Probing the early universe with inflationary gravitational waves

By Latham Boyle, Paul J. Steinhardt. 2005

214 citations recorded by the source corpus.

Near comoving wave number $k$, the gravitational-wave background (GWB) from inflation carries information about the physical conditions near two moments in cosmic history: the moment when $k$ ``left the horizon'' during inflation, and the moment when it ``re-entered the horizon'' after inflation. We investigate the extent to which this information can be extracted if the GWB is measured by a combination of cosmic-microwave-background polarization experiments on large scales and space-based laser-interferometer experiments on small scales. To disentangle this information, we derive a new gravitational-wave transfer function that incorporates a number of physical effects that were treated less accurately, less generally, or were missing altogether in previous treatments. In particular, it incorporates: (i) dark energy with time-varying equation of state $w(z)$; (ii) tensor anisotropic stress due to free-streaming relativistic particles in the early universe; and (iii) a variety of physical effects that cause deviations from the standard equation of state $w=1/3$ during the radiation era. Based on this transfer function, we consider the degree to which the GWB can be used to test inflation and to probe the ``primordial dark age'' between the end of inflation and the electroweak phase transition.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Oceanography

View Paper: https://www.semanticscholar.org/paper/1e7bda9d455a7999ec8505989af4027bc1633437

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. Marco Peloso
2. E. Pajer
3. N. Barnaby
4. J. Pritchard
5. Peter Adshead
6. R. Cai
7. Abraham Loeb
8. Zongkuan Guo

In Nuclear and High Energy Physics

1. Marco Peloso
2. E. Pajer
3. N. Barnaby
4. J. Pritchard
5. Peter Adshead
6. Abraham Loeb
7. R. Cai
8. Zongkuan Guo

In Oceanography

1. Zongkuan Guo
2. K. Saikawa
3. E. Pajer
4. Marco Peloso
5. Abraham Loeb
6. N. Barnaby
7. R. Cai
8. R. Easther

Citations in the corpus

• Gauge Field Production in Axion Inflation: Consequences for Monodromy, non-Gaussianity in the CMB, and Gravitational Waves at Interferometers (2011, background): “[36, 37]) for modes that re-entered the horizon during radiation domination, as it is the case for the modes relevant for interferometers, one finds”
• Primordial gravitational waves, precisely: the role of thermodynamics in the Standard Model (2018, background): “In addition to such an effect, Boyle and Steinhardt [30] explored general possibilities that the equation of state might be modified by some non-trivial features of interacting particles.”
• Inflation and the scale dependent spectral index: prospects and strategies (2010, background): “the equation of state, and need the full transfer function — this distinction will be important for direct detection gravitational wave experiments [39, 40].”
• Taiji program: Gravitational-wave sources (2018, background): “Since tensor perturbations begin to oscillate with the amplitude damped by a factor a−1 after reentering the Hubble horizon at the epoch of radiation or matter dominance, for the slightly red-tilted spectrum, the energy spectrum of GWs in the frequency range of 10−10 − 10(3) Hz at present becomes to”
• The Gravitational-Wave Physics (2017, background): “Unfortunately, for the nearly scale-invariant tensor spectrum predicted by the single-field slow-roll inflationary models, the energy spectrum in the frequency range of 10−10 ∼ 103 Hz at present becomes too weak to be directly detected by pulsar timing array (PTA) experiments and laser interferomete”
• Inflation, Cosmic Perturbations and Non-Gaussianities (2013, unknown): “[90]).”