7,276 research outputs found
Revisiting the determinacy on New Keynesian Models
The goal of this paper is to shed light on the determinacy question that
arises in New Keynesian models as result of a combination of several monetary
policy rules; in these models, we provide conditions to guarantee existence and
uniqueness of equilibrium by means of results that are obtained from
theoretical analysis. In particular, we show that Taylor--like rules in
interest rate setting are not the only way to reach determinacy of the rational
expectations equilibrium in the New Keynesian setting. The key technical tool
that we use for that purposes is the so--called Budan--Fourier Theorem, that we
review along the paper.Comment: 16 pages, comments are welcom
Dynamical zeros in neutrino-electron elastic scattering at leading order
We show the existence of dynamical zeros in the helicity amplitudes for
neutrino-electron elastic scattering at lowest order in the standard theory. In
particular, the non-flip electron helicity amplitude in the
electron antineutrino process vanishes for an incident neutrino energy
and forward electrons (maximum recoil
energy). The rest of helicity amplitudes show kinematical zeros in this
configuration and therefore the cross section vanishes. Prospects to search for
neutrino magnetic moment are discussed.Comment: 9 pg.+ 2 figures (not included available upon request
A Novel Kind of Neutrino Oscillation Experiment
A novel method to look for neutrino oscillations is proposed based on the
elastic scattering process , taking advantage of the dynamical zero present in the differential
cross section for . An
effective tunable experiment between the "appearance" and "disappearance"
limits is made possible. Prospects to exclude the allowed region for
atmospheric neutrino oscillations are given.Comment: 11 pages (+3 figures, available upon request),Standard Latex,
FTUV/94-3
The State of the Circumstellar Medium Surrounding Gamma-Ray Burst Sources and its Effect on the Afterglow Appearance
We present a numerical investigation of the contribution of the presupernova
ejecta of Wolf-Rayet stars to the environment surrounding gamma-ray bursts
(GRBs), and describe how this external matter can affect the observable
afterglow characteristics. An implicit hydrodynamic calculation for massive
stellar evolution is used here to provide the inner boundary conditions for an
explicit hydrodynamical code to model the circumstellar gas dynamics. The
resulting properties of the circumstellar medium are then used to calculate the
deceleration of a relativistic, gas-dynamic jet and the corresponding afterglow
light curve produced as the shock wave propagates through the shocked-wind
medium. We find that variations in the stellar wind drive instabilities that
may produce radial filaments in the shocked-wind region. These comet-like tails
of clumps could give rise to strong temporal variations in the early afterglow
lightcurve. Afterglows may be expected to differ widely among themselves,
depending on the angular anisotropy of the jet and the properties of the
stellar progenitor; a wide diversity of behaviors may be the rule, rather than
the exception.Comment: 17 pages, 7 figures, ApJ in pres
Investigation of acceptor levels and hole scattering mechanisms in p-gallium selenide by means of transport measurements under pressure
The effect of pressure on acceptor levels and hole scattering mechanisms in
p-GaSe is investigated through Hall effect and resistivity measurements under
quasi-hydrostatic conditions up to 4 GPa. The pressure dependence of the hole
concentration is interpreted through a carrier statistics equation with a
single (nitrogen) or double (tin) acceptor whose ionization energies decrease
under pressure due to the dielectric constant increase. The pressure effect on
the hole mobility is also accounted for by considering the pressure
dependencies of both the phonon frequencies and the hole-phonon coupling
constants involved in the scattering rates.Comment: 13 pages, Latex, 4 ps figures. to appear in High Pressure Research 69
(1997
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