The Return of the Phoenix Universe (2009)
Lehners, Jean-Luc, Steinhardt, Paul J., Turok, Neil
Georges Lemaitre introduced the term "phoenix universe" to describe an oscillatory cosmology with alternating periods of gravitational collapse and expansion. This model is ruled out observationally...
A multitrace deformation of ABJM theory (2009)
Craps, Ben, Hertog, Thomas, Turok, Neil
Motivated by the study of big crunch singularities in asymptotically $AdS_4$ spacetimes, we consider a marginal triple trace deformation of ABJM theory. The deformation corresponds to adding a...
Measures on Mixing Angles (2008)
Gibbons, Gary W., Gielen, Steffen, Pope, C. N., Turok, Neil
We address the problem of the apparently very small magnitude of CP violation in the standard model, measured by the Jarlskog invariant J. In order to make statements about probabilities for certain...
Naturalness of CP Violation in the Standard Model (2008)
Gibbons, Gary W., Gielen, Steffen, Pope, C. N., Turok, Neil
We construct a natural measure on the space of CKM matrices in the standard model, assuming the fermion mass matrices are randomly selected from a distribution which fits the observed quark mass...
Interview of Neil Turok (2008)
Interviewed by Tina Kosir on 19th February 2008 and filmed by Alan Macfarlane and edited by Sarah Harrison, lasts two hours
Quantum Resolution of Cosmological Singularities using AdS/CFT (2007)
Craps, Ben, Hertog, Thomas, Turok, Neil
The AdS/CFT correspondence allows us to map a dynamical cosmology to a dual quantum field theory living on the boundary of spacetime. Specifically, we study a five-dimensional model cosmology in type...
Horizons and Tunneling in the Euclidean False Vacuum (2007)
In the thin-wall approximation, the decay of a gravitating false vacuum to a lower-energy state is affected by the cosmological horizon structure in both spaces. The nucleation radius of a bubble of...
Exponentially Small, Ph. Brax, Neil Turok
: We propose a stringy mechanism whereby a large hierarchy between symmetry breaking scales is generated. This mechanism is based upon the existence of a fifth dimension compactified on a segment. We...
Halo Formation in Warm Dark Matter Models (2007)
Paul Bode, Jeremiah P. Ostriker, Neil Turok
Discrepancies have emerged between the predictions of standard cold dark matter (CDM) theory and observations of clustering on sub-galactic scales. Warm dark matter (WDM) is a simple modification of...
From Big Crunch to Big Bang with AdS/CFT (2007)
Turok, Neil, Craps, Ben, Hertog, Thomas
The AdS/CFT correspondence is used to describe five-dimensional cosmology with a big crunch singularity in terms of super-Yang-Mills theory on R times S^3 deformed by a potential which is unbounded...
Bouncing Negative-Tension Branes (2007)
Lehners, Jean-Luc, Turok, Neil
Braneworlds, understood here as double domain wall spacetimes, can be described in terms of a linear harmonic function, with kinks at the locations of the boundary branes. In a dynamical setting,...
Stringy corrections to a time-dependent background solution of string and M-Theory (2007)
We consider one of the simplest time-dependent backgrounds in M-theory, describing the shrinking away of the M-theory dimension with the other spatial dimensions static. As the M-theory dimension...
Primordial Black Hole Baryogenesis (2007)
Baumann, Daniel, Steinhardt, Paul J., Turok, Neil
We reconsider the possibility that the observed baryon asymmetry was generated by the evaporation of primordial black holes that dominated the early universe. We present a simple derivation showing...
Generating Ekpyrotic Curvature Perturbations Before the Big Bang (2007)
Lehners, Jean-Luc, McFadden, Paul, Turok, Neil, Steinhardt, Paul J.
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, that can be entirely described...
Effective Actions for Heterotic M-Theory (2006)
Lehners, Jean-Luc, McFadden, Paul, Turok, Neil
We discuss the moduli space approximation for heterotic M-theory, both for the minimal case of two boundary branes only, and when a bulk brane is included. The resulting effective actions may be used...
Colliding Branes in Heterotic M-theory (2006)
Lehners, Jean-Luc, McFadden, Paul, Turok, Neil
We study the collision of two flat, parallel end-of-the-world branes in heterotic M-theory. By insisting that there is no divergence in the Riemann curvature as the collision approaches, we are able...
