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We re-examine the process of loop quantization for flat isotropic models in cosmology. In particular, we contrast different inequivalent `loop quantizations' of these simple models through their respective successes and limitations and…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Alejandro Corichi , Parampreet Singh

Structure in the Universe is widely believed to have originated from quantum fluctuations during an early epoch of accelerated expansion. Yet, the patterns we observe today do not distinguish between quantum or classical primordial…

High Energy Physics - Theory · Physics 2020-07-01 Daniel Green , Rafael A. Porto

In loop quantum cosmology (LQC) the big bang is replaced by a quantum bounce which is followed by a robust phase of super-inflation. Rather than growing unboundedly in the past, the Hubble parameter \emph{vanishes} at the bounce and attains…

General Relativity and Quantum Cosmology · Physics 2014-11-20 Abhay Ashtekar , David Sloan

Loop quantum cosmology predicts that quantum gravity effects resolve the big-bang singularity and replace it by a cosmic bounce. Furthermore, loop quantum cosmology can also modify the form of primordial cosmological perturbations, for…

General Relativity and Quantum Cosmology · Physics 2017-06-28 Edward Wilson-Ewing

Quantum simulations of Lattice Gauge Theories (LGTs) are often formulated on an enlarged Hilbert space containing both physical and unphysical sectors in order to retain a local Hamiltonian. We provide simple fault-tolerant procedures that…

Quantum Physics · Physics 2022-11-21 Abhishek Rajput , Alessandro Roggero , Nathan Wiebe

A key result of isotropic loop quantum cosmology is the existence of a quantum bounce which occurs when the energy density of the matter field approaches a universal maximum close to the Planck density. Though the bounce has been exhibited…

General Relativity and Quantum Cosmology · Physics 2015-06-18 Peter Diener , Brajesh Gupt , Parampreet Singh

Quantum cosmology in the presence of a fundamental minimal length is analyzed in the context of the flat isotropic and the Taub cosmological models. Such minimal scale comes out from a generalized uncertainty principle and the quantization…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Marco Valerio Battisti , Giovanni Montani

I present a streamlined review of how the separate universe approach to cosmological perturbation theory can be used to study the dynamics of long-wavelength scalar perturbations in loop quantum cosmology, and then use it to calculate how…

General Relativity and Quantum Cosmology · Physics 2016-08-03 Edward Wilson-Ewing

We consider the quantum and classical Liouville dynamics of a non-integrable model of two coupled spins. Initially localised quantum states spread exponentially to the system dimension when the classical dynamics are chaotic. The long-time…

Quantum Physics · Physics 2009-11-07 J. Emerson , L. E. Ballentine

Quantum cosmology is the quantum theory of the entire universe. Although strange at first sight, it is appropriate because (1) our world appears to be fundamentally quantum, (2) the classical description of gravity breaks down at…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Don N. Page

With the decline of the Copenhagen interpretation of quantum mechanics and the recent experiments indicating that quantum mechanics does actually embody 'objective reality', one might ask if a 'mechanical', conceptual model for quantum…

Quantum Physics · Physics 2014-06-23 Carl Frederick

We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion (E.G. Cavalcanti and M. Reid, Phys. Rev. Lett. 97, 170405 (2006)). The macroscopic coherence stems from…

Three of the big puzzles of theoretical physics are the following: (i) There is apparently no time evolution in the dynamics of quantum general relativity, because the allowed quantum states must obey the Hamiltonian constraint. (ii) During…

General Relativity and Quantum Cosmology · Physics 2015-12-29 Shreya Banerjee , Sayantani Bera , Tejinder P. Singh

In this paper, we first provide a brief review of the effective dynamics of two recently well-studied models of modified loop quantum cosmologies (mLQCs), which arise from different regularizations of the Hamiltonian constraint and show the…

General Relativity and Quantum Cosmology · Physics 2021-06-25 Bao-Fei Li , Parampreet Singh , Anzhong Wang

The occurrence of singularities where spacetime curvature becomes infinite and geodesic evolution breaks down are inevitable events in classical general relativity (GR) unless one chooses an exotic matter violating weak energy condition.…

General Relativity and Quantum Cosmology · Physics 2024-11-05 Bao-Fei Li , Parampreet Singh

Randomness is a key feature of quantum physics. Heisenberg's uncertainty principle reveals the existence of an intrinsic noise, usually explored through Gaussian squeezed states. Due to their insufficiency for quantum advantage, the focus…

Quantum Physics · Physics 2025-11-20 Vojtěch Kala , Jiří Fadrný , Michal Neset , Jan Bílek , Petr Marek , Miroslav Ježek

The precision of a quantum sensor can overcome its classical counterpart when its constituents are entangled. In gaussian squeezed states, quantum correlations lead to a reduction of the quantum projection noise below the shot noise limit.…

Generalized coherent states (GCs) under deformed quantum mechanics which exhibits intrinsic minimum length and maximum momentum have been well studied following Gazeau-Klauder approach. In this paper, as an extension to the study of quantum…

General Relativity and Quantum Cosmology · Physics 2019-10-30 Chee Leong Ching , Wei Khim Ng

We investigate bosonic Gaussian quantum states on an infinite cubic lattice in arbitrary spatial dimensions. We derive general properties of such states as ground states of quadratic Hamiltonians for both critical and non-critical cases.…

Quantum Physics · Physics 2012-01-23 Norbert Schuch , J. Ignacio Cirac , Michael M. Wolf

In the matter bounce scenario, a dust-dominated contracting space-time generates scale-invariant perturbations that, assuming a nonsingular bouncing cosmology, propagate to the expanding branch and set appropriate initial conditions for the…

General Relativity and Quantum Cosmology · Physics 2015-06-12 Edward Wilson-Ewing