Quantum Stochastic Processes and Noncommutative Geometry by Kalyan B. Sinha

By Kalyan B. Sinha

The classical concept of stochastic procedures has vital purposes bobbing up from the necessity to describe irreversible evolutions in classical mechanics; analogously quantum stochastic tactics can be utilized to version the dynamics of irreversible quantum platforms. Noncommutative, i.e. quantum, geometry offers a framework during which quantum stochastic buildings will be explored. This publication is the 1st to explain how those mathematical structures are similar. specifically, key rules of semigroups and entire positivity are mixed to yield quantum dynamical semigroups (QDS). Sinha and Goswami additionally enhance a common idea of Evans-Hudson dilation for either bounded and unbounded coefficients. the original positive aspects of the e-book, together with the interplay of QDS and quantum stochastic calculus with noncommutative geometry and a radical dialogue of this calculus with unbounded coefficients, will make it of curiosity to graduate scholars and researchers in practical research, likelihood and mathematical physics.

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Thus for all m ≤ n, ||T∗,tn (rm ) ([ρ]h )|| ≤ ||T∗,tn (rn ) ([ρ]h )|| ≤ ||T∗,tn (min) ([ρ]h )|| − (min) 0. 46 Quantum dynamical semigroups Keeping m fixed and letting n tend to ∞, we obtain that ||T∗,t0 (rm ) ([ρ]h )|| ≤ ||T∗,t0 (min) ([ρ]h )|| − 0; and then by letting m tend to ∞, ||T∗,t0 (min) ([ρ]h )|| ≤ ||T∗,t0 (min) ([ρ]h )|| − 0, ✷ which is clearly a contradiction. 13 The generator of (T∗,t J ; and we have the following minimality property. Whenever (T∗,t )t≥0 is a positive, C0 contraction semigroup on Ah,∗ whose (min) generator (say A ) extends Z + J , we must have T∗,t ≥ T∗,t for all t ≥ 0.

But by a simple computation it can be verified that T (X ) is the 4 × 4 matrix ⎛ ⎞ 2 0 −i 0 ⎜ 0 0 −i 0 ⎟ ⎜ ⎟, ⎝i i 1 1⎠ 0 0 1 1 which is not positive since its determinant = −2 < 0. We say that T is n-positive if Tk is positive for all k ≤ n, but not necessarily for k = n + 1. T is said to be completely positive (CP for short) if it is n-positive for each n. The role of positivity in classical probability is played by complete positivity in the quantum theory. Let us now formulate the notion of complete positivity in a slightly different but convenient language, namely that of positive definite kernels.

Take ρ1 = (1 − G/n)−1 σn+ (1 − G ∗ /n)−1 , ρ2 = (1 − G/n)−1 σn− (1 − G ∗ /n)−1 ; and observe that ||[ρ1 ]h || + ||[ρ2 ]h || = ||(1 − G/n)−1 σn+ (1 − G ∗ /n)−1 ||1 + ||(1 − G/n)−1 σn− (1 − G ∗ /n)−1 ||1 (as ρ1 , ρ2 are positive) ≤ ||σn+ ||1 + ||σn− ||1 = ||[σn+ ]h || + ||[σn− ]h || = ||[σn ]h || ≤ ||[ρ]h || + . Now, [ρ1 ]h − [ρ2 ]h = [(1 − G/n)−1 (σn+ − σn− )(1 − G ∗ /n)−1 ]h = [(1 − G/n)−1 σn (1 − G ∗ /n)−1 ]h = [ρ]h , because (σn+ − σn− ) ∼ σn implies (1 − G/n)−1 (σn+ − σn− )(1 − G ∗ /n)−1 ∼ (1 − G/n)−1 σn (1 − G ∗ /n)−1 .

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