18,695 research outputs found
Eigenfunctions for smooth expanding circle maps
We construct a real-analytic circle map for which the corresponding
Perron-Frobenius operator has a real-analytic eigenfunction with an eigenvalue
outside the essential spectral radius when acting upon -functions.Comment: 10 pages, 2 figure
Electrical transport in the ferromagnetic state of manganites: Small-polaron metallic conduction at low temperatures
We report measurements of the resistivity in the ferromagnetic state of
epitaxial thin films of La_{1-x}Ca_{x}MnO_{3} and the low temperature specific
heat of a polycrystalline La_{0.8}Ca_{0.2}MnO_{3}. The resistivity below 100 K
can be well fitted by \rho - \rho_{o} = E \omega_{s}/sinh^{2}(\hbar
\omega_{s}/2k_{B}T) with \hbar \omega_{s}/k_{B} \simeq 100 K and E being a
constant. Such behavior is consistent with small-polaron coherent motion which
involves a relaxation due to a soft optical phonon mode. The specific heat data
also suggest the existence of such a phonon mode. The present results thus
provide evidence for small-polaron metallic conduction in the ferromagnetic
state of manganites.Comment: 4 pages, 4 figures, submitted to PR
On the susceptibility function of piecewise expanding interval maps
We study the susceptibility function Psi(z) associated to the perturbation
f_t=f+tX of a piecewise expanding interval map f. The analysis is based on a
spectral description of transfer operators. It gives in particular sufficient
conditions which guarantee that Psi(z) is holomorphic in a disc of larger than
one. Although Psi(1) is the formal derivative of the SRB measure of f_t with
respect to t, we present examples satisfying our conditions so that the SRB
measure is not Lipschitz.*We propose a new version of Ruelle's conjectures.* In
v2, we corrected a few minor mistakes and added Conjectures A-B and Remark 4.5.
In v3, we corrected the perturbation (X(f(x)) instead of X(x)), in particular
in the examples from Section 6. As a consequence, Psi(z) has a pole at z=1 for
these examples.Comment: To appear Comm. Math. Phy
The Colorado School of Mines Nevada geothermal study
Geothermal systems in the Basin and Range Province of the western United States probably differ in many respects from geothermal systems already discovered in other parts of the world because of the unique tectonic setting. To investigate this, a study of the geothermal occurrences at Fly Ranch, approximately 100 miles north of Reno, Nevada, has been undertaken. Ample evidence for a geothermal system exists in this area, including the surface expression of heat flow in the form of hot springs, an extensive area of low electrical resistivity, and a high level of seismicity along faults bounding the thermal area. However, geophysical and geological studies have not yet provided evidence for a local heat source at depth. Additional detailed geophysical and geological studies, as well as drilling, must be completed before the geothermal system can be described fully
Rare events, escape rates and quasistationarity: some exact formulae
We present a common framework to study decay and exchanges rates in a wide
class of dynamical systems. Several applications, ranging form the metric
theory of continuons fractions and the Shannon capacity of contrained systems
to the decay rate of metastable states, are given
Continuity of the four-point function of massive -theory above threshold
In this paper we prove that the four-point function of massive
\vp_4^4-theory is continuous as a function of its independent external
momenta when posing the renormalization condition for the (physical) mass
on-shell. The proof is based on integral representations derived inductively
from the perturbative flow equations of the renormalization group. It closes a
longstanding loophole in rigorous renormalization theory in so far as it shows
the feasibility of a physical definition of the renormalized coupling.Comment: 23 pages; to appear in Rev. Math. Physics few corrections, two
explanatory paragraphs adde
Robust single-parameter quantized charge pumping
This paper investigates a scheme for quantized charge pumping based on
single-parameter modulation. The device was realized in an AlGaAs-GaAs gated
nanowire. We find a remarkable robustness of the quantized regime against
variations in the driving signal, which increases with applied rf power. This
feature together with its simple configuration makes this device a potential
module for a scalable source of quantized current.Comment: Submitted to Appl. Phys. Let
X-Ray Diffraction and Reflectance Spectroscopy of Murchison Powders (CM2) After Thermal Analysis Under Reducing Conditions to Final Temperatures Between 300 and 1300c
The asteroids Ryugu and Bennu have spectral characteristics in common with CI/CM type carbonaceous chondrites and are target bodies for JAXAs Hayabusa2 and NASAs OSIRIS-Rex missions, respectively. Analog studies, based primarily on the Murchison CM2 chondrite, provide a pathway to separate spectral properties resulting space weathering from those inherent to parent-body, mineralogy, chemistry, and processes. Ryugu shares spectral properties with thermally metamorphosed and partly dehydrated CI/CM chondrites. We have undertaken a multidisciplinary study of the thermal decomposition of Murchison powder samples as an analog to metamorphic process that may have occurred on Ryugu. Bulk analyses include thermal And evolved gas analysis, X-ray diffraction (XRD), and VIS-NIR and Mssbauer spectroscopy; micro- to nanoscale analyses included scanning and transmission electron microscopy and electron probe micro analysisWe report here XRD and VIS-NIR analyses of pre- and post-heated Murchison powders, and in a companion paper report results from multiple electron beam techniques
Phase transition and correlation decay in Coupled Map Lattices
For a Coupled Map Lattice with a specific strong coupling emulating
Stavskaya's probabilistic cellular automata, we prove the existence of a phase
transition using a Peierls argument, and exponential convergence to the
invariant measures for a wide class of initial states using a technique of
decoupling originally developed for weak coupling. This implies the exponential
decay, in space and in time, of the correlation functions of the invariant
measures
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