529 research outputs found
Burden-Sharing and Accommodation of Migrants in the EU - a Simulation Based on Factorial Designs
In recent years, migration to European countries has intensified like never before, raising issues regarding cooperation in order to manage the situation. The aim of this paper is to simulate the implications for the cooperation
between countries using the Vickrey-Clarke-Groves (VCG) mechanism and statistical analysis. In the simulation, we identify the consequences of various decisions of the countries involved in accommodating migrants. We conclude that the types of migrants and partners willing to cooperate can influence on the groups accommodated first, and that the decision to cooperate can influence on the political situation and budgets of receiving countries
A relative entropy rate method for path space sensitivity analysis of stationary complex stochastic dynamics
We propose a new sensitivity analysis methodology for complex stochastic
dynamics based on the Relative Entropy Rate. The method becomes computationally
feasible at the stationary regime of the process and involves the calculation
of suitable observables in path space for the Relative Entropy Rate and the
corresponding Fisher Information Matrix. The stationary regime is crucial for
stochastic dynamics and here allows us to address the sensitivity analysis of
complex systems, including examples of processes with complex landscapes that
exhibit metastability, non-reversible systems from a statistical mechanics
perspective, and high-dimensional, spatially distributed models. All these
systems exhibit, typically non-gaussian stationary probability distributions,
while in the case of high-dimensionality, histograms are impossible to
construct directly. Our proposed methods bypass these challenges relying on the
direct Monte Carlo simulation of rigorously derived observables for the
Relative Entropy Rate and Fisher Information in path space rather than on the
stationary probability distribution itself. We demonstrate the capabilities of
the proposed methodology by focusing here on two classes of problems: (a)
Langevin particle systems with either reversible (gradient) or non-reversible
(non-gradient) forcing, highlighting the ability of the method to carry out
sensitivity analysis in non-equilibrium systems; and, (b) spatially extended
Kinetic Monte Carlo models, showing that the method can handle high-dimensional
problems
Three form potential in (special) minimal supergravity superspace and supermembrane supercurrent
This contribution begins the study of the complete superfield Lagrangian
description of the interacting system of D=4 N=1 supergravity (SUGRA) and
supermembrane. Firstly, we review a 'three form supergravity' by Ovrut and
Waldram, which we prefer to call 'special minimal supergravity'. This off-shell
formulation of simple SUGRA is appropriate for our purposes as the
supermembrane action contains the so-called Wess-Zumino term given by the
integral over a three form potential in superspace, C3. We describe this
formulation in the frame of Wess--Zumino superfield approach, showing how the
basic variations of minimal SUGRA are restricted by the conditions of the
existence of a three-form potential C3 in its superspace. In this language the
effect of dynamical generation of cosmological constant, known to be
characteristic for this formulation of SUGRA, appears in its superfield form,
first described by Ogievetsky and Sokatchev in their formulation of SUGRA as a
theory of axial vector superfield. Secondly, we vary the supermembrane action
with respect to the special minimal SUGRA superfields (basic variations) and
obtain the supercurrent superfields as well as the supergravity superfield
equations with the supermembrane contributions.Comment: 18 pages, no figures. V2: Important references added. The abstract
and presentation have been changed to reflect the overloop with that.
Submitted to the QTS7 Proceedings. J. Phys. style use
Electrochemistry at nanoscale electrodes : individual single-walled carbon nanotubes (SWNTs) and SWNT-templated metal nanowires
Individual nanowires (NWs) and native single-walled carbon nanotubes (SWNTs) can be readily used as well-defined nanoscale electrodes (NSEs) for voltammetric analysis. Here, the simple photolithography-free fabrication of submillimeter long Au, Pt, and Pd NWs, with sub-100 nm heights, by templated electrodeposition onto ultralong flow-aligned SWNTs is demonstrated. Both individual Au NWs and SWNTs are employed as NSEs for electron-transfer (ET) kinetic quantification, using cyclic voltammetry (CV), in conjunction with a microcapillary-based electrochemical method. A small capillary with internal diameter in the range 30â70 ÎŒm, filled with solution containing a redox-active mediator (FcTMA+ ((trimethylammonium)methylferrocene), Fe(CN)64â, or hydrazine) is positioned above the NSE, so that the solution meniscus completes an electrochemical cell. A 3D finite-element model, faithfully reproducing the experimental geometry, is used to both analyze the experimental CVs and derive the rate of heterogeneous ET, using ButlerâVolmer kinetics. For a 70 nm height Au NW, intrinsic rate constants, k0, up to ca. 1 cm sâ1 can be resolved. Using the same experimental configuration the electrochemistry of individual SWNTs can also be accessed. For FcTMA+/2+ electrolysis the simulated ET kinetic parameters yield very fast ET kinetics (k0 > 2 ± 1 cm sâ1). Some deviation between the experimental voltammetry and the idealized model is noted, suggesting that double-layer effects may influence ET at the nanoscale
Global Symmetries and D-Terms in Supersymmetric Field Theories
We study the role of D-terms in supersymmetry (SUSY) breaking. By carefully
analyzing the SUSY multiplets containing various conserved currents in theories
with global symmetries, we obtain a number of constraints on the
renormalization group flow in supersymmetric field theories. Under broad
assumptions, these results imply that there are no SUSY-breaking vacua, not
even metastable ones, with parametrically large D-terms. This explains the
absence of such D-terms in models of dynamical SUSY-breaking. There is,
however, a rich class of calculable models which generate comparable D-terms
and F-terms through a variety of non-perturbative effects; these D-terms can be
non-abelian. We give several explicit examples of such models, one of which is
a new calculable limit of the 3-2 model.Comment: 34 pages, 2 figures; reference added, minor change
Anomalous Dimensions of Non-Chiral Operators from AdS/CFT
Non-chiral operators with positive anomalous dimensions can have interesting
applications to supersymmetric model building. Motivated by this, we develop a
new method for obtaining the anomalous dimensions of non-chiral double-trace
operators in N=1 superconformal field theories (SCFTs) with weakly-coupled AdS
duals. Via the Hamiltonian formulation of AdS/CFT, we show how to directly
compute the anomalous dimension as a bound state energy in the gravity dual.
This simplifies previous approaches based on the four-point function and the
OPE. We apply our method to a class of effective AdS5 supergravity models, and
we find that the binding energy can have either sign. If such models can be UV
completed, they will provide the first calculable examples of SCFTs with
positive anomalous dimensions.Comment: 38 pages, 2 figures, refs adde
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