We study the phenomenology of a recent string construction with a quantum mechanically stable dark energy. A mild supersymmetry protects the vacuum energy but also allows O(10−100) TeV scale superpartner masses. The construction is holographic in the sense that the 4D spacetime is generated from “spacetime pixels” originating from five-branes wrapped over metastable five-cycles of the compactification. The cosmological constant scales as 𝚲Λ~1∕N in the pixel number. An instability in the construction leads to cosmic expansion. This also causes more five-branes to wind up in the geometry, leading to a slowly decreasing cosmological constant which we interpret as an epoch of inflation followed by (pre-)heating when a rare event occurs in which the number of pixels increases by an order one fraction. The sudden appearance of radiation triggers an exponential increase in the number of pixels. Dark energy has a time varying equation of state with wa = −3Ωm,0(1 + w0)/2, which is compatible with current bounds, and could be constrained further by future data releases. The pixelated nature of the Universe also implies a large-l cutoff on the angular power spectrum of cosmological observables with lmax ~ O(N). We also use this pixel description to study the thermodynamics of de Sitter space, finding rough agreement with effective field theory considerations.
Heckman J.J., Lawrie C., Lin L., Sakstein J., Zoccarato G. (2019). Pixelated Dark Energy. FORTSCHRITTE DER PHYSIK, 67(11), 1-25 [10.1002/prop.201900071].
Pixelated Dark Energy
Lin L.;
2019
Abstract
We study the phenomenology of a recent string construction with a quantum mechanically stable dark energy. A mild supersymmetry protects the vacuum energy but also allows O(10−100) TeV scale superpartner masses. The construction is holographic in the sense that the 4D spacetime is generated from “spacetime pixels” originating from five-branes wrapped over metastable five-cycles of the compactification. The cosmological constant scales as 𝚲Λ~1∕N in the pixel number. An instability in the construction leads to cosmic expansion. This also causes more five-branes to wind up in the geometry, leading to a slowly decreasing cosmological constant which we interpret as an epoch of inflation followed by (pre-)heating when a rare event occurs in which the number of pixels increases by an order one fraction. The sudden appearance of radiation triggers an exponential increase in the number of pixels. Dark energy has a time varying equation of state with wa = −3Ωm,0(1 + w0)/2, which is compatible with current bounds, and could be constrained further by future data releases. The pixelated nature of the Universe also implies a large-l cutoff on the angular power spectrum of cosmological observables with lmax ~ O(N). We also use this pixel description to study the thermodynamics of de Sitter space, finding rough agreement with effective field theory considerations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
