Parametric Competition in non-autonomous Hamiltonian Systems

In this work we use the formalism of chord functions (\emph{i.e.} characteristic functions) to analytically solve quadratic non-autonomous Hamiltonians coupled to a reservoir composed by an infinity set of oscillators, with Gaussian initial state. We analytically obtain a solution for the characteristic function under dissipation, and therefore for the determinant of the covariance matrix and the von Neumann entropy, where the latter is the physical quantity of interest. We study in details two examples that are known to show dynamical squeezing and instability effects: the inverted harmonic oscillator and an oscillator with time dependent frequency. We show that it will appear in both cases a clear competition between instability and dissipation. If the dissipation is small when compared to the instability, the squeezing generation is dominant and one can see an increasing in the von Neumann entropy. When the dissipation is large enough, the dynamical squeezing generation in one of the quadratures is retained, thence the growth in the von Neumann entropy is contained

Quantum-state transfer in staggered coupled-cavity arrays

We consider a coupled-cavity array, where each cavity interacts with an atom under the rotating-wave approximation. For a staggered pattern of inter-cavity couplings, a pair of field normal modes each bi-localized at the two array ends arise. A rich structure of dynamical regimes can hence be addressed depending on which resonance condition between the atom and field modes is set. We show that this can be harnessed to carry out high-fidelity quantum-state transfer (QST) of photonic, atomic or polaritonic states. Moreover, by partitioning the array into coupled modules of smaller length, the QST time can be substantially shortened without significantly affecting the fidelity.Comment: 12 pages, 8 figure

Asymmetrical bloch branes and the hierarchy problem

We investigate a two scalar fields split braneworld model which leads to a possible approach to the hierarchy problem within the thick brane scenario. The model exhibits a resulting asymmetric warp factor suitable for this purpose. The solution is obtained by means of the orbit equation approach for a specific value of one of the parameters. Besides, we analyze the model qualitative behaviour for arbitrary parameters by inspecting the underlying dynamical system defined by the equations which give rise to the braneworld model. We finalize commenting on the metric fluctuation and stability issues.Comment: 8 pages, 7 figure

Constraining non-minimally coupled tachyon fields by Noether symmetry

A model for a spatially flat homogeneous and isotropic Universe whose gravitational sources are a pressureless matter field and a tachyon field non-minimally coupled to the gravitational field is analyzed. Noether symmetry is used to find the expressions for the potential density and for the coupling function, and it is shown that both must be exponential functions of the tachyon field. Two cosmological solutions are investigated: (i) for the early Universe whose only source of the gravitational field is a non-minimally coupled tachyon field which behaves as an inflaton and leads to an exponential accelerated expansion and (ii) for the late Universe whose gravitational sources are a pressureless matter field and a non-minimally coupled tachyon field which plays the role of dark energy and is the responsible of the decelerated-accelerated transition period.Comment: 11 pages, 5 figures. Version accepted for publication in Classical and Quantum Gravit

Doses e epocas de aplicacao de nitrogenio sobre a produtividade e caracteristicas comerciais de alho.

O trabalho foi conduzido no periodo de abril a outubro de 1991, no Campo Experimental da Universidade Federal de Lavras para avaliar a influencia de doses de nitrogenio e epocas de aplicacao sobre a produtividade e caracteristicas comerciais do alho (Allium sativum L.). Utilizou-se o delineamento de blocos ao acaso no esquema fatorial5 x 3, compreendendo cinco doses de nitrogenio (40; 60; 80; 100 e 120 kg/ha de N) e tres epocas de aplicacao (30; 50 e 70 dias apos o plantio (dap)) e 3 repeticoes. O nitrogenio e as epocas de aplicacao, atuaram independentemente sobre a produtividade total, observando-se efeito linear com o aumento das doses de nitrogenio e epocas de aplicacao. Houve reducao na produtividade comercial com o aumento das doses de nitrogenio. A dose de N de 40 kg/ha proporcionou as maiores produtividades comerciais independente- mente se aplicado aos 30 dap (5.076 kg/ha), 50 dap (5.502 kg/ha) ou 70 dap apos o plantio (4.086 kg/ha). A aplicacao em cobertura mais tardiamente (70dap) propiciou, de forma geral, as menores produtividades comerciais. Com o aumento das doses de nitrogenio, em funcao das epocas de plantio, verificou-se aumento linear na per- centagem de bulbos pseudoperfilhados, sendo que a dose de N de 40 kg/ha e aplicacoes aos 30 dap (30,6%); 50 dap (34,9%) e 70 dap (42,0%), apresentaram as menores percentagens de bulbos pseudoperfilhados. Com a dose de N de 120 kg/ha aplicada aos 30; 50 e 70 dap a incidencia de bulbos pseudoperfilhados foi 65,2%; 68,8% e 64,8%, respectivamente. Para peso medio de bulbo observou-se efeitos lineares para doses de nitrogenio e epocas de aplicacao, assim como constatou-se aumento no numero de bulbilhos por bulbo, com o incremento das doses de nitrogenio