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The Group Theory and Non-Euclidean Superposition Principle in Quantum Mechanics

V. Nicolay

Published Feb 24, 2012• 1 citation
Publisher

Abstract

One of the unsolved problem in theoretical physics during some decades remains a construction of the complete and closed theory in which quantum mechanics and special relativity would be consistent without divergences and renormalization (Dirac, 1978). It may be assumed that divergences show conservation laws violation in the conventional theories, and a cause for it may be in turn violation of the group-theoretic principles in these theories, in accordance with the Noether theorems. A success of renormalization allows one to believe that the theory without divergences is possible. This paper is devoted to consideration of possibility to develop the consistent group-theoretic scheme of the quantum mechanics merely. It consists of Introduction, three parts, and Conclusion. The requirements which allow one to consider the quantum mechanics as a consistent group-theoretic theory are formulated in Introduction. The Noether theorems set one-to-one correspondence between conservation laws of the variables to be measured, i.e. observables (Dirac, 1958), and groups of symmetries of the solutions transformations of equations for complex wave functions, spinors, matrices and so on in which the space-time properties appear (Olver, 1986). These solutions do not obey to be an observables but the last ones may be constructed as the Hermitian forms corresponding to these observables on their basis. The mathematical tool to express the space-time symmetry properties is the group theory. Two circumstances connected with the stated above attract attention in the generally accepted schemes of the quantum mechanics. The exact conservation laws fulfilment is inconceivable in any theoretical scheme under absence of the complete set of the Hermitian forms, based on the main equations solutions and its derivatives, each of them would be corresponded to the observables. Some of these Hermitian forms have to be conserved, another have to be changed but all of them have to satisfy to some completeness condition expressed mathematically. The last subject has exceptional significance since if only some part of the unknown complete set of observables really existing is included into the theory, then both physical interpretation and conservation laws would be dependent on the Hermitian forms which are excluded from the theory. Of course, such theory can not be recognized to be the consecutive, complete and closed theory. One of the impressive consequence of the observables complete set and corresponding completeness condition absence is the well known question on the hidden parameters 13

DOI
10.5772/34781

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Second-quantization and irreducible tensorial sets

Z. Rudzikas

General remarks As already mentioned in the Introduction, the exact solution of the main equation of quantum mechanics – the Schrödinger equation – lies beyond the potentialities of modern mathematics and computer technology. But a number of important inferences about the behaviour, structure and properties of a given quantum-mechanical many-particle system can be drawn without solving this equation, just by examining its symmetry properties. Symmetry concepts come about in physics in two ways. First, since any physical process occurs in a real space, we have to make use of one or another coordinate system. The isotropy and homogeneity of space make physically meaningful only those mathematical relationships that remain unchanged under rotations of the axes of the coordinate system, and that impose fairly rigorous constraints on the possible physical laws. Second, every physical object and process features a symmetry which should be taken into account by the physical theory. A common idea underlying particular forms of symmetry is the invariance of a system under a certain set (group) of transformations. The normally considered forms of symmetry are rotational symmetry, which is based on the equivalence of all directions in space, and permutation symmetry, which is caused by identical particles. The operations of the geometrical symmetry group are responsible for appropriate conservation laws. So, the rotational symmetry of a closed system gives rise to the law of conservation of angular momentum. The group of rotations of a three-dimensional space stands apart in atomic spectroscopy. This is mostly due to the high accuracy of the central field approximation, on which the entire modern theory of complex atoms and ions is based.

Cambridge University Press eBooks•Dec 4, 1997•0 citations

Quantum Mechanics Based on Non-Hermitian Hamiltonians (Recent Trends in Exponential Asymptotics)

Carl M. Bender

A physical theory of quantum mechanics can be based on a complex Hamiltonian that is not Hermitian but instead satisfies the physical condition of space-time reflection symmetry ( $P\mathcal{T}$ symmetry).Thus, there are infinitely many new Hamiltonians that one can construct that might explain experimental data.One would think that a non-Hermitian Hamiltonian would give a quantum theory that violates unitarity.However, if $P\mathcal{T}$ symmetry is not broken, it is possible to use a physical symmetry of the Hamiltonian to construct an inner product whose associated norm is positive definite.This construction is general and works for any $P\mathcal{T}$ -symmetric Hamiltonian.The dynamics is governed by unitary time evolution.This formulation does not conflict with the requirements of conventional quantum mechanics.There are many possible observable and experimental consequences of extending quantum mechanics into the complex domain, both in particle physics and in solid state physics.

