A5015204838- Cosmology and Gravitation Theories
- Galaxies: Formation, Evolution, Phenomena
- Scientific Research and Discoveries
- Space exploration and regulation
- Science, Research, and Medicine
- Astronomy and Astrophysical Research
- History and Developments in Astronomy
- Radio Astronomy Observations and Technology
- Healthcare Systems and Practices
- Space Science and Extraterrestrial Life
- Dark Matter and Cosmic Phenomena
- Geophysics and Gravity Measurements
- Relativity and Gravitational Theory
- Health and Medical Research Impacts
- Advances in Oncology and Radiotherapy
- Complex Systems and Time Series Analysis
- Advanced Thermodynamics and Statistical Mechanics
- Black Holes and Theoretical Physics
- HIV/AIDS Impact and Responses
- Biotechnology and Related Fields
- International Science and Diplomacy
- Global Public Health Policies and Epidemiology
- Advanced Differential Geometry Research
- Solar and Space Plasma Dynamics
- Statistical Mechanics and Entropy
University of Nottingham
2001-2022
National University of Ireland, Maynooth
2009-2022
Cardiff University
2007-2017
University of Sussex
1986-2016
Stanford University
2015
Boston Public Library
2015
University of Zurich
2015
Netherlands Institute for Radio Astronomy
2007-2012
Goldsmiths University of London
2012
Queen Mary University of London
1992-2008
We discuss the use of a lognormal (LN) random field as model for distribution matter in Universe. find number reasons why this should be plausible approximation to density irregularities obtained by evolving from Gaussian initial conditions. Unlike straightforward linear theory, always has |$\rho\gt0$| but is arbitrarily close at early times. It added advantage that, like model, all its statistical properties can formulated terms one covariance function.
The Herschel ATLAS is the largest open-time key project that will be carried out on Space Observatory. It survey 510 square degrees of extragalactic sky, four times larger than all other surveys combined, in five far-infrared and submillimetre bands. We describe survey, complementary multi-wavelength datasets combined with data, six major science programmes we are undertaking. Using new models based a previous galaxies, present predictions properties sources wavebands.
PART I: Cosmological Methods The Relativistic Universe Friedmann Models Alternative Cosmologies: Past and Present Observational Properties of the Universe. II: Evolution Big Bang Model Physical Hot Quantum Gravity Phase Transitions Inflation Hadron Lepton Eras Plasma Era. III: Structure Formation by Gravitational Instability Introduction to Jeans in Origin Baryons Only Non-Baryonic Matter Perturbations Non-Linear Perturbations. IV: Test Statistics Galaxy Clustering Cosmic Microwave...
We discuss how the redshift dependence of observed two-point correlation function various classes objects can be related to theoretical predictions. This relation involves first a calculation evolution underlying matter correlations. The next step is relate fluctuations in mass those any particular class cosmic objects; general terms, this means model for bias and it evolves with epoch. Only after these two effects have been quantified one perform an appropriate convolution non-linearly...
We investigate the accuracy of various analytic approximations for following evolution cosmological density fluctuations into non-linear regime. compare results application linear theory, lognormal approximation and Zeldovich to a set initial data with corresponding obtained by full three-dimensional N-body computation from same conditions. A cross-correlation technique is used quantify agreement between approximated 'final' distributions different power spectra, normalization epochs degrees...
The relationship between galaxies (i.e., luminous objects) and the cosmological mass density field is discussed. A generalization of idea biased galaxy formation introduced, in which form with a probability given by an arbitrary function local density. Constraints, inequalities, on various statistical measures clustering are derived, do not depend upon this or underlying distribution fluctuations. Stronger constraints can be achieved if one specifies statistics. In particular, it shown that...
We present an analysis of the Minkowski Functionals (MFs) describing WMAP three-year temperature maps to place limits on possible levels primordial non-Gaussianity.In particular, we apply perturbative formulae for MFs give constraints usual non-linear coupling constant f NL .The theoretical predictions are found agree with simulated CMB including full effects radiative transfer.The agreement is also very good even when simulation include various observational artifacts, pixel window...
We study the statistical properties of spherical harmonic modes temperature maps cosmic microwave background. Unlike other studies, which focus mainly on amplitudes these modes, we look instead at their phases. In particular, present a simple measure phase correlation that can be diagnostic departures from standard assumption primordial density fluctuations constitute statistically homogeneous and isotropic Gaussian random field, should possess phases are uniformly unit circle. The method...
