Quantum Mechanics

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Quantum Mechanics ◽  
Ground State ◽  
Variational Principles ◽  
Free Particle ◽  
Uncertainty Relations ◽  
Probabilistic Interpretation ◽  
Historical Account ◽  
Potential Wells ◽  
Harmonic Oscillator Potential ◽  
Ground State Energies

In this chapter, the main features of quantum theory are presented. The chapter begins with a historical account of the invention of quantum mechanics. The meaning of position and momentum in quantum mechanics is discussed and non-commuting operators are introduced. The Schrödinger equation is presented and solved for a free particle and for a harmonic oscillator potential in one dimension. The meaning of the wavefunction is considered and the probabilistic interpretation is presented. The mathematical machinery and language of quantum mechanics are developed, including Hermitian operators, observables and expectation values. The uncertainty principle is discussed and the uncertainty relations are presented. Scattering and tunnelling by potential wells and barriers is considered. The use of variational principles to estimate ground state energies is explained and illustrated with a simple example.

Calculation of energy eigenvalues via supersymmetric quantum mechanics

1989 ◽  
Vol 67 (10) ◽  
pp. 931-934 ◽  
Author(s):  
Francisco M. Fernández ◽  
Q. Ma ◽  
D. J. DeSmet ◽  
R. H. Tipping
Keyword(s):  
Quantum Mechanics ◽  
Ground State ◽  
Potential Energy Function ◽  
Supersymmetric Quantum Mechanics ◽  
Energy Eigenvalues ◽  
Arbitrary Power ◽  
Rational Function Approximation ◽  
Ricatti Equation ◽  
Original Potential ◽  
Ground State Energies

A systematic procedure using supersymmetric quantum mechanics is presented for calculating the energy eigenvalues of the Schrödinger equation. Starting from the Hamiltonian for a given potential-energy function, a sequence of supersymmetric partners is derived such that the ground-state energy of the kth one corresponds to the kth eigen energy of the original potential. Various theoretical procedures for obtaining ground-state energies, including a method involving a rational-function approximation for the solution of the Ricatti equation that is outlined in the present paper, can then be applied. Illustrative numerical results for two one-dimensional parity-invariant model potentials are given, and the results of the present procedure are compared with those obtainable via other methods. Generalizations of the method for arbitrary power-law potentials and for radial problems are discussed briefly.

NONLINEAR QUANTUM MECHANICS WITH NONCLASSICAL GRAVITATIONAL SELF-INTERACTION III: RELATED TOPICS

1993 ◽  
Vol 08 (16) ◽  
pp. 2709-2734 ◽  
Author(s):  
A. D. POPOVA ◽  
A. N. PETROV
Keyword(s):  
Quantum Mechanics ◽  
Gauge Invariance ◽  
Ricci Tensor ◽  
Variational Principles ◽  
Uncertainty Relations ◽  
Quantum Problem ◽  
General Quantum ◽  
Nonlinear Quantum ◽  
Nonlinear Quantum Mechanics ◽  
The One

Some problems are considered in the framework of general quantum mechanics with gravitational self-interaction constructed earlier. A number of them were analyzed for the stationary situation. Here, the problem of gauge invariance generated by translations which do not violate the 3 + 1 splitting is studied. The notions of position and momentum operators are extended to the general case. The uncertainty relations are obtained for the uncertainty of the Ricci tensor and for uncertainties of the position and momentum of a particle. The correspondence between the stationary and nonstationary cases is examined at the level of variational principles. At least, the one-particle and two-particle problems in the Newtonian–Schrödingerian limit are considered; the latter problem is compared with the standard two-particle quantum problem to demonstrate the advantage of our approach.

The Physical World

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Quantum Mechanics ◽  
Particle Physics ◽  
Variational Principles ◽  
Black Body ◽  
Black Body Radiation ◽  
Physical World ◽  
Atomic Scale ◽  
Solid State Physics ◽  
Least Action ◽  
Dimensional Spacetime

The book is an inspirational survey of fundamental physics, emphasizing the use of variational principles. Chapter 1 presents introductory ideas, including the principle of least action, vectors and partial differentiation. Chapter 2 covers Newtonian dynamics and the motion of mutually gravitating bodies. Chapter 3 is about electromagnetic fields as described by Maxwell’s equations. Chapter 4 is about special relativity, which unifies space and time into 4-dimensional spacetime. Chapter 5 introduces the mathematics of curved space, leading to Chapter 6 covering general relativity and its remarkable consequences, such as the existence of black holes. Chapters 7 and 8 present quantum mechanics, essential for understanding atomic-scale phenomena. Chapter 9 uses quantum mechanics to explain the fundamental principles of chemistry and solid state physics. Chapter 10 is about thermodynamics, which is built around the concepts of temperature and entropy. Various applications are discussed, including the analysis of black body radiation that led to the quantum revolution. Chapter 11 surveys the atomic nucleus, its properties and applications. Chapter 12 explores particle physics, the Standard Model and the Higgs mechanism, with a short introduction to quantum field theory. Chapter 13 is about the structure and evolution of stars and brings together material from many of the earlier chapters. Chapter 14 on cosmology describes the structure and evolution of the universe as a whole. Finally, Chapter 15 discusses remaining problems at the frontiers of physics, such as the interpretation of quantum mechanics, and the ultimate nature of particles. Some speculative ideas are explored, such as supersymmetry, solitons and string theory.

