325,944 research outputs found
Unexpected High Brightness Temperature 140 PC from the Core in the Jet of 3C 120
We present 1.7, 5, 15, 22 and 43 GHz polarimetric multi-epoch VLBA
observations of the radio galaxy 3C 120. The higher frequency observations
reveal a new component, not visible before April 2007, located 80 mas from the
core (which corresponds to a deprojected distance of 140 pc), with a brightness
temperature about 600 times higher than expected at such distances. This
component (hereafter C80) is observed to remain stationary and to undergo small
changes in its brightness temperature during more than two years of
observations. A helical shocked jet model - and perhaps some flow acceleration
- may explain the unusually high Tb of C80, but it seems unlikely that this
corresponds to the usual shock that emerges from the core and travels
downstream to the location of C80. It appears that some other intrinsic process
in the jet, capable of providing a local burst in particle and/or magnetic
field energy, may be responsible for the enhanced brightness temperature
observed in C80, its sudden appearance in April 2007, and apparent
stationarity.Comment: 5 pages, 5 figures Accepted to be published in ApJ Letter
Asymptotic behaviour of zeros of exceptional Jacobi and Laguerre polynomials
The location and asymptotic behaviour for large n of the zeros of exceptional
Jacobi and Laguerre polynomials are discussed. The zeros of exceptional
polynomials fall into two classes: the regular zeros, which lie in the interval
of orthogonality and the exceptional zeros, which lie outside that interval. We
show that the regular zeros have two interlacing properties: one is the natural
interlacing between consecutive polynomials as a consequence of their
Sturm-Liouville character, while the other one shows interlacing between the
zeros of exceptional and classical polynomials. A generalization of the
classical Heine-Mehler formula is provided for the exceptional polynomials,
which allows to derive the asymptotic behaviour of their regular zeros. We also
describe the location and the asymptotic behaviour of the exceptional zeros,
which converge for large n to fixed values.Comment: 19 pages, 3 figures, typed in AMS-LaTe
Two novel classes of solvable many-body problems of goldfish type with constraints
Two novel classes of many-body models with nonlinear interactions "of
goldfish type" are introduced. They are solvable provided the initial data
satisfy a single constraint (in one case; in the other, two constraints): i.
e., for such initial data the solution of their initial-value problem can be
achieved via algebraic operations, such as finding the eigenvalues of given
matrices or equivalently the zeros of known polynomials. Entirely isochronous
versions of some of these models are also exhibited: i.e., versions of these
models whose nonsingular solutions are all completely periodic with the same
period.Comment: 30 pages, 2 figure
On Integrable Quantum Group Invariant Antiferromagnets
A new open spin chain hamiltonian is introduced. It is both integrable
(Sklyanin`s type matrices are used to achieve this) and invariant under
transformations in nilpotent irreps for
. Some considerations on the centralizer of nilpotent
representations and its representation theory are also presented.Comment: IFF-5/92, 13 pages, LaTex file, 8 figures available from author
Ethical implications of onto-epistemological pluralism in relation to entropy,
From the epistemological posture that we present in this work we sustain the following thesis:-That as subjects we constitute the world we live in through one of the possible conceptual frameworks.-Our cognitive and social practices construct the world in a certain manner, which makes us responsible for the way this world is constituted
A dissipative algorithm for wave-like equations in the characteristic formulation
We present a dissipative algorithm for solving nonlinear wave-like equations
when the initial data is specified on characteristic surfaces. The dissipative
properties built in this algorithm make it particularly useful when studying
the highly nonlinear regime where previous methods have failed to give a stable
evolution in three dimensions. The algorithm presented in this work is directly
applicable to hyperbolic systems proper of Electromagnetism, Yang-Mills and
General Relativity theories. We carry out an analysis of the stability of the
algorithm and test its properties with linear waves propagating on a Minkowski
background and the scattering off a Scwharszchild black hole in General
Relativity.Comment: 23 pages, 7 figure
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