26,454 research outputs found
Cheban loops
Left Cheban loops are loops that satisfy the identity x(xy.z) = yx.xz. Right
Cheban loops satisfy the mirror identity {(z.yx)x = zx.xy}. Loops that are both
left and right Cheban are called Cheban loops. Cheban loops can also be
characterized as those loops that satisfy the identity x(xy.z) = (y.zx)x. These
loops were introduced in Cheban, A. M. Loops with identities of length four and
of rank three. II. (Russian) General algebra and discrete geometry, pp.
117-120, 164, "Shtiintsa", Kishinev, 1980. Here we initiate a study of their
structural properties. Left Cheban loops are left conjugacy closed. Cheban
loops are weak inverse property, power associative, conjugacy closed loops;
they are centrally nilpotent of class at most two.Comment: 6 page
The Extended Methanol Maser Emission in W51
The European VLBI Network (EVN) has been used to make phase referenced,
wide-field (several arcminute) spectral line observations of the 6.7-GHz
methanol maser emission towards W51. In the W51main region, the bulk of the
methanol is offset from an UCHII region. This probably indicates the methanol
emission arises at the interface of the expanding UCHII region and not from an
edge-on circumstellar disc, as previously suggested. Near the W51 IRS2 region,
the methanol emission is associated with a very compact, extremely embedded
source supporting the hypothesis that methanol masers trace the earliest stages
of massive star formation. As well as these two previously well studied sites
of star formation, many previously unknown regions star formation are detected,
demonstrating that methanol masers are powerful means of detection young
massive stars.Comment: 5 pages, 3 figure
Anomalous optical absorption in a random system with scale-free disorder
We report on an anomalous behavior of the absorption spectrum in a
one-dimensional lattice with long-range-correlated diagonal disorder with a
power-like spectrum in the form S(k) ~ 1/k^A. These type of correlations give
rise to a phase of extended states at the band center, provided A is larger
than a critical value A_c. We show that for A < A_c the absorption spectrum is
single-peaked, while an additional peak arises when A > A_c, signalling the
occurrence of the Anderson transition. The peak is located slightly below the
low-energy mobility edge, providing a unique spectroscopic tool to monitor the
latter. We present qualitative arguments explaining this anomaly.Comment: 4 pages, 4 postscript figures, uses revtex
A Bose-Einstein Condensate in a Uniform Light-induced Vector Potential
We use a two-photon dressing field to create an effective vector gauge
potential for Bose-condensed Rb atoms in the F=1 hyperfine ground state. The
dressed states in this Raman field are spin and momentum superpositions, and we
adiabatically load the atoms into the lowest energy dressed state. The
effective Hamiltonian of these neutral atoms is like that of charged particles
in a uniform magnetic vector potential, whose magnitude is set by the strength
and detuning of Raman coupling. The spin and momentum decomposition of the
dressed states reveals the strength of the effective vector potential, and our
measurements agree quantitatively with a simple single-particle model. While
the uniform effective vector potential described here corresponds to zero
magnetic field, our technique can be extended to non-uniform vector potentials,
giving non-zero effective magnetic fields.Comment: 5 pages, submitted to Physical Review Letter
Higgs Bosons: Intermediate Mass Range at e+e- Colliders
We elaborate on the production of the Standard Model Higgs particle at
high-energy colliders through the reaction .
Particular emphasis is put on the intermediate mass range. In addition to the
signal we discuss in detail the background processes. Angular distributions
which are sensitive to the spin and parity of the Higgs particle are analyzed.Comment: Standard Latex. 15 pages. 11 figures available by fax or regular
mail. MAD/PH/749, DESY 93-064, UdeM-LPN-TH-93-143, NUHEP-TH-93-1
Weak Turbulent Kolmogorov Spectrum for Surface Gravity Waves
We study the long-time evolution of gravity waves on deep water exited by the
stochastic external force concentrated in moderately small wave numbers. We
numerically implement the primitive Euler equations for the potential flow of
an ideal fluid with free surface written in canonical variables, using
expansion of the Hamiltonian in powers of nonlinearity of up to fourth order
terms.
We show that due to nonlinear interaction processes a stationary energy
spectrum close to is formed. The observed spectrum can be
interpreted as a weak-turbulent Kolmogorov spectrum for a direct cascade of
energy.Comment: 4 pages, 5 figure
Possible co-existence of local itinerancy and global localization in a quasi-one-dimensional conductor
In the chain compound PrBaCuO localization appears simultaneously
with a dimensional crossover in the electronic ground state when the scattering
rate in the chains exceeds the hopping rate between the chains. Here we report
the discovery of a large, transverse magnetoresistance in PrBaCuO
in the localized regime. This result suggests a novel form of localization
whereby electrons retain their metallic (quasi-one-dimensional) character over
a microscopic length scale despite the fact that macroscopically, they exhibit
localized (one-dimensional) behavior.Comment: 4 pages, 4 Figure
Chiral effective theory predictions for deuteron form factor ratios at low Q^2
We use chiral effective theory to predict the deuteron form factor ratio
G_C/G_Q as well as ratios of deuteron to nucleon form factors. These ratios are
calculated to next-to-next-to-leading order. At this order the chiral expansion
for the NN isoscalar charge operator (including consistently calculated 1/M
corrections) is a parameter-free prediction of the effective theory. Use of
this operator in conjunction with NLO and NNLO chiral effective theory wave
functions produces results that are consistent with extant experimental data
for Q^2 < 0.35 GeV^2. These wave functions predict a deuteron quadrupole moment
G_Q(Q^2=0)=0.278-0.282 fm^2-with the variation arising from short-distance
contributions to this quantity. The variation is of the same size as the
discrepancy between the theoretical result and the experimental value. This
motivates the renormalization of G_Q via a two-nucleon operator that couples to
quadrupole photons. After that renormalization we obtain a robust prediction
for the shape of G_C/G_Q at Q^2 < 0.3 GeV^2. This allows us to make precise,
model-independent predictions for the values of this ratio that will be
measured at the lower end of the kinematic range explored at BLAST. We also
present results for the ratio G_C/G_M.Comment: 31 pages, 7 figure
A proposal for a new type of thin-film field-emission display by edge breakdown of MIS structure
A new type of field emission display(FED) based on an edge-enhance electron
emission from metal-insulator-semiconductor (MIS) thin film structure is
proposed. The electrons produced by an avalanche breakdown in the semiconductor
near the edge of a top metal electrode are initially injected to the thin film
of an insulator with a negative electron affinity (NEA), and then are injected
into vacuum in proximity to the top electrode edge. The condition for the
deep-depletition breakdown near the edge of the top metal electrode is
analytically found in terms of ratio of the insulator thickness to the maximum
(breakdown) width of the semiconductor depletition region: this ratio should be
less than 2/(3 \pi - 2) = 0.27. The influence of a neighboring metal electrode
and an electrode thickness on this condition are analyzed. Different practical
schemes of the proposed display with a special reference to M/CaF_2/Si
structure are considered.Comment: 11 pages, 5 figure
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