99 research outputs found
Contesti in volo
Traditional design tools and procedures are not always appropriate to tackle the continuous movement of buildings and contexts. Starting from such apt consideration by Latour and Yaneva, this essay reflects on the issues that the introduction of movement and of time as strategic components of a design project involves, particularly within an Italian context. The move away from the binding duality of text and context requires an overcoming of the separation between objects and subjects that is substantial to a traditional determinist and authorial approach to the project: this is only possible through the proposition of a different dialogical and argumentative process and, consequently, a fundamental change in the role of the designer. This perspective finds a few premises within Italian discourse in the course of the 20th Century as regards three fundamental points: the city and its transformations; the necessary relationship between theory and project; the central question of form. In the conclusive remarks of the paper I propose an interpretation of form not as final solution but, as tentative form, as indispensable empowerment tool for the various actors involved
Supersymmetric Electroweak Renormalization of the Z-Width in the MSSM (I)
Within the framework of the MSSM, we compute the complete set of electroweak
one-loop supersymmetric quantum effects on the width of the
-boson in the on-shell renormalization scheme. Numerical analyses of the
corrections to the various partial widths into leptons and quarks are
presented. On general grounds, the average size of the electroweak SUSY
corrections to may well saturate the level of the present
theoretical uncertainties, even if considering the full supersymmetric spectrum
lying in the neighbourhood of the unaccessible LEP 200 range. Remarkably
enough, for the present values of the top quark mass, the electroweak SUSY
effects could be, globally, very close or even bigger than the electroweak SM
corrections, but opposite in sign. Therefore, in the absence of theoretical
errors, there are large regions of parameter space where one could find that,
effectively, the electroweak SM corrections are ``missing'', or even having the
``wrong'' sign. This should be helpful in discriminating between the SM and the
MSSM. However, an accurate prediction of the electroweak quantum effects on
will only be possible, if and are pinned down
in the future with enough precision.Comment: 17 p. in LaTeX. Preprint UAB-FT-343. Error in figure caption #3
corrected. Results unchange
Cosmic Flows on 100 Mpc/h Scales: Standardized Minimum Variance Bulk Flow, Shear and Octupole Moments
The low order moments, such as the bulk flow and shear, of the large scale
peculiar velocity field are sensitive probes of the matter density fluctuations
on very large scales. In practice, however, peculiar velocity surveys are
usually sparse and noisy, which can lead to the aliasing of small scale power
into what is meant to be a probe of the largest scales. Previously, we
developed an optimal ``minimum variance'' (MV) weighting scheme, designed to
overcome this problem by minimizing the difference between the measured bulk
flow (BF) and that which would be measured by an ideal survey. Here we extend
this MV analysis to include the shear and octupole moments, which are designed
to have almost no correlations between them so that they are virtually
orthogonal. We apply this MV analysis to a compilation of all major peculiar
velocity surveys, consisting of 4536 measurements. Our estimate of the BF on
scales of ~ 100 Mpc/h has a magnitude of |v|= 416 +/- 78 km/s towards Galactic
l = 282 degree +/- 11 degree and b = 6 degree +/- 6 degree. This result is in
disagreement with LCDM with WMAP5 cosmological parameters at a high confidence
level, but is in good agreement with our previous MV result without an
orthogonality constraint, showing that the shear and octupole moments did not
contaminate the previous BF measurement. The shear and octupole moments are
consistent with WMAP5 power spectrum, although the measurement noise is larger
for these moments than for the BF. The relatively low shear moments suggest
that the sources responsible for the BF are at large distances.Comment: 13 Pages, 7 figures, 4 tables. Some changes to reflect the published
versio
Statistical properties of exoplanets II. Metallicity, orbital parameters, and space velocities
In this article we present a detailed spectroscopic analysis of more than 50
extra-solar planet host stars. Stellar atmospheric parameters and metallicities
are derived using high resolution and high S/N spectra. The spectroscopy
results, added to the previous studies, imply that we have access to a large
and uniform sample of metallicities for about 80 planet hosts stars. We make
use of this sample to confirm the metal-rich nature of stars with planets, and
to show that the planetary frequency is rising as a function of the [Fe/H].
