7,973 research outputs found
Extensive ground state entropy in supersymmetric lattice models
We present the result of calculations of the Witten index for a
supersymmetric lattice model on lattices of various type and size. Because the
model remains supersymmetric at finite lattice size, the Witten index can be
calculated using row-to-row transfer matrices and the calculations are similar
to calculations of the partition function at negative activity -1. The Witten
index provides a lower bound on the number of ground states. We find strong
numerical evidence that the Witten index grows exponentially with the number of
sites of the lattice, implying that the model has extensive entropy in the
ground state.Comment: 7 figure
General discussion : Weiner-Wright : Interchange fees in various countries : developments and determinants
Debit cards ; Credit cards
Does trade integration alter monetary policy transmission?
This paper explores the role of trade integration—or openness—for monetary policy transmission in a medium-scale New Keynesian model. Allowing for strategic complementarities in price-setting, we highlight a new dimension of the exchange rate channel by which monetary policy directly impacts domestic inflation. Although the strength of this effect increases with economic openness, it also requires that import prices respond to exchange rate changes. In this case domestic producers find it optimal to adjust their prices to exchange rate changes which alter the domestic currency price of their foreign competitors. We pin down key parameters of the model by matching impulse responses obtained from a vector autoregression on U.S. time series relative to an aggregate of industrialized countries. While we find evidence for strong complementarities, exchange rate pass-through is limited. Openness has therefore little bearing on monetary transmission in the estimated model
Phenomenological Study of Decoherence in Solid-State Spin Qubits due to Nuclear Spin Diffusion
We present a study of the prospects for coherence preservation in solid-state
spin qubits using dynamical decoupling protocols. Recent experiments have
provided the first demonstrations of multipulse dynamical decoupling sequences
in this qubit system, but quantitative analyses of potential coherence
improvements have been hampered by a lack of concrete knowledge of the relevant
noise processes. We present simulations of qubit coherence under the
application of arbitrary dynamical decoupling pulse sequences based on an
experimentally validated semiclassical model. This phenomenological approach
bundles the details of underlying noise processes into a single experimentally
relevant noise power spectral density. Our results show that the dominant
features of experimental measurements in a two-electron singlet-triplet spin
qubit can be replicated using a noise power spectrum associated
with nuclear-spin-flips in the host material. Beginning with this validation we
address the effects of nuclear programming, high-frequency nuclear-spin
dynamics, and other high-frequency classical noise sources, with conjectures
supported by physical arguments and microscopic calculations where relevant.
Our results provide expected performance bounds and identify diagnostic metrics
that can be measured experimentally in order to better elucidate the underlying
nuclear spin dynamics.Comment: Updated References. Related articles at:
http://www.physics.usyd.edu.au/~mbiercuk/Publications.htm
The Scope of Conflict in International Merger Control
In this paper, we analyse the scope for conflict between national merger control agencies which assert jurisdictions simultaneously. We consider a positive model of merger control in which market definition and the analysis of dominance are both explicitly specified. We find that conflict in international merger control is less likely to occur when economic integration is high. Hence, "globalisation" should alleviate rather than exacerbate conflict. In addition, we observe that conflict is less likely to arise between countries of different size and for extreme policy rules (very lenient or very strict) towards dominance.international antitrust; merger control; extra-territoriality
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