10,059 research outputs found
The spacetime structure of MOND with Tully-Fisher relation and Lorentz invariance violation
It is believed that the modification of Newtonian dynamics (MOND) is possible
alternate for dark matter hypothesis. Although Bekenstein's TeVeS supplies a
relativistic version of MOND, one may still wish a more concise covariant
formulism of MOND. In this paper, within covariant geometrical framwork, we
present another version of MOND. We show the spacetime structure of MOND with
properties of Tully-Fisher relation and Lorentz invariance violation.Comment: 6 pages. arXiv admin note: substantial text overlap with
arXiv:1111.1383 and arXiv:1108.344
The binary mass transfer origin of the red blue straggler sequence in M30
Two separated sequences of blue straggler stars (BSSs) have been revealed by
Ferraro et al. (2009) in the color-magnitude diagram (CMD) of the Milky Way
globular cluster M30. Their presence has been suggested to be related to the
two BSS formation channels (namely, collisions and mass-transfer in close
binaries) operating within the same stellar system. The blue sequence was
indeed found to be well reproduced by collisional BSS models. In contrast, no
specific models for mass transfer BSSs were available for an old stellar system
like M30. Here we present binary evolution models, including case-B mass
transfer and binary merging, specifically calculated for this cluster. We
discuss in detail the evolutionary track of a binary, which
spends approximately 4 Gyr in the BSS region of the CMD of a 13 Gyr old
cluster. We also run Monte-Carlo simulations to study the distribution of mass
transfer BSSs in the CMD and to compare it with the observational data. Our
results show that: (1) the color and magnitude distribution of synthetic mass
transfer BSSs defines a strip in the CMD that nicely matches the observed red
BSS sequence, thus providing strong support to the mass transfer origin for
these stars; (2) the CMD distribution of synthetic BSSs never attains the
observed location of the blue BSS sequence, thus reinforcing the hypothesis
that the latter formed through a different channel (likely collisions); (3)
most () of the synthetic BSSs are produced by mass-transfer models,
while the remaining requires the contribution from merger models.Comment: 8 pages, 5 figures, accepted to Ap
The stability of transgene expression and effect of DNA methylation on post transcriptional gene silencing (PTGS) in birch
In this paper, we selected transgenic birch (Betula platyphylla Suk) plants, which included nonsilencing plants, transcriptional silence plants including TP96, TP74, TP73 and the post-transcriptional silence ones (TP67 and TP72). The transcription of the bgt gene in different tissues and organs were significantly different. The transcriptional level of bgt gene in the different tissues and organs was in the following order: leaf > female flower and male flower > branch bark > phloem > root. The transgenic lines were monitored for foreign gene expression for a long-term period of 8 years during their continuous growth under field conditions. GUS protein expression was not reactivated in the transgene silencing lines TP72 and TP67 when cultured in field conditions for long-term period. Meanwhile, no cases of gene silencing were observed again during the study period in the field conditions. Our results suggest that transgene expression in transgenic birch plants appears to be stable under field conditions. The frequencies of methylated cytosines in the code regions of gus gene was studied. Relation of transgene expression and DNA methylation was analysed. The data of restriction enzyme digestion (HpaII and MspI) indicated that DNA methylation resulted in post transcriptional gene silencing (PTGS) in transgenic birch.Key words: Transgenic birch, DNA methylation, gene silencing
Thin front propagation in random shear flows
Front propagation in time dependent laminar flows is investigated in the
limit of very fast reaction and very thin fronts, i.e. the so-called
geometrical optics limit. In particular, we consider fronts evolving in time
correlated random shear flows, modeled in terms of Ornstein-Uhlembeck
processes. We show that the ratio between the time correlation of the flow and
an intrinsic time scale of the reaction dynamics (the wrinkling time ) is
crucial in determining both the front propagation speed and the front spatial
patterns. The relevance of time correlation in realistic flows is briefly
discussed in the light of the bending phenomenon, i.e. the decrease of
propagation speed observed at high flow intensities.Comment: 5 Revtex4 pages, 4 figures include
Simple Stellar Population Models as probed by the Large Magellanic Cloud Star Cluster ESO 121-SC03
The presence of blue straggler stars (BSs) in star clusters has proven a
challenge to conventional simple stellar population (SSP) models. Conventional
SSP models are based on the evolution theory of single stars. Meanwhile, the
typical locations of BSs in the colour-magnitude diagram of a cluster are
brighter and bluer than the main sequence turn-off point. Such loci cannot be
predicted by single-star evolution theory. However, stars with such properties
contribute significantly to the integrated light of the cluster. In this paper,
we reconstruct the integrated properties of the Large Magellanic Cloud cluster
ESO 121-SC03, based on a detailed exploration of the individual cluster stars,
and with particular emphasis on the cluster's BSs. We find that the integrated
light properties of ESO 121-SC03 are dramatically modified by its BS component.
