Primordial Feature at the Scale of Superclusters of Galaxies

We investigate a spatially-flat cold dark matter model (with the matter density parameter $\Omega_m=0.3$) with a primordial feature in the initial power spectrum. We assume that there is a bump in the power spectrum of density fluctuations at wavelengths $\lambda \sim 30-60h^{-1}$Mpc, which correspond to the scale of superclusters of galaxies. There are indications for such a feature in the power spectra derived from redshift surveys and also in the power spectra derived from peculiar velocities of galaxies. We study the mass function of clusters of galaxies, the power spectrum of the CMB temperature fluctuations, the rms bulk velocity and the rms peculiar velocity of clusters of galaxies. The baryon density is assumed to be consistent with the BBN value. We show that with an appropriately chosen feature in the power spectrum of density fluctuations at the scale of superclusters, the mass function of clusters, the CMB power spectrum and peculiar velocities are in good agreement with the observed data.Comment: 8 pages, 6 figures, with final revisions, MNRAS in press, new CMB data adde

Velocity Correlations of Galaxy Clusters

We determine the velocity correlation function, pairwise peculiar velocity difference, and root-mean-square pairwise peculiar velocity dispersion of rich clusters of galaxies, as a function of pair separation, for three cosmological models: Omega=1 and Omega=0.3 CDM, and Omega=0.3 PBI models (all flat and COBE-normalized). We find that close cluster pairs, with separation r<10Mpc/h, exhibit strong attractive peculiar velocities in all models; the cluster pairwise velocities depend sensitively on the model. The mean pairwise attractive velocity of clusters on 5Mpc/h scale ranges from 1700 km/s for Omega=1 CDM, to 1000 km/s for PBI, to 700 km/s for Omega=0.3 CDM. The small-scale pairwise velocities depend also on cluster mass: richer, more massive clusters exhibit stronger attractive velocities than less massive clusters. On large scales, from 20 to 200Mpc/h, the cluster peculiar velocities are increasingly dominated by bulk and random motions; they are independent of cluster mass. The cluster velocity correlation function, which reflects the bulk motion minus the relative motion of pairs, is negative on small scales for Omega=1 and Omega=0.3 CDM, and positive for PBI; this indicates stronger pairwise motion than bulk motion on small scales for CDM, and relatively larger bulk motions for PBI. The cluster velocity correlation function is positive on very large scales, from 10 to 200Mpc/h, for all models. These positive correlations, which decrease monotonically with scale, indicate significant bulk motions of clusters up to 200Mpc/h. The strong dependence of the cluster velocity functions on models, especially at small separations, makes them useful tools in constraining cosmological models when compared with observations.Comment: 12p postscript file, in press of The Astrophysical Journal Letters Local report# 94915,email: [email protected]

The Motions of Clusters and Groups of Galaxies

The distributions of peculiar velocities of rich clusters and of groups of galaxies are investigated for different cosmological models and are compared with observations. Four cosmological models are studied: standard ($\Omega=1$) CDM, low-density CDM, HDM ($\Omega=1$), and PBI. We find that rich clusters of galaxies exhibit a Maxwellian distribution of peculiar velocities in all models, as expected from a Gaussian initial density fluctuation field. The cluster 3-D velocity distribution is generally similar in the models: it peaks at $v \sim 500$ km s$^{-1}$, and extends to high cluster velocities of $v \sim 1500$ km s$^{-1}$. Approximately 10\% of all model rich clusters move with high peculiar velocities of $v \ge 10^3$ km s$^{-1}$. The highest velocity clusters frequently originate in dense superclusters. The group velocity distribution is, in general, similar to the velocity distribution of the rich clusters. In all but the low-density CDM model, the mass exhibits a longer tail of high velocities than do the clusters. This high-velocity tail originates mostly from the high velocities that exist within rich clusters. The model velocity distributions of groups and clusters of galaxies are compared with observations. The data are generally consistent with the models, but exhibit a somewhat larger high-velocity tail, to $v_r \sim 3000$ km s$^{-1}$. While this high-velocity tail is similar to the HDM model predictions, the data are consistent with the other models studied, including the low-density CDM model, which best fits most other large-scale structure observations. The observed velocityComment: 25p plaintex submitted to The Astrophysical Journa

Compositions portfolio commentary

For this submission, I have included a commentary on the works I have written over the last two years and a CD of recordings of most of the works in the portfolio. The commentary shows the development I have made as a composer: moving from an initially fairly conventional style of composing, with an emphasis on rhythmic drive and melody, to a polystylist approach to composition - whereby I try to combine a myriad of influences in my work, and to a style of music that is more focussed on timbre, sonority and texture. I also decided to continue to develop and explore the possibilities of writing contemporary music for amateurs. The works range from pieces written for specific ensembles for workshops at Birmingham University, such as the Hermes Ensemble (‘$Jimi$’), The Birmingham Contemporary Music Group (‘$Fragments$’) and EXAUDI ($Yo$ $volveré$) to works written for local projects in Germany. The first set of songs ($The$ $Climate$ $Change$ $Songs$) was written for a singer in Potsdam, Angela Baier- Banthien. Walpurgisnacht was written as part of a project with a group of local contemporary composers, which ultimately led to the publication of one of the oboe duets as part of a compendium of works together with the other composers. One Day was commissioned by the jazz saxophonist, Lars Stoermer and played by him on the accompanying CD. $Beck’s$ $Dream$ was written for and performed by the guitarist Martin Milner. $Fragile$ $Planet$ was written for the pianist Mamiko Wada and played by Susan Handy on the accompanying CD. The total length of the submission is approximately 47 minutes and is comprised of 13 contrasting works

Investigating established EEG parameter during real-world driving

© 2018 Protzak and Gramann. In real life, behavior is influenced by dynamically changing contextual factors and is rarely limited to simple tasks and binary choices. For a meaningful interpretation of brain dynamics underlying more natural cognitive processing in active humans, ecologically valid test scenarios are essential. To understand whether brain dynamics in restricted artificial lab settings reflect the neural activity in complex natural environments, we systematically tested the auditory event-related P300 in both settings. We developed an integrative approach comprising an initial P300-study in a highly controlled laboratory set-up and a subsequent validation within a realistic driving scenario. Using a simulated dialog with a speech-based input system, increased P300 amplitudes reflected processing of infrequent and incorrect auditory feedback events in both the laboratory setting and the real world setup. Environmental noise and movement-related activity in the car driving scenario led to higher data rejection rates but revealed comparable theta and alpha frequency band pattern. Our results demonstrate the possibility to investigate cognitive functions like context updating in highly artifact prone driving scenarios and encourage the consideration of more realistic task settings in prospective brain imaging approaches

Steps toward the power spectrum of matter. II. The biasing correction with sigma_8 normalization

A new method to determine the bias parameter of galaxies relative to matter is suggested. The method is based on the assumption that gravity is the dominating force which determines the formation of the structure in the Universe. Due to gravitational instability the galaxy formation is a threshold process: in low-density environments galaxies do not form and matter remains in primordial form. We investigate the influence of the presence of void and clustered populations to the power spectrum of matter and galaxies. The power spectrum of galaxies is similar to the power spectrum of matter; the fraction of total matter in the clustered population determines the difference between amplitudes of fluctuations of matter and galaxies, i.e. the bias factor. To determine the fraction of matter in voids and clustered population we perform numerical simulations. The fraction of matter in galaxies at the present epoch is found using a calibration through the sigma_8 parameter.Comment: LaTex (sty files added), 31 pages, 4 PostScript figures embedded, Astrophysical Journal (accepted