1,939 research outputs found
Early Dark Energy Cosmologies
We propose a novel parameterization of the dark energy density. It is
particularly well suited to describe a non-negligible contribution of dark
energy at early times and contains only three parameters, which are all
physically meaningful: the fractional dark energy density today, the equation
of state today and the fractional dark energy density at early times. As we
parameterize Omega_d(a) directly instead of the equation of state, we can give
analytic expressions for the Hubble parameter, the conformal horizon today and
at last scattering, the sound horizon at last scattering, the acoustic scale as
well as the luminosity distance. For an equation of state today w_0 < -1, our
model crosses the cosmological constant boundary. We perform numerical studies
to constrain the parameters of our model by using Cosmic Microwave Background,
Large Scale Structure and Supernovae Ia data. At 95% confidence, we find that
the fractional dark energy density at early times Omega_early < 0.06. This
bound tightens considerably to Omega_early < 0.04 when the latest Boomerang
data is included. We find that both the gold sample of Riess et. al. and the
SNLS data by Astier et. al. when combined with CMB and LSS data mildly prefer
w_0 < -1, but are well compatible with a cosmological constant.Comment: 6 pages, 3 figures; references added, matches published versio
The Positional Match Running Performance of Elite Gaelic Football.
There is currently limited information available on match running performance in Gaelic football. The objective of the current study was to report on the match running profile of elite male Gaelic football and assess positional running performance. In this observational study 50 elite male Gaelic football players wore 4-Hz GPS units (VXsports, New Zealand) across 30 competitive games with a total of 212 full game data sets collected. Activity was classed according to total distance, high speed distance (≥17 km.h), sprint distance (≥22 km.h), mean velocity (km.h), peak velocity (km.h) and number of accelerations. The average match distance was 8160 ± 1482 m, reflective of a relative distance of 116 ± 21 m.min, with 1731 ± 659 m covered at high speed which is reflective of a relative high speed distance of 25 ± 9 m.min. The observed sprint distance was 445 ± 169 m distributed across 44 sprint actions. The peak velocity was 30.3 ± 1.8 km.h with a mean velocity of 6.5 ± 1.2 km.h. Players completed 184 ± 40 accelerations which represent 2.6 ± 0.5 a.min. There were significant differences between positional groups for both total running distance, high speed running distance and sprint distance, with midfielders covering more total and high speed running distance, compared to other positions (p<0.001). There was a reduction in high speed and sprint distance between the first and second half (p<0.001). Reductions in running performance were position dependant with the middle three positions experiencing the highest decrement in performance. The current study is the first to communicate a detailed description of match running performance during competitive elite Gaelic football match play
High chronic training loads and exposure to bouts of maximal velocity running reduce injury risk in elite Gaelic football.
OBJECTIVES: To examine the relationship between chronic training loads, number of exposures to maximal velocity, the distance covered at maximal velocity, percentage of maximal velocity in training and match-play and subsequent injury risk in elite Gaelic footballers. DESIGN: Prospective cohort design. METHODS: Thirty-seven elite Gaelic footballers from one elite squad were involved in a one-season study. Training and game loads (session-RPE multiplied by duration in min) were recorded in conjunction with external match and training loads (using global positioning system technology) to measure the distance covered at maximal velocity, relative maximal velocity and the number of player exposures to maximal velocity across weekly periods during the season. Lower limb injuries were also recorded. Training load and GPS data were modelled against injury data using logistic regression. Odds ratios (OR) were calculated based on chronic training load status, relative maximal velocity and number of exposures to maximal velocity with these reported against the lowest reference group for these variables. RESULTS: Players who produced over 95% maximal velocity on at least one occasion within training environments had lower risk of injury compared to the reference group of 85% maximal velocity on at least one occasion (OR: 0.12, p=0.001). Higher chronic training loads (≥4750AU) allowed players to tolerate increased distances (between 90 to 120m) and exposures to maximal velocity (between 10 to 15 exposures), with these exposures having a protective effect compared to lower exposures (OR: 0.22 p=0.026) and distance (OR=0.23, p=0.055). CONCLUSIONS: Players who had higher chronic training loads (≥4750AU) tolerated increased distances and exposures to maximal velocity when compared to players exposed to low chronic training loads (≤4750AU). Under- and over-exposure of players to maximal velocity events (represented by a U-shaped curve) increased the risk of injury
Codes and Supersymmetry in One Dimension
Adinkras are diagrams that describe many useful supermultiplets in D=1
dimensions. We show that the topology of the Adinkra is uniquely determined by
a doubly even code. Conversely, every doubly even code produces a possible
topology of an Adinkra. A computation of doubly even codes results in an
enumeration of these Adinkra topologies up to N=28, and for minimal
supermultiplets, up to N=32.Comment: 48 pages, a new version that combines arXiv:0811.3410 and parts of
arXiv:0806.0050, for submission for publicatio
Observational constraints on the dark energy density evolution
We constrain the evolution of the dark energy density from Cosmic Microwave
Background, Large Scale Structure and Supernovae Ia measurements. While
Supernovae Ia are most sensitive to the equation of state of dark energy
today, the Cosmic Microwave Background and Large Scale Structure data best
constrains the dark energy evolution at earlier times. For the parametrization
used in our models, we find and the dark energy fraction at very
high redshift at 95 per cent confidence level.Comment: 5 pages, 10 figure
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