312 research outputs found
Strongly Interacting Neutrinos and the Highest Energy Cosmic Rays
Cosmic rays of energies larger than the Greisen-Zatsepin-Kuzmin (GZK) cutoff
may be neutrinos if they acquire strong interactions due to a ``precocious
unification'' of forces. A scenario for this to happen is outlined. There is no
contradiction with precision measurements carried out at LEP and SLAC.
Observable consequences at LHC and future neutrino detectors are discussed.Comment: 9 pages, LaTeX2e, no macros, 2 eps. figures. Uses epsf.te
Optical discrimination between spatial decoherence and thermalization of a massive object
We propose an optical ring interferometer to observe environment-induced
spatial decoherence of massive objects. The object is held in a harmonic trap
and scatters light between degenerate modes of a ring cavity. The output signal
of the interferometer permits to monitor the spatial width of the object's wave
function. It shows oscillations that arise from coherences between energy
eigenstates and that reveal the difference between pure spatial decoherence and
that coinciding with energy transfer and heating. Our method is designed to
work with a wide variety of masses, ranging from the atomic scale to
nano-fabricated structures. We give a thorough discussion of its experimental
feasibility.Comment: 2 figure
Locally Perturbed Random Walks with Unbounded Jumps
In \cite{SzT}, D. Sz\'asz and A. Telcs have shown that for the diffusively
scaled, simple symmetric random walk, weak convergence to the Brownian motion
holds even in the case of local impurities if . The extension of their
result to finite range random walks is straightforward. Here, however, we are
interested in the situation when the random walk has unbounded range.
Concretely we generalize the statement of \cite{SzT} to unbounded random walks
whose jump distribution belongs to the domain of attraction of the normal law.
We do this first: for diffusively scaled random walks on having finite variance; and second: for random walks with distribution
belonging to the non-normal domain of attraction of the normal law. This result
can be applied to random walks with tail behavior analogous to that of the
infinite horizon Lorentz-process; these, in particular, have infinite variance,
and convergence to Brownian motion holds with the superdiffusive scaling.Comment: 16 page
Lepton pairs from thermal mesons
We study the net dielectron production rates from an ensemble of thermal
mesons, using an effective Lagrangian to model their interaction. The coupling
between the electromagnetic and the hadronic sectors is done through the vector
meson dominance approach. For the first time, a complete set of light mesons is
considered. We include contributions from decays of the type
V~(PS)~~PS~(V)~+~, where V is a vector meson and PS is a
pseudoscalar, as well as those from binary reactions PS~+~PS, V~+~V, and
V~+~PS~. Direct decays of the type V~
are included and shown to be important. We find that the dielectron invariant
mass spectrum naturally divides in distinct regions: in the low mass domain the
decays from vector and pseudoscalar mesons form the dominant contribution. The
pion--pion annihilation and direct decays then pick up and form the leading
signal in an invariant mass region that includes the complex
and extends up to the . Above invariant mass ~1~GeV other
two-body reactions take over as the prominent mechanisms for lepton pair
generation. These facts will have quantitative bearing on the eventual
identification of the quark--gluon plasma.Comment: In ReVTeX 3.0, 9 figs. available from above email address. McGill
93/8, TPI-MINN-93/19-
Observation of Collective-Emission-Induced Cooling inside an Optical Cavity
We report the observation of collective-emission-induced, velocity-dependent
light forces. One third of a falling sample containing 3 x 10^6 cesium atoms
illuminated by a horizontal standing wave is stopped by cooperatively emitting
light into a vertically oriented confocal resonator. We observe decelerations
up to 1500 m/s^2 and cooling to temperatures as low as 7 uK, well below the
free space Doppler limit. The measured forces substantially exceed those
predicted for a single two-level atom.Comment: 10 pages, 5 figure
Forces between a single atom and its distant mirror image
An excited-state atom whose emitted light is back-reflected by a distant
mirror can experience trapping forces, because the presence of the mirror
modifies both the electromagnetic vacuum field and the atom's own radiation
reaction field. We demonstrate this mechanical action using a single trapped
barium ion. We observe the trapping conditions to be notably altered when the
distant mirror is shifted by an optical wavelength. The well-localised barium
ion enables the spatial dependence of the forces to be measured explicitly. The
experiment has implications for quantum information processing and may be
regarded as the most elementary optical tweezers.Comment: 4 pages, 5 figures, published versio
Lower Energy Consequences of an Anomalous High-Energy Neutrino Cross-Section
A new strong-interaction has been postulated for neutrinos above ~10^{19} eV
to explain the production of highest-energy cosmic ray events. We derive a
dispersion relation relating the hypothesized high-energy cross-section to the
lower-energy neutrino-nucleon elastic amplitude. Remarkably, we find that the
real forward amplitude becomes anomalous seven orders of magnitude lower in
energy than does the total cross-section. We discuss possible measurable
consequences of this early onset of new neutrino physics, and conclude that a
significantly enhanced elastic \nu-N scattering rate may occur for the neutrino
beams available at Fermilab and CERN.Comment: 13 pages, LaTe
Selenium enriched vegetables as biofortification alternative for alleviating micronutrient malnutrition
There is a very difficult equation for malnutrition and over-consumption. That means malnutrition even of vitamins and/or minerals (Ca, Cu, Fe, I, Mg, Se and Zn, vitamin A) affects more than two billion people worldwide, largely due to low concentrations or poor bioavailability of the nutrients in the diet. In some developed countries in contrast, over-consumption, particularly of over-refined cerealbased foods, has contributed to the development of an epidemic of metabolic diseases. So, producing nutritious and safe foods sufficiently and sustainably is important target at the same time challenge of modern agriculture. In the past, great efforts have focused only on increasing crop yields, but enhancing the concentrations of mineral micronutrients has become an urgent task. The main daily food source is the staple crops specially in developing countries of the world, i.e., wheat, rice, cassava, beans, sweet potato or maize. These kind of plants are often deficient in some of mineral elements. Thus, the increasing of bioavailable concentration of micronutrients in edible crop tissues (via biofortification) has become a promising strategy in modern agriculture, providing more nutritious foods, to more people, with the use of fewer lands. Biofortification of these trace elements can be achieved application with agronomic process such as soil or foliar fertilization or crop breeding even conventional technic and/or genetic engineering. This review highlight progress to date and identify challenges faced in delivering biofortified vegetable crops as well as the agronomic approaches and tools to improve crop yield and micronutrient content of food crops
Self-bound dense objects in holographic QCD
We study a self-bound dense object in the hard wall model. We consider a
spherically symmetric dense object which is characterized by its radial density
distribution and non-uniform but spherically symmetric chiral condensate. For
this we analytically solve the partial differential equations in the hard wall
model and read off the radial coordinate dependence of the density and chiral
condensate according to the AdS/CFT correspondence. We then attempt to describe
nucleon density profiles of a few nuclei within our framework and observe that
the confinement scale changes from a free nucleon to a nucleus. We briefly
discuss how to include the effect of higher dimensional operator into our
study. We finally comment on possible extensions of our work.Comment: 17 pages, 5 figures, figures replaced, minor revision, to appear in
JHE
- …