Migration and the diffusion of knowledge in a globalized economy

This paper considers diversity of the knowledge of expats as a complementary dimension of human capital that may generate spillovers. Such, often intangible, knowledge about foreign markets, management skills, and other complementary information may enhance the productivity of these expats, or the people who interact with them. However, due to a lack of knowledge about local culture and language, productivity may also decline. We explore an extensive set of microdata from Statistics Netherlands, and use an augmented Mincer approach to simultaneously identify the private and social returns to the presence of foreign knowledge workers. Private returns are found to be negative and statistically significant, while no evidence for – either negative or positive – social returns is found.

Regional wage differences in the Netherlands: Micro-evidence on agglomeration externalities

Based on micro-data on individual workers for the period 2000–2005, we show that regional wage differentials in the Netherlands are small but present. A large part of these differentials can be attributed to individual characteristics of workers. Remaining effects are partially explained by variations in employment density, with an elasticity of about 3.8 percent and by Marshall-Arrow-Romer externalities, where doubling the share of a (2-digit NACE) industry results in a 2.4 percent higher productivity. We find evidence for a negative effect of competition (associated with Porter externalities) and diversity (associated with Jacobs externalities).

Heterotic warped Eguchi-Hanson spectra with five-branes and line bundles

We consider heterotic strings on a warped Eguchi-Hanson space with five-brane and line bundle gauge fluxes. The heterotic string admits an exact CFT description in terms of an asymmetrically gauged SU(2)xSL(2,R) WZW model, in a specific double scaling limit in which the blow-up radius and the string scale are sent to zero simultaneously. This allows us to compute the perturbative 6D spectra for these models in two independent fashions: i) Within the supergravity approximation we employ a representation dependent index; ii) In the double scaling limit we determine all marginal vertex operators of the coset CFT. To achieve agreement between the supergravity and the CFT spectra, we conjecture that the untwisted and the twisted CFT states correspond to the same set of hyper multiplets in supergravity. This is in a similar spirit as a conjectured duality between asymptotically linear dilaton CFTs and little string theory living on NS-five-branes. As the five-brane charge is non-vanishing, heterotic (anti-)five-branes have to be added in order to cancel irreducible gauge anomalies. The local spectra can be combined in such a way that supersymmetry is preserved on the compact resolved T^4/Z_2 orbifold by choosing the local gauge fluxes appropriately.Comment: 1+36 pages LaTe

A Lorentz invariant doubled worldsheet theory

We propose a Lorentz invariant version of Tseytlin's doubled worldsheet theory that makes T-duality covariance of the string manifest. This theory can be derived as a gauge fixed version of Buscher's gauging procedure, in which the left-over gauge field component acts as a Lagrange multiplier. This description can naturally account for fractional linear O(D,D) transformations of the metric and b-field. It is capable of describing non-geometric backgrounds; geometric and non-geometric fluxes are encoded in the doubled anti-symmetric tensor field strength.Comment: 4 pages LaTeX, no figures, discussion of path integral quantization include

Torus partition functions and spectra of gauged linear sigma models

Worldsheet (0,2) gauged linear sigma models are often used to study supersymmetric heterotic string compactifications with non-trivial vector bundles. We make use of supersymmetric localization techniques to determine their one-loop partition functions. In particular we derive conditions which ensure that the full partition function is modular invariant and we propose a method to determine the massless and massive target space matter spectrum.Comment: 4 pages LaTeX; v2: important technical issue resolved, most results essentially unchange