16,602 research outputs found
Science Enabled by the Ares V: A Large Monolithic Telescope Placed at the Second Sun-Earth Lagrange Point
The payload mass and volume capabilities of the planned Ares V launch vehicle provide the science community with unprecedented opportunities to place large science payloads into low earth orbit and beyond. One example, the outcome of a recent study conducted at the NASA Marshall Space Flight Center, is a large, monolithic telescope with a primary mirror diameter of 6.2 meters placed into a halo orbit about the second Sun-Earth Lagrange point, or L2, approximately 1.5 million kin beyond Earth's orbit. Operating in the visible and ultraviolet regions of the electromagnetic spectrum, such a large telescope would allow astronomers to detect bio-signatures and characterize the atmospheres of transiting exoplanets, provide high resolution imaging three or more times better than the Hubble Space Telescope and the James Webb Space Telescope, and observe the ultraviolet light from warm baryonic matter
The topological classification of one-dimensional symmetric quantum walks
We give a topological classification of quantum walks on an infinite 1D
lattice, which obey one of the discrete symmetry groups of the tenfold way,
have a gap around some eigenvalues at symmetry protected points, and satisfy a
mild locality condition. No translation invariance is assumed. The
classification is parameterized by three indices, taking values in a group,
which is either trivial, the group of integers, or the group of integers modulo
2, depending on the type of symmetry. The classification is complete in the
sense that two walks have the same indices if and only if they can be connected
by a norm continuous path along which all the mentioned properties remain
valid. Of the three indices, two are related to the asymptotic behaviour far to
the right and far to the left, respectively. These are also stable under
compact perturbations. The third index is sensitive to those compact
perturbations which cannot be contracted to a trivial one. The results apply to
the Hamiltonian case as well. In this case all compact perturbations can be
contracted, so the third index is not defined. Our classification extends the
one known in the translation invariant case, where the asymptotic right and
left indices add up to zero, and the third one vanishes, leaving effectively
only one independent index. When two translationally invariant bulks with
distinct indices are joined, the left and right asymptotic indices of the
joined walk are thereby fixed, and there must be eigenvalues at or
(bulk-boundary correspondence). Their location is governed by the third index.
We also discuss how the theory applies to finite lattices, with suitable
homogeneity assumptions.Comment: 36 pages, 7 figure
An experimental study on (2) modular symmetry in the quantum Hall system with a small spin-splitting
Magnetic-field-induced phase transitions were studied with a two-dimensional
electron AlGaAs/GaAs system. The temperature-driven flow diagram shows the
features of the (2) modular symmetry, which includes distorted
flowlines and shiftted critical point. The deviation of the critical
conductivities is attributed to a small but resolved spin splitting, which
reduces the symmetry in Landau quantization. [B. P. Dolan, Phys. Rev. B 62,
10278.] Universal scaling is found under the reduction of the modular symmetry.
It is also shown that the Hall conductivity could still be governed by the
scaling law when the semicircle law and the scaling on the longitudinal
conductivity are invalid. *corresponding author:[email protected]: The revised manuscript has been published in J. Phys.: Condens.
Matte
Calculation of electrostatic fields using quasi-Green's functions: application to the hybrid Penning trap.
Penning traps offer unique possibilities for storing, manipulating and investigating charged particles with high sensitivity and accuracy. The widespread applications of Penning traps in physics and chemistry comprise e.g. mass spectrometry, laser spectroscopy, measurements of electronic and nuclear magnetic moments, chemical sample analysis and reaction studies. We have developed a method, based on the Green's function approach, which allows for the analytical calculation of the electrostatic properties of a Penning trap with arbitrary electrodes. The ansatz features an extension of Dirichlet's problem to nontrivial geometries and leads to an analytical solution of the Laplace equation. As an example we discuss the toroidal hybrid Penning trap designed for our planned measurements of the magnetic moment of the (anti)proton. As in the case of cylindrical Penning traps, it is possible to optimize the properties of the electric trapping fields, which is mandatory for high-precision experiments with single charged particles. Of particular interest are the anharmonicity compensation, orthogonality and optimum adjustment of frequency shifts by the continuous SternGerlach effect in a quantum jump spectrometer. The mathematical formalism developed goes beyond the mere design of novel Penning traps and has potential applications in other fields of physics and engineering
Extended Magnetic Dome Induced by Low Pressures in Superconducting FeSeS
We report muon spin rotation (SR) and magnetization measurements under
pressure on FeSeS with x
.Above GPa we find microscopic coexistence of
superconductivity with an extended dome of long range magnetic order that spans
a pressure range between previously reported separated magnetic phases. The
magnetism initially competes on an atomic scale with the coexisting
superconductivity leading to a local maximum and minimum of the superconducting
. The maximum of corresponds to the onset of
magnetism while the minimum coincides with the pressure of strongest
competition. A shift of the maximum of for a series of single
crystals with x up to 0.14 roughly extrapolates to a putative magnetic and
superconducting state at ambient pressure for x .Comment: 10 pages, 6 figures, including supplemental materia
