Spacetime as a quantum many-body system

Quantum gravity has become a fertile interface between gravitational physics and quantum many-body physics, with its double goal of identifying the microscopic constituents of the universe and their fundamental dynamics, and of understanding their collective properties and how spacetime and geometry themselves emerge from them at macroscopic scales. In this brief contribution, we outline the problem of quantum gravity from this emergent spacetime perspective, and discuss some examples in which ideas and methods from quantum many-body systems have found a central role in quantum gravity research.Comment: 15 pages; invited contribution to "Many-body approaches at different scales: A tribute to Norman H. March on the occasion of his 90th birthday", edited by G. G. N. Angilella and C. Amovilli (New York, Springer, 2017 - to appear

Integral equation for inhomogeneous condensed bosons generalizing the Gross-Pitaevskii differential equation

We give here the derivation of a Gross-Pitaevskii--type equation for inhomogeneous condensed bosons. Instead of the original Gross-Pitaevskii differential equation, we obtain an integral equation that implies less restrictive assumptions than are made in the very recent study of Pieri and Strinati [Phys. Rev. Lett. 91 (2003) 030401]. In particular, the Thomas-Fermi approximation and the restriction to small spatial variations of the order parameter invoked in their study are avoided.Comment: Phys. Rev. A (accepted

Tiergesundheit als Faktor des Qualitätsmanagements in der ökologischen Milchviehhaltung - Eine Interventions- und Coaching-Studie zur Anwendung präventiver Tiergesundheitskonzepte

Ziel des ersten Projektteils war es, (1) ein präventives Tiergesundheitskonzept für die ökologische Milchviehhaltung am Beispiel von Lahmheiten zu entwickeln und (2) dieses Managementkonzept anhand einer Interventionsstudie zu validieren sowie dessen Praxistauglichkeit zu demonstrieren. Über einen Zeitraum von drei Jahren (2005-2007) wurde die Lahmheitssituation auf insgesamt 43 ökologisch wirtschaftenden Milchviehbetrieben verfolgt. Die Lahmheitsprävalenz ging in den 21 Interventionsbetrieben, für die mit den BetriebsleiterInnen betriebsindividuelle Maßnahmenkataloge erarbeitet worden waren, konsistent und signifikant stärker zurück als in den Kontrollbetrieben (Intervention: -18,3 % (absolut); Kontrolle: -4,5 %). Der zweite Projektteil hatte zum Ziel, (1) zentrale Indikatoren für die Milchviehgesundheit zu identifizieren und Zielgrößen zu definieren (Mastitis, Lahmheiten, Stoffwechselstörungen, Fruchtbarkeitsstörungen, Kälbererkrankungen), (2) Leitlinien für die Entwicklung von Herdengesundheitsplänen zu erstellen und (3) die Umsetzbarkeit und Effektivität auf Praxisbetrieben unter Einbindung von Betriebsleiter-, Berater- und HoftierärztInnen zu untersuchen. Dazu wurden 44 Bio-Milchviehbetriebe in den Jahren 2006 und 2007 insgesamt vier Mal besucht. Nach einzelbetrieblichen Schwachstellenanalysen wurden in 28 Betrieben unter Berücksichtigung der o.g. Zielgrößen betriebsindividuelle Tiergesundheitspläne erstellt und die Entwicklung der Tiergesundheit im Jahr 2007 für Interventions- und Kontrollbetriebe verfolgt. Ein Jahr nach Einführung der Tiergesundheitspläne ging die Behandlungsinzidenz von klinischen Mastitiden in Betrieben, die diesbezügliche Maßnahmen umgesetzt hatten, signifikant stärker zurück, als in den Kontrollbetrieben. Für andere Indikatoren ließ sich keine Verbesserung der Tiergesundheit absichern; dabei muss jedoch der kurze Beobachtungszeitraum berücksichtigt werden

