57,642 research outputs found
On a q-analog of the Wallach-Okounkov formula
We obtain a -analog of the well known Wallach-Okounkov result on a joint
spectrum of invariant differential operators with polynomial coefficients on a
prehomogeneous vector space of complex -matrices. We are motivated
by applications to the problems of harmonic analysis in the quantum matrix
ball: our main theorem can be used while proving the Plancherel formula (to be
published).
This paper is dedicated to our friend and colleague Dmitry Shklyarov who
celebrates his 30-th birthday on April 8, 2006.Comment: 10 pages, corrected minor misprint
The influences of the galactic cosmic ray on the atmospheric ozone
The relationship between the yearly variations of cosmic ray intensity and ozone in the atmosphere, and the ozone disturbance initiated by the Forbush decrease of 1965-1976 is analyzed. The data on cosmic ray intensity were selected from the records of the super neutron monitor at Deep River station and the ionization chamber at Beijing station. Ozone data were taken from Resolute (Canada), Bismark (N. Dakota, USA), Kagoshima (Japan), and Kodaikanal (India). The statistical results show that ozone is prominently modulated and disturbed by the 11 year variation and the Forbush decrease in the galactic cosmic ray
Ultrasensitive detections in atomic and molecular physics: demonstration in molecular overtone spectroscopy
We consider several highly sensitive techniques commonly used in detection of atomic and molecular absorptions. Their basic operating principles and corresponding performances are summarized and compared. We then present our latest results on the ultrasensitive detection of molecular overtone transitions to illustrate the principle and application of the cavity-enhanced frequency-modulation (FM) spectroscopy. An external cavity is used to enhance the molecular response to the light field, and an FM technique is applied for shot-noise-limited signal recovery. A perfect match between the FM sideband frequency and the cavity free spectral range makes the detection process insensitive to the laser-frequency noise relative to the cavity, and, at the same time, overcomes the cavity bandwidth limit. Working with a 1.064-µm Nd:YAG laser, we obtained sub-Doppler overtone resonances of C2HD, C2H2, and CO2 molecules. A detection sensitivity of 5 x 10^-13 of integrated absorption (1 x 10^-14/cm) over 1-s averaging time has been achieved
Discriminative Cooperative Networks for Detecting Phase Transitions
The classification of states of matter and their corresponding phase
transitions is a special kind of machine-learning task, where physical data
allow for the analysis of new algorithms, which have not been considered in the
general computer-science setting so far. Here we introduce an unsupervised
machine-learning scheme for detecting phase transitions with a pair of
discriminative cooperative networks (DCN). In this scheme, a guesser network
and a learner network cooperate to detect phase transitions from fully
unlabeled data. The new scheme is efficient enough for dealing with phase
diagrams in two-dimensional parameter spaces, where we can utilize an active
contour model -- the snake -- from computer vision to host the two networks.
The snake, with a DCN "brain", moves and learns actively in the parameter
space, and locates phase boundaries automatically
Medium effects in the production and decay of vector mesons in pion-nucleus reactions
The -, - and -resonance production and their dileptonic
decay in reactions at 1.1 - 1.7 GeV/c are calculated within the
intranuclear cascade (INC) approach. The invariant mass distribution of the
dilepton pair for each resonance can be decomposed in two components which
correspond to their decay 'inside' the target nucleus and in the vacuum,
respectively. The first components are strongly distorted by the nuclear medium
due to resonance-nucleon scattering and a possible mass shift at finite baryon
density. These medium modifications are compared to background sources in the
dilepton spectrum from bremsstrahlung as well as the Dalitz decays of
and mesons produced in the reaction. Detailed predictions for
reactions at 1.3 and 1.7 GeV/c are made within several momentum bins
for the lepton pair.Comment: 29 pages, LaTeX, including 12 postscript figures, UGI-97-07, Nucl.
Phys. A., in pres
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