8. Quantum mechanics

2019 ◽  
pp. 99-110
Author(s):  
Eric R. Scerri
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Boundary Conditions ◽  
Spherical Shell ◽  
Electron Energy ◽  
Energy Levels ◽  
Single Electron ◽  
Electron Systems ◽  
New Developments

‘Quantum mechanics’ shows how Bohr’s quantum theory was a stepping stone for the development of quantum mechanics. Bohr’s quantum theory worked well in single electron systems, but not in multi-electron systems. Quantum mechanics allowed the development of Schrödinger’s equation, which could theoretically predict the determination of electron energy levels in any system. The advantage of quantum mechanics over quantum theory lies in its treatment of electrons as waves. This allowed Schrödinger to apply mathematical boundary conditions to his equation and quantize the energy levels of electrons. Further work by Heisenberg showed that electrons are spread around a spherical shell. New developments on atomic configurations by Eugen Schwarz are also discussed.

Anthropic Contingency

2020 ◽  
pp. 185-197
Author(s):  
Alastair Wilson
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Cosmological Parameters ◽  
Selection Effect ◽  
Fine Tuning ◽  
Interpretation Of Quantum Mechanics ◽  
Correct Interpretation ◽  
The One ◽  
Observation Selection

Distinguish contingency in general from anthropic contingency. The former is what really could happen; the latter is what really could be observed to happen. Quantum histories which host no life cannot, as a matter of obvious necessity, be observed. This distinction generates an anthropic observation selection effect, which has been employed in response to the fine-tuning argument for the design hypothesis. This chapter argues that fine-tuning is a genuine phenomenon that cries out for explanation; that in one-world approaches to quantum theory a chancy determination of cosmological parameters would render the one universe we are in preposterously lucky; that no preposterous luck is required from the perspective of quantum modal realism; and that the correct interpretation of quantum mechanics turns out to have a significant evidential bearing on the design question.

scholarly journals Irreversibility in quantum mechanics

2004 ◽  
Vol 2004 (1) ◽  
pp. 75-83 ◽  
Author(s):  
R. C. Bishop ◽  
A. Bohm ◽  
M. Gadella
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Boundary Conditions ◽  
Liouville Equation ◽  
Quantum Systems ◽  
Arrow Of Time ◽  
Time Asymmetry ◽  
Classical Physics ◽  
Von Neumann ◽  
Signal Features

Time asymmetry and irreversibility are signal features of our world. They are the reason of our aging and the basis for our belief that effects are preceded by causes. These features have many manifestations called arrows of time. In classical physics, some of these arrows are described by the increase of entropy or probability, and others by time-asymmetric boundary conditions of time-symmetric equations (e.g., Maxwell or Einstein). However, there is some controversy over whether probability or boundary conditions are more fundamental. For quantum systems, entropy increase is usually associated with the effects of an environment or measurement apparatus on a quantum system and is described by the von Neumann-Liouville equation. But since the traditional (von Neumann) axioms of quantum mechanics do not allow time-asymmetric boundary conditions for the dynamical differential equations (Schrödinger or Heisenberg), there is no quantum analogue of the radiation arrow of time. In this paper, we review consequences of a modification of a fundamental axiom of quantum mechanics. The new quantum theory is time asymmetric and accommodates an irreversible time evolution of isolated quantum systems.

NEW DEVELOPMENTS IN THE STUDY OFTIMEAS A QUANTUM OBSERVABLE

2008 ◽  
Vol 22 (12) ◽  
pp. 1877-1897 ◽  
Author(s):  
V. S. OLKHOVSKY ◽  
E. RECAMI
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Quantum Electrodynamics ◽  
Selfadjoint Operator ◽  
Relativistic Quantum ◽  
Relativistic Quantum Mechanics ◽  
New Developments ◽  
Quantum Observable ◽  
Time In Quantum Mechanics

