We extend the concept of Wigner-Yanase-Dyson skew information to something we call "metric adjusted skew information" (of a state with respect to a conserved observable). This "skew information" is intended to be a non-negative quantity bounded by the variance (of an observable in a state) that vanishes for observables commuting with the state. We show that the skew information is a convex function on the manifold of states. It also satisfies other requirements, proposed by Wigner and Yanase, for an effective measure-of-information content of a state relative to a conserved observable. We establish a connection between the geometrical formulation of quantum statistics as proposed by Chentsov and Morozova and measures of quantum information as introduced by Wigner and Yanase and extended in this article. We show that the set of normalized Morozova-Chentsov functions describing the possible quantum statistics is a Bauer simplex and determine its extreme points. We determine a particularly simple skew information, the "λ-skew information," parametrized by a λ ∈ (0, 1], and show that the convex cone this family generates coincides with the set of all metric adjusted skew informations.convexity | monotone metric | Morozova-Chentsov function | λ-skew information I n the mathematical model for a quantum mechanical system, the physical observables are represented by self-adjoint operators on a Hilbert space. The "states" (that is, the "expectation functionals" associated with the states) of the physical system are often "modeled" by the unit vectors in the underlying Hilbert space. So, if A represents an observable and x ∈ H corresponds to a state of the system, the expectation of A in that state is (Ax | x). For what we shall be proving, it will suffice to assume that our Hilbert space is finite dimensional and that the observables are self-adjoint operators, or the matrices that represent them, on that finite dimensional space. In this case, the states can be realized with the aid of the trace (functional) on matrices and an associated "density matrix." We denote by Tr(B) the usual trace of a matrix B [that is, Tr(B) is the sum of the diagonal entries of B]. The expectation functional of a state can be expressed as Tr(ρA), where ρ is a matrix, the density matrix associated with the state, and "Tr(ρA)" is the trace of the product ρA of the two matrices ρ and A. (Henceforth, we write "Tr ρA" omitting the parentheses when they are clearly understood.)In ref. 1, Wigner noticed that in the presence of a conservation law the obtainable accuracy of the measurement of a physical observable is limited if the operator representing the observable does not commute with (the operator representing) the conserved quantity (observable). Wigner proved it in the simple case where the physical observable is the x-component of the spin of a spin one-half particle and the z-component of the angular momentum is conserved. Araki and Yanase (2) demonstrated that this is a general phenomenon and pointed out, following Wigner's example, that u...
Given a Hermitian operator, a monotone convex function f and a subspace E , dim E < ∞ , there exists a unitary operator U on E such that f (A E) Uf (A) E U *. (Here X E denotes the compression of X onto E). A related result is: For a monotone convex function f , 0 < α, β < 1 , α + β = 1 , and Hermitian operators A , B on a finite dimensional space, there exists a unitary U such that f (αA + βB) U{αf (A) + βf (B)}U *. More general convexity results are established. Also, several old and new trace inequalities of Brown-Kosaki and Hansen-Pedersen type are derived. We study the behaviour of the map p −→ {(A p) E } 1/p , A 0 , 0 < p < ∞. Mathematics subject classification (2000): 47A20, 47A30, 47A63.
(To be submitted to Nucl. Instr. Meth. A) described. electrons, muons, neutrinos (from missing energy), charged hadrons, ·rr°'s and V°'s is of the detector is its ability to identify particles; the performance in identification of hadrons, and the accuracy obtained in energy and angle is given. An essential property of charged tracks is specified. Calorimeters are used to measure photons and neutral accuracy of the tracking detectors to measure the impact parameter and momentumThe performance of the ALEPH detector at the LEP e+e' collider is reviewed. The Abstract The ALEPH Collaboration" Performance of the ALEPH detector at LEP
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