The Limits of Quintessence (2009)
We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as...
Lower Limit to the Scale of an Effective Quantum Theory of Gravitation (2008)
An effective quantum theory of gravitation in which gravity weakens at energies higher than ~10^-3 eV is one way to accommodate the apparent smallness of the cosmological constant. Such a theory...
Observer dependence of the quasi-local energy and momentum in Schwarzschild space-time (2008)
The observer dependence of the quasi-local energy (QLE) and momentum in the Schwarzschild geometry is illustrated. Using the Brown-York prescription, the QLE for families of non-geodesic and geodesic...
A Test of the Copernican Principle (2007)
The blackbody nature of the cosmic microwave background (CMB) radiation spectrum is used in a modern test of the Copernican Principle. The reionized universe serves as a mirror to reflect CMB...
Anisotropy of the Cosmic Neutrino Background (2006)
Michney, R. J., Caldwell, R. R.
The cosmic neutrino background (CNB) consists of low-energy relic neutrinos which decoupled from the cosmological fluid at a redshift z ~ 10^{10}. Despite being the second-most abundant particles in...
Lower Limit to the Scale of an Effective Theory of Gravitation (2006)
We consider a linearized, effective quantum theory of gravitation in which gravity weakens at energies higher than ~10^-3 eV in order to accommodate the apparent smallness of the cosmological...
The Limits of Quintessence (2005)
Caldwell, R. R., Linder, Eric V.
We present evidence that the simplest particle-physics scalar-field models of dynamical dark energy can be separated into distinct behaviors based on the acceleration or deceleration of the field as...
DeDeo, Simon, Caldwell, R. R., Steinhardt, Paul J.
We consider how quintessence models in which the sound speed differs from the speed of light and varies with time affect the cosmic microwave background and the fluctuation power spectrum....
Gravitation of the Casimir Effect and the Cosmological Non-Constant (2002)
Whereas the total energy in zero-point fluctuations of the particle physics vacuum gives rise to the cosmological constant problem, differences in the vacuum give rise to real physical phenomena,...
Dave, Rahul, Caldwell, R. R., Steinhardt, Paul J.
We analyze the evolution of energy density fluctuations in cosmological scenarios with a mixture of cold dark matter and quintessence, in which the quintessence field is modeled by a constant...
Measuring the Speed of Sound of Quintessence (2001)
Erickson, Joel K., Caldwell, R. R., Steinhardt, Paul J., Armendariz-Picon, C., Mukhanov, V.
Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show...
Caldwell, R. R., Juszkiewicz, Roman, Steinhardt, Paul J., Bouchet, Francois
We propose a simple and accurate method for computing analytically the mass correlation function for cold dark matter and scale-free models that fits N-body simulations over a range that extends from...
It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort...
The Mass Power Spectrum in Quintessence Cosmological Models (1999)
Ma, Chung-Pei, Caldwell, R. R., Bode, Paul, Wang, Limin
We present simple analytic approximations for the linear and fully evolved nonlinear mass power spectrum for spatially flat cold dark matter (CDM) cosmological models with quintessence (Q)....
Cosmic Concordance and Quintessence (1999)
Wang, Limin, Caldwell, R. R., Ostriker, J. P., Steinhardt, Paul J.
We present a comprehensive study of the observational constraints on spatially flat cosmological models containing a mixture of matter and quintessence --- a time varying, spatially inhomogeneous...
The first space-based gravitational-wave detectors (1999)
Caldwell, R. R., Kamionkowski, Marc, Wadley, Leven
Gravitational waves provide a laboratory for general relativity and a window to energetic astrophysical phenomena invisible with electromagnetic radiation. Several terrestrial detectors are currently...
Cosmological Consequences of String-forming Open Inflation Models (1998)
Avelino, P. P., Caldwell, R. R.
We present a study of open inflation cosmological scenarios in which cosmic strings form betwen the two inflationary epochs. It is shown that in these models strings are stretched outside the horizon...
The First Space-Based Gravitational-Wave Detectors (1998)
Caldwell, R. R., Kamionkowski, Marc, Wadley, Leven
Gravitational waves provide a laboratory for general relativity and a window to energetic astrophysical phenomena invisible with electromagnetic radiation. Several terrestrial detectors are currently...
Resolving the Cosmological Missing Energy Problem (1998)
Huey, Greg, Wang, Limin, Dave, R., Caldwell, R. R., Steinhardt, Paul J.
Some form of missing energy may account for the difference between the observed cosmic matter density and the critical density. Two leading candidates are a cosmological constant and quintessence (a...
CMB anisotropy due to cosmic strings: Large angular scale (1998)
Allen, Bruce, Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
The Imprint of Gravitational Waves in Models Dominated by a Dynamical Cosmic Scalar Field (1997)
Caldwell, R. R., Steinhardt, Paul J.
An alternative to the standard cold dark matter model has been recently proposed in which a significant fraction of the energy density of the universe is due to a dynamical scalar field ($Q$) whose...
Cosmological Imprint of an Energy Component with General Equation of State (1997)
Caldwell, R. R., Dave, Rahul, Steinhardt, Paul J.
