Bogolyubov transformations for regular representations of canonical commutation relations in space with an indefinite metric

Bogolyubov transformations for regular representations of the algebra of canonical commutation relations (CCRs) are considered in space with an indefinite metric.     

On representations of the canonical commutation relations

In the measure space construction of a representation of the canonical commutation relations, the strong continuity of any one parameter subgroup is proved.All multipliers for the separable case are expressed in a constructive manner and an irreducibility criterion for a subset of multipliers is obtained.Preprint No. 1970-27.On leave from Research Institute for Mathematical Sciences Kyoto University, Kyoto, Japan.     

Particle representations of canonical commutation relations

The aim of the present paper is to find a necessary and sufficient condition for the existence of the operator of the total number of particles in a representation of canonical commutation relations. The result is formulated by means of generating functionals of representations. It is shown that an irreducible representation possesses a (generalized) number operator if and only if the representation obtained by averaging its generating functional over the group of phase transformations is a factor representation of type I.     

Exponential representations of the canonical commutation relations

A class of representations of the canonical commutation relations is investigated. These representations, which are called exponential representations, are given by explicit formulas. Exponential representations are thus comparable to tensor product representations in that one may compute useful criteria concerning various properties. In particular, they are all locally Fock, and non-trivial exponential representations are globally disjoint from the Fock representation. Also, a sufficient condition is obtained for two exponential representations not to be disjoint. An example is furnished by Glimm's model for the :⁴: interaction for boson fields in three space-time dimensions.     

On factor representations and theC*-algebra of canonical commutation relations

A newC*-algebra,A, for canonical commutation relations, both in the case of finite and infinite number of degrees of freedom, is defined. It has the property that to each, not necessarily continuous, representation of CCR there corresponds a representation ofA. The definition ofA is based on the existence and uniqueness of the factor type II₁ representation. Some continuity properties of separable factor representations are proved.     

Functional representations of the canonical anticommutation relations and their application in quantum field theory

We construct functional Fock representations of the CAR algebra. The S-operator quantum theory of interacting Fermi fields is formulated. It is found that the functional version of this theory does not require the use of functionals taking values from a Grassmann algebra. All functionals used are C-valued quantities.     

Number operators for representations of the canonical commutation relations

Anumber operator for a representation of the canonical commutation relations is defined as a self-adjoint operator satisfying an exponentiated form of the equationNa*=a*(N+I), wherea* is an arbitrary creation operator. WhenN exists it may be chosen to have spectrum {0, 1, 2, ...} (in a direct sum of Fock representations) or {0, ±1, ±2, ...} (otherwise). Examples are given of representations having number operators, and a necessary and sufficient condition is given for a direct-product representation to have a number operator.     

Topologies induced by representations of the canonical commutation relations

This paper is concerned with continuity properties of representations of the canonical commutation relations, and is mainly devoted to a detailed discussion of the topologies induced on the test function spaces. The notion of closability of a representation of the canonical commutation relations is introduced and studied. We also discuss the strong continuity of functions of self-adjoint operators, and use bounded functions to define an analogue of the strong operator topology on the set of all self-adjoint operators.     

Current commutation relations in the framework of general quantum field theory

In this paper we give a rigorous formulation of Gell-Mann's equal time commutation relations in the framework of general quantum field theory. We show that this can be achieved despite the nonexistence of charge operators for nonconserved currents. Starting from the properly formulated equal time commutation relations of generalized charges, we justify the application of the Gauss-Theorem and we discuss the limits for large times of time dependent generalized charges. The Jost-Lehmann-Dyson representation is used in order to show that the equal time commutation relations always lead to exactly one, frame independent, sum rule. We discuss the connection between properties of the Jost-Lehmann-Dyson spectral function and the convergence of Adler-Weisberger type sum rules.On leave of absence from University of Pittsburgh, Pittsburgh 13 Penna.     

Continuity properties of the representations of the canonical commutation relations

We prove that a given representation of the canonical commutation relations can be extended uniquely by continuity to larger test function spaces which are maximal in the sense that no further extension is possible. For irreducible tensor product representations of the canonical commutation relations we give a necessary and a sufficient condition for the admissible test functions. We consider the problem of finding topologies on the test function spaces such that this extension can be obtained by a topological completion. Various examples are discussed.Supported in part by the National Research Council of Canada.An earlier version of the present work was distributed as a preprint entitled Topologies for Test Function Spaces for Representations of the Canonical Commutation Relations.     

Time-energy uncertainty and relativistic canonical commutation relations in quantum spacetime

It is shown that the time operatorQ ⁰ appearing in the realization of the RCCR's [Q,P^v]=–jhg^v, on Minkowski quantum spacetime is a self adjoint operator on Hilbert space of square integrable functions over _m =×v _m , where is a timelike hyperplane. This result leads to time-energy uncertainty relations that match their space-momentum counterparts. The operators Q appearing in Born's metric operator in quantum spacetime emerge as internal spacetime operators for exciton states, and the condition that the metric operator should possess a ground exciton state assumes the significance of achieving minimal spacetime4-momentum uncertainty in fundamental standards for spacetime measurements.Supported in part by NSERC research grant No. A5206.     

