Rowing and the Same-Sum Problem Have Their Moments (2009)
We consider the optimal positioning of an even number of crew members in a coxless racing boat in order to avoid the presence of a sideways wiggle as the boat is propelled forwards through the water....
On the Stability of Static Ghost Cosmologies (2009)
Barrow, John D, Tsagas, Christos G
We consider the linear stability of a static universe filled with a non-interacting mixture of isotropic radiation and a ghost scalar field. Unlike the conventional Einstein static model, this...
Does Bulk Viscosity Create a Viable Unified Dark Matter Model? (2009)
We investigate in detail the possibility that a single imperfect fluid with bulk viscosity can replace the need for separate dark matter and dark energy in cosmological models. With suitable choices...
The Classical Stability of Sudden and Big Rip Singularities (2009)
Barrow, John D., Lip, Sean Z. W.
We introduce a general characterisation of sudden cosmological singularities and investigate the classical stability of homogeneous and isotropic cosmological solutions of all curvatures containing...
Varying-Alpha Cosmologies with Potentials (2008)
We generalize the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model for the variation of the fine structure 'constant', $\alpha ,$ to include an exponential or inverse power-law self-potential for the...
Quantum Particle Production at Sudden Singularities (2008)
Barrow, John D., Batista, Antonio B., Fabris, Julio C., Houndjo, Stephane
We investigate the effects of quantum particle production on a classical sudden singularity occurring at fine time in a Friedmann universe. We use an exact solution to describe an initially...
Varying Alpha: New Constraints from Seasonal Variations (2008)
Barrow, John D., Shaw, Douglas J.
We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they are strengthened...
Testing Alternative Theories of Dark Matter with the CMB (2008)
Li, Baojiu, Barrow, John D., Mota, David F., Zhao, HongSheng
We propose a method to study and constrain modified gravity theories for dark matter using CMB temperature anisotropies and polarization. We assume that the theories considered here have already...
Slow decay of magnetic fields in open Friedmann universes (2008)
Barrow, John D., Tsagas, Christos G.
We describe how magnetic fields in Friedmann universes can experience superadiabatic growth without departing from conventional electromagnetism. The reason is the relativistic coupling between...
The Constants of Nature (2008)
Just Six Numbers, Reviewed Brian, E. Blank, John D. Barrow, Just Six Numbers, Martin Rees
Consider the two constants G and G. The first G arises frequently when we manipulate special functions. We represent this G by dozens of series and integrals, we study its continued fraction...
The Stability of an Isotropic Cosmological Singularity in Higher-Order Gravity (2008)
Middleton, Jonathan, Barrow, John D.
We study the stability of the isotropic vacuum Friedmann universe in gravity theories with higher-order curvature terms of the form $(R_{ab}R^{ab})^{n}$ added to the Einstein-Hilbert Lagrangian of...
Some Late-time Asymptotics of General Scalar-Tensor Cosmologies (2007)
Barrow, John D., Shaw, Douglas J.
We study the asymptotic behaviour of isotropic and homogeneous universes in general scalar-tensor gravity theories containing a p=-rho vacuum fluid stress and other sub-dominant matter stresses. It...
Can Inflation be Falsified? (2007)
John Barrow And, John D. Barrow, Andrew R. Liddle
Despite its central role in modern cosmology, doubts are often expressed as to whether cosmological inflation is really a falsifiable theory. We distinguish two facets of inflation, one as a theory...
Generalised Scalar Field Potentials and Inflation (2007)
Paul Parsons, John D. Barrow, Brighton Bn Qh
We investigate the range of inflationary universe models driven by scalar fields possessing a general interaction potential of the form V (OE) = V 0 OE n exp(\GammaOE m ). Power-law, de Sitter and...
A Gauge-invariant Analysis of Magnetic Fields in General Relativistic Cosmology (2007)
Christos G. Tsagas, John D. Barrow
We provide a fully general-relativistic treatment of cosmological perturbations in a universe permeated by a large-scale primordial magnetic field using the Ellis-Bruni gauge-invariant formalism. The...
Detecting a Lorentz-Violating Field in Cosmology (2007)
Li, Baojiu, Mota, David F., Barrow, John D.
