10,475 research outputs found
Full linear perturbations and localization of gravity on brane
We study the thick brane world system constructed in the recently proposed
theories of gravity, with the Ricci scalar and the trace of
the energy-momentum tensor. We try to get the analytic background solutions and
discuss the full linear perturbations, especially the scalar perturbations. We
compare how the brane world model is modified with that of general relativity
coupled to a canonical scalar field. It is found that some more interesting
background solutions are allowed, and only the scalar perturbation mode is
modified. There is no tachyon state exists in this model and only the massless
tensor mode can be localized on the brane, which recovers the effective
four-dimensional gravity. These conclusions hold provided that two constraints
on the original formalism of the action are satisfied.Comment: v3: 8 pages, 2 figures, improved version with minor corrections,
accepted by EPJ
Gravitational resonances on -brane
In this paper, we investigate various -brane models and compare their
gravitational resonance structures with the corresponding general relativity
(GR)-branes. {Starting from some known GR-brane solutions}, we derive thick
-brane solutions such that the metric, scalar field, and scalar potential
coincide with those of the corresponding GR-branes. {We find that for branes
generated by a single or several canonical scalar fields, there is no obvious
distinction between the GR-branes and corresponding -branes in terms of
gravitational resonance structure.} Then we discuss the branes generated by
K-fields. In this case, there could exist huge differences between GR-branes
and -branes.Comment: 17 pages, 14 figures, published versio
Multifractal analysis of weighted networks by a modified sandbox algorithm
Complex networks have attracted growing attention in many fields. As a
generalization of fractal analysis, multifractal analysis (MFA) is a useful way
to systematically describe the spatial heterogeneity of both theoretical and
experimental fractal patterns. Some algorithms for MFA of unweighted complex
networks have been proposed in the past a few years, including the sandbox (SB)
algorithm recently employed by our group. In this paper, a modified SB
algorithm (we call it SBw algorithm) is proposed for MFA of weighted
networks.First, we use the SBw algorithm to study the multifractal property of
two families of weighted fractal networks (WFNs): "Sierpinski" WFNs and "Cantor
dust" WFNs. We also discuss how the fractal dimension and generalized fractal
dimensions change with the edge-weights of the WFN. From the comparison between
the theoretical and numerical fractal dimensions of these networks, we can find
that the proposed SBw algorithm is efficient and feasible for MFA of weighted
networks. Then, we apply the SBw algorithm to study multifractal properties of
some real weighted networks ---collaboration networks. It is found that the
multifractality exists in these weighted networks, and is affected by their
edge-weights.Comment: 15 pages, 6 figures. Accepted for publication by Scientific Report
Applicability of Relativistic Point-Coupling Models to Neutron Star Physics
Comparing with a wide range of covariant energy density functional models
based on the finite-range meson-exchange representation, the relativistic
mean-field models with the zero-range contact interaction, namely the
relativistic point-coupling models, are still infrequent to be utilized in
establishing nuclear equation of state (EoS) and investigating neutron star
properties, although comprehensive applications and achievements of them in
describing many nuclear properties both in ground and exited states are mature.
In this work, the EoS of neutron star matter is established constructively in
the framework of the relativistic point-coupling models to study neutron star
physics. Taking two selected functionals DD-PC1 and PC-PK1 as examples, nuclear
symmetry energies and several neutron star properties including proton
fractions, mass-radius relations, the core-crust transition density, the
fraction of crustal moment of inertia and dimensionless tidal deformabilities
are discussed. A suppression of pressure of neutron star matter found in the
functional PC-PK1 at high densities results in the difficulty of its prediction
when approaching to the maximum mass of neutron stars. In addition, the
divergences between two selected functionals in describing neutron star
quantities mentioned above are still large, ascribing to the less constrained
behavior of these functionals at high densities. Then it is expected that the
constraints on the dense matter EoS from precise and massive modern
astronomical observations, such as the tidal-deformabilities taken from
gravitational-wave events, would be essential to improve the parameterizing of
the relativistic point-coupling models.Comment: To appear in the AIP Proceedings of the Xiamen-CUSTIPEN Workshop on
the EOS of Dense Neutron-Rich Matter in the Era of Gravitational Wave
Astronomy, Jan. 3-7, Xiamen, Chin
Stability of braneworlds with non-minimally coupled multi-scalar fields
Linear stability of braneworld models constructed with multi-scalar fields is
very different from that of single-scalar field models. It is well known that
both the tensor and scalar perturbation equations of the later can always be
written as a supersymmetric Schr\"{o}dinger equation, so it can be shown that
the perturbations are stable at linear level. However, in general it is not
true for multi-scalar field models and especially there is no effective method
to deal with the stability problem of the scalar perturbations for braneworld
models constructed with non-minimally coupled multi-scalar fields. In this
paper we present a method to investigate the stability of such braneworld
models. It is easy to find that the tensor perturbations are stable. For the
stability problem of the scalar perturbations, we present a systematic
covariant approach. The covariant quadratic order action and the corresponding
first-order perturbed equations are derived. By introducing the orthonormal
bases in field space and making the Kaluza-Klein decomposition, we show that
the Kaluza-Klein modes of the scalar perturbations satisfy a set of coupled
Schr\"{o}dinger-like equations, with which the stability of the scalar
perturbations and localization of the scalar zero modes can be analyzed
according to nodal theorem. The result depends on the explicit models. For
superpotential derived barane models, the scalar perturbations are stable, but
there exist normalizable scalar zero modes, which will result in unaccepted
fifth force on the brane. We also use this method to analyze the
braneworld model with an explicit solution and find that the scalar
perturbations are stable and the scalar zero modes can not be localized on the
brane, which ensure that there is no extra long-range force and the Newtonian
potential on the brane can be recovered.Comment: 13 pages, 3 figure
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