250 research outputs found
Spectral Statistics in the Quantized Cardioid Billiard
The spectral statistics in the strongly chaotic cardioid billiard are
studied. The analysis is based on the first 11000 quantal energy levels for odd
and even symmetry respectively. It is found that the level-spacing distribution
is in good agreement with the GOE distribution of random-matrix theory. In case
of the number variance and rigidity we observe agreement with the random-matrix
model for short-range correlations only, whereas for long-range correlations
both statistics saturate in agreement with semiclassical expectations.
Furthermore the conjecture that for classically chaotic systems the normalized
mode fluctuations have a universal Gaussian distribution with unit variance is
tested and found to be in very good agreement for both symmetry classes. By
means of the Gutzwiller trace formula the trace of the cosine-modulated heat
kernel is studied. Since the billiard boundary is focusing there are conjugate
points giving rise to zeros at the locations of the periodic orbits instead of
exclusively Gaussian peaks.Comment: 20 pages, uu-encoded ps.Z-fil
MODELING THE TRANS-ATLANTIC TRANSPORTATION OF SAHARAN DUST
In the present study we are simulating the trans-Atlantic transport of dust from Sahara to the South-Central America, using the regional climate model RegCM4 and its online dust scheme, for the year 2007. The simulated horizontal and vertical distributions of the mineral dust optical properties were evaluated against the LIVAS CALIPSO satellite dust product. The Trans-Atlantic dust transport is simulated adequately with RegCM4, but there are some spatial discrepancies. Dust optical thickness is overestimated in the eastern Sahara throughout the year by 0.1-0.2, while near the gulf of Guinea is underestimated during winter and spring. Although RegCM4 dust plume is located southern on winter and spring, it doesn't spatially match the dust optical thickness of LIVAS. In summer and autumn the vertical distribution of dust between 3-4km during the Trans-Atlantic transport is simulated by the model adequately up to 30ÂșW 40ÂșW longitude. However, during winter-spring RegCM4 misplaces dust loading into higher altitude. Finally, we discuss some possible reasons and mechanisms that might be responsible for the differences between the model and the observations
Selberg Supertrace Formula for Super Riemann Surfaces III: Bordered Super Riemann Surfaces
This paper is the third in a sequel to develop a super-analogue of the
classical Selberg trace formula, the Selberg supertrace formula. It deals with
bordered super Riemann surfaces. The theory of bordered super Riemann surfaces
is outlined, and the corresponding Selberg supertrace formula is developed. The
analytic properties of the Selberg super zeta-functions on bordered super
Riemann surfaces are discussed, and super-determinants of Dirac-Laplace
operators on bordered super Riemann surfaces are calculated in terms of Selberg
super zeta-functions.Comment: 43 pages, amste
Nuclear Structure Functions in the Large x Large Q^2 Kinematic Region in Neutrino Deep Inelastic Scattering
Data from the CCFR E770 Neutrino Deep Inelastic Scattering (DIS) experiment
at Fermilab contain events with large Bjorken x (x>0.7) and high momentum
transfer (Q^2>50 (GeV/c)^2). A comparison of the data with a model based on no
nuclear effects at large x, shows a significant excess of events in the data.
Addition of Fermi gas motion of the nucleons in the nucleus to the model does
not explain the excess. Adding a higher momentum tail due to the formation of
``quasi-deuterons'' makes some improvement. An exponentially falling F_2
\propto e^-s(x-x_0) at large x, predicted by ``multi-quark clusters'' and
``few-nucleon correlations'', can describe the data. A value of s=8.3 \pm
0.7(stat.)\pm 0.7(sys.) yields the best agreement with the data.Comment: 4 pages, 4 figures, 1 table. Sibmitted to PR
Cerebral perfusion in sepsis
This article is one of ten reviews selected from the Yearbook of Intensive Care and Emergency Medicine 2010 (Springer Verlag) and co-published as a series in Critical Care. Other articles in the series can be found online at http://ccforum.com/series/yearbook. Further information about the Yearbook of Intensive Care and Emergency Medicine is available from http://www.springer.com/series/2855
Is symmetry identity?
Wigner found unreasonable the "effectiveness of mathematics in the natural
sciences". But if the mathematics we use to describe nature is simply a coded
expression of our experience then its effectiveness is quite reasonable. Its
effectiveness is built into its design. We consider group theory, the logic of
symmetry. We examine the premise that symmetry is identity; that group theory
encodes our experience of identification. To decide whether group theory
describes the world in such an elemental way we catalogue the detailed
correspondence between elements of the physical world and elements of the
formalism. Providing an unequivocal match between concept and mathematical
statement completes the case. It makes effectiveness appear reasonable. The
case that symmetry is identity is a strong one but it is not complete. The
further validation required suggests that unexpected entities might be
describable by the irreducible representations of group theory
Observation of incipient particle formation during flame synthesis by tandem differential mobility analysis-mass spectrometry (DMA-MS)
While flame aerosol reactor (FLAR) synthesis of nanoparticles is widely used to produce a range of nano-materials, incipient particle formation by nucleation and vapor condensation is not well understood. This gap in our knowledge of incipient particle formation is caused by limitations in instruments, where, during measurements, the high diffusivity of sub 3 nm particles significantly affects resolution and transport loss. This work used a high resolution differential mobility analyzer (DMA) and an atmospheric pressure interface-mass spectrometer (APi-TOF) to observe incipient particle formation during flame synthesis. By tandemly applying these two instruments, differential mobility analysis-mass spectrometry (DMA-MS) measured the size and mass of the incipient particles simultaneously, and the effective density of the sub 3 nm particles was estimated. The APi-TOF further provided the chemical compositions of the detected particles based on highly accurate masses and isotope distributions. This study investigated the incipient particle formation in flames with and without the addition of synthesis precursors. Results from FLAR using two types of precursors including tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TTIP) are presented. The effect of the precursor feed rates on incipient particle growth was also investigated. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.Peer reviewe
Limits on and Oscillations from a Precision Measurement of Neutrino-Nucleon Neutral Current Interactions
We present limits on and
oscillations based on a study of
inclusive interactions performed using the CCFR massive coarse grained
detector in the FNAL Tevatron Quadrupole Triplet neutrino beam. The sensitivity
to oscillations is from the difference in the longitudinal energy deposition
pattern of versus or charged current
interactions. The energies ranged from 30 to 500 GeV with a mean of
140 GeV. The minimum and maximum flight lengths are 0.9 km and 1.4 km
respectively. For oscillations, the lowest 90% confidence
upper limit in of is obtained at ~eV. This result is the most stringent limit to date for
eV. For oscillations, the lowest 90%
confidence upper limit in of is obtained at
~eV. This result is the most stringent limit to date for
eV, and also excludes at 90% confidence much of the
high region favored by the recent LSND observation.Comment: Revised version contains limit on oscillations as
well as limit on oscillations found in original. 15
pages, ReVTeX, 3 figures in uuencoded file, submitted to PR
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