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Relativistic Particle Theories Without Canonical Quantization

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The diffculties of relativistic particle theories formulated my means of canonical quantization, such as Klein-Gordon and Dirac theories, ultimately led theoretical physicists to turn on quantum field theory to model elementary particle physics. The aim of the present work is to pursue a method alternative to canonical quantization that avoids these dfficulties. In order to guarantee this result, the present approach is constrained to be developed deductively from physical principles. The physical principles assumed for a free particle consist of the symmetry properties of the particle with respect to the Poincaré group and of the transformation properties of the position observable, expressed by means of a suitably conceived notion of quantum transformation. In so doing, the effectiveness of group theoretical methods is exploited. Our work has pointed out the necessity of new classes of irreducible representations of the Poincaré group the theory can be based on. For spin 0 particle, four inequivalent theories are completely determined, that differ from Klein-Gordon theory for the physical interpretation but also for the mathematical structures. In particular, two of these theories requires irreducible representations in the new classes. The present lack of the explicit transformation properties of position with respect to boosts forbids the complete determination of non zero spin particle theories. A particular form of these transformation properties was in past adopted by Jordan and Mukunda. We check its consistency within the present approach; it is found that for spin 1/2 particles there is only one consistent theory; it is unitarily related to Dirac theory, but, once again, it requires the new classes of irreducible representations.

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Group theoretical methods in physics: Proceedings of the IX international colloquium, held at Cocoyoc, Mexico, June 23-27, 1980

Kurt Bernardo Wolf

Group theory of the Morse potential.- Four Euclidean conformal group approach to the multiphoton processes in the H-atom.- Landau theory, symmetry breaking and the chain criterion.- The configuration dN in cubic symmetry: A symmetry adapted weak field approach.- Group theory of the effective potential.- Bloch theorem for crystals with structural distortions.- Global symmetries of spin systems defined on abelian manifolds.- Phases and conjugacy classes.- The probability density in non relativistic quantum mechanics and the (extended) Galilei group.- Quaternionic quantum mechanics and Adler's chromostatics.- Coherent angular momentum states for the isotropic oscillator.- How to measure the canonical momentum p and operators p + f(q).- A uniqueness result for the segal quantization of a classical system with symmetries.- On the singular points of the matrix elements of the resolvent operator.- Limitations on quantum measuring processes.- Classical and quantum physics on phase space: The state spaces.- Quantum dynamical semigroups and complete positivity. 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•Jan 1, 1980•2 citations

Symmetry and physics

Michael El-Batanouny, F. Wooten

Introduction The application of group theory to study physical problems and their solutions provides a formal method for exploiting the simplifications made possible by the presence of symmetry. Often the symmetry that is readily apparent is the symmetry of the system/object of interest, such as the three-fold axial symmetry of an NH 3 molecule. The symmetry exploited in actual analysis is the symmetry of the Hamiltonian. When alluding to symmetry we usually include geometrical, time-reversal symmetry, and symmetry associated with the exchange of identical particles. Conservation laws of physics are rooted in the symmetries of the underlying space and time. The most common physical laws we are familiar with are actually manifestations of some universal symmetries. For example, the homogeneity and isotropy of space lead to the conservation of linear and angular momentum, respectively, while the homogeneity of time leads to the conservation of energy. Such laws have come to be known as universal conservation laws. As we will delineate in a later chapter, the relation between these classical symmetries and corresponding conserved quantities is beautifully cast in a theorem due to Emmy Noether. At the day-to-day working level of the physicist dealing with quantum mechanics, the application of symmetry restrictions leads to familiar results, such as selection rules and characteristic transformations of eigenfunctions when acted upon by symmetry operations that leave the Hamiltonian of the system invariant.

Cambridge University Press eBooks•Mar 13, 2008•0 citations

Introduction to 𝒫𝒯-symmetric quantum theory

Carl M. Bender

In most introductory courses on quantum mechanics one is taught that the Hamiltonian operator must be Hermitian in order that the energy levels be real and that the theory be unitary (probability conserving). To express the Hermiticity of a Hamiltonian, one writes H = H †, where the symbol † denotes the usual Dirac Hermitian conjugation; that is, transpose and complex conjugate. In the past few years it has been recognized that the requirement of Hermiticity, which is often stated as an axiom of quantum mechanics, may be replaced by the less mathematical and more physical requirement of space – time reflection symmetry (𝒫𝒯 symmetry) without losing any of the essential physical features of quantum mechanics. Theories defined by non-Hermitian 𝒫𝒯-symmetric Hamiltonians exhibit strange and unexpected properties at the classical as well as at the quantum level. This paper explains how the requirement of Hermiticity can be evaded and discusses the properties of some non-Hermitian 𝒫𝒯-symmetric quantum theories.