scholarly journals Fast Vacuum Fluctuations and the Emergence of Quantum Mechanics

2021 ◽  
Vol 51 (3) ◽  
Author(s):  
Gerard ’t Hooft
Keyword(s):  
Quantum Mechanics ◽  
Ground State ◽  
Quantum Interference ◽  
Direct Detection ◽  
Energy Levels ◽  
Vacuum Fluctuations ◽  
Heavy Particles ◽  
Evolving Systems ◽  
Gedanken Experiment ◽  
Classical Computer

AbstractFast moving classical variables can generate quantum mechanical behavior. We demonstrate how this can happen in a model. The key point is that in classically (ontologically) evolving systems one can still define a conserved quantum energy. For the fast variables, the energy levels are far separated, such that one may assume these variables to stay in their ground state. This forces them to be entangled, so that, consequently, the slow variables are entangled as well. The fast variables could be the vacuum fluctuations caused by unknown super heavy particles. The emerging quantum effects in the light particles are expressed by a Hamiltonian that can have almost any form. The entire system is ontological, and yet allows one to generate interference effects in computer models. This seemed to lead to an inexplicable paradox, which is now resolved: exactly what happens in our models if we run a quantum interference experiment in a classical computer is explained. The restriction that very fast variables stay predominantly in their ground state appears to be due to smearing of the physical states in the time direction, preventing their direct detection. Discussions are added of the emergence of quantum mechanics, and the ontology of an EPR/Bell Gedanken experiment.

TABLE OF GROUND STATE PROPERTIES OF NUCLEI IN THE RMF MODEL

2013 ◽  
Vol 28 (16) ◽  
pp. 1350068 ◽  
Author(s):  
TUNCAY BAYRAM ◽  
A. HAKAN YILMAZ
Keyword(s):  
Ground State ◽  
Mean Field ◽  
Properties Of Nuclei ◽  
Relativistic Mean Field ◽  
Ground State Properties ◽  
Pairing Correlations ◽  
Ground State Energies ◽  
Rmf Model

The ground state energies, sizes and deformations of 1897 even–even nuclei with 10≤Z ≤110 have been carried out by using the Relativistic Mean Field (RMF) model. In the present calculations, the nonlinear RMF force NL3* recent refitted version of the NL3 force has been used. The BCS (Bardeen–Cooper–Schrieffer) formalism with constant gap approximation has been taken into account for pairing correlations. The predictions of RMF model for the ground state properties of some nuclei have been discussed in detail.

Application of multireference linearized coupled-cluster theory to atomic and molecular systems

2018 ◽  
Vol 17 (02) ◽  
pp. 1850016 ◽  
Author(s):  
Jiang Yi ◽  
Feiwu Chen
Keyword(s):  
Ground State ◽  
Basis Sets ◽  
Coupled Cluster ◽  
Vibration Frequencies ◽  
Electron Affinities ◽  
Proton Affinities ◽  
Coupled Cluster Theory ◽  
Molecular Systems ◽  
Ground State Energies ◽  
Second Order Perturbation Theory

Applications of the multireference linearized coupled-cluster single-doubles (MRLCCSD) to atomic and molecular systems have been carried out. MRLCCSD is exploited to calculate the ground-state energies of HF, H2O, NH3, CH4, N2, BF, and C2with basis sets, cc-pVDZ, cc-pVTZ and cc-pVQZ. The equilibrium bond lengths and vibration frequencies of HF, HCl, Li2, LiH, LiF, LiBr, BH, and AlF are computed with MRLCCSD and compared with the experimental data. The electron affinities of F and CH as well as the proton affinities of H2O and NH3are also calculated with MRLCCSD. These results are compared with the results produced with second-order perturbation theory, linearized coupled-cluster doubles (LCCD), coupled-cluster doubles (CCD), coupled-cluster singles and doubles (CCSD), CCSD with perturbative triples correction (CCSD(T)). It is shown that all results obtained with MRLCCSD are reliable and accurate.

Sign in / Sign up

Export Citation Format

Share Document