1,570 research outputs found
Astrophysical Configurations with Background Cosmology: Probing Dark Energy at Astrophysical Scales
We explore the effects of a positive cosmological constant on astrophysical
and cosmological configurations described by a polytropic equation of state. We
derive the conditions for equilibrium and stability of such configurations and
consider some astrophysical examples where our analysis may be relevant. We
show that in the presence of the cosmological constant the isothermal sphere is
not a viable astrophysical model since the density in this model does not go
asymptotically to zero. The cosmological constant implies that, for polytropic
index smaller than five, the central density has to exceed a certain minimal
value in terms of the vacuum density in order to guarantee the existence of a
finite size object. We examine such configurations together with effects of
in other exotic possibilities, such as neutrino and boson stars, and
we compare our results to N-body simulations. The astrophysical properties and
configurations found in this article are specific features resulting from the
existence of a dark energy component. Hence, if found in nature would be an
independent probe of a cosmological constant, complementary to other
observations.Comment: 23 pages, 11 figures, 2 tables. Reference added. Mon. Not. Roy.
Astro. Soc in prin
An approach to anomalous diffusion in the n-dimensional space generated by a self-similar Laplacian
We analyze a quasi-continuous linear chain with self-similar distribution of
harmonic interparticle springs as recently introduced for one dimension
(Michelitsch et al., Phys. Rev. E 80, 011135 (2009)). We define a continuum
limit for one dimension and generalize it to dimensions of the
physical space. Application of Hamilton's (variational) principle defines then
a self-similar and as consequence non-local Laplacian operator for the
-dimensional space where we proof its ellipticity and its accordance (up to
a strictly positive prefactor) with the fractional Laplacian
. By employing this Laplacian we establish a
Fokker Planck diffusion equation: We show that this Laplacian generates
spatially isotropic L\'evi stable distributions which correspond to L\'evi
flights in -dimensions. In the limit of large scaled times the obtained distributions exhibit an algebraic decay independent from the initial distribution
and spacepoint. This universal scaling depends only on the ratio of
the dimension of the physical space and the L\'evi parameter .Comment: Submitted manuscrip
On Gauge Invariance of Breit-Wigner Propagators
We present an approach to bosonic () as well as fermionic
(top-quark) Breit-Wigner propagators which is consistent with gauge invariance
arguments. In particular, for the -boson propagator we extend previous
analyses and show that the part proportional to must be
modified near the resonance. We derive a mass shift which agrees with results
obtained elsewhere by different methods. The modified form of a resonant heavy
fermion propagator is also given.Comment: 16 p., TeX, (final version
Finite Width Effects and Gauge Invariance in Radiative Production and Decay
The naive implementation of finite width effects in processes involving
unstable particles can violate gauge invariance. For the example of radiative
production and decay, , at tree level, it is
demonstrated how gauge invariance is restored by including the imaginary part
of triangle graphs in addition to resumming the imaginary contributions to the
vacuum polarization. Monte Carlo results are presented for the Fermilab
Tevatron.Comment: 10 pages, Revtex, 3 figures submitted separately as uuencoded tarred
postscript files, the complete paper is available at
ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-878.ps.Z or
http://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-878.ps.
Effect of energy spectrum law on clustering patterns for inertial particles subjected to gravity in Kinematic Simulation
We study the clustering of inertial particles using a periodic kinematic simulation. Particles
clustering is observed for different pairs of Stokes number and Froude number and different spectral
power laws (1.4 6 p 6 2.1). The main focus is to identify and then quantify the effect of p on the
clustering attractor - by attractor we mean the set of points in the physical space where the particles
settle when time tends to infinity. It is observed that spectral power laws can have a dramatic effect
on the attractor shape. In particular, we observed a new attractor type which was not present in
previous studies for Kolmogorov spectra (p = 5/3)
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