Test function spaces for direct product representations of the canonical commutation relations

It is shown how the test function spaces for the field operator and its canonical conjugate are determined by a given irreducible direct product representation of the canonical commutation relations. An explicit characterization of the admissible test functions (so that the smeared out field operators are selfadjoint) is given in terms of any one product state of the representation space.     

A note on product measures and representations of the canonical commutation relations

There is a well-known theorem which states that a non-zero -finite left quasi-invariant measure on a -compact locally compact groupG must be equivalent to left Haar measure. It is shown in this paper that there is a natural generalization of this fact to the case in which the groupG is replaced by a product space, one factor of which is a group. With the aid of this generalization, an easy proof of the following fact, due to H. Araki, is given: the representations of the canonical commutation relations constructed in the usual measure-theoretic manner are ray continuous.     

Deformations of the canonical commutation relations

Deformations of the canonical commutation relations which have the effect of altering the spectrum of a standard Hamiltonian, bilinear in creation and annihilation operators are described. The problem of going over from an eigenvalue situation, as is the case in the vast majority of papers in the literature, to a theory with time evolution is discussed, and a special example with deformation parameter an Nth root of unity is constructed which possesses a consistent time evolution. This work is an account of some recent studies of associative deformations of the Heisenberg algebra of several creation and annihilation algebras, with Jean Nuyts of the University of Mons, Hainaut, together with some observations of my own concerning the difficulty of implementing time evolution in a quantum group context. It builds on earlier work with Cosmas Zachos (Argonne National Laboratory, USA), which in turn is re;ated to work of Manin, and Wess, Zumino and collaborators. The main idea is that, if quantum groups have any role in physics, then they must manifest themselves at the level of the basic rules of quantisation.     

Extension of Tomita-Takesaki theory to the unbounded algebra of the canonical commutation relations

We consider the unbounded CCR algebra in infinitely many degrees of freedom equipped with a suitable faithful state. We prove that this state satisfies the KMS condition with respect to a certain time evolution and the associated unbounded GNS representation π_β has the structure encountered in Tomita-Takesaki theory; what is more, the commutant π_β$\text{U}$′ is a standard von Neumann algebra, invariant under the time evolution.     

A theorem on canonical commutation and anticommutation relations

The aim of this note is to characterize representations of the canonical commutation or anticommutation relations which, on a subspace of the space of test-functions, reduce to a sum of copies of the Fock representation.     

An algebraic approach to quantum field theory and commutation relations for energy momentum in the framework of general relativity

We present a consistent set of commutation relations (C.R.) for a quantum system immersed in a classical gravitational field. The gravity field is described by metric tensorg _ik (x) andg ₀₀(x) with coordinate gaugeg _i0=0. The Hamiltonian of the system is found to be a linear function of [–g ₀₀(x)]^1/2. Its properties we define by C.R. avoiding explicit expression in terms of fields, as well as its splitting into free and interaction parts. In this way a consistent set of C.R., which are equally simple for a flat and curvilinear space, can be established. To stress the main idea of our approach, we consider the simple but still nontrivial example of a scalar electrodynamics immersed in a gravity field. The electromagnetic current operator we define by its C.R. and not explicitly. An interesting feature of this approach is that the Poisson equation follows from the consistency of the C.R. The C.R. for the energy and momentum operators of the system in a gravity field are established which generalize the usual Poincare group generators C.R. For example, we find (i/hc ²)[H _(x) ,H _(x) ]=P _– , whereH _(x) is the Hamiltonian of the system, which is a linear functional of (x)[–g ₀₀(x)]^1/2 andP _s(x) represents the momentum-density operator [averaged with the classical functions(x)].     

On equal-time commutation relations of renormalized currents in perturbation theory I

Equal-time current commutation relations are considered in renormalizable field theories. Renormalized currents are obtained by means of solutions of the Yang-Feldman equations for Heisenberg field operators in perturbation theory. For the computation of matrix elements of current commutators we apply Jost-Lehmann-Dyson type techniques. The equal time limit is taken with the help of symmetrical time-smearing functions which interpolate the -function. Our methods avoid any cut-off procedure and lead therefore to unambiguous results. In order to avoid spin complications, our general methods are applied to trilinear resp. quadrilinear couplings of isoscalar and isovector spin 0-mesons in first order perturbation theory. We find that the zero-space components of the current-commutator matrix elements behave for small time separationT like ln(T) grad _x (X–Y).Supported by the U. S. Atomic Energy Commission under Contract AT(30-I)-3829.     

On associative commutation relations

Conditions that follow from the associativity of the algebras of deformed commutation relations are discussed. Possible commutation relations for one pair of creation and annihilation operators are presented.Presented at the Colloquium on the Quantum Groups, Prague, 18–20 June, 1992.