International Liquidity and the Role of the SDR in the International Monetary System

This paper describes how the changed conditions in the international monetary system have undermined the role originally envisaged for the SDR. It argues that the concept of a global stock of international liquidity, which was fundamental to the creation of the SDR, is now no longer relevant. Nonetheless, there are good reasons to satisfy part of the growing demand for international reserves with SDR allocations: (i) there are efficiency gains, as SDRs can be created at zero resource cost, and thus obviate the need for countries to run current account surpluses or engage in expensive borrowing to obtain reserves, and (ii) there would be a reduction in systemic risk, as SDRs would substitute to some extent for borrowed reserves, which are a less reliable and predictable source of reserves, especially in times of crisis. Copyright 2004, International Monetary Fund

Development and Application of an Activity Based Space-Time Accessibility Measure for Individual Activity Schedules

Accessibility is an important aspect of human existence impacting on our notion of society equity and justice. It plays an important role in a number of existing theories of spatial and travel behaviour in addition to affecting the rate and the pattern of land-use development. However despite the importance of the notion of accessibility, the accessibility measures, which have traditionally been used to quantify accessibility, have tended to be relatively poorly defined, excluding a wide range of observed forms of travel behaviour. This has ramifications for the implicit assumption underpinning the use of accessibility measures, namely that of a direct correlation between the measure of accessibility and individual travel behaviour. In this paper a hitherto unknown family of space-time route benefit measures are developed and utilised to derive an associated family of disaggregate activity based space-time utility accessibility measures. Applicable to individual activity schedules, these space-time activity accessibility measures implicitly acknowledge that travel is a derived demand. The paper commences with an outline of the limitations and primary assumptions present within traditional accessibility measures. The paper proceeds to provide a brief review of space-time user benefit measures highlighting their principle assumptions. Existing space-time locational benefit measures are subsequently extended to incorporate more realistic temporal constraints on activity participation and the perceived user benefit. The improved locational benefit measures incorporate a variety of factors including the utility an individual derives from activity participation, individual income, space-time constraints. In addition travel time, route delay and schedule disutility components such as the facility and activity wait times associated with early arrival are incorporated, in addition to late start time penalties associated with late commencement of an activity. The improved space-time locational benefit measure is subsequently applied to activity schedules incorporating a series of multiple linked activities. The paper subsequently demonstrates how the resulting user benefit measure can be shown to be part of a broader family of space-time route benefit measures, which despite their theoretical attractiveness have hitherto not been utilised by researchers. An associated family of space-time utility accessibility measures are subsequently developed and the paper proceeds to highlight how stochastic frontier models utilised in conjunction with existing travel/activity diary datasets can be utilised to operationalise the proposed measure of accessibility. The proposed family of accessibility measures are implemented within a point based spatial framework encompassing detailed spatially referenced land-use transportation network encompassing public transport, cycle, walk and car transport modes. Several practical examples are presented of the proposed family of accessibility measures in use and in particular demonstrate the strength and potential of the methodology in developing a wide range of transport-land-use policies. Examples are presented of the use of the methodology in developing new/improved transport links and services, the provision of additional land-use facilities/opportunities, extended opening of facilities/opportunities, the identification of transport related social exclusion, the development of equitable land-use transport schemes and policies as well as the development of flexible working policies. The paper concludes with a summary highlighting the principle benefits and properties of the proposed family of accessibility measures in addition to highlighting potential areas of future research.

Development and Application of an Activity Based Space-Time Accessibility Measure for Individual Activity Schedules

Accessibility is an important aspect of human existence impacting on our notion of society equity and justice. It plays an important role in a number of existing theories of spatial and travel behaviour in addition to affecting the rate and the pattern of land-use development. However despite the importance of the notion of accessibility, the accessibility measures, which have traditionally been used to quantify accessibility, have tended to be relatively poorly defined, excluding a wide range of observed forms of travel behaviour. This has ramifications for the implicit assumption underpinning the use of accessibility measures, namely that of a direct correlation between the measure of accessibility and individual travel behaviour. In this paper a hitherto unknown family of space-time route benefit measures are developed and utilised to derive an associated family of disaggregate activity based space-time utility accessibility measures. Applicable to individual activity schedules, these space-time activity accessibility measures implicitly acknowledge that travel is a derived demand. The paper commences with an outline of the limitations and primary assumptions present within traditional accessibility measures. The paper proceeds to provide a brief review of space-time user benefit measures highlighting their principle assumptions. Existing space-time locational benefit measures are subsequently extended to incorporate more realistic temporal constraints on activity participation and the perceived user benefit. The improved locational benefit measures incorporate a variety of factors including the utility an individual derives from activity participation, individual income, space-time constraints. In addition travel time, route delay and schedule disutility components such as the facility and activity wait times associated with early arrival are incorporated, in addition to late start time penalties associated with late commencement of an activity. The improved space-time locational benefit measure is subsequently applied to activity schedules incorporating a series of multiple linked activities. The paper subsequently demonstrates how the resulting user benefit measure can be shown to be part of a broader family of space-time route benefit measures, which despite their theoretical attractiveness have hitherto not been utilised by researchers. An associated family of space-time utility accessibility measures are subsequently developed and the paper proceeds to highlight how stochastic frontier models utilised in conjunction with existing travel/activity diary datasets can be utilised to operationalise the proposed measure of accessibility. The proposed family of accessibility measures are implemented within a point based spatial framework encompassing detailed spatially referenced land-use transportation network encompassing public transport, cycle, walk and car transport modes. Several practical examples are presented of the proposed family of accessibility measures in use and in particular demonstrate the strength and potential of the methodology in developing a wide range of transport-land-use policies. Examples are presented of the use of the methodology in developing new/improved transport links and services, the provision of additional land-use facilities/opportunities, extended opening of facilities/opportunities, the identification of transport related social exclusion, the development of equitable land-use transport schemes and policies as well as the development of flexible working policies. The paper concludes with a summary highlighting the principle benefits and properties of the proposed family of accessibility measures in addition to highlighting potential areas of future research

