8,410 research outputs found
The role of rotation on Petersen Diagrams. II The influence of near-degeneracy
In the present work, the effect of near-degeneracy on rotational Petersen
diagrams (RPD) is analysed. Seismic models are computed considering rotation
effects on both equilibrium models and adiabatic oscillation frequencies
(including second-order near-degeneracy effects). Contamination of coupled
modes and coupling strength on the first radial modes are studied in detail.
Analysis of relative intrinsic amplitudes of near-degenerate modes reveals that
the identity of the fundamental radial mode and its coupled quadrupole pair are
almost unaltered once near-degeneracy effects are considered. However, for the
first overtone, a mixed radial/quadrupole identity is always predicted. The
effect of near-degeneracy on the oscillation frequencies becomes critical for
rotational velocities larger than 15-20 km/s, for which large wriggles in the
evolution of the period ratios are obtained (up ). Such wriggles imply
uncertainties, in terms of metallicity determinations using RPD, reaching up to
0.50 dex, which can be critical for Pop. I HADS (High Amplitude \dss). In terms
of mass determinations, uncertainties reaching up to 0.5 M_sun are predicted.
The location of such wriggles is found to be independent of metallicity and
rotational velocity, and governed mainly by the avoided-crossing phenomenon.Comment: 8 pages, 7 figures, 1 table. (accepted for publication in A&A
FILOU oscillation code
The present paper provides a description of the oscillation code FILOU, its
main features, type of applications it can be used for, and some representative
solutions. The code is actively involved in CoRoT/ESTA exercises (this volume)
for the preparation for the proper interpretation of space data from the CoRoT
mission. Although CoRoT/ESTA exercises have been limited to the oscillations
computations for non-rotating models, the main characteristic of FILOU is,
however, the computation of radial and non-radial oscillation frequencies in
presence of rotation. In particular, FILOU calculates (in a perturbative
approach) adiabatic oscillation frequencies corrected for the effects of
rotation (up to the second order in the rotation rate) including near
degeneracy effects. Furthermore, FILOU works with either a uniform rotation or
a radial differential rotation profile (shellular rotation), feature which
makes the code singular in the field.Comment: 6 pages, 5 figures. Astrophysics and Space Science (in press
Building Stability in Latin American Financial Markets
This paper argues that the investor reluctance to make long-term commitments to Latin American financial markets results from experience. In the 1980s, while ex ante real interest rates on Latin American financial assets were usually high, ex-post real interest rates were often highly negative. In the 1990s, policymakers instituted stabilization programs and structural reforms that have improved the environment in which financial markets operate. Based on a review of experiences in the region, this paper shows that, when these opportunities are taken, investor confidence in long-term markets is strengthened.
Inconsistencies in the application of harmonic analysis to pulsating stars
Using ultra-precise data from space instrumentation we found that the
underlying functions of stellar light curves from some AF pul- sating stars are
non-analytic, and consequently their Fourier expansion is not guaranteed. This
result demonstrates that periodograms do not provide a mathematically
consistent estimator of the frequency content for this kind of variable stars.
More importantly, this constitutes the first counterexample against the current
paradigm which considers that any physical process is described by a contin-
uous (band-limited) function that is infinitely differentiable.Comment: 9 pages, 8 figure
Towards an Effective Regulatory and Supervisory Framework for Latin America
This paper raises fundamental questions about how banks in Latin America ought to be supervised. The concentration of wealth holders in Latin America and the equity markets` resulting illiquidity permit investors who control banks to subvert the intent of capital requirements, even when the bank itself is subject to rigorous accounting standards. A number of policy implications follow from the analysis. Three of policy recommendations derived from this analysis can be successfully implemented in the short run. Latin American supervisors should focus on: improving the markets that already work in Latin America, which currently are markets for bank liabilities; severely limiting public safety nets for bank liabilities so that risky banks face a high price for raising liabilities; and encouraging macroeconomic policies to play a much more important role in restraining bank risk in Latin America than in the industrial countries.
Impact of Fano and Breit-Wigner resonances in the thermoelectric properties of nanoscale junctions
We show that the thermoelectric properties of nanoscale junctions featuring
states near the Fermi level strongly depend on the type of resonance generated
by such states, which can be either Fano or Breit-Wigner-like. We give general
expressions for the thermoelectric coefficients generated by the two types of
resonances and calculate the thermoelectric properties of these systems, which
encompass most nanoelectronics junctions. We include simulations of real
junctions where metalloporphyrin molecules bridge gold electrodes and prove
that for some metallic elements the thermoelectric properties show a large
variability. We find that the thermopower and figure of merit are largely
enhanced when the resonance gets close to the Fermi level and reach values much
higher than typical values found in other nanoscale junctions. The specific
value and temperature dependence are determined by a series of factors such as
the strength of the coupling between the state and other molecular states, the
symmetry of the state, the strength of the coupling between the molecule and
the leads and the spin filtering behavior of the junction.Comment: 9 pages, 11 figure
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