50,367 research outputs found
Bimodality as a signal of Liquid-Gas phase transition in nuclei?
We use the HIPSE (Heavy-Ion Phase-Space Exploration) Model to discuss the
origin of the bimodality in charge asymmetry observed in nuclear reactions
around the Fermi energy. We show that it may be related to the important
angular momentum (spin) transferred into the quasi-projectile before secondary
decay. As the spin overcomes the critical value, a sudden opening of decay
channels is induced and leads to a bimodal distribution for the charge
asymmetry. In the model, it is not assigned to a liquid-gas phase transition
but to specific instabilities in nuclei with high spin. Therefore, we propose
to use these reactions to study instabilities in rotating nuclear droplets.Comment: 4 pages, 4 figures Accepted to PR
Precise comparison of theory and new experiment for the Casimir force leads to stronger constraints on thermal quantum effects and long-range interactions
We report an improved dynamic determination of the Casimir pressure between
two plane plates obtained using a micromachined torsional oscillator. The main
improvements in the current experiment are a significant suppression of the
surface roughness of the Au layers deposited on the interacting surfaces, and a
decrease in the experimental error in the measurement of the absolute
separation. A metrological analysis of all data permitted us to determine both
the random and systematic errors, and to find the total experimental error as a
function of separation at the 95% confidence level. In contrast to all previous
experiments on the Casimir effect, our smallest experimental error (%) is achieved over a wide separation range. The theoretical Casimir
pressures in the experimental configuration were calculated by the use of four
theoretical approaches suggested in the literature. All corrections to the
Casimir force were calculated or estimated. All theoretical errors were
analyzed and combined to obtain the total theoretical error at the 95%
confidence level. Finally, the confidence interval for the differences between
theoretical and experimental pressures was obtained as a function of
separation. Our measurements are found to be consistent with two theoretical
approaches utilizing the plasma model and the surface impedance over the entire
measurement region. Two other approaches to the thermal Casimir force,
utilizing the Drude model or a special prescription for the determination of
the zero-frequency contribution to the Lifshitz formula, are excluded on the
basis of our measurements at the 99% and 95% confidence levels, respectively.
Finally, constraints on Yukawa-type hypothetical interactions are strengthened
by up to a factor of 20 in a wide interaction range.Comment: 43 pages, 15 figures, elsart.cls is used. Accepted for publication in
Annals of Physics. (Several misprints in the text are corrected.
String solutions in Chern-Simons-Higgs model coupled to an axion
We study a d=2+1 dimensional Chern-Simons gauge theory coupled to a Higgs
scalar and an axion field, finding the form of the potential that allows the
existence of selfdual equations and the corresponding Bogomolny bound for the
energy of static configurations. We show that the same conditions allow for the
N=2 supersymmetric extension of the model, reobtaining the BPS equations from
the supersymmetry requirement. Explicit electrically charged vortex-like
solutions to these equations are presented.Comment: 11 pages, 3 figure
Threading the spindle: a geometric study of chiral liquid crystal polymer microparticles
Polymeric particles are strong candidates for designing artificial materials
capable of emulating the complex twisting-based functionality observed in
biological systems. In this letter, we provide the first detailed investigation
of the swelling behavior of bipolar polymer liquid crystalline microparticles.
Deswelling from the spherical bipolar configuration causes the microparticle to
contract anisotropically and twist in the process, resulting in a twisted
spindle shaped structure. We propose a model to describe the observed spiral
patterns and twisting behavior
Child education and work choices in the presence of a conditional cash transfer programme in rural Colombia
This research is part of a large evaluation effort, undertaken by a consortium formed by IFS, Econometria and SEI, which has considered the effects of Familias en Accion on a variety of outcomes one year after its implementation. In early reports, we focussed on the effects of the programme on school enrolment. In this paper, we both expand those results, by carefully analysing anticipation effects along with other issues, and complement them with an analysis of child labour - both paid and unpaid (including domestic) work. The child labour analysis is made possible due to a rich time use module of the surveys that has not previously been analysed. We find that the programme increased the school participation rates of 14 to 17 year old children quite substantially, by between 5 and 7 percentage points, and had lower, but non-negligible effects on the enrolment of younger children of between 1.4 and 2.4 percentage points. In terms of work, the effects are generally largest for younger children whose participation in domestic work decreased by around 10 to 12 percentage points after the programme but whose participation in income-generating work remained largely unaffected by the programme. We also find evidence of school and work time not being fully substitutable, suggesting that some, but not all, of the increased time at school may be drawn from children's leisure time
Inflation expectations and risk premiums in an arbitrage-free model of nominal and real bond yields
Differences between yields on comparable-maturity U.S. Treasury nominal and real debt, the so-called breakeven inflation (BEI) rates, are widely used indicators of inflation expectations. However, better measures of inflation expectations could be obtained by subtracting inflation risk premiums from the BEI rates. We provide such decompositions using an estimated affine arbitrage-free model of the term structure that captures the pricing of both nominal and real Treasury securities. Our empirical results suggest that long-term inflation expectations have been well anchored over the past few years, and inflation risk premiums, although volatile, have been close to zero on average.Inflation (Finance) ; Treasury bonds
Extracting deflation probability forecasts from Treasury yields
We construct probability forecasts for episodes of price deflation (i.e., a falling price level) using yields on nominal and real U.S. Treasury bonds. The deflation probability forecasts identify two "deflation scares" during the past decade: a mild one following the 2001 recession, and a more serious one starting in late 2008 with the deepening of the financial crisis. The estimated deflation probabilities are generally consistent with those from macroeconomic models and surveys of professional forecasters, but they also provide highfrequency insight into the views of financial market participants. The probabilities can also be used to price the deflation option embedded in real Treasury bonds.Deflation (Finance)
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