Bruna Pinho - Academia.edu (original) (raw)
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UERJ - Universidade do Estado do Rio de Janeiro / Rio de Janeiro State University
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Papers by Bruna Pinho
The Astrophysical Journal, 1986
ABSTRACT A closure of the BBGKY hierarchy of galaxy correlation functions previously introduced b... more ABSTRACT A closure of the BBGKY hierarchy of galaxy correlation functions previously introduced by Davis and Peebles is considered. Its consequence on a second velocity moment is explicitly computed. Its consistency domain is shown to be limited to extremely short distances.
Journal of Statistical Physics, 1989
A unified formalism is presented to study Hamiltonian linear systems driven by noise. With this f... more A unified formalism is presented to study Hamiltonian linear systems driven by noise. With this formalism, the phase averaging approximation, valid at weak noise, is easily performed. Already known results are straightforwardly recovered and new ones are obtained. After introducing this formalism on the exactly solvable one-degree-of-freedom problem with uncorrelated noise, one studies the corresponding exponentially correlated case. The validity of the approximate results thus obtained is considered by investigating the systematic weak-disorder expansion beyond the quasilinear approximation. In particular, it is argued that this expansion behaves uniformly for weak and large correlation time. The two-degrees-of-freedom problem is completely solved at the lowdisorder approximation and this result is applied to the two-channel Anderson localization problem. The invariant measure and the two positive Lyapunov exponents are computed at all coupling between the channels. For systems with n degree of freedom the phase averaging leads to a Fokker-Planck equation for the measure in action space describing the system. However, it is argued that it is not solvable except in a special case which is explicitly displayed and solved. Nevertheless, in the large-n limit, it is possible to compute the largest Lyapunov exponent. Moreover, generalized Lyapunov exponents are calculated in this limit, and they do not exhibit a dispersion: in particular, log(d~}/(log d~> ~ 1, where 6 ~ is the energy of the system and where the brackets denote averaging over the noise. On the other hand, it is possible to compute at weak noise the sum of all the positive Lyapunov exponents. Taking into account all these results allows more insight on the whole spectrum of Lyapunov exponents.
Journal of Physics A: Mathematical and General, 1989
We study the phase diagram of the isotropic three-state chiral Potts model. Monte Carlo simulatio... more We study the phase diagram of the isotropic three-state chiral Potts model. Monte Carlo simulations performed on twisted square lattices with different sizes up to 64x64 indicate different types of critical curves. In particular, a floating phase seems to occur. Finite-size scaling analyses are performed at some specific critical points. The phase diagram we propose is discussed using exact results.
Malaysian Journal of Social Sciences and Humanities (MJSSH), 2020
Bantuan modal zakat merupakan salah satu bentuk bantuan yang disalurkan oleh agensi zakat di Mala... more Bantuan modal zakat merupakan salah satu bentuk bantuan yang disalurkan oleh agensi zakat di Malaysia bagi membantu golongan asnaf melibatkan diri dalam dunia perniagaan seterusnya merubah kehidupan mereka lebih baik dari sebelumnya. Oleh itu, terdapat beberapa isu yang timbul seperti berlaku penipuan ke atas bantuan yang diberikan, kegagalan usahawan asnaf dalam perniagaan, serta modal yang tidak mencukupi. Oleh yang demikian, kajian ini adalah bertujuan untuk mengenal pasti bentuk-bentuk bantuan modal yang disediakan oleh Institusi zakat serta mengenal pasti sejauhmanakah pencapaian bantuan modal membantu asnaf dalam perniagaan. Kajian ini telah menggunakan kaedah kualitatif iaitu menemu bual seramai 12 orang informan asnaf dan 5 orang pegawai zakat. Tema yang terhasil daripada persoalan pertama berkaitan dengan bentuk bantuan modal perniagaan ialah bantuan kemahiran, bantuan peralatan dan bantuan kewangan. Manakala tema yang terhasil daripada persoalan yang kedua iaitu pencapaian...
The Astrophysical Journal, 1986
ABSTRACT A closure of the BBGKY hierarchy of galaxy correlation functions previously introduced b... more ABSTRACT A closure of the BBGKY hierarchy of galaxy correlation functions previously introduced by Davis and Peebles is considered. Its consequence on a second velocity moment is explicitly computed. Its consistency domain is shown to be limited to extremely short distances.
Journal of Statistical Physics, 1989
A unified formalism is presented to study Hamiltonian linear systems driven by noise. With this f... more A unified formalism is presented to study Hamiltonian linear systems driven by noise. With this formalism, the phase averaging approximation, valid at weak noise, is easily performed. Already known results are straightforwardly recovered and new ones are obtained. After introducing this formalism on the exactly solvable one-degree-of-freedom problem with uncorrelated noise, one studies the corresponding exponentially correlated case. The validity of the approximate results thus obtained is considered by investigating the systematic weak-disorder expansion beyond the quasilinear approximation. In particular, it is argued that this expansion behaves uniformly for weak and large correlation time. The two-degrees-of-freedom problem is completely solved at the lowdisorder approximation and this result is applied to the two-channel Anderson localization problem. The invariant measure and the two positive Lyapunov exponents are computed at all coupling between the channels. For systems with n degree of freedom the phase averaging leads to a Fokker-Planck equation for the measure in action space describing the system. However, it is argued that it is not solvable except in a special case which is explicitly displayed and solved. Nevertheless, in the large-n limit, it is possible to compute the largest Lyapunov exponent. Moreover, generalized Lyapunov exponents are calculated in this limit, and they do not exhibit a dispersion: in particular, log(d~}/(log d~> ~ 1, where 6 ~ is the energy of the system and where the brackets denote averaging over the noise. On the other hand, it is possible to compute at weak noise the sum of all the positive Lyapunov exponents. Taking into account all these results allows more insight on the whole spectrum of Lyapunov exponents.
Journal of Physics A: Mathematical and General, 1989
We study the phase diagram of the isotropic three-state chiral Potts model. Monte Carlo simulatio... more We study the phase diagram of the isotropic three-state chiral Potts model. Monte Carlo simulations performed on twisted square lattices with different sizes up to 64x64 indicate different types of critical curves. In particular, a floating phase seems to occur. Finite-size scaling analyses are performed at some specific critical points. The phase diagram we propose is discussed using exact results.
Malaysian Journal of Social Sciences and Humanities (MJSSH), 2020
Bantuan modal zakat merupakan salah satu bentuk bantuan yang disalurkan oleh agensi zakat di Mala... more Bantuan modal zakat merupakan salah satu bentuk bantuan yang disalurkan oleh agensi zakat di Malaysia bagi membantu golongan asnaf melibatkan diri dalam dunia perniagaan seterusnya merubah kehidupan mereka lebih baik dari sebelumnya. Oleh itu, terdapat beberapa isu yang timbul seperti berlaku penipuan ke atas bantuan yang diberikan, kegagalan usahawan asnaf dalam perniagaan, serta modal yang tidak mencukupi. Oleh yang demikian, kajian ini adalah bertujuan untuk mengenal pasti bentuk-bentuk bantuan modal yang disediakan oleh Institusi zakat serta mengenal pasti sejauhmanakah pencapaian bantuan modal membantu asnaf dalam perniagaan. Kajian ini telah menggunakan kaedah kualitatif iaitu menemu bual seramai 12 orang informan asnaf dan 5 orang pegawai zakat. Tema yang terhasil daripada persoalan pertama berkaitan dengan bentuk bantuan modal perniagaan ialah bantuan kemahiran, bantuan peralatan dan bantuan kewangan. Manakala tema yang terhasil daripada persoalan yang kedua iaitu pencapaian...