122277485
Beam test results from the SPAKEBAB electromagnetic calorimeter
Abstract We present the results of beam tests with high energy (6–150 GeV) electrons and muons of a new type of electromagnetic calorimeter, consisting of very thin interleaved lead and scintillator plates and read out by means of a large number of wavelength shifting fibers. A crucial feature of this detector is the absence of physical boundaries between the readout towers. We have measured the effects of crosstalk between cells that results from this feature and more common calorimeter properties such as the energy and position resolutions, signal linearity, signal uniformity and light yield. The results are among the very best ever obtained for sampling calorimeters.
109580082
The CMS pixel detector
The Compact Muon Solenoid Experiment (CMS) will start taking data at the Large Hadron Collider (LHC) in 2007 with the largest silicon tracking detector ever built. The central components of this tracker consist of two forward/backward pixel disks on each side of the interaction region and three barrel pixel layers. The silicon pixel detector will be crucial to pattern recognition and track reconstruction in the hadronic collisions of CMS and will play a key role in the physics program of the LHC. During the 2007 pilot physics run of the LHC, CMS will run with a subset of the final detector to be installed in 2008. In this report, the final design and results from test beam runs and expected performance of the detector are given. The expected radiation tolerance and projected lifetime of the pixel detector will be discussed as well its impact on the physics program of CMS.
14575890
Morphology of the large-scale structure
The Minkowski functionals are a mathematical tool to quantify morphological features of patterns. Some applications to the matter distribution in galaxy catalogues and N-body simulations are reviewed, with an emphasis on the effects of cosmic variance. The conclusions are that (i) the observed large-scale morphology is sensitive to cosmic variance on scales much larger than the nonlinear length (approx. 8 Mpc/h), and (ii) the large-scale morphology predicted by simulations is thus affected by finite-size effects, but nonetheless a Lambda-CDM model is favored.
2374089
Numerical study of the cosmological velocity field as a function of density
We report on a new study of the velocity distribution in N-body simulations. We investigate the center-of-mass and internal kinetic energies of coarsening cells as a function of time, cell size and cell mass. By using self-similar cosmological models, we are able to derive theoretical predictions for comparison and to assess the influence of finite-size and resolution effects. The most interesting result is the discovery of a polytropic-like relationship between the average velocity dispersion (internal kinetic energy) and the mass density in an intermediate range of densities, κint ∝ � 2−η . The exponent η measures the deviations from the virial prediction, ηvirial = 0. For self-similar models, η depends only on the spectral index of the initial power spectrum. We also study CDM models and confirm a previous result that the same polytropic-like dependence exists, with a time and coarsening length dependent η. The dependence κint(� ) is an important input for a recently proposed theoretical model of cosmological structure formation which improves over the standard dust model (pressureless fluid) by regularizing the density singularities.
42350703
Large quantum gravity effects and nonlocal variables
We reconsider here the model where large quantum gravity effects were first found, but now in its null surface formulation (NSF). We find that although the set of coherent states for Z, the basic variable of NSF, is as restricted as is the one for the metric, while some type of small deviations from these states may cause huge fluctuations on the metric, the corresponding fluctuations on Z remain small.
966351
The Fractal Distribution of Galaxies and the Transition to Homogeneity
There is an ongoing debate in cosmology about the value of the length scale at which "homogeneity" in the matter distribution is reached or even if such a scale exists. In the wake of this debate, we intend in this Letter to clarify the meaning of the statement transition to homogeneity and of the concept of correlation length. We show that there are two scales, each associated with the fractal and with the homogeneous regimes of the matter distribution, respectively. The distinction between both scales has deep consequences, for there can be a regime that, despite having small fluctuations around the average density, exhibits large clusters of galaxies.
18437289
Hydrodynamic approach to the evolution of cosmic structures – II. Study of N‐body simulations at z= 0
We present a series of cosmological N-body simulations which make use of the hydrodynamic approach to the evolution of structures. This approach addresses explicitly the existence of a finite spatial resolution and the dynamical effect of subresolution degrees of freedom. We adapt this method to cosmological simulations of the standard Lambda cold dark matter structure formation scenario and study the effects induced at redshift z= 0 by this novel approach on the large-scale clustering patterns as well as (individual) dark matter haloes. 
 
 
 
Comparing these simulations to usual N-body simulations, we find that (i) the new (hydrodynamic) model entails a proliferation of low-mass haloes and (ii) dark matter haloes have a higher degree of rotational support. These results agree with the theoretical expectation about the qualitative behaviour of the ‘correction terms’ introduced by the hydrodynamic approach: these terms act as a drain of inflow kinetic energy and a source of vorticity by the small-scale tidal torques and shear stresses.