additional research was necessary to confirm the transits and white dwarf signal were coming from the same astrophysical source. The software package PyKe was utilized to adjust the light curve aperture, and perform principal component analysis which revealed that the transits were originating from a single pixel. Generating a new lightcurve from this pixel revealed the absolute transit depth, which was unconstrained previously. Ten additional images taken with the 2m LCOGT telescope revealed that a potential target star in the single Kepler pixel was actually a cluster of three stars, but no clear transits were seen from any of the potential target stars in the followup images. Additionally, analysis of transit depths in the single pixel light curve and additional investigation of nearby bright sources supported the hypothesis that the transits were more likely to be coming from the white dwarf rather than the two other sources. However, the transit duration and shape appear atypical for white dwarf systems. Thus, despite determining the potential sources and relative sizes for the potential eclipsing white dwarf candidate, or whether the eclipses come from the white dwarf target cannot be confirmed without additional data.https://iopscience.iop.org/article/10.3847/2515-5172/ab5861Published versio

When Do Composed Maps Become Entanglement Breaking?

For many completely positive maps repeated compositions will eventually become entanglement breaking. To quantify this behaviour we develop a technique based on the Schmidt number: If a completely positive map breaks the entanglement with respect to any qubit ancilla, then applying it to part of a bipartite quantum state will result in a Schmidt number bounded away from the maximum possible value. Iterating this result puts a successively decreasing upper bound on the Schmidt number arising in this way from compositions of such a map. By applying this technique to completely positive maps in dimension three that are also completely copositive we prove the so called PPT squared conjecture in this dimension. We then give more examples of completely positive maps where our technique can be applied, e.g.~maps close to the completely depolarizing map, and maps of low rank. Finally, we study the PPT squared conjecture in more detail, establishing equivalent conjectures related to other parts of quantum information theory, and we prove the conjecture for Gaussian quantum channels.Comment: 24 pages, no picture

Modulation enzymatischer Stickoxidsynthasen in zellulären und murinen Modellen der Alzheimer-Krankheit

Die induzierbare Form der Stickoxidsynthase (iNOS) wird bei entzündlichen Stimuli transkriptionell hochreguliert und kann in Gehirnen von Patienten mit Morbus Alzheimer (AD; „Alzheimer’s disease“, auch Alzheimer-Demenz) nachgewiesen werden. Im Rahmen dieser Arbeit wurde der Einfluss der genetischen oder pharmakologischen Ausschaltung der iNOS in Amyloid-Vorläuferprotein/Präsenilin1 (APP/PS1; „amyloid precursor protein/presenilin1“)-transgenen Mäusen auf das räumliche Gedächtnis, die hippokampale Langzeitpotenzierung (LTP; „long term potentiation“), amyloide Pathologie, Astrogliose sowie den neuronalen Verlust hin untersucht. Ebenfalls wurde die Aktivität Amyloid β-degradierender Enzyme sowie synaptosomaler Mitochondrien und deren Modifikationen durch Stickstoffmonoxid (NO) analysiert. APP/PS1-tg iNOS (-/-) Mäuse sowie Mäuse, die mit dem iNOS-spezifischen Inhibitor L-N 6 -(1-iminoethyl)-Lysin (L-NIL) behandelt wurden, zeigten sowohl im Alter von drei, als auch zwölf Monaten im Radialarm-Labyrinth eine signifikante Reduktion von Arbeitsgedächtnis- und Referenzgedächtnisfehlern. Ebenso konnte eine Verbesserung der LTP oben genannter Tiere verglichen mit rein APP/PS1 transgenen Tieren zum Zeitpunkt von drei Monaten gezeigt werden. Darüber hinaus konnte im Alter von zwölf Monaten sowohl mittels „enzyme-linked immunosorbent assay“ (ELISA) eine signifikante Reduktion der Amyloid-β (Aβ)-Menge sowohl in den entsprechenden Ganzhirn-Lysaten, als auch mittels Thioflavin-S-Färbung sowie Aβ-Antikörper-Immunofluoreszenzfärbung in der Großhirnrinde und im Hippocampus nachgewiesen werden. Immunohistologische Untersuchungen zeigten des Weiteren, dass APP/PS1-tg iNOS (-/-) Mäuse, verglichen mit APP/PS1-transgenen Tieren, eine reduzierte „glial fibrillary acidic protein“ (GFAP) Expression, jedoch eine erhöhte „neuronal nuclei“ (NeuN) Immunoreaktivität im Alter von zwölf Monaten in den genannten Gehirnregionen aufweisen. Korrespondierend zu dem Nachweis nitrosylierten Glukose-regulierten Proteins 75 (GRP 75) ließ sich eine reduzierte Aktivität synaptosomaler Mitochondrien durch Zugabe von NO (-Derivat)-Donoren in vitro nachweisen. Diese Ergebnisse lassen vermuten, dass die Expression von iNOS zu einer Verschlechterung der AD-Symptome wie neuropathologische Veränderungen, kognitive Leistung und der damit verbundenen elektrophysiologischen Parameter in diesem etablierten Modell der AD führt. Da die pharmakologische Inhibition der iNOS identische Effekte wie der genetische „knock out“ zeigt, könnte iNOS zukünftig als therapeutisches Ziel zur Behandlung der AD dienen

Assessing and Governing Ecosystem Services Trade-Offs in Agrarian Landscapes: The Case of Biogas

This paper develops a method to explore how alternative scenarios of the expansion of maize production for biogas generation affect biodiversity and ecosystem services (ES). Our approach consists of four steps: (i) defining scenario targets and implementation of assumptions; (ii) simulating crop distributions across the landscape; (iii) assessing the ES impacts; and (iv) quantifying the impacts for a comparative trade-off analysis. The case study is the region of Hannover, Germany. One scenario assumes an increase of maize production in a little regulated governance system; two others reflect an increase of biogas production with either strict or flexible environmental regulation. We consider biodiversity and three ES: biogas generation, food production and the visual landscape. Our results show that the expansion of maize production results in predominantly negative impacts for other ES. However, positive effects can also be identified, i.e., when the introduction of maize leads to higher local crop diversity and, thus, a more attractive visual landscape. The scenario of little regulation portrays more negative impacts than the other scenarios. Targeted spatial planning, implementation and appropriate governance for steering maize production into less sensitive areas is crucial for minimizing trade-offs and exploiting synergies between bioenergy and other ES.Lower Saxony Ministry for Education and Cultur