scholarly journals Quantum groups and polymer quantum mechanics

2021 ◽  
Author(s):  
G. Acquaviva ◽  
A. Iorio ◽  
L. Smaldone
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Quantum Groups ◽  
Loop Quantum Gravity ◽  
Quantization Scheme ◽  
Creation And Annihilation Operators

In Polymer Quantum Mechanics, a quantization scheme that naturally emerges from Loop Quantum Gravity, position and momentum operators cannot be both well defined on the Hilbert space [Formula: see text]. It is henceforth deemed impossible to define standard creation and annihilation operators. In this paper, we show that a [Formula: see text]-oscillator structure, and hence [Formula: see text]-deformed creation/annihilation operators, can be naturally defined on [Formula: see text], which is then mapped into the sum of many copies of the [Formula: see text]-oscillator Hilbert space. This shows that the [Formula: see text]-calculus is a natural calculus for Polymer Quantum Mechanics. Moreover, we show that the inequivalence of different superselected sectors of [Formula: see text] is of topological nature.

Polymer quantization effects on gauge-flation

2018 ◽  
Vol 15 (10) ◽  
pp. 1850169
Author(s):  
M. Mardaani ◽  
K. Nozari
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Gauge Field ◽  
Quantum Cosmology ◽  
Loop Quantum Gravity ◽  
Loop Quantum Cosmology ◽  
Abelian Gauge ◽  
Friedmann Equations ◽  
Cosmological Inflation

Polymer quantum mechanics, as a non-standard representation of quantum mechanics, is based on a symmetric sector of loop quantum gravity known as loop quantum cosmology. In this work, by analyzing the Hamiltonian and Friedmann equations in the standard Hilbert space and polymer Hilbert space, we show that polymer quantization is a successful formalism for a non-Abelian gauge field driving the cosmological inflation, the so-called gauge-flation, in order to remove initial singularity and also keeping the inflationary trajectories in this model as attractors of dynamics after the bounce.

scholarly journals A CLASS OF GUP SOLUTIONS IN DEFORMED QUANTUM MECHANICS

2010 ◽  
Vol 19 (12) ◽  
pp. 2003-2009 ◽  
Author(s):  
POURIA PEDRAM
Keyword(s):  
Black Hole ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Uncertainty Principle ◽  
Loop Quantum Gravity ◽  
Black Hole Physics ◽  
Generalized Uncertainty Principle ◽  
Heisenberg Uncertainty Principle ◽  
Deformed Algebra ◽  
Heisenberg Uncertainty

Various candidates of quantum gravity such as string theory, loop quantum gravity and black hole physics all predict the existence of a minimum observable length which modifies the Heisenberg uncertainty principle to the so-called generalized uncertainty principle (GUP). This approach results from the modification of the commutation relations and changes all Hamiltonians in quantum mechanics. In this paper, we present a class of physically acceptable solutions for a general commutation relation without directly solving the corresponding generalized Schrödinger equations. These solutions satisfy the boundary conditions and exhibit the effect of the deformed algebra on the energy spectrum. We show that this procedure prevents us from doing equivalent but lengthy calculations.

scholarly journals Misleading inferences from discretization of empty spacetime: Snyder-noncommutativity case study

2015 ◽  
Vol 24 (10) ◽  
pp. 1550073 ◽  
Author(s):  
Giovanni Amelino-Camelia ◽  
Valerio Astuti
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Recent Progress ◽  
Covariant Formulation ◽  
Specific Context ◽  
Intrinsic Interest ◽  
Alternative Approaches

Alternative approaches to the study of the quantum gravity problem are handling the role of spacetime very differently. Some are focusing on the analysis of one or another novel formulation of "empty spacetime", postponing to later stages the introduction of particles and fields, while other approaches assume that spacetime should only be an emergent entity. We here argue that recent progress in the covariant formulation of quantum mechanics, suggests that empty spacetime is not physically meaningful. We illustrate our general thesis in the specific context of the noncommutative Snyder spacetime, which is also of some intrinsic interest, since hundreds of studies were devoted to its analysis. We show that empty Snyder spacetime, described in terms of a suitable kinematical Hilbert space, is discrete, but this is only a formal artifact: the discreteness leaves no trace on the observable properties of particles on the physical Hilbert space.

