Baryons and String Creation from the Fivebrane Worldvolume Action

We construct BPS-exact solutions of the worldvolume Born-Infeld plus WZW action of a D5-brane in the background of N D3-branes. The non-trivial background metric and RR five-form field strength play a crucial role in the solution. When a D5-brane is dragged across a stack of N D3-branes a bundle of N fundamental strings joining the two types of branes is created, as in the Hanany-Witten effect. Our solutions give a detailed description of this bundle in terms of a D5-brane wrapped on a sphere. We discuss extensions of these solutions which have an interpretation in terms of gauge theory multi-quark states via the AdS/CFT correspondence.Comment: LaTeX, 18 pages, 5 eps figures; v2: added reference which had been inadvertently omitte

A prototype for dS/CFT

We consider dS_2/CFT_1 where the asymptotic symmetry group of the de Sitter spacetime contains the Virasoro algebra. We construct representations of the Virasoro algebra realized in the Fock space of a massive scalar field in de Sitter, built as excitations of the Euclidean vacuum state. These representations are unitary, without highest weight, and have vanishing central charge. They provide a prototype for a new class of conformal field theories dual to de Sitter backgrounds in string theory. The mapping of operators in the CFT to bulk quantities is described in detail. We comment on the extension to dS_3/CFT_2.Comment: 17 pages, revtex

Baryons and Flux Tubes in Confining Gauge Theories from Brane Actions

We study baryon configurations in large N non-supersymmetric SU(N) gauge theories, applying the AdS/CFT correspondence. Using the D5-brane worldvolume theory in the near-horizon geometry of non-extremal D3-branes, we find embeddings which describe baryonic states in three-dimensional QCD. In particular, we construct solutions corresponding to a baryon made of N quarks, and study what happens when some fraction $\nu$ of the total number of quarks are bodily moved to a large spatial separation from the others. The individual clumps of quarks are represented by Born-Infeld string tubes obtained from a D5-brane whose spatial section has topology $R \times S^4$. They are connected by a confining color flux tube, described by a portion of the fivebrane that runs very close and parallel to the horizon. We find that this flux tube has a tension with a nontrivial $\nu$-dependence (not previously obtained by other methods). A similar picture is presented for the four-dimensional case.Comment: LaTeX, 20 pages, 6 eps figures; v2: added reference, corrected numerical error in Eqs. (13) and (23

Physical parameters of a relativistic jet at very high redshift: the case of the blazar J1430+4204

Context. The high-redshift (z = 4.72) blazar J1430+4204 produced a major radio outburst in 2005. Such outbursts are usually associated with the emergence of a new component in the inner radio jet. Aims. We searched for possible changes in the radio structure on milli-arcsecond angular scales, to determine physical parameters that characterise the relativistic jet ejected from the centre of this source. Methods. We analysed 15-GHz radio interferometric images obtained with the Very Long Baseline Array (VLBA) before and after the peak of the outburst. Results. We did not identify any significant new jet component over a period of 569 days. We estimated the Doppler factor, the Lorentz factor, and the apparent transverse speed of a putative jet component using three different methods. The likely small jet angle to the line of sight and our values of the apparent transverse speed are consistent with not detecting a new jet feature.Comment: (6 pages, 4 figures) accepted for publication in Astronomy and Astrophysic

Multifrequency VLBA Monitoring of 3C 273 during the INTEGRAL Campaign in 2003 - I. Kinematics of the Parsec Scale Jet from 43 GHz Data

In this first of a series of papers describing polarimetric multifrequency Very Long Baseline Array (VLBA) monitoring of 3C 273 during a simultaneous campaign with the INTEGRAL gamma-ray satellite in 2003, we present 5 Stokes I images and source models at 7 mm. We show that a part of the inner jet (1-2 milliarcseconds from the core) is resolved in a direction transverse to the flow, and we analyse the kinematics of the jet within the first 10 mas. Based on the VLBA data and simultaneous single-dish flux density monitoring, we determine an accurate value for the Doppler factor of the parsec scale jet, and using this value with observed proper motions, we calculate the Lorentz factors and the viewing angles for the emission components in the jet. Our data indicates a significant velocity gradient across the jet with the components travelling near the southern edge being faster than the components with more northern path. We discuss our observations in the light of jet precession model and growing plasma instabilities.Comment: Accepted for publication in Astronomy & Astrophysics, 16 pages, 15 figure

Blazar sequence - an artefact of Doppler boosting

The blazar sequence is a scenario in which the bolometric luminosity of the blazar governs the appearance of its spectral energy distribution. The most prominent result is the significant negative correlation between the synchrotron peak frequencies and the synchrotron peak luminosities of the blazar population. Observational studies of the blazar sequence have, in general, neglected the effect of Doppler boosting. We study the dependence of both the synchrotron peak frequency and luminosity with Doppler-corrected quantities. We determine the spectral energy distributions of 135 radio-bright AGN and find the best-fit parabolic function for the distribution to quantify their synchrotron emission. The corresponding measurements of synchrotron peak luminosities and frequencies are Doppler-corrected with a new set of Doppler factors calculated from variability data. The relevant correlations for the blazar sequence are determined for these intrinsic quantities. The Doppler factor depends strongly on the synchrotron peak frequency, the lower energy sources being more boosted. Applying the Doppler correction to the peak frequencies and luminosities annuls the negative correlation between the two quantities, which becomes positive. For BL Lacertae objects, the positive correlation is particularly strong. The blazar sequence, when defined as the anticorrelation between the peak frequency and luminosity of the synchrotron component of the spectral energy distribution, disappears when the intrinsic, Doppler-corrected values are used. It is an observational phenomenon created by variable Doppler boosting across the synchrotron peak frequency range.Comment: 9 pages, 5 figures + 2 tables. The published version with minor changes, the main conclusions are unchange

The milliarcsecond-scale jet of PKS 0735+178 during quiescence

We present polarimetric 5 GHz to 43 GHz VLBI observations of the BL Lacertae object PKS 0735+178, spanning March 1996 to May 2000. Comparison with previous and later observations suggests that the overall kinematic and structural properties of the jet are greatly influenced by its activity. Time intervals of enhanced activity, as reported before 1993 and after 2000 by other studies, are followed by highly superluminal motion along a rectilinear jet. In contrast the less active state in which we performed our observations, shows subluminal or slow superluminal jet features propagating through a twisted jet with two sharp bends of about 90 deg. within the innermost three-milliarcsecond jet structure. Proper motion estimates from the data presented here allow us to constrain the jet viewing angle to values < 9 deg., and the bulk Lorentz factor to be between 2 and 4.Comment: 11 pages, 12 figures. Accepted for publication in A&

Statistical entropy of three-dimensional q-deformed Kerr-de Sitter space

A quantum deformation of three-dimensional de Sitter space was proposed in hep-th/0407188. We use this to calculate the entropy of Kerr-de Sitter space, using a canonical ensemble, and find agreement with the semiclassical result.Comment: 11 pages, revtex, (v2, reference added