We consider cosmology in the Einstein-aether theory (the generally covariant theory of gravitation coupled to a dynamical timelike Lorentz-violating vector field) with a linear aether-Lagrangian. The...
The Cosmology of Ricci-Tensor-Squared Gravity in the Palatini Variational Approach (2007)
Li, Baojiu, Barrow, John D., Mota, David F.
We consider the cosmology of the Ricci-tensor-squared gravity in the Palatini variational approach. The gravitational action of standard general relativity is modified by adding a function...
Dynamics of Logamediate Inflation (2007)
A computation of the inflationary observables n_{s} and r is made for `logamediate' inflation where the cosmological scale factor expands as $a=\exp (A(\ln t)^{\lambda})$, and is compared to their...
The Cosmology of Modified Gauss-Bonnet Gravity (2007)
Li, Baojiu, Barrow, John D., Mota, David F.
We consider the cosmology where some function f(G) of the Gauss-Bonnet term G is added to the gravitational action to account for the late-time accelerating expansion of the universe. The covariant...
Stable Isotropic Cosmological Singularities in Quadratic Gravity (2007)
Barrow, John D., Middleton, Jonathan
We show that, in quadratic lagrangian theories of gravity, isotropic cosmological singularities are stable to the presence of small scalar, vector and tensor inhomogeneities. Unlike in general...
The Cosmology of f(R) Gravity in the Metric Variational Approach (2007)
We consider the cosmologies that arise in a subclass of f(R) gravity with f(R)=R+\mu ^{2n+2}/(-R)^{n} and -1
The Ups and Downs of Cyclic Universes (2007)
We investigate homogeneous and isotropic oscillating cosmologies with multiple fluid components. Transfer of energy between these fluids is included in order to model the effects of non-equilibrium...
We introduce some early considerations of physical and mathematical impossibility as preludes to the Goedel incompleteness theorems. We consider some informal aspects of these theorems and their...
A Strong Constraint on Ever-Present Lambda (2006)
We show that the causal set approach to creating an ever-present cosmological 'constant' in the expanding universe is strongly constrained by the isotropy of the microwave background. Fluctuations...
Barrow, John D., Tsagas, Christos G.
We consider the brane-world generalization of the Gφdel universe and analyze its dynamical interaction with the bulk. The exact homogeneity of the standard Gφdel spacetime no longer holds, unless...
Intermediate inflation in light of the three-year WMAP observations (2006)
Barrow, John D, Liddle, Andrew R, Pahud, Cédric
The three-year observations from the Wilkinson Microwave Anisotropy Probe have been hailed as giving the first clear indication of a spectral index n_s0 is given (within the slow-roll approximation)...
On the evolution of universes in quadratic theories of gravity (2006)
Barrow, John D., Hervik, Sigbjorn
We use a dynamical systems approach to investigate Bianchi type I and II universes in quadratic theories of gravity. Due to the complicated nature of the equations of motion we focus on the stability...
Averaging anisotropic cosmologies (2006)
Barrow, John D., Tsagas, Christos G.
We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we...
The Dominant Balance at Cosmological Singularities (2006)
Cotsakis, Spiros, Barrow, John D.
We define the notion of a finite-time singularity of a vector field and then discuss a technique suitable for the asymptotic analysis of vector fields and their integral curves in the neighborhood of...
Observable Effects of Scalar Fields and Varying Constants (2006)
Barrow, John D., Shaw, Douglas J.
We show by using the method of matched asymptotic expansions that a sufficient condition can be derived which determines when a local experiment will detect the cosmological variation of a scalar...
Cosmology in three dimensions: steps towards the general solution (2006)
Barrow, John D., Shaw, Douglas J., Tsagas, Christos G.
We use covariant and first-order formalism techniques to study the properties of general relativistic cosmology in three dimensions. The covariant approach provides an irreducible decomposition of...
Cosmologies with Energy Exchange (2006)
We provide a simple mathematical description of the exchange of energy between two fluids in an expanding Friedmann universe with zero spatial curvature. The evolution can be reduced to a single...
We consider the possibility of energy being exchanged between the scalar and matter fields in scalar-tensor theories of gravity. Such an exchange provides a new mechanism which can drive variations...
