2,183 research outputs found
Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions
The magneto-electrostatic tailoring of the supercurrent in quantum point
contact ballistic Josephson junctions is demonstrated. An etched InAs-based
heterostructure is laterally contacted to superconducting niobium leads and the
existence of two etched side gates permits, in combination with the application
of a perpendicular magnetic field, to modify continuously the magnetic
interference pattern by depleting the weak link. For wider junctions the
supercurrent presents a Fraunhofer-like interference pattern with periodicity
h/2e whereas by shrinking electrostatically the weak link, the periodicity
evolves continuously to a monotonic decay. These devices represent novel
tunable structures that might lead to the study of the elusive Majorana
fermions.Comment: 4.5 pages, 4 color figure
Freedom and Complicity: The Case of Horison and Solidarity, two Congress for Cultural Freedom Journals in Southeast Asia
The current project is a two-pronged study of Horison (Indonesia) and Solidarity (Philippines), two journals funded by the Congress for Cultural Freedom (CCF) during the Cold War in its quest to mount a cultural offensive against the rising threat of communism in Southeast Asia. The first part of the project deals with what Ang Cheng Guan sees as the case of the Cold War ceasing to be an actual historical event and, in turn, transforming into an “object” of historical inquiry (1–17). To this end, the article will provide a short account of both journals’ genesis and history during the Cold War’s peak in the region. Through the use of computer-aided methods, the second part will attempt a “closer” reading of selected editorials from 1966 to 1976 in order to shed light on specific discursive-ideological aspects (i.e., anti-communist intimations) evinced by both journals and their progenitors
Growth cycles in Latin America and developed countries
The Minskyan approach to financial instability and its effects on the real economy have recently been revived in order to explain the exchange rate crises undergone by the so-called emergent economies. Economies of this type are characterized by repeated scarcity of foreign currency, which can be explained by using Neo-Schumpeterian theory. Based on the Minskyan approach and on the Neo-Schumpeterian literature, this study seeks to demonstrate that there is a cyclic recurrence of exchange rate crises in Latin-American (peripheral) economies. By using data on international liquidity, the balance of payments and the increase in production in the G7 economies and in thirteen Latin-American economies, it was found that the Latin-American economies mirror the cycles of international liquidity.financial instability, national innovation system, cycles
Circularly Polarized Resonant Rayleigh Scattering and Skyrmions in the = 1 Quantum Hall Ferromagnet
We use the circularly polarized resonant Rayleigh scattering (RRS) to study
the quantum Hall ferromagnet at = 1. At this filling factor we observe a
right handed copolarized RRS which probes the Skyrmion spin texture of the
electrons in the photoexcited grounds state. The resonant scattering is not
present in the left handed copolarization, and this can be related to the
correlation between Skymionic effects, screening and spin wave excitations.
These results evidence that RRS is a valid method for the study of the spin
texture of the quantum Hall states
An attractive nucleon-nucleon spin-orbit force from skyrmions with dilatons
Within the skyrmion approach for the nucleon-nucleon force, difficulties have
been experienced in obtaining an isoscalar attractive spin-orbit potential, in
parallel to the problems of finding attraction in the isoscalar central
potential. We here study the spin-orbit force using a skyrmion with four- and
six-derivative stabilizing terms in the lagrangian as well as with the crucial
addition of a dilaton. With these features present the spin-orbit force proves
to be attractive as does the central potential. In the absence of the dilaton,
attraction can also be found for the spin-orbit potential but only at the
expense of a greatly over-emphasized term with six derivatives and a continuing
absence of attraction in the central potential.Comment: 8 pages plus 5 figures in uuencoded tar-compressed for
A study of local approximation for polarization potentials
We discuss the derivation of an equivalent \textit{l}-independent
polarization potential for use in the optical Schr\"{o}dinger equation that
describes the elastic scattering of heavy ions. Three diffferent methods are
used for this purpose. Application of our theory to the low energy scattering
of the halo nucleus Li from a C target is made. It is found that
the notion of \textit{l}-independent polarization potential has some validity
but can not be a good substitute for the \textit{l}-dependent local equivalent
Feshbach polarization potential.Comment: 8 pages, 4 figure
High-cadence spectroscopy of M-dwarfs – II. Searching for stellar pulsations with HARPS
Stellar oscillations appear all across the Hertzsprung–Russell diagram. Recent theoretical studies support their existence also in the atmosphere of M dwarfs. These studies predict for them short periodicities ranging from 20 min to 3 h. Our Cool Tiny Beats (CTB) programme aims at finding these oscillations for the very first time. With this goal, CTB explores the short time domain of M dwarfs using radial velocity data from the High Accuracy Radial velocity Planet Searcher (HARPS)-European Southern Observatory and HARPS-N high-precision spectrographs. Here we present the results for the two most long-term stable targets observed to date with CTB, GJ 588 and GJ 699 (i.e. Barnard's star). In the first part of this work we detail the correction of several instrumental effects. These corrections are especially relevant when searching for subnight signals. Results show no significant signals in the range where M dwarfs pulsations were predicted. However, we estimate that stellar pulsations with amplitudes larger than ∼0.5 m s−1 can be detected with a 90 per cent completeness with our observations. This result, along with the excess of power regions detected in the periodograms, opens the possibility of non-resolved very low amplitude pulsation signals. Next generation more precise instrumentation would be required to detect such oscillations. However, the possibility of detecting pulsating M-dwarf stars with larger amplitudes is feasible due to the short size of the analysed sample. This motivates the need for completeness of the CTB survey
Algebraic-eikonal approach to medium energy proton scattering from odd-mass nuclei
We extend the algebraic-eikonal approach to medium energy proton scattering
from odd-mass nuclei by combining the eikonal approximation for the scattering
with a description of odd-mass nuclei in terms of the interacting boson-fermion
model. We derive closed expressions for the transition matrix elements for one
of the dynamical symmetries and discuss the interplay between collective and
single-particle degrees of freedom in an application to elastic and inelastic
proton scattering from Pt.Comment: latex, 14 pages, 4 figures uuencoded, to be published in Physical
Review
Two are better than one: Volatility forecasting using multiplicative component GARCH‐MIDAS models
We examine the properties and forecast performance of multiplicative volatility
specifications that belong to the class of generalized autoregressive conditional
heteroskedasticity–mixed-data sampling (GARCH-MIDAS) models suggested in
Engle, Ghysels, and Sohn (Review of Economics and Statistics, 2013, 95, 776–797).
In those models volatility is decomposed into a short-term GARCH component
and a long-term component that is driven by an explanatory variable. We derive
the kurtosis of returns, the autocorrelation function of squared returns, and
the R2 of a Mincer–Zarnowitz regression and evaluate the QMLE and forecast
performance of these models in a Monte Carlo simulation. For S&P 500 data,
we compare the forecast performance of GARCH-MIDAS models with a wide
range of competitor models such as HAR (heterogeneous autoregression), realized GARCH, HEAVY (high-frequency-based volatility) and Markov-switching
GARCH. Our results show that the GARCH-MIDAS based on housing starts
as an explanatory variable significantly outperforms all competitor models at
forecast horizons of 2 and 3 months ahead
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