Evolution: Complexity, uncertainty and innovation

Complexity science provides a general mathematical basis for evolutionary thinking. It makes us face the inherent, irreducible nature of uncertainty and the limits to knowledge and prediction. Complex, evolutionary systems work on the basis of on-going, continuous internal processes of exploration, experimentation and innovation at their underlying levels. This is acted upon by the level above, leading to a selection process on the lower levels and a probing of the stability of the level above. This could either be an organizational level above, or the potential market place. Models aimed at predicting system behaviour therefore consist of assumptions of constraints on the micro-level – and because of inertia or conformity may be approximately true for some unspecified time. However, systems without strong mechanisms of repression and conformity will evolve, innovate and change, creating new emergent structures, capabilities and characteristics. Systems with no individual freedom at their lower levels will have predictable behaviour in the short term – but will not survive in the long term. Creative, innovative, evolving systems, on the other hand, will more probably survive over longer times, but will not have predictable characteristics or behaviour. These minimal mechanisms are all that are required to explain (though not predict) the co-evolutionary processes occurring in markets, organizations, and indeed in emergent, evolutionary communities of practice. Some examples will be presented briefly

Spatial fluctuations in an optical parametric oscillator below threshold with an intracavity photonic crystal

We show how to control spatial quantum correlations in a multimode degenerate optical parametric oscillator type I below threshold by introducing a spatially inhomogeneous medium, such as a photonic crystal, in the plane perpendicular to light propagation. We obtain the analytical expressions for all the correlations in terms of the relevant parameters of the problem and study the number of photons, entanglement, squeezing, and twin beams. Considering different regimes and configurations we show the possibility to tune the instability thresholds as well as the quantumness of correlations by breaking the translational invariance of the system through a photonic crystal modulation.Comment: 12 pages, 7 figure

Energy gaps in quantum first-order mean-field-like transitions: The problems that quantum annealing cannot solve

We study first-order quantum phase transitions in models where the mean-field traitment is exact, and the exponentially fast closure of the energy gap with the system size at the transition. We consider exactly solvable ferromagnetic models, and show that they reduce to the Grover problem in a particular limit. We compute the coefficient in the exponential closure of the gap using an instantonic approach, and discuss the (dire) consequences for quantum annealing.Comment: 6 pages, 3 figure

Power, norms and institutional change in the European Union: the protection of the free movement of goods

How do institutions of the European Union change? Using an institutionalist approach, this article highlights the interplay between power, cognitive limits, and the normative order that underpins institutional settings and assesses their impact upon the process of institutional change. Empirical evidence from recent attempts to reinforce the protection of the free movement of goods in the EU suggests that, under conditions of uncertainty, actors with ambiguous preferences assess attempts at institutional change on the basis of the historically defined normative order which holds a given institutional structure together. Hence, path dependent and incremental change occurs even when more ambitious and functionally superior proposals are on offer

Party finance reform as constitutional engineering? The effectiveness and unintended consequences of party finance reform in France and Britain

In both Britain and France, party funding was traditionally characterized by a laissez faire approach and a conspicuous lack of regulation. In France, this was tantamount to a 'legislative vacuum'. In the last two decades, however, both countries have sought to fundamentally reform their political finance regulation regimes. This prompted, in Britain, the Political Parties, Elections and Referendums Act 2000, and in France a bout of 'legislative incontinence' — profoundly transforming the political finance regime between 1988 and 1995. This article seeks to explore and compare the impacts of the reforms in each country in a bid to explain the unintended consequences of the alternative paths taken and the effectiveness of the new party finance regime in each country. It finds that constitutional engineering through party finance reform is a singularly inexact science, largely due to the imperfect nature of information, the limited predictability of cause and effect, and the constraining influence of non-party actors, such as the Constitutional Council in France, and the Electoral Commission in Britain

Minimising medicine use in organic dairy herds through animal health and welfare planning

Livestock is important in many organic farming systems, and it is an explicit goal to ensure high levels of animal health and welfare (AHW) through good management. This will lead to reduced medicine use and better quality of animal products. In two EU network projects NAHWOA & SAFO it was concluded that this is not guaranteed merely by following organic standards. Both networks recommended implementation of individual animal health plans to stimulate organic farmers to improve AHW. These plans should include a systematic evaluation of AHW and be implemented through dialogue with each farmer in order to identify goals and plan improvements. 15 research institutions in 8 European countries are involved in the proposed project with the main objective to minimise medicine use in organic dairy herds through active and well planned AHW promotion and disease prevention. The project consists of 5 work packages, 4 of which comprise research activities building on current research projects, new applications across borders, exchange of knowledge, results and conclusions between participating countries, and adopting them to widely different contexts. International and national workshops facilitate this exchange. Focus areas are animal health planning, AHW assessment using animal based parameters and development of advisory systems and farmer groups. Epidemiological analyses of the effect on AHW from reduced medicine use and herd improvements are planned in all participating countries