Multipole Expansion of Bremsstrahlung in Intermediate Energy Heavy Ion Collisions
Using a multipole expansion of the radiated field generated by a classical
electric current, we present a way to interprete the bremsstrahlung spectra of
low energy heavy ion collisions. We perform the calculation explicitely for the
system ^{12}C+ ^{12}C at 84AMeV and compare the result with the experimental
data of E. Grosse et al. Using simple model assumptions for the electromagnetic
source current we are able to describe the measured data in terms of coherent
photon emission. In this context, the information contained in the measured
data is discussed.Comment: LaTex, 4 Figure
The Pricing Behaviour of Firms in the Euro Area: New Survey Evidence
This study investigates the pricing behaviour of firms in the euro area on the basis of surveys conducted by nine Eurosystem national central banks. Overall, more than 11,000 firms participated in the survey. The results are very robust across countries. Firms operate in monopolistically competitive markets, where prices are mostly set following mark-up rules and where price discrimination is a common practice. Our evidence suggests that both time- and state-dependent pricing strategies are applied by firms in the euro area: around one-third of the companies follow mainly time-dependent pricing rules while two-thirds use pricing rules with some element of state-dependence. Although the majority of firms take into account a wide range of information, including past and expected economic developments, about one-third adopts a purely backward-looking behaviour. The pattern of results lends support to the recent wave of estimations of hybrid versions of the New Keynesian Phillips Curve. Price stickiness arises both at the stage when firms review their prices and again when they actually change prices. The most relevant factors underlying price rigidity are customer relationships â as expressed in the theories about explicit and implicit contracts â and thus, are mainly found at the price changing (second) stage of the price adjustment process. Finally, we provide evidence that firms adjust prices asymmetrically in response to shocks, depending on the direction of the adjustment and the source of the shock: while cost shocks have a greater impact when prices have to be raised than when they have to be reduced, reductions in demand are more likely to induce a price change than increases in demand.
The pricing behaviour of firms in the euro area : new survey evidence
This study investigates the pricing behaviour of firms in the euro area on the basis of surveys conducted by nine Eurosystem national central banks. Overall, more than 11,000 firms participated in the survey. The results are very robust across countries. Firms operate in monopolistically competitive markets, where prices are mostly set following mark-up rules and where price discrimination is a common practice. Our evidence suggests that both time- and state-dependent pricing strategies are applied by firms in the euro area: around one-third of the companies follow mainly time-dependent pricing rules while two-thirds use pricing rules with some element of state-dependence. Although the majority of firms take into account a wide range of information, including past and expected economic developments, about one-third adopts a purely backward-looking behaviour. The pattern of results lends support to the recent wave of estimations of hybrid versions of the New Keynesian Phillips Curve. Price stickiness arises both at the stage when firms review their prices and again when they actually change prices. The most relevant factors underlying price rigidity are customer relationships - as expressed in the theories about explicit and implicit contracts - and thus, are mainly found at the price changing (second) stage of the price adjustment process. Finally, we provide evidence that firms adjust prices asymmetrically in response to shocks, depending on the direction of the adjustment and the source of the shock: while cost shocks have a greater impact when prices have to be raised than when they have to be reduced, reductions in demand are more likely to induce a price change than increases in demand.price setting, nominal rigidity, real rigidity, inflation persistence, survey data.
Spectroscopic and photometric oscillatory envelope variability during the S Doradus outburst of the Luminous Blue Variable R71
To better understand the LBV phenomenon, we analyze multi-epoch and
multi-wavelength spectra and photometry of R71. Pre-outburst spectra are
analyzed with the radiative transfer code CMFGEN to determine the star's
fundamental stellar parameters. During quiescence, R71 has an effective
temperature of and a luminosity of
log = 5.78 and is thus a classical LBV, but at the lower
luminosity end of this group. We determine its mass-loss rate to yr. We present R71's spectral energy distribution
from the near-ultraviolet to the mid-infrared during its present outburst.
Mid-infrared observations suggest that we are witnessing dust formation and
grain evolution. Semi-regular oscillatory variability in the star's light curve
is observed during the current outburst. Absorption lines develop a second blue
component on a timescale twice that length. The variability may consist of one
(quasi-)periodic component with P ~ 425/850 d with additional variations
superimposed. During its current S Doradus outburst, R71 occupies a region in
the HR diagram at the high-luminosity extension of the Cepheid instability
strip and exhibits similar irregular variations as RV Tau variables. LBVs do
not pass the Cepheid instability strip because of core evolution, but they
develop comparable cool, low-mass, extended atmospheres in which convective
instabilities may occur. As in the case of RV Tau variables, the occurrence of
double absorption lines with an apparent regular cycle may be due to shocks
within the atmosphere and period doubling may explain the factor of two in the
lengths of the photometric and spectroscopic cycles.Comment: 18 pages, 14 figures, submitted to A&
- âŠ