20,284 research outputs found
Primordial Lepton Family Asymmtries in Seesaw Model
In leptogenesis scenario, the decays of heavy Majorana neutrinos generate
lepton family asymmetries, and . They are sensitive to
CP violating phases in seesaw models. The time evolution of the lepton family
asymmetries are derived by solving Boltzmann equations. By taking a minimal
seesaw model, we show how each family asymmetry varies with a CP violating
phase. For instance, we find the case that the lepton asymmetry is dominated by
or depending on the choice of the CP violating phase. We
also find the case that the signs of lepton family asymmetries and
are opposite each other. Their absolute values can be larger than
the total lepton asymmetry and the baryon asymmetry may result from the
cancellation of the lepton family asymmetries.Comment: 26 pages, 8 figures, ptp.styl
Oscillating p-Branes
Coset methods are used to construct the action describing the dynamics
associated with the spontaneous breaking of the Poincare symmetries of D
dimensional space-time due to the embedding of a p-brane with codimension
N=D-p-1. The resulting world volume action is an ISO(1,p+N) invariant
generalization of the Nambu-Goto action in d=p+1 dimensional space-time.
Analogous results are obtained for an AdS p-brane with codimension N embedded
in D dimensional AdS space, yielding an SO(2,p+N) invariant version of the
Nambu-Goto action in d=p+1 dimensional space-time. Attention is focused on a
supersymmetric extension of the D=6 Minkowski space case with an embedded p=3
brane; a particular realization of which is provided by a non-BPS vortex. Here
both the Nambu-Goto-Akulov-Volkov action and its dual tensor form are
presented.Comment: 25 pages, no figure
Higgs Decays and Brane Gravi-vectors
Higgs boson decays in flexible brane world models with stable, massive
gravi-vectors are considered. Such vectors couple bilinearly to the Standard
Model fields through either the Standard Model energy-momentum tensor, the weak
hypercharge field strength or the Higgs scalar. The role of the coupling
involving the extrinsic curvature is highlighted. It is found that within the
presently allowed parameter space, the decay rate of the Higgs into two
gravi-vectors (which would appear as an invisible Higgs decay) can be
comparable to the rate for any of the Standard Model decay modes.Comment: 5 pages, 11 figures, revte
Brane Vector Phenomenology
Local oscillations of the brane world are manifested as masssive vector
fields. Their coupling to the Standard Model can be obtained using the method
of nonlinear realizations of the spontaneously broken higher dimensional
space-time symmetries, and to an extent, are model independent.
Phenomenological limits on these vector field parameters are obtained using LEP
collider data and dark matter constraints.Comment: 3 pages, 2 figures, late
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Investigation of the Viscoelastic Effect on Optical- Fiber Sensing and Its Solution for 3D-Printed Sensor Packages
Viscoelasticity is an effect seen in a wide range of materials and it affects the reliability of static measurements made using Fiber Bragg Grating-based sensors, because either the target structure, the adhesive used, or the fiber itself could be viscoelastic. The effect of viscoelasticity on FBG-based sensing has been comprehensively researched through theoretical analysis and simulation using a finite-element approach and a further data processing method to reconstruct the graphical data has been developed. An integrated sensor package comprising of an FBG-based sensor in a polymer host and manufactured by using three-dimensional printing was investigated and examined through tensile testing to validate the approach. The application of the 3D-printed FBG-based sensor package, coupled to the data process method has been explored to monitor the height of a railway pantograph, a critical measurement requirement to monitor elongation, employing a method that can be used in the presence of electromagnetic interference. The results show that the effect of viscoelasticity can be effectively eliminated, and the graphical system response allows results that are sufficiently precise for field use to be generated
Sub-Nanosecond Time of Flight on Commercial Wi-Fi Cards
Time-of-flight, i.e., the time incurred by a signal to travel from
transmitter to receiver, is perhaps the most intuitive way to measure distances
using wireless signals. It is used in major positioning systems such as GPS,
RADAR, and SONAR. However, attempts at using time-of-flight for indoor
localization have failed to deliver acceptable accuracy due to fundamental
limitations in measuring time on Wi-Fi and other RF consumer technologies.
While the research community has developed alternatives for RF-based indoor
localization that do not require time-of-flight, those approaches have their
own limitations that hamper their use in practice. In particular, many existing
approaches need receivers with large antenna arrays while commercial Wi-Fi
nodes have two or three antennas. Other systems require fingerprinting the
environment to create signal maps. More fundamentally, none of these methods
support indoor positioning between a pair of Wi-Fi devices
without~third~party~support.
In this paper, we present a set of algorithms that measure the time-of-flight
to sub-nanosecond accuracy on commercial Wi-Fi cards. We implement these
algorithms and demonstrate a system that achieves accurate device-to-device
localization, i.e. enables a pair of Wi-Fi devices to locate each other without
any support from the infrastructure, not even the location of the access
points.Comment: 14 page
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