Latham Boyle

Relating gravitational wave constraints from primordial nucleosynthesis, pulsar timing, laser interferometers, and the CMB: Implications for the early universe

gw 0 (f1) and gw 0 (f2). Here r is the so-called “tensor-to-scalar ratio,” which is constrained by cosmic-microwave-background (CMB) experiments; and gw (f) is the energy spectrum of primordial gravitational-waves, which is constrained e.g. by pulsar-timing (PT) measurements, laser-interferometer (LI) experiments, and the standard Big Bang Nucleosynthesis (BBN) bound. Differentiating the master equation yields a new expression for the tilt dln gw (f)/dlnf of the present-day gravitational-wave spectrum. The relationship between r and gw (f) depends sensitively on the uncertain physics of the early universe, and we show that this uncertainty may be encapsulated (in a model-independent way) by two quantities: ˆ w(f) and ˆ nt(f), where ˆ nt(f) is a certain logarithmic average over nt(k) (the primordial tensor spectral index); and ˆ w(f) is a certain logarithmic average over ˜ w(a) (the effective equation-of-state parameter in the early universe, after horizon re-entry). Here the effective equation-of-state parameter ˜ w(a) is a combination of the ordinary equation-of-state parameter w(a) and the bulk viscosity �(a). Thus, by comparing observational constraints on r and gw (f), one obtains (remarkably tight) constraints in the { ˆ w(f), ˆ nt(f)} plane. In particular, this is the best way to constrain (or detect) the presence of a “stiff” energy component (with w > 1/3) in the early universe, prior to BBN. (The discovery of such a component would be no more surprising than the discovery of a tiny cosmological constant at late times!) Finally, although most of our analysis does not assume inflation, we point out that if CMB experiments detect a non-zero value for r, then we will immediately obtain (as a free by-product) a new upper bound ˆ w < 0.55 on the logarithmically averaged effective equation-of-state parameter during

New duality relating density perturbations in expanding and contracting Friedmann cosmologies

For a 4-dimensional spatially-flat Friedmann-Robertson-Walker universe with a scalar field

Binary–Black-Hole Merger: Symmetry and the Spin Expansion

\phi(x)

Quantifying the BICEP2-Planck tension over gravitational waves.

, potential

Rethinking Connes? Approach to the Standard Model of Particle Physics Via Non-Commutative Geometry

V(\phi)

Testing and extending the inflationary consistency relation for tensor modes

and constant equation of state

Non-Associative Geometry and the Spectral Action Principle

w=p/\rho

A new algebraic structure in the standard model of particle physics

, we show that an expanding solution characterized by

Longer Baseline Telescope Arrays Using Quantum Repeaters

\epsilon=3(1+w)/2

Cosmic gravitational-wave background in a cyclic universe

produces the same scalar perturbations as a contracting solution with