arXiv:quant-ph/0501052•Contemporary Physics•Jul 1, 2005•497 citations
One of the unsolved problem in theoretical physics during some decades remains a construction of the complete and closed theory in which quantum mechanics and special relativity would be consistent without divergences and renormalization (Dirac, 1978). It may be assumed that divergences show conservation laws violation in the conventional theories, and a cause for it may be in turn violation of the group-theoretic principles in these theories, in accordance with the Noether theorems. A success of renormalization allows one to believe that the theory without divergences is possible. This paper is devoted to consideration of possibility to develop the consistent group-theoretic scheme of the quantum mechanics merely. It consists of Introduction, three parts, and Conclusion. The requirements which allow one to consider the quantum mechanics as a consistent group-theoretic theory are formulated in Introduction. The Noether theorems set one-to-one correspondence between conservation laws of the variables to be measured, i.e. observables (Dirac, 1958), and groups of symmetries of the solutions transformations of equations for complex wave functions, spinors, matrices and so on in which the space-time properties appear (Olver, 1986). These solutions do not obey to be an observables but the last ones may be constructed as the Hermitian forms corresponding to these observables on their basis. The mathematical tool to express the space-time symmetry properties is the group theory. Two circumstances connected with the stated above attract attention in the generally accepted schemes of the quantum mechanics. The exact conservation laws fulfilment is inconceivable in any theoretical scheme under absence of the complete set of the Hermitian forms, based on the main equations solutions and its derivatives, each of them would be corresponded to the observables. Some of these Hermitian forms have to be conserved, another have to be changed but all of them have to satisfy to some completeness condition expressed mathematically. The last subject has exceptional significance since if only some part of the unknown complete set of observables really existing is included into the theory, then both physical interpretation and conservation laws would be dependent on the Hermitian forms which are excluded from the theory. Of course, such theory can not be recognized to be the consecutive, complete and closed theory. One of the impressive consequence of the observables complete set and corresponding completeness condition absence is the well known question on the hidden parameters 13
General remarks As already mentioned in the Introduction, the exact solution of the main equation of quantum mechanics – the Schrödinger equation – lies beyond the potentialities of modern mathematics and computer technology. But a number of important inferences about the behaviour, structure and properties of a given quantum-mechanical many-particle system can be drawn without solving this equation, just by examining its symmetry properties. Symmetry concepts come about in physics in two ways. First, since any physical process occurs in a real space, we have to make use of one or another coordinate system. The isotropy and homogeneity of space make physically meaningful only those mathematical relationships that remain unchanged under rotations of the axes of the coordinate system, and that impose fairly rigorous constraints on the possible physical laws. Second, every physical object and process features a symmetry which should be taken into account by the physical theory. A common idea underlying particular forms of symmetry is the invariance of a system under a certain set (group) of transformations. The normally considered forms of symmetry are rotational symmetry, which is based on the equivalence of all directions in space, and permutation symmetry, which is caused by identical particles. The operations of the geometrical symmetry group are responsible for appropriate conservation laws. So, the rotational symmetry of a closed system gives rise to the law of conservation of angular momentum. The group of rotations of a three-dimensional space stands apart in atomic spectroscopy. This is mostly due to the high accuracy of the central field approximation, on which the entire modern theory of complex atoms and ions is based.
A physical theory of quantum mechanics can be based on a complex Hamiltonian that is not Hermitian but instead satisfies the physical condition of space-time reflection symmetry ( PTP\mathcal{T}PT symmetry).Thus, there are infinitely many new Hamiltonians that one can construct that might explain experimental data.One would think that a non-Hermitian Hamiltonian would give a quantum theory that violates unitarity.However, if PTP\mathcal{T}PT symmetry is not broken, it is possible to use a physical symmetry of the Hamiltonian to construct an inner product whose associated norm is positive definite.This construction is general and works for any PTP\mathcal{T}PT -symmetric Hamiltonian.The dynamics is governed by unitary time evolution.This formulation does not conflict with the requirements of conventional quantum mechanics.There are many possible observable and experimental consequences of extending quantum mechanics into the complex domain, both in particle physics and in solid state physics.
