631 research outputs found
Open inflation in the landscape
Open inflation scenario is attracting a renewed interest in the context of
string landscape. Since there are a large number of metastable de Sitter vacua
in string landscape, tunneling transitions to lower metastable vacua through
the bubble nucleation occur quite naturally. Although the deviation of Omega_0
from unity is small by the observational bound, we argue that the effect of
this small deviation on the large angle CMB anisotropies can be significant for
tensor-type perturbation in open inflation scenario. We consider the situation
in which there is a large hierarchy between the energy scale of the quantum
tunneling and that of the slow-roll inflation in the nucleated bubble. If the
potential just after tunneling is steep enough, a rapid-roll phase appears
before the slow-roll inflation. In this case the power spectrum is basically
determined by the Hubble rate during the slow-roll inflation. If such
rapid-roll phase is absent, the power spectrum keeps the memory of the high
energy density there in the large angular components. The amplitude of large
angular components can be enhanced due to the effects of the wall fluctuation
mode if the bubble wall tension is small. Therefore, one can construct some
models in which the deviation of Omega_0 from unity is large enough to produce
measurable effects. We also consider a more general class of models, where the
false vacuum decay may occur due to Hawking-Moss tunneling, as well as the
models involving more than one scalar field. We discuss scalar perturbations in
these models and point out that a large set of such models is already ruled out
by observational data, unless there was a very long stage of slow-roll
inflation after the tunneling. These results show that observational data allow
us to test various assumptions concerning the structure of the string theory
potentials and the duration of the last stage of inflation.Comment: 14 pages, 11 figures, v2:minor corrections and a reference added,
v3:accepted for publication in PR
A New Milky Way Satellite Discovered In The Subaru/Hyper Suprime-Cam Survey
We report the discovery of a new ultra-faint dwarf satellite companion of the
Milky Way based on the early survey data from the Hyper Suprime-Cam Subaru
Strategic Program. This new satellite, Virgo I, which is located in the
constellation of Virgo, has been identified as a statistically significant (5.5
sigma) spatial overdensity of star-like objects with a well-defined main
sequence and red giant branch in their color-magnitude diagram. The
significance of this overdensity increases to 10.8 sigma when the relevant
isochrone filter is adopted for the search. Based on the distribution of the
stars around the likely main sequence turn-off at r ~ 24 mag, the distance to
Virgo I is estimated as 87 kpc, and its most likely absolute magnitude
calculated from a Monte Carlo analysis is M_V = -0.8 +/- 0.9 mag. This stellar
system has an extended spatial distribution with a half-light radius of 38
+12/-11 pc, which clearly distinguishes it from a globular cluster with
comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites
known and is located beyond the reach of the Sloan Digital Sky Survey. This
demonstrates the power of this survey program to identify very faint dwarf
satellites. This discovery of VirgoI is based only on about 100 square degrees
of data, thus a large number of faint dwarf satellites are likely to exist in
the outer halo of the Milky Way.Comment: typos are corrected, 6 pages, 4 figures, accepted for publication in
Ap
Statistical mechanical analysis of the linear vector channel in digital communication
A statistical mechanical framework to analyze linear vector channel models in
digital wireless communication is proposed for a large system. The framework is
a generalization of that proposed for code-division multiple-access systems in
Europhys. Lett. 76 (2006) 1193 and enables the analysis of the system in which
the elements of the channel transfer matrix are statistically correlated with
each other. The significance of the proposed scheme is demonstrated by
assessing the performance of an existing model of multi-input multi-output
communication systems.Comment: 15 pages, 2 figure
Mutaciones y tensiones de la escuela contemporánea: miradas críticas
A fines de la década de los años 70 del siglo XX, se percibieron los primeros síntomas de las mudanzas a las que fue sometida la escuela de la modernidad. Estas variaciones fueron usadas como pretexto para exponer un profundo cambio que la época develada, la educación de masas, explosión demográfica, entre otras. La reforma estatal más importante, omnipresente, amplia y extendida de todas las épocas es la vinculación a la escuela de las dificultades propias de la economía, el Estado y las organizaciones. En los últimos treinta años se han configurado las subjetividades más complejas presentes en la historia de la escuela, donde el más crudo de los individualismos colonizó este espacio. Las anteriores mutaciones parecieran pertenecer al género de obviedades que no es preciso explicar, pues “los cambios son porque están”. De ahí que se requiera, desde miradas históricas y pedagógicas, comprender la génesis de estos cambios que determinaron el formato de la escuela contemporánea. Desde miradas genealógicas arqueológicas para futuras revisiones, este documento dará algunas pistas sobre el giro de la escuela dentro del consenso transcultural adherido a la educación de masas y sobre la creación de un dispositivo de control social del mundo escolar a través de las disciplinas escolares.Palabras clave: escuela, cambios, historia, crítica.AbstractIn the late 70s of the twentieth century, the