4,779 research outputs found
Estimation of Precautionary Demand by Financial Anxieties
Pioneering work of modelling financial anxieties was given by Kimura et al (1999) as psychological change of people due to financial shocks. Since they regressed financial position (easy or tight) by nonstationary interest rate, their results exhibit high peaks not only in financial crisis period of 1997 and 1998, but also in the bubble economy period of 1987 to 1989, which seems to be a spurious regression. Furthermore, defining financial anxieties as the conditional variance in TARCH model, one of estimated coefficients did not satisfy sign condition. We got rid of these difficulties by introducing a growth rate model, where a change of financial position (toward ''tight'') under a change of interest rate (toward ''fall'') is regarded as financial anxieties. Such anxieties are quantified by conditional variance of EGARCH model and shown to be stationary. Precautionary demand caused by financial anxieties is estimated in VEC model and it is shown that money adjusted by precautionary demand satisfies a long-run equilibrium relationship in the system (adjusted money, real GDP, interest rate) even in the interval 1980q1 to 2003q2.financial anxieties, precautionary demand, cointegration, EGARCH
The Juelich hyperon-nucleon model revisited
A one-boson-exchange model for the hyperon-nucleon (\Lambda N, \Sigma N)
interaction is presented. The model incorporates the standard one boson
exchanges of the lowest pseudoscalar and vector meson multiplets with coupling
constants fixed by SU(6) flavor symmetry relations. As the main new feature of
the model, the contributions in the scalar--isoscalar (\sigma) and
vector--isovector (\rho) exchange channels are now constrained by a microscopic
model of correlated \pi\pi and K \bar K exchange. Additional short-ranged
ingredients of the model in the scalar--isovector (a_0) and scalar--isospin-1/2
(\kappa) channels are likewise viewed as arising from meson-meson correlations
but are treated phenomenologically. With this model a satisfactory reproduction
of the available hyperon-nucleon data can be achieved.Comment: 24 pages, 13 figures, some modifications to text, several references
added, some figures corrected, to appear in Phys. Rev.
The nonmesonic weak decay of the hypertriton
The nonmesonic decay of the hypertriton is calculated based on a hypertriton
wavefunction and 3N scattering states, which are rigorous solutions of 3-body
Faddeev equations using realistic NN and hyperon-nucleon interactions. The
pion-exchange together with heavier meson exchanges for the transition is considered. The total nonmesonic decay rate is found to be 0.5%
of the free decay rate. Integrated as well as differential decay
rates are given. The p- and n- induced decays are discussed thoroughly and it
is shown that the corresponding total rates cannot be measured individually.Comment: 27 pages, 20 figures, revtex, submitted to Phys. Rev.
Transport criticality of the first-order Mott transition in a quasi-two-dimensional organic conductor, -(BEDT-TTF)Cu[N(CN)]Cl
An organic Mott insulator, -(BEDT-TTF)Cu[N(CN)]Cl, was
investigated by resistance measurements under continuously controllable He gas
pressure. The first-order Mott transition was demonstrated by observation of
clear jump in the resistance variation against pressure. Its critical endpoint
at 38 K is featured by vanishing of the resistive jump and critical divergence
in pressure derivative of resistance, , which are consistent with the prediction of the dynamical mean field
theory and have phenomenological correspondence with the liquid-gas transition.
The present results provide the experimental basis for physics of the Mott
transition criticality.Comment: 4 pages, 5 figure
Lambda-N scattering length from the reaction gamma d -> K^+ Lambda n
The perspects of utilizing the strangeness-production reaction gamma d -> K^+
Lambda n for the determination of the Lambda n low-energy scattering parameters
are investigated. The spin observables that need to be measured in order to
isolate the Lambda n singlet (1S0) and triplet (3S1) states are identified.