scholarly journals FUNDAMENTAL STRUCTURE OF LOOP QUANTUM GRAVITY

2007 ◽  
Vol 16 (09) ◽  
pp. 1397-1474 ◽  
Author(s):  
MUXIN HAN ◽  
YONGGE MA ◽  
WEIMING HUANG
Keyword(s):  
General Relativity ◽  
Quantum Mechanics ◽  
Quantum Theory ◽  
Quantum Gravity ◽  
Quantum Dynamics ◽  
Loop Quantum Gravity ◽  
Hamiltonian Constraint ◽  
Dimensional Manifold ◽  
Fundamental Structure ◽  
Fundamental Scale

In the recent twenty years, loop quantum gravity, a background independent approach to unify general relativity and quantum mechanics, has been widely investigated. The aim of loop quantum gravity is to construct a mathematically rigorous, background independent, non-perturbative quantum theory for a Lorentzian gravitational field on a four-dimensional manifold. In the approach, the principles of quantum mechanics are combined with those of general relativity naturally. Such a combination provides us a picture of, so-called, quantum Riemannian geometry, which is discrete on the fundamental scale. Imposing the quantum constraints in analogy from the classical ones, the quantum dynamics of gravity is being studied as one of the most important issues in loop quantum gravity. On the other hand, the semi-classical analysis is being carried out to test the classical limit of the quantum theory. In this review, the fundamental structure of loop quantum gravity is presented pedagogically. Our main aim is to help non-experts to understand the motivations, basic structures, as well as general results. It may also be beneficial to practitioners to gain insights from different perspectives on the theory. We will focus on the theoretical framework itself, rather than its applications, and do our best to write it in modern and precise langauge while keeping the presentation accessible for beginners. After reviewing the classical connection dynamical formalism of general relativity, as a foundation, the construction of the kinematical Ashtekar–Isham–Lewandowski representation is introduced in the content of quantum kinematics. The algebraic structure of quantum kinematics is also discussed. In the content of quantum dynamics, we mainly introduce the construction of a Hamiltonian constraint operator and the master constraint project. At last, some applications and recent advances are outlined. It should be noted that this strategy of quantizing gravity can also be extended to obtain other background-independent quantum gauge theories. There is no divergence within this background-independent and diffeomorphism-invariant quantization program of matter coupled to gravity.

scholarly journals Loop Quantum Black Hole Extensions Within the Improved Dynamics

2021 ◽  
Vol 8 ◽  
Author(s):  
Rodolfo Gambini ◽  
Javier Olmedo ◽  
Jorge Pullin
Keyword(s):  
Black Hole ◽  
Quantum Gravity ◽  
Loop Quantum Gravity ◽  
Space Time ◽  
Anisotropic Fluid ◽  
Spherically Symmetric ◽  
Quantization Scheme ◽  
White Hole ◽  
Quantum Black Hole ◽  
Black Hole Singularity

We continue our investigation of an improved quantization scheme for spherically symmetric loop quantum gravity. We find that in the region where the black hole singularity appears in the classical theory, the quantum theory contains semi-classical states that approximate general relativity coupled to an effective anisotropic fluid. The singularity is eliminated and the space-time can be continued into a white hole space-time. This is similar to previously considered scenarios based on a loop quantum gravity quantization.

scholarly journals Differential representations of dynamical oscillator symmetries in discrete Hilbert space

2000 ◽  
Vol 5 (2) ◽  
pp. 97-106
Author(s):  
Andreas Ruffing
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Discrete Spectrum ◽  
Classical Limit ◽  
Heisenberg Algebra ◽  
Space Structure ◽  
Hermite Functions ◽  
Dynamical Symmetries ◽  
Creation And Annihilation Operators

As a very important example for dynamical symmetries in the context ofq-generalized quantum mechanics the algebraaa†−q−2a†a=1is investigated. It represents the oscillator symmetrySUq(1,1)and is regarded as a commutation phenomenon of theq-Heisenberg algebra which provides a discrete spectrum of momentum and space,i.e., a discrete Hilbert space structure. Generalizedq-Hermite functions and systems of creation and annihilation operators are derived. The classical limitq→1is investigated. Finally theSUq(1,1)algebra is represented by the dynamical variables of theq-Heisenberg algebra.

