Search results for "Formalism"

Transitionless quantum driving in open quantum systems

2014

Abstract We extend the concept of superadiabatic dynamics, or transitionless quantum driving, to quantum open systems whose evolution is governed by a master equation in the Lindblad form. We provide the general framework needed to determine the control strategy required to achieve superadiabaticity. We apply our formalism to two examples consisting of a two-level system coupled to environments with time-dependent bath operators.

The algebra eigenstates method for some systems with spin-like interactions

2006

International audience; An extension of the algebra eigenstates formalism is proposed to solve the eigenvalue equation for a class of problems involving "spin interactions". The method is detailed for the harmonic oscillator, su(2) and su(1, 1) algebras. Special emphasis is given to the resolution of problems in vibronic spectroscopy involving doubly degenerate electronic states.

Dynamical Ising-like model for the two-step spin-crossover systems

2003

In order to reproduce the two-step relaxation observed experimentally in spin-crossover systems, we investigate analytically the static and the dynamic properties of a two-sublattice Ising-like Hamiltonian. The formalism is based on a stochastic master equation approach. It is solved in the mean-field approximation, and yields two coupled differential equations that correspond to the HS fractions of the sublattices A and B. Virginie.Niel@uv.es ; Jose.A.Real@uv.es

Perturbative results for two and three particle threshold energies in finite volume

2015

We calculate the energy of the state closest to threshold for two and three identical, spinless particles confined to a cubic spatial volume with periodic boundary conditions and with zero total momentum in the finite-volume frame. The calculation is performed in relativistic quantum field theory with particles coupled via a $\lambda \phi^4$ interaction, and we work through order $\lambda^3$. The energy shifts begin at ${\cal O}(1/L^3)$, and we keep subleading terms proportional to $1/L^4$, $1/L^5$ and $1/L^6$. These terms allow a non-trivial check of the results obtained from quantization conditions that hold for arbitrary interactions, namely that of L\"uscher for two particles and our re…

Spectroscopy of XY3Z (C3v) molecules: A tensorial formalism adapted to the O(3)⊃C∞v⊃C3v group chain

2005

Abstract A tensorial formalism adapted to the case of XY3Z symmetric tops has been developed. We use the O (3) ⊃ C∞v ⊃ C3v group chain. All the coupling coefficients and formulas for the computation of the matrix elements are given for this chain. Such relations are also deduced in C3v group itself.

Current-spin-density-functional study of persistent currents in quantum rings

2000

We present a numerical study of persistent currents in quantum rings using current spin density functional theory (CSDFT). This formalism allows for a systematic study of the joint effects of both spin, interactions and impurities for realistic systems. It is illustrated that CSDFT is suitable for describing the physical effects related to Aharonov-Bohm phases by comparing energy spectra of impurity-free rings to existing exact diagonalization and experimental results. Further, we examine the effects of a symmetry-breaking impurity potential on the density and current characteristics of the system and propose that narrowing the confining potential at fixed impurity potential will suppress t…

Quantum dots in magnetic fields: Unrestricted symmetries in the current spin-density functional formalism

1999

We apply the current spin-density functional formalism (CSDFT) of Vignale and Rasolt to two-dimensional quantum dots in magnetic fields. Avoiding any spatial symmetry restrictions of the solutions, we find that a broken rotational symmetry of the electronic charge density can occur in high magnetic fields.

EP-1186: Accuracy of the TG-43 dose calculation formalism for HDR skin brachytherapy

2013

Energy relaxation in a? 4 with long range interactions

1995

We investigate the influence of long range interactions on the relaxation behaviour of a lattice model with an on-site potential ofϕ 4-type and “infinite” range harmonic interactions. For finite number of particlesN, it is shown that the autocorrelation functions of the fluctuations of the one-particle energiesE n(t) decays exponentially. The corresponding relaxation time τ is proportional toN and is given by τ(T, N) =Nτ0(T). The temperature dependent time scale τ0 can explicitly be related to the dynamics of a one-particle correlator of the noninteracting system. The results are derived using Mori-Zwanzig projection formalism. The corresponding memory kernel is calculated within a mode cou…

Spectroscopy of XY5Z (C4v) Molecules: A Tensorial Formalism Adapted to the O(3) ⊃ Oh ⊃ C4v Chain

2000

Abstract A tensorial formalism adapted to the case of XY 5 Z symmetric tops has been developed as an extension of the usual one for the octahedral molecules. We use the O (3) ⊃ O h ⊃ C 4 v group chain. All the coupling coefficients and formulas for the computation of matrix elements are given for this chain. Such relations are also deduced in the C 4 v group itself.