AT1 - Extended Theories of Gravity and Quantum Cosmology |
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Speaker |
Choudhury, Sayantan |
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Coauthors |
Sayantan Choudhury, Sudhakar Panda |
| Talk Title |
Spectrum of cosmological correlation from vacuum fluctuation of Stringy Axion in entangled de Sitter space |
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Abstract |
In this work, we study the impact of quantum entanglement on the two-point correlation function and the associated primordial power spectrum of mean square vacuum fluctuation in a bipartite quantum field theoretic system in presence of axion originating from {\bf Type IIB} string theory. Compared to the usual approach followed in (primordial) cosmology here we use most elegant and technically correct methods to compute the expression for the power spectrum of vacuum fluctuation. For this computation, we consider two causally separated region ({\bf L} and {\bf R}) in open hyperbolic chart of the de Sitter space-time. We start our analysis with three approaches -1. field operator expansion (FOE) technique with the quantum entangled state, 2. reduced density matrix (RDM) formalism with mixed quantum state and 3. non-entangled state (NES) method. For FOE and RDM we are tracing out the physical information from of one of the regions ({\bf R} ) and for NES we consider the Hilbert space is only described by region {\bf L} in de Sitter hyperbolic open chart. For massless ($\nu=3/2$) axion field we get the exact scale invariant feature of the power spectrum on small scale from this three formalism at the leading order which is consistent with the finding of the observational probes for early universe cosmology. Additionally, we due to quantum entanglement we get different quantum correction terms in the power spectrum for these thee formalisms at the next to leading order. Such correction terms serve the purpose of the breaking of degeneracy among the outcomes of the FOE, RDM and NES formalisms in the superhorizon limit. On the other hand, for massive ($\nu\neq 3/2$) axion filed we get a slight deviation from scale invariance and exactly quantify the spectral tilt of the power spectrum in small scales. Apart from that, for massless ($\nu=3/2$) and massive ($\nu=3/2$) axion field, we find distinguishable features of the power spectrum for the FOE, RDM, and NES on the large scales, which is the outcome of quantum entanglement. We also find that such large-scale effects are comparable to or greater than the curvature radius of de Sitter space. |
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