1,704 research outputs found
Volumetric reach-through displays for direct manipulation of 3D content
In my PhD, I aim at developing a reach-through volumetric display where points of light are emitted from each 3d position of the display volume, and yet it allows people to introduce theirs hands inside to directly interact with the rendered content. Here, I present TomoLit, an inverse tomographic display, where multiple emitters project rays of different intensities for each angle, rendering a target image in mid-air. We have analysed the effect on image quality of the number of emitters, their locations, the angular resolution and the levels of intensities. We have developed a simple emitter and we are in the process of putting together multiple of them. And what I plan to do next, e.g. moving from 2D to 3D and exploring interaction techniques. The feedback obtained in this symposium will clearly dissipate some of of my doubts and guide my research career.This work has been funded by Government of Navarre (FEDER) 0011-1365-2019-000086; and by Jóvenes Investigadores UPNA PJUPNA1923
Status of non-Riemannian cosmology
We provide a brief chronological guide to the literature on non-Riemannian
cosmological models. Developments in this field are traced back to the early
seventies and are given in table form.Comment: 10 pages, 1 figure, to appear in the proceedings of the 6th UCLA
Symposium on ''Sources and Detection of Dark Matter and Dark Energy in the
Universe'', 4 references added, minor typos fixe
Neuropsychological attention deficits in tuberous sclerosis complex (TSC).
Tuberous sclerosis complex (TSC) (OMIM191100) is a genetic disorder with multi-system involvement including neurodevelopmental manifestations. There is great interest in understanding the pathogenetic mechanisms underlying these neurobehavioral and neurocognitive manifestations. However, there are still significant gaps in knowledge about the exact neuropsychiatric phenotypes observed in TSC. Here we report on the first systematic evaluation of neuropsychological attentional skills in a population-derived sample of children and adolescents with TSC. The study showed that, even when age, gender, IQ, and intra-familial clustering were controlled for, the TSC group had significantly lower scores than their unaffected siblings on a range of neuropsychological attentional tasks, and that they had significantly more neuropsychological attention deficits. Eighteen of the 20 children (90%) showed deficits on one or more attentional tasks, with dual task performance most consistently impaired (85%) and visual selective attention a relative strength. Active seizures and anti-epilepsy medication did not influence attentional profiles. Furthermore, parent rating of attention-related behaviors were not able to identify children at risk of neuropsychological deficits. The findings suggest that clinical neuropsychological evaluation of attentional skills should be performed in children and adolescents with TSC even when they have normal global intellectual abilities, no seizures, and no disruptive behaviors. Results suggest that the mechanisms underlying these deficits may include contributions from structural, seizure-related and molecular factors
The Exotic Eclipsing Nucleus of the Ring Planetary Nebula SuWt2
SuWt2 is a planetary nebula (PN) consisting of a bright ionized thin ring
seen nearly edge-on. It has a bright (V=12) central star, too cool to ionize
the PN, which we discovered to be an eclipsing binary. A spectrum from IUE did
not reveal a UV source. We present extensive ground-based photometry and
spectroscopy of the central binary collected over the ensuing two decades,
resulting in the determination that the orbital period of the eclipsing pair is
4.9 d, and consists of two nearly identical A1 V stars, each of mass ~2.7
M_sun. The physical parameters of the A stars, combined with evolutionary
tracks, show that both are in the short-lived "blue-hook" evolutionary phase
that occurs between the main sequence and the Hertzsprung gap, and that the age
of the system is about 520 Myr. One puzzle is that the stars' rotational
velocities are different from each other, and considerably slower than
synchronous with the orbital period. It is possible that the center-of-mass
velocity of the eclipsing pair is varying with time, suggesting that there is
an unseen third orbiting body in the system. We propose a scenario in which the
system began as a hierarchical triple, consisting of a ~2.9 M_sun star orbiting
the close pair of A stars. Upon reaching the AGB stage, the primary engulfed
the pair into a common envelope, leading to a rapid contraction of the orbit
and catastrophic ejection of the envelope into the orbital plane. In this
picture, the exposed core of the initial primary is now a white dwarf of ~0.7
M_sun, orbiting the eclipsing pair, which has already cooled below the
detectability possible by IUE at our derived distance of 2.3 kpc and a
reddening of E(B-V)=0.40. The SuWt2 system may be destined to perish as a Type
Ia supernova. (Abridged)Comment: 60 pages, 11 figure, to appear in the Astronomical Journa
Perfect hypermomentum fluid: variational theory and equations of motion
The variational theory of the perfect hypermomentum fluid is developed. The
new type of the generalized Frenkel condition is considered. The Lagrangian
density of such fluid is stated, and the equations of motion of the fluid and
the Weyssenhoff-type evolution equation of the hypermomentum tensor are
derived. The expressions of the matter currents of the fluid (the canonical
energy-momentum 3-form, the metric stress-energy 4-form and the hypermomentum
3-form) are obtained. The Euler-type hydrodynamic equation of motion of the
perfect hypermomentum fluid is derived. It is proved that the motion of the
perfect fluid without hypermomentum in a metric-affine space coincides with the
motion of this fluid in a Riemann space.Comment: REVTEX, 23 pages, no figure
KIC 4768731: a bright long-period roAp star in theKeplerfield
We report the identification of 61.45 d−1 (711.2 μHz) oscillations, with amplitudes of 62.6 μmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21 d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of Teff = 8100 ± 200 K, log g = 4.0 ± 0.2, [Fe/H] = +0.31 ± 0.24 and v sin i = 14.8 ± 1.6 km s−1.
Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar Teff and log g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr
On the formation of oxygen-neon white dwarfs in close binary systems
The evolution of a star of initial mass 10 , and metallicity in a Close Binary System (CBS) is followed from its main sequence until
an ONe degenerate remnant forms. Restrictions have been made on the
characteristics of the companion as well as on the initial orbital parameters
in order to avoid the occurrence of reversal mass transfer before carbon is
ignited in the core. The system undergoes three mass loss episodes. The first
and second ones are a consequence of a case B Roche lobe overflow. During the
third mass loss episode stellar winds may play a role comparable to, or even
more important than Roche lobe overflow. In this paper, we extend the
previously existing calculations of stars of intermediate mass belonging to
close binary systems by following carefully the carbon burning phase of the
primary component. We also propose different possible outcomes for our scenario
and discuss the relevance of our findings. In particular, our main result is
that the resulting white dwarf component of mass more likely has
a core composed of oxygen and neon, surrounded by a mantle of carbon-oxygen
rich material. The average abundances of the oxygen-neon rich core are , , and . This result has important consequences for the Accretion
Induced Collapse scenario. The average abundances of the carbon-oxygen rich
mantle are , and . The existence of
this mantle could also play a significant role in our understanding of
cataclysmic variables.Comment: 13 pages, 12 figures, accepted for publication in A&
Convection, Thermal Bifurcation, and the Colors of A stars
Broad-band ultraviolet photometry from the TD-1 satellite and low dispersion
spectra from the short wavelength camera of IUE have been used to investigate a
long-standing proposal of Bohm-Vitense that the normal main sequence A- and
early-F stars may divide into two different temperature sequences: (1) a high
temperature branch (and plateau) comprised of slowly rotating convective stars,
and (2) a low temperature branch populated by rapidly rotating radiative stars.
We find no evidence from either dataset to support such a claim, or to confirm
the existence of an "A-star gap" in the B-V color range 0.22 <= B-V <= 0.28 due
to the sudden onset of convection. We do observe, nonetheless, a large scatter
in the 1800--2000 A colors of the A-F stars, which amounts to ~0.65 mags at a
given B-V color index. The scatter is not caused by interstellar or
circumstellar reddening. A convincing case can also be made against binarity
and intrinsic variability due to pulsations of delta Sct origin. We find no
correlation with established chromospheric and coronal proxies of convection,
and thus no demonstrable link to the possible onset of convection among the A-F
stars. The scatter is not instrumental. Approximately 0.4 mags of the scatter
is shown to arise from individual differences in surface gravity as well as a
moderate spread (factor of ~3) in heavy metal abundance and UV line blanketing.
A dispersion of ~0.25 mags remains, which has no clear and obvious explanation.
The most likely cause, we believe, is a residual imprecision in our correction
for the spread in metal abundances. However, the existing data do not rule out
possible contributions from intrinsic stellar variability or from differential
UV line blanketing effects owing to a dispersion in microturbulent velocity.Comment: 40 pages, 14 figures, 1 table, AAS LaTex, to appear in The
Astrophysical Journa
Hyperfluid - a model of classical matter with hypermomentum
A variational theory of a continuous medium is developed the elements of
which carry momentum and hypermomentum (hyperfluid). It is shown that the
structure of the sources in metric-affine gravity is predetermined by the
conservation identities and, when using the Weyssenhoff ansatz, these
explicitly yield the hyperfluid currents.Comment: plain Tex, 11 pages, no figure
The ideal relativistic rotating gas as a perfect fluid with spin
We show that the ideal relativistic spinning gas at complete thermodynamical
equilibrium is a fluid with a non-vanishing spin density tensor \sigma_\mu \nu.
After having obtained the expression of the local spin-dependent phase space
density f(x,p)_(\sigma \tau) in the Boltzmann approximation, we derive the spin
density tensor and show that it is proportional to the acceleration tensor
Omega_\mu \nu constructed with the Frenet-Serret tetrad. We recover the proper
generalization of the fundamental thermodynamical relation, involving an
additional term -(1/2) \Omega_\mu \nu \sigma^\mu \nu. We also show that the
spin density tensor has a non-vanishing projection onto the four-velocity
field, i.e. t^\mu= sigma_\mu \nu u^\nu \ne 0, in contrast to the common
assumption t^\mu = 0, known as Frenkel condition, in the thus-far proposed
theories of relativistic fluids with spin. We briefly address the viewpoint of
the accelerated observer and inertial spin effects.Comment: Final published version in Annals of Physic
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