10,914 research outputs found
Stability of the spin- kagome ground state with breathing anisotropy
We numerically study the spin- breathing kagome lattice. In this
variation of the kagome Heisenberg antiferromagnet, the spins belonging to
upward and downward facing triangles have different coupling strengths. Using
the density matrix renormalization group (DMRG) method and exact
diagonalization, we show that the kagome antiferromagnet spin liquid is
extremely robust to this anisotropy. Materials featuring this anisotropy -- and
especially the recently studied vanadium compound
(DQVOF) -- may thus be very good candidates to realize the much studied kagome
spin liquid. Further, we closely examine the limit of strong breathing
anisotropy and find indications of a transition to a nematic phase.Comment: 12 pages, 15 figure
Banking reforms, performance and risk in China
We investigate the impact of the banking reform started from 2005 on ownership structures in China on commercial banks’ profitability, efficiency and risk over the period 2000–2012, providing comprehensive evidence on the impact of banking reform in China. We find that banks on average tend to have higher profitability, lower risk and lower efficiency after the reforms, and the results are robust with our difference-in-difference approach. Our results also show that the Big 5 state-owned banks (SOCB) underperform banks with other types of ownership when risk is measured by non-performing loans (NPLs) over the entire study period but tend to have fewer NPLs than other banks during the post-reform period. Our results provide some supporting evidence on the ongoing banking reforms in China, suggesting that attracting strategic foreign investors and listing SOCBs on stock exchanges appear to be effective ways to help SOCBs deal with the problem of NPLs and manage their risk
A Framework for Monitoring Capital Flows in Hong Kong
In this paper we attempt to delineate conceptual issues relating to the definition of capital flows, and introduce a framework that organises survey data and accounting information at different time horizons to form a judgment on the nature and scale of fund flows in Hong Kong. Given the complexity of international financial transactions in Hong Kong, cross-border capital flows may not correspond closely to fund flows into and out of the Hong Kong dollar. A comprehensive view on the scale and nature of capital flows in Hong Kong requires the joint analysis of both monetary and Balance of Payments statistics, in addition to information gathered through market intelligence. We then apply the monitoring framework to analyse four episodes of large fund flows between 2003 and mid-2009.Capital flows; Fund flows; Hong Kong; Balance of Payments; External claims and liabilities of banks; Monetary Survey
RECENT PERFORMANCE OF THE HONG KONG DOLLAR LINKED EXCHANGE RATE SYSTEM
This paper reviews the performance of the Hong Kong dollar Linked Exchange Rate system since the introduction of the three refinements to it in May 2005. It presents an analytical framework which argues that, in a fully credible exchange rate target zone regime, the spot exchange rate normally stays inside the band but does not have a natural tendency to converge towards the centre of the zone. While a certain level of interest rate differential between the Hong Kong dollar and the US dollar may persist, it should not grow significantly larger than what is implied by the width of the Convertibility Zone. Judged against this framework, the developments since May 2005 point to increased credibility of the refined Linked Exchange Rate system.Hong Kong dollar linked exchange rate system
Commodity Markets, Price Limiters and Speculative Price Dynamics
We develop a behavioral commodity market model with consumers, producers and heterogeneous speculators to characterize the nature of commodity price fluctuations and to explore the efectiveness of price stabilization schemes. Within our model, nonlinear interactions between market participants can create either bull or bear markets, or irregular price fluctuations between bulland bear markets. Both the imposition of a bottoming price level (to support producers) or a topping price level (to protect consumers) can reduce market price volatility. However, simple policy rules, such as price limiters, may have unexpected consequences in a complex environment: a minimum price level decreases the average price while a maximum price limit increases the average price. In addition, price limiters influence the price dynamics in an intricate way and may cause volatility clustering.commodity markets; price stabilization; simple limiters; technical and fundamental anaysis; bifurcation analysis; chaos control
Butter Mountains, Milk Lakes and Optimal Price Limiters
It is known that simple price limiters may have unexpected consequences in irregular commodity price fluctuations between bull and bear markets and complicated impacts on the size of buffer stocks. In particular, imposing a lower price boundary may lead to a huge buffer stock, e.g. to a ?butter mountain? or a ?milk lake? and this is a real problem for regulators since storage costs may become impossible to finance over time. The relation between price limiters and the size of buffer stocks is nontrivial and there may exist some optimal price limiters which require only weak market interventions and thus provide a rather inexpensive option to regulate commodity markets. In this paper, we use a simple commodity market model to explore the relation between price limiters and the average growth rate of the buffer stocks. It is found that these optimal price limiter levels are simply the minimum values of unstable periodic orbits of the underlying deterministic system.commodity markets; price stabilization; limiter control; butter mountains and milk lakes
Bosonic Integer Quantum Hall effect in an interacting lattice model
We study a bosonic model with correlated hopping on a honeycomb lattice, and
show that its ground state is a bosonic integer quantum Hall (BIQH) phase, a
prominent example of a symmetry protected topological (SPT) phase. By using the
infinite density matrix renormalization group method, we establish the
existence of the BIQH phase by providing clear numerical evidence: (i) a
quantized Hall conductance with (ii) two counter propagating
gapless edge modes. Our simple model is an example of a novel class of systems
that can stabilize SPT phases protected by a continuous symmetry on lattices
and opens up new possibilities for the experimental realization of these exotic
phases.Comment: 7 pages, 6 figure
Kagome chiral spin liquid as a gauged U(1) symmetry protected topological phase
While the existence of a chiral spin liquid (CSL) on a class of spin-1/2
kagome antiferromagnets is by now well-established numerically, a controlled
theoretical path from the lattice model leading to a low energy topological
field theory is still lacking. This we provide via an explicit construction,
starting from reformulating a microscopic model for a CSL as a lattice gauge
theory, and deriving the low-energy form of its continuum limit. A crucial
ingredient is the realisation that the bosonic spinons of the gauge theory
exhibit a symmetry-protected topological (SPT) phase, which upon
promoting its global symmetry to a local gauge structure ("gauging")
yields the CSL. We suggest that such an explicit lattice-based construction
involving gauging of an SPT phase can be applied more generally to understand
topological spin liquids.Comment: 5+3 pages, 3+4 figure
Signatures of Dirac cones in a DMRG study of the Kagome Heisenberg model
The antiferromagnetic spin- Heisenberg model on a kagome lattice is one
of the most paradigmatic models in the context of spin liquids, yet the precise
nature of its ground state is not understood. We use large scale density matrix
normalization group simulations (DMRG) on infinitely long cylinders and find
indications for the formation of a gapless Dirac spin liquid. First, we use
adiabatic flux insertion to demonstrate that the spin gap is much smaller than
estimated from previous DMRG simulation. Second, we find that the momentum
dependent excitation spectrum, as extracted from the DMRG transfer matrix,
exhibits Dirac cones that match those of a -flux free fermion model (the
parton mean-field ansatz of a Dirac spin liquid)Comment: 15 pages, 16 figure
- …