Orbital phase in inspiralling compact binaries

Orbital precession due to central-force perturbations

Orbital Tests of Relativistic Gravity using Artificial Satellites

Orbiting binary black hole evolutions with a multipatch high order finite-difference approach

Orbits in a non-Kerr Dynamical System

Orbits in the Field of a Gravitating Magnetic Monopole

Orbits of particles in noncommutative Schwarzschild spacetime

Orbits, forces and accretion dynamics near spinning black holes

Ordinary Matter in Nonlinear Affine Gauge Theories of Gravitation

Oriented Matroids -- Combinatorial Structures Underlying Loop Quantum Gravity

Origin of Classical Singularities

Origin of FRW cosmology in slow-roll inflation from noncompact Kaluza-Klein theory

Origin of holographic dark energy models

Origin of Structure in a Supersymmetric Quantum Universe

Origin of the Immirzi Parameter

Origin of the inflationary Universe

Origin of the Thermal Radiation in a Solid-State Analog of a Black-Hole

Orthogonal decomposition of Lorentz transformations

Orthonormal Frame and SO(3) Kaluza-Klein Dyon

Oscillating Friedman Cosmology