7,061 research outputs found
Shortcuts to Adiabaticity Assisted by Counterdiabatic Born-Oppenheimer Dynamics
Shortcuts to adiabaticity (STA) provide control protocols to guide the
dynamics of a quantum system through an adiabatic reference trajectory in an
arbitrary prescheduled time. Designing STA proves challenging in complex
quantum systems when the dynamics of the degrees of freedom span different time
scales. We introduce Counterdiabatic Born-Oppenheimer Dynamics (CBOD) as a
framework to design STA in systems with a large separation of energy scales.
CBOD exploits the Born-Oppenheimer approximation to separate the Hamiltonian
into effective fast and slow degrees of freedom and calculate the corresponding
counterdiabatic drivings for each subsystem. We show the validity of the CBOD
technique via an example of coupled harmonic oscillators, which can be solved
exactly for comparison, and further apply it to a system of two-charged
particles.Comment: 14 pages, 3 figures, published New Journal of Physic
Dairy Food Consumption, Production, and Policy in Japan
We explore and investigate Japanese dairy markets. We first provide an overview of consumer demand and how it evolved after World War II. Using historical data and econometric estimates of Japanese dairy demand, we identify economic, cultural, and demographic forces that have been shaping consumption patterns. Then we summarize the characteristics of Japanese milk production and dairy processing and policies affecting them. We next describe the import regime and trade flows in dairy products. The analysis of the regulatory system of the dairy sector shows how its incentive structure affects the long-term prospects of various segments of the industry. The paper concludes with policy recommendations of how to reform the Japanese dairy sector.
Japanese Consumer Demand for Dairy Products
We econometrically estimate consumer demand for dairy products in Japan using time series data for 1960-2003. We identify economic, cultural, and demographic forces that have been influencing dairy consumption patterns. We use the Almost Ideal (AI) Demand System by Deaton and Muellbauer and its variant, the Semiflexible Almost Ideal (SAI) Demand System developed by Moschini to impose concavity locally by reducing the rank of the Hessian of the expenditure function. We estimate three specifications: a full system comprising of four dairy products (fluid milk, powder milk, cheese, and butter), and an allother-goods aggregate; a subsystem for food made of four dairy goods and an all-other-food aggregate; and a sub-system of the four dairy products. The minimum distance estimator is used to estimate the demand system. We find that expenditure responses are positive, except for butter demand; own-price responses are large in absolute value; and non-price factors are important determinants of Japanese dairy consumption.dairy demand, Japan, demand system, cheese, fluid milk, Demand and Price Analysis, Livestock Production/Industries, Q11, Q17, Q18,
Non Singular Origin of the Universe and its Present Vacuum Energy Density
We consider a non singular origin for the Universe starting from an Einstein
static Universe, the so called "emergent universe" scenario, in the framework
of a theory which uses two volume elements and , where is a metric independent density, used as an additional
measure of integration. Also curvature, curvature square terms and for scale
invariance a dilaton field are considered in the action. The first order
formalism is applied. The integration of the equations of motion associated
with the new measure gives rise to the spontaneous symmetry breaking (S.S.B) of
scale invariance (S.I.). After S.S.B. of S.I., it is found that a non trivial
potential for the dilaton is generated. In the Einstein frame we also add a
cosmological term that parametrizes the zero point fluctuations. The resulting
effective potential for the dilaton contains two flat regions, for relevant for the non singular origin of the Universe,
followed by an inflationary phase and , describing
our present Universe. The dynamics of the scalar field becomes non linear and
these non linearities are instrumental in the stability of some of the emergent
universe solutions, which exists for a parameter range of values of the vacuum
energy in , which must be positive but not very big,
avoiding the extreme fine tuning required to keep the vacuum energy density of
the present universe small. Zero vacuum energy density for the present universe
defines the threshold for the creation of the universe.Comment: 28 pages, short version of this paper awarded an honorable mention by
the Gravity Research Foundation, 2011, accepted for publication in
International Journal of Modern Physics
Is the cosmological dark sector better modeled by a generalized Chaplygin gas or by a scalar field?
Both scalar fields and (generalized) Chaplygin gases have been widely used
separately to characterize the dark sector of the Universe. Here we investigate
the cosmological background dynamics for a mixture of both these components and
quantify the fractional abundances that are admitted by observational data from
supernovae of type Ia and from the evolution of the Hubble rate. Moreover, we
study how the growth rate of (baryonic) matter perturbations is affected by the
dark-sector perturbations.Comment: 20 pages, 9 figures, substantially revised, section on matter
perturbations added, accepted for publication in EPJ
Cosmology with Ricci-type dark energy
We consider the dynamics of a cosmological substratum of pressureless matter
and holographic dark energy with a cutoff length proportional to the Ricci
scale. Stability requirements for the matter perturbations are shown to single
out a model with a fixed relation between the present matter fraction
and the present value of the equation-of-state
parameter of the dark energy. This model has the same number of free parameters
as the CDM model but it has no CDM limit. We discuss the
consistency between background observations and the mentioned
stability-guaranteeing parameter combination.Comment: 6 pages, 3 figures, submitted to the Proceedings of the CosmoSurII
conference, Valpara\'iso, Chile, 27 - 31 May 201
Raman transitions between hyperfine clock states in a magnetic trap
We present our experimental investigation of an optical Raman transition
between the magnetic clock states of Rb in an atom chip magnetic trap.
The transfer of atomic population is induced by a pair of diode lasers which
couple the two clock states off-resonantly to an intermediate state manifold.
This transition is subject to destructive interference of two excitation paths,
which leads to a reduction of the effective two-photon Rabi-frequency.
Furthermore, we find that the transition frequency is highly sensitive to the
intensity ratio of the diode lasers. Our results are well described in terms of
light shifts in the multi-level structure of Rb. The differential light
shifts vanish at an optimal intensity ratio, which we observe as a narrowing of
the transition linewidth. We also observe the temporal dynamics of the
population transfer and find good agreement with a model based on the system's
master equation and a Gaussian laser beam profile. Finally, we identify several
sources of decoherence in our system, and discuss possible improvements.Comment: 10 pages, 7 figure
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