Subgame-perfect free trade networks in a four-country model

Goyal and Joshi (2006, Int Econ Review) apply the notion of ``pairwise stable networks" introduced by Jackson and Wolinsky (1996, J Econ Theory) to a model of free trade network formation, and show that (i) every pairwise stable network is either complete or almost complete (with all countries except one forming direct links), and (ii) the complete network maximizes global welfare. In this note, we use essentially the same model as their model with four countries, and investigate which network is more likely to be realized than others by considering a dynamic process introduced by Jackson and Watts (2002, J Econ Theory).free trade network, network formation, subgame-perfect equilibrium

Pairwise stable and stochastically stable networks in the four-person co-author model

The co-author model is introduced by Jackson and Wolinsky (1996, Journal of Economic Theory) as a typical example of the models of network formation. In this note, we study which network is pairwise stable and/or stochastically stable when the number of players is four.

Quantum Phase transition under pressure in a heavily hydrogen-doped iron-based superconductor LaFeAsO

Hydrogen (H)-doped LaFeAsO is a prototypical iron-based superconductor. However, its phase diagram extends beyond the standard framework, where a superconducting (SC) phase follows an antiferromagnetic (AF) phase upon carrier doping; instead, the SC phase is sandwiched between two AF phases appearing in lightly and heavily H-doped regimes. We performed nuclear magnetic resonance (NMR) measurements under pressure, focusing on the second AF phase in the heavily H-doped regime. The second AF phase is strongly suppressed when a pressure of 3.0 GPa is applied, and apparently shifts to a highly H-doped regime, thereby a "bare" quantum critical point (QCP) emerges. A quantum critical regime emerges in a paramagnetic state near the QCP, however, the influence of the AF critical fluctuations to the SC phase is limited in the narrow doping regime near the QCP. The optimal SC condition ($T_c \sim$ 48 K) is unaffected by AF fluctuations

High pressure growth and electron transport properties of superconducting SmFeAsO1-xHx single crystals

We report the single crystal growth and characterization of the highest Tc iron-based superconductor SmFeAsO1-xHx. Some sub-millimeter-sized crystals were grown using the mixture flux of Na3As + 3NaH + As at 3.0 GPa and 1473 K. The chemical composition analyses confirmed 10% substitution of hydrogen for the oxygen site (x = 0.10), however, the structural analyses suggested that the obtained crystal forms a multi-domain structure. By using the FIB technique we fabricated the single domain SmFeAsO0.9H0.10 crystal with the Tc of 42 K, and revealed the metallic conduction in in-plane (rhoab), while semiconducting in the out-of-plane (rhoc). From the in-plane Hall coefficient measurements, we confirmed that the dominant carrier of SmFeAsO0.9H0.10 crystal is an electron, and the hydride ion occupied at the site of the oxygen ion effectively supplies a carrier electron per iron following the equation: O2- = H- + e-.Comment: 4 figures, 2 table

Experimental evidence of TcT_c enhancement without the influence of spin fluctuations: NMR study on LaFeAsO_{1-x}H_x under a pressure of 3.0 GPa

The electron-doped high-transition-temperature (T_c) iron-based pnictide superconductor LaFeAsO_{1-x}H_x has a unique phase diagram: superconducting (SC) double domes are sandwiched by antiferromagnetic phases at ambient pressure and they turn to a single dome with a maximum T_c that exceeds 45K at a pressure of 3.0 GPa. We studied whether spin fluctuations are involved in increasing T_c under a pressure of 3.0 GPa by using ^{75}As nuclear magnetic resonance (NMR) technique. The ^{75}As-NMR results for the powder samples show that T_c increases up to 48 K without the influence of spin fluctuations. The fact indicates that spin fluctuations are not involved in raising T_c, which implies that other factors, such as orbital degrees of freedom, may be important for achieving a high T_c of almost 50 K.Comment: Correponding Author: Naoki Fujiwar

Simulating a Simple Real Business Cycle Model Using Excel

Simulating the real business cycle models is a popular topic in first-year graduate courses on macroeconomics. Usually, Maple and Matlab are used for this purpose, mainly because they can be used both for solving and for simulating the models. Strulik (2004) demonstrates that Excel can be used both for solving and for simulating a standard RBC model. In this paper, we propose a more elementary approach that might be suitable for undergraduate courses. We illustrate (i) how to solve a simple RBC model by hand and (ii) how to use Excel to simulate the solution.