The integrated spectral energy distribution (ISED) flux level is significantly
enhanced toward shorter wavelengths, and all broad-band colours become bluer.
When fitting the fully integrated ISED of this cluster based on conventional
SSP models, the best-fitting values of age and metallicity are significantly
underestimated compared to the true cluster parameters. The age underestimate
is per cent if we only include the BSs within the cluster's half-light
radius and per cent if all BSs are included. The corresponding
underestimates of the cluster's metallicity are and per cent,
respectively. The populous star clusters in the Magellanic Clouds are ideal
objects to explore the potential importance of BSs for the integrated light
properties of more distant unresolved star clusters in a statistically robust
manner, since they cover a large range in age and metallicity.Comment: 11 pages, 7 figures, 2 tables, accepted for publication in MNRA
A new parametric equation of state and quark stars
It is still a matter of debate to understand the equation of state of cold
supra-nuclear matter in compact stars because of unknown on-perturbative strong
interaction between quarks. Nevertheless, it is speculated from an
astrophysical view point that quark clusters could form in cold quark matter
due to strong coupling at realistic baryon densities. Although it is hard to
calculate this conjectured matter from first principles, one can expect the
inter-cluster interaction to share some general features to nucleon-nucleon
interaction. We adopt a two-Gaussian component soft-core potential with these
general features and show that quark clusters can form stable simple cubic
crystal structure if we assume Gaussian form wave function. With this
parameterizing, Tolman-Oppenheimer-Volkoff equation is solved with reasonable
constrained parameter space to give mass-radius relation of crystalline solid
quark star. With baryon densities truncated at 2 times nuclear density at
surface and range of interaction fixed at 2fm we can reproduce similar
mass-radius relation to that obtained with bag model equations of state. The
maximum mass ranges from about 0.5 to 3 solar mass. Observed maximum pulsar
mass (about 2 solar mass) is then used to constrain parameters of this simple
interaction potential.Comment: 5 pages, 2 figure
Effects of Contrarians in the Minority Game
We study the effects of the presence of contrarians in an agent-based model
of competing populations. Contrarians are common in societies. These
contrarians are agents who deliberately prefer to hold an opinion that is
contrary to the prevailing idea of the commons or normal agents. Contrarians
are introduced within the context of the Minority Game (MG), which is a binary
model for an evolving and adaptive population of agents competing for a limited
resource. Results of numerical simulations reveal that the average success rate
among the agents depends non-monotonically on the fraction of
contrarians. For small , the contrarians systematically outperform the
normal agents by avoiding the crowd effect and enhance the overall success
rate. For high , the anti-persistent nature of the MG is disturbed and
the few normal agents outperform the contrarians. Qualitative discussion and
analytic results for the small and high regimes are also
presented, and the crossover behavior between the two regimes is discussed.Comment: revtex, 11 pages, 4 figure
Scaling and non-Abelian signature in fractional quantum Hall quasiparticle tunneling amplitude
We study the scaling behavior in the tunneling amplitude when quasiparticles
tunnel along a straight path between the two edges of a fractional quantum Hall
annulus. Such scaling behavior originates from the propagation and tunneling of
charged quasielectrons and quasiholes in an effective field analysis. In the
limit when the annulus deforms continuously into a quasi-one-dimensional ring,
we conjecture the exact functional form of the tunneling amplitude for several
cases, which reproduces the numerical results in finite systems exactly. The
results for Abelian quasiparticle tunneling is consistent with the scaling
anaysis; this allows for the extraction of the conformal dimensions of the
quasiparticles. We analyze the scaling behavior of both Abelian and non-Abelian
quasiparticles in the Read-Rezayi Z_k-parafermion states. Interestingly, the
non-Abelian quasiparticle tunneling amplitudes exhibit nontrivial k-dependent
corrections to the scaling exponent.Comment: 16 pages, 4 figure
Chaos in Small-World Networks
A nonlinear small-world network model has been presented to investigate the
effect of nonlinear interaction and time delay on the dynamic properties of
small-world networks. Both numerical simulations and analytical analysis for
networks with time delay and nonlinear interaction show chaotic features in the
system response when nonlinear interaction is strong enough or the length scale
is large enough. In addition, the small-world system may behave very
differently on different scales. Time-delay parameter also has a very strong
effect on properties such as the critical length and response time of
small-world networks
Topological structures of adiabatic phase for multi-level quantum systems
The topological properties of adiabatic gauge fields for multi-level
(three-level in particular) quantum systems are studied in detail. Similar to
the result that the adiabatic gauge field for SU(2) systems (e.g. two-level
quantum system or angular momentum systems, etc) have a monopole structure, the
curvature two-forms of the adiabatic holonomies for SU(3) three-level and SU(3)
eight-level quantum systems are shown to have monopole-like (for all levels) or
instanton-like (for the degenerate levels) structures.Comment: 15 pages, no figures. Accepted by J.Phys.
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