"Stability of Spatial Equilibrium"

This paper focuses on externalities between economic agents. We consider spatial dis- tribution of economic activities in a multiregional dynamical system, where regions may be interpreted as clubs, social subgroups, species, or strategies. Our dynamics includes gravity models and replicator dynamics as special cases. Assuming that other variables, such as prices are solved as a function of the population distribution, we analyze both interior and corner equilibria of spatial distribution in a general class of dynamics, including the replicator dynamics and the gravity model. We derive the exact conditions for stable equilibrium and give some interpretations of the stability conditions. We show that interior equilibria are stable in the presence of strong agglomeration economies, but unstable in the presence of strong congestion diseconomies.

The Home Market Effect and the Agricultural Sector

The "home market effect" (HME) is an essential topic of the new trade theory. Assuming the transport costs only for the manufacturing goods, Krugman (1980) shows that the country with bigger market size is a net exporter. The assumption of free transport of the agricultural good was shown mattering a great deal rather than being innocuous by Davis (1998). Particularly, when manufacturing and agricultural goods have identical transport costs, the HME disappears. However, we find that the homogeneous-agricultural-good assumption in Davis' model derives the discontinuity of inverse demand functions, which causes the disappearance of the HME. After establishing an analytical solvable model and assuming two differentiated agricultural goods in two countries, we find that the HME does exist even if the transport cost of the agricultural goods is positive.

Regional Specialization via Differences in Transport Costs

This paper examines a new economic geography model with multiple (three) industries and urban costs. The industries are asymmetric in their transport costs. The following results were obtained. First, if transport costs sufficiently decrease whereas commuting costs are constant, we have three stable location patterns; full dispersion, partial regional specialization, and complete regional specialization. Second, if commuting costs sufficiently decrease (resp. increase) whereas transport costs are constant, we have full agglomeration (resp. full dispersion). The cases with medium value of transport and commuting costs and with multiple (three) regions are analyzed by use of numerical simulation.

Economic Integration and Welfare: Manufacturing vs. Agricultural Markets

In the literature of new trade theory, most papers study the industrial location by imposing the assumption of free transportation in the agricultural sector. This paper explicitly incorporates arbitrary transport costs in both the manufacturing and the agricultural sectors into the Helpman-Krugman-Davis model of two countries and one production factor. The following results are obtained. First, we find a necessary and sufficient condition for the home market effect (HME) to be observed. Secondly, we find that integrating manufacturing markets has contrastive impacts on two countries to integrating agricultural markets. Our results are suggestive for the understanding of various international trade agreements.

Electromagnetic Lens-focusing Antenna Enabled Massive MIMO: Performance Improvement and Cost Reduction

Massive multiple-input multiple-output (MIMO) techniques have been recently advanced to tremendously improve the performance of wireless communication networks. However, the use of very large antenna arrays at the base stations (BSs) brings new issues, such as the significantly increased hardware and signal processing costs. In order to reap the enormous gain of massive MIMO and yet reduce its cost to an affordable level, this paper proposes a novel system design by integrating an electromagnetic (EM) lens with the large antenna array, termed the EM-lens enabled MIMO. The EM lens has the capability of focusing the power of an incident wave to a small area of the antenna array, while the location of the focal area varies with the angle of arrival (AoA) of the wave. Therefore, in practical scenarios where the arriving signals from geographically separated users have different AoAs, the EM-lens enabled system provides two new benefits, namely energy focusing and spatial interference rejection. By taking into account the effects of imperfect channel estimation via pilot-assisted training, in this paper we analytically show that the average received signal-to-noise ratio (SNR) in both the single-user and multiuser uplink transmissions can be strictly improved by the EM-lens enabled system. Furthermore, we demonstrate that the proposed design makes it possible to considerably reduce the hardware and signal processing costs with only slight degradations in performance. To this end, two complexity/cost reduction schemes are proposed, which are small-MIMO processing with parallel receiver filtering applied over subgroups of antennas to reduce the computational complexity, and channel covariance based antenna selection to reduce the required number of radio frequency (RF) chains. Numerical results are provided to corroborate our analysis.Comment: 30 pages, 9 figure

Complete analysis of hyperentangled Bell state in three degrees of freedom

We present an efficient scheme for the complete hyperentangled Bell state analysis (HBSA) of photon system in polarization and two longitudinal momentum degrees of freedom (DOFs). In the process of distinguishing the 64 hyperentangled Bell states in three DOFs, the weak cross-Kerr nonlinearity and self-assisted mechanism are both utilized, which can make our scheme simple and realizable. We also discuss the application of this complete HBSA scheme in quantum teleportation that based on hyperentangled state in three DOFs