The Measure Problem in Cosmology (2006)
The Hamiltonian structure of general relativity provides a natural canonical measure on the space of all classical universes, i.e., the multiverse. We review this construction and show how one can...
Cosmic Perturbations Through the Cyclic Ages (2006)
Erickson, Joel K., Gratton, Steven, Steinhardt, Paul J., Turok, Neil
We analyze the evolution of cosmological perturbations in the cyclic model, paying particular attention to their behavior and interplay over multiple cycles. Our key results are: (1) galaxies and...
Why the cosmological constant is small and positive (2006)
Steinhardt, Paul J., Turok, Neil
Within conventional big bang cosmology, it has proven to be very difficult to understand why today's cosmological constant is so small. In this paper, we show that a cyclic model of the universe can...
Classical Propagation of Strings across a Big Crunch/Big Bang Singularity (2006)
One of the simplest time-dependent solutions of M theory consists of nine-dimensional Euclidean space times 1+1-dimensional compactified Milne space-time. With a further modding out by Z_2, the...
Solution of a Braneworld Big Crunch/Big Bang Cosmology (2005)
McFadden, Paul, Turok, Neil, Steinhardt, Paul J.
We solve for the cosmological perturbations in a five-dimensional background consisting of two separating or colliding boundary branes, as an expansion in the collision speed V divided by the speed...
Inflationary predictions for scalar and tensor fluctuations reconsidered (2005)
Boyle, Latham A., Steinhardt, Paul J., Turok, Neil
We reconsider the predictions of inflation for the spectral index of scalar (energy density) fluctuations (n_s) and the tensor/scalar ratio (r) using a discrete, model-independent measure of the...
Langevin Analysis of Eternal Inflation (2005)
It has been widely claimed that inflation is generically eternal to the future, even in models where the inflaton potential monotonically increases away from its minimum. The idea is that quantum...
Controlling Chaos through Compactification in Cosmological Models with a Collapsing Phase (2005)
Wesley, Daniel H., Steinhardt, Paul J., Turok, Neil
We consider the effect of compactification of extra dimensions on the onset of classical chaotic "Mixmaster" behavior during cosmic contraction. Assuming a universe that is well-approximated as a...
Effective theory approach to brane world black holes (2004)
McFadden, Paul L., Turok, Neil
We derive static spherically-symmetric vacuum solutions of the low-energy effective action for the two brane Randall-Sundrum model. The solutions with non-trivial radion belong to a one-parameter...
Conformal symmetry of brane world effective actions (2004)
McFadden, Paul L., Turok, Neil
A simple derivation of the low-energy effective action for brane worlds is given, highlighting the role of conformal invariance. We show how to improve the effective action for a positive- and...
M Theory Model of a Big Crunch/Big Bang Transition (2004)
Turok, Neil, Perry, Malcolm, Steinhardt, Paul J.
We consider a picture in which the transition from a big crunch to a big bang corresponds to the collision of two empty orbifold planes approaching each other at a constant non-relativistic speed in...
The Cyclic Model Simplified (2004)
Steinhardt, Paul J., Turok, Neil
The Cyclic Model attempts to resolve the homogeneity, isotropy, and flatness problems and generate a nearly scale-invariant spectrum of fluctuations during a period of slow contraction that precedes...
Boyle, Latham A., Steinhardt, Paul J., Turok, Neil
For a 4-dimensional spatially-flat Friedmann-Robertson-Walker universe with a scalar field $\phi(x)$, potential $V(\phi)$ and constant equation of state $w=p/\rho$, we show that an expanding solution...
Beyond Inflation: A Cyclic Universe Scenario (2004)
Turok, Neil, Seinhardt, Paul J.
Inflation has been the leading early universe scenario for two decades, and has become an accepted element of the successful `cosmic concordance' model. However, there are many puzzling features of...
Kasner and Mixmaster behavior in universes with equation of state w \ge 1 (2003)
Erickson, Joel K., Wesley, Daniel H., Steinhardt, Paul J., Turok, Neil
We consider cosmological models with a scalar field with equation of state $w\ge 1$ that contract towards a big crunch singularity, as in recent cyclic and ekpyrotic scenarios. We show that chaotic...
