1 / 14

Can we go beyond a semiclassical description of cosmology?

Explore the limitations of semiclassical descriptions in cosmology, delving into the role of quantum gravity and the entangled states of separate CFTs on Hd boundaries. Investigate how density matrices describe spacetime patches and the emergence of spacetime from quantum entanglement.

leane
Download Presentation

Can we go beyond a semiclassical description of cosmology?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Can we go beyond a semiclassical description of cosmology? Mark Van Raamsdonk (UBC) CIFAR 2012 1/2

  2. no 2/2

  3. Should we care?

  4. Yes: • Still some major theoretical issues that a • semiclassical description can’t address: • e.g.: • cosmological constant problem • validity of effective field theory • initial conditions/ likelihood of inflation Can we come up with a consistent theoretical framework for cosmology (fully consistent theoretical mode including quantum gravity)?

  5. Doesn’t string theory provide such a framework? • Nonperturbative description available only for • special cases (e.g. asymptotically AdS): • AdS/CFT or gauge-theory / gravity duality

  6. Cosmological spacetimes: typically have horizons • No single observer has access to full spacetime.

  7. AdS analog: accelerating observers • Each observer has access to part of spacetime bounded by a horizon.

  8. Each wedge: asymptotically AdSspacetime with boundary Hd New description: Entangled state of two separate CFTs on Hd -each side described by thermal density matrix -``Rindler” description of AdS

  9. General story: certain patches of spacetime described by density matrices (mixed states).

  10. Interesting feature: patches connected together by entanglement of non-perturbative degrees of freedom e.g. : what happens if we disentangle two sides? Emergence of spacetime ↔ quantum entanglement

  11. Can we describe finite patches? Want a density matrix that describes only the IR degrees of freedom (finitely many). Such an object naturally associated with low-energy effective action.

  12. Best guess for full description: Regions inside horizons associated with density matrices describing finitely many degrees of freedom. Maybe no global description. Entanglement between degrees of freedom for different patches carries information about how full spacetime is pieced together. Requirement of nice global spacetime places constraints on what density matrices are allowed and how the various degrees of freedom are entangled.

  13. Thanks!

More Related