The D4-D8 Brane System and Five Dimensional Fixed Points

We construct dual Type I' string descriptions to five dimensional supersymmetric fixed points with $E_{N_f+1}$ global symmetry. The background is obtained as the near horizon geometry of the D4-D8 brane system in massive Type IIA supergravity. We use the dual description to deduce some properties of the fixed points.Comment: 10 pages, LaTeX2e; improved references, corrected typo

Free Riding on Altruism and Group Size

It is shown that altruism does not affect the equilibrium provision of public goods although altruism takes the form of unconditional commitment to contribute. The reason is that altruistic contributions completely crowd out selfish contributions. That is, egoists free ride on altruism. It is also shown that public goods are less likely to be provided in larger groups.Free Riding, Public good, Altruism

The W3W_3-string spectrum

We study the spectrum of $W_3$ strings. In particular, we show that for appropriately chosen space-time signature, one of the scalar fields is singled out by the spin-3 constraint and is ``frozen'': no creation operators from it can appear in physical states and the corresponding momentum must assume a specific fixed value. The remaining theory is unitary and resembles an ordinary string theory in $d\ne26$ with anomalies cancelled by appropriate background charges. In the case of the $W_3$ string, however, the spin-two ``graviton'' is massive.Comment: 14 Page

Schelling's Spatial Proximity Model of Segregation Revisited

Schelling [1969, 1971a, 1971b, 1978] presented a microeconomic model showing how an integrated city could unravel to a rather segregated city, notwithstanding relatively mild assumptions concerning the individual agents' preferences, i.e., no agent preferring the resulting segregation. We examine the robustness of Schelling's model, focusing in particular on its driving force: the individual preferences. We show that even if all individual agents have a strict preference for perfect integration, best-response dynamics will lead to segregation. What is more, we argue that the one-dimensional and two-dimensional versions of Schelling's spatial proximity model are in fact two qualitatively very different models of segregation.Neighborhood segregation, Myopic Nash Equilibria, Best-response dynamics, Markov chain, Limit-behavior.

A comment on the magical realizations of W_3

In the process of investigating classical realizations of W_3 in terms of free bosons, Romans unveiled a relation to finite-dimensional Jordan algebras with a cubic norm. These algebras have been classified and consist of an infinite series (yielding the ``generic'' realizations) and four sporadic algebras associated to the real division algebras (which yield the ``magical'' realizations). The generic realizations were shown by Romans to quantize, who left the problem of the quantization of the magical realizations open. In later work, Mohammedi showed that the first two magical realizations did not survive quantization. In this note we close the problem by showing that neither do the other two magical realizations.Comment: .dvi file + 1 EPS figure, 10 document pages but 5 physical page

What Makes a Good Conference? Analysing the Preferences of Labor Economists

Conferences are an important element in the work of researchers, requiring substantial investments in fees, travel expenses and the time spent by the participants. The aim of this paper is to identify the preferences of participants with respect to conference characteristics. Based on a sample of European labour economists, preferences are measured using the vignette approach where participants are asked to choose between hypothetical European Association of Labour Economists (EALE) conferences. We find that the keynote speakers are the most important element in the preference for a conference, followed by the location of the conference. There is substantial heterogeneity in the taste of labour economists especially with respect to location, though the link between preference parameters and measured characteristics like gender, age and seniority is limited. Factor analysis suggests that the variety in preferences can be best described by a latent variable that reflects the weights people put on content versus fun.vignette-method, economics profession, conference participation, random-coefficients model

Ballistic Josephson junctions based on CVD graphene

Josephson junctions with graphene as the weak link between superconductors have been intensely studied in recent years, with respect to both fundamental physics and potential applications. However, most of the previous work was based on mechanically exfoliated graphene, which is not compatible with mass production. Here we present our research using graphene grown by chemical vapour deposition (CVD) as the weak link of Josephson junctions. We demonstrate that CVD-graphene-based Josephson junctions with Nb electrodes can work effectively without any thermal hysteresis from 1.5 K down to a base temperature of 320 mK, and they show an ideal Fraunhofer-like interference pattern in a perpendicular magnetic field. We also show that the critical current of the junction can be tuned by a gate voltage. Furthermore, for our shortest junctions (50 nm in length), we find that the normal state resistance oscillates with the gate voltage, indicating that the junctions are in the ballistic regime, a feature not previously observed in CVD-graphene-based Josephson junctions.Comment: 14 pages, 4 figure

What makes a good conference? Analysing the preferences of labor economists

Conferences are an important element in the work of researchers, requiring substantial investments in fees, travel expenses and the time spent by the participants. The aim of this paper is to identify the preferences of participants with respect to conference characteristics. Based on a sample of European labour economists, preferences are measured using the vignette approach where participants are asked to choose between hypothetical European Association of Labour Economists (EALE) conferences. We find that the keynote speakers are the most important element in the preference for a conference, followed by the location of the conference. There is substantial heterogeneity in the taste of labour economists especially with respect to location, though the link between preference parameters and measured characteristics like gender, age and seniority is limited. Factor analysis suggests that the variety in preferences can be best described by a latent variable that reflects the weights people put on content versus fun.labour economics ;