Wading the String Bog: CMB Birefringence in the Swampland

arXiv:2607.27318 · hep-th, astro-ph.CO, gr-qc, hep-ph · Submitted 2026-07-29 · Read on arXiv

Guido D'Amico, Nemanja Kaloper, Alexander Westphal

hep-th, astro-ph.CO, gr-qc, hep-ph

Submitted: 2026-07-29

Comments: 31 pages, 3 figures

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Terminology

• Domain Walls — 23× in this paper · explained in 2 episodes
• Quintessence — 22× in this paper · explained in 2 episodes
• Symmetry Breaking — 3× in this paper · explained in 3 episodes
• Anisotropic Cosmic Birefringence — 2× in this paper · explained in 1 episode
• Consistency — 2× in this paper · explained in 3 episodes
• Degeneracy — 2× in this paper · explained in 3 episodes
• Anisotropy — 1× in this paper · explained in 3 episodes
• Benchmark — 1× in this paper · explained in 2 episodes
• Boltzmann Equation — 1× in this paper · explained in 2 episodes
• Calibration — 1× in this paper · explained in 7 episodes
• Frequency Dependence — 1× in this paper · explained in 2 episodes
• Gauge Freedom — 1× in this paper · explained in 2 episodes
• Homogeneity — 1× in this paper · explained in 2 episodes
• Hubble Tension — 1× in this paper · explained in 9 episodes
• Phase Transitions — 1× in this paper · explained in 2 episodes

Sources

• The Cosmological Constant and the String Landscape
• DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
• The Hubble Tension and Early Dark Energy
• The String Landscape, Black Holes and Gravity as the Weakest Force
• Distance and de Sitter Conjectures on the Swampland
• On the Cosmological Implications of the String Swampland
• The Swampland: Introduction and Review
• Cosmology with Ultra-light Pseudo-Nambu-Goldstone Bosons
• Quintessence Axion Potential Induced by Electroweak Instanton Effects
• A Quintessential Axion
• Where in the String Landscape is Quintessence
• Strongly Coupled Quintessence
• Quintessence Axion Revisited in Light of Swampland Conjectures
• Discretely Evanescent Dark Energy
• On Super-Planckian Fields at Sub-Planckian Energies
• New physics from the polarised light of the cosmic microwave background
• Quintessence and the Rest of the World
• Cosmological Signature of New Parity-Violating Interactions
• Pseudoscalar perturbations and polarization of the cosmic microwave background
• New Extraction of the Cosmic Birefringence from the Planck 2018 Polarization Data

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