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数理解析研究所講究録

The Hot Free Algebra(Recent Trends in Infinite Dimensional Non-Commutative Analysis)

Luigi Accardi, Sergei Vladimirovich Kozyrev, Igor Vasil'evich Volovich

Published Apr 1, 1998• 0 citations
OpenAlex

Abstract

We consider the stochastic limit of the standard non relativistic QED (but our results also hold for the polaron interaction of a particle with a Boson field).Extending the Fock case results of $[\mathrm{A}\mathrm{c}\mathrm{L}\mathrm{u}92]$ , we take the initial state of the field to be a Gibbs state at a given temperature.We show that a new algebra, with commutation relations depending on the temperature and acting on a Hilbert module, emerges.This algebra, that we call the Hot Ree Algebra, generalizes the QED Hilbert module algebra in the sense of $[\mathrm{A}\mathrm{c}\mathrm{L}\mathrm{u}\mathrm{v}_{0}97\mathrm{C}]$ and [Ske96] and therefore also the Ree (or Boltzmannian) algebra.It is interesting to notice that, when the module structure is neglected, the algebra we find is precisely the algebra that was found in the singleton independence central limit theorem of $[\mathrm{A}\mathrm{h}_{0}98\mathrm{a}],$ $[\mathrm{A}\mathrm{h}_{0}98\mathrm{b}]$ .So the present result also gives a natural physical interpretation for that algebra.

Related papers

Dynamicalq-deformation in quantum theory and the stochastic limit

Luigi Accardi, Sergei Vladimirovich Kozyrev, Igor Vasil'evich Volovich

We show that in a model of a particle interacting with a quantum field, the field operators rescaled according to the prescriptions of the stochastic limit, obey q -commutational relations with q depending on time. After the stochastic limit, due to the nonlinearity, the particle and field degrees of freedom become entangled even at a kinematical level in the sense that the field and the atomic variables no longer commute but give rise to a new algebra with new commutation relations replacing the boson ones. This allows to give a simple proof of the fact that the non-crossing half-planar diagrams give the dominating contribution in a weak-coupling regime and to calculate explicitly the correlations associated with the new algebra.

arXiv:math/9807137•Journal of Physics A Mathematical and General•Jan 1, 1999•17 citations

Quantum Probability and Applications IV: Proceedings of the Year of Quantum Probability, Held at the University of Rome Ii, Italy, 1987

Luigi Accardi, Wilhelm von Waldenfels

Cecchini's transition expectations and markov chains.- Central limits of squeezing operators.- On the weak coupling limit problem.- On multi-dimensional markovian cocycles.- Quantum stop times.- Quantum random walks.- Unitary dilation of a nonlinear quantum boltzmann equation.- On isometries of non associative Lp-spaces.- Convolution semigroups in quantum probability and quantum stochastic calculus.- Stochastic couplings for von neumann algebras.- The covering property in a causal logic.- Temperature states of spin-boson models.- Bernoulli fields.- The relations of the non-commutative coefficient algebra of the unitary group.- Orthogonal series and strong laws of large numbers in von neumann algebras.- Limit theorems for repeated measurements and continuous measurement processes.- Quantum diffusions on the algebra of all bounded operators on a hilbert space.- Asymptotic formula for normal operators in non-commutative L2-spaces.- Convergences in W*-algebras - Their strange behaviour and tools for their investigation.- Positive mappings on matrix algebras.- Fluctuations of the dicke maser.- Tangent bimodule and locality for dissipative operators on C*-algebras.- Noncommutative stochastic processes with independent and stationary additive increments.- The atom in the radiation field as a quantum stochastic process.

