34,872 research outputs found
CROSS-SECTIONAL ESTIMATION OF U.S. DEMAND FOR BEEF PRODUCTS: A CENSORED SYSTEM APPROACH
Demands for beef products are investigated using the U.S. Department of AgricultureÂ’'s 1987-88 Nationwide Food Consumption Survey data. The censored translog demand system is estimated with full-information and simulated maximum-likelihood procedures. These procedures represent different approaches to evaluation of multiple probability integrals in the likelihood function, but produce very similar parameter and elasticity estimates. Findings suggest sociodemographic variables play important roles in the demand for beef, and that demand for different cuts of beef should be treated differently.Demand and Price Analysis,
HOUSEHOLD DEMAND FOR FINFISH: A GENERALIZED DOUBLE-HURDLE MODEL
This study estimates household demand for finfish in the United States using a limited dependent variable model that accounts for both participation and consumption decisions and also accommodates nonnormal heteroskedastic errors. Results suggest that own-price elasticity is near unitary and income elasticity is small. Price of finfish, shopping frequency, Northeast, Black and other non-Whites, and the life-cycle variable “"young, single, no children”" are they key factors that affect significantly both the probability of participation and the level of finfish consumption. Furthermore, a variable may exert opposite effects on the probability and level of consumption.Consumer/Household Economics, Demand and Price Analysis,
ESTIMATION OF A DEMAND SYSTEM WITH LIMITED DEPENDENT VARIABLES
The study employs the full-information maximum-likelihood method to estimate a censored translog demand system. U.S. household consumption of steak, roast, and ground beef are used to demonstrate the application of the estimation procedure. The proposed methodology produces more efficient estimates than the popular two-step procedures found in demand literature.Demand and Price Analysis,
Tunnelling current and emission spectrum of a single electron transistor under optical pumping
Theoretical studies of the tunnelling current and emission spectrum of a
single electron transistor (SET) under optical pumping are presented. The
calculation is performed via Keldysh Green's function method within the
Anderson model with two energy levels. It is found that holes in the quantum
dot (QD) created by optical pumping lead to new channels for the electron
tunnelling from emitter to collector. As a consequence, an electron can tunnel
through the QD via additional channels, characterized by the exciton, trion and
biexciton states. It is found that the tunnelling current as a function of the
gate voltage displays a series of sharp peaks and the spacing between these
peaks can be used to determine the exciton binding energy as well as the
electron-electron Coulomb repulsion energy. In addition, we show that the
single-photon emission associated with the electron-hole recombination in the
exciton complexes formed in the QD can be controlled both electrically and
optically.Comment: 24 pages, 10 figure
Quantum criticality in Kondo quantum dot coupled to helical edge states of interacting 2D topological insulators
We investigate theoretically the quantum phase transition (QPT) between the
one-channel Kondo (1CK) and two-channel Kondo (2CK) fixed points in a quantum
dot coupled to helical edge states of interacting 2D topological insulators
(2DTI) with Luttinger parameter . The model has been studied in Ref. 21,
and was mapped onto an anisotropic two-channel Kondo model via bosonization.
For K<1, the strong coupling 2CK fixed point was argued to be stable for
infinitesimally weak tunnelings between dot and the 2DTI based on a simple
scaling dimensional analysis[21]. We re-examine this model beyond the bare
scaling dimension analysis via a 1-loop renormalization group (RG) approach
combined with bosonization and re-fermionization techniques near weak-coupling
and strong-coupling (2CK) fixed points. We find for K -->1 that the 2CK fixed
point can be unstable towards the 1CK fixed point and the system may undergo a
quantum phase transition between 1CK and 2CK fixed points. The QPT in our model
comes as a result of the combined Kondo and the helical Luttinger physics in
2DTI, and it serves as the first example of the 1CK-2CK QPT that is accessible
by the controlled RG approach. We extract quantum critical and crossover
behaviors from various thermodynamical quantities near the transition. Our
results are robust against particle-hole asymmetry for 1/2<K<1.Comment: 17 pages, 9 figures, more details added, typos corrected, revised
Sec. IV, V, Appendix A and
Quintessential Kination and Leptogenesis
Thermal leptogenesis induced by the CP-violating decay of a right-handed
neutrino (RHN) is discussed in the background of quintessential kination, i.e.,
in a cosmological model where the energy density of the early Universe is
assumed to be dominated by the kinetic term of a quintessence field during some
epoch of its evolution. This assumption may lead to very different
observational consequences compared to the case of a standard cosmology where
the energy density of the Universe is dominated by radiation. We show that,
depending on the choice of the temperature T_r above which kination dominates
over radiation, any situation between the strong and the super--weak wash--out
regime are equally viable for leptogenesis, even with the RHN Yukawa coupling
fixed to provide the observed atmospheric neutrino mass scale ~ 0.05 eV. For M<
T_r < M/100, i.e., when kination stops to dominate at a time which is not much
later than when leptogenesis takes place, the efficiency of the process,
defined as the ratio between the produced lepton asymmetry and the amount of CP
violation in the RHN decay, can be larger than in the standard scenario of
radiation domination. This possibility is limited to the case when the neutrino
mass scale is larger than about 0.01 eV. The super--weak wash--out regime is
obtained for T_r << M/100, and includes the case when T_r is close to the
nucleosynthesis temperature ~ 1 MeV. Irrespective of T_r, we always find a
sufficient window above the electroweak temperature T ~ 100 GeV for the
sphaleron transition to thermalize, so that the lepton asymmetry can always be
converted to the observed baryon asymmetry.Comment: 13 pages, 8 figure
Dynamics of composite Haldane spin chains in IPA-CuCl3
Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl3
are studied by cold neutron inelastic scattering. Strongly dispersive gap
excitations are observed. Contrary to previously proposed models, the system is
best described as an asymmetric quantum spin ladder. The observed spectrum is
interpreted in terms of ``composite'' Haldane spin chains. The key difference
from actual S=1 chains is a sharp cutoff of the single-magnon spectrum at a
certain critical wave vector.Comment: 4 pages 4 figure
Partially composite 2-Higgs-doublet model
In the extra dimensional scenarios with gauge fields in the bulk, the
Kaluza-Klein (KK) gauge bosons can induce Nambu-Jona-Lasinio (NJL) type
attractive four-fermion interactions, which can break electroweak symmetry
dynamically with accompanying composite Higgs fields. We consider a possibility
that electroweak symmetry breaking (EWSB) is triggered by both a fundamental
Higgs and a composite Higgs arising in a dynamical symmetry breaking mechanism
induced by a new strong dynamics. The resulting Higgs sector is a partially
composite two-Higgs doublet model with specific boundary conditions on the
coupling and mass parameters originating at a compositeness scale .
The phenomenology of this model is discussed including the collider
phenomenology at LHC and ILC.Comment: To appear in the proceeding of LCWS06, Bangalore, Indi
Nagy-Soper subtraction scheme for multiparton final states
In this work, we present the extension of an alternative subtraction scheme
for next-to-leading order QCD calculations to the case of an arbitrary number
of massless final-state partons. The scheme is based on the splitting kernels
of an improved parton shower and comes with a reduced number of final state
momentum mappings. While a previous publication including the setup of the
scheme has been restricted to cases with maximally two massless partons in the
final state, we here provide the final state real emission and integrated
subtraction terms for processes with any number of massless partons. We apply
our scheme to three jet production at lepton colliders at next-to-leading order
and present results for the differential C parameter distribution.Comment: 45 pages, 5 figures v2: several references added; v3: title changed,
references and a discussion of further scaling improvement added. Corresponds
to published journal versio
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