"The Finance Constraint Theory of Money: A Progress Report"

The theory of money that emerged from the Keynesian Revolution is coming increasingly into question, and a variety of new theories are being put forward as alternatives. The most promising is one I will call the finance constraint theory. This paper is a progress report on its development. It is particularly fitting that this progress report appear in afestschrift for S.C. Tsiang, as he has been one of the most cogent critics of the conventional theory and a major architect of the finance constraint alternative. The issues a theory of money should address may be divided into three broad areas: (1) What is money and how is it special (2) What is the connection between money and its various "prices" (the general price level, interest rates, and exchange rates)? (3) What is the role of money in economic fluctuations? After some introductory material, each of these areas will be taken up in turn.

Local moment formation in quantum point contacts

Spin-density-functional theory of quantum point contacts (QPCs) reveals the formation of a local moment with a net of one electron spin in the vicinity of the point contact - supporting the recent report of a Kondo effect in a QPC. The hybridization of the local moment to the leads decreases as the QPC becomes longer, while the onsite Coulomb-interaction energy remains almost constant.Comment: 10 pages, 3 figures, accepted for publication in Physical Review Letter

Kondo model for the "0.7 anomaly" in transport through a quantum point contact

Experiments on quantum point contacts have highlighted an anomalous conductance plateau at $0.7 (2e^2/h)$, with features suggestive of the Kondo effect. Here we present an Anderson model for transport through a point contact which we analyze in the Kondo limit. Hybridization to the band increases abruptly with energy but decreases with valence, so that the background conductance and the Kondo temperature $T_K$ are dominated by different valence transitions. This accounts for the high residual conductance above $T_K$. A spin-polarized current is predicted for Zeeman splitting $g^* \mu_B B > k_B T_K,k_BT$.Comment: 4 page

Radiation dose optimized lateral expansion of the field of view in synchrotron radiation X-ray tomographic microscopy

Increasing the lateral field of view of tomography-based imaging methods greatly increases the acquisition time. This article presents scanning protocols to obtain high-resolution tomographic scans with large lateral field of view at greatly decreased acquisition time and thus reduced radiation dose while resulting in high-quality three-dimensional tomographic datasets

The 2-Channel Kondo Model II: CFT Calculation of Non-Equilibrium Conductance through a Nanoconstriction containing 2-Channel Kondo Impurities

Recent experiments by Ralph and Buhrman on zero-bias anomalies in quenched Cu nanoconstrictions (reviewed in the preceding paper, I), are in accord with the assumption that the interaction between electrons and nearly degenerate two-level systems in the constriction can be described, for sufficiently small voltages and temperatures (V,T < \Tk), by the 2-channel Kondo (2CK) model. Motivated by these experiments, we introduce a generalization of the 2CK model, which we call the nanoconstriction 2-channel Kondo model (NTKM), that takes into account the complications arising from the non-equilibrium electron distribution in the nanoconstriction. We calculate the conductance $G(V,T)$ of the constriction in the weakly non-equilibrium regime of V,T \ll \Tk by combining concepts from Hershfield's $Y$-operator formulation of non-equilibrium problems and Affleck and Ludwig's exact conformal field theory (CFT) solution of the 2CK problem (CFT technicalities are discussed in a subsequent paper, III). Finally, we extract from the conductance a universal scaling curve $\Gamma(v)$ and compare it with experiment. Combining our results with those of Hettler, Kroha and Hershfield, we conclude that the NTKM achieves quantitative agreement with the experimental scaling data.Comment: Final published version (minor revisions only), 41 pages RevTeX, 9 encapsulated postscript figure

Theory of Transmission through disordered superlattices

We derive a theory for transmission through disordered finite superlattices in which the interface roughness scattering is treated by disorder averaging. This procedure permits efficient calculation of the transmission thr ough samples with large cross-sections. These calculations can be performed utilizing either the Keldysh or the Landauer-B\"uttiker transmission formalisms, both of which yield identical equations. For energies close to the lowest miniband, we demonstrate the accuracy of the computationally efficient Wannier-function approximation. Our calculations indicate that the transmission is strongly affected by interface roughness and that information about scale and size of the imperfections can be obtained from transmission data.Comment: 12 pages, 6 Figures included into the text. Final version with minor changes. Accepted by Physical Review

Time-Dependent Partition-Free Approach in Resonant Tunneling Systems

An extended Keldysh formalism, well suited to properly take into account the initial correlations, is used in order to deal with the time-dependent current response of a resonant tunneling system. We use a \textit{partition-free} approach by Cini in which the whole system is in equilibrium before an external bias is switched on. No fictitious partitions are used. Besides the steady-state responses one can also calculate physical dynamical responses. In the noninteracting case we clarify under what circumstances a steady-state current develops and compare our result with the one obtained in the partitioned scheme. We prove a Theorem of asymptotic Equivalence between the two schemes for arbitrary time-dependent disturbances. We also show that the steady-state current is independent of the history of the external perturbation (Memory Loss Theorem). In the so called wide-band limit an analytic result for the time-dependent current is obtained. In the interacting case we propose an exact non-equilibrium Green function approach based on Time Dependent Density Functional Theory. The equations are no more difficult than an ordinary Mean Field treatment. We show how the scattering-state scheme by Lang follows from our formulation. An exact formula for the steady-state current of an arbitrary interacting resonant tunneling system is obtained. As an example the time-dependent current response is calculated in the Random Phase Approximation.Comment: final version, 18 pages, 9 figure

Formulae for zero-temperature conductance through a region with interaction

The zero-temperature linear response conductance through an interacting mesoscopic region attached to noninteracting leads is investigated. We present a set of formulae expressing the conductance in terms of the ground-state energy or persistent currents in an auxiliary system, namely a ring threaded by a magnetic flux and containing the correlated electron region. We first derive the conductance formulae for the noninteracting case and then give arguments why the formalism is also correct in the interacting case if the ground state of a system exhibits Fermi liquid properties. We prove that in such systems, the ground-state energy is a universal function of the magnetic flux, where the conductance is the only parameter. The method is tested by comparing its predictions with exact results and results of other methods for problems such as the transport through single and double quantum dots containing interacting electrons. The comparisons show an excellent quantitative agreement.Comment: 18 pages, 18 figures; to appear in Phys. Rev.

Inducement of Spin-pairing and Correlated Semi-metallic State in Mott-Hubbard Quantum Dot Array

We model a quantum dot-array (with one electron per dot) comprising of two (or more than two) coupled dots by an extended Hubbard Hamiltonian to investigate the role played by the inter-dot tunneling amplitude td, together with intra-dot (U) and inter-dot(U1) coulomb repulsions, in the singlet / triplet bound state formation and evolution of the system from the Mott-insulator-like state to a correlated semi-metallic state via charge-bond-order route. In the presence of magnetic field, td is complex due to the appearance of Peierls phase factor. We introduce a short-ranged inter-dot capacitive coupling U0, assumed to be non-zero for nearest-neighbor dots only, for the bound state analysis. The study indicates that, while for the tunable parameter d = (2td/U0) greater than unity only the possibility of the triplet bound state formation exists, for d less than one both triplet and singlet states are possible. The bound states are formed due to tunneling and capacitive dot-bondings with coulomb interactions (U,U1) playing marginal role. The interaction U, however, is found to play, together with complex td, an important role in the evolution of the double quantum dot system from the insulator-like state to that of a correlated semi-metallic state through charge-bond-ordering route.Comment: 18 pages,4 figure