18,322 research outputs found
The stellar content of the Local Group dwarf galaxy Phoenix
We present new deep ground-based photometry of the Local Group dwarf
galaxy Phoenix. Our results confirm that this galaxy is mainly dominated by red
stars, with some blue plume stars indicating recent (100 Myr old) star
formation in the central part of the galaxy. We have performed an analysis of
the structural parameters of Phoenix based on an ESO/SRC scanned plate, in
order to search for differentiated component. The results were then used to
obtain the color-magnitude diagrams for three different regions of Phoenix in
order to study the variation of the properties of its stellar population. The
young population located in the central component of Phoenix shows a clear
asymmetry in its distribution, that could indicate a propagation of star
formation across the central component. The HI cloud found at 6 arcmin
Southwest by Young & Lo (1997) could have been involved in this process.
We also find the presence of a substantial intermediate-age population in the
central region of Phoenix that would be less abundant or absent in its outer
regions. This result is also consistent with the gradient found in the number
of horizontal branch stars, whose frequency relative to red giant branch stars
increases towards the outer part of the galaxy. These results, together with
those of our morphological study, suggest the existence of an old, metal-poor
population with a spheroidal distribution surrounding the younger inner
component of Phoenix. This two-component structure may resemble the halo-disk
structure observed in spirals, although more data, in particular on kinematics,
are necessary to confirm this.Comment: 46 pages, 21 figures, 9 Tables, to be published in AJ, August 9
Thanks, but no thanks: women's avoidance of help-seeking in the context of a dependency-related stereotype
The stereotype that women are dependent on men is a commonly verbalized, potentially damaging aspect of benevolent sexism. We investigated how women may use behavioral disconfirmation of the personal applicability of the stereotype to negotiate such sexism. In an experiment (N = 86), we manipulated female college studentsâ awareness that women may be stereotyped by men as dependent. We then placed participants in a situation where they needed help. Women made aware of the dependency stereotype (compared to controls who were not) were less willing to seek help. They also displayed a stronger negative correlation between help-seeking and post help-seeking affect - such that the more help they sought, the worse they felt. We discuss the relevance of these findings for research concerning womenâs help-seeking and their management of sexist stereotyping in everyday interaction. We also consider the implications of our results for those working in domains such as healthcare, teaching and counseling, where interaction with individuals in need and requiring help is common
Equivariant Poincar\'e series of filtrations and topology
Earlier, for an action of a finite group on a germ of an analytic
variety, an equivariant -Poincar\'e series of a multi-index filtration in
the ring of germs of functions on the variety was defined as an element of the
Grothendieck ring of -sets with an additional structure. We discuss to which
extend the -Poincar\'e series of a filtration defined by a set of curve or
divisorial valuations on the ring of germs of analytic functions in two
variables determines the (equivariant) topology of the curve or of the set of
divisors
Semiquantitative theory of electronic Raman scattering from medium-size quantum dots
A consistent semiquantitative theoretical analysis of electronic Raman
scattering from many-electron quantum dots under resonance excitation
conditions has been performed. The theory is based on
random-phase-approximation-like wave functions, with the Coulomb interactions
treated exactly, and hole valence-band mixing accounted for within the
Kohn-Luttinger Hamiltonian framework. The widths of intermediate and final
states in the scattering process, although treated phenomenologically, play a
significant role in the calculations, particularly for well above band gap
excitation. The calculated polarized and unpolarized Raman spectra reveal a
great complexity of features and details when the incident light energy is
swept from below, through, and above the quantum dot band gap. Incoming and
outgoing resonances dramatically modify the Raman intensities of the single
particle, charge density, and spin density excitations. The theoretical results
are presented in detail and discussed with regard to experimental observations.Comment: Submitted to Phys. Rev.
Storage of classical information in quantum spins
Digital magnetic recording is based on the storage of a bit of information in
the orientation of a magnetic system with two stable ground states. Here we
address two fundamental problems that arise when this is done on a quantized
spin: quantum spin tunneling and back-action of the readout process. We show
that fundamental differences exist between integer and semi-integer spins when
it comes to both, read and record classical information in a quantized spin.
Our findings imply fundamental limits to the miniaturization of magnetic bits
and are relevant to recent experiments where spin polarized scanning tunneling
microscope reads and records a classical bit in the spin orientation of a
single magnetic atom
Black hole evaporation with separated fermions
In models with a low quantum gravity scale, a well-motivated reason to expect
quark and lepton fields are localized but physically separated is to avoid
proton decay. This could happen in a ``fat-brane'' or in an additional,
orthogonal 1/TeV sized dimension in which the gauge and Higgs fields live
throughout. Black holes with masses of order the quantum gravity scale are
therefore expected to evaporate non-universally, preferentially radiating
directly into quarks or leptons but not both. Should black holes be copiously
produced at a future hadron collider, we find the ratio of final state jets to
charged leptons to photons is 113:8:1, which differs from previous analyses
that assumed all standard model fields live at the same point in the extra
dimensional space.Comment: 5 pages, REVTe
Quantum simulation of Anderson and Kondo lattices with superconducting qubits
We introduce a mapping between a variety of superconducting circuits and a
family of Hamiltonians describing localized magnetic impurities interacting
with conduction bands. This includes the Anderson model, the single impurity
one- and two-channel Kondo problem, as well as the 1D Kondo lattice. We compare
the requirements for performing quantum simulations using the proposed circuits
to those of universal quantum computation with superconducting qubits, singling
out the specific challenges that will have to be addressed.Comment: Longer versio
Measurement of the parity violating 6S-7S transition amplitude in cesium achieved within 2 \times 10^{-13} atomic-unit accuracy by stimulated-emission detection
We exploit the process of asymmetry amplification by stimulated emission
which provides an original method for parity violation (PV) measurements in a
highly forbidden atomic transition. The method involves measurements of a
chiral, transient, optical gain of a cesium vapor on the 7S-6P_{3/2}
transition, probed after it is excited by an intense, linearly polarized,
collinear laser, tuned to resonance for one hyperfine line of the forbidden
6S-7S transition in a longitudinal electric field. We report here a 3.5 fold
increase, of the one-second-measurement sensitivity, and subsequent reduction
by a factor of 3.5 of the statistical accuracy compared with our previous
result [J. Gu\'ena et al., Phys. Rev. Lett. 90, 143001 (2003)]. Decisive
improvements to the set-up include an increased repetition rate, better
extinction of the probe beam at the end of the probe pulse and, for the first
time to our knowledge, the following: a polarization-tilt magnifier,
quasi-suppression of beam reflections at the cell windows, and a Cs cell with
electrically conductive windows. We also present real-time tests of systematic
effects, consistency checks on the data, as well as a 1% accurate measurement
of the electric field seen by the atoms, from atomic signals. PV measurements
performed in seven different vapor cells agree within the statistical error.
Our present result is compatible with the more precise Boulder result within
our present relative statistical accuracy of 2.6%, corresponding to a 2 \times
10^{-13} atomic-unit uncertainty in E_1^{pv}. Theoretical motivations for
further measurements are emphasized and we give a brief overview of a recent
proposal that would allow the uncertainty to be reduced to the 0.1% level by
creating conditions where asymmetry amplification is much greater.Comment: Article 21 pages, 6 figures, 3 tables Typos, addition of few comments
and little more data (1 week) leading to a slight reduction of the error bar
Accepted for publication in Phys.Rev.
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