Gravitational Absorption Lines

Abstract

We consider the gravitational analogue of Lyman-alpha absorption lines in astronomical spectroscopy. If Einstein gravity with minimally coupled matter is valid up to the Planck scale, quantum bound states absorb gravitons of a specific frequency with Planckian cross section, ${\sigma }_{\text{abs}}\approx l_p^2$. Consequently, one can show that gravitational absorption by bound states is inefficient in ordinary gravity. If observed, gravitational absorption lines would therefore constitute a powerful smoking gun of new exotic astrophysical bound states (near extremal bound states) or new gravitational physics, as well as give direct evidence of the quantized nature of the gravitational field. We provide, as an example of new gravitational physics near the Planck scale, a non-minimal coupling of the matter fields which breaks the equivalence principle on-shell. We lay out a model in which absorption lines in the primordial gravitational wave spectrum are produced as a consequence of this coupling.

33 pages, 2 figures. Added one reference and an additional section in the appendix. Version accepted for publication in PRD

References in corpus (15)

• The Hierarchy Problem and New Dimensions at a Millimeter
• Cosmological Backgrounds of Gravitational Waves
• Discovering the QCD Axion with Black Holes and Gravitational Waves
• New constraints on primordial gravitational waves from Planck 2015
• Can Gravitons Be Detected?
• Using Cosmology to Establish the Quantization of Gravity
• Aspects of Graviton Detection: Graviton Emission and Absorption by Atomic Hydrogen
• Gravitational Waves in Cold Dark Matter
• Higher-derivative operators and effective field theory for general scalar-tensor theories
• Damping of gravitational waves by matter
• Black Hole Masses are Quantized
• Absorption of Gravitational Waves from Distant Sources
• A probabilistic model for learning in cortical microcircuit motifs with data-based divisive inhibition
• Gravitational Atoms
• Quantum Field Theory with Classical Sources - Linearized Quantum Gravity

Cited by in corpus (6)

• A Simple Derivation of the Gertsenshtein Effect
• Graviton-Photon Oscillations in an Expanding Universe
• Graviton-Photon Oscillations as a Probe of Quantum Gravity
• Theoretical Radio Signals from Radio-Band Gravitational Waves Converted from the Neutron Star Magnetic Field
• Autocatalysis of Graviton Production via the Gertsenshtein Effect for the Yang-Mills Field
• Infeasibility of Graviton Detection as Cosmic Censorship