Third Down with a Yard to Go: The Dixit-Skeath Conundrum on Equilibria in Competitive Games.

In strictly competitive games, equilibrium mixed strategies are invariant to changes in the ultimate prizes. Dixit & Skeath (1999) argue that this seems counter-intuitive. We show that this invariance is robust to dropping the independence axiom, but is removed if we drop the reduction axiom.GAME THEORY ; COMPETITION ; EXPECTATIONS

Local dissipation effects in two-dimensional quantum Josephson junction arrays with magnetic field

We study the quantum phase transitions in two-dimensional arrays of Josephson-couples junctions with short range Josephson couplings (given by the Josephson energy) and the charging energy. We map the problem onto the solvable quantum generalization of the spherical model that improves over the mean-field theory method. The arrays are placed on the top of a two-dimensional electron gas separated by an insulator. We include effects of the local dissipation in the presence of an external magnetic flux f in square lattice for several rational fluxes f=0,1/2,1/3,1/4 and 1/6. We also have examined the T=0 superconducting-insulator phase boundary as function of a dissipation alpha for two different geometry of the lattice: square and triangular. We have found critical value of the dissipation parameter independent on geometry of the lattice and presence magnetic field.Comment: accepted to PR

On an extremal problem for poset dimension

Let $f(n)$ be the largest integer such that every poset on $n$ elements has a $2$-dimensional subposet on $f(n)$ elements. What is the asymptotics of $f(n)$? It is easy to see that $f(n)\geqslant n^{1/2}$. We improve the best known upper bound and show $f(n)=\mathcal{O}(n^{2/3})$. For higher dimensions, we show $f_d(n)=\mathcal{O}\left(n^\frac{d}{d+1}\right)$, where $f_d(n)$ is the largest integer such that every poset on $n$ elements has a $d$-dimensional subposet on $f_d(n)$ elements.Comment: removed proof of Theorem 3 duplicating previous work; fixed typos and reference

Slow relaxation, confinement, and solitons

Millisecond crystal relaxation has been used to explain anomalous decay in doped alkali halides. We attribute this slowness to Fermi-Pasta-Ulam solitons. Our model exhibits confinement of mechanical energy released by excitation. Extending the model to long times is justified by its relation to solitons, excitations previously proposed to occur in alkali halides. Soliton damping and observation are also discussed

Accident of Birth, Life Chances adn the Impartial Observer

We confront two common objections to Harsanyi's impartial observer theorem: one to do with 'fairness', and the other to do with different individuals' having different attitudes toward risk. Both these objections can be accommodated if we drop the reduction axiom: in particular, if we distinguish between 'accidents of birth' and real-world 'life chances'. We do not drop the independence axiom that has often been seen as the source of these problems. Just as Harsanyi's theorem yields a utilitarian form of social welfare function, so our approach axiomatizes a generalized utilitarian form. If in addition, welfare is cardinally measurable, then we can interpret the shape of our generalized utilitarian functional from in terms of attitudes toward risk and toward interim inequality.

Compositional Design and Verification of a Multi-Agent System for One-to-Many Negotiation

A compositional verification method for multi-agent systems is presented and applied to a multi-agent system for one-to-many negotiation in the domain of load balancing of electricity use. Advantages of the method are that the complexity of the verification process is managed by compositionality, and that parts of the proofs can be reused in relation to reuse of components

Limits on the Dipole Moments of the τ\tau-Lepton via the Process $e^{+}e^{-}\to \tau^+ \tau^- \gamma in a Left-Right Symmetric Model

Limits on the anomalous magnetic moment and the electric dipole moment of the $\tau$ lepton are calculated through the reaction $e^{+}e^{-}\to \tau^+ \tau^- \gamma$ at the $Z_1$-pole and in the framework of a left-right symmetric model. The results are based on the recent data reported by the L3 Collaboration at CERN LEP. Due to the stringent limit of the model mixing angle $\phi$, the effect of this angle on the dipole moments is quite small.Comment: 15 pages, 3 figure