1,720,984 research outputs found
Detailed Balance, time reversal and generators of Quantum Markov Semigroups
No full textWe characterize generators L of norm continuous quantum Markov semigroups satisfying the quantum detailed balance condition with respect to an antiunitary time reversal in terms of the operators H and L k in the Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) representation L(x) = i[H, x] − (1/2)\sum_k (L^*_k L_k x − 2L^*_k x L_k + x L^*_k L_k )
Generators of KMS Symmetric Markov Semigroups on B(h) Symmetry and Quantum Detailed Balance.
No full textWe find the structure of generators of norm-continuous quantum Markov semigroups on B(h) that are symmetric with respect to the scalar product induced by a faithful normal invariant state ρ and satisfy two quantum generalisations of the classical detailed balance condition related with this non-commutative notion of symmetry: the so-called standard detailed balance condition and the standard detailed balance condition with an antiunitary time reversal
GENERIC QUANTUM MARKOV SEMIGROUPS, CYCLE DECOMPOSITION AND DEVIATION FROM EQUILIBRIUM
No full textA generic quantum Markov semigroup T of a d-level quantum open system with a faithful normal invariant state ρ admits a dual semigroup with respect to the scalar product induced by ρ. We show that the difference of the generator L and its adjoint can be written as the sum of a derivation 2i[H, ·] and a weighted difference of automorphisms.
The formula we prove allows us to represent the deviation from equilibrium (in a “small” time interval) as the superposition of cycles of the system where the difference between the forward and backward evolution is written as the difference of a reversible evolution and its time reversal. Moreover, it generalises cycle decomposition of Markov jump processes.
We also find a similar formula with partial isometries instead of unitaries
Generators of detailed balance quantum Markov semigroups
No full textFor a quantum Markov semigroup T on the algebra B(h) with a faithful invariant state, we defne an adjoint T' with respect to the scalar product determined by the invariant state. In this paper, we solve the open problems of characterizing adjoints T' that are also a quantum Markov semigroup and satisfy the detailed balance condition in terms of the operators
in the Gorini-Kossakowski-Sudarshan-Lindblad representation of the generator of T
Quantum detailed balance conditions with time reversal: three-level systems
No full textThe classical detailed balance, or reversibility, condition admits several non-commutative extensions. We discuss the most appropriate in view of our previous results and the complete case study of three-level systems
Quantum detailed balance conditions with time reversal: the finite-dimensional case.
No full textWe classify generators of quantum Markov semigroups T on B(h), with h finite dimensional and with a faithful normal invariant state satisfying the standard quantum detailed balance condition with an anti-unitary time reversal commuting with . Our results also show that it is possible to find a standard form for the operators in the Lindblad representation of the generators extending the standard form of generators of quantum Markov semigroups satisfying the usual quantum detailed balance condition with non-symmetric multiplications whose generators must commute with the
modular group associated with . This supports our conclusion that the most appropriate noncommutative version of the classical detailed balance condition is the above standard quantum
detailed balance condition with an anti-unitary time reversal
Spectral properties of the two-photon absorption and emission process
No full textThe quantum Markov semigroup of the two-photon absorption and emission process has two extremal normal invariant states. Starting from an arbitrary initial state it converges toward some convex combination of these states as time goes to infinity (approach to equilibrium). We compute the exact exponential rate of this convergence showing that it depends only on the emission rates. Moreover, we show that off-diagonal matrix elements of any initial state go to zero with an exponential rate which is smaller than the exponential rate of convergence of the diagonal part. In other words quantum features of a state survive longer than the relaxation time of its classical part
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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