Supersymmetric Gauge Theories from Branes and Orientifold Six-planes

We study brane configurations in the presence of orientifold six-planes. After deriving the curves for N=2 supersymmetric SU(Nc) gauge theories with one flavor in the symmetric or antisymmetric representation and Nf fundamental flavors, we rotate the brane configuration, reducing the supersymmetry to N=1. For the case of an antisymmetric flavor and less than two fundamental flavors, nonperturbative effects lead to a brane configuration that is topologically a torus. Using the description of the orientifold six-planes as Dn singularities we discuss the Higgs branches for N=2 brane configurations with Sp/SO gauge groups and the related N=1 theories with tensor representations.Comment: 30 pages (harvmac b-mode), 5 figures, (v2 minor corrections), (v3 sign error corrected

Duality of Chiral N=1 Supersymmetric Gauge Theories via Branes

Using a six-orientifold on top of a NS-fivebrane we construct a chiral N=1 supersymmetric gauge theory in four dimensions with gauge group SU(N_c) and matter in the symmetric, antisymmetric and (anti)fundamental representations. Anomaly cancellation is fulfilled by the requirement of a smooth RR 7-form charge distribution and leads us to the introduction of 8 half D-sixbranes ending on the NS-fivebrane. We obtain the dual model from branes by a linking number argument. We check explicitly the 't Hooft anomaly matching conditions and the map between deformations in the original and the dual model.Comment: 16 pages, 2 figures, TeX, harvmac, table

Fate of the spin-\frac{1}{2} Kondo effect in the presence of temperature gradients

We consider a strongly interacting quantum dot connected to two leads held at quite different temperatures. Our aim is to study the behavior of the Kondo effect in the presence of large thermal biases. We use three different approaches, namely, a perturbation formalism based on the Kondo Hamiltonian, a slave-boson mean-field theory for the Anderson model at large charging energies and a truncated equation-of-motion approach beyond the Hartree-Fock approximation. The two former formalisms yield a suppression of the Kondo peak for thermal gradients above the Kondo temperature, showing a remarkably good agreement despite their different ranges of validity. The third technique allows us to analyze the full density of states within a wide range of energies. Additionally, we have investigated the quantum transport properties (electric current and thermocurrent) beyond linear response. In the voltage-driven case, we reproduce the split differential conductance due to the presence of different electrochemical potentials. In the temperature-driven case, we observe a strongly nonlinear thermocurrent as a function of the applied thermal gradient. Depending on the parameters, we can find nontrivial zeros in the electric current for finite values of the temperature bias. Importantly, these thermocurrent zeros yield direct access to the system's characteristic energy scales (Kondo temperature and charging energy).Comment: 14 pages, 11 figures, revised versio

The Effects of Economic Factors in Determining the Transition Process in Europe and Central Asia

This paper examines how economic determinants affect foreign direct investment into a sample of Western European and transition countries from 1990 to 2003. The observed differences in the flow of foreign investment into the transition countries, relative to those in Western Europe, provokes the question of whether this phenomenon was determined by the economic factors present in those countries. Using a conceptual model constructed from economic factors that affect FDI inflows, this study considers the sample set for two sub-periods in the transition process, namely the early period from 1990 to 1998 and the later period from 1998 to 2003. In the first period, economic factors do not account for comparatively higher rates of capital inflows into the Central European and former Soviet economies. This result is reconciled with the obvious difference observed in reality, by suggesting that the higher than expected FDI flows into the transition countries of Central Europe specifically were due to the transition process. In the second period, the rates of capital inflow remain relatively similar between Western and Central European economies, though the former Soviet economies were shown to experience different rates of FDI inflows based on the economic factors specified. The lack of difference between Central European and Western European FDI flows proves that the transition period had come to any end by 2003 for Poland, Hungary and the Czech Republic

The Arkisys Port Module: An Orbital Platform for Hosted Payloads in Low-Earth Orbit

Advances in Small Satellite technology combined with the availability of low-cost rideshares to Low-Earth Orbit (LEO) have led to an increasing number of space missions. However, the underlying technology for small payload missions has been relatively constant over the past two decades: CubeSat form factor platforms for free-flying missions in LEO. Arkisys is working to change this, and allow a wider variety of payloads to reach LEO which don\u27t include an immediate free-flying requirement. This platform is called The Port, and is an autonomous long-duration orbital platform for a multitude of uses, including hosting payloads in LEO. Currently, avenues available to test small experimental payloads in LEO are hosted inside other satellites, or in some cases aboard the International Space Station (ISS) at the ISS National Laboratory. While CubeSats are quite ubiquitous and widely available; the downside is that while they appear low cost, they can be costly for a team who has never developed one before. New companies hosting payloads for customers offer a way to get to space for a limited duration, some even offering to bring them back to Earth. The ISS National Laboratory can support a wider variety of payloads than small satellites alone; however, there is a limited capacity on the ISS, and the missions are limited by human factor constraints. For researchers and commercial developers who want to run small-scale experiments on orbit, on the order of 10 - 200 kg, a long-duration robotic platform which can host these payloads, providing power, data, and thermal control over a standardized docking interface presents a unique opportunity to expand their functional test and operations. On a long duration platform payloads can be situated in an orientation that provides a constant view of the Earth, of deep space, or even a radiation-shielded environment. With a large enough number of payloads on board running at a duty cycle, the per-user cost is able to be brought significantly lower than a one-off small satellite mission for an equivalently sized payload. There is a interesting dichotomy in the use of Cubesat/Small Satellites to support payload testing; the value proposition is typically in building a satellite to last for multiple years, yet many payloads are Technology Readiness Level (TRL) raising demonstrations that only need to run for a matter of months. This results in a potential under-utilization of resources of the satellite. A long-duration platform optimized to allow for any level of maturity of a technology or payload that needs testing on orbit is able to amortize the cost of operation over time and numbers of customers, helping to drive cost down with increased utility and functions passed on to the payload consumer. This paper puts forward Arkisys\u27s alternative approach to hosting new technologies and missions into space that does not require a full satellite to be built and launched, and describes in detail the capabilities and benefits of the Arkisys Port platform as a long-duration orbital platforms to serve short- and medium-term missions to LEO. The goal is to offload some of the existing payload and new technology backlog from the existing methods to accelerate innovation in space technology today