119760521
On the intrinsic labeling of space‐times: a characterization of the Kerr solution
The interest of obtaining an intrinsic (depending solely on the metric tensor) and fully explicit characterization of a space‐time is pointed out. We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve concomitants of the Weyl tensor.
118782909
Positioning systems in Minkowski spacetime: from emission to inertial coordinates
The coordinate transformation between emission coordinates and inertial coordinates in Minkowski spacetime is obtained for arbitrary configurations of the emitters. It appears that a positioning system always generates two different coordinate domains, namely, the front and the back emission coordinate domains. For both domains, the corresponding covariant expression of the transformation is explicitly given in terms of the emitter world lines. This task requires the notion of the orientation of an emitter configuration. The orientation is shown to be computable from the emission coordinates for the users of a 'central' region of the front emission coordinate domain. Other spacetime regions associated with the emission coordinates are also outlined.
118720389
Obtaining the Weyl tensor from the Bel–Robinson tensor
The algebraic study of the Bel–Robinson tensor proposed and initiated in a previous work (Ferrando and Sáez in Gen Relativ Gravit 41:1695–1715, 2009) is achieved. The canonical form of the different algebraic types is obtained in terms of Bel–Robinson eigen-tensors. An algorithmic determination of the Weyl tensor from the Bel–Robinson tensor is presented.
118521043
An intrinsic characterization of spherically symmetric spacetimes
We give the necessary and sufficient (local) conditions for a metric tensor to be a nonconformally flat spherically symmetric solution. These conditions exclusively involve explicit concomitants of the Riemann tensor. As a direct application we obtain the ideal labeling of the Schwarzschild, Reissner–Nordstrom and Lemaitre–Tolman–Bondi solutions.
6470358
Aligned Electric and Magnetic Weyl Fields
The results on the non-existence of purely magnetic solutions are extended to the wider class of spacetimes which have homothetic electric and magnetic Weyl fields. This class is a particularization of the spacetimes admitting a direction for which the relative electric and magnetic Weyl fields are aligned. We give an invariant characterization of these metrics and study the properties of their Debever null vectors. The directions ‘observing’ aligned electric and magnetic Weyl fields are obtained for every Petrov-Bel type.
14972296
Vacuum type I spacetimes and aligned Papapetrou fields: symmetries
We analyse type I vacuum solutions admitting an isometry whose Killing 2-form is aligned with a principal bivector of the Weyl tensor, and we show that these solutions belong to a family of type I metrics which admit a group G3 of isometries. We give a classification of this family and study the Bianchi type for each class. The classes compatible with an aligned Killing 2-form are also determined. The Szekeres–Brans theorem is extended to non-vacuum spacetimes with vanishing Cotton tensor.
123672736
Forward jet production in deep inelastic ep scattering and low-x parton dynamics at HERA
Abstract Differential inclusive jet cross sections in neutral current deep inelastic ep scattering have been measured with the ZEUS detector using an integrated luminosity of 38.7 pb −1 . The jets have been identified using the k T cluster algorithm in the longitudinally invariant inclusive mode in the laboratory frame; they have been selected with jet transverse energy, E T jet above 6 GeV and jet pseudorapidity, η jet , between −1 and 3. Measurements of cross sections as functions of E T jet , Bjorken x and the photon virtuality, Q 2 , are presented. Three phase-space regions have been selected in order to study parton dynamics from the most global to the most restrictive region of forward-going (close to the proton-beam direction) jets at low x , where the effects of BFKL evolution might be present. The measurements have been compared to the predictions of leading-logarithm parton-shower Monte Carlo models and fixed-order perturbative QCD calculations. In the forward region, O ( α s 1 ) QCD calculations underestimate the data up to an order of magnitude at low x . An improved description of the data in this region is obtained by including O ( α s 2 ) QCD corrections, which account for the lowest-order t ˆ -channel gluon-exchange diagrams, highlighting the importance of such terms in the parton dynamics at low x .
15330351
Subjet distributions in deep inelastic scattering at HERA
Subjet distributions were measured in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb−1. Jets were identified using the kT cluster algorithm in the laboratory frame. Subjets were defined as jet-like substructures identified by a reapplication of the cluster algorithm at a smaller value of the resolution parameter $y_{\rm cut}$. Measurements of subjet distributions for jets with exactly two subjets for $y_{\rm cut}=0.05$ are presented as functions of observables sensitive to the pattern of parton radiation and to the colour coherence between the initial and final states. Perturbative QCD predictions give an adequate description of the data.
15550947
Measurement of diffractive production of D*+- (2010) mesons in deep inelastic scattering at HERA
Abstract Diffractive production of D ∗± (2010) mesons in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 44.3 pb −1 . Diffractive charm production is identified by the presence of a large rapidity gap in the final state of events in which a D ∗± (2010) meson is reconstructed in the decay channel D ∗+ →(D 0 →K − π + )π + s (+ charge conjugate). Differential cross sections when compared with theoretical predictions indicate the importance of gluons in such diffractive interactions.
126420285
Table 55 ; Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at $\sqrt{s_{NN}}=2.76$ TeV with the ATLAS detector
62786869
Measurement of isolated photons accompanied by jets in deep inelastic ep scattering
The production of isolated high-energy photons accompanied by jets has been measured in deep inelastic ep scattering with the ZEUS detector at HERA, using an integrated luminosity of 326pb -1 . Measurements were made for exchanged photon virtualities, Q 2 , in the range 10 to 350GeV 2 . The photons were measured in the transverse-energy and pseudorapidity ranges 4 γ jet <1.8. Differential cross sections are presented as functions of these quantities. Perturbative QCD predictions give a reasonable description of the shape of the measured cross sections over most of the kinematic range, but the absolute normalisation is typically in disagreement by 20-30%. © 2012 Elsevier B.V.