15,421 research outputs found
Dynamics, Welfare and Migration in Open Economies
In this work we analyze the importance of dynamics in the determination of the distribution of gains from free trade and migration. Given a transition dynamic, free trade might worsen a country relatively to autarchy. Moreover, some individuals might lose welfare during the transition dynamics. In both case, individuals find incentives to migrating, given the lost in the welfare relatively to the autarchy; given the lost in welfare relatively to another country; or, given the intertemporal lost in welfare. Then, inequalities in the distribution of the benefits from free trade matters. Finally, we find out that population size and specialization in production matters in the determination of the distribution of gains from free trade and migration.Migration; free trade; welfare; transition dynamics
Self-consistent 2D models of fast rotating early-type star
This work aims at presenting the first two-dimensional models of an isolated
rapidly rotating star that include the derivation of the differential rotation
and meridional circulation in a self-consistent way.We use spectral methods in
multidomains, together with a Newton algorithm to determine the steady state
solutions including differential rotation and meridional circulation for an
isolated non-magnetic, rapidly rotating early-type star. In particular we
devise an asymptotic method for small Ekman numbers (small viscosities) that
removes the Ekman boundary layer and lifts the degeneracy of the inviscid
baroclinic solutions.For the first time, realistic two-dimensional models of
fast-rotating stars are computed with the actual baroclinic flows that predict
the differential rotation and the meridional circulation for intermediate-mass
and massive stars. These models nicely compare with available data of some
nearby fast-rotating early-type stars like Ras Alhague ( Oph), Regulus
( Leo), and Vega ( Lyr). It is shown that baroclinicity drives
a differential rotation with a slow pole, a fast equator, a fast core, and a
slow envelope. The differential rotation is found to increase with mass, with
evolution (here measured by the hydrogen mass fraction in the core), and with
metallicity. The core-envelope interface is found to be a place of strong shear
where mixing will be efficient.Two-dimensional models offer a new view of
fast-rotating stars, especially of their differential rotation, which turns out
to be strong at the core-envelope interface. They also offer more accurate
models for interpreting the interferometric and spectroscopic data of
early-type stars.Comment: 16 pages, 17 figures, to appear in Astronomy and Astrophysic
What is the upper limit on the lightest supersymmetric Higgs mass?
In this talk the question of what is the upper bound on the lightest
supersymmetric Higgs mass, m_h is addressed. This question is relevant since
experimental lower bounds on m_h might implement, in the near future, exclusion
of supersymmetry. By imposing (perturbative) unification of the gauge couplings
at some high scale \simgt 10^{17} GeV, we have found that for a top-quark mass
M_t=175 GeV, and depending on the supersymmetric parameters, this bound can be
as high as 205 GeV.Comment: 7 pages, 4 figures, Work presented at PASCOS-98, March 22-29 199
First Glimpses at Higgs' face
The 8 TeV LHC Higgs search data just released indicates the existence of a
scalar resonance with mass ~ 125 GeV. We examine the implications of the data
reported by ATLAS, CMS and the Tevatron collaborations on understanding the
properties of this scalar by performing joint fits on its couplings to other
Standard Model particles. We discuss and characterize to what degree this
resonance has the properties of the Standard Model (SM) Higgs, and consider
what implications can be extracted for New Physics in a (mostly)
model-independent fashion. We find that, if the Higgs couplings to fermions and
weak vector bosons are allowed to differ from their standard values, the SM is
~ 2 sigma from the best fit point to current data. Fitting to a possible
invisible decay branching ratio, we find BR_{inv} = 0.05\pm 0.32\ (95% C.L.) We
also discuss and develop some ways of using the data in order to bound or rule
out models which modify significantly the properties of this scalar resonance
and apply these techniques to the global current data set.Comment: 26 pages, 7 figures, v2 post ICHEP data updat
An algorithm for computing the 2D structure of fast rotating stars
Stars may be understood as self-gravitating masses of a compressible fluid
whose radiative cooling is compensated by nuclear reactions or gravitational
contraction. The understanding of their time evolution requires the use of
detailed models that account for a complex microphysics including that of
opacities, equation of state and nuclear reactions. The present stellar models
are essentially one-dimensional, namely spherically symmetric. However, the
interpretation of recent data like the surface abundances of elements or the
distribution of internal rotation have reached the limits of validity of
one-dimensional models because of their very simplified representation of
large-scale fluid flows. In this article, we describe the ESTER code, which is
the first code able to compute in a consistent way a two-dimensional model of a
fast rotating star including its large-scale flows. Compared to classical 1D
stellar evolution codes, many numerical innovations have been introduced to
deal with this complex problem. First, the spectral discretization based on
spherical harmonics and Chebyshev polynomials is used to represent the 2D
axisymmetric fields. A nonlinear mapping maps the spheroidal star and allows a
smooth spectral representation of the fields. The properties of Picard and
Newton iterations for solving the nonlinear partial differential equations of
the problem are discussed. It turns out that the Picard scheme is efficient on
the computation of the simple polytropic stars, but Newton algorithm is
unsurpassed when stellar models include complex microphysics. Finally, we
discuss the numerical efficiency of our solver of Newton iterations. This
linear solver combines the iterative Conjugate Gradient Squared algorithm
together with an LU-factorization serving as a preconditionner of the Jacobian
matrix.Comment: 40 pages, 12 figures, accepted in J. Comput. Physic
- âŠ