Furthermore, the source of this high metallicity is shown to have most probably
an ``primordial'' source, confirming previous results. The comparison of the
orbital properties (period and eccentricity) and minimum masses of the planets
with the stellar properties also reveal some emerging but still not significant
trends. These are discussed and some explanations are proposed. Finally, we
show that the planet host stars included in the CORALIE survey have similar
kinematical properties as the whole CORALIE volume-limited planet search
sample. Planet hosts simply seem to occupy the metal-rich envelope of this
latter population.Comment: 15 pages, 10 (eps) figures, Astronomy & Astrophysics, in pres
The GAPS Programme with HARPS-N@TNG VI: The Curious Case of TrES-4b
We revisit the TrES-4 system parameters based on high-precision HARPS-N
radial-velocity measurements and new photometric light curves. A combined
spectroscopic and photometric analysis allows us to determine a spectroscopic
orbit with an amplitude m s. The derived mass of TrES-4b is
found to be , significantly lower than
previously reported. Combined with the large radius () inferred from our analysis, TrES-4b becomes
the second-lowest density transiting hot Jupiter known. We discuss several
scenarios to explain the puzzling discrepancy in the mass of TrES-4b in the
context of the exotic class of highly inflated transiting giant planets.Comment: 5 pages, 4 figures, Letter accepted for publication in Astronomy and
Astrophysic
Observation of the full 12-hour-long transit of the exoplanet HD80606b. Warm-Spitzer photometry and SOPHIE spectroscopy
We present new observations of a transit of the 111-day-period exoplanet
HD80606b. Using the Spitzer Space Telescope and its IRAC camera on the
post-cryogenic mission, we performed a 19-hour-long photometric observation of
HD80606 that covers the full transit of 13-14 January 2010. We complement this
photometric data by new spectroscopic observations that we simultaneously
performed with SOPHIE at Haute-Provence Observatory. This provides radial
velocity measurements of the first half of the transit that was previously
uncovered with spectroscopy. This new data set allows the parameters of this
singular planetary system to be significantly refined. We obtained a
planet-to-star radius ratio R_p/R_* = 0.1001 +/- 0.0006 that is slightly lower
than the one measured from previous ground observations. We detected a feature
in the Spitzer light curve that could be due to a stellar spot. We also found a
transit timing about 20 minutes earlier than the ephemeris prediction; this
could be caused by actual TTVs due to an additional body in the system or by
underestimated systematic uncertainties. The sky-projected angle between the
spin-axis of HD80606 and the normal to the planetary orbital plane is found to
be lambda = 42 +/- 8 degrees thanks to the fit of the Rossiter-McLaughlin
anomaly. This allows scenarios with aligned spin-orbit to be definitively
rejected. Over the twenty planetary systems with measured spin-orbit angles, a
few of them are misaligned; this is probably the signature of two different
evolution scenarios for misaligned and aligned systems, depending if they
experienced or not gravitational interaction with a third body. As in the case
of HD80606b, most of the planetary systems including a massive planet are
tilted; this could be the signature of a separate evolution scenario for
massive planets in comparison with Jupiter-mass planets.Comment: 14 pages, 9 figures, 2 tables, accepted for publication in A&
The GAPS programme with HARPS-N@TNG IV: A planetary system around XO-2S
We performed an intensive radial velocity monitoring of XO-2S, the wide
companion of the transiting planet-host XO-2N, using HARPS-N at TNG in the
framework of the GAPS programme. The radial velocity measurements indicate the
presence of a new planetary system formed by a planet that is slightly more
massive than Jupiter at 0.48 au and a Saturn-mass planet at 0.13 au. Both
planetary orbits are moderately eccentric and were found to be dynamically
stable. There are also indications of a long-term trend in the radial
velocities. This is the first confirmed case of a wide binary whose components
both host planets, one of which is transiting, which makes the XO-2 system a
unique laboratory for understanding the diversity of planetary systems.Comment: 7 pages, 3 figures, accepted on A&A Lette
The Values of and Derived from the Non-Observation of Electroweak Radiative Corrections at LEP: Global Fit
A set of equations representing the mass ratio and various observables
of decays in terms of , , ,
, , , and (all
other fermion masses being neglected) are compared with the latest data of the
four LEP detectors, which at the level of one standard deviation coincide with
their Born values. Our global fit gives: , where the central values
correspond to GeV, the first errors are statistical and the second
ones represent shifts of the central values corresponding to
GeV() and 60 GeV(). The predicted mass of the top is smaller than in the
recent fits by 4 GeV. The {\it predicted} values of and the LEP
observables, based on the fitted values of and , show a
weak dependence on and differ by several {\it predicted} standard
deviations from the corresponding Born values. The uncertainties of the
predicted values and their deviations from the corresponding Born values
determine the experimental accuracy required to observe electroweak radiative
corrections.Comment: LaTex, 15 pages (including 3 figures as EPS files at the end
Transiting exoplanets from the CoRoT space mission IX. CoRoT-6b: a transiting `hot Jupiter' planet in an 8.9d orbit around a low-metallicity star
The CoRoT satellite exoplanetary team announces its sixth transiting planet
in this paper. We describe and discuss the satellite observations as well as
the complementary ground-based observations - photometric and spectroscopic -
carried out to assess the planetary nature of the object and determine its
specific physical parameters. The discovery reported here is a `hot Jupiter'
planet in an 8.9d orbit, 18 stellar radii, or 0.08 AU, away from its primary
star, which is a solar-type star (F9V) with an estimated age of 3.0 Gyr. The
planet mass is close to 3 times that of Jupiter. The star has a metallicity of
0.2 dex lower than the Sun, and a relatively high Li abundance. While
thelightcurveindicatesamuchhigherlevelof activity than, e.g., the Sun, there is
no sign of activity spectroscopically in e.g., the [Ca ] H&K lines
On the Eccentricity Distribution of Short-Period Single-Planet Systems
We apply standard Markov chain Monte Carlo (MCMC) analysis techniques for 50
short- period, single-planet systems discovered with radial velocity technique.
We develop a new method for accessing the significance of a non-zero orbital
eccentricity, namely {\Gamma} analysis, which combines frequentist bootstrap
approach with Bayesian analysis of each simulated data set. We find the
eccentricity estimations from {\Gamma} analysis are generally consistent with
results from both standard MCMC analysis and previous references. The {\Gamma}
method is particular useful for assessing the significance of small
eccentricities. Our results suggest that the current sample size is
insufficient to draw robust conclusions about the roles of tidal interaction
and perturbations in shaping the eccentricity distribution of short-period
single-planet systems. We use a Bayesian population analysis to show that a
mixture of analytical distributions is a good approximation of the underlying
eccentricity distribution. For short-period planets, we find the most probable
values of parameters in the analytical functions given the observed
eccentricities. These analytical functions can be used in theoretical
investigations or as priors for the eccentricity distribution when analyzing
short-period planets. As the measurement precision improves and sample size
increases, the method can be applied to more complex parametrizations for the
underlying distribution of eccentricity for extrasolar planetary systems.Comment: 13 pages, 11 figures, 4 tables, accepted by MNRA
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