The cosmic gravitational wave background in a cyclic universe (2003)
Boyle, Latham A., Steinhardt, Paul J., Turok, Neil
Inflation predicts a primordial gravitational wave spectrum that is slightly ``red,'' i.e., nearly scale-invariant with slowly increasing power at longer wavelengths. In this paper, we compute both...
Designing Cyclic Universe Models (2003)
Khoury, Justin, Steinhardt, Paul J., Turok, Neil
Recent advances in understanding the propagation of perturbations through the transition from big crunch to big bang (esp. Tolley et al. hep-th/0306109) make it possible for the first time to...
Cosmological Perturbations in a Big Crunch/Big Bang Space-time (2003)
Tolley, Andrew J., Turok, Neil, Steinhardt, Paul J.
A prescription is developed for matching general relativistic perturbations across singularities of the type encountered in the ekpyrotic and cyclic scenarios i.e. a collision between orbifold...
Inflation versus Cyclic Predictions for Spectral Tilt (2003)
Khoury, Justin, Steinhardt, Paul J., Turok, Neil
We present a simple, nearly model-independent estimate that yields the predictions of the simplest inflationary and ekpyrotic/cyclic models for the spectral tilt of the primordial density...
Conditions for Generating Scale-Invariant Density Perturbations (2003)
Gratton, Steven, Khoury, Justin, Steinhardt, Paul J., Turok, Neil
We analyze the general conditions on the equation of state $w$ required for quantum fluctuations of a scalar field to produce a scale-invariant spectrum of density perturbations, including models...
Cosmological Perturbations Through a General Relativistic Bounce (2002)
Gordon, Christopher, Turok, Neil
The ekpyrotic and cyclic universe scenarios have revived the idea that the density perturbations apparent in today's universe could have been generated in a `pre-singularity' epoch before the big...
The Cyclic Universe: An Informal Introduction (2002)
Steinhardt, Paul J., Turok, Neil
The Cyclic Model is a radical, new cosmological scenario which proposes that the Universe undergoes an endless sequence of epochs which begin with a `big bang' and end in a `big crunch.' When the...
Quantum Fields in a Big Crunch/Big Bang Spacetime (2002)
Tolley, Andrew J., Turok, Neil
We consider quantum field theory on a spacetime representing the Big Crunch/Big Bang transition postulated in the ekpyrotic or cyclic cosmologies. We show via several independent methods that an...
Is Vacuum Decay Significant in Ekpyrotic and Cyclic Models? (2001)
Steinhardt, Paul J., Turok, Neil
It has recently been argued that bubble nucleation in ekpyrotic and cyclic cosmological scenarios can lead to unacceptable inhomogeneities unless certain constraints are satisfied. In this paper we...
Cosmic Evolution in a Cyclic Universe (2001)
Steinhardt, Paul J., Turok, Neil
Based on concepts drawn from the ekpyrotic scenario and M-theory, we elaborate our recent proposal of a cyclic model of the Universe. In this model, the Universe undergoes an endless sequence of...
A Cyclic Model of the Universe (2001)
Steinhardt, Paul J., Turok, Neil
We propose a cosmological model in which the universe undergoes an endless sequence of cosmic epochs each beginning with a `bang' and ending in a `crunch.' The temperature and density are finite at...
Closed Universes from Cosmological Instantons (2001)
Gratton, Steven, Lewis, Antony, Turok, Neil
Current observational data is consistent with the universe being slightly closed. We investigate families of singular and non-singular closed instantons that could describe the beginning of a closed...
Density Perturbations in the Ekpyrotic Scenario (2001)
Khoury, Justin, Ovrut, Burt A., Steinhardt, Paul J., Turok, Neil
We study the generation of density perturbations in the ekpyrotic scenario for the early universe, including gravitational backreaction. We expose interesting subtleties that apply to both...
From Big Crunch to Big Bang (2001)
Khoury, Justin, Ovrut, Burt A., Seiberg, Nathan, Steinhardt, Paul J., Turok, Neil
We consider conditions under which a universe contracting towards a big crunch can make a transition to an expanding big bang universe. A promising example is 11-dimensional M-theory in which the...