scholarly journals PSEUDO-HERMITIAN REPRESENTATION OF QUANTUM MECHANICS

2010 ◽  
Vol 07 (07) ◽  
pp. 1191-1306 ◽  
Author(s):  
ALI MOSTAFAZADEH
Keyword(s):  
Hilbert Space ◽  
Quantum Mechanics ◽  
Quantum Chaos ◽  
Relativistic Quantum ◽  
Canonical Quantization ◽  
Inner Product ◽  
Relativistic Quantum Mechanics ◽  
Real Spectrum ◽  
Quantization Scheme

A diagonalizable non-Hermitian Hamiltonian having a real spectrum may be used to define a unitary quantum system, if one modifies the inner product of the Hilbert space properly. We give a comprehensive and essentially self-contained review of the basic ideas and techniques responsible for the recent developments in this subject. We provide a critical assessment of the role of the geometry of the Hilbert space in conventional quantum mechanics to reveal the basic physical principle motivating our study. We then offer a survey of the necessary mathematical tools, present their utility in establishing a lucid and precise formulation of a unitary quantum theory based on a non-Hermitian Hamiltonian, and elaborate on a number of relevant issues of fundamental importance. In particular, we discuss the role of the antilinear symmetries such as [Formula: see text], the true meaning and significance of the so-called charge operators [Formula: see text] and the [Formula: see text]-inner products, the nature of the physical observables, the equivalent description of such models using ordinary Hermitian quantum mechanics, the pertaining duality between local-non-Hermitian versus nonlocal-Hermitian descriptions of their dynamics, the corresponding classical systems, the pseudo-Hermitian canonical quantization scheme, various methods of calculating the (pseudo-) metric operators, subtleties of dealing with time-dependent quasi-Hermitian Hamiltonians and the path-integral formulation of the theory, and the structure of the state space and its ramifications for the quantum Brachistochrone problem. We also explore some concrete physical applications and manifestations of the abstract concepts and tools that have been developed in the course of this investigation. These include applications in nuclear physics, condensed matter physics, relativistic quantum mechanics and quantum field theory, quantum cosmology, electromagnetic wave propagation, open quantum systems, magnetohydrodynamics, quantum chaos and biophysics.

scholarly journals Violation of unitarity in gravitational subregions

2021 ◽  
Author(s):  
Aron C. Wall
Keyword(s):  
Hilbert Space ◽  
Black Hole ◽  
Quantum Mechanics ◽  
Quantum Gravity ◽  
Path Integral ◽  
Cpt Symmetry ◽  
Negative Norm ◽  
Trapped Surfaces ◽  
Negative Probability

This essay contends that in quantum gravity, some spatial regions do not admit a unitary Hilbert space. Because the gravitational path integral spontaneously breaks CPT symmetry, “states” with negative probability can be identified on either side of trapped surfaces. I argue that these negative norm states are tolerable, by analogy to quantum mechanics. This viewpoint suggests a resolution of the firewall paradox, similar to black hole complementarity. Implications for cosmology are briefly discussed.

6. Frontiers of gravitational physics

2017 ◽  
pp. 83-97
Author(s):  
Timothy Clifton
Keyword(s):  
Quantum Mechanics ◽  
String Theory ◽  
Quantum Gravity ◽  
Cosmological Constant ◽  
Loop Quantum Gravity ◽  
Gravitational Interaction ◽  
Theoretical Description ◽  
Theoretical Physics ◽  
Cosmic Inflation ◽  
The World

‘Frontiers of gravitational physics’ considers some of the issues involved in the theoretical description of gravity. Since 1915, it has been Einstein’s theory that has shaped our understanding of the gravitational interaction, but a lot has happened in the world of theoretical physics since then. Quantum mechanics, devised by Bohr, Heisenberg, and Schrödinger, is incompatible with gravity and so has raised numerous questions. Several theories, including String Theory and Loop Quantum Gravity, have been proposed with some success. The concepts of cosmic inflation, the cosmological constant, and the possibility of multiple universes are also discussed. It concludes that with further astrophysical studies a new fundamental theory may explain it all.

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