47,179 research outputs found
Spherical Redshift Distortions
Peculiar velocities induce apparent line of sight displacements of galaxies
in redshift space, distorting the pattern of clustering in the radial versus
transverse directions. On large scales, the amplitude of the distortion yields
a measure of the dimensionless linear growth rate , where is the cosmological density and the linear
bias factor. To make the maximum statistical use of the data in a wide angle
redshift survey, and for the greatest accuracy, the spherical character of the
distortion needs to be treated properly, rather than in the simpler plane
parallel approximation. In the linear regime, the redshift space correlation
function is described by a spherical distortion operator acting on the true
correlation function. It is pointed out here that there exists an operator,
which is essentially the logarithmic derivative with respect to pair
separation, which both commutes with the spherical distortion operator, and at
the same time defines a characteristic scale of separation. The correlation
function can be expanded in eigenfunctions of this operator, and these
eigenfunctions are eigenfunctions of the distortion operator. Ratios of the
observed amplitudes of the eigenfunctions yield measures of the linear growth
rate in a manner independent of the shape of the correlation function.
More generally, the logarithmic derivative with
respect to depth , along with the square and component of the
angular momentum operator, form a complete set of commuting operators for the
spherical distortion operator acting on the density. The eigenfunctions of this
complete set of operators are spherical waves about the observer, with radial
part lying in logarithmic real or Fourier space.Comment: 15 pages, with 1 embedded EPS figur
A note on dual giant gravitons in
We study some of the properties of dual giant gravitons - D2-branes wrapped
on an - in type IIA string theory on . In particular we confirm that the spectrum of small
fluctuations about the giant is both real and independent of the size of the
graviton. We also extend previously developed techniques for attaching open
strings to giants to this D2-brane giant and focus on two particular limits of
the resulting string sigma model: In the pp-wave limit we quantize the string
and compute the spectrum of bosonic excitations while in the semiclassical
limit, we read off the fast string Polyakov action and comment on the
comparison to the Landau-Lifshitz action for the dual open spin chain.Comment: v3 significantly changed: added coupling to RR 1-form and turned on
worldvolume gauge field, computed gauge field fluctuation, added comments on
closure of the sl(2) sector and re-written to improve clarity. This version
published in JHE
THE ROLE OF CLIMATE INFORMATION IN TOURIST DESTINATION CHOICE DECISION-MAKING
This study examines if tourists actively inform themselves about the climate of their planned destination. In addition, we examine where they inform themselves and at what point in the holiday decision-making process. A self-administered questionnaire was distributed to tourists at the airport, international bus station, and the train station in Hamburg during July and August 2004. Of the 394 respondents, 73% stated that they informed themselves about the climate of their destination. Moreover, the majority of them informed themselves about climate before booking (42%). Nevertheless, a large percentage of the tourists sampled state that they informed themselves shortly before their trip. Interestingly, a significantly large share of the respondents said that they checked the weather at their destination in the week before their trip.Tourist decision-making, destination image, information search, climate, weather
Infrared diode laser spectroscopy of the fundamental band of NF(a1Δ)
Thirty-one lines of the fundamental vibration–rotation band of the NF free radical in its a 1 state have been detected in absorption near 8.6 µm using a tunable infrared diode laser. Linewidths were Doppler limited and several transitions were accompanied by resolved hyperfine structure due to fluorine and nitrogen nuclear moments. Wave number calibration using accurately determined N2O lines yielded v0 = 1165.952±0.001 cm^−1 for the band center. Rotational and centrifugal distortion constants for both v = 0 and 1 states have also been determined
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Nonlinear Torsional Wave Beams
An evolution equation with cubic nonlinearity is presented for a torsional wave beam in an isotropic elastic solid. Analytical solutions are presented for the fundamental and third harmonic in the far field of a uniform circular source. Numerical results are presented for harmonic beam patterns at an intermediate distance between the near and far fields, and for a torsional waveform with shocks.Applied Research Laboratorie
Old open clusters: UBGVRI photometry of NGC 2506
UBGVRI photometry for the open cluster NGC 2506 is presented. From comparison
of the observed colour-magnitude diagrams with simulations based on stellar
evolutionary models we derive in a self consistent way reddening, distance, and
age of the cluster: E(B-V)=0-0.07, (m-M)o = 12.6, age = 1.5-2.2 Gyr. The
cluster shows a well definite secondary sequence, suggesting that binary
systems constitute about 20 % of the cluster members visible in the
colour-magnitude diagram.Comment: 11 pages, 7 figures, MNRAS latex style, accepte
Multiband Mechanism for the Sign Reversal of Coulomb Drag Observed in Double Bilayer Graphene Heterostructures
Coupled 2D sheets of electrons and holes are predicted to support novel
quantum phases. Two experiments of Coulomb drag in electron-hole (e-h) double
bilayer graphene (DBLG) have reported an unexplained and puzzling sign reversal
of the drag signal. However, we show that this effect is due to the multiband
character of DBLG. Our multiband Fermi liquid theory produces excellent
agreement and captures the key features of the experimental drag resistance for
all temperatures. This demonstrates the importance of multiband effects in
DBLG: they have a strong effect not only on superfluidity, but also on the
drag.Comment: 5 pages, 3 figure
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Coupled Pulsation And Translation Of A Gas Bubble And Rigid Particle
A nonlinear analytic model describing the interaction of a spherical gas bubble and spherical rigid particle is presented. Both the bubble and particle are free to translate. The model is accurate to fifth order in terms of a nondimensional expansion parameter R/d, where R is a characteristic radius and d is the distance separating the bubble and particle. Numerical simulation results are presented to demonstrate the effects of key particle parameters and an external acoustic source.Applied Research Laboratorie
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