We examine the possibility that a significant component of the energy density of the universe has an equation-of-state different from that of matter, radiation or cosmological constant ($\Lambda$)....
Cosmic Strings in an Open Universe: Quantitative Evolution and Observational Consequences (1997)
Avelino, P. P., Caldwell, R. R.
The cosmic string scenario in an open universe is developed -- including the equations of motion, a model of network evolution, the large angular scale CMB temperature anisotropy, and the power...
Gravitational Waves From Cosmic Strings (1997)
Battye, R. A., Caldwell, R. R., Shellard, E. P. S.
Gravitational waves from cosmic strings are generated in the first fractions of a second after the Big Bang, potentially providing a unprecedented probe of the early universe. We discuss the key...
CMB Anisotropy Induced by Cosmic Strings on Angular Scales $>~ 15'$ (1997)
Allen, B., Caldwell, R. R., Dodelson, S., Knox, L., Shellard, E. P. S., Stebbins, A.
We have computed an estimate of the angular power spectrum of the Cosmic Microwave Background (CMB) induced by cosmic strings on angular scales $>~ 15'$, using a numerical simulation of a cosmic...
Cosmic Microwave Background Anisotropy Induced by Cosmic Strings on Angular Scales ≳15′ (1997)
Allen, Bruce, Caldwell, R. R., Dodelson, S., Knox, L., Shellard, E. P. S., Stebbins, A.
We have computed an estimate of the angular power spectrum of the cosmic microwave background induced by cosmic strings on angular scales ≳15′, using a numerical simulation of a cosmic string...
Large Angular Scale CMB Anisotropy Induced by Cosmic Strings (1996)
Allen, B., Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy...
Caldwell, R. R., Battye, R. A., Shellard, E. P. S.
We examine the spectrum of gravitational radiation emitted by a network of cosmic strings, with emphasis on the observational constraints and the opportunities for detection. The analysis improves...
Large Angular Scale Anisotropy in Cosmic Microwave Background Induced by Cosmic Strings (1996)
Allen, Bruce, Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
We simulate the anisotropy in the cosmic microwave background (CMB) induced by cosmic strings. By numerically evolving a network of cosmic strings we generate full-sky CMB temperature anisotropy...
On the Evolution of Scalar Metric Perturbations in an Inflationary Cosmology (1995)
We further clarify how scalar metric perturbations are amplified in an inflationary cosmology. We first construct a simple, analytic model of an inflationary cosmology in which the expansion scale...
Formation of Black Holes from Collapsed Cosmic String Loops (1995)
The fraction of cosmic string loops which collapse to form black holes is estimated using a set of realistic loops generated by loop fragmentation. The smallest radius sphere into which each cosmic...
Allen, Bruce, Caldwell, R. R., Koranda, Scott
Primordial gravitational waves are created during the de Sitter phase of an exponentially, expanding (inflationary) universe, due to quantum zero-point vacuum fluctuations. These waves produce...
Cosmic microwave background radiation anisotropy induced by cosmic strings (1995)
Allen, Bruce, Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
We report on a current investigation of the anisotropy pattern induced by cosmic strings on the cosmic microwave background radiation (MBR). We have numerically evolved a network of cosmic strings...
Cosmic strings confront COBE (1995)
Allen, Bruce, Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
We investigate large-angle anisotropies in the cosmic microwave radiation background which are induced by cosmic strings. We numerically evolve a string network from a redshift Z-100 to the present...
No Very Large Scale Structure in an Open Universe (1994)
Stebbins, Albert, Caldwell, R. R.
We study the effects of negative spatial curvature on the statistics of inhomogeneities in open cosmological models. In particular we examine the suppression of large-separation correlations in...
Cosmic Microwave Background Radiation Anisotropy Induced by Cosmic Strings (1994)
Allen, B., Caldwell, R. R., Shellard, E. P. S., Stebbins, A., Veeraraghavan, S.
We report on a current investigation of the anisotropy pattern induced by cosmic strings on the cosmic microwave background radiation (MBR). We have numerically evolved a network of cosmic strings...
Green's function for gravitational waves in FRW spacetimes (1993)
A method for calculating the retarded Green's function for the gravitational wave equation in Friedmann-Roberson-Walker spacetimes, within the formalism of linearized Einstein gravity is developed....
Constraints on Cosmic Strings due to Black Holes Formed from Collapsed Cosmic String Loops (1993)
The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict...
Cosmological constraints on cosmic-string gravitational radiation (1992)
The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed. The computation consists of a numerical integration of the...
Small-scale structure on a cosmic-string network (1991)
We construct an analytic model of the accumulation of small-scale structure on a cosmic-string network in an expanding universe. The structure is composed of kinks which form when the string segments...
Kinky structure on strings (1991)
The evolution of the linear density of kinks on a cosmic string network is examined, and new possibilities about the behavior of the string network are considered. These include (1) allowing kinky...
Generation of structure on a cosmic-string network (1990)
When cosmic strings cross and intercommute, four kinks are created. We calculate the linear density of these kinks, K(t), in an expanding universe. After a period of rapid initial growth, K(t)...