Structural preferential attachment: Stochastic process for the growth of scale-free, modular and self-similar systems. (arXiv:1109.0034v1 [physics.soc-ph])

Many complex systems have been shown to share universal properties of
organization, such as scale independence, modularity and self-similarity. We
borrow tools from statistical physics in order to study structural preferential
attachment (SPA), a recently proposed growth principle for the emergence of the
aforementioned properties. We study the corresponding stochastic process in
terms of its time evolution, its asymptotic behaviour and the scaling
properties of its statistical steady state. Moreover, approximations are
introduced to facilitate the reproduction of real systems, mainly complex
networks, using SPA. Finally, we investigate a particular behaviour observed in
the stochastic process, the peloton dynamics, and show how it predicts some
features of real growing systems using prose samples as an example.

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Thermal and mechanical denaturation properties of a DNA model with three sites per nucleotide. (arXiv:1108.5390v1 [physics.bio-ph])

In this paper, we show that the coarse grain model for DNA, which has been
proposed recently by Knotts, Rathore, Schwartz and de Pablo (J. Chem. Phys.
126, 084901 (2007)), can be adapted to describe the thermal and mechanical
denaturation of long DNA sequences by adjusting slightly the base pairing
contribution. The adjusted model leads to (i) critical temperatures for long
homogeneous sequences that are in good agreement with both experimental ones
and those obtained from statistical models, (ii) a realistic step-like
denaturation behaviour for long inhomogeneous sequences, and (iii) critical
forces at ambient temperature of the order of 10 pN, close to measured values.
The adjusted model furthermore supports the conclusion that the thermal
denaturation of long homogeneous sequences corresponds to a first-order phase
transition and yields a critical exponent for the critical force equal to
sigma=0.70. This model is both geometrically and energetically realistic, in
the sense that the helical structure and the grooves, where most proteins bind,
are satisfactorily reproduced, while the energy and force required to break a
base pair lie in the expected range. It therefore represents a promising tool
for studying the dynamics of DNA-protein specific interactions at an
unprecedented detail level.

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Heat Transfer and Reconnection Diffusion in Turbulent Magnetized Plasmas. (arXiv:1108.2280v1 [astro-ph.GA])

It is well known that magnetic fields constrain motions of charged particles,
impeding the diffusion of charged particles perpendicular to magnetic field
direction. This modification of transport processes is of vital importance for
a wide variety of astrophysical processes including cosmic ray transport,
transfer of heavy elements in the interstellar medium, star formation etc.
Dealing with these processes one should keep in mind that in realistic
astrophysical conditions magnetized fluids are turbulent. In this review we
single out a single transport process, namely, heat transfer and consider how
it occurs in the presence of the magnetized turbulence. We show that the
ability of magnetic field lines to constantly change topology and connectivity
is at the heart of the correct description of the 3D magnetic field
stochasticity in turbulent fluids. This ability is ensured by fast magnetic
reconnection in turbulent fluids and puts forward the concept of reconnection
diffusion at the core of the physical picture of heat transfer in astrophysical
plasmas. Appealing to reconnection diffusion we describe the ability of plasma
to diffuse between different magnetized eddies explaining the advection of the
heat by turbulence. Adopting the structure of magnetic field that follows from
the modern understanding of MHD turbulence, we also discuss thermal
conductivity that arises as electrons stream along stochastic magnetic field
lines. We compare the effective heat transport that arise from the two
processes and conclude that in many astrophysically-motivated cased eddy
advection of heat dominates. Finally, we discuss the concepts of sub and
superdiffusion and show that the subdiffusion requires rather restrictive
settings. At the same time, accelerated diffusion or superdiffusion of heat is
possible on the scales less than the injection scale of the turbulence.

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Electron Correlation via Frozen Gaussian Dynamics. (arXiv:1108.2034v1 [physics.chem-ph])

We investigate the accuracy and efficiency of the semiclassical Frozen
Gaussian method in describing electron dynamics in real time. Model systems of
two soft-Coulomb-interacting electrons are used to study correlated dynamics
under non-perturbative electric fields, as well as the excitation spectrum. The
results show that a recently proposed method that combines exact-exchange with
semiclassical correlation to propagate the one-body density-matrix holds
promise for electron dynamics in many situations that either wavefunction or
density-functional methods have difficulty describing. The results also however
point out challenges in such a method that need to be addressed before it can
become widely applicable.

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Dust f(R,T) Models. (arXiv:1107.5807v1 [physics.gen-ph])

In this Letter, we reconstruct cosmological models in the frame of the new
model $ f(R,T)$ , where $ R$ is the Ricci scalar and $ T$ is the trace of the
stress-energy tensor. This model was recently proposed by [T. Harko, F.S.N.
Lobo, S. Nojiri, S.D. Odintsov, Phys. Rev. D 84, 024020 (2011)]. We show that
the dust fluid reproduce $ \Lambda $ CDM, phantom-non phantom era and also the
phantom cosmology with some specified forms of the action $ f(R,T)$ . We also
considered the important case $ f(R,T)=f_1(R)+f_2(T)$ .