Quantization of the massless minimally coupled scalar field and the dS/CFT correspondence (2001)
Tolley, Andrew J., Turok, Neil
We consider the quantization of the massless minimally coupled scalar field in de Sitter spacetime. The no-boundary Euclidean prescription naturally picks out the de Sitter invariant vacuum state of...
Detecting magnetic CMB polarization on an incomplete sky (2001)
Lewis, Antony, Challinor, Anthony, Turok, Neil
The full sky cosmic microwave background polarization field can be decomposed into `electric' and `magnetic' components. Working in harmonic space we construct magnetic variables that can be measured...
The shapes of dark matter dominated dwarf spheroidal stellar density profiles (2001)
A Bayesian likelihood analysis of the stellar density profile shapes of several dark matter dominated Galactic dwarf spheroidal galaxies (dSphs) has been completed. This analysis indicates that the...
Analysis of CMB polarization on an incomplete sky (2001)
Lewis, Antony, Challinor, Anthony, Turok, Neil
The full sky cosmic microwave background polarization field can be decomposed into 'electric' and 'magnetic' components. Working in harmonic space we construct window functions that allow clean...
A Brief Comment on "The Pyrotechnic Universe" (2001)
Khoury, Justin, Ovrut, Burt A., Steinhardt, Paul J., Turok, Neil
We respond to the criticisms by Kallosh, Kofman and Linde concerning our proposal of the ekpyrotic universe scenario. We point out a number of errors in their considerations and argue that, at this...
Visible Branes with Negative Tension in Heterotic M-Theory (2001)
Donagi, Ron Y., Khoury, Justin, Ovrut, Burt A., Steinhardt, Paul J., Turok, Neil
It is shown that there exist large classes of BPS vacua in heterotic M-theory which have negative tension on the visible orbifold plane, positive tension on the hidden plane and positive tension,...
The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang (2001)
Khoury, Justin, Ovrut, Burt A., Steinhardt, Paul J., Turok, Neil
We propose a cosmological scenario in which the hot big bang universe is produced by the collision of a brane in the bulk space with a bounding orbifold plane, beginning from an otherwise cold,...
Observations of the cosmic microwave sky are revealing the primordial non-uniformities from which all structure in the Universe grew. The only known physical mechanism for generating the...
Primordial Isocurvature Perturbations: Testing the Adiabaticity of the CMB Anisotropy (2000)
Bucher, Martin, Moodley, Kavilan, Turok, Neil
Prospects for testing the adiabaticity of the primordial cosmological perturbations using MAP and PLANCK are evaluated. The most general cosmological perturbation in a universe with just baryons,...
Halo Formation in Warm Dark Matter Models (2000)
Bode, Paul, Ostriker, Jeremiah P., Turok, Neil
Discrepancies have emerged between the predictions of standard cold dark matter (CDM) theory and observations of clustering on sub-galactic scales. Warm dark matter (WDM) is a simple modification of...
Homogeneous Modes of Cosmological Instantons (2000)
We discuss the O(4) invariant perturbation modes of cosmological instantons. These modes are spatially homogeneous in Lorentzian spacetime and thus not relevant to density perturbations. But their...
Characterising the Primordial Cosmic Perturbations (2000)
Bucher, Martin, Moodley, Kavilan, Turok, Neil
The most general homogeneous and isotropic statistical ensemble of linear scalar perturbations which are regular at early times, in a universe with only photons, baryons, neutrinos, and a cold dark...
Singular Instantons Made Regular (2000)
Kirklin, Kelly, Turok, Neil, Wiseman, Toby
The singularity present in cosmological instantons of the Hawking-Turok type is resolved by a conformal transformation, where the conformal factor has a linear zero of codimension one. We show that...
Gravitational Waves in Open de Sitter Space (2000)
Hawking, S. W., Hertog, Thomas, Turok, Neil
We compute the spectrum of primordial gravitational wave perturbations in open de Sitter spacetime. The background spacetime is taken to be the continuation of an O(5) symmetric instanton saddle...
An Observational Test of Quantum Cosmology (1999)
Gratton, Steven, Hertog, Thomas, Turok, Neil
We compute the tensor CMB anisotropy power spectrum for singular and non-singular instantons describing the beginning of an open universe according to the Euclidean no boundary proposal. Singular...
