609 research outputs found
Dynamics of Massive Scalar Fields in dS Space and the dS/CFT Correspondence
Global geometric properties of dS space are presented explicitly in various
coordinates. A Robertson-Walker like metric is deduced, which is convenient to
be used in study of dynamics in dS space. Singularities of wavefunctions of
massive scalar fields at boundary are demonstrated. A bulk-boundary propagator
is constructed by making use of the solutions of equations of motion. The
dS/CFT correspondence and the Strominger's mass bound is shown.Comment: latex, 14 pages and 3 figure
Discovery, photometry, and astrometry of 49 classical nova candidates in M81 galaxy
This paper reports on a search for new classical nova candidates in the M81
galaxy based on archival, as well as recent, new images. We used images from
1999-2007 to search for optical transients in M81. The positions of the
identified classical nova candidates were used to study their spatial
distribution. Kolmogorov - Smirnov test (KS) and bottom-to-top (BTR) ratio
diagnostic were used to analyze the nova candidate distribution and
differentiate between the disk and the bulge populations. In total, 49
classical nova candidates were discovered. In this study, we present the
precise positions and photometry of these objects, plus the photometry of an
additional 9 classical nova candidates found by Neill and Shara (2004). With
our large sample, we find a different spatial distribution of classical nova
candidates when compared to the results of earlier studies. Also, an
extraordinarily bright nova was found and studied in detail.Comment: Accepted for publication in Astronomy & Astrophysics, 23 pages, 8
figure
Early Tracking Behavior in Small-field Quintessence Models
We study several quintessence models which are singular at Q=0, and use a
simple initial constraint to see when they enter
tracking regime, disregarding the details of inflation. We find it can give
strong constraints for the inverse power-law potential ,
which has to enter tracking regime for . While for the
supergravity model , the constraint is much
weakened. For another kind inverse power-law potential , it exhibits no constraints.Comment: 11 pages,5 figures. Improved versio
BVRI Observations of the Optical Afterglow of GRB 990510
We present observations of the optical counterpart to the Gamma-Ray
Burst (GRB) 990510 obtained with the Las Campanas 1.0-m telescope between 15
and 48 hours after the burst. The temporal analysis of the data indicates
steepening decay, independent of wavelength, approaching asymptotically
at early times ( and at
late times, with the break time at . GRB 990510 is the
most rapidly fading of the well-documented GRB afterglows. It is also the first
observed example of broad-band break for a GRB optical counterpart. The optical
spectral energy distribution, corrected for significant Galactic reddening, is
well fitted by a single power-law with . However, when the
-band point is dropped from the fit, the power-law becomes , indicating a possible deviation from the power-law in the spectrum,
either intrinsic or due to additional extinction near the source or from an
intervening galaxy at . Broad-band break behavior broadly similar to
that observed in GRB 990510 has been predicted in some jet models of GRB
afterglows, thus supporting the idea that the GRB energy is beamed, at least in
some cases.Comment: submitted to the ApJ Letters, 13 pages, 5 tables, 3 figures;
additional data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB990510/
and through WWW at http://cfa-www.harvard.edu/cfa/oir/Research/GRB
Analysis of Jovian decametric data: Study of radio emission mechanisms
The Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) have produced the finest set of Jovian decametric radio emission data ever obtained. Jovian decametric L-burst and S-burst arcs were characterized and the data reconciled with models for the radio emission geometry and mechanisms. The first major results involve comparisons of the distribution of arc separations with longitudes. The identification and analyses of systematic variations in the PRA data have yielded interesting results, but only the most obvious features of the data were examined. Analyses of the PRA data were extended with the use of new 6-Sec formats that are more sensitive to the S-bursts
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