We investigate some aspects of the statistical geometry 2D random fields relevant to studies temperature anisotropics in microwave background. extend work Coles & Barrow calculate expectation values Euler–Poincaré characteristic excursion sets Gaussian and non-Gaussian above various threshold levels. Monte Carlo simulations possessing covariance function expected CDM models are used assess usefulness this, other, pattern statistics as discriminators between hence primordial fluctuations....
With the successful launch of European Space Agency's Planck satellite earlier this year cosmic microwave background (CMB) is once again centre attention for cosmologists around globe. Since its accidental discovery in 1964 by Arno Penzias and Robert Wilson, relic Big Bang has been subjected to intense scrutiny generation after experiments gradually yielded up answers deepest questions about origin our Universe. Most recently, Wilkinson Microwave Anisotropy Probe (WMAP) made a full-sky...
We present a new harmonic-domain-based approach for extracting morphological information, in the form of Minkowski functionals (MFs), from weak-lensing convergence maps. Using perturbative expansion MFs, which is expected to be valid range angular scales probed by most current surveys, we show that study three generalized skewness parameters equivalent MFs defined 2D. then extend these associated skew spectra carry more information about bispectrum than their one-point counterparts. discuss...
Short-term shifts in booking behaviors can disrupt forecasting the travel and hospitality industry, especially during global crises. Traditional metrics like average or median lead times often overlook important distribution changes. This study introduces a normalized L1 (Manhattan) distance to assess Airbnb time divergences from 2018 2022, focusing on COVID-19 pandemic across four major U.S. cities. We identify two-phase disruption: an abrupt change at pandemic's onset followed by partial...
This thesis explores the application of differential geometric and general relativistic techniques to deepen our understanding quantum mechanical systems. We focus on three systems, employing these mathematical frameworks uncover subtle features within each. First, we examine Unruh radiation in context an accelerated two-state atom, determining transition frequencies for a variety trajectories via first-order perturbation theory. For harmonic motion atom vacuum, derive rates with potential...
We discuss the theoretical interpretation of observational data concerning clustering galaxies at high redshifts.Building on machinery developed by Matarrese et al., we make detailed quantitative predictions galaxy statistics for a variety cosmological models, taking into account differences in spatial geometry and initial fluctuation spectra exploring role bias as complicating factor these calculations.We demonstrate that usual description evolution (in terms parameters e r 0 ) is not...
We use recent COBE observational limits on departures of the spectrum cosmic microwave background (CMB) from a pure blackbody curve to constrain models galaxy formation. The damping adiabatic density perturbations at high redshifts |$(z\sim{10}^{5})$| injects energy into primordial plasma which cannot be thermalized and therefore distorts CMB spectrum. find that we can eliminate flat |$(\Omega_{0} = 1)$| baryon-dominated with power-law fluctuations having n > 4 open 0.1)$| baryonic 1....
The Fourier transform of cosmological density perturbations can be represented in terms amplitudes and phases for each mode. We investigate the phase evolution these modes using a mixture analytical numerical techniques. Using toy model one-dimensional evolving under Zel'dovich approximation as an initial motivation, we develop statistic that quantifies information content distribution phases. simulations beginning with more realistic Gaussian random-phase conditions, show grows from zero...
We examine the production of tensor (gravitational wave) perturbations in a universe where inflation is driven by scalar field interacting via an exponential potential. In such scenario, Universe undergoes power-law rather than expansion, and density have but non-scale-invariant spectrum. show that models which lead to only slight departures from scale-invariant also produce significant gravitational wave anisotropics cosmic microwave background. For spectral index n < 0.83, more half...
We study the effect of primordial non-Gaussianity on development large-scale cosmic structure using high-resolution N-body simulations. In particular, we focus topological properties "cosmic web", quantitatively characterized by Minkowski Functionals, for models with quadratic non-linearities different values usual parameter fNL. weakly non-linear regime, find that analytic formulae derived from perturbation theory agree numerical results within a few percent amplitude each MF when...
Motivated by recent suggestions that a number of observed galaxy clusters have masses which are too high for their given redshift to occur naturally in standard model cosmology, we use Extreme Value Statistics construct confidence regions the mass-redshift plane most extreme objects expected universe. We show how such diagram not only provides way potentially ruling out concordance but also allows us differentiate between alternative models enhanced structure formation. compare our...