7,516 research outputs found
Measuring robustness of community structure in complex networks
The theory of community structure is a powerful tool for real networks, which
can simplify their topological and functional analysis considerably. However,
since community detection methods have random factors and real social networks
obtained from complex systems always contain error edges, evaluating the
robustness of community structure is an urgent and important task. In this
letter, we employ the critical threshold of resolution parameter in Hamiltonian
function, , to measure the robustness of a network. According to
spectral theory, a rigorous proof shows that the index we proposed is inversely
proportional to robustness of community structure. Furthermore, by utilizing
the co-evolution model, we provides a new efficient method for computing the
value of . The research can be applied to broad clustering problems
in network analysis and data mining due to its solid mathematical basis and
experimental effects.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1303.7434 by other author
Study on radiative decays of and into by means of LFQM
The observed resonance peak around 2.86 GeV has been carefully reexamined by
the LHCb collaboration and it is found that under the peak there reside two
states and which are considered as
and with slightly different masses and
total widths. Thus, the earlier assumption that the resonance
was a state should not be right. We suggest to measure the partial widths
of radiative decays of and to confirm their
quantum numbers. We would consider as or a pure
state, or their mixture and respectively calculate the corresponding
branching ratios as well as those of . The future precise
measurement would provide us information to help identifying the structures of
those resonances .Comment: 8 pages, 4 figures, 1 tabl
3,3′-(p-PhenylÂenedimethylÂene)diÂimidazol-1-ium bisÂ(3-carbÂoxy-4-hydroxyÂbenzeneÂsulfonate) dihydrate
In the title compound, C14H16N4
2+·2C7H5O6S−·2H2O, the 3,3′-(p-phenylÂenedimethylÂene)diimidazol-1-ium dication lies on a crystallographic inversion center. In the crystal structure, dications, anions and solvent water molÂecules are linked via O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds, and C—H⋯π interÂactions, forming a three-dimensional network containing R
2
2(4), R
2
4(12), R
4
4(22), R
8
10(32) and R
12
14(66) ring motifs
Pairing phase transition: A Finite-Temperature Relativistic Hartree-Fock-Bogoliubov study
Background: The relativistic Hartree-Fock-Bogoliubov (RHFB) theory has
recently been developed and it provides a unified and highly predictive
description of both nuclear mean field and pairing correlations. Ground state
properties of finite nuclei can accurately be reproduced without neglecting
exchange (Fock) contributions. Purpose: Finite-temperature RHFB (FT-RHFB)
theory has not yet been developed, leaving yet unknown its predictions for
phase transitions and thermal excitations in both stable and weakly bound
nuclei. Method: FT-RHFB equations are solved in a Dirac Woods-Saxon (DWS) basis
considering two kinds of pairing interactions: finite or zero range. Such a
model is appropriate for describing stable as well as loosely bound nuclei
since the basis states have correct asymptotic behaviour for large spatial
distributions. Results: Systematic FT-RH(F)B calculations are performed for
several semi-magic isotopic/isotonic chains comparing the predictions of a
large number of Lagrangians, among which are PKA1, PKO1 and DD-ME2. It is found
that the critical temperature for a pairing transition generally follows the
rule for a finite-range pairing force and for a contact pairing force, where is the pairing
gap at zero temperature. Two types of pairing persistence are analysed: type I
pairing persistence occurs in closed subshell nuclei while type II pairing
persistence can occur in loosely bound nuclei strongly coupled to the continuum
states. Conclusions: This first FT-RHFB calculation shows very interesting
features of the pairing correlations at finite temperature and in finite
systems such as pairing re-entrance and pairing persistence.Comment: 13 pages, 11 figures, accepted version in Phys. Rev.
Superheavy magic structures in the relativistic Hartree-Fock-Bogoliubov approach
We have explored the occurrence of the spherical shell closures for
superheavy nuclei in the framework of the relativistic Hartree-Fock-Bogoliubov
(RHFB) theory. Shell effects are characterized in terms of two-nucleon gaps
. Although the results depend slightly on the effective
Lagrangians used, the general set of magic numbers beyond Pb are
predicted to be , for protons and , 184, 228 and 258
for neutrons, respectively. Specifically the RHFB calculations favor the
nuclide 120 as the next spherical doubly magic one beyond Pb.
Shell effects are sensitive to various terms of the mean-field, such as the
spin-orbit coupling, the scalar and effective masses.Comment: 3 figures, 1 table, and 5 page
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