‘Barking Dogs Seldom Bite’ – Trump and the Middle East

Drafting its Middle East policy, the Trump administration appears to depart from the soft-power rhetoric of the Obama years, seemingly favoring a more hawkish hard-power approach to dealing with America’s most important interests in the region: the defeat of ISIS and the containment of Iran. While many regional partners hope for a radical U.S. foreign policy shift after years of perceived American disengagement, Trump seems to be constrained by path dependency. He inherits a region in turmoil, a public adverse to regional military engagements for peripheral interests, as well as a major strategic discrepancy between ambition and capability. Consequently, the new White House will be forced to continue Obama’s policy of delegation and multilateralism

Topological tunneling with Dynamical overlap fermions

Tunneling between different topological sectors with dynamical chiral fermions is difficult because of a poor mass scaling of the pseudo-fermion estimate of the determinant. For small fermion masses it is virtually impossible using standard methods. However, by projecting out the small Wilson eigenvectors from the overlap operator, and treating the correction determinant exactly, we can significantly increase the rate of topological sector tunneling and reduce substantially the auto-correlation time. We present and compare a number of different approaches, and advocate a method which allows topological tunneling even at low mass with little addition to the computational cost.Comment: 17 pages; v2 as accepted in computer Physics Communication

Adaptive Aggregation Based Domain Decomposition Multigrid for the Lattice Wilson Dirac Operator

In lattice QCD computations a substantial amount of work is spent in solving discretized versions of the Dirac equation. Conventional Krylov solvers show critical slowing down for large system sizes and physically interesting parameter regions. We present a domain decomposition adaptive algebraic multigrid method used as a precondtioner to solve the "clover improved" Wilson discretization of the Dirac equation. This approach combines and improves two approaches, namely domain decomposition and adaptive algebraic multigrid, that have been used seperately in lattice QCD before. We show in extensive numerical test conducted with a parallel production code implementation that considerable speed-up over conventional Krylov subspace methods, domain decomposition methods and other hierarchical approaches for realistic system sizes can be achieved.Comment: Additional comparison to method of arXiv:1011.2775 and to mixed-precision odd-even preconditioned BiCGStab. Results of numerical experiments changed slightly due to more systematic use of odd-even preconditionin

Aggregation-based Multilevel Methods for Lattice QCD

In Lattice QCD computations a substantial amount of work is spent in solving the Dirac equation. In the recent past it has been observed that conventional Krylov solvers tend to critically slow down for large lattices and small quark masses. We present a Schwarz alternating procedure (SAP) multilevel method as a solver for the Clover improved Wilson discretization of the Dirac equation. This approach combines two components (SAP and algebraic multigrid) that have separately been used in lattice QCD before. In combination with a bootstrap setup procedure we show that considerable speed-up over conventional Krylov subspace methods for realistic configurations can be achieved.Comment: Talk presented at the XXIX International Symposium on Lattice Field Theory, July 10-16, 2011, Lake Tahoe, Californi

Surrogate warfare:the art of war in the 21st century?

Airpower, drones and cyber-weapons are employed by states in conjunction with local armed non-state actors in an effort to coercively intervene in the crises of the twenty-first century. While the externalization of the burden of warfare is a return to pre-modern war, it is the change in the underlying socio-political relations between the state and its military agent that is a novel phenomenon in surrogate warfare. This article demonstrates that in a post-Westphalian era characterized by non-state violence, globalized conflicts, a prioritization of risk management in a mediatized environment, the state has to explore new ways to remain relevant as the primary communal security provider. Thereby, the organization of violence has departed from the employment of the state’s soldier as the primary bearer of the burden of warfare to a mode of war where technological and human surrogates enable the state to manage the risks of post-modern conflict remotely. In this article, we conceptually explore surrogate warfare as a socio-political phenomenon within the context of globalized, privatized, securitized and mediatized war.</p

Leg Lengthening With a Motorized Nail in Adolescents: An Alternative to External Fixators?

Leg lengthening by external fixation is associated with various difficulties. We evaluated eight adolescent patients who underwent leg lengthening with a motorized intramedullary lengthening device. We asked whether this method could reduce the time of hospitalization and rehabilitation and whether the incidence of complications commonly associated with external fixators could be reduced. We compared our preliminary results with those from other reports, with a focus on leg length achieved, time of rehabilitation, and rate of complications. The average leg-length discrepancy was 3.8cm (range, 3-5cm). The average lengthening distance was 3.8cm (range, 2.9-4.7cm). In six patients, leg lengthening was combined with successful correction of the mechanical axis alignment. The consolidation index averaged 26days/cm (range, 19-41days/cm). The average hospital stay was 9.6days. No bone or soft tissue infections were observed. In comparison to other studies (1.0-2.8 complications/patient), our results suggest that the difficulties commonly associated with external fixators can be reduced with this method. It also allows good angular correction in patients with mechanical axis deviation. These features combined with a short time of hospitalization and rehabilitation make it a promising procedure for limb lengthening. Level of Evidence: Level IV Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidenc

Numerical Methods for the QCD Overlap Operator:III. Nested Iterations

The numerical and computational aspects of chiral fermions in lattice quantum chromodynamics are extremely demanding. In the overlap framework, the computation of the fermion propagator leads to a nested iteration where the matrix vector multiplications in each step of an outer iteration have to be accomplished by an inner iteration; the latter approximates the product of the sign function of the hermitian Wilson fermion matrix with a vector. In this paper we investigate aspects of this nested paradigm. We examine several Krylov subspace methods to be used as an outer iteration for both propagator computations and the Hybrid Monte-Carlo scheme. We establish criteria on the accuracy of the inner iteration which allow to preserve an a priori given precision for the overall computation. It will turn out that the accuracy of the sign function can be relaxed as the outer iteration proceeds. Furthermore, we consider preconditioning strategies, where the preconditioner is built upon an inaccurate approximation to the sign function. Relaxation combined with preconditioning allows for considerable savings in computational efforts up to a factor of 4 as our numerical experiments illustrate. We also discuss the possibility of projecting the squared overlap operator into one chiral sector.Comment: 33 Pages; citations adde

Parameter Influences on HVDC Transformer Insulation and Its Link to Conduction Processes

HVDC (high voltage direct current) transmission is an effective way to transport electrical power over long distances by using direct current. The insulation system of HVDC components has to be designed for both AC and DC field distributions. It consists of mineral oil and pressboard. The used insulation material behavior has not been completely understood under DC stress. In this paper, electrical conductivity of pressboard is evaluated and conduction processes are considered. Therefore, conductivity measurements are linked to a number of RC network elements in order to achieve a network model representative for the insulation material behavior under DC stress. Time-constants are determined under different temperatures and different electric field strengths. In addition, the performed simulations provide evaluation of parameters affecting the dielectric behavior of the insulation system oil and pressboard, which are not measured or even cannot be determined by measurement