319 research outputs found
On the Construction of Quintessential Inflation Models
Attention has been recently drawn towards models in which inflation and
quintessence schemes are unified. In such `quintessential inflation' models, a
unique scalar field is required to play both the role of the inflaton and of
the late-time dynamical cosmological constant. We address the issue of the
initial conditions for quintessence in this context and find that, in the two
explicit examples provided, inflation can uniquely fix them to be in the
allowed range for a present day tracking.Comment: LaTex; 14 pages, 1 figure. V2: improved version, some points
clarifie
Breakthroughs on the Dark Matter Issue
Last year observations had a profound impact on our views on the amount and
nature of dark matter in the universe. We give a brief review of the recent
history of dark matter models beyond the pure cold dark matter universe. In
view of the most recent cosmological data, we then go on to discuss models with
a positive cosmological constant. Finally we explicitly analyse a class of
particle physics models for a dynamical cosmological component with negative
pressure (``quintessence''), in the context of supersymmetric theories.Comment: 13 pages; Talk given by Antonio Masiero at the 8^th International
Workshop on Neutrino Telescopes, 23-26 Feb. 1999, Venice, Italy. To be
published in the Proceeding
Dark Energy and the Dark Matter relic abundance
Two mechanisms by which the Quintessence scalar could enhance the relic
abundance of dark matter particles are discussed. This effect can have an
impact on supersymmetric candidates for dark matter.Comment: 6 pages; to appear in the Proceedings of "Phi in the Sky - the quest
for cosmological scalar fields", 8-10 July 2004, Porto (PT
A machine learning approach for stride speed estimation based on a head-mounted IMU
Walking speed in real-life conditions is typically
estimated through wearable inertial sensors mounted on waist,
lower limbs, or wrists. Very recently, head-mounted inertial
sensors are emerging for gait assessment. The present study
explores the feasibility of measuring the stride speed with a
head-mounted inertial sensor in both laboratory and real-world
settings. The developed algorithm exploits a Temporal
Convolutional Network for the detection of the gait events and a
Gaussian Process Regression for the stride speed estimation.
The experimental evaluation was carried out on healthy young
participants during both standardised indoor and real-world
walking trials. For indoor trials, errors were smaller than
previous studies (0.05 m/s). As expected, errors increased at
lower speed regimes due to a reduced signals amplitude. During
2.5-hours real-world evaluation, errors were slightly larger but
acceptable (0.1 m/s). Reported results are encouraging and show
the feasibility of estimating gait speed with a single head-worn
inertial sensor
Quintessence, Supersymmetry and Inflation
Recent data point in the direction of a dominated universe. We
briefly review ``Quintessence'' as a model for a dynamical cosmological term
and analyse the role of Susy QCD as a possible particle physics candidate. The
multiscalar content of the theory is fully taken into account and interaction
with other cosmological fields is discussed. Finally, the possibility of
constructing a unified scheme for quintessence and inflation is mentioned.Comment: 5 LaTex pages, no figures; Talk given at the International Workshop
on "Particles in Astrophysics and Cosmology: from Theory to Observations"
(Valencia99), 3-8 May 1999, Valencia, Spain. To appear on Nucl. Phys. B,
Proc. Supp
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