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• genph
• T Harko F S N Lobo S Nojiri S D Odintsov Phys Rev D 84 024020 (2011)

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Mapping the Arnold web with a GPU-supercomputer. (arXiv:1107.4107v1 [nlin.CD])

The Arnold diffusion constitutes a dynamical phenomenon which may occur in
the phase space of a non-integrable Hamiltonian system whenever the number of
the system degrees of freedom is $ M \geq 3$ . The diffusion is mediated by a
web-like structure of resonance channels, which penetrates the phase space and
allows the system to explore the whole energy shell. The Arnold diffusion is a
slow process; consequently the mapping of the web presents a very
time-consuming task. We demonstrate that the exploration of the Arnold web by
use of a graphic processing unit (GPU)-supercomputer can result in distinct
speedups of two orders of magnitude as compared to standard CPU-based
simulations.

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Comments on: “Energetic balance for the Rayleigh–Stokes problem of an Oldroyd-B fluid” [Nonlinear Anal. RWA 12 (2011) 1]. (arXiv:1107.2947v1 [physics.flu-dyn])

We point out that an erroneous derivation in the recent paper [Fetecau et
al., Nonlinear Anal. RWA 12 (2011) 1] yields a correct solution by accident.
Additionally, a number of misrepresentations and inaccuracies in the latter
recent paper are identified, corrected and/or clarified in this Comment.
Finally, a listing of recent papers in this journal that make a mistake
applying the Fourier sine transform, and thus present erroneous solutions, is
given as an Appendix.

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Perturbed stellar motions around the rotating black hole in Sgr A* for a generic orientation of its spin axis. (arXiv:1107.2916v1 [gr-qc])

Empirically determining the averaged variations of the orbital parameters of
the stars orbiting the Supermassive Black Hole (SBH) hosted by the Galactic
Centre (GC) in Sgr A* is, in principle, a valuable tool to put on the test the
General Theory of Relativity (GTR), in regimes far stronger than those tested
so far, and certain key predictions of it like the no-hair theorems. We
analytically work out the long-term variations of all the six osculating
Keplerian orbital elements of a test particle orbiting a non-spherical,
rotating body with quadrupole moment Q_2 and angular momentum S for a generic
spatial orientation of its spin axis k. This choice is motivated by the fact
that, basically, we do not know the position in the sky of the spin axis of the
SBH in Sgr A* with sufficient accuracy. We apply our results to S2, which is
the closest star discovered so far having an orbital period P_b = 15.98 yr, and
to a hypothetical closer star X with P_b = 0.5 yr. Our calculations are quite
general, not being related to any specific parameterization of k, and can be
applied also to astrophysical binary systems, stellar planetary systems, and
planetary satellite geodesy in which different reference frames, generally not
aligned with the primary’s rotational axis, are routinely used.

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Who Is God?

This article is dedicated to Mr. Bhimsen Panda, my role model & teacher, who have been a source of inspiration & support for me. Sir, this is for you.

Who is God? I think this is by far the most controversial or most asked question of all time which had largely affected our way of thinking. God is our creator, a being which is responsible for the beginning of our universe. Throughout the history, people have been giving many ideas or views. In response to these ideas, people started to believe in some forms of powers which rule the cosmos. After the formation of human civilization, people started to break apart within many believes which is called religion. Today there are Christianity, Islam, Hinduism & Buddhism as major religions along with other kind of minor religions. Every religion has its ideas about the nature. Each & every religion believes in different forms of superpower. All these are OK till social level, but when it comes to science, all these are dismissed. Science doesn’t believe in creator or God because there’s no experimental prove of existence of any kind of super being throughout the universe. Science makes God meaningless. Almost no scientist believes in God. All are atheist. But there’re still few of them, who keep believe in a creator. Prof. Stephen Hawking, regarded as one of the greatest physicist & cosmologist of the century, said in his book The Grand Design that science makes God unnecessary. Only the laws of nature rule. Now I want to be a scientist (astrophysicist) in future. So what view do I hold?

Few years ago, I wasn’t thinking on all these matters as I was too young. But all of a sudden, some days or months earlier, I started to think on the topic. Who is our God? Who created us? The top most priority goes to laws of nature. So, for me laws of nature is the creator or God. Every where we see, every thing is dominated by laws of nature. But still questions arise, was there … Continue reading …

The Great Escape: How Exoplanets and Smaller Bodies Desert Dying Stars. (arXiv:1107.1239v1 [astro-ph.EP])

Mounting discoveries of extrasolar planets orbiting post-main sequence stars
motivate studies aimed at understanding the fate of these planets. In the
traditional “adiabatic” approximation, a secondary’s eccentricity remains
constant during stellar mass loss. Here, we remove this approximation,
investigate the full two-body point-mass problem with isotropic mass loss, and
illustrate the resulting dynamical evolution. The magnitude and duration of a
star’s mass loss combined with a secondary’s initial orbital characteristics
might provoke ejection, modest eccentricity pumping, or even circularisation of
the orbit. We conclude that Oort clouds and wide-separation planets may be
dynamically ejected from 1-7 Solar-mass parent stars during AGB evolution. The
vast majority of planetary material which survives a supernova from a 7-20
Solar-mass progenitor will be dynamically ejected from the system, placing
limits on the existence of first-generation pulsar planets. Planets around >20
Solar-mass black hole progenitors may easily survive or readily be ejected
depending on the core collapse and superwind models applied. Material ejected
during stellar evolution might contribute significantly to the free-floating
planetary population.

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• Everything and More: A Compact History of Infinity djvu
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