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Generation and Coherent Control of Pulsed Quantum Frequency Combs
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Effective scenario of loop quantum cosmology.

You Ding1, Yongge Ma, Jinsong Yang

  • 1Department of Physics, Beijing Normal University, Beijing 100875, China. youding@gmail.com

Physical Review Letters
|March 5, 2009
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Summary
This summary is machine-generated.

Loop quantum cosmology reveals that quantum gravity effects can cause a future collapse in expanding universes, potentially leading to a cyclic universe scenario with quantum bounces. This improved dynamics maintains a classical limit.

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Area of Science:

  • Cosmology
  • Quantum Gravity
  • Theoretical Physics

Background:

  • Loop quantum cosmology (LQC) offers a framework for quantizing cosmological models.
  • Understanding the classical limit of quantum cosmological models is crucial for their physical interpretation.
  • Previous models often focused on leading-order quantum corrections.

Purpose of the Study:

  • To investigate semiclassical states in isotropic LQC.
  • To derive the effective Hamiltonian incorporating next-to-leading order quantum corrections.
  • To explore the classical limit and potential future evolution of the universe.

Main Methods:

  • Utilizing semiclassical states within the framework of isotropic loop quantum cosmology.
  • Deriving an effective Hamiltonian that includes higher-order quantum corrections.
  • Analyzing the behavior of a Friedmann-Lemaître-Robertson-Walker universe with a massless scalar field.

Main Results:

  • The improved dynamics in LQC demonstrates the correct classical limit.
  • The effective Hamiltonian reveals significant departures from leading-order scenarios due to higher-order corrections.
  • A k=0 Friedmann universe may collapse in the future due to quantum gravity effects.

Conclusions:

  • Quantum gravity effects, including quantum bounces and collapses, can lead to a cyclic universe.
  • The inclusion of higher-order quantum corrections is essential for a complete understanding of cosmic evolution.
  • The semiclassicality of the model is maintained in the large-scale limit, supporting these findings.