277,849 research outputs found
Proton-proton and deuteron-gold collisions at RHIC
We try to understand recent data on proton-proton and deuteron-gold
collisions at RHIC, employing a modified parton model approach.Comment: Invited talk, given at the XXth Winter Workshop on Nuclear Dynamics,
Trelawny Beach, Jamaica, March 200
Characterizing Some Gaia Alerts with LAMOST and SDSS
Gaia is regularly producing Alerts on objects where photometric variability
has been detected. The physical nature of these objects has often to be
determined with the complementary observations from ground-based facilities. We
have compared the list of Gaia Alerts (until 20181101) with archival LAMOST and
SDSS spectroscopic data. The date of the ground-based observation rarely
corresponds to the date of the Alert, but this allows at least the
identification of the source if it is persistent, or the host galaxy if the
object was only transient like a supernova. A list of Gaia Nuclear Transients
from Kostrzewa-Rutkowska et al. (2018) has been included in this search also.
We found 26 Gaia Alerts with spectra in LAMOST+SDSS labelled as stars (12 with
multi-epoch spectra). A majority of them are CVs. Similarly 206 Gaia Alerts
have associated spectra labelled as galaxies (49 with multi-epoch spectra).
Those spectra were generally obtained on a date different from the Alert date,
are mostly emission-line galaxies, leading to the suspicion that most of the
Alerts were due to a SN. As for the GNT list, we found 55 associated spectra
labelled as galaxies (13 with multi-epoch spectra). In two galaxies, Gaia17aal
and GNTJ170213+2543, was the date of the spectroscopic observation close enough
to the Alert date: we find a trace of the SN itself in their LAMOST spectrum,
both classified here as a type Ia SN. The GNT sample has a higher proportion of
AGNs, suggesting that some of the detected variations are also due to the AGN
itself. Similar for Quasars, we found 30 Gaia Alerts but 68 GNT cases have
single epoch quasar spectra, while 12 plus 23 have multi-epoch spectra. For ten
out of these 35, their multi-epoch spectra show appearance or disappearance of
the broad Balmer lines and also variations in the continuum, qualifying them as
"Changing Look Quasars".Comment: Accepted for publication in APSS, 14 pages, 8 figures, 2 table
Eleven Dimensional Origin of String/String Duality: A One Loop Test
Membrane/fivebrane duality in D=11 implies Type IIA string/Type IIA fivebrane
duality in D=10, which in turn implies Type IIA string/heterotic string duality
in D=6. To test the conjecture, we reproduce the corrections to the 3-form
field equations of the D=10 Type IIA string (a mixture of tree-level and
one-loop effects) starting from the Chern-Simons corrections to the 7-form
Bianchi identities of the D=11 fivebrane (a purely tree-level effect). K3
compactification of the latter then yields the familiar gauge and Lorentz
Chern-Simons corrections to 3-form Bianchi identities of the heterotic string.
We note that the absence of a dilaton in the D=11 theory allows us to fix both
the gravitational constant and the fivebrane tension in terms of the membrane
tension. We also comment on an apparent conflict between fundamental and
solitonic heterotic strings and on the puzzle of a fivebrane origin of
S-duality.Comment: 30 pages (including 5 postscript figures included), LaTeX, Footnote 8
has been removed; the apparent disagreement with Townsend is only one of
semantics, not substanc
Mass in anti-de Sitter spaces
The boundary stress tensor approach has proven extremely useful in defining
mass and angular momentum in asymptotically anti-de Sitter spaces with CFT
duals. An integral part of this method is the use of boundary counterterms to
regulate the gravitational action and stress tensor. In addition to the
standard gravitational counterterms, in the presence of matter we advocate the
use of a finite counterterm proportional to phi^2 (in five dimensions). We
demonstrate that this finite shift is necessary to properly reproduce the
expected mass/charge relation for R-charged black holes in AdS_5.Comment: 15 pages, late
Quantum Statistical Entropy and Minimal Length of 5D Ricci-flat Black String with Generalized Uncertainty Principle
In this paper, we study the quantum statistical entropy in a 5D Ricci-flat
black string solution, which contains a 4D Schwarzschild-de Sitter black hole
on the brane, by using the improved thin-layer method with the generalized
uncertainty principle. The entropy is the linear sum of the areas of the event
horizon and the cosmological horizon without any cut-off and any constraint on
the bulk's configuration rather than the usual uncertainty principle. The
system's density of state and free energy are convergent in the neighborhood of
horizon. The small-mass approximation is determined by the asymptotic behavior
of metric function near horizons. Meanwhile, we obtain the minimal length of
the position which is restrained by the surface gravities and the
thickness of layer near horizons.Comment: 11pages and this work is dedicated to the memory of Professor Hongya
Li
Cross sections for pentaquark baryon production from protons in reactions induced by hadrons and photons
Using hadronic Lagrangians that include the interaction of pentaquark
baryon with and , we evaluate the cross sections for its
production from meson-proton, proton-proton, and photon-proton reactions near
threshold. With empirical coupling constants and form factors, the predicted
cross sections are about 1.5 mb in kaon-proton reactions, 0.1 mb in rho-nucleon
reactions, 0.05 mb in pion-nucleon reactions, 20 b in proton-proton
reactions, and 40 nb in photon-proton reactions.Comment: 14 pages, 7 figure
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