18,106 research outputs found
The KCAL VERA 22 GHz calibrator survey
We observed at 22 GHz with the VLBI array VERA a sample of 1536 sources with
correlated flux densities brighter than 200 mJy at 8 GHz. One half of target
sources has been detected. The detection limit was around 200 mJy. We derived
the correlated flux densities of 877 detected sources in three ranges of
projected baseline lengths. The objective of these observations was to
determine the suitability of given sources as phase calibrators for dual-beam
and phase-referencing observations at high frequencies. Preliminary results
indicate that the number of compact extragalactic sources at 22 GHz brighter
than a given correlated flux density level is twice less than at 8 GHz.Comment: Accepted for publication by the Astronomical Journal. 6 pages, 3
figures, 3 table. The machine readable catalogue file, kcal_cat.txt can be
extracted from the source of this submissio
Elastic Multi-Body Interactions on a Lattice
We show that by coupling two hyperfine states of an atom in an optical
lattice one can independently control two-, three-, and four-body on-site
interactions in a non-perturbative manner. In particular, under typical
conditions of current experiments one can have a purely three- or four-body
interacting gas of K atoms characterized by on-site interaction shifts
of several 100Hz.Comment: 6 pages, 3 figure
Three-Body Interacting Bosons in Free Space
We propose a method of controlling two- and three-body interactions in an
ultracold Bose gas in any dimension. The method requires us to have two coupled
internal single-particle states split in energy such that the upper state is
occupied virtually but amply during collisions. By varying system parameters
one can switch off the two-body interaction while maintaining a strong
three-body one. The mechanism can be implemented for dipolar bosons in the
bilayer configuration with tunnelling or in an atomic system by using
radio-frequency fields to couple two hyperfine states. One can then aim to
observe a purely three-body-interacting gas, dilute self-trapped droplets, the
paired superfluid phase, Pfaffian state, and other exotic phenomena.Comment: Published version with Supplemental Materia
From the exclusive photoproduction of heavy quarkonia at HERA to the EDDE at TeVatron and LHC
Exclusive photoproduction of heavy quarkonia at HERA is analyzed in the
framework of the Regge-eikonal approach together with the nonrelativistic bound
state formalism. Total and differential cross-sections for the process
are calculated. The model predicts
cross-sections of Exclusive Double Diffractive Events (EDDE) at TeVatron and
LHC.Comment: 14 pages, 6 figures, reference is adde
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