Further Exact Cosmological Solutions to Higher-Order Gravity Theories (2006)
We investigate the effect of deviations from general relativity on approach to the initial singularity by finding exact cosmological solutions to a wide class of fourth-order gravity theories. We...
Shaw, Douglas J., Barrow, John D.
We investigate the conditions under which cosmological variations in physical `constants' and scalar fields are detectable on the surface of local gravitationally-bound systems, such as planets, in...
ON THE EVOLUTION OF UNIVERSES IN QUADRATIC THEORIES OF GRAVITY (2006)
Barrow, John D., Hervik, Sigbjorn
We use a dynamical systems approach to investigate Bianchi type I and II universes in quadratic theories of gravity. Due to the complicated nature of the equations of motion we focus on the stability...
Local Experiments See Cosmologically Varying Constants (2005)
Shaw, Douglas J., Barrow, John D.
We describe a rigorous construction, using matched asymptotic expansions, which establishes under very general conditions that local terrestrial and solar-system experiments will measure the effects...
Shaw, Douglas J., Barrow, John D.
We apply the method of matched asymptotic expansions to analyse whether cosmological variations in physical `constants' and scalar fields are detectable, locally, on the surface of local...
Anisotropically Inflating Universes (2005)
Barrow, John D., Hervik, Sigbjorn
We show that in theories of gravity that add quadratic curvature invariants to the Einstein-Hilbert action there exist expanding vacuum cosmologies with positive cosmological constant which do not...
We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with...
The Existence of Godel, Einstein and de Sitter Universes (2005)
We determine the general conditions for the existence of Godel, Einstein static, and de Sitter universes in gravity theories derived from a Lagrangian that is an arbitrary function of the scalar...
Cosmological Co-evolution of Yang-Mills Fields and Perfect Fluids (2005)
Barrow, John D., Jin, Yoshida, Maeda, Kei-ichi
We study the co-evolution of Yang-Mills fields and perfect fluids in Bianchi type I universes. We investigate numerically the evolution of the universe and the Yang-Mills fields during the radiation...
Exact cosmological solutions of scale-invariant gravity theories (2005)
We have found new anisotropic vacuum solutions for the scale-invariant gravity theories which generalise Einstein's general relativity to a theory derived from the Lagrangian $R^{1+\delta}$. These...
The Power of General Relativity (2005)
Clifton, Timothy, Barrow, John D.
We study the cosmological and weak-field properties of theories of gravity derived by extending general relativity by means of a Lagrangian proportional to $R^{1+\delta}$. This scale-free extension...
Cosmological Bounds on Spatial Variations of Physical Constants (2005)
We derive strong observational limits on any possible large-scale spatial variation in the values of physical 'constants' whose space-time evolution is driven by a scalar field. The limits are...
Cosmological Constraints on a Dynamical Electron Mass (2005)
Barrow, John D, Magueijo, Joao
Motivated by recent astrophysical observations of quasar absorption systems, we formulate a simple theory where the electron to proton mass ratio $\mu =m_{e}/m_{p}$ is allowed to vary in space-time....
Varying Couplings in Electroweak Theory (2004)
Shaw, Douglas J., Barrow, John D.
We extend the theory of Kimberly and Magueijo for the spacetime variation of the electroweak couplings in the unified Glashow-Salam-Weinberg model of the electroweak interaction to include quantum...
Structure and stability of the Lukash plane-wave spacetime (2004)
Barrow, John D., Tsagas, Christos G.
We study the vacuum, plane-wave Bianchi $VII{}_{h}$ spacetimes described by the Lukash metric. Combining covariant with orthonormal frame techniques, we describe these models in terms of their...
New Isotropic and Anisotropic Sudden Singularities (2004)
Barrow, John D., Tsagas, Christos G.
We show the existence of an infinite family of finite-time singularities in isotropically expanding universes which obey the weak, strong, and dominant energy conditions. We show what new type of...
More General Sudden Singularities (2004)
We present a general form for the solution of an expanding general-relativistic Friedmann universe that encounters a singularity at finite future time. The singularity occurs in the material pressure...
Bouncing Universes with Varying Constants (2004)
Barrow, John D., Kimberly, Dagny, Magueijo, Joao
We investigate the behaviour of exact closed bouncing Friedmann universes in theories with varying constants. We show that the simplest BSBM varying-alpha theory leads to a bouncing universe. The...