The diffculties of relativistic particle theories formulated my means of canonical quantization, such as Klein-Gordon and Dirac theories, ultimately led theoretical physicists to turn on quantum field theory to model elementary particle physics. The aim of the present work is to pursue a method alternative to canonical quantization that avoids these dfficulties. In order to guarantee this result, the present approach is constrained to be developed deductively from physical principles. The physical principles assumed for a free particle consist of the symmetry properties of the particle with respect to the Poincaré group and of the transformation properties of the position observable, expressed by means of a suitably conceived notion of quantum transformation. In so doing, the effectiveness of group theoretical methods is exploited. Our work has pointed out the necessity of new classes of irreducible representations of the Poincaré group the theory can be based on. For spin 0 particle, four inequivalent theories are completely determined, that differ from Klein-Gordon theory for the physical interpretation but also for the mathematical structures. In particular, two of these theories requires irreducible representations in the new classes. The present lack of the explicit transformation properties of position with respect to boosts forbids the complete determination of non zero spin particle theories. A particular form of these transformation properties was in past adopted by Jordan and Mukunda. We check its consistency within the present approach; it is found that for spin 1/2 particles there is only one consistent theory; it is unitarily related to Dirac theory, but, once again, it requires the new classes of irreducible representations.
Group theory of the Morse potential.- Four Euclidean conformal group approach to the multiphoton processes in the H-atom.- Landau theory, symmetry breaking and the chain criterion.- The configuration dN in cubic symmetry: A symmetry adapted weak field approach.- Group theory of the effective potential.- Bloch theorem for crystals with structural distortions.- Global symmetries of spin systems defined on abelian manifolds.- Phases and conjugacy classes.- The probability density in non relativistic quantum mechanics and the (extended) Galilei group.- Quaternionic quantum mechanics and Adler's chromostatics.- Coherent angular momentum states for the isotropic oscillator.- How to measure the canonical momentum p and operators p + f(q).- A uniqueness result for the segal quantization of a classical system with symmetries.- On the singular points of the matrix elements of the resolvent operator.- Limitations on quantum measuring processes.- Classical and quantum physics on phase space: The state spaces.- Quantum dynamical semigroups and complete positivity. An application to isotropic spin relaxation.- On geometric quantization of the rigid body.- A unified theory of simple dynamical systems.- Geometry of the time-dependent variational principle in quantum mechanics.- Variational characterization of Hamiltonian vectorfields as lie algebra of canonical diffeomorphisms.- The lie theory of extended groups in classical mechanics - Is it of relevance to quantum mechanics?.- On the structure of phase space.- Quantization as mapping and as deformation.- Metric and group structures from quantum physics.- Spontaneous symmetry breaking and restricted superposition principle.- Many-body quantum mechanics as symplectic dynamics.- A nonlinear superposition principle for Riccati equations of the conformal type.- Backlund transformations, conservation laws and lie symmetries for the generalized nonlinear Schrodinger equation.- Killing tensors and variable separation for Hamilton-Jacobi equations.- Lie pseudogroups and gauge theory.- Conformal invariance and symmetry breaking for the one-dimensional wave equation.- The flavour sequence and superselection rules.- The Zitterbewegung of the electron and its compact phase space.- New experimental evidence for a new interpretation of flavor SU(3).- Baryon magnetic moments in broken SU(6).- The Racah-Wigner algebra and the masses of exotic hadrons.- Simple construction of a relativistic wave equation with arbitrary mass and spin and belinfante's 1/S-conjecture.- Poincare group, symplectic group, and relativistic extended hadrons consisting of spin 1/2 quarks.- An operator S matrix theory of the strongly interacting particles.- Generalized Galilei invariant partial wave expansions of the scattering amplitude for collisions between two particles with arbitrary spin.- Ternary algebras as the basis of a dynamical theory of subconstituents.- Solitons as sections in non trivial bundles.- Effects of heavy colored higgs scalars in grand unified theories.- Categories of nonlinear group realizations: A possible explanation for the multiple states of charge.- Classical solutions of non-linear ?-models and their quantum fluctuations.- Higgs representations for SO(n) gauges theories.- Multivortex configurations in the Abelian Higgs model.- Quark confinement in field theories with discrete gauge symmetry Z(3).- Proliferation of effective fields by spontaneous symmetry breakdown.- Explicit solutions for the scalar coupled Yang-Mills system in Minkowski space.- Dynamical supersymmetry SU(6/4) in nuclei.- Group theory of the IBA and its applications.- Bases for irreps of U(6) and three body problems.- Intrinsic sphape of nuclei.- Group theory and nuclear high spin phenomena.- SU3 symmetry in resonating group calculations. Toward a microscopic theory of 12C + 12C molecular resonances.