A "Cellular Neuronal" Approach to Optimization Problems

The Hopfield-Tank (1985) recurrent neural network architecture for the Traveling Salesman Problem is generalized to a fully interconnected "cellular" neural network of regular oscillators. Tours are defined by synchronization patterns, allowing the simultaneous representation of all cyclic permutations of a given tour. The network converges to local optima some of which correspond to shortest-distance tours, as can be shown analytically in a stationary phase approximation. Simulated annealing is required for global optimization, but the stochastic element might be replaced by chaotic intermittency in a further generalization of the architecture to a network of chaotic oscillators.Comment: -2nd revised version submitted to Chaos (original version submitted 6/07

A theoretical approach to thermal noise caused by an inhomogeneously distributed loss -- Physical insight by the advanced modal expansion

We modified the modal expansion, which is the traditional method used to calculate thermal noise. This advanced modal expansion provides physical insight about the discrepancy between the actual thermal noise caused by inhomogeneously distributed loss and the traditional modal expansion. This discrepancy comes from correlations between the thermal fluctuations of the resonant modes. The thermal noise spectra estimated by the advanced modal expansion are consistent with the results of measurements of thermal fluctuations caused by inhomogeneous losses.Comment: 10 pages, 4 figure

VLBI study of water maser emission in the Seyfert 2 galaxy NGC5793. I: Imaging blueshifted emission and the parsec-scale jet

We present the first result of VLBI observations of the blueshifted water maser emission from the type 2 Seyfert galaxy NGC5793, which we combine with new and previous VLBI observations of continuum emission at 1.7, 5.0, 8.4, 15, and 22 GHz. Maser emission was detected earlier in single-dish observations and found to have both red- and blueshifted features relative to the systemic velocity. We could image only the blueshifted emission, which is located 3.6 pc southwest of the 22 GHz continuum peak. The blueshifted emission was found to originate in two clusters that are separated by 0.7 milliarcsecond (0.16 pc). No compact continuum emission was found within 3.6 pc of the maser spot. A compact continuum source showing a marginally inverted spectrum between 1.7 and 5.0 GHz was found 4.2 pc southwest of the maser position. The spectral turnover might be due to synchrotron self-absorption caused by a shock in the jet owing to collision with dense gas, or it might be due to free-free absorption in an ionized screen possibly the inner part of a disk, foreground to the jet. The water maser may be part of a maser disk. If so, it would be rotating in the opposite sense to the highly inclined galactic disk observed in CO emission. We estimate a binding mass within 1 pc of the presumed nucleus to be on the order of 10^7 Msun. Alternatively, the maser emission could result from the amplification of a radio jet by foreground circumnuclear molecular gas. In this case, the high blueshift of the maser emission might mean that the masing region is moving outward away from the molecular gas surrounding an active nucleus.Comment: 20 pages, 6 figures, to appear in ApJ, Oct. 200

Water Maser Survey toward Low‐Mass Young Stellar Objects in the Northern Sky with the Nobeyama 45 Meter Telescope and the Very Large Array

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Sensitive Radio Observations of High Redshift Dusty QSOs

We present sensitive radio continuum imaging at 1.4 GHz and 4.9 GHz of seven high redshift QSOs selected for having a 240 GHz continuum detection, which is thought to be thermal dust emission. We detect radio continuum emission from four of the sources: BRI 0952-0115, BR 1202-0725, LBQS 1230+1627B, and BRI 1335-0417. The radio source in BR 1202-0725 is resolved into two components, coincident with the double mm and CO sources. We compare the results at 1.4 GHz and 240 GHz to empirical and semi-analytic spectral models based on star forming galaxies at low redshift. The radio-to-submm spectral energy distribution for BR 1202-0725, LBQS 1230+1627B, and BRI 1335-0417 are consistent with that expected for a massive starburst galaxy, with implied massive star formation rates of order 1000 solar masses per year (without correcting for possible amplification by gravitational lensing). The radio-to-submm spectral energy distribution for BRI 0952-0115 suggests a low-luminosity radio jet source driven by the AGN.Comment: 12 pages, Latex emulateapj format, including 1 table and 3 figures. The Astrophysical Journal, to appear in the January 2000 issu

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

L1642 is one of the two high galactic latitude (|b| > 30deg) clouds confirmed to have active star formation. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources in different stages of star formation. We present high-resolution far-infrared and submm observations with the Herschel and AKARI satellites and mm observations with the AzTEC/ASTE telescope, which we combined with archive data from near- and mid-infrared (2MASS, WISE) to mm observations (Planck). The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects at different evolutionary stages. Source B-3 (2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud, instead of a foreground brown dwarf, as previously classified. Herschel data reveal striation in the diffuse dust emission around L1642. The western region shows striation towards NE and has a steeper column density gradient on its southern side. The densest central region has a bow-shock like structure showing compression from the west and a filamentary tail extending towards east. The differences suggest that these may be spatially distinct structures, aligned only in projection. We derive values of the dust emission cross-section per H nucleon for different regions of the cloud. Modified black-body fits to the spectral energy distribution of Herschel and Planck data give emissivity spectral index beta values 1.8-2.0 for the different regions. The compact sources have lower beta values and show an anticorrelation between T and beta. Markov chain Monte Carlo calculations demonstrate the strong anticorrelation between beta and T errors and the importance of mm Planck data in constraining the estimates. L1642 reveals a more complex structure and sequence of star formation than previously known.Comment: 22 pages, 18 figures, accepted to Astronomy & Astrophysics; abstract shortened and figures reduced for astrop