Do Fermions and Bosons Produce the Same Gravitational Field? (2004)
Barrow, John D., Scherrer, Robert J.
We examine some cosmological consequences of gravity coupling with different strength to fermions and bosons. We show that this leads to a different perturbation of the standard picture of primordial...
Sudden Future Singularities (2004)
We show that a singularity can occur at a finite future time in an expanding Friedmann universe even when the density is positive and the density plus the sum of the principal pressures is positive....
Das 1x1 des Universums - Neue Erkenntnisse über die Naturkonstanten. (2004)
John D. Barrow erklärt die Gesetzmäßigkeiten, auf denen unser Wissen von der Beschaffenheit des Universums beruht: die Naturkonstanten. Newtons Gravitationskonstante, Einsteins...
Barrow, John D., Tsagas, Christos G.
We consider the brane-world generalisation of the Godel universe and analyse its dynamical interaction with the bulk. The exact homogeneity of the standard Godel spacetime no longer holds, unless the...
Dynamics and stability of the Godel universe (2003)
Barrow, John D., Tsagas, Christos G.
We use covariant techniques to describe the properties of the Godel universe and then consider its linear response to a variety of perturbations. Against matter aggregations, we find that the...
Mapping the Dark Energy with Varying Alpha (2003)
Parkinson, David, Bassett, Bruce A., Barrow, John D.
Cosmological dark energy is a natural source of variation of the fine structure constant. Using a model-independent approach we show that once general assumptions about the alpha-varying interactions...
Quasi-Spherical Gravitational Collapse in Any Dimension (2003)
Debnath, Ujjal, Chakraborty, Subenoy, Barrow, John D.
We study the occurrence and nature of naked singularities for a dust model with non-zero cosmological constant in ($n+2$)-dimensional Szekeres space-times (which possess no Killing vectors) for...
The Future of Tilted Bianchi Universes (2003)
Barrow, John D., Hervik, Sigbjorn
An asymptotic stability analysis of spatially homogeneous models of Bianchi type containing tilted perfect fluids is performed. Using the known attractors for the non-tilted Bianchi type universes,...
The Copernican Principle in Compact Spacetimes (2003)
Copernicus realised we were not at the centre of the universe. A universe made finite by topological identifications introduces a new Copernican consideration: while we may not be at the geometric...
A Test of a Test for Chaos (2003)
A simple new binary test for chaos has been proposed by Gottwald and Melbourne. We apply this test successfully to the Henon-Heiles and Lorenz systems, demonstrating its applicability to conservative...
Small-scale CMB polarization anisotropies due to tangled primordial magnetic fields (2003)
Subramanian, Kandaswamy, Seshadri, T. R., Barrow, John. D.
Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface (LSS) of the cosmic microwave background radiation (CMBR). Such perturbations...
On the Stability of the Einstein Static Universe (2003)
Barrow, John D, Ellis, George, Maartens, Roy, Tsagas, Christos
We show using covariant techniques that the Einstein static universe containing a perfect fluid is always neutrally stable against small inhomogeneous vector and tensor perturbations and neutrally...
Indefinite Information Processing in Ever-expanding Universes (2003)
Barrow, John D., Hervik, Sigbjorn
We show that generic anisotropic universes arbitrarily close to the open Friedmann universe allow information processing to continue into the infinite future if there is no cosmological constant or...
Gauge-Invariant Perturbations of Varying-Alpha Cosmologies (2002)
Using a gauge-invariant formalism we derive and solve the perturbed cosmological equations for the BSBM theory of varying fine structure 'constant'. We calculate the time evolution of inhomogeneous...
Unusual Features of Varying Speed of Light Cosmologies (2002)
We contrast features of simple varying speed of light (VSL) cosmologies with inflationary universe models. We present new features of VSL cosmologies and show that they face problems explaining the...
Constants and Variations: From Alpha to Omega (2002)
We review some of the history and properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist...
Qualitative Analysis of Universes with Varying Alpha (2002)
Barrow, John D., Mota, David F.
Assuming a Friedmann universe which evolves with a power-law scale factor, $a=t^{n}$, we analyse the phase space of the system of equations that describes a time-varying fine structure 'constant',...
