632 research outputs found
Radiative proton-antiproton annihilation and isospin mixing in protonium
A detailed analysis of the radiative annihilation is made in the
framework of a two-step formalism, the annihilates into meson
channels containing a vector meson with a subsequent conversion into a photon
via the vector dominance model (VDM). Both steps are derived from the
underlying quark model. First, branching ratios for radiative protonium
annihilation are calculated and compared with data. Then, details of the
isospin interference are studied for different models of the initial protonium
state and also for different kinematical form factors. The isospin interference
is shown to be uniquely connected to the mixing in the
protonium state. Values of the interference terms directly deduced from data
are consistent with theoretical expectations, indicating a dominant
component for the and a sizable component for the
protonium state. The analysis is extended to the
transition, where the large observed branching ratio remains unexplained in the
VDM approach.Comment: 34 pages, RevTeX, 2 figures, to appear in Phys. Rev. C; typos
correcte
Three-dimensional media for mobile devices
Cataloged from PDF version of article.This paper aims at providing an overview of the core technologies enabling the delivery of 3-D Media to next-generation mobile devices. To succeed in the design of the corresponding system, a profound knowledge about the human visual system and the visual cues that form the perception of depth, combined with understanding of the user requirements for designing user experience for mobile 3-D media, are required. These aspects are addressed first and related with the critical parts of the generic system within a novel user-centered research framework. Next-generation mobile devices are characterized through their portable 3-D displays, as those are considered critical for enabling a genuine 3-D experience on mobiles. Quality of 3-D content is emphasized as the most important factor for the adoption of the new technology. Quality is characterized through the most typical, 3-D-specific visual artifacts on portable 3-D displays and through subjective tests addressing the acceptance and satisfaction of different 3-D video representation, coding, and transmission methods. An emphasis is put on 3-D video broadcast over digital video broadcasting-handheld (DVB-H) in order to illustrate the importance of the joint source-channel optimization of 3-D video for its efficient compression and robust transmission over error-prone channels. The comparative results obtained identify the best coding and transmission approaches and enlighten the interaction between video quality and depth perception along with the influence of the context of media use. Finally, the paper speculates on the role and place of 3-D multimedia mobile devices in the future internet continuum involving the users in cocreation and refining of rich 3-D media content
Orbital and physical parameters of eclipsing binaries from the ASAS catalogue -- I. A sample of systems with components' masses between 1 and 2 M
We derive the absolute physical and orbital parameters for a sample of 18
detached eclipsing binaries from the \emph{All Sky Automated Survey} (ASAS)
database based on the available photometry and our own radial velocity
measurements. The radial velocities (RVs) are computed using spectra we
collected with the 3.9-m Anglo-Australian Telescope and its \emph{University
College London Echelle Spectrograph} and the 1.9-m SAAO Radcliffe telescope and
its \emph{Grating Instrument for Radiation Analysis with a Fibre Fed Echelle}.
In order to obtain as precise RVs as possible, most of the systems were
observed with an iodine cell available at the AAT/UCLES and/or analyzed using
the two-dimensional cross-correlation technique (TODCOR). The RVs were measured
with TODCOR using synthetic template spectra as references. However, for two
objects we used our own approach to the tomographic disentangling of the binary
spectra to provide observed template spectra for the RV measurements and to
improve the RV precision even more. For one of these binaries, AI Phe, we were
able to the obtain an orbital solution with an RV of 62 and 24 m s
for the primary and secondary respectively. For this system, the precision in
is 0.08%. For the analysis, we used the photometry available in
the ASAS database. We combined the RV and light curves using PHOEBE and JKTEBOP
codes to obtain the absolute physical parameters of the systems. Having precise
RVs we were able to reach 0.2 % precision (or better) in masses in
several cases but in radii, due to the limited precision of the ASAS
photometry, we were able to reach a precision of only 1% in one case and 3-5 %
in a few more cases. For the majority of our objects, the orbital and physical
analysis is presented for the first time.Comment: 16 pages, 2 figures, 6 tables in the main text, 1 table in appendix,
to appear in MNRA
HS Hya about to turn off its eclipses
Aims: We aim to perform the first long-term analysis of the system HS Hya.
Methods: We performed an analysis of the long-term evolution of the light
curves of the detached eclipsing system HS Hya. Collecting all available
photometric data since its discovery, the light curves were analyzed with a
special focus on the evolution of system's inclination. Results: We find that
the system undergoes a rapid change of inclination. Since its discovery until
today the system's inclination changed by more than 15 deg. The shape of the
light curve changes, and now the eclipses are almost undetectable. The third
distant component of the system is causing the precession of the close orbit,
and the nodal period is about 631 yr. Conclusions: New precise observations are
desperately needed, preferably this year, because the amplitude of variations
is decreasing rapidly every year. We know only 10 such systems on the whole sky
at present.Comment: 4 pages, 3 figures, published in 2012A&A...542L..23
ASAS Light Curves of Intermediate Mass Eclipsing Binaries and the Parameters of HI Mon
We present a catalog of 56 candidate intermediate mass eclipsing binary
systems extracted from the 3rd data release of the All Sky Automated Survey. We
gather pertinent observational data and derive orbital properties, including
ephemerides, for these systems as a prelude to anticipated spectroscopic
observations. We find that 37 of the 56, or ~66% of the systems are not
identified in the Simbad Astronomical Database as known binaries. As a specific
example, we show spectroscopic data obtained for the system HI Mon (B0 V + B0.5
V) observed at key orbital phases based on the computed ephemeris, and we
present a combined spectroscopic and photometric solution for the system and
give stellar parameters for each component.Comment: 83 pages, 63 figure
High speed photometry of faint cataclysmic variables - VI. Car2, V1040 Cen, Ha 075648, IL Nor (Nova Nor 1893), HS Pup (Nova Pup 1963), SDSS J2048-06, CSS 081419-005022 and CSS 112634-100210
We have observed 8 faint cataclysmic variable stars photometrically. The
nova-like Car2 was extensively sampled but showed little variability. V1040 Cen
was observed near the end of a dwarf nova outburst and possessed dwarf nova and
quasi-periodic oscillations. Ha 075648 has strong large amplitude flickering
and a possible orbital modulation at 3.49 h. The correct identification for the
nova remnant IL Nor (Nova Nor 1893) has been established. HS Pup (Nova Pup
1963) has a possible orbital period of 3.244 h. SDSS J2048-06 is a low mass
transfer dwarf nova that in quiescence shows slow variations at 7.67 h (though
poorly sampled with our observations) and an orbital modulation at 87.26 min.
The dwarf nova CSS 081419-005022 has an orbital period of 1.796 h and the
eclipsing dwarf nova CSS 112634-100210 has an orbital period of 1.8581 h.Comment: 7 pages, 15 figures. Accepted for publication in MNRA
On the Mixing of the Scalar Mesons , and
Based on a mass matrix describing the mixing of the scalar states
, and , the hadronic decays of the three
states are investigated. Taking into account the two possible assumptions
concerning the mass level order of the bare states
, and in the
scalar sector, and , we obtain the
glueball-quarkonia content of the three states by solving the unlinear
equations. Some predictions about the decays of the three states in two cases
are presented, which can provide a stringent consistency check of the two
assumptions.Comment: revtex 10 pages, 1 eps figur
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