5,954 research outputs found
Model Counting for Formulas of Bounded Clique-Width
We show that #SAT is polynomial-time tractable for classes of CNF formulas
whose incidence graphs have bounded symmetric clique-width (or bounded
clique-width, or bounded rank-width). This result strictly generalizes
polynomial-time tractability results for classes of formulas with signed
incidence graphs of bounded clique-width and classes of formulas with incidence
graphs of bounded modular treewidth, which were the most general results of
this kind known so far.Comment: Extended version of a paper published at ISAAC 201
Polynomial kernels for 3-leaf power graph modification problems
A graph G=(V,E) is a 3-leaf power iff there exists a tree T whose leaves are
V and such that (u,v) is an edge iff u and v are at distance at most 3 in T.
The 3-leaf power graph edge modification problems, i.e. edition (also known as
the closest 3-leaf power), completion and edge-deletion, are FTP when
parameterized by the size of the edge set modification. However polynomial
kernel was known for none of these three problems. For each of them, we provide
cubic kernels that can be computed in linear time for each of these problems.
We thereby answer an open problem first mentioned by Dom, Guo, Huffner and
Niedermeier (2005).Comment: Submitte
Impacts of nuclear-physics uncertainty in stellar temperatures on the s-process nucleosynthesis
N. Nishimura, G. Cescutti, R. Hirschi, T. Rauscher, J. Den Hartogh, and A. St J. Murphy, 'Impacts of nuclear-physics uncertainty in stellar temperatures on the s-process nucleosynthesis', in Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016). Niigata, Japan. June 19-24, 2016. ISBN: 978-4-89027-118-4. DOI: http://dx.doi.org/10.7566/JPSCP.14.020903 © 2017 The Physical Society of Japan.We evaluated the uncertainty relevant to s-process nucleosynthesis using a Monte-Carlo centred approach. We are based on a realistic and general prescription of temperature dependent uncertainty for the reactions. We considered massive stars for the weak s-process and AGB stars for the main s-process. We found that the adopted uncertainty for (n,) rates, tens of per cent on average, affect the production of s-process nuclei along the -stability line, while for -decay, for which contributions from excited states enhances the uncertainty, has the strongest impact on branching points
Impact of the first-forbidden decay on the production of r-process peak
We investigated the effects of first-forbidden transitions in decays
on the production of the r-process peak. The theoretical
calculated -decay rates with -delayed neutron emission were
examined using several astrophysical conditions. As the first-borbidden decay
is dominant in neutron-rich nuclei, their inclusion shortens
-decay lifetimes and shifts the abundance peak towards higher masses.
Additionally, the inclusion of the -delayed neutron emission results in
a wider abundance peak, and smoothens the mass distribution by removing the
odd-even mass staggering. The effects are commonly seen in the results of all
adopted astrophysical models. Nevertheless there are quantitative differences,
indicating that remaining uncertainty in the determination of half-lives for
nuclei is still significant in order to determine the production of the
r-process peak.Comment: 6 pages, 4 figures, 1 table, Phys. Lett. B, in pres
Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-Radiation Hydrodynamics Study
We perform long-term general relativistic neutrino radiation hydrodynamics
simulations (in axisymmetry) for a massive neutron star (MNS) surrounded by a
torus, which is a canonical remnant formed after the binary neutron star
merger. We take into account the effects of viscosity, which is likely to arise
in the merger remnant due to magnetohydrodynamical turbulence. As the initial
condition, we employ the azimuthally averaged data of the MNS-torus system
derived in a three-dimensional, numerical-relativity simulation for the binary
neutron star merger. The viscous effect plays key roles for the remnant
evolution and mass ejection from it in two phases of the evolution. In the
first ms, a differential rotation state of the MNS is changed to
a rigidly rotating state, and as a result, a sound wave, which subsequently
becomes a shock wave, is formed in the vicinity of the MNS due to the variation
of the quasi-equilibrium state of the MNS. The shock wave induces significant
mass ejection of mass for the alpha
viscosity parameter of . For the longer-term evolution with s, a significant fraction of the torus material is ejected. The ejecta
mass is likely to be of order , so that the total mass of the
viscosity-driven ejecta could dominate that of the dynamical ejecta of mass
. The electron fraction, , of the ejecta is
always high enough () that this post-merger ejecta is
lanthanide-poor; hence, the opacity of the ejecta is likely to be
times lower than that of the dynamical ejecta. This indicates that the
electromagnetic signal from the ejecta would be rapidly evolving, bright, and
blue if it is observed from a small viewing angle () for
which the effect of the dynamical ejecta is minor.Comment: 21 pages, 18 figures, accepted for publication in Ap
Impact of nuclear mass uncertainties on the -process
Nuclear masses play a fundamental role in understanding how the heaviest
elements in the Universe are created in the -process. We predict -process
nucleosynthesis yields using neutron capture and photodissociation rates that
are based on nuclear density functional theory. Using six Skyrme energy density
functionals based on different optimization protocols, we determine for the
first time systematic uncertainty bands -- related to mass modeling -- for
-process abundances in realistic astrophysical scenarios. We find that
features of the underlying microphysics make an imprint on abundances
especially in the vicinity of neutron shell closures: abundance peaks and
troughs are reflected in trends of neutron separation energy. Further advances
in nuclear theory and experiments, when linked to observations, will help in
the understanding of astrophysical conditions in extreme -process sites.Comment: 7 pages, 3 figure
Trachyphyllum carinatum Dix. new to China
Trachyphyllum carinatum Dix. is reported new to China from Xishuangbanna
Mosses new to Hong Kong (4)
Sixteen moss species - Eurhynchium asperisetum (C. Muell.) Tak.; Rhynchostegium pallidifolium (Mitt.) Jaeg.; Bryum argenteum Hedw.; Bryum caespiticium Hedw.; Bryum capillare Hedw.; Platyhynidium riarioides (Hedw.) Dix.; Dicranella varia (Hedw.) Schimp.;Entodon virudulus Card.; Fissidens strictulus C. Muell.; Ectropothecium obtusulum (Card.) Iwats.; Caduciella guangdongensis Enroth.; Plagiomnium cuspidatum (Hedw.) T. Kop.; Plagiomnium vesicatum (Besch.) T. Kop.; Pyrrhobryum spiniforme (Hedw.) Mitt., Taxithelium nepalense (Schwaegr.) Broth. and Claopodium aciculum (Broth.) Broth. are reported new to Hong Kong. Among them, four are new to Guangdong Province of China
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