Possible kinematical regions where the extraction of the Lambda n scattering
lengths might be feasible are discussed.Comment: 8 pages, 4 figure
Antiferromagnetic Spin Fluctuations in the Metallic Phase of Quasi-Two-Dimensional Organic Superconductors
We give a quantitative analysis of the previously published nuclear magnetic
resonance (NMR) experiments in the k-(ET)2X family of organic charge transfer
salts by using the phenomenological spin fluctuation model of Moriya, and
Millis, Monien and Pines (M-MMP). For temperatures above T_nmr ~ 50 K, the
model gives a good quantitative description of the data in the metallic phases
of several k-(ET)2X materials. These materials display antiferromagnetic
correlation lengths which increase with decreasing temperature and grow to
several lattice constants by T_nmr. It is shown that the fact that the
dimensionless Korringa ratio is much larger than unity is inconsistent with a
broad class of theoretical models (such as dynamical mean-field theory) which
neglects spatial correlations and/or vertex corrections. For materials close to
the Mott insulating phase the nuclear spin relaxation rate, the Knight shift
and the Korringa ratio all decrease significantly with decreasing temperature
below T_nmr. This cannot be described by the M-MMP model and the most natural
explanation is that a pseudogap, similar to that observed in the underdoped
cuprate superconductors, opens up in the density of states below T_nmr. Such a
pseudogap has recently been predicted to occur in the dimerised organic charge
transfer salts materials by the resonating valence bond (RVB) theory. We
propose specific new experiments on organic superconductors to elucidate these
issues. For example, measurements to see if high magnetic fields or high
pressures can be used to close the pseudogap would be extremely valuable.Comment: 11 pages, 2 figures. Accepted for publication in Phys. Rev.
Superconductor-Insulator Phase Separation Induced by Rapid Cooling in kappa-(ET)_2Cu[N(CN)_2]Br
We present measurements of the low temperature specific heat of single
crystals of kappa-(ET)_2Cu[N(CN)_2]Br as a function of the cooling rate through
the glasslike structure transition at 80K. We find that rapid cooling
produces a small (< 4%) decrease in the superconducting transition temperature
accompanied by a substantial (up to 50%) decrease in the normal-state
electronic specific heat. A natural explanation of our data is that there is a
macroscopic phase separation between superconducting and insulating regions in
rapidly cooled samples.Comment: 4 pages, to appear in Phys. Rev. B (Rapid Comm
Resonant inelastic x-ray scattering probes the electron-phonon coupling in the spin-liquid kappa-(BEDT-TTF)2Cu2(CN)3
Resonant inelastic x-ray scattering at the N K edge reveals clearly resolved
harmonics of the anion plane vibrations in the kappa-(BEDT-TTF)2Cu2(CN)3
spin-liquid insulator. Tuning the incoming light energy at the K edge of two
distinct N sites permits to excite different sets of phonon modes. Cyanide CN
stretching mode is selected at the edge of the ordered N sites which are more
strongly connected to the BEDT-TTF molecules, while positionally disordered N
sites show multi-mode excitation. Combining measurements with calculations on
an anion plane cluster permits to estimate the sitedependent electron-phonon
coupling of the modes related to nitrogen excitation
Inclusive and exclusive photoproduction on the deuteron: - and -threshold phenomena
Inclusive and exclusive photoproduction on the deuteron are
investigated theoretically. Modern hyperon-nucleon forces and a recently
updated kaon photoproduction operator for the process are
used. Sizable effects of the hyperon-nucleon final state interaction are found
near the and thresholds in the inclusive reaction.
Angular distributions for the exclusive process show clear final state
interaction effects in certain kinematic regions. Precise data especially for
the inclusive process around the threshold would help to clarify
the strength and property of the interaction.Comment: 14 pages, 10 figure
Precise calculation of the two-step process for K- d -> pi Sigma N in the Lambda (1405) resonance region
The reaction K- d -> pi Sigma N is investigated taking into account single
scattering and the two-step process due to Kbar N -> pi Sigma rescattering. The
influence of some common approximations are examined. It is found that the
treatment of the kinematics in the Green's function that appears in the loop
integral of the rescattering process has a rather strong impact on the
resulting lineshape of the pi Sigma invariant mass spectrum. Specifically, a
calculation with correct kinematics where the three-body unitarity cut due to
the nK- p threshold occurs at the physical value yields a pronounced peak in
the invariant mass spectrum at this threshold and, at the same time, suppresses
the signal in the region of the Lambda(1405) resonance. On the other hand, an
approximation applied in past calculations shifts that threshold down and,
consequently, leads to an accidental and therefore erroneous enhancement of the
signal of the Lambda(1405) in the pi Sigma invariant mass spectrum.Comment: 11 pages, 13 figure
- …