16,996 research outputs found
The extremely asymmetric radio structure of the z=3.1 radio galaxy B3 J2330+3927
We report on 1.7 and 5.0 GHz observations of the z=3.087 radio galaxy B3
J2330+3927, using the Very Long Baseline Array (VLBA), and archival 1.4 and 8.4
GHz Very Large Array (VLA) data. Our VLBA data identify a compact, flat
spectrum (\alpha_{1.7 GHz}^{5 GHz} = -0.2 +/- 0.1; S_\nu ~ \nu^\alpha) radio
component as the core. The VLA images show that the fraction of core emission
is very large (f_c \approx 0.5 at 8.4 GHz), and reveal a previously undetected,
very faint counterjet, implying a radio lobe flux density ratio R >= 11 and a
radio lobe distance ratio Q \approx 1.9. Those values are much more common in
quasars than in radio galaxies, but the optical/near-IR spectra show a clear
type II AGN for B3 J2330+3927, confirming that it is indeed a radio galaxy.
Unlike all other radio galaxies, the bright Ly-\alpha emitting gas is located
towards the furthest radio arm. We argue against environmental and relativistic
beaming effects being the cause of the observed asymmetry, and suggest this
source has intrinsically asymmetric radio jets. If this is the case, B3
J2330+3927 is the first example of such a source at high redshift, and seems to
be difficult to reconcile with the unified model, which explains the
differences between quasars and radio galaxies as being due to orientation
effects.Comment: 6 pages, 3 figures, to appear as a Letter to MNRA
End-point estimates for iterated commutators of multilinear singular integrals
Iterated commutators of multilinear Calderon-Zygmund operators and pointwise
multiplication with functions in are studied in products of Lebesgue
spaces. Both strong type and weak end-point estimates are obtained, including
weighted results involving the vectors weights of the multilinear
Calderon-Zygmund theory recently introduced in the literature. Some better than
expected estimates for certain multilinear operators are presented too.Comment: A typo in the original manuscript lead to overlook a gap in one of
our arguments which has been fixed. The new arguments are provided in the
proof of Theorem 3.1 in Section 3. With the exception of some new notation
introduced and some minor changes in wording in a few places, those new
details are the only modifications to the original manuscrip
The multilinear strong maximal function
A multivariable version of the strong maximal function is introduced and a
sharp distributional estimate for this operator in the spirit of the Jessen,
Marcinkiewicz, and Zygmund theorem is obtained. Conditions that characterize
the boundedness of this multivariable operator on products of weighted Lebesgue
spaces equipped with multiple weights are obtained. Results for other
multi(sub)linear maximal functions associated with bases of open sets are
studied too. Certain bilinear interpolation results between distributional
estimates, such as that obtained for the multivariable strong maximal function,
are also proved.Comment: appeared in J. of Geometric Ana
Stabilization of solitons of the multidimensional nonlinear Schrodinger equation: Matter-wave breathers
We demonstrate that stabilization of solitons of the multidimensional
Schrodinger equation with a cubic nonlinearity may be achieved by a suitable
periodic control of the nonlinear term. The effect of this control is to
stabilize the unstable solitary waves which belong to the frontier between
expanding and collapsing solutions and to provide an oscillating solitonic
structure, some sort of breather-type solution. We obtain precise conditions on
the control parameters to achieve the stabilization and compare our results
with accurate numerical simulations of the nonlinear Schrodinger equation.
Because of the application of these ideas to matter waves these solutions are
some sort of matter breathers
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