Relations between transfer matrices and numerical stability analysis to avoid the Ωd\Omega d problem

The transfer matrix method is usually employed to study problems described by $N$ equations of matrix Sturm-Liouville (MSL) kind. In some cases a numerical degradation (the so called $\Omega d$ problem) appears thus impairing the performance of the method. We present here a procedure that can overcome this problem in the case of multilayer systems having piecewise constant coefficients. This is performed by studying the relations between the associated transfer matrix and other transfer matrix variants. In this way it was possible to obtain the matrices which can overcome the $\Omega d$ problem in the general case and then in problems which are particular cases of the general one. In this framework different strategies are put forward to solve different boundary condition problems by means of these numerically stable matrices. Numerical and analytic examples are presented to show that these stable variants are more adequate than other matrix methods to overcome the $\Omega d$ problem. Due to the ubiquity of the MSL system, these results can be applied to the study of many elementary excitations in multilayer structures.Comment: 23 pages, 2 figure

DoS protection for a Pragmatic Multiservice Network Based on Programmable Networks

Proceedings of First International IFIP TC6 Conference, AN 2006, Paris, France, September 27-29, 2006.We propose a scenario of a multiservice network, based on pragmatic ideas of programmable networks. Active routers are capable of processing both active and legacy packets. This scenario is vulnerable to a Denial of Service attack, which consists in inserting false legacy packets into active routers. We propose a mechanism for detecting the injection of fake legacy packets into active routers. This mechanism consists in exchanging accounting information on the traffic between neighboring active routers. The exchange of accounting information must be carried out in a secure way using secure active packets. The proposed mechanism is sensitive to the loss of packets. To deal with this problem some improvements in the mechanism has been proposed. An important issue is the procedure for discharging packets when an attack has been detected. We propose an easy and efficient mechanism that would be improved in future work.Publicad

Implementing a subnational results-oriented management and budgeting system. Lessons from Medellín, Colombia.

"The purpose of this paper is to describe the budget process reform implemented in Medellín, and to analyze its actual performance and evaluate its success. The reform is changing the way public resources are allocated and executed, while gradually institutionalizing supply and demand-side practices beyond the government´s political cycles.This paper describes and analyzes how the RoB was designed and implemented, and the achievements of the system to date, in terms of resource allocation and the policy-making process. The following section describes the context of Medellín: political and economic trends, and the objectives of the budget reform. The third section presents the state of the budget process in Medellín as it was diagnosed before implementation. Section four describes the implementation process of the system, and section five addresses its major achievements. A final section includes some policy recommendations, which can be divided into two parts: (i) recommendations for consolidating the system as a main support tool of a RoM approach, and (ii) recommendations for replicating the system in other municipalities and subnational governments".Budget process reform, Budget reform, Medellín, Colombia

The International National: Ius Commune and the fictions of citizenship.

The following text was presented as part of the Presidential Panel at the American Comparative Literature Association, Utrecht (The Netherlands), July 8th 2017. The panel was composed of Joseph Slaughter (ACLA President, English and Comparative Literature, Columbia University in the City of New York), Maria Aristodemou, Law, Birkbeck College, London), and Hala Halim (Comparative Literature, NYU). I address the question that international law is already formally, politically, and culturally embedded in national laws from a historical perspective. I will show how cultural legal history could unveil the ways in which the formation of national common law —and in particular that that claims to derive from the tradition of ius commune— implies the articulation of imperial and ecclesiastical legal models. This articulation, and its presentation as a common legal core, is indeed the result of a complex process of exclusions, of which one could highlight some important ones, including, of course, other universalized legal systems (Muslim, Jew), racial issues, gender issues as well as other more subtle ones, like the legalities surrounding citizenship and the legal fictions (fictiones legum) that underwrite citizenship in the process of imperial expansion

The Asian Liquidity Crisis

A country's financial system is internationally illiquid if its potential short term obligations in foreign currency exceed the amount of foreign currency it can have access to in short notice. This condition may be crucial for the existence of financial crises and/or exchange rate collapses (Chang and Velasc 1998a, b). In this paper we argue that the 1997-98 crises in Asia were in fact a consequence of international illiquidity.LIQUIDITY ; BANKS ; CURRENCIES ; MONETARY CRISIS

Quantum Isotropization of the Universe

We consider minisuperspace models constituted of Bianchi I geometries with a free massless scalar field. The classical solutions are always singular (with the trivial exception of flat space-time), and always anisotropic once they begin anisotropic. When quantizing the system, we obtain the Wheeler-DeWitt equation as a four-dimensional massless Klein-Gordon equation. We show that there are plenty of quantum states whose corresponding bohmian trajectories may be non-singular and/or presenting large isotropic phases, even if they begin anisotropic, due to quantum gravitational effects. As a specific example, we exhibit field plots of bohmian trajectories for the case of gaussian superpositions of plane wave solutions of the Wheeler-DeWitt equation which have those properties. These conclusions are valid even in the absence of the scalar field.Comment: 10 pages, RevTeX, 3 Postscript figures, uses graficx.st

Is there Ornstein-Zernike equation in the canonical ensemble?

A general density-functional formalism using an extended variable-space is presented for classical fluids in the canonical ensemble (CE). An exact equation is derived that plays the role of the Ornstein-Zernike (OZ) equation in the grand canonical ensemble (GCE). When applied to the ideal gas we obtain the exact result for the total correlation function h_N. For a homogeneous fluid with N particles the new equation only differs from OZ by 1/N and it allows to obtain an approximate expression for h_N in terms of its GCE counterpart that agrees with the expansion of h_N in powers of 1/N.Comment: 5 pages, RevTeX. Submitted to Phys. Rev. Let