1,405 research outputs found
Monetary Policy Rules, Adverse Selection and Long-Run Financial Risk
This paper constructs a macro-finance model with two types of borrowers: entrepreneurs who engage in productive activities and gamblers who play in lotteries. It links a central bank's interest rate policy to expected cash ows of both types of borrowers. Via this link we study how the interactions between various shocks and different monetary policy rules affect the quality of the borrower pool faced by financial intermediaries. We find that if the economy is hit by an expansionary monetary policy shock, in the long run the proportion of entrepreneurs in the borrower pool will be persistently lower than the steady state level. This worsening of the borrower pool is more serious if the central bank does not react to output uctuations. By contrast, not reacting to output uctuations in case of a negative productivity shock avoids a persistent worsening of the borrower pool in the long run.Monetary Policy;Adverse Selection;Financial Crisis
Lattice Boltzmann Models for Complex Fluids
We present various Lattice Boltzmann Models which reproduce the effects of
rough walls, shear thinning and granular flow. We examine the boundary layers
generated by the roughness of the walls. Shear thinning produces plug flow with
a sharp density contrast at the boundaries. Density waves are spontaneously
generated when the viscosity has a nonlinear dependence on density which
characterizes granular flow.Comment: 11 pages, plain TeX, preprint HLRZ 23/9
High performance Beowulf computer for lattice QCD
We describe the construction of a high performance parallel computer composed
of PC components, as well as the performance test in lattice QCD.Comment: Lattice 2001 (Algorithms and Machines) 3 page
qqqbar to qqqbar and qqbarqbar to qqbarqbar Elastic Scatterings and Thermalization of Quark Matter and Antiquark Matter
Thermalization of quark matter and antiquark matter is studied with
quark-quark-antiquark as well as quark-antiquark-antiquark elastic scatterings.
Squared amplitudes of qqqbar to qqqbar and qqbarqbar to qqbarqbar at order
alpha_s^4 are derived in perturbative QCD. Solved by a new technique, solutions
of transport equations with the squared amplitudes indicate that the
scatterings qqqbar to qqqbar and qqbarqbar to qqbarqbar shorten the
thermalization time of quark matter and antiquark matter. It is emphasized that
three-parton and other multi-parton scatterings become important at the high
parton number density achieved in RHIC Au-Au collisions.Comment: 14 pages, 5 figures, Late
Asymmetry of Strange Sea in Nucleons
Based on the finite-temperature field theory, we evaluate the medium effects
in nucleon which can induce an asymmetry between quarks and antiquarks of the
strange sea. The short-distance effects determined by the weak interaction can
give rise to where is the medium-induced mass of strange quark by a few KeV at
most, but the long-distance effects by strong interaction are sizable. Our
numerical results show that there exists an obvious mass difference between
strange and anti-strange quarks, as large as 10-100 MeV.Comment: 15 latex pages, 3 figures, to appear in PR
Theoretical study of incoherent phi photoproduction on a deuteron target
We study the photoproduction of phi mesons in deuteron, paying attention to
the modification of the cross section from bound protons to the free ones with
the aim of comparing with recent results at LEPS. For this purpose we take into
account Fermi motion in single scattering and rescattering of the phi to
account for phi absorption on a second nucleon as well as the rescattering of
the proton. We find that the contribution of the double scattering is much
smaller than the typical cross section of gamma p to phi p in free space, which
implies a very small screening of the phi production in deuteron. The
contribution from the proton rescattering, on the other hand, is found to be
not negligible compared to the cross section of gamma p to phi p in free space,
and leads to a moderate reduction of the phi photoproduction cross section on a
deuteron at forward angles if LEPS set up is taken into account. The Fermi
motion allows contribution of the single scattering in regions forbidden by
phase space in the free case. In particular, we find that for momentum
transferred squared close to the maximum value, the Fermi motion changes
drastically the shape of d sigma / dt, to the point that the ratio of this
cross section to the free one becomes very sensitive to the precise value of t
chosen, or the size of the bin used in an experimental analysis. Hence, this
particular region of t does not seem the most indicated to find effects of a
possible phi absorption in the deuteron. This reaction is studied theoretically
as a function of t and the effect of the experimental angular cuts at LEPS is
also discussed, providing guidelines for future experimental analyses of the
reaction.Comment: 17 pages, 16 figure
Ab-initio study of BaTiO3 surfaces
We have carried out first-principles total-energy calculations of (001)
surfaces of the tetragonal and cubic phases of BaTiO3. Both BaO-terminated
(type I) and TiO2-terminated (type II) surfaces are considered, and the atomic
configurations have been fully relaxed. We found no deep-gap surface states for
any of the surfaces, in agreement with previous theoretical studies. However,
the gap is reduced for the type-II surface, especially in the cubic phase. The
surface relaxation energies are found to be substantial, i.e., many times
larger than the bulk ferroelectric well depth. Nevertheless, the influence of
the surface upon the ferroelectric order parameter is modest; we find only a
small enhancement of the ferroelectricity near the surface.Comment: 8 pages, two-column style with 4 postscript figures embedded. Uses
REVTEX and epsf macros. Also available at
http://www.physics.rutgers.edu/~dhv/preprints/index.html#pad_sur
Theoretical study of the (3x2) reconstruction of beta-SiC(001)
By means of ab initio molecular dynamics and band structure calculations, as
well as using calculated STM images, we have singled out one structural model
for the (3x2) reconstruction of the Si-terminated (001) surface of cubic SiC,
amongst several proposed in the literature. This is an alternate dimer-row
model, with an excess Si coverage of 1/3, yielding STM images in good accord
with recent measurements [F.Semond et al. Phys. Rev. Lett. 77, 2013 (1996)].Comment: To be published in PRB Rapid. Com
First-principles study of the polar O-terminated ZnO surface in thermodynamic equilibrium with oxygen and hydrogen
Using density-functional theory in combination with a thermodynamic formalism
we calculate the relative stability of various structural models of the polar
O-terminated (000-1)-O surface of ZnO. Model surfaces with different
concentrations of oxygen vacancies and hydrogen adatoms are considered.
Assuming that the surfaces are in thermodynamic equilibrium with an O2 and H2
gas phase we determine a phase diagram of the lowest-energy surface structures.
For a wide range of temperatures and pressures we find that hydrogen will be
adsorbed at the surface, preferentially with a coverage of 1/2 monolayer. At
high temperatures and low pressures the hydrogen can be removed and a structure
with 1/4 of the surface oxygen atoms missing becomes the most stable one. The
clean, defect-free surface can only exist in an oxygen-rich environment with a
very low hydrogen partial pressure. However, since we find that the
dissociative adsorption of molecular hydrogen and water (if also the
Zn-terminated surface is present) is energetically very preferable, it is very
unlikely that a clean, defect-free (000-1)-O surface can be observed in
experiment.Comment: 10 pages, 4 postscript figures. Uses REVTEX and epsf macro
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