14,016 research outputs found
Pad\'e Approximants and Resonance Poles
Based on the mathematically well defined Pad\'e Theory, a theoretically safe
new procedure for the extraction of the pole mass and width of a resonance is
proposed. In particular, thanks to the Montessus de Ballore theorem we are able
to unfold the Second Riemann Sheet of an amplitude to search for the position
of the resonant pole in the complex plane. The method is systematic and
provides a model-independent treatment of the prediction and the corresponding
errors of the approximation.Comment: 12 pages, 17 figure
Quantum Zeno-based control mechanism for molecular fragmentation
A quantum control mechanism is proposed for molecular fragmentation processes
within a scenario grounded on the quantum Zeno effect. In particular, we focus
on the van der Waals Ne-Br complex, which displays two competing
dissociation channels via vibrational and electronic predissociation.
Accordingly, realistic three dimensional wave packet simulations are carried
out by using ab initio interaction potentials recently obtained to reproduce
available experimental data. Two numerical models to simulate the repeated
measurements are reported and analyzed. It is found that the otherwise fast
vibrational predissociation is slowed down in favor of the slow electronic
(double fragmentation) predissociation, which is enhanced by several orders of
magnitude. Based on these theoretical predictions, some hints to
experimentalists to confirm their validity are also proposed.Comment: 4 pages, 3 figure
Temperature crossover of decoherence rates in chaotic and regular bath dynamics
The effect of chaotic bath dynamics on the decoherence of a quantum system is
examined for the vibrational degrees of freedom of a diatomic molecule in a
realistic, constant temperature collisional bath. As an example, the specific
case of I in liquid xenon is examined as a function of temperature, and the
results compared with an integrable xenon bath. A crossover in behavior is
found: the integrable bath induces more decoherence at low bath temperatures
than does the chaotic bath, whereas the opposite is the case at the higher bath
temperatures. These results, verifying a conjecture due to Wilkie, shed light
on the differing views of the effect of chaotic dynamics on system decoherence.Comment: 7 pages, 3 figure
Pseudoscalar pole light-by-light contributions to the muon in Resonance Chiral Theory
We have studied the transition form-factors
() within a chiral invariant framework that allows us to
relate the three form-factors and evaluate the corresponding contributions to
the muon anomalous magnetic moment , through pseudoscalar pole
contributions. We use a chiral invariant Lagrangian to describe the
interactions between the pseudo-Goldstones from the spontaneous chiral symmetry
breaking and the massive meson resonances. We will consider just the lightest
vector and pseudoscalar resonance multiplets. Photon interactions and flavor
breaking effects are accounted for in this covariant framework. This article
studies the most general corrections of order within this setting.
Requiring short-distance constraints fixes most of the parameters entering the
form-factors, consistent with previous determinations. The remaining ones are
obtained from a fit of these form-factors to experimental measurements in the
space-like () region of photon momenta. The combination of data,
chiral symmetry relations between form-factors and high-energy constraints
allows us to determine with improved precision the on-shell -pole
contribution to the Hadronic Light-by-Light scattering of the muon anomalous
magnetic moment: we obtain for
our best fit. This result was obtained excluding BaBar data, which our
analysis finds in conflict with the remaining experimental inputs. This study
also allows us to determine the parameters describing the system
in the two-mixing angle scheme and their correlations. Finally, a preliminary
rough estimate of the impact of loop corrections () and higher vector
multiplets (asym) enlarges the uncertainty up to .Comment: 43 pages, 5 figures. Accepted for publication in JHEP. New subsection
involving error analysis and some minor change
Effect of ancilla's structure on quantum error correction using the 7-qubit Calderbank-Shor-Steane code
In this work we discuss the ability of different types of ancillas to control
the decoherence of a qubit interacting with an environment. The error is
introduced into the numerical simulation via a depolarizing isotropic channel.
After the correction we calculate the fidelity as a quality criterion for the
qubit recovered. We observe that a recovery method with a three-qubit ancilla
provides reasonable good results bearing in mind its economy. If we want to go
further, we have to use fault-tolerant ancillas with a high degree of
parallelism, even if this condition implies introducing new ancilla
verification qubits.Comment: 24 pages, 10 Figures included. Accepted in Phys. Rev. A 200
Coverage of Infertility Treatment and Fertility Outcomes: Do Women Catch Up?
The ageing of first-time mothers and the changes in women's labor market conditions have been accompanied by the introduction and subsequent increase in the use of assisted reproductive therapies (ART) that help extend women's reproductive lives. Considering the financial cost of infertility treatments, policy interventions that increase insurance coverage may significantly affect fertility trends, and ultimately, population age structures. However, policies have ignored the overall impact of ART coverage on fertility. In this paper, long-term effects of insurance coverage for infertility on the timing of first births and on total fertility rates are examined. Variation in the enactment of infertility insurance mandates over time and across U.S. states allows the estimation of both the short-term and long-term effects. We concentrate on the effects of the more demanding mandates enacted in six states in the later 80s and 90s. Our results show that the effect of these mandates to cover infertility treatment is positive on the average age at first birth and increases over time. The long-term estimates of the increase in age of first-time mothers range from 3 to 5 months. Importantly, we also show that these mandates do not increase the total fertility rates of women by the end of their reproductive lives.assisted reproductive technologies, infertility insurance mandates, total fertility, synthetic control methods
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