•Oct 1, 1989•0 citations

Interacting Quantum Field Theory at Positive Temperature: States and Properties

Stefano Galanda

In this thesis interacting relativistic and non relativistic Quantum Field Theories (QFT) are studied, investigating their equilibrium configurations and their long time evolution in the framework of perturbative Algebraic Quantum Field Theory, studying also convergence in a specific model. In the first part, concerning the relativistic case, we study, in formal perturbation theory, interacting KMS states generalising results by Fredenhagen and Lindner to fermionic field theories. As an application their stability is investigated together with the characterisation of the Debye screening effect in plasmas via the explicit solution of the Semiclassical Maxwell equations. Connected to these results, we also initiate a systematic study of secular growths appearing in the truncated perturbative series and affecting the validity of perturbation theory in its long time predicting capability. We restrict to theories on Minkowski spacetime and provide, for interactions depending on time via a switching process, a sufficient condition preventing secular growths in the truncated perturbative series. In the second part, we focus on a model of non relativistic quantum field theory. We construct equilibrium states at positive temperature in the presence of a condensation phase for a gas of non relativistic Bose particles on an infinite space interacting through a localised two body interaction. The convergence is proven, both for the interacting KMS state and for the entropy of the interacting KMS state relative to the free KMS state. The strategy of our proof combines ideas of Algebraic QFT, Constructive QFT and methods of statistical mechanics in the operator algebraic setting. Limits where the localisation of the two-body interaction is removed are eventually discussed, in combination with limits of the other physical parameters of the theory such as temperature, strength of the interaction and chemical potential. Finally, in the appendix, we present results on the Araki-Uhlmann relative entropy in fermionic quantum field theories, as well as an entropy-area relation, obtained via semiclassical methods, for the cosmological horizon in the static patch of de Sitter spacetime sourced by a coherent excitation of a free quantum scalar field. This completes the collection of original results obtained during the PhD.

•Dec 18, 2025•0 citations

On Classical Aspects of Bose–Einstein Condensation

Lorenzo Pettinari

Abstract Berezin and Weyl quantization are renowned procedures for mapping commutative Poisson algebras of observables to their non-commutative, quantum counterparts. The latter is famous for its use on Weyl algebras, while the former is more appropriate for continuous functions decaying at infinity. In this work, we define a variant of the Berezin quantization map, which acts on the classical Weyl algebra $$\mathcal {W}(E,0)$$ W ( E , 0 ) and constitutes a positive strict deformation quantization . This construction provides a natural framework to compare classical and quantum thermal equilibrium states of a Bose gas through the computation of their semi-classical limit. To this end, we first introduce a purely algebraic notion of KMS states for the classical Weyl algebra and establish that, in finite volume, there exists a unique such state, which can be interpreted as the Fourier transform of a Gibbs measure on a Hilbert space. We then construct a new class of classical KMS states that realize representations of the canonical commutation relations with infinite local density. These states arise as the semi-classical high-density limit of the quantum equilibrium states originally studied by Araki and Woods [5]. A key feature of our approach is that it preserves the macroscopic ground-state occupation of the Bose gas in the classical regime. Finally, we demonstrate that the infinite-volume classical states can be obtained as thermodynamic limits of finite-volume Gibbs states.

arXiv:2411.02626•Annales Henri Poincaré•Oct 30, 2025•2 citations

Quantization as a Universal Probabilistic Phenomenon

L. Accardi, Yu. G. Lu

We survey some results obtained in the last 25 years to illustrate the following probabilistic quantization statement: quantum probability is not a generalization of classical probability but a deeper level of it. Generalizing the classical theory of orthogonal polynomials, one can show that any random field $X$ admitting all the moments can be represented as the sum of three operators, which are natural extensions of the creation, annihilation, and preservation operators in the usual boson Fock quantum theory. These operators generate a noncommutative $*$-algebra on which the quantum extension of the expected value relative to the probability distribution of the field $X$ induces a quantum state. So, any classical algebraic probability space generates a quantum space with its own commutation relations. The Heisenberg commutation relation characterizes the classical fields, while the new type of commutation relations (of type II) appears in non-Gaussian cases. The same machinery, but applied to Bernoulli fields, leads to Fermi--Dirac anticommutation relations (see the introduction).

