Skip to content
DraconiticResearch
Search Sources API
186,625 studies31 sourcesUpdated 7 min ago
Peer-reviewedCC BYJournal of High Energy Physics

Sphere amplitudes and observing the universe’s size

  • Andreas Blommaert1
  • Adam Levine2
  1. 1Institute for Advanced Study
  2. 2Massachusetts Institute of Technology
Open at sourcePDFDOICite

Abstract

A bstract Sine dilaton gravity is holographically related to DSSYK. We explain how to interpret sine dilaton as 2d quantum cosmology. This paves the way for using two copies of DSSYK as hologram for Big-Bang cosmologies. We study the most basic cosmological observable: the sphere amplitude. Via canonical quantization we find a finite answer that matches the on-shell action of a dual matrix integral. The sphere amplitude (or the norm of the no-boundary wavefunction) also gives a prediction for the universe’s size. In the context of slow-roll inflation, the no-boundary state is non-normalizable, and predicts a small universe, in contradiction with experiments. We argue that an avatar of these issues exists in dS JT gravity. By considering sine dilaton as a UV completion of dS JT gravity, the state becomes normalizable. We then consider the observer’s no-boundary state and show that this prefers neither small nor large universes. The resulting distribution is flat.

Related

  1. The Disordered Universe 2025: Analytic Properties of Amplitudes and Correlators
    Mattia Capuano, Chandramouli Chowdhury, Chantelle Esper +6
    arXivPreprintarXiv licenceFull textMathematical physicsGravitation & general relativityarXiv
  2. The Halperin (111) state as a paired composite-fermion wave function: Two exact finite-size identities on the sphere
    Glenn Wagner
    arXivPreprintarXiv licenceFull textCondensed matterarXiv
  3. Predicting the conditions for observing the Mpemba effect
    Yue Liu, Tan van Vu, Raphaël Chétrite +2
    HALPreprintLicence not statedGeneral physicsHAL
  4. Excursion-Resolved Thermodynamic Inference without Observing Reverse Transitions
    Jie Gu
    arXivPreprintCC BY 4.0Full textStatistical & nonlinear physicsarXiv
  5. Observing oscillations using the non-magnetic and magnetic spin Hall effect in a non-collinear antiferromagnet
    Monalisa Cavalcante, José Laurentino, Carlos Eduardo +2
    arXivPreprintarXiv licenceFull textApplied physics & instrumentationCondensed matterarXiv

Cite

BibTeXRIS
BibTeX
@article{blommaert2026sphere,
  title = {{Sphere amplitudes and observing the universe’s size}},
  author = {Andreas Blommaert and Adam Levine},
  journal = {Journal of High Energy Physics},
  year = {2026},
  month = jul,
  doi = {10.1007/jhep07(2026)136},
  url = {https://doi.org/10.1007/jhep07(2026)136},
  note = {CC BY},
}
RIS
TY  - JOUR
TI  - Sphere amplitudes and observing the universe’s size
AU  - Andreas Blommaert
AU  - Adam Levine
PY  - 2026
DA  - 2026/07/15
JO  - Journal of High Energy Physics
DO  - 10.1007/jhep07(2026)136
UR  - https://doi.org/10.1007/jhep07(2026)136
AB  - A bstract Sine dilaton gravity is holographically related to DSSYK. We explain how to interpret sine dilaton as 2d quantum cosmology. This paves the way for using two copies of DSSYK as hologram for Big-Bang cosmologies. We study the most basic cosmological observable: the sphere amplitude. Via canonical quantization we find a finite answer that matches the on-shell action of a dual matrix integral. The sphere amplitude (or the norm of the no-boundary wavefunction) also gives a prediction for the universe’s size. In the context of slow-roll inflation, the no-boundary state is non-normalizable, and predicts a small universe, in contradiction with experiments. We argue that an avatar of these issues exists in dS JT gravity. By considering sine dilaton as a UV completion of dS JT gravity, the state becomes normalizable. We then consider the observer’s no-boundary state and show that this prefers neither small nor large universes. The resulting distribution is flat.
SN  - 1029-8479
SN  - 1126-6708
SN  - 1127-2236
ER  -