Some results are briefly reviewed and developments are presented on the study of Time in quantum mechanics as an observable, canonically conjugate to energy. Operators for the observable Time are investigated in particle and photon quantum theory. In particular, this paper deals with the hermitian (more precisely, maximal hermitian, but non-selfadjoint) operator for Time which appears: (i) for particles, in ordinary non-relativistic quantum mechanics; and (ii) for photons (i.e., in first-quantization quantum electrodynamics).

scholarly journals Elliptical orbits in the phase-space quantization

2016 ◽  
Vol 38 (3) ◽  
Author(s):  
Leonardo Andreta de Castro ◽  
Carlos Alexandre Brasil ◽  
Reginaldo de Jesus Napolitano
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Phase Space ◽  
Energy Levels ◽  
Radial Component ◽  
Original Method ◽  
Direct Integration ◽  
Old Quantum Theory ◽  
Complex Integration ◽  
Elliptical Orbits

The energy levels of hydrogen-like atoms are obtained from the phase-space quantization, one of the pillars of the old quantum theory, by three different methods - (i) direct integration, (ii) Sommerfeld's original method, and (iii) complex integration. The difficulties come from the imposition of elliptical orbits to the electron, resulting in a variable radial component of the linear momentum. Details of the calculation, which constitute a recurrent gap in textbooks that deal with phase-space quantization, are shown in depth in an accessible fashion for students of introductory quantum mechanics courses.

scholarly journals DETERMINATION OF BOUNDARY CONDITIONS FOR THE RADIATION PATTERN OF A MICROELECTRO-OPTICAL INTELLIGENT PASSIVE INFRARED MOTION DETECTOR

2021 ◽  
Vol 3 (1) ◽  
pp. 31-36
Author(s):  
Ruslan Holovatskyy ◽  
◽  
Mykhaylo Lobur ◽  
Keyword(s):  
Boundary Conditions ◽  
Computer Aided Design ◽  
Block Diagram ◽  
Primary Sources ◽  
Motion Detector ◽  
New Developments ◽  
Aided Design ◽  
Motion Detectors ◽  
Passive Infrared

In this paper, a block diagram of a microelectro-optical intelligent passive infrared motion detector is proposed. On the basis of the proposed structural scheme and analytically conducted synthetic processing of information from primary sources [5-17], boundary conditions for the directivity diagram of such a detector are determined. The analytical information collected in this article will be necessary for further modeling in computer-aided design with a view to new developments and improvements to existing motion detectors.

New developments in the ab initio determination of transition metal alloys phase diagram

1993 ◽  
Vol 90 ◽  
pp. 249-254 ◽  
Author(s):  
C Wolverton ◽  
M Asta ◽  
S Ouannasser ◽  
H Dreyssé ◽  
D de Fontaine
Keyword(s):  
Phase Diagram ◽  
Transition Metal ◽  
Ab Initio ◽  
Metal Alloys ◽  
New Developments ◽  
Transition Metal Alloys

On-the-Fly Determination of Active Region Centers in Adaptive-Partitioning QM/MM

2020 ◽  
Author(s):  
Zenghui Yang
Keyword(s):  
Quantum Mechanics ◽  
Active Region ◽  
Molecular Mechanics ◽  
Active Regions ◽  
Available Energy ◽  
Adaptive Partitioning ◽  
Different Levels

Quantum mechanics/molecular mechanics (QM/MM) methods partition the system into active and environmental regions and treat them with different levels of theory, achieving accuracy and efficiency at the same time. Adaptive-partitioning (AP) QM/MM methods allow on-the-fly changes to the QM/MM partitioning of the system. Many of the available energy-based AP-QM/MM methods partition the system according to distances to pre-chosen centers of active regions. For such AP-QM/MM methods, I develop an adaptive-center (AC) method that allows on-the-fly determination of the centers of active regions according to general geometrical or potential-related criteria, extending the range of application of energy-based AP-QM/MM methods to systems where active regions may occur or vanish during the simulation.

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