11,135 research outputs found
Integrated Light 2MASS IR Photometry of Galactic Globular Clusters
We have mosaiced 2MASS images to derive surface brightness profiles in JHK
for 104 Galactic globular clusters. We fit these with King profiles, and show
that the core radii are identical to within the errors for each of these IR
colors, and are identical to the core radii at V in essentially all cases. We
derive integrated light colors V-J, V-H, V-K_s, J-H and J-K_s for these
globular clusters. Each color shows a reasonably tight relation between the
dereddened colors and metallicity. Fits to these are given for each color. The
IR--IR colors have very small errors due largely to the all-sky photometric
calibration of the 2MASS survey, while the V-IR colors have substantially
larger uncertainties. We find fairly good agreement with measurements of
integrated light colors for a smaller sample of Galactic globular clusters by
Aaronson, Malkan & Kleinmann from 1977. Our results provide a calibration for
the integrated light of distant single burst old stellar populations from very
low to Solar metallicities. A comparison of our dereddened measured colors with
predictions from several models of the integrated light of single burst old
populations shows good agreement in the low metallicity domain for V-K_s
colors, but an offset at a fixed [Fe/H] of ~0.1 mag in J-K_s, which we ascribe
to photometric system transformation issues. Some of the models fail to
reproduce the behavior of the integrated light colors of the Galactic globular
clusters near Solar metallicity.Comment: Accepted for publication in the A
Quantum properties of the Dirac field on BTZ black hole backgrounds
We consider a Dirac field on a -dimensional uncharged BTZ black hole
background. We first find out the Dirac Hamiltonian, and study its
self-adjointness properties. We find that, in analogy to the Kerr-Newman-AdS
Dirac Hamiltonian in dimensions, essential self-adjointness on
of the reduced (radial) Hamiltonian is implemented
only if a suitable relation between the mass of the Dirac field and the
cosmological radius holds true. The very presence of a boundary-like
behaviour of is at the root of this problem. Also, we determine in a
complete way qualitative spectral properties for the non-extremal case, for
which we can infer the absence of quantum bound states for the Dirac field.
Next, we investigate the possibility of a quantum loss of angular momentum for
the -dimensional uncharged BTZ black hole. Unlike the corresponding
stationary four-dimensional solutions, the formal treatment of the level
crossing mechanism is much simpler. We find that, even in the extremal case, no
level crossing takes place. Therefore, no quantum loss of angular momentum via
particle pair production is allowed.Comment: 19 pages; IOP styl
The activation energy for GaAs/AlGaAs interdiffusion
Copyright 1997 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 82, 4842 (1997) and may be found at
Generalization of the Scheme and the Structure of the Valence Space
The scheme, which has been extensively applied to even-even nuclei,
is found to be a very good benchmark for odd-even, even-odd, and doubly-odd
nuclei as well. There are no apparent shifts in the correlations for these four
classes of nuclei. The compact correlations highlight the deviant behavior of
the Z=78 nuclei, are used to deduce effective valence proton numbers near Z=64,
and to study the evolution of the Z=64 subshell gap.Comment: 10 pages, 4 figure
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Imaging stress and magnetism at high pressures using a nanoscale quantum sensor.
Pressure alters the physical, chemical, and electronic properties of matter. The diamond anvil cell enables tabletop experiments to investigate a diverse landscape of high-pressure phenomena. Here, we introduce and use a nanoscale sensing platform that integrates nitrogen-vacancy (NV) color centers directly into the culet of diamond anvils. We demonstrate the versatility of this platform by performing diffraction-limited imaging of both stress fields and magnetism as a function of pressure and temperature. We quantify all normal and shear stress components and demonstrate vector magnetic field imaging, enabling measurement of the pressure-driven [Formula: see text] phase transition in iron and the complex pressure-temperature phase diagram of gadolinium. A complementary NV-sensing modality using noise spectroscopy enables the characterization of phase transitions even in the absence of static magnetic signatures
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