8,293 research outputs found
Optical properties of charged quantum dots doped with a single magnetic impurity
We present a microscopic theory of the optical properties of self-assembled
quantum dots doped with a single magnetic manganese (Mn) impurity and
containing a controlled number of electrons. The single-particle electron and
heavy-hole electronic shells are described by two-dimensional harmonic
oscillators. The electron-electron, electron-hole Coulomb as well as the
short-range electron spin-Mn spin and hole spin-Mn spin contact exchange
interactions are included. The electronic states of the photo-excited
electron-hole-Mn complex and of the final electron-Mn complex are expanded in a
finite number of configurations and the full interacting Hamiltonian is
diagonalized numerically. The emission spectrum is predicted as a function of
photon energy for a given number of electrons and different number of confined
electronic quantum dot shells. We show how emission spectra allow to identify
the number of electronic shells, the number of electrons populating these
shells and, most importantly, their spin. We show that electrons not
interacting directly with the spin of Mn ion do so via electron-electron
interactions. This indirect interaction is a strong effect even when Mn
impurity is away from the quantum dot center.Comment: 12 pages, 10 figure
GHASP: an H{\alpha} kinematic survey of spiral and irregular galaxies -- IX. The NIR, stellar and baryonic Tully-Fisher relations
We studied, for the first time, the near infrared, stellar and baryonic
Tully-Fisher relations for a sample of field galaxies taken from an homogeneous
Fabry-Perot sample of galaxies (the GHASP survey). The main advantage of GHASP
over other samples is that maximum rotational velocities were estimated from 2D
velocity fields, avoiding assumptions about the inclination and position angle
of the galaxies. By combining these data with 2MASS photometry, optical colors,
HI masses and different mass-to-light ratio estimators, we found a slope of
4.48\pm0.38 and 3.64\pm0.28 for the stellar and baryonic Tully-Fisher relation,
respectively. We found that these values do not change significantly when
different mass-to-light ratios recipes were used. We also point out, for the
first time, that rising rotation curves as well as asymmetric rotation curves
show a larger dispersion in the Tully-Fisher relation than flat ones or than
symmetric ones. Using the baryonic mass and the optical radius of galaxies, we
found that the surface baryonic mass density is almost constant for all the
galaxies of this sample. In this study we also emphasize the presence of a
break in the NIR Tully-Fisher relation at M(H,K)\sim-20 and we confirm that
late-type galaxies present higher total-to-baryonic mass ratios than early-type
spirals, suggesting that supernova feedback is actually an important issue in
late-type spirals. Due to the well defined sample selection criteria and the
homogeneity of the data analysis, the Tully-Fisher relation for GHASP galaxies
can be used as a reference for the study of this relation in other environments
and at higher redshifts.Comment: 16 pages, 6 figures. Accepted for publication in MNRA
Kinematics and morphology of ionized gas in Hickson Compact Group 18
We present new observations of emission in the Hickson Compact
Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The
velocity field does not show motions of individual group members but, instead,
a complex common velocity field for the whole group. The gas distribution is
very asymmetric with clumps of maximum intensity coinciding with the optically
brightest knots. Comparing and HI data we conclude that HCG 18 is
not a compact group but instead a large irregular galaxy with several clumps of
star formation.Comment: Accepted for publication in Astronomical Journal (13p 6 figures
On the dynamics of bubbles in boiling water
We investigate the dynamics of many interacting bubbles in boiling water by
using a laser scattering experiment. Specifically, we analyze the temporal
variations of a laser intensity signal which passed through a sample of boiling
water. Our empirical results indicate that the return interval distribution of
the laser signal does not follow an exponential distribution; contrariwise, a
heavy-tailed distribution has been found. Additionally, we compare the
experimental results with those obtained from a minimalist phenomenological
model, finding a good agreement.Comment: Accepted for publication in Chaos, Solitons & Fractal
Dynamical effects of interactions and the Tully-Fisher relation for Hickson compact groups
We investigate the properties of the B-band Tully-Fisher (T-F) relation for
25 compact group galaxies, using Vmax derived from 2-D velocity maps. Our main
result is that the majority of the Hickson Compact Group galaxies lie on the
T-F relation. However, about 20% of the galaxies, including the lowest-mass
systems, have higher B luminosities for a given mass, or alternatively, a mass
which is too low for their luminosities. We favour a scenario in which outliers
have been brightened due to either enhanced star formation or merging.
Alternatively, the T-F outliers may have undergone truncation of their dark
halo due to interactions. It is possible that in some cases, both effects
contribute. The fact that the B-band T-F relation is similar for compact group
and field galaxies tells us that these galaxies show common mass-to-size
relations and that the halos of compact group galaxies have not been
significantly stripped inside R25. We find that 75% of the compact group
galaxies studied (22 out of 29) have highly peculiar velocity fields.