first signs of the changes to which the School of modernity was brought under are perceived. These variations were used as a pretext to expose an existing deep change that stood out above others: education to the masses. The most important, pervasive, widespread and extensive state reform of all ages is the link to the school of the own difficulties of the economy, the State and organizations. In the last thirty years, the most complex subjectivities present in the history of the school have been set up, the crudest model of individualism colonized this space. The previous mutations seem to belong to the genre of truism that is not necessary to explain: “The changes are because they are”. Hence, it is required from historical and pedagogical understanding the genesis of these changes that determined the format of the contemporary school. From archaeological genealogical looks for future reviews, this document will give some clues about the shift of the school in the transcultural consensus adhered to the education to the masses, and the creation of a device for social control of the school system through school subjects.Keywords: school, changes, history, criticism
Feasibility of the Assessment of Cholesterol Crystals in Human Macrophages Using Micro Optical Coherence Tomography
The presence of cholesterol crystals is a hallmark of atherosclerosis, but until recently, such crystals have been considered to be passive components of necrotic plaque cores. Recent studies have demonstrated that phagocytosis of cholesterol crystals by macrophages may actively precipitate plaque progression via an inflammatory pathway, emphasizing the need for methods to study the interaction between macrophages and crystalline cholesterol. In this study, we demonstrate the feasibility of detecting cholesterol in macrophages in situ using Micro-Optical Coherence Tomography (µOCT), an imaging modality we have recently developed with 1-µm resolution. Macrophages containing cholesterol crystals frequently demonstrated highly scattering constituents in their cytoplasm on µOCT imaging, and µOCT was able to evaluate cholesterol crystals in cultured macrophage cells. Our results suggest that µOCT may be useful for the detection and characterization of inflammatory activity associated with cholesterol crystals in the coronary artery
Source Selection for Cluster Weak Lensing Measurements in the Hyper Suprime-Cam Survey
We present optimized source galaxy selection schemes for measuring cluster
weak lensing (WL) mass profiles unaffected by cluster member dilution from the
Subaru Hyper Suprime-Cam Strategic Survey Program (HSC-SSP). The ongoing
HSC-SSP survey will uncover thousands of galaxy clusters to . In
deriving cluster masses via WL, a critical source of systematics is
contamination and dilution of the lensing signal by cluster {members, and by
foreground galaxies whose photometric redshifts are biased}. Using the
first-year CAMIRA catalog of 900 clusters with richness larger than 20
found in 140 deg of HSC-SSP data, we devise and compare several
source selection methods, including selection in color-color space (CC-cut),
and selection of robust photometric redshifts by applying constraints on their
cumulative probability distribution function (PDF; P-cut). We examine the
dependence of the contamination on the chosen limits adopted for each method.
Using the proper limits, these methods give mass profiles with minimal dilution
in agreement with one another. We find that not adopting either the CC-cut or
P-cut methods results in an underestimation of the total cluster mass
() and the concentration of the profile (). The level of
cluster contamination can reach as high as at
Mpc/ for low-z clusters without cuts, while employing either the P-cut or
CC-cut results in cluster contamination consistent with zero to within the 0.5%
uncertainties. Our robust methods yield a detection of the
stacked CAMIRA surface mass density profile, with a mean mass of
.Comment: 19 pages, 4 tables, 12 figures, accepted to PASJ special issu
Thermal physics of the lead chalcogenides PbS, PbSe, and PbTe from first principles
The lead chalcogenides represent an important family of functional materials,
in particular due to the benchmark high-temperature thermoelectric performance
of PbTe. A number of recent investigations, experimental and theoretical, have
aimed to gather insight into their unique lattice dynamics and electronic
structure. However, the majority of first-principles modelling has been
performed at fixed temperatures, and there has been no comprehensive and
systematic computational study of the effect of temperature on the material
properties. We report a comparative lattice-dynamics study of the temperature
dependence of the properties of PbS, PbSe and PbTe, focussing particularly on
those relevant to thermoelectric performance, viz. phonon frequencies, lattice
thermal conductivity, and electronic band structure. Calculations are performed
within the quasi-harmonic approximation, with the inclusion of phonon-phonon
interactions from many-body perturbation theory, which are used to compute
phonon lifetimes and predict the lattice thermal conductivity. The results are
critically compared against experimental data and other calculations, and add
new insight to on-going research on the PbX compounds in relation to the
off-centring of Pb at high temperatures, which is shown to be related to phonon
softening. The agreement with experiment suggests that this method could serve
as a straightforward, powerful and generally-applicable means of investigating
the temperature dependence of material properties from first principles.Comment: Article (19 pages, 7 figures) and supporting informatio
- …