Theory of Probability and Its Applications•Feb 1, 2026•0 citations

Quantization as a universal probabilistic phenomenon

Luigi Accardi, Yun Gang Lu

We survey some results obtained in the last 25 years to illustrate the following probabilistic quantization statement: quantum probability is not a generalization of classical probability but a deeper level of it. Generalizing the classical theory of orthogonal polynomials, one can show that any random field $X$ admitting all the moments can be represented as the sum of three operators, which are natural extensions of the creation, annihilation, and preservation operators in the usual boson Fock quantum theory. These operators generate a noncommutative $*$-algebra on which the quantum extension of the expected value relative to the probability distribution of the field $X$ induces a quantum state. So, any classical algebraic probability space generates a quantum space with its own commutation relations. The Heisenberg commutation relation characterizes the classical fields, while the new type of commutation relations (of type II) appears in non-Gaussian cases. The same machinery, but applied to Bernoulli fields, leads to Fermi-Dirac anticommutation relations (see the introduction).

Теория вероятностей и ее применения•Jan 1, 2025•0 citations
We consider the stochastic limit of the standard non relativistic QED (but our results also hold for the polaron interaction of a particle with a Boson field).Extending the Fock case results of [AcLu92][\mathrm{A}\mathrm{c}\mathrm{L}\mathrm{u}92][AcLu92] , we take the initial state of the field to be a Gibbs state at a given temperature.We show that a new algebra, with commutation relations depending on the temperature and acting on a Hilbert module, emerges.This algebra, that we call the Hot Ree Algebra, generalizes the QED Hilbert module algebra in the sense of [AcLuv097C][\mathrm{A}\mathrm{c}\mathrm{L}\mathrm{u}\mathrm{v}_{0}97\mathrm{C}][AcLuv0​97C] and [Ske96] and therefore also the Ree (or Boltzmannian) algebra.It is interesting to notice that, when the module structure is neglected, the algebra we find is precisely the algebra that was found in the singleton independence central limit theorem of [Ah098a],[\mathrm{A}\mathrm{h}_{0}98\mathrm{a}],[Ah0​98a], [Ah098b][\mathrm{A}\mathrm{h}_{0}98\mathrm{b}][Ah0​98b] .So the present result also gives a natural physical interpretation for that algebra.
We show that in a model of a particle interacting with a quantum field, the field operators rescaled according to the prescriptions of the stochastic limit, obey q -commutational relations with q depending on time. After the stochastic limit, due to the nonlinearity, the particle and field degrees of freedom become entangled even at a kinematical level in the sense that the field and the atomic variables no longer commute but give rise to a new algebra with new commutation relations replacing the boson ones. This allows to give a simple proof of the fact that the non-crossing half-planar diagrams give the dominating contribution in a weak-coupling regime and to calculate explicitly the correlations associated with the new algebra.
Cecchini's transition expectations and markov chains.- Central limits of squeezing operators.- On the weak coupling limit problem.- On multi-dimensional markovian cocycles.- Quantum stop times.- Quantum random walks.- Unitary dilation of a nonlinear quantum boltzmann equation.- On isometries of non associative Lp-spaces.- Convolution semigroups in quantum probability and quantum stochastic calculus.- Stochastic couplings for von neumann algebras.- The covering property in a causal logic.- Temperature states of spin-boson models.- Bernoulli fields.- The relations of the non-commutative coefficient algebra of the unitary group.- Orthogonal series and strong laws of large numbers in von neumann algebras.- Limit theorems for repeated measurements and continuous measurement processes.- Quantum diffusions on the algebra of all bounded operators on a hilbert space.- Asymptotic formula for normal operators in non-commutative L2-spaces.- Convergences in W*-algebras - Their strange behaviour and tools for their investigation.- Positive mappings on matrix algebras.- Fluctuations of the dicke maser.- Tangent bimodule and locality for dissipative operators on C*-algebras.- Noncommutative stochastic processes with independent and stationary additive increments.- The atom in the radiation field as a quantum stochastic process.
