Natural inflation and moduli stabilization in heterotic orbifolds

We study moduli stabilization in combination with inflation in heterotic orbifold compactifications in the light of a large Hubble scale and the favored tensor-to-scalar ratio $r \approx 0.05$. To account for a trans-Planckian field range we implement aligned natural inflation. Although there is only one universal axion in heterotic constructions, further axions from the geometric moduli can be used for alignment and inflation. We argue that such an alignment is rather generic on orbifolds, since all non-perturbative terms are determined by modular weights of the involved fields and the Dedekind $\eta$ function. We present two setups inspired by the mini-landscape models of the $\mathbb Z_{6-\text{II}}$ orbifold which realize aligned inflation and stabilization of the relevant moduli. One has a supersymmetric vacuum after inflation, while the other includes a gaugino condensate which breaks supersymmetry at a high scale.Comment: 17 pages, 5 tables, comments and references adde

Inflation with Fayet-Iliopoulos Terms

Two of the most attractive realizations of inflation in supergravity are based upon the presence of a constant Fayet-Iliopoulos (FI) term. In D-term hybrid inflation it is the FI term itself which sets the energy scale of inflation. Alternatively, the breaking of a U(1) symmetry induced by the FI term can dynamically generate the quadratic potential of chaotic inflation. The purpose of this note is to study the possible UV embedding of these schemes in terms of the `field-dependent FI term' related to a string modulus field which is stabilized by a non-perturbative superpotential. We find that in settings where the FI term drives inflation, gauge invariance prevents a decoupling of the modulus from the inflationary dynamics. The resulting inflation models generically contain additional dynamical degrees of freedom compared to D-term hybrid inflation. However, the dynamical realization of chaotic inflation can be obtained in complete analogy to the case of a constant FI term. We present a simple string-inspired toy model of this type.Comment: 20 pages, accepted for publication in PR

Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition

We study one-dimensional transport in focused-ion-beam written in-plane-gate transistors on III-V heterostructures at moderately low temperatures at zero bias without any external magnetic field applied. In accordance with a recent proposal of A. Gold and L. Calmels, Valley- and spin-occupancy instability in the quasi-one-dimensional electron gas, Phil. Mag. Lett. 74, 33-42 (1996) and earlier experimental data, we observe plateaux in the source-drain conductivity considered as a function of the gate voltage, not only at multliples of 2e^2/h but also clearly at e^2/h, just before the channel closes to zero conductivity. This may be interpreted as a many electron effect, namely as a novel ballistic ferromagnetic ground state evading standard descriptions and theorems.Comment: 19 pages, 9 figures, 22 reference

The Bioterrorism Act of the USA and international food trade: evaluating WTO conformity and effects on bilateral imports

The September 11th event focused the world’s attention on the threat of bioterrorism on the food chain. As a consequence, the USA implemented the Bioterrorism Act (BTA) containing new import requirements that can be classified as non-tariff barriers (NTBs). This paper analyses these NTBs by performing an assessment of WTO conformity and trade impact: hereby general problems in the analysis of bioterrorist risks are explored as for this new and unknown threat explicit WTO rules are still missing. Additionally, in exploring the BTA relevant process standard rules laid out by the WTO, the analysis indicates the extensive flexibility provided in this framework. This leads to larger scope for national polices on process standards compared to product standards (e.g. residua levels). The empirical trade flow analysis illustrates differences in the compliance costs between countries. This differentiation can be caused by learning costs that may differ among countries. The analysis highlights that perishable products and countries with small import quantities are mostly affected.food terrorism, non-tariff barriers, trade facilitation, Bioterrorism Act, international food trade, SPS Agreement, International Relations/Trade,

Single-hole transistor in p-type GaAs/AlGaAs heterostructures

A single-hole transistor is patterned in a p-type, C-doped GaAs/AlGaAs heterostructure by AFM oxidation lithography. Clear Coulomb blockade resonances have been observed at T=300 mK. A charging energy of ~ 1.5 meV is extracted from Coulomb diamond measurements, in agreement with the lithographic dimensions of the dot. The absence of excited states in Coulomb diamond measurements, as well as the temperature dependence of Coulomb peak heights indicate that the dot is in the multi-level transport regime. Fluctuations in peak spacings larger than the estimated mean single-particle level spacing are observed.Comment: 4 pages, 5 figure

Challenges for D-brane large-field inflation with stabilizer fields

We study possible string theory compactifications which, in the low-energy limit, describe chaotic inflation with a stabilizer field. We first analyze type IIA setups where the inflationary potential arises from a D6-brane wrapping an internal three-cycle, and where the stabilizer field is either an open-string or bulk K\"ahler modulus. We find that after integrating out the relevant closed-string moduli consistently, tachyonic directions arise during inflation which cannot be lifted. This is ultimately due to the shift symmetries of the type IIA K\"ahler potential at large compactification volume. This motivates us to search for stabilizer candidates in the complex structure sector of type IIB orientifolds, since these fields couple to D7-brane Wilson lines and their shift symmetries are generically broken away from the large complex structure limit. However, we find that in these setups the challenge is to obtain the necessary hierarchy between the inflationary and Kaluza-Klein scales.Comment: 26 pages, typos corrected and comments added. Published versio

Welfare distribution between EU Member States through different national decoupling options. Implications for Spain

SUMMARY: This paper makes use of an agricultural sector model to analyse welfare effects derived from different national implementation options of the CAP Reform 2003. It shows that agricultural prices developed more favourable in a full premium decoupling scenario, since agricultural production declines more pronounced compared to a partial decoupling scenario. The use of the partial decoupling mechanism helps Member States to distribute income into less favoured areas but is not the optimal policy choice. However, if other Member States follow the same path of reform, a "prisoner's dilemma" will most likely be observed: partial decoupling appears as the preferred option for individual Member States, since high domestic production and high producer prices would be expected, but this would lead to welfare losses for consumers and taxpayers. Distribución de bienestar económico entre Estados Miembros ante distintas opciones de desacoplamiento en el marco de la nueva PAC – Consecuencias para España RESUMEN: Este trabajo modeliza los efectos en el bienestar económico derivados de distintas op-ciones de desacoplamiento de las primas contenidas en la reforma de la Política Agraria Común apro-bada tras los Acuerdos de Luxemburgo en 2003. Se observa como bajo un escenario de pleno desaco-plamiento, los precios agrarios evolucionan más favorablemente que bajo un desacoplamiento parcial debido a una caída de la producción más pronunciada. El uso del mecanismo de desacoplamiento par-cial permite a los estados miembros mantener determinados cultivos en zonas marginales, lo que resul-ta en una solución no óptima. Si los demás países siguieran el mismo camino de reforma, podría surgir un problema tipo "dilema del prisionero". La opción de desacoplamiento parcial aparecería como la opción preferida desde el punto de vista individual al asegurar una mayor producción doméstica y altos precios de producción. No obstante, a nivel agregado, el resultado sería una reducción de renta de consumidores y contribuyentes. PALABRAS CLAVE: Política Agraria Común, análisis de equilibrio parcial, modelización, desaco-plamiento, análisis de bienestar.Common Agricultural Policy, partial equilibrium analysis, modelling, decoupling, welfare analysis., Agricultural and Food Policy, C61, D60, Q18,