Coherence annihilator

We introduce the eigenstates and eigenvalues for the creation and annihilation operators (coherent states86) ... 

If the dephasing time of the coherent phonons depend critically on the carrier density, photo-injection of carriers with the second pump pulse can annihilate them partially or completely, depending on its fluence but not on its relative timing. Such incoherent control was demonstrated for the LO phonons of GaAs [37],... 

The expectation value of H in the coherent state (7.17) can be evaluated explicitly for any Hamiltonian. However, an even simpler construction of Hd (valid to leading order in N) can be done (Cooper and Levine, 1989) by introducing intensive boson operators (Gilmore, 1981). In view of its simplicity, we report here this construction. If one divides the individual creation and annihilation operators by the square root of the total number of bosons, the relevant commutation relations become... 

Section IV is devoted to excitons in a disordered lattice. In the first subsection, restricted to the 2D radiant exciton, we study how the coherent emission is hampered by such disorder as thermal fluctuation, static disorder, or surface annihilation by surface-molecule photodimerization. A sharp transition is shown to take place between coherent emission at low temperature (or weak extended disorder) and incoherent emission of small excitonic coherence domains at high temperature (strong extended disorder). Whereas a mean-field theory correctly deals with the long-range forces involved in emission, these approximations are reviewed and tested on a simple model case the nondipolar triplet naphthalene exciton. The very strong disorder then makes the inclusion of aggregates in the theory compulsory. From all this study, our conclusion is that an effective-medium theory needs an effective interaction as well as an effective potential, as shown by the comparison of our theoretical results with exact numerical calculations, with very satisfactory agreement at all concentrations. Lastly, the 3D case of a dipolar exciton with disorder is discussed qualitatively. 

The coherent states of the photon field can be defined as the eigenvectors of the annihilation operator... 

Annihilation operator coherent states are the eigenstates of the annihilation operator and are parameterized by a complex eigenvalue. 

The Baker-Hausdorf formula cannot be used to solve this problem because the commutator of the annihilation as and creation a operators is not a c number. A numerical procedure, leading to the coefficients b was proposed by Buzek et al. [16]. In order to solve this problem analytically [18], it is of advantage to express the conventional coherent state, a), in the Fock representation in a different manner... 

The atoms interact with the quantized three-dimensional vacuum field and are also driven by a single-mode coherent laser field. We express the quantized multimode field in terms of the annihilation and creation operators and a x of field mode kr, which has wavevector k, frequency cd., and polarization ets. Thus, we write the electric field operator at position r in the form... 

This constant is essentially the limit of K as gi en by Eq. (5.14), in the case where the two absorbed photons become identical however, the factor rtiniY is replaced by n (n — 1) since the photon annihilation operator acts twice on the same radiation mode. As will be seen below, this difference is ultimately reflected in a dependence on the coherence properties of the laser source, which is uniquely associated with single-beam processes. It is also worth observing that although the first two terms of Eq. (5.13) become identical if the two absorbed photons are deiived from the same beam, inclusion of a factor of 2 in Eq. (6.1) would amount to double-counting the time-ordered diagrams, and is therefore not ap])ropriate. 

Nucleation considerations may dictate that the first oxide to form will have an epitaxial relationship with the substrate. This constraint will result in stress development because of the difference in lattice parameter between the metal and the oxide. This mechanism would only seem to generate significant stresses when the oxide is very thin, i.e., for short oxidation times and low oxidation temperatures. However, there are proposals that the action of intrinsic dislocations, in what amounts to a semi-coherent interface, in amuhilating vacancies during cationic scale growth can lead to sizeable stresses. However, there are also interface dislocation structures proposed, which could annihilate vacancies without generating significant stress. ... 

The last term in Eq. (116) describes the particle s interaction with a thermostat. We introduce the eigenfunctions and eigenvalues of creation and annihilation operators (coherent states) according to Ref. [50] ... 

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