Simulation of Slow Light with Electronics Circuits

We present an electronic circuit which simulates wave propagation in dispersive media. The circuit is an array of phase shifter composed of operational amplifiers and can be described with a discretized version of one-dimensional wave equation for envelopes. The group velocity can be changed both spatially and temporarily. It is used to emulate slow light or stopped light, which has been realized in a medium with electromagnetically induced transparency (EIT). The group-velocity control of optical pulses is expected to be a useful tool in the field of quantum information and communication.Comment: The following article has been submitted to the American Journal of Physics. After it is published, it will be found at http://scitation.aip.org/ajp (7 pages, 7 figures

Generation of photon pairs using polarization-dependent two-photon absorption

We propose a new method for generating photon pairs from coherent light using polarization-dependent two-photon absorption. We study the photon statistics of two orthogonally polarized modes by solving a master equation, and show that when we prepare a coherent state in one polarization mode, photon pairs are created in the other mode. The photon pairs have the same frequency as that of the incident light.Comment: 4 pages, 3 figures, submitted to PR

D=26 and Exact Solution to the Conformal-Gauge Two-Dimensional Quantum Gravity

The conformal-gauge two-dimensional quantum gravity is formulated in the framework of the BRS quantization and solved completely in the Heisenberg picture: All n-point Wightman functions are explicitly obtained. The field-equation anomaly is shown to exist as in other gauges, but there is no other subtlety. At the critical dimension D=26 of the bosonic string, the field-equation anomaly is shown to be absent. However, this result is not equivalent to the statement that the conformal anomaly is proportional to D-26. The existence of the FP-ghost number current anomaly is seen to be an illusion.Comment: 18 pages, LaTe

Demonstration of negative group delays in a simple electronic circuit

We present a simple electronic circuit which produces negative group delays for base-band pulses. When a band-limited pulse is applied as the input, a forwarded pulse appears at the output. The negative group delays in lumped systems share the same mechanism with the superluminal light propagation, which is recently demonstrated in an absorption-free, anomalous dispersive medium [Wang et al., Nature 406, 277 (2000)]. In this circuit, the advance time more than twenty percent of the pulse width can easily be achieved. The time constants, which can be in the order of seconds, is slow enough to be observed with the naked eye by looking at the lamps driven by the pulses.Comment: 6pages,8 figure

Global dispersive solutions for the Gross-Pitaevskii equation in two and three dimensions

We study asymptotic behaviour at time infinity of solutions close to the non-zero constant equilibrium for the Gross-Pitaevskii equation in two and three spatial dimensions. We construct a class of global solutions with prescribed dispersive asymptotic behavior, which is given in terms of the linearized evolution

CO(J=6-5) Observations of the Quasar SDSS1044-0125 at z = 5.8

We present a result of the quasar CO(J=6-5) observations of SDSSp J104433.04-012502.2 at z = 5.8. Ten-days observations with the Nobeyama Millimeter Array yielded an rms noise level of ~ 2.1 mJy/beam in a frequency range from 101.28 GHz to 101.99 GHz at a velocity resolution of 120 km/s. No significant clear emission line was detected in the observed field and frequency range. Three sigma upper limit on the CO(J=6-5) luminosity of the object is 2.8 x 10^10 K km/s pc^2, corresponding to a molecular gas mass of 1.2 x 10^11 Solar Mass, if a conversion factor of 4.5 Solar Mass /(K km/s pc^2) is adopted. The obtained upper limit on CO luminosity is slightly smaller than those observed in quasars at z=4-5 toward which CO emissions are detected.Comment: 4 pages, 3 figures, LaTeX2e, to appear in Publication of Astronomical Society of Japan (PASJ), Postscript file available at ftp://ftp.kusastro.kyoto-u.ac.jp/pub/iwata/preprint/sdss1044/sdss.ps.g

Dense and Warm Molecular Gas between Double Nuclei of the Luminous Infrared Galaxy NGC 6240

High spatial resolution observations of the 12CO(1-0), HCN(1-0), HCO+(1-0), and 13CO(1-0) molecular lines toward the luminous infrared merger NGC 6240 have been performed using the Nobeyama Millimeter Array and the RAINBOW Interferometer. All of the observed molecular emission lines are concentrated in the region between the double nuclei of the galaxy. However, the distributions of both HCN and HCO+ emissions are more compact compared with that of 12CO, and they are not coincident with the star-forming regions. The HCN/12CO line intensity ratio is 0.25; this suggests that most of the molecular gas between the double nuclei is dense. A comparison of the observed high HCN/13CO intensity ratio, 5.9, with large velocity gradient calculations suggests that the molecular gas is dense [n(H_2)=10^{4-6} cm^-3] and warm (T_kin>50 K). The observed structure in NGC 6240 may be explained by time evolution of the molecular gas and star formation, which was induced by an almost head-on collision or very close encounter of the two galactic nuclei accompanied with the dense gas and star-forming regions.Comment: 25 pages, 8 figures, To be appeared in PASJ 57, No.4 (August 25, 2005) issu

Detection of laser-UV microirradiation-induced DNA photolesions by immunofluorescent staining

A low-power laser-UV microbeam of wave-length 257 nm was used for microirradiation of a small part of the nucleus of Chinese hamster cells. Following fixation in interphase or in the subsequent metaphase indirect immunofluorescent staining was performed with antiserum to photoproducts of DNA treated with far UV light. The results show that antibodies specific for UV-irradiated DNA can be used for a direct detection of laser-UV microirradiation-induced DNA photolesions. The potential usefulness of this method for investigation of the spatial arrangement of chromosomes in the interphase nucleus is discussed