Optimal control of elliptic equations with positive measures

Optimal control problems without control costs in general do not possess solutions due to the lack of coercivity. However, unilateral constraints together with the assumption of existence of strictly positive solutions of a pre-adjoint state equation, are sufficient to obtain existence of optimal solutions in the space of Radon measures. Optimality conditions for these generalized minimizers can be obtained using Fenchel duality, which requires a non-standard perturbation approach if the control-to-observation mapping is not continuous (e.g., for Neumann boundary control in three dimensions). Combining a conforming discretization of the measure space with a semismooth Newton method allows the numerical solution of the optimal control problem

What is the Minimal Systemic Risk in Financial Exposure Networks?

Management of systemic risk in financial markets is traditionally associated with setting (higher) capital requirements for market participants. There are indications that while equity ratios have been increased massively since the financial crisis, systemic risk levels might not have lowered, but even increased. It has been shown that systemic risk is to a large extent related to the underlying network topology of financial exposures. A natural question arising is how much systemic risk can be eliminated by optimally rearranging these networks and without increasing capital requirements. Overlapping portfolios with minimized systemic risk which provide the same market functionality as empirical ones have been studied by [pichler2018]. Here we propose a similar method for direct exposure networks, and apply it to cross-sectional interbank loan networks, consisting of 10 quarterly observations of the Austrian interbank market. We show that the suggested framework rearranges the network topology, such that systemic risk is reduced by a factor of approximately 3.5, and leaves the relevant economic features of the optimized network and its agents unchanged. The presented optimization procedure is not intended to actually re-configure interbank markets, but to demonstrate the huge potential for systemic risk management through rearranging exposure networks, in contrast to increasing capital requirements that were shown to have only marginal effects on systemic risk [poledna2017]. Ways to actually incentivize a self-organized formation toward optimal network configurations were introduced in [thurner2013] and [poledna2016]. For regulatory policies concerning financial market stability the knowledge of minimal systemic risk for a given economic environment can serve as a benchmark for monitoring actual systemic risk in markets.Comment: 25 page

The EU Emissions Trading System and Climate Policy towards 2050: Real incentives to reduce emissions and drive innovation? CEPS Special Reports, 12 January 2011

With the EU Emissions Trading System (ETS) now entering in its seventh year of operation, this report takes stock of the largest multi-sector greenhouse gas trading scheme in the world. It reviews the experiences of the pilot phase from 2005-07, assesses the adjustments introduced in the second phase (2008-12) and looks ahead to the radical changes that will come into effect in the third phase starting in 2013. The assessment is based on a literature review of recently published ex-post analyses and ex-ante studies and draws as well on our own calculations. It investigates the main controversies surrounding the EU ETS, such as its environmental effectiveness, economic rents, windfall profits and fairness, the role of CDM and JI and its impact of on industrial competitiveness. It also evaluates the scheme’s ability to promote innovation and low-carbon technology deployment. Finally, the study addresses the fundamental question of whether the ETS has lived up to its promise to “promote reductions of greenhouse gas emissions in a cost-effective and economically efficient manner”, and if not, what are the prospects of its doing so in the future and what additional changes will be required

Sketched Answer Set Programming

Answer Set Programming (ASP) is a powerful modeling formalism for combinatorial problems. However, writing ASP models is not trivial. We propose a novel method, called Sketched Answer Set Programming (SkASP), aiming at supporting the user in resolving this issue. The user writes an ASP program while marking uncertain parts open with question marks. In addition, the user provides a number of positive and negative examples of the desired program behaviour. The sketched model is rewritten into another ASP program, which is solved by traditional methods. As a result, the user obtains a functional and reusable ASP program modelling her problem. We evaluate our approach on 21 well known puzzles and combinatorial problems inspired by Karp's 21 NP-complete problems and demonstrate a use-case for a database application based on ASP.Comment: 15 pages, 11 figures; to appear in ICTAI 201

THE ROLE OF CROSS-CLASS ALLIANCES AND ELITES IN COORDINATED EMPLOYMENT RELATIONS IN DENMARK. CES Open Forum Series 2018-2019, September 4, 2018

Explanations for coordination between labor and capital in Northern Europe continue to cause debate among scholars of comparative political economy. On one hand, power resource scholars argue that strong trade unions promoting equality are necessary for coordination. On the other hand, employer-centered theories argue that employers are the primary actors in promoting coordination due to the comparative advantages stemming from coordination. To inform this debate, we study the case of Denmark by combining a unique database of 5.000 elite affiliations with 80 stakeholder interviews spanning a decade. We argue that trade union power resources are necessary for coordination. However, only when certain segments of labor can forge powerful alliances with key employers for the economy will coordination persist. The network analysis identifies a powerful cross-class alliance between trade unions and employer associations in manufacturing. Interviews with stakeholders show that coordination in industrial relations and related institutional spheres such as education and industrial policies serves this alliance’s interests in safeguarding international competitiveness of manufacturing. However, intra-class allegiances ensure that the alliance constantly has to consider the interests of outsider organizations

Time evolution of a toy semiholographic glasma

We extend our previous study of a toy model for coupling classical Yang-Mills equations for describing overoccupied gluons at the saturation scale with a strongly coupled infrared sector modeled by AdS/CFT. Including propagating modes in the bulk we find that the Yang-Mills sector loses its initial energy to a growing black hole in the gravity dual such that there is a conserved energy-momentum tensor for the total system while entropy grows monotonically. This involves a numerical AdS simulation with a backreacted boundary source far from equilibrium.Comment: 17 pages, 7 figures, v2: minor changes in section 3 and acknowledgement

From Violence to Witness via Reason and Faith : The Interreligious Message of Pope Benedict XVI

This article examines the message of Pope Benedict XVI to representatives of other religions, especially Muslims, using the pope’s interreligious addresses as the main source material. The main topics surveyed are the peaceful nature of religion, the relationship between faith and reason, and common service or interreligious witness. These are interconnected, for Benedict is convinced that religiously motivated violence is contrary to the essence of religion, irrational, and damaging to the common cause of the religions against radical ecularism. The difficulty arises in declaring a priori, based on Enlightenment convictions, that ‘genuine religion’ is nonviolent at heart, without discussing the authoritative sources of each religion. It is striking that Benedict XVI never quotes the Qur’an in his speeches to Muslims. The appeals to reason, conscience, and human nature attempt to settle the matter on a level preceding faith, but the pope’s Augustinian-Bonaventurian vision requires that reason be illumined by faith and revelation. This framework, used interreligiously, as the pope does, cuts both ways. Who or what decides, in the face of a violent instance of ‘revelation’, whether faith is to be purified by reason, or reason elevated by faith? Benedict XVI provides a strong impetus to those who agree with him and food for thought to all who are open to dialogue, but more needs to be done in order to ‘argue credibly and realistically against religiously motivated violence’.Peer reviewe