8,654 research outputs found
QED in strong, finite-flux magnetic fields
Lower bounds are placed on the fermionic determinants of Euclidean quantum
electrodynamics in two and four dimensions in the presence of a smooth,
finite-flux, static, unidirectional magnetic field , where
or , and is a point in the xy-plane.Comment: 10 pages, postscript (in uuencoded compressed tar file
Appropriate Loads for Peak-Power During Resisted Sprinting on a Non-Motorized Treadmill
The purpose of this study was to determine the load which allows the highest peak power for resisted sprinting on a non-motorized treadmill and to determine if other variables are related to individual differences. Thirty college students were tested for vertical jump, vertical jump peak and mean power, 10 m sprint, 20 m sprint, leg press 1 RM, leg press 1 RM relative to body weight, leg press 1 RM relative to lean body mass, leg press 1 RM power, and leg press power at 80% of 1 RM. Participants performed eight resisted sprints on a non-motorized treadmill, with increasing relative loads expressed as percent of body weight. Sprint peak power was measured for each load. Pearson correlations were used to determine if relationships between the sprint peak power load and the other variables were significant. The sprint peak power load had a mode of 35% with 73% of all participants having a relative sprint peak power load between 25-35%. Significant correlations occurred between sprint peak power load and body weight, lean body mass, vertical jump peak and mean power, leg press 1 RM, leg press 1 RM relative to lean body mass, leg press 1 RM power, and leg press power at 80% of 1 RM (r = 0.44, 0.43, 0.39, 0.37, 0.47, 0.39, 0.46, and 0.47, respectively). Larger, stronger, more powerful athletes produced peak power at a higher relative load during resisted sprinting on a nonmotorized treadmill
Low Energy Leptogenesis in Left-Right Symmetric Models
We propose a new mechanism for baryogenesis. We study the effective potential
of left-right extension of the standard model and show that there can be a
first order phase transition at the left-right symmetry breaking and hence
symmetry breaking scale, which is around TeV in our scenario. As a
result, although violating interactions are in equilibrium at this
scale, enough asymmetry may be generated. This asymmetry is
then converted to baryon asymmetry during the anomalous electroweak process. If
right handed gauge bosons are seen in the TeV scale, then we argue that this
will be the only consistent mechanism to generate baryon asymmetry of the
universe.Comment: 16 pages (Latex file) - 1 postscript figure appende
The abundance of high-redshift objects as a probe of non-Gaussian initial conditions
The observed abundance of high-redshift galaxies and clusters contains
precious information about the properties of the initial perturbations. We
present a method to compute analytically the number density of objects as a
function of mass and redshift for a range of physically motivated non-Gaussian
models. In these models the non-Gaussianity can be dialed from zero and is
assumed to be small. We compute the probability density function for the
smoothed dark matter density field and we extend the Press and Schechter
approach to mildly non-Gaussian density fields. The abundance of high-redshift
objects can be directly related to the non-Gaussianity parameter and thus to
the physical processes that generated deviations from the Gaussian behaviour.
Even a skewness parameter of order 0.1 implies a dramatic change in the
predicted abundance of z\gap 1 objects. Observations from NGST and X-ray
satellites (XMM) can be used to accurately measure the amount of
non-Gaussianity in the primordial density field.Comment: Minor changes to match the accepted ApJ version (ApJ, 539
Fermionic Determinant of the Massive Schwinger Model
A representation for the fermionic determinant of the massive Schwinger
model, or , is obtained that makes a clean separation between the
Schwinger model and its massive counterpart. From this it is shown that the
index theorem for follows from gauge invariance, that the Schwinger
model's contribution to the determinant is canceled in the weak field limit,
and that the determinant vanishes when the field strength is sufficiently
strong to form a zero-energy bound state
Absence of correlation between built-in electric dipole moment and quantum Stark effect in InAs/GaAs self-assembled quantum dots
We report significant deviations from the usual quadratic dependence of the
ground state interband transition energy on applied electric fields in
InAs/GaAs self-assembled quantum dots. In particular, we show that conventional
second-order perturbation theory fails to correctly describe the Stark shift
for electric field below kV/cm in high dots. Eight-band calculations demonstrate this effect is predominantly due to
the three-dimensional strain field distribution which for various dot shapes
and stoichiometric compositions drastically affects the hole ground state. Our
conclusions are supported by two independent experiments.Comment: 4 pages, 4 figure
Culture change in a professional sports team: Shaping environmental contexts and regulating power
Although high performing cultures are crucial for the enduring success of professional sport performance teams, theoretical and practical understanding of how they are established and sustained is lacking. To develop knowledge in this area, a case study was undertaken to examine the key mechanisms and processes of a successful culture change programme at English Rugby Unionâs Leeds Carnegie. Exploring the change process from a 360 degree perspective, semi-structured interviews were conducted with team management, one specialist coach, six players, and the CEO. Analysed and explained through decentred theory, results revealed that culture change was effectively facilitated by team management: a) subtly and covertly shaping the physical, structural, and psychosocial context in which support staff and players made performance-impacting choices, and b) regulating the âto and froâ of power which characterises professional sport performance teams. Decentred theory is also supported as an effective framework for culture change study
Anomalous quantum confined Stark effects in stacked InAs/GaAs self-assembled quantum dots
Vertically stacked and coupled InAs/GaAs self-assembled quantum dots (SADs)
are predicted to exhibit a strong non-parabolic dependence of the interband
transition energy on the electric field, which is not encountered in single SAD
structures nor in other types of quantum structures. Our study based on an
eight-band strain-dependent Hamiltonian indicates that
this anomalous quantum confined Stark effect is caused by the three-dimensional
strain field distribution which influences drastically the hole states in the
stacked SAD structures.Comment: 4 pages, 4 figure
Flareâgenerated shock evolution and geomagnetic storms during the âHalloween 2003 epochâ: 29 October to 2 November
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95151/1/jgra17876.pd
Kinetic and Kinematic Characteristics of Proficient and Non-Proficient 2-Point and 3-Point Basketball Shooters
The purpose of this study was to examine kinetic and kinematic characteristics of various types of 2-point and 3-point basketball shooting approaches and determine which variables have the greatest contribution in discriminating proficient (PRO) from non-proficient (N-PRO) shooters. While standing on a force plate, twenty-nine recreationally active males performed a total of 1740 shots by utilizing stationary and step-in shooting approaches. Two high-definition cameras were used to simultaneously capture kinematic parameters of shooting motions. The type of shooting approach showed as a non-influential factor. During the preparatory phase of the shooting motion, PRO 2-point shooters demonstrated higher elbow and basketball height placements, greater flexion in the shoulder and elbow joints while attaining greater release and entry ball angles during the release phase. PRO 3-point shooters demonstrated greater elbow flexion, higher basketball placement, and less hip flexion during the preparatory phase while attaining greater heel, release, and trajectory heights during the release phase. When entered into a full-model discriminant function analysis, elbow angle, elbow height, and release angle variables correctly classified PRO from N-PRO 2-point shooters in 62.1% of cases and hip angle, heel height, and elbow angle variables correctly classified PRO from N-PRO 3-point shooters in 81.6% of cases
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