21 research outputs found
A 12.5 GHz-Spaced Optical Frequency Comb Spanning >400 nm for near-Infrared Astronomical Spectrograph Calibration
A 12.5 GHz-spaced optical frequency comb locked to a Global Positioning
disciplined oscillator for near-IR spectrograph calibration is presented. The
comb is generated via filtering a 250 MHz-spaced comb. Subsequency nonlinear
broadening of the 12.5 GHz comb extends the wavelength range to cover 1380 nm
to 1820 nm, providing complete coverage over the H-band transmission widow of
Earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth
and instability of the comb have been examined to estmiate potential wavelength
biases in spectrograph calibration. Sidemode suppression varies between 20 db
and 45 dB, and the optical linewidth is ~350 kHz at 1550 nm. The comb frequency
uncertainty is bounded by +/- 30 kHz (corresponding to a radial velocity of +/-
5 cm/s), limited by the Global Positioning System disciplined oscillator
reference. These results indicate this comb can readily support radial velocity
measurements below 1 m/s in the near-IR.Comment: 16 pages, 12 figures, new file fixes some readability problems on
Mac
The Bekenstein Formula and String Theory (N-brane Theory)
A review of recent progress in string theory concerning the Bekenstein
formula for black hole entropy is given. Topics discussed include p-branes,
D-branes and supersymmetry; the correspondence principle; the D- and M-brane
approach to black hole entropy; the D-brane analogue of Hawking radiation, and
information loss; D-branes as probes of black holes; and the Matrix theory
approach to charged and neutral black holes. Some introductory material is
included.Comment: 53 pages, LaTeX. v3: Typos fixed, minor updates, references added,
brief Note Added on AdS/CF
Knots, Feynman diagrams and matrix models
Grothaus M, Streit L, Volovich IV. Knots, Feynman diagrams and matrix models. INFINITE DIMENSIONAL ANALYSIS QUANTUM PROBABILITY AND RELATED TOPICS. 1999;2(3):359-380.A U(N)-invariant matrix model with d matrix variables is studied. It was shown that in the limit N --> infinity and d --> 0 the model describes the knot diagrams. We realize the free partition function of the matrix model as the generalized expectation of a Hida distribution Phi(N,d). This enables us to give a mathematically rigorous meaning to the partition function with interaction. For the generalized function Phi(N,d), we prove a Wick theorem and we derive explicit formulas for the propagators