28,339 research outputs found
Topological Discrete Algebra, Ground State Degeneracy, and Quark Confinement in QCD
Based on the permutation group formalism, we present a discrete symmetry
algebra in QCD. The discrete algebra is hidden symmetry in QCD, which is
manifest only on a space-manifold with non-trivial topology. Quark confinement
in the presence of the dynamical quarks is discussed in terms of the discrete
symmetry algebra. It is shown that the quark deconfinement phase has the ground
state degeneracy depending on the topology of the space, which gives a
gauge-invariant distinction between the confinement and deconfinement phases.
We also point out that new quantum numbers relating to the fractional quantum
Hall effect exist in the deconfinement phase.Comment: 11 pages, 1 figur
Seismic anisotropy of Precambrian lithosphere : Insights from Rayleigh wave tomography of the eastern Superior Craton
The seismic data used in this study are freely available from the CNDC (Canadian National Data Centre for Earthquake Seismology and Nuclear Explosion Monitoring) and IRIS DMC (Data Management Center) via their data request tools. The Leverhulme Trust (grant RPG-2013-332) and National Science Foundation are acknowledged for financial support. L.P. is supported by Janet Watson Imperial College Department Scholarship and the Romanian Government Research Grant NUCLEU. F.D. is supported by NSERC through the Discovery Grants and Canada Research Chairs program. We also thank two anonymous reviewers and the Associate Editor for insightful comments that helped improve the manuscript.Peer reviewedPublisher PD
Convergence of the Allen-Cahn equation with Neumann boundary conditions
We study a singular limit problem of the Allen-Cahn equation with Neumann
boundary conditions and general initial data of uniformly bounded energy. We
prove that the time-parametrized family of limit energy measures is Brakke's
mean curvature flow with a generalized right angle condition on the boundary.Comment: 26 pages, 1 figur
Diretrizes para o projeto gráfico da Agropedia brasilis.
Este trabalho estabelece as diretrizes para a construção de um projeto gráfico adequado para a Agropedia brasilis, embasado nas funcionalidades demandadas pelos empregados da Embrapa, em aspectos de usabilidade de sites e nas regras institucionais para a presença digital da empresa
Chandra deep X-ray observation on the Galactic plane
Using the Chandra ACIS-I instruments, we have carried out the deepest X-ray
observation on a typical Galactic plane region at l 28.5 deg, where no discrete
X-ray sources have been known previously. We have detected, as well as strong
diffuse emission, 275 new point X-ray sources (4 sigma confidence) within two
partially overlapping fields (~250 arcmin^2 in total) down to ~3 x 10^{-15} erg
s^{-1} cm^{-2} (2 -- 10 keV) or ~ 7 x 10^{-16} erg s^{-1} cm^{-2} (0.5 -- 2
keV). We have studied spectral distribution of these point sources, and found
that very soft sources detected only below ~ 3 keV are more numerous than hard
sources detected only above ~ 3 keV. Only small number of sources are detected
both in the soft and hard bands. Surface density of the hard sources is almost
consistent with that at high Galactic regions, thus most of the hard sources
are considered to be Active Galactic Nuclei seen through the milky way. On the
other hand, some of the bright hard X-ray sources which show extremely flat
spectra and iron line or edge features are considered to be Galactic,
presumably quiescent dwarf novae. The soft sources show thermal spectra and
small interstellar hydrogen column densities, and some of them exhibit X-ray
flares. Therefore, most of the soft sources are probably X-ray active nearby
late type stars.Comment: Contribution to the proceedings of the "New Visions of the X-Ray
Universe in the XMM-Newton and Chandra Era" symposium at ESTEC, The
Netherlands. 26-30 Nov. 200
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