The Weyl tensor in Spatially Homogeneous Cosmological Models (2002)
Barrow, John D., Hervik, Sigbjorn
We study the evolution of the Weyl curvature invariant in all spatially homogeneous universe models containing a non-tilted gamma-law perfect fluid. We investigate all the Bianchi and Thurston type...
Small-scale microwave background anisotropies due to tangled primordial magnetic fields (2002)
Subramanian, Kandaswamy, Barrow, John D.
An inhomogeneous cosmological magnetic field creates vortical perturbations that survive Silk damping on much smaller scales than compressional modes. This ensures that there is no sharp cut-off in...
Is it e or is it c? Experimental Tests of Varying Alpha (2002)
Magueijo, Joao, Barrow, John D., Sandvik, Haavard Bunes
Is the recent evidence for a time-varying fine structure 'constant' $\alpha$ to be interpreted as a varying $e$, $c$, $\hbar$, or a combination thereof? We consider the simplest varying electric...
Science and Ultimate Reality : Quantum Theory, Cosmology, and Complexity (2002)
Barrow, John D, Davies, Paul Charles William, Harper, Charles L
Barrow, John D., Hervik, Sigbjorn
We investigate brane-worlds with a pure magnetic field and a perfect fluid. We extend earlier work to brane-worlds, and find new properties of the Bianchi type I brane-world. We find new asymptotic...
Kaluza-Klein anisotropy in the CMB (2001)
We show that 5-dimensional Kaluza-Klein graviton stresses can slow the decay of shear anisotropy on the brane to observable levels, and we use cosmic microwave background anisotropies to place limits...
All Universes Great and Small (2001)
Barrow, John D., Kodama, Hideo
If the topology of the universe is compact we show how it significantly changes our assessment of the naturalness of the observed structure of the universe and the likelihood of its present state of...
Scaling Solutions and reconstruction of Scalar Field Potentials (2001)
Rubano, Claudio, Barrow, John D.
Starting from the hypothesis of scaling solutions, the general exact form of the scalar field potential is found. In the case of two fluids, it turns out to be a negative power of hyperbolic sine. In...
Cosmological Evolution of Black Holes in Brans-Dicke Gravity (2001)
Sakai, Nobuyuki, Barrow, John D.
We consider a modified ``Swiss cheese'' model in Brans-Dicke theory, and use it to discuss the evolution of black holes in an expanding universe. We define the black hole radius by the Misner-Sharp...
Bianchi VIII Empty Futures (2001)
Using a qualitative analysis based on the Hamiltonian formalism and the orthonormal frame representation we investigate whether the chaotic behaviour which occurs close to the initial singularity is...
The twin paradox in compact spaces (2001)
Twins travelling at constant relative velocity will each see the other's time dilate leading to the apparent paradox that each twin believes the other ages more slowly. In a finite space, the twins...
Murphy, M. T., Webb, J. K., Flambaum, Victor V., Dzuba, V. A., Churchill, Christopher W., Prochaska, Jason X., ...
An experimental search for variation in the fundamental coupling constants is strongly motivated by modern high-energy physics theories. Comparison of quasar (QSO) absorption-line spectra with...
Further evidence for cosmological evolution of the fine structure constant (2001)
Webb, J. K., Murphy, M. T., Flambaum, Victor V., Dzuba, V. A., Barrow, John D., Churchill, Christopher W., ...
We describe the results of a search for time variability of the fine structure constant α using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm...
Murphy, M. T., Webb, J. K., Flambaum, Victor V., Dzuba, V. A., Churchill, Christopher W., Prochaska, Jason X., ...
An experimental search for variation in the fundamental coupling constants is strongly motivated by modern high-energy physics theories. Comparison of quasar (QSO) absorption-line spectra with...
Further evidence for cosmological evolution of the fine structure constant (2001)
Webb, J. K., Murphy, M. T., Flambaum, Victor V., Dzuba, V. A., Barrow, John D., Churchill, Christopher W., ...
We describe the results of a search for time variability of the fine structure constant α using absorption systems in the spectra of distant quasars. Three large optical data sets and two 21 cm...
The Isotropy of Compact Universes (2000)
Barrow, John D., Kodama, Hideo
We discuss the problem of the stability of the isotropy of the universe in the space of ever-expanding spatially homogeneous universes with a compact spatial topology. The anisotropic modes which...
