39,350 research outputs found
Exchange rate dynamics in crawling-band systems
In this note we show that an exchange rate crawling-band system can borrow a portion of those aspects of a target zone that lead to its stabilizing effects on the exchange rate, depending on the relationship between the crawl rate and the drift of the fundamentals process. If the crawl rate is sufficiently high (with respect to the drift), the crawling-band is similar to a free float regime. As the crawl rate decreases, the crawling-band system collapses to a standard target zone.crawling band
Effects of nuclear molecular configurations on the astrophysical S-factor for O + O
The impact of nuclear molecular configurations on the astrophysical S-factor
for O + O is investigated within the realistic two-center shell
model based on Woods-Saxon potentials. These molecular effects refer to the
formation of a neck between the interacting nuclei and the radial dependent
collective mass parameter. It is demonstrated that the former is crucial to
explain the current experimental data with high accuracy and without any free
parameter, whilst in addition the latter predicts a pronounced maximum in the
S-factor. In contrast to very recent results by Jiang et al., the S-factor does
not decline towards extremely low values as energy decreases.Comment: In press in Physics Letters
Antiresonances as precursors of decoherence
We show that, in presence of a complex spectrum, antiresonances act as a
precursor for dephasing enabling the crossover to a fully decoherent transport
even within a unitary Hamiltonian description. This general scenario is
illustrated here by focusing on a quantum dot coupled to a chaotic cavity
containing a finite, but large, number of states using a Hamiltonian
formulation. For weak coupling to a chaotic cavity with a sufficiently dense
spectrum, the ensuing complex structure of resonances and antiresonances leads
to phase randomization under coarse graining in energy. Such phase
instabilities and coarse graining are the ingredients for a mechanism producing
decoherence and thus irreversibility. For the present simple model one finds a
conductance that coincides with the one obtained by adding a ficticious voltage
probe within the Landauer-Buettiker picture. This sheds new light on how the
microscopic mechanisms that produce phase fluctuations induce decoherence.Comment: 7 pages, 2 figures, to appear in Europhys. Let
Floquet topological transitions in a driven one-dimensional topological insulator
The Su-Schrieffer-Heeger model of polyacetylene is a paradigmatic Hamiltonian
exhibiting non-trivial edge states. By using Floquet theory we study how the
spectrum of this one-dimensional topological insulator is affected by a
time-dependent potential. In particular, we evidence the competition among
different photon-assisted processes and the native topology of the unperturbed
Hamiltonian to settle the resulting topology at different driving frequencies.
While some regions of the quasienergy spectrum develop new gaps hosting Floquet
edge states, the native gap can be dramatically reduced and the original edge
states may be destroyed or replaced by new Floquet edge states. Our study is
complemented by an analysis of Zak phase applied to the Floquet bands. Besides
serving as a simple example for understanding the physics of driven topological
phases, our results could find a promising test-ground in cold matter
experiments
Conformal mapping of ultrasonic crystals: confining ultrasound and cochlear-like wave guiding
Conformal mapping of a slab of a two-dimensional ultrasonic crystal generate
a closed geometrical arrangement of ultrasonic scatterers with appealing
acoustic properties. This acoustic shell is able to confine ultrasonic modes.
Some of these internal resonances can be induced from an external wave source.
The mapping of a linear defect produces a wave-guide that exhibits a
spatial-frequency selection analogous to that characteristic of a synthetic
"cochlea". Both, experimental and theoretical results are reported here.Comment: 4 pages, 4 figure
Two interacting atoms in a cavity: exact solutions, entanglement and decoherence
We address the problem of two interacting atoms of different species inside a
cavity and find the explicit solutions of the corresponding eigenvalues and
eigenfunctions using a new invariant. This model encompasses various commonly
used models. By way of example we obtain closed expressions for concurrence and
purity as a function of time for the case where the cavity is prepared in a
number state. We discuss the behaviour of these quantities and and their
relative behaviour in the concurrence-purity plane.Comment: 10 pages, 3 figure
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