Durham University

About: Durham University is a education organization based out in Durham, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 39385 authors who have published 82311 publications receiving 3110994 citations. The organization is also known as: University of Durham & Gallery of Durham University.

Active Vision: The Psychology of Looking and Seeing

Abstract: PASSIVE VISION AND ACTIVE VISION 1.1 Introduction 1.2 Passive vision 1.3 Visual attention 1.4 Active vision 1.5 Active vision and vision for action 1.6 Outline of the book BACKGROUND TO ACTIVE VISION 2.1 Introduction 2.2 The inhomogeneity of the visual projections 2.3 Parallel visual pathways 2.4 The oculomotor system 2.5 Saccadic eye movements 2.6 Summary VISUAL SELECTION, COVERT ATTENTION AND EYE MOVEMENTS 3.1 Covert and overt attention 3.2 Covert spatial attention 3.3 The relationship between covert and overt attention 3.4 Speed of attention 3.5 Neurophysiology of attention 3.6 Non-spatial attention 3.7 Active vision and attention 3.8 Summary VISUAL ORIENTING 4.1 Introduction 4.2 What determines the latency of orienting saccades? 4.3 Physiology of saccade initiation 4.4 What determines the landing position of orienting saccades? 4.5 Physiology of the WHERE system 4.6 The Findlay and Walker model 4.7 Development and plasticity VISUAL SAMPLING DURING TEXT READING 5.1 Introduction 5.2 Basic patterns of visual sampling during reading 5.3 Perception during fixations in reading 5.4 Language processing 5.5 Control of fixation duration 5.6 Control of landing position 5.7 Theories of eye control during reading 5.8 Practical aspects of eye control in reading 5.9 Overview VISUAL SEARCH 6.1 Visual search tasks 6.2 Theories of visual search 6.3 The need for eye movements in visual search 6.4 Eye movements in visual search 6.5 Ocular capture in visual search 6.6 Saccades in visual search: scanpaths 6.7 Physiology of visual search 6.8 Summary NATURAL SCENES AND ACTIVITIES 7.1 Introduction 7.2 Analytic studies of scene and object perception 7.3 Dynamic scenes and situations 7.4 Summary HUMAN NEUROPSYCHOLOGY 8.1 Blindsight 8.2 Neglect 8.3 Balint's syndrome and dorsal simultanagnosia 8.4 Frontal lobe damage 8.5 Orienting without eye movements 8.6 Summary SPACE CONSTANCY AND TRANS-SACCADIC INTEGRATION 9.1 The traditional approach: 'compensatory taking into account' 9.2 Trans-saccadic integration 9.3 Resolution of the conflicting results 9.4 Conclusion: The Active Vision Cycle 9.5 Future directions

The statistics of LCDM Halo Concentrations

Abstract: We use the Millennium Simulation (MS) to study the statistics of LCDM halo concentrations at z = 0. Our results confirm that the average halo concentration declines monotonically with mass; a power-law fits well the concentration-mass relation for over 3 decades in mass, up to the most massive objects to form in a LCDM universe (~ 10^15 h^-1 Msol). This is in clear disagreement with the predictions of the model proposed by Bullock et al. for these rare objects, and agrees better with the original predictions of Navarro, Frenk, & White. The large volume surveyed, together with the unprecedented numerical resolution of the MS, allow us to estimate with confidence the distribution of concentrations and, consequently, the abundance of systems with unusual properties. About one in a hundred cluster haloes (M200 >~ 3x10^14 h^-1 Msol) have concentrations exceeding c200 = 7.5, a result that may be used to interpret the likelihood of unusually strong massive gravitational lenses, such as Abell 1689, in the LCDM cosmogony. A similar fraction (1 in 100) of galaxy-sized haloes (M200 ~ 10^12 h^-1 Msol) have c200 < 4.5, an important constraint on models that attempt to reconcile the rotation curves of low surface-brightness galaxies by appealing to haloes of unexpectedly low concentration. We find that halo concentrations are independent of spin once haloes manifestly out of equilibrium are removed from the sample. Compared to their relaxed brethren, the concentrations of out-of-equilibrium haloes tend to be lower and to have more scatter, while their spins tend to be higher... (continue)

A Universal Density Profile from Hierarchical Clustering

Abstract: We use high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes. We find that all such profiles have the same shape, independent of halo mass, of initial density fluctuation spectrum, and of the values of the cosmological parameters. Spherically averaged equilibrium profiles are well fit over two decades in radius by a simple formula originally proposed to describe the structure of galaxy clusters in a cold dark matter universe. In any particular cosmology the two scale parameters of the fit, the halo mass and its characteristic density, are strongly correlated. Low-mass halos are significantly denser than more massive systems, a correlation which reflects the higher collapse redshift of small halos. The characteristic density of an equilibrium halo is proportional to the density of the universe at the time it was assembled. A suitable definition of this assembly time allows the same proportionality constant to be used for all the cosmologies that we have tested. We compare our results to previous work on halo density profiles and show that there is good agreement. We also provide a step-by-step analytic procedure, based on the Press-Schechter formalism, which allows accurate equilibrium profiles to be calculated as a function of mass in any hierarchical model.