Evolution of Black Holes in Brans-Dicke Cosmology (2000)
Sakai, Nobuyuki, Barrow, John D.
We consider a modified ``Swiss cheese'' model in the Brans-Dicke theory, and discuss the evolution of black holes in the expanding universe. We define the black hole radius by the Misner-Sharp mass...
Fractals and Scars on a Compact Octagon (1999)
A finite universe naturally supports chaotic classical motion. An ordered fractal emerges from the chaotic dynamics which we characterize in full for a compact 2-dimensional octagon. In the classical...
Can a changing $\alpha$ explain the Supernovae results? (1999)
Barrow, John D., Magueijo, Joao
We show that the Supernovae results, implying evidence for an accelerating Universe, may be closely related to the recent discovery of redshift dependence in the fine structure constant $\alpha$. The...
Chaos and order in a finite universe (1999)
All inhabitants of this universe, from galaxies to people, are finite. Yet the universe itself is often assumed to be infinite. If instead the universe is topologically finite, then light and matter...
Spatial Variations of Fundamental Constants (1999)
Barrow, John D., O'Toole, Chris
We show that observational limits on the possible time variation of constants of Nature are significantly affected by allowing for both space and time variation. Bekenstein's generalisation of...
We discuss the evolution of radiation and Bekenstein-Hawking entropies in expanding isotropic universes. We establish a general relation which shows why it is inevitable that there is currently a...
Barrow, John D., Magueijo, Joao
We define the flatness and quasi-flatness problems in cosmological models. We seek solutions to both problems in homogeneous and isotropic Brans-Dicke cosmologies with varying speed of light. We...
Imposibilidad : los límites de la ciencia y la ciencia de los límites (1999)
Traducción de: Impossibility. The Limits of Science and the Science of Limits
Traducción de: Impossibility. The Limits of Science and the Science of Limits
Cosmology and the Origin of Life (1998)
We discuss some of the cosmological constraints on the evolution and persistence of life in the Universe and in hypothetical universes other than our own. We highlight the role played by the age and...
Varying-$\alpha $ Theories and Solutions to the Cosmological Problems (1998)
Barrow, John D., Magueijo, Joao
If the fine structure constant $\alpha =e^2/(\hbar c)$ were to change, then a number of interpretations would be possible, attributing this change either to variations in the electron charge, the...
Solutions to the Quasi-flatness and Quasi-lambda Problems (1998)
Barrow, John D., Magueijo, Joao
Big Bang models of the Universe predict rapid domination by curvature, a paradox known as the flatness problem. Solutions to this problem usually leave the Universe exactly flat for every practical...
Cosmologies with Varying Light-Speed (1998)
We analyse a generalisation of general relativity that incorporates a cosmic time-variation of the velocity of light in vacuum, $c,$ and the Newtonian gravitation 'constant', $G,$ proposed by...
How the Universe got its Spots (1998)
Levin, Janna, Scannapieco, Evan, De Gasperis, Giancarlo, Silk, Joseph, Barrow, John D.
The universe displays a three-dimensional pattern of hot and cold spots in the radiation remnant from the big bang. The global geometry of the universe can be revealed in the spatial distribution of...
Barrow, John D., Kunze, Kerstin E.
An overview is given of the formulation of low-energy string cosmologies together with examples of particular solutions, successes and problems of the theory.
String Cosmology and Chaos (1998)
Barrow, John D., Dabrowski, Mariusz P.
We investigate Bianchi type IX ''Mixmaster'' universes within the framework of the low-energy tree-level effective action for string theory, which (when the ''stringy'' 2-form axion potential...
Microwave Background Signals from Tangled Magnetic Fields (1998)
Subramanian, Kandaswamy, Barrow, John D.
An inhomogeneous cosmological magnetic field will create Alfven-wave modes that induce a small rotational velocity perturbation on the last scattering surface of the microwave background radiation....
A Search for Time Variation of the Fine Structure Constant (1998)
Webb, John K., Flambaum, Victor V., Churchill, Christopher W., Drinkwater, Michael J., Barrow, John D.
A method offering an order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant, alpha. Applying the...
Godel Universes in String Theory (1998)
Barrow, John D., Dabrowski, Mariusz P.
