6,276 research outputs found
Rare tau Decays in R-parity Violating Supersymmetry
We constrain, from rare tau decays, several combinations of and
type couplings coming from Supersymmetry without R-parity. The
processes that we consider are tau --> l M, tau --> l_i l_j l_k, and tau --> l
gamma, where l stands for either e or mu, and M is the generic symbol for a
meson. We update several existing bounds, and provide a few new ones too.Comment: 12 pages, no figure
Electromagnetic Zero Point Field as Active Energy Source in the Intergalactic Medium
For over twenty years the possibility that the electromagnetic zero point
field (ZPF) may actively accelerate electromagnetically interacting particles
in regions of extremely low particle density (as those extant in intergalactic
space (IGS) with n < 1 particle/m^3 has been studied and analyzed. This
energizing phenomenon has been one of the few contenders for acceleration of
cosmic rays (CR), particularly at ultrahigh energies. The recent finding by the
AGASA collaboration (Phys. Rev. Lett., 81, 1163, 1998) that the CR energy
spectrum does not display any signs of the Greisen-Zatsepin-Kuzmin cut-off
(that should be present if these CR particles were indeed generated in
localized ultrahigh energies CR sources, as e.g., quasars and other highly
active galactic nuclei), may indicate the need for an acceleration mechanism
that is distributed throughout IGS as is the case with the ZPF. Other
unexplained phenomena that receive an explanation from this mechanism are the
generation of X-ray and gamma-ray backgrounds and the existence of Cosmic
Voids. However recently, a statistical mechanics kind of challenge to the
classical (not the quantum) version of the zero-point acceleration mechanism
has been posed (de la Pena and Cetto, The Quantum Dice, 1996). Here we briefly
examine the consequences of this challenge and a prospective resolution.Comment: 7 pages, no figure
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"Sub-Hertz" Dielectric Spectroscopy
Dielectric spectroscopy measurements below 1 Hz are often dominated by âconduction-likeâ effects. For this reason, they often appear to be dismissed as being of little interest. In this paper two âsub-hertzâ responses are considered that give insights into the insulating sys-tems concerned. The first system is that of cross-linked polyethylene, taken from a power cable system. Measurements at temperatures between 60°C and close to melting at 100°C show a change in characteristic from a percolation process to a âtrueâ DC conduction at close to the melting point. Using DC conductivities, it appears to be possible to show whether the cable has been subjected to thermo-electric ageing. This might give insights into where the conduction and hence the ageing in the XLPE is occurring. The second system is an epoxy composite. By considering the sub-hertz response, it is possible to demonstrate the effect of the interface between the filler and the epoxy matrix. In this system, ageing, resulting in delamination between the glass fiber filler and the epoxy, is clearly detected by sub-hertz dielectric spectroscopy. This process is likely to be facilitated by the presence of water, which is known to lead to mechanical failure in such systems, and which can also be detected by "sub-hertz" dielectric spectroscopy. The implications for nano-dielectrics are then briefly considered
American Indian Oral Traditions and their Relation to the Paleo-SETI Community
Paleo-SETI is a social discourse which has seen rapidly increasing popularity since its conception in the late 1800âs. Its main focus is identifying evidence of intelligent extraterrestrial occupation of Earth in its distant past. The Paleo-SETI community commonly draws upon ancient oral and religious traditions, reinterpreting them as containing evidence of alien visitors. Commonalities such as âthe floodâ and âcyclical timeâ are also identified. Paleo-SETI thought also incorporates evidence of Supra human knowledge, anomalous archeological sites and seemingly unexplainabe advanced technology. This paper examined six American Indian Oral traditions and their relation to the evolving discourses in the Paleo-SETI community. An attempt is made to determine if ancient Oral Traditions do, in fact, lend themselves to an âalienâ reinterpretation. Common themes among the movement are discussed in terms of these six traditions. Also included is an examination of these key themes in Paleo-SETI thought on a global scale. The final section includes a brief investigation of possible psychological, spiritual and philosophical motivations driving the popular Ancient Astronaut Theory.
Faculty mentor: Sean Dale
Will mobile video become the killer application for 3G? - an empirical model for media convergence
Mobile carriers have continually rolled out 3G mobile video applications to increase their revenue and profits. The presumption is that video is superior to the already successful SMS, ringtones, and pictures, and can create greater value to users. However, recent market surveys revealed contradicting results. Motivated by this discrepancy, we propose in this paper a parsimonious model for user acceptance of mobile entertainment as digital convergence. Integrating research on Information Systems, Flow, and Media Psychology, we take a unique approach to user acceptance of digital convergence - platform migration. Our key proposition is that the interaction between media types and the platform-specific constraints is the key determinant of user evaluation. Particularly, users' involvement in the media is determined by both the entertaining time span on the original platform and the attentional constraint of the new platform. The mismatch between the two spans can result in lower level involvement, which in turn cause no or even negative user emotional responses. The model was tested with empirical data. We discuss the theoretical contributions, strategic and design implications, and future research directions derived from this theoretical framewor
A new orthogonalization procedure with an extremal property
Various methods of constructing an orthonomal set out of a given set of
linearly independent vectors are discussed. Particular attention is paid to the
Gram-Schmidt and the Schweinler-Wigner orthogonalization procedures. A new
orthogonalization procedure which, like the Schweinler- Wigner procedure, is
democratic and is endowed with an extremal property is suggested.Comment: 7 pages, latex, no figures, To appear in J. Phys
Spacetime Defects: von K\'arm\'an vortex street like configurations
A special arrangement of spinning strings with dislocations similar to a von
K\'arm\'an vortex street is studied. We numerically solve the geodesic
equations for the special case of a test particle moving along twoinfinite rows
of pure dislocations and also discuss the case of pure spinning defects.Comment: 9 pages, 2figures, CQG in pres
Quantum magnetism with multicomponent polar molecules in an optical lattice
We consider bosonic dipolar molecules in an optical lattice prepared in a
mixture of different rotational states. The 1/r^3 interaction between molecules
for this system is produced by exchanging a quantum of angular momentum between
two molecules. We show that the Mott states of such systems have a large
variety of non-trivial spin orderings including a state with ordering wave
vector that can be changed by tilting the lattice. As the Mott insulating phase
is melted, we also describe several exotic superfluid phases that will occur
Dynamical Symmetry Breaking in Planar QED
We investigate (2+1)-dimensional QED coupled with Dirac fermions both at zero
and finite temperature. We discuss in details two-components (P-odd) and
four-components (P-even) fermion fields. We focus on P-odd and P-even Dirac
fermions in presence of an external constant magnetic field. In the spontaneous
generation of the magnetic condensate survives even at infinite temperature. We
also discuss the spontaneous generation of fermion mass in presence of an
external magnetic field.Comment: 34 pages, 8 postscript figures, final version to appear on J. Phys.
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