Classical microscopic theory of mixed states

Volker Werner, Noémie Benczer-Koller, P. Boutachkov +22 more

M. Yamamura, A. Kuriyama, Y. Tsue

To appear in those proceedings.OCR Output 'Invited talk presented by M. Y. at the conference on "Many-Body Physics", Coimbra, Portugal, mixed states in highly excited nucleus.5•°•7 been formulated as the Dirac canonical formalism with constraints in order to describe the time-dependent variational principle and thermo field dynamics.This theory has Fiolhais, have also developed a microscopic theory for mixed states based on both is investigated.4Two of the authors (M.Y. and A.K.), together with Providéncia and based on the thermo field dynamics and the variation of the thermodynamic potential the thermo field dynamicsz has progressed,3 and the relation between the treatments description of mixed states in many-fermion systems.}Also, the treatment based on For example, the thermal boson expansion theory has been studied in the microscopic various attempts to describe the systems in the excited states have been developed.particle physics.In the field of microscopic theory in nuclear many-body systems, in highly excited states, has been one of the interesting problems in quantum many-The theoretical study of systems in highly excited states, such as nucleus observed a correct classical counterpart is examined and explicitly constructed as "mixed-means of time-dependent variational procedure, a possible state which can offerIn order to investigate quantal systems governed by su(1,1)-algebra by

A. Kuriyama, M. Yamamura, João da Providência +1 more

A classical microscopic theory of mixed states has recently been formulated in order to deal with the theoretical description of nuclear phenomena observed in highly excited states. In this theory, which is here briefly reviewed, the degrees of freedom of real fermions are doubled by fictitious fermions, in the context of the formalism of thermofield dynamics. The requirement of static stability of the thermal state of equilibrium plays, in the theory, a relevant role. The possibility of constraining the dynamics of the fictitious degrees of freedom, in such a way as to eliminate spurious thermal excitations, is discussed. The concept of canonical collective variables for mixed states is analyzed. Boson expansions appropriate to describe collective excitations of hot quantal systems are introduced and their properties investigated. It is shown that thermal boson expansions based on the formalism of thermofield dynamics are free from formal inconsistencies which may be present in boson expansions derived by an ad hoc quantization of conventional thermal mean field theories. The formalism is applied to the Lipkin model, and the correlation energy of a hot system is discussed.

Yeshwant R. Waghmare

Paul Cooney

Arc V — Gravity & Quantum Theory Paper 6 Title Accessibility, Thermodynamics, and the Quantum Gap:Why Purification Is the Minimal Structural Upgrade Zenodo DOI 10.5281/zenodo.18225996 Description This paper addresses the structural gap between classical accessibility-based physics and quantum theory. While finite accessibility accounts naturally for horizons, thermodynamic irreversibility, and emergent geometry, it does not by itself explain quantum coherence, entanglement, or unitary evolution. This discrepancy is identified as the quantum gap. The analysis shows that classical accessibility dynamics generically lead to mixed states and irreversible information loss. To recover quantum phenomena, an additional structural principle is required. The paper argues that purification—the requirement that every mixed state arise from a larger pure state—is the minimal and unique upgrade capable of closing this gap without introducing geometric or ontological assumptions. Thermodynamic behavior is reinterpreted as accessibility collapse within a larger purified state space. Entropy emerges from marginalization over inaccessible degrees of freedom rather than from microscopic counting. The paper demonstrates that purification restores reversibility and coherence while remaining fully compatible with operational constraints. By isolating purification as the sole necessary extension beyond finite accessibility, the work sharply constrains possible routes from classical operational physics to quantum theory. Any alternative upgrade is shown to either over-assume structure or fail to recover core quantum features. Keywords purification; quantum foundations; thermodynamics; entropy; accessibility collapse; mixed states; operational quantum theory Notes Arc V — Gravity & Quantum Theory (structural bridge to quantum theory) Identifies the “quantum gap” in accessibility-based physics Purification isolated as the minimal necessary structural upgrade Thermodynamics reinterpreted as marginalization over inaccessible degrees Sets the foundation for post-geometric quantum mechanics

Seogjoo Jang