We show that homogeneous G\"odel spacetimes need not contain closed timelike curves in low-energy-effective string theories. We find exact solutions for the G\"odel metric in string theory for the...
Gauge-invariant magnetic perturbations in perfect-fluid cosmologies (1998)
Tsagas, Christos G., Barrow, John D.
We develop further our extension of the Ellis-Bruni covariant and gauge-invariant formalism to the general relativistic treatment of density perturbations in the presence of cosmological magnetic...
The radiation-matter transition in Jordan-Brans-Dicke theory (1998)
Liddle, Andrew R, Mazumdar, Anupam, Barrow, John D
We study the transition from radiation domination to matter domination in Jordan-Brans-Dicke theory, in particular examining how the Hubble length at equality depends on the coupling parameter...
Magnetohydrodynamics in the Early Universe and the Damping of Non-linear Alfven Waves (1997)
Subramanian, Kandaswamy, Barrow, John D.
The evolution and viscous damping of cosmic magnetic fields in the early universe, is analysed. Using the fact that the fluid, electromagnetic, and shear viscous energy-momentum tensors are all...
Limits on Cosmological Magnetic Fields and Other Anisotropic Stresses (1997)
We discuss the cosmological evolution of matter sources with small anisotropic pressures. This includes electric and magnetic fields, collisionless relativistic particles, gravitons, antisymmetric...
Varying G and Other Constants (1997)
We review recent progress in the study of varying constants and attempts to explain the observed values of the fundamental physical constants. We describe the variation of $G$ in Newtonian and...
Is there chaos in string cosmology? (1997)
Barrow, John D., Dabrowski, Mariusz P.
Bianchi type IX, 'Mixmaster' universes are investigated in low-energy-effective-action string cosmology. We show that, unlike in general relativity, there is no chaos in these string cosmologies for...
Spherical Curvature Inhomogeneities in String Cosmology (1997)
Barrow, John D., Kunze, Kerstin E.
We study the evolution of non-linear spherically symmetric inhomogeneities in string cosmology. Friedmann solutions of different spatial curvature are matched to produce solutions which describe the...
Chaos in the Einstein-Yang-Mills Equations (1997)
Yang-Mills color fields evolve chaotically in an anisotropically expanding universe. The chaotic behaviour differs from that found in anisotropic Mixmaster universes. The universe isotropizes at late...
Can Inflation be Falsified? (1997)
Barrow, John D, Liddle, Andrew R
Despite its central role in modern cosmology, doubts are often expressed as to whether cosmological inflation is really a falsifiable theory. We distinguish two facets of inflation, one as a theory...
A Gauge-invariant Analysis of Magnetic Fields in General Relativistic Cosmology (1997)
Tsagas, Christos G., Barrow, John D.
We provide a fully general-relativistic treatment of cosmological perturbations in a universe permeated by a large-scale primordial magnetic field, using the Ellis-Bruni gauge-invariant formalism....
Geodesics in Open Universes (1997)
We present the geodesics on homogeneous and isotropic negatively curved spaces in a simple form suitable for application to cosmological problems. We discuss how the patterns in the microwave sky of...
Flat Spots: topological signatures of an open universe in COBE sky maps (1997)
Levin, Janna J., Barrow, John D., Bunn, Emory F., Silk, Joseph
We investigate the behaviour of light rays in an open universe with a partly periodic horn topology. The geodesics can be solved exactly and the periodic topology creates characteristic new effects...
Inhomogeneous String Cosmologies (1997)
Barrow, John D., Kunze, Kerstin E.
We present exact inhomogeneous and anisotropic cosmological solutions of low-energy string theory containing dilaton and axion fields. The spacetime metric possesses cylindrical symmetry. The...
Cosmological Limits on Slightly Skew Stresses (1997)
We present an analysis of the cosmological evolution of matter sources with small anisotropic pressures. This includes electric and magnetic fields, collisionless relativistic particles, gravitons,...
Constraints on a Primordial Magnetic Field (1997)
Barrow, John D., Ferreira, Pedro G., Silk, Joseph
We derive an upper limit of $B_0
Spherical Curvature Inhomogeneities in String Cosmology (1997)
John D. Barrow, Kerstin E. Kunze, Astronomy Centre
We study the evolution of non-linear spherically symmetric inhomogeneities in string cosmology. Friedmann solutions of different spatial curvature are matched to produce solutions which describe the...