Gravity Waves from Instantons (1999)
We perform a first principles computation of the spectrum of gravity waves produced in open inflationary universes. The background spacetime is taken to be the continuation of an instanton saddle...
Cosmological Perturbations from the No Boundary Euclidean Path Integral (1999)
We compute, from first principles, the quantum fluctuations about instanton saddle points of the Euclidean path integral for Einstein gravity coupled to a scalar field. The Euclidean two-point...
Stability of Flat Space to Singular Instantons (1999)
Hawking and the author have proposed a class of singular, finite action instantons for defining the initial conditions for inflation. Vilenkin has argued they are unacceptable. He exhibited an...
Conservation Laws and Cosmological Perturbations in Curved Universes (1998)
Uzan, Jean-Philippe, Deruelle, Nathalie, Turok, Neil
When working in synchronous gauges, pseudo-tensor conservation laws are often used to set the initial conditions for cosmological scalar perturbations, when those are generated by topological defects...
Open Inflation, the Four Form and the Cosmological Constant (1998)
Fundamental theories of quantum gravity such as supergravity include a four form field strength which contributes to the cosmological constant. The inclusion of such a field into our theory of open...
Comment on `Quantum Creation of an Open Universe', by Andrei Linde (1998)
We comment on Linde's claim that one should change the sign in the action for a Euclidean instanton in quantum cosmology, resulting in the formula $P \sim e^{+S}$ for the probability of various...
Open Inflation Without False Vacua (1998)
We show that within the framework of a definite proposal for the initial conditions for the universe, the Hartle-Hawking `no boundary' proposal, open inflation is generic and does not require any...
Gamma Ray Bursts from Baryon Decay in Neutron Stars (1997)
Pen, Ue-Li, Loeb, Abraham, Turok, Neil
The standard unbroken electroweak theory is known to erase baryon number. The baryon number symmetry can be restored in the core of a neutron star as its density diverges via gravitational...
A Technique for Calculating Quantum Corrections to Solitons (1997)
We present a numerical scheme for calculating the first quantum corrections to the properties of static solitons. The technique is applicable to solitons of arbitrary shape, and may be used in 3+1...
The Scalar, Vector and Tensor Contributions to CMB anisotropies from Cosmic Defects (1997)
Turok, Neil, Pen, Ue-Li, Seljak, Uros
Recent work has emphasised the importance of vector and tensor contributions to the large scale microwave anisotropy fluctuations produced by cosmic defects. In this paper we provide a general...
Exponentially Small Couplings and the Hierarchy Problem (1997)
We propose a stringy mechanism whereby a large hierarchy between symmetry breaking scales is generated. This mechanism is based upon the existence of a fifth dimension compactified on a segment. We...
Exponentially Small Couplings between Twisted Fields of Orbifold String Theories (1997)
We investigate the natural occurence of exponentially small couplings in effective field theories deduced from higher dimensional models. We calculate the coupling between twisted fields of the Z_3...
Polarization of the Microwave Background in Defect Models (1997)
Seljak, Uros, Pen, Ue-Li, Turok, Neil
We compute the polarization power spectra for global strings, monopoles, textures and nontopological textures, and compare them to inflationary models. We find that topological defect models predict...
Power Spectra in Global Defect Theories of Cosmic Structure Formation (1997)
Pen, Ue-Li, Seljak, Uros, Turok, Neil
An efficient technique for computing perturbation power spectra in field ordering theories of cosmic structure formation is introduced, enabling computations to be carried out with unprecedented...
Normal Modes of the B=4 Skyrme Soliton (1997)
Barnes, Chris, Baskerville, Kim, Turok, Neil
The Skyrme model of nuclear physics requires quantisation if it is to match observed nuclear properties. A simple technique is used to find the normal mode spectrum of the baryon number B=4 Skyrme...
Cosmic Texture from a Broken Global SU(3) Symmetry (1997)
We investigate the observable consequences of creating cosmic texture by breaking a global SU(3) symmetry, rather than the SU(2) case which is generally studied. To this end, we study the nonlinear...
We present a calculation of the power spectrum generated in a classically symmetry-breaking O(N) scalar field through inflationary quantum fluctuations, using the large-N limit. The effective...
