3,035 research outputs found
Testing the distance duality relation with present and future data
The assumptions that "light propagates along null geodesics of the spacetime
metric" and "the number of photons is conserved along the light path" lead to
the distance duality relation (DDR), ,
with and the luminosity and angular diameter distances to a
source at redshift . In order to test the DDR, we follow the usual strategy
comparing the angular diameter distances of a set of clusters, inferred from X
- ray and radio data, with the luminosity distance at the same cluster redshift
using the local regression technique to estimate from Type Ia
Supernovae (SNeIa) Hubble diagram. In order to both strengthen the constraints
on the DDR and get rid of the systematics related to the unknown cluster
geometry, we also investigate the possibility to use Baryon Acoustic
Oscillations (BAO) to infer from future BAO surveys. As a test case,
we consider the proposed Euclid mission investigating the precision can be
afforded on from the expected SNeIa and BAO data. We find that the
combination of BAO and the local regression coupled allows to reduce the errors
on by a factor two if one is forced and future data are used. On the other hand, although the
statistical error on is not significantly reduced, the constraints on
this quantity will be nevertheless ameliorated thanks to the reduce impact of
systematics.Comment: 10 pages, 1 figure, 1 table, accepted for publication on Physical
Review
Selfish Dark Matter
We present a mechanism where a particle asymmetry in one sector is used to
generate an asymmetry in another sector. The two sectors are not coupled
through particle number violating interactions and are not required to be in
thermal contact with each other. When this mechanism is applied to baryogenesis
in asymmetric dark matter models, we find that the dark matter particles can be
extremely light, e.g. much lighter than an eV, and that in some cases there is
no need to annihilate away the symmetric component of dark matter. We discuss a
concrete realization of the mechanism with signals in direct detection, at the
LHC, at -factories or future beam dump experiments.Comment: 18+5 pages, 2 figures; Journal version: Added references, small
changes to the free-streaming length estimate
Empowering and assisting natural human mobility: The simbiosis walker
This paper presents the complete development of the Simbiosis Smart Walker. The device is equipped with a set of sensor subsystems to acquire user-machine interaction forces and the temporal evolution of user's feet during gait. The authors present an adaptive filtering technique used for the identification and separation of different components found on the human-machine interaction forces. This technique allowed isolating the components related with the navigational commands and developing a Fuzzy logic controller to guide the device. The Smart Walker was clinically validated at the Spinal Cord Injury Hospital of Toledo - Spain, presenting great acceptability by spinal chord injury patients and clinical staf
ESO Imaging Survey VII. Distant Cluster Candidates over 12 square degrees
In this paper the list of candidate clusters identified from the I-band data
of the ESO Imaging Survey (EIS) is completed using the images obtained over a
total area of about 12 square degrees. Together with the data reported earlier
the total I-band coverage of EIS is 17 square degrees, which has yielded a
sample of 252 cluster candidates in the redshift range 0.2 \lsim z \lsim 1.3.
This is the largest optically-selected sample currently available in the
Southern Hemisphere. It is also well distributed in the sky thus providing
targets for a variety of VLT programs nearly year round.Comment: 5 pages, 3 figures, submitted to Astronomy & Astrophysic
Evolutions in undirected travel (satisfaction) during the COVID-19 pandemic
The COVID-19 pandemic illustrated that undirected travel (UT), or trips taken for their own sake, can partly compensate for a reduction in destination-based trips due to governmental regulations. Consequently, UT (in general, but particularly during the pandemic) may be especially satisfying and therefore important to subjective well-being. However, through the course of the pandemic, changes in UT were anticipated as individuals adapted to a ‘new normal’. This research – conducted in Flanders, Belgium – first investigates whether the characteristics of and satisfaction with UT persisted after one year into the pandemic (April 2020 to May 2021) using longitudinal panel data from two waves (n = 332). Results of paired sample t-tests indicate that UT satisfaction increased though duration of trips decreased, and results of the Sign test indicate that the frequency of UT generally decreased. Second, this research investigates characteristics of individuals with different UT behavior. Six profiles of UT behavior were identified based on starting or stopping UT, increasing or decreasing UT, maintaining UT frequency, or not participating in UT. Chi2 tests identified differences among profiles based on wave 1 UT frequency, most recent trip mode, socio-demographic, and household characteristics. Results indicate that participation in UT might motivate future UT, one to three UT trips per week is a maintainable frequency, UT might be important to those with smaller living spaces and those living with children or other adults, and suggest that attention should be paid to mobility equity, including how and for whom systems are planned. These findings are important to understanding the effects of long-term governmental regulations in response to the COVID-19 pandemic on travel behavior, and how investigating UT might help to challenge and reimagine traditional mobility systems post-pandemic
On undirected trips, satisfaction, and well-being: Evidence from Flanders (Belgium)
Despite having the potential to improve subjective well-being, satisfaction with undirected travel, or travel for its own sake (e.g. taking a walk, bike ride, or joy ride), has not yet been empirically investigated. Using mean-comparison and generalized linear regression models, this study analyzes 1579 undirected trips made by 852 respondents to a survey in Flanders, Belgium during the COVID-19 pandemic lockdown (18 March – 4 May 2020). Undirected travel was found to be longer in duration and more satisfying than results from directed trips in previous literature, with an indication that higher levels of physical activity are important to satisfaction. Undirected travel satisfaction was found to have a clear positive relationship to well-being. As these trips are often active and were found to imply a positive utility of travel, understanding them can be important to policy goals regarding health, sustainability, and improving individual well-being
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