Kantowski-Sachs String Cosmologies (1997)
John D. Barrow, Mariusz P. D��abrowski
We present new exact solutions of the low-energy-effective-action string equations with both dilaton OE and axion H fields non-zero. The background universe is of Kantowski-Sachs type. We consider...
A Gauge-invariant Analysis of Magnetic Fields in General Relativistic Cosmology (1997)
Christos Tsagas, John D. Barrow
We provide a fully general-relativistic treatment of cosmological perturbations in a universe permeated by a large-scale primordial magnetic field using the Ellis-Bruni gauge-invariant formalism. The...
Exact Inhomogeneous Cosmological Models (1996)
Barrow, John D., Kunze, Kerstin E.
We present new exact inhomogeneous vacuum cosmological solutions of Einstein's equations. They provide new information about the nature of general cosmological solutions to Einstein's equations.
Kantowski-Sachs String Cosmologies (1996)
Barrow, John D., Dabrowski, Mariusz P.
We present new exact solutions of the low-energy-effective-action string equations with both dilaton $\phi $ and axion $H$ fields non-zero. The background universe is of Kantowski-Sachs type. We...
Spatially Homogeneous String Cosmologies (1996)
Barrow, John D., Kunze, Kerstin E.
We determine the most general form of the antisymmetric $H$-field tensor derived from a purely time-dependent potential that is admitted by all possible spatially homogeneous cosmological models in...
The Behaviour Of Cosmological Models With Varying-G (1996)
Barrow, John D., Parsons, Paul
We provide a detailed analysis of Friedmann-Robertson-Walker universes in a wide range of scalar-tensor theories of gravity. We apply solution-generating methods to three parametrised classes of...
The Behaviour Of Cosmological Models With Varying-G (1996)
We provide a detailed analysis of Friedmann-Robertson-Walker universes in a wide range of scalar-tensor theories of gravity. We apply solution-generating methods to three parametrised classes of...
Inflationary Models with Logarithmic Potentials (1995)
Barrow, John D., Parsons, Paul
We examine inflationary universe models driven by scalar fields with logarithmic potentials of the form $V(\phi) = V_0 \phi^p(\ln \phi)^q$. Combining the slow-roll approximation with asymptotic...
Generalised Scalar Field Potentials and Inflation (1995)
Parsons, Paul, Barrow, John D.
We investigate the range of inflationary universe models driven by scalar fields possessing a general interaction potential of the form $V(\phi) = V_0 \phi^n \exp(-\lambda \phi^m)$. Power-law, de...
Inflationary Models with Logarithmic Potentials (1995)
We examine inflationary universe models driven by scalar fields with logarithmic potentials of the form V (OE) = V 0 OE p (ln OE) q . Combining the slow-roll approximation with asymptotic techniques,...
Formalising the Slow-Roll Approximation in Inflation (1994)
Liddle, Andrew R., Parsons, Paul, Barrow, John D.
The meaning of the inflationary slow-roll approximation is formalised. Comparisons are made between an approach based on the Hamilton-Jacobi equations, governing the evolution of the Hubble...
Teorías del todo : hacia una explicación fundamental del universo (1994)
Traducción de: Theories of everything
Traducción de: Theories of everything
Formalising the Slow-Roll Approximation in Inflation (1994)
Andrew R. Liddle, Paul Parsons, John D. Barrow, Brighton Bn Qh
The meaning of the inflationary slow-roll approximation is formalised. Comparisons are made between an approach based on the Hamilton-Jacobi equations, governing the evolution of the Hubble...
Perturbation Spectra from Intermediate Inflation (1993)
Barrow, John D, Liddle, Andrew R
We investigate models of `intermediate' inflation, where the scale factor $a(t)$ grows as $a(t) = \exp (A t^f)$, $0 < f < 1$, $A$ constant. These solutions arise as exact analytic solutions for a...
L'universo come opera d'arte, John D. Barrow, trad. di Isabella Blum e Carlo Capararo. . - Milano. NALUAF000464, Rizzoli. NAEDAF004331, 23 cm.