In this thesis interacting relativistic and non relativistic Quantum Field Theories (QFT) are studied, investigating their equilibrium configurations and their long time evolution in the framework of perturbative Algebraic Quantum Field Theory, studying also convergence in a specific model. In the first part, concerning the relativistic case, we study, in formal perturbation theory, interacting KMS states generalising results by Fredenhagen and Lindner to fermionic field theories. As an application their stability is investigated together with the characterisation of the Debye screening effect in plasmas via the explicit solution of the Semiclassical Maxwell equations. Connected to these results, we also initiate a systematic study of secular growths appearing in the truncated perturbative series and affecting the validity of perturbation theory in its long time predicting capability. We restrict to theories on Minkowski spacetime and provide, for interactions depending on time via a switching process, a sufficient condition preventing secular growths in the truncated perturbative series. In the second part, we focus on a model of non relativistic quantum field theory. We construct equilibrium states at positive temperature in the presence of a condensation phase for a gas of non relativistic Bose particles on an infinite space interacting through a localised two body interaction. The convergence is proven, both for the interacting KMS state and for the entropy of the interacting KMS state relative to the free KMS state. The strategy of our proof combines ideas of Algebraic QFT, Constructive QFT and methods of statistical mechanics in the operator algebraic setting. Limits where the localisation of the two-body interaction is removed are eventually discussed, in combination with limits of the other physical parameters of the theory such as temperature, strength of the interaction and chemical potential. Finally, in the appendix, we present results on the Araki-Uhlmann relative entropy in fermionic quantum field theories, as well as an entropy-area relation, obtained via semiclassical methods, for the cosmological horizon in the static patch of de Sitter spacetime sourced by a coherent excitation of a free quantum scalar field. This completes the collection of original results obtained during the PhD.
Abstract Berezin and Weyl quantization are renowned procedures for mapping commutative Poisson algebras of observables to their non-commutative, quantum counterparts. The latter is famous for its use on Weyl algebras, while the former is more appropriate for continuous functions decaying at infinity. In this work, we define a variant of the Berezin quantization map, which acts on the classical Weyl algebra W(E,0)\mathcal {W}(E,0)W(E,0) W ( E , 0 ) and constitutes a positive strict deformation quantization . This construction provides a natural framework to compare classical and quantum thermal equilibrium states of a Bose gas through the computation of their semi-classical limit. To this end, we first introduce a purely algebraic notion of KMS states for the classical Weyl algebra and establish that, in finite volume, there exists a unique such state, which can be interpreted as the Fourier transform of a Gibbs measure on a Hilbert space. We then construct a new class of classical KMS states that realize representations of the canonical commutation relations with infinite local density. These states arise as the semi-classical high-density limit of the quantum equilibrium states originally studied by Araki and Woods [5]. A key feature of our approach is that it preserves the macroscopic ground-state occupation of the Bose gas in the classical regime. Finally, we demonstrate that the infinite-volume classical states can be obtained as thermodynamic limits of finite-volume Gibbs states.
We survey some results obtained in the last 25 years to illustrate the following probabilistic quantization statement: quantum probability is not a generalization of classical probability but a deeper level of it. Generalizing the classical theory of orthogonal polynomials, one can show that any random field XXX admitting all the moments can be represented as the sum of three operators, which are natural extensions of the creation, annihilation, and preservation operators in the usual boson Fock quantum theory. These operators generate a noncommutative ∗*∗-algebra on which the quantum extension of the expected value relative to the probability distribution of the field XXX induces a quantum state. So, any classical algebraic probability space generates a quantum space with its own commutation relations. The Heisenberg commutation relation characterizes the classical fields, while the new type of commutation relations (of type II) appears in non-Gaussian cases. The same machinery, but applied to Bernoulli fields, leads to Fermi--Dirac anticommutation relations (see the introduction).
We survey some results obtained in the last 25 years to illustrate the following probabilistic quantization statement: quantum probability is not a generalization of classical probability but a deeper level of it. Generalizing the classical theory of orthogonal polynomials, one can show that any random field XXX admitting all the moments can be represented as the sum of three operators, which are natural extensions of the creation, annihilation, and preservation operators in the usual boson Fock quantum theory. These operators generate a noncommutative ∗*∗-algebra on which the quantum extension of the expected value relative to the probability distribution of the field XXX induces a quantum state. So, any classical algebraic probability space generates a quantum space with its own commutation relations. The Heisenberg commutation relation characterizes the classical fields, while the new type of commutation relations (of type II) appears in non-Gaussian cases. The same machinery, but applied to Bernoulli fields, leads to Fermi-Dirac anticommutation relations (see the introduction).