- Collective motion, composite particle structure, and symplectic groups in nuclei.- Group theory and confrontation of nuclear collective models.- Matrix elements of generators of U(6) in a U(6)?U(3)?U(2) basis.- Hartree-Fock one-body dynamics and U(n) co-adjoint orbits.- Group-theoretical aspects of the many-body problem in nuclear theory.- The continuing quest for exact solutions of Einstein's field eouations - - new goals for the eighties.- All non-twisting N's with cosmological constant.- Can quantum effects prevent spacetime collapse?.- Complex plane representation of the Geroch group and a proof of a geroch conjecture.- The Geroch group and soliton solutions of the stationary axially symmetric Einstein's equations.- Geometry of projective asymptotic twistor space.- A truly relativistic approach of the concept of time.- Bases in Sp(2n) representation space.- Semiunitary projective representations of non-connected lie groups: A criterion for the choice of the unitary subgroup.- SU(mn) ? SU(m) x SU(n) isoscalar factors and S(f1+f2) ? S(f1) x S(f2) isoscalar factors.- Structure of enveloping algebras of low-rank groups.- Computer programs for the reduction of symmetrised nth powers of space group irreducible representations using gard's subgroup method.- Some remarks on the uniqueness and reality of Clebsch-Gordan coefficients for corepresentations.- On some special relations involving 3-jm symbols.- Two problems related to the Stone-von Neumann-Mackey uniqueness theorem.- Non-complex representations and their relation to antiunitary symmetry.- Representation theory of compact groups.- Representation theory of compact groups / Shift operators for discrete unitary representations of O(p,q).- Representation theory of compact groups / Maximal Abelian subalgebras of sp(2n,?) and their applications in physics.- Representation theory of compact groups / Polynomial space group tensors.- A permutation for SUn consistent with duality.- Integral transform representation of SL (2,R).- The theory of G? supermanifolds.- Casimir operations and the relations of the simplest supersymmetric superalgebra.- On realizations of graded lie algebras and on properties of d-polynomials.- On gauge formulations of gravitation theories.- Lagrangian formalism for superfields with internal symmetry.- Causal propagation in second order Lorentz-invariant wave equations.- The exceptional group E8 for grand unification.- Completely integrable N-body problems in three-dimension and their relativistic generalization.- Ward-Takashi identities as a necessary and sufficient condition for gauce invariance.- Supersymmetric generalization of Riemannian symmetric pairs.- Composite gauge fields and Riemannian geometry.- Gauge-theory ghosts and unitarity - Progress in the geometrical treatment.- Color in internal supersymmetry unification.- Canonical (possibly Lagrangian) realizations of the Poincare' group with increasing mass-spin trajectories.- Similarity analysis of wave propagation in axially nonlinear nonhomogeneous systems.
Introduction The application of group theory to study physical problems and their solutions provides a formal method for exploiting the simplifications made possible by the presence of symmetry. Often the symmetry that is readily apparent is the symmetry of the system/object of interest, such as the three-fold axial symmetry of an NH 3 molecule. The symmetry exploited in actual analysis is the symmetry of the Hamiltonian. When alluding to symmetry we usually include geometrical, time-reversal symmetry, and symmetry associated with the exchange of identical particles. Conservation laws of physics are rooted in the symmetries of the underlying space and time. The most common physical laws we are familiar with are actually manifestations of some universal symmetries. For example, the homogeneity and isotropy of space lead to the conservation of linear and angular momentum, respectively, while the homogeneity of time leads to the conservation of energy. Such laws have come to be known as universal conservation laws. As we will delineate in a later chapter, the relation between these classical symmetries and corresponding conserved quantities is beautifully cast in a theorem due to Emmy Noether. At the day-to-day working level of the physicist dealing with quantum mechanics, the application of symmetry restrictions leads to familiar results, such as selection rules and characteristic transformations of eigenfunctions when acted upon by symmetry operations that leave the Hamiltonian of the system invariant.
In most introductory courses on quantum mechanics one is taught that the Hamiltonian operator must be Hermitian in order that the energy levels be real and that the theory be unitary (probability conserving). To express the Hermiticity of a Hamiltonian, one writes H = H †, where the symbol † denotes the usual Dirac Hermitian conjugation; that is, transpose and complex conjugate. In the past few years it has been recognized that the requirement of Hermiticity, which is often stated as an axiom of quantum mechanics, may be replaced by the less mathematical and more physical requirement of space – time reflection symmetry (𝒫𝒯 symmetry) without losing any of the essential physical features of quantum mechanics. Theories defined by non-Hermitian 𝒫𝒯-symmetric Hamiltonians exhibit strange and unexpected properties at the classical as well as at the quantum level. This paper explains how the requirement of Hermiticity can be evaded and discusses the properties of some non-Hermitian 𝒫𝒯-symmetric quantum theories.