The Operator Algebra and the Hamiltonian Formalism

Xijia Miao

A general operator algebra formalism is proposed for describing the unitary time evolution of multilevel spin systems. The time-evolutional propagator of a multilevel spin system is decomposed completely into a product of a series of elementary propagators. Then the unitary time evolution of the system can be determined exactly through the decomposed propagator. This decomposition may be simplified with the help of the properties of the finite dimensional Liouville operator space and of its three operator subspaces, and the operator algebra structure of spin Hamiltonian of the system. The Liouville operator space contains the even-order multiple-quantum, the zero-quantum, and the longitudinal magnetization and spin order operator subspace, and moreover, each former subspace contains its following subspaces. The propagator can be decomposed readily and completely for a spin system whose Hamiltonian is a member of the longitudinal magnetization and spin order operator subspace. If the Hamiltonian of a spin system is a zero-quantum operator this decomposition may be implemented by making a zero-quantum unitary transformation on the Hamiltonian to convert it into the diagonalized Hamiltonian, while if the Hamiltonian is an even-order multiple-quantum operator the decomposition may be carried out by diagonalizing the Hamiltonian with an even-order multiple-quantum unitary transformation. When the Hamiltonian is a member of the Liouville operator space but not any element of its three subspaces the decomposition may be achieved first by making an odd-order multiple-quantum and then an even-order multiple-quantum unitary transformation to convert it into the diagonalized Hamiltonian. Parameter equations to determine the unknown parameters in the decomposed propagator are derived for the general case and approaches to solve the equations are proposed.

Felix Meier, Daniel Waltner, Petr A. Braun +1 more

Abstract We derive a formalism to express the spin algebra <?CDATA $\mathfrak{s}\mathfrak{u}(2)$?> s u ( 2 ) in a spin s representation in terms of the algebra of L fermionic operators that obey the canonical anti-commutation relations. We also give the reverse direction of expressing the fermionic operators as polynomials in the spin operators of a single spin. We extend here to further spin values the previous investigations by Dobrov (2003 J. Phys. A: Math. Gen. 36 L503) who in turn clarified on an inconsistency within a similar formalism in the works of Batista and Ortiz (2001 Phys. Rev. Lett. 86 1082). We then consider a system of L fermion flavors and apply our mapping in order to express it in terms of the spin algebra. Furthermore we investigate a possibility to simplify certain Hamiltonian operators by means of the mapping.

Jan Hamhalter

Zen Revista, 10 MFC

Mathematical Applications of Science Fiction We present a rigorous derivation of the spectral inversion map for modular Hamiltonians within the framework of Type III von Neumann algebras, particularly those arising in the algebraic formulation of holographic field theories. By introducing a measure of Non-Commutative Kolmogorov Complexity defined on the predual space of the operator algebra, we establish a direct correspondence between the algorithmic information content of a quantum state and the spectral density of its associated modular operator. We prove that the reconstruction of bulk operators from boundary data is formally equivalent to a spectral inversion problem subject to an algorithmic entropy bound. To this end, we construct the Valerius–Kolmogorov Operator, a unitary mapping that retrieves information from the island regions of the entanglement wedge by inverting the modular flow. We provide detailed proofs of the existence, uniqueness, and stability of this inversion, showing that unitary information retrieval is possible precisely when the complexity growth of the modular flow is subexponential. This framework resolves the trans-temporal information leakage paradox in black hole evaporation models by interpreting Hawking radiation as a complexity-encoded modular scramble.

Mich�le Irac-Astaud