282 research outputs found
Gravitational redshifts in electromagnetic bursts occuring near Schwarzschild horizon
It was suggested earlier that the gravitational redshift formula can be
invalid when the effect of the backscattering is strong. It is demonstrated
here numerically, for an exemplary electromagnetic pulse that is: i) initially
located very close to the horizon of a Schwarzschild black hole and ii)
strongly backscattered, that a mean frequency does not obey the standard
redshift formula. Redshifts appear to depend on the frequency and there
manifests a backscatter-induced blueshift in the outgoing radiation.Comment: 4 pages, 2 figures. To appear in the Class. Q. Gra
Strictly finite range forces from the signum-Gordon field: exact results in two spatial dimensions
Exact formula for the force between two identical static point charges
coupled to the nonlinear scalar field of two-dimensional signum-Gordon model is
obtained. Pertinent solution of the field equation is found in the form of
one-dimensional integral. The force exactly vanishes when the distance between
the charges exceeds certain critical value.Comment: published versio
The distance and neutral environment of the massive stellar cluster Westerlund 1
The goal of this study is to determine a distance to Westerlund 1 independent
of the characteristics of the stellar population and to study its neutral
environment, using observations of atomic hydrogen. The HI observations are
taken from the Southern Galactic Plane Survey to study HI absorption in the
direction of the HII region created by the members of Westerlund 1 and to
investigate its environment as observed in the HI line emission. A Galactic
rotation curve was derived using the recently revised values for the Galactic
centre distance of kpc, and the velocity of the Sun around the
Galactic centre of km s. The newly determined
rotation model leads us to derive a distance of kpc to Westerlund
1, consistent with a location in the Scutum-Crux Arm. Included in this estimate
is a very careful investigation of possible sources of error for the Galactic
rotation curve. We also report on small expanding HI features around the
cluster with a maximum dynamic age of 600,000 years and a larger bubble which
has a minimum dynamic age of 2.5 million years. Additionally we re-calculated
the kinematic distances to nearby HII regions and supernova remnants based on
our new Galaxic rotation curve. We propose that in the early stages of the
development of Wd 1 a large interstellar bubble of diameter about 50 pc was
created by the cluster members. This bubble has a dynamic age similar to the
age of the cluster. Small expanding bubbles, with dynamical ages Myr
are found around Wd 1, which we suggest consist of recombined material lost by
cluster members through their winds.Comment: 8 pages, accepted for publication in A&
Nambu-Goto string action with Gauss-Bonnet term
We examine the relativistic Nambu-Goto model with Gauss-Bonnet boundary term
added to the action integral. The system is analysed using an invariant
representation of dynamical string degrees of freedom by complex Liouville
fields. The solutions of classical equations of motion for open strings are
described.Comment: 9 pages, late
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