19,005 research outputs found
Bound states of PT-symmetric separable potentials
All of the PT-symmetric potentials that have been studied so far have been
local. In this paper nonlocal PT-symmetric separable potentials of the form
, where is real, are examined.
Two specific models are examined. In each case it is shown that there is a
parametric region of the coupling strength for which the PT symmetry
of the Hamiltonian is unbroken and the bound-state energies are real. The
critical values of that bound this region are calculated.Comment: 10 pages, 3 figure
Quantum Limits of Measurements Induced by Multiplicative Conservation Laws: Extension of the Wigner-Araki-Yanase Theorem
The Wigner-Araki-Yanase (WAY) theorem shows that additive conservation laws
limit the accuracy of measurements. Recently, various quantitative expressions
have been found for quantum limits on measurements induced by additive
conservation laws, and have been applied to the study of fundamental limits on
quantum information processing. Here, we investigate generalizations of the WAY
theorem to multiplicative conservation laws. The WAY theorem is extended to
show that an observable not commuting with the modulus of, or equivalently the
square of, a multiplicatively conserved quantity cannot be precisely measured.
We also obtain a lower bound for the mean-square noise of a measurement in the
presence of a multiplicatively conserved quantity. To overcome this noise it is
necessary to make large the coefficient of variation (the so-called relative
fluctuation), instead of the variance as is the case for additive conservation
laws, of the conserved quantity in the apparatus.Comment: 8 pages, REVTEX; typo added, to appear in PR
Frequency-dependent reflection of spin waves from a magnetic inhomogeneity induced by a surface DC-current
The reflectivity of a highly localized magnetic inhomogeneity is
experimentally studied. The inhomogeneity is created by a dc-current carrying
wire placed on the surface of a ferrite film. The reflection of propagating
dipole-dominated spin-wave pulses is found to be strongly dependent on the
spin-wave frequency if the current locally increases the magnetic field. In the
opposite case the frequency dependence is negligible.Comment: 3 pages, 3 figure
Multiwavelength Mass Comparisons of the z~0.3 CNOC Cluster Sample
Results are presented from a detailed analysis of optical and X-ray
observations of moderate-redshift galaxy clusters from the Canadian Network for
Observational Cosmology (CNOC) subsample of the EMSS. The combination of
extensive optical and deep X-ray observations of these clusters make them ideal
candidates for multiwavelength mass comparison studies. X-ray surface
brightness profiles of 14 clusters with 0.17<z<0.55 are constructed from
Chandra observations and fit to single and double beta-models. Spatially
resolved temperature analysis is performed, indicating that five of the
clusters in this sample exhibit temperature gradients within their inner 60-200
kpc. Integrated spectra extracted within R_2500 provide temperature, abundance,
and luminosity information. Under assumptions of hydrostatic equilibrium and
spherical symmetry, we derive gas and total masses within R_2500 and R_200. We
find an average gas mass fraction within R_200 of 0.136 +/- 0.004, resulting in
Omega_m=0.28 +/- 0.01 (formal error). We also derive dynamical masses for these
clusters to R_200. We find no systematic bias between X-ray and dynamical
methods across the sample, with an average M(dyn)/M(X-ray) = 0.97 +/- 0.05. We
also compare X-ray masses to weak lensing mass estimates of a subset of our
sample, resulting in a weighted average of M(lens)/M(X-ray) of 0.99 +/- 0.07.
We investigate X-ray scaling relationships and find powerlaw slopes which are
slightly steeper than the predictions of self-similar models, with an E(z)^(-1)
Lx-Tx slope of 2.4 +/- 0.2 and an E(z) M_2500-Tx slope of 1.7 +/- 0.1.
Relationships between red-sequence optical richness (B_gc,red) and global
cluster X-ray properties (Tx, Lx and M_2500) are also examined and fitted.Comment: Astrophysical Journal, 48 pages, 11 figures, LaTeX. Added correction
to surface brightness normalization of MS1512.4+3647, corrections to sample
gas mass fractions and calculated value of Omega_m. Figure resolution has
been reduced to comply with astro-ph upload requirement
Happiness, environmental protection and market economy
The manufacturing sector is leaving the West for Asiaâs low wages and good working culture. Europe would be better off keeping these manufacturing activities, slowing down wage inflation and what is more, letting a young, cheaper workforce from the East settle down within their borders. This would aid in preserving the diverse economic structure which has been characteristic for Europe.Beside the economic growth there are two more concepts which have turned into the âholy cowsâ of economics during the last fifty years. One is the need to constantly improve labor productivity and the other is increasing competitiveness of nations. The high labor productivity of some countries, induces severe unemployment in the globalized world. In the other hand it is high time we understood that it is not competition, but cooperation that brings more happiness to humanity.Should we still opt for âhappinessâ and âsanityâ, it is quite obvious that we all should, in economistsâ terms, define our individual welfare functions corresponding to our own set of values, staying free from the influence of media, advertisements and fashion. The cornerstone to all this is the intelligent citizen who prefers local goods and services
The Variation of Gas Mass Distribution in Galaxy Clusters: Effects of Preheating and Shocks
We investigate the origin of the variation of the gas mass fraction in the
core of galaxy clusters, which was indicated by our work on the X-ray
fundamental plane. The adopted model supposes that the gas distribution
characterized by the slope parameter is related to the preheated temperature.
Comparison with observations of relatively hot (~> 3 keV) and low redshift
clusters suggests that the preheated temperature is about 0.5-2 keV, which is
higher than expected from the conventional galactic wind model and possibly
suggests the need for additional heating such as quasars or gravitational
heating on the largest scales at high redshift. The dispersion of the preheated
temperature may be attributed to the gravitational heating in subclusters. We
calculate the central gas fraction of a cluster from the gas distribution,
assuming that the global gas mass fraction is constant within a virial radius
at the time of the cluster collapse. We find that the central gas density thus
calculated is in good agreement with the observed one, which suggests that the
variation of gas mass fraction in cluster cores appears to be explained by
breaking the self-similarity in clusters due to preheated gas. We also find
that this model does not change major conclusions on the fundamental plane and
its cosmological implications obtained in previous papers, which strongly
suggests that not only for the dark halo but also for the intracluster gas the
core structure preserves information about the cluster formation.Comment: 17 pages, to be published in Ap
Design of a fault tolerant airborne digital computer. Volume 1: Architecture
This volume is concerned with the architecture of a fault tolerant digital computer for an advanced commercial aircraft. All of the computations of the aircraft, including those presently carried out by analogue techniques, are to be carried out in this digital computer. Among the important qualities of the computer are the following: (1) The capacity is to be matched to the aircraft environment. (2) The reliability is to be selectively matched to the criticality and deadline requirements of each of the computations. (3) The system is to be readily expandable. contractible, and (4) The design is to appropriate to post 1975 technology. Three candidate architectures are discussed and assessed in terms of the above qualities. Of the three candidates, a newly conceived architecture, Software Implemented Fault Tolerance (SIFT), provides the best match to the above qualities. In addition SIFT is particularly simple and believable. The other candidates, Bus Checker System (BUCS), also newly conceived in this project, and the Hopkins multiprocessor are potentially more efficient than SIFT in the use of redundancy, but otherwise are not as attractive
Preparation of pure and mixed polarization qubits and the direct measurement of figures of merit
Non-classical joint measurements can hugely improve the efficiency with which
certain figures of merit of quantum systems are measured. We use such a
measurement to determine a particular figure of merit, the purity, for a
polarization qubit. In the process we highlight some of subtleties involved in
common methods for generating decoherence in quantum optics.Comment: 5 pages, 3 figures, 1 tabl
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