A Causal Source which Mimics Inflation (1996)
How unique are the inflationary predictions for the cosmic microwave anisotropy pattern? In this paper, it is asked whether an arbitrary causal source for perturbations in the standard hot big bang...
Sub-degree Scale Microwave Anisotropies from Cosmic Defects (1996)
If current ideas about unified field theories are correct, macroscopic cosmic defects may well exist. The observation of such an entity would have enormous significance for our understanding of...
Causality and the Doppler Peaks (1996)
Could cosmic structure have formed by the action of causal physics within the standard hot big bang, or was a prior period of inflation required? Recently there has been some discussion of whether...
Almost-Goldstone Bosons from Extra-Dimensional Gauge Theories (1995)
A mechanism is presented through which very light scalar degrees of freedom obeying the nonlinear sigma model equation can emerge in spontaneously broken gauge theories. The mechanism operates in...
Looking for $\Lambda$ with the Rees-Sciama Effect (1995)
Crittenden, Robert G., Turok, Neil
In models with a cosmological constant, a significant component of the large scale cosmic microwave background (CMB) anisotropy is produced at rather low redshifts, z < 1. In these models, the...
Open Inflation with Arbitrary False Vacuum Mass (1995)
We calculate the power spectrum of adiabatic density perturbations in an open inflationary model in which inflation occurs in two stages. First an epoch of old inflation creates a large, smooth...
Non-local Electroweak Baryogenesis Part I : Thin Wall Regime (1994)
Joyce, Michael, Prokopec, Tomislav, Turok, Neil
We investigate `non-local' schemes for baryogenesis at a first order electroweak phase transition, in which the effects of a $CP$ violating condensate on the bubble wall propagate into the unbroken...
Non-local Electroweak Baryogenesis Part II : The Classical Regime (1994)
Joyce, Michael, Prokopec, Tomislav, Turok, Neil
We investigate baryogenesis at a first order electroweak phase transition in the presence of a CP violating condensate on the bubble walls, in the regime in which the bubble walls are `thick', in the...
Electroweak Baryogenesis from a Classical Force (1994)
Joyce, Michael, Prokopec, Tomislav, Turok, Neil
We describe a new effect which produces baryons at a first order electroweak phase transition. It operates when there is a CP-violating field present on propagating bubble walls. The novel aspect is...
Polarization and Anisotropy of the Microwave Sky (1994)
Coulson, David, Crittenden, Robert G., Turok, Neil
We study the polarization-polarization and polarization-temperature correlations in standard adiabatic scenarios for structure formation. Temperature anisotropies due to gravitational potential wells...
Z Condensation and Standard Model Baryogenesis (1994)
The standard model satisfies Sakharov's conditions for baryogenesis but the CP violation in the KM matrix appears too small to account for the observed asymmetry. In this letter we explore a...
Efficient Electroweak Baryogenesis from Lepton Transport (1994)
Joyce, Michael, Prokopec, Tomislav, Turok, Neil
One mechanism for generating a baryon asymmetry at the electroweak phase transition involves propagation of particle asymmetries generated by reflection from the bubble walls into the unbroken phase....
$\Pi$ in the Sky ? Microwave Anisotropies from Cosmic Defects (1993)
Coulson, David, Ferreira, Pedro, Graham, Paul, Turok, Neil
High resolution maps of the anisotropy of the microwave sky will yield invaluable clues as to the mechanisms involved in cosmic structure formation. One fundamental question they should answer is...
A Simple Test for Non-Gaussianity in CMBR Measurements (1993)
Graham, Paul, Turok, Neil, Lubin, Philip, Schuster, Jeff
We propose a set of statistics $S_q$ for detecting non-gaussianity in CMBR anisotropy data sets. These statistics are both simple and, according to calculations over a space of linear combinations of...
Degree Scale Microwave Anisotropies in NonGaussian Theories of Cosmic Structure Formation (1993)
Coulson, David, Pen, Ue-Li, Turok, Neil
The COBE satellite's maps of the cosmic microwave background (CMB) anisotropy do not have the resolution to discriminate between theories of cosmic structure formation based on inflation, and those...
Family Symmetry, Fermion Mass Matrices and Cosmic Texture (1993)
The observed replication of fermions in three families is undoubtedly a reflection of a deeper symmetry underlying the standard model. In this paper we investigate one very elementary possibility,...