2,316 research outputs found
Double butterfly spectrum for two interacting particles in the Harper model
We study the effect of interparticle interaction on the spectrum of the
Harper model and show that it leads to a pure-point component arising from the
multifractal spectrum of non interacting problem. Our numerical studies allow
to understand the global structure of the spectrum. Analytical approach
developed permits to understand the origin of localized states in the limit of
strong interaction and fine spectral structure for small .Comment: revtex, 4 pages, 5 figure
Expansion of nanoplasmas and laser-driven nuclear fusion in single exploding clusters
The expansion of laser-irradiated clusters or nanodroplets depends strongly
on the amount of energy delivered to the electrons and can be controlled by
using appropriately shaped laser pulses. In this paper, a self-consistent
kinetic model is used to analyze the transition from quasineutral,
hydrodinamic-like expansion regimes to the Coulomb explosion (CE) regime when
increasing the ratio between the thermal energy of the electrons and the
electrostatic energy stored in the cluster. It is shown that a suitable
double-pump irradiation scheme can produce hybrid expansion regimes, wherein a
slow hydrodynamic expansion is followed by a fast CE, leading to ion overtaking
and producing multiple ion flows expanding with different velocities. This can
be exploited to obtain intracluster fusion reactions in both homonuclear
deuterium clusters and heteronuclear deuterium-tritium clusters, as also proved
by three-dimensional molecular-dynamics simulations.Comment: 9 pages, 3 figures, to appear in Plasma Physics and Controlled Fusio
Bloch electron in a magnetic field and the Ising model
The spectral determinant det(H-\epsilon I) of the Azbel-Hofstadter
Hamiltonian H is related to Onsager's partition function of the 2D Ising model
for any value of magnetic flux \Phi=2\pi P/Q through an elementary cell, where
P and Q are coprime integers. The band edges of H correspond to the critical
temperature of the Ising model; the spectral determinant at these (and other
points defined in a certain similar way) is independent of P. A connection of
the mean of Lyapunov exponents to the asymptotic (large Q) bandwidth is
indicated.Comment: 4 pages, 1 figure, REVTE
Differential Accumulation of Antioxidant mRNAs in Arabidopsis thaliana Exposed to Ozone
Expression Patterns of Duplicate Tryptophan Synthase [beta] Genes in Arabidopsis thaliana
Direct Observation of Hyperfine Quenching of the (2)3p0 Level in Helium-Like Nickel
Journals published by the American Physical Society can be found at http://publish.aps.org/We report a clear demonstration of the effect of hyperfine quenching of a forbidden transition by direct comparison of the lifetimes of the 2 3P0 level in the heliumlike isotopes Ni-61(26+) and Ni-58(26+). We find the quenched lifetime of the 2 3P0 level in Ni-61(26+) to be 470(50) ps. From this we deduce the 2 3P0-2 3P1 energy splitting to be 2.33(15) eV. We also report a measurement of the lifetime of the 2 3P2 level in Ni-58(26+), which is found to be 70(3) ps
Acceptance conditions in automated negotiation
In every negotiation with a deadline, one of the negotiating parties has to accept an offer to avoid a break off. A break off is usually an undesirable outcome for both parties, therefore it is important that a negotiator employs a proficient mechanism to decide under which conditions to accept. When designing such conditions one is faced with the acceptance dilemma: accepting the current offer may be suboptimal, as better offers may still be presented. On the other hand, accepting too late may prevent an agreement from being reached, resulting in a break off with no gain for either party. Motivated by the challenges of bilateral negotiations between automated agents and by the results and insights of the automated negotiating agents competition (ANAC), we classify and compare state-of-the-art generic acceptance conditions. We focus on decoupled acceptance conditions, i.e. conditions that do not depend on the bidding strategy that is used. We performed extensive experiments to compare the performance of acceptance conditions in combination with a broad range of bidding strategies and negotiation domains. Furthermore we propose new acceptance conditions and we demonstrate that they outperform the other conditions that we study. In particular, it is shown that they outperform the standard acceptance condition of comparing the current offer with the offer the agent is ready to send out. We also provide insight in to why some conditions work better than others and investigate correlations between the properties of the negotiation environment and the efficacy of acceptance condition
Arabidopsis Mutants Lacking Phenolic Sunscreens Exhibit Enhanced Ultraviolet-B Injury and Oxidative Damage
Second order analysis of geometric functionals of Boolean models
This paper presents asymptotic covariance formulae and central limit theorems
for geometric functionals, including volume, surface area, and all Minkowski
functionals and translation invariant Minkowski tensors as prominent examples,
of stationary Boolean models. Special focus is put on the anisotropic case. In
the (anisotropic) example of aligned rectangles, we provide explicit analytic
formulae and compare them with simulation results. We discuss which information
about the grain distribution second moments add to the mean values.Comment: Chapter of the forthcoming book "Tensor Valuations and their
Applications in Stochastic Geometry and Imaging" in Lecture Notes in
Mathematics edited by Markus Kiderlen and Eva B. Vedel Jensen. (The second
version mainly resolves minor LaTeX problems.
Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr_(9-x)PbxCe2Ti2O36 (x=0-9) Ceramic System
Sr_(9-x)PbxCe2Ti12O36 system is derived from the perovskite SrTiO3 and its
chemical formula can be written as (Sr_(1-y)Pby)0.75Ce0.167TiO3. We
investigated dielectric response of Sr_(9-x)PbxCe2Ti12O36 ceramics (x = 0-9)
between 100 Hz and 100 THz at temperatures from 10 to 700 K using low- and
high-frequency dielectric, microwave (MW), THz and infrared spectroscopy. We
revealed that Sr9Ce2Ti12O36 is an incipient ferroelectric with the R-3c
trigonal structure whose relative permittivity e' increases from 167 at 300 K
and saturates near 240 below 30 K. The subsequent substitution of Sr by Pb
enhances e' to several thousands and induces a ferroelectric phase transition
to monoclinic Cc phase for x>=3. Its critical temperature Tc linearly depends
on the Pb concentration and reaches 550 K for x=9. The phase transition is of
displacive type. The soft mode frequency follows the Barrett formula in samples
with x=3.
The MW dispersion is lacking and quality factor Q is high in samples with low
Pb concentration, although the permittivity is very high in some cases.
However, due to the lattice softening, the temperature coefficient of the
permittivity is rather high. The best MW quality factor was observed for x=1:
Q*f=5800 GHz and e'=250. Concluding, the dielectric properties of Sr_(9-
x)PbxCe2Ti12O36 are similar to those of Ba_(1-x)SrxTiO3 so that this system can
be presumably used as an alternative for MW devices or capacitors.Comment: subm. to Chem. Mate
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