Nevertheless, a careful choice of inclination, position angle and center,
obtained from the velocity field, and an average of the velocities over a large
sector of the galaxy enabled the determination of fairly well-behaved rotation
curves for the galaxies. However, two of the compact group galaxies which are
the most massive members in M51--like pairs, HCG 91a and HCG 96a, have very
asymmetric rotation curves, with one arm rising and the other one falling,
indicating, most probably, a recent perturbation by the small close companions.Comment: 15 pages, 4 figures, accepted for publication in the Astronomical
Journa
Mass Distribution in Hickson Compact Groups of Galaxies
This study presents the mass distribution for a sample of 18 late-type
galaxies in nine Hickson Compact Groups. We used rotation curves from high
resolution 2D velocity fields of Fabry-Perot observations and J-band photometry
from the 2MASS survey, in order to determine the dark halo and the visible
matter distributions. The study compares two halo density profile, an
isothermal core-like distribution and a cuspy one. We also compare their
visible and dark matter distributions with those of galaxies belonging to
cluster and field galaxies coming from two samples: 40 cluster galaxies of
Barnes et al (2004) and 35 field galaxies of Spano et al. (2008). The central
halo surface density is found to be constant with respect to the total absolute
magnitude similar to what is found for the isolated galaxies. This suggests
that the halo density is independent to galaxy type and environment. We have
found that core-like density profiles fit better the rotation curves than
cuspy-like ones. No major differences have been found between field, cluster
and compact group galaxies with respect to their dark halo density profiles.Comment: 35 pages, 21 figures. Accept for publication in Astronomical Journa
Effective action in DSR1 quantum field theory
We present the one-loop effective action of a quantum scalar field with DSR1
space-time symmetry as a sum over field modes. The effective action has real
and imaginary parts and manifest charge conjugation asymmetry, which provides
an alternative theoretical setting to the study of the particle-antiparticle
asymmetry in nature.Comment: 8 page
2.4 GHz wireless sensor network for smart electronic shirts
This paper presents a wireless sensor network for smart electronic shirts. This allows the monitoring of individual
biomedical data, such the cardio-respiratory function. The solution chosen to transmit the bodyâs measured signals for further processing was the use of a wireless link, working at the 2.4 GHz ISM band. A radio frequency transceiver chip was
designed in a UMC RF 0.18 ”m CMOS process. The power supply of the transceiver is 1.8 V. Simulations show a power consumption of 12.9 mW. Innovative topics concerning efficient power management was taken into account during the design of the transceiver.(undefined
The Compact Group of Galaxies HCG 31 is in an early phase of merging
We have obtained high spectral resolution (R = 45900) Fabry-Perot velocity
maps of the Hickson Compact Group HCG 31 in order to revisit the important
problem of the merger nature of the central object A+C and to derive the
internal kinematics of the candidate tidal dwarf galaxies in this group. Our
main findings are: (1) double kinematic components are present throughout the
main body of A+C, which strongly suggests that this complex is an ongoing
merger (2) regions and E, to the east and south of complex A+C, present
rotation patterns with velocity amplitudes of and they
counterrotate with respect to A+C, (3) region F, which was previously thought
to be the best example of a tidal dwarf galaxy in HCG 31, presents no rotation
and negligible internal velocity dispersion, as is also the case for region
. HCG 31 presents an undergoing merger in its center (A+C) and it is likely
that it has suffered additional perturbations due to interactions with the
nearby galaxies B, G and Q.Comment: 5 pages + figures - Accepted to ApJ Lette
Comparison of 120Sn(6He,6He)120Sn and 120Sn(alpha,alpha)120Sn elastic scattering and signatures of the 6He neutron halo in the optical potential
Cross sections of Sn(,)Sn elastic scattering
have been extracted from the particle beam contamination of a recent
Sn(He,He)Sn experiment. Both reactions are analyzed
using systematic double folding potentials in the real part and smoothly
varying Woods-Saxon potentials in the imaginary part. The potential extracted
from the Sn(He,He)Sn data may be used as the basis for
the construction of a simple global He optical potential. The comparison of
the He and data shows that the halo nature of the He nucleus
leads to a clear signature in the reflexion coefficients : the relevant
angular momenta with and are shifted to
larger with a broader distribution. This signature is not present in the
scattering data and can thus be used as a new criterion for the
definition of a halo nucleus.Comment: 13 pages, 7 figures, accepted for publication in Phys. Rev.
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