Papers by Arnaldo Santiago
Il Nuovo Cimento A
Summary The evolution of bubbles with arbitrary initial density in an infinite nuclear system is... more Summary The evolution of bubbles with arbitrary initial density in an infinite nuclear system is studied including kinetic-pressure fluctuations on the bubble surface. The critical radius and probability for bubble expansion are found to depend significantly upon both the initial bubble density and the nuclear equation of state.
Revista do Professor de Física
Apresentamos uma proposta de ensino na área de eletromagnetismo (motor de corrente continua - cc)... more Apresentamos uma proposta de ensino na área de eletromagnetismo (motor de corrente continua - cc) com foco nas atividades práticas segundo a conceituação de Piaget, aqui extrapolada para incluir os objetos em ambientes virtuais. Montamos em sala de aula um motor elétrico de cc, para discutir conceitos da teoria eletromagnética. Realiza-se a modelagem física e sua simulação em computador utilizando o software educacional Modellus. Em ambas as situações, no laboratório didático com o objeto de estudo real, e no laboratório virtual com a simulação do objeto, os participantes mostram intenso interesse, ilustrando as potencialidades da aprendizagem ativa.
AIP Conference Proceedings
Nuclear matter properties are calculated in the relativistic mean field theory with the excluded ... more Nuclear matter properties are calculated in the relativistic mean field theory with the excluded volume effects by using a number of different parameter sets. The results show that the incompressibility K0 assumes reasonable value; the density symmetry L is around 100 MeV, and the symmetry incompressibility Ks has positive sign in models without EVE, but may be negative if EVE is took into account. In almost all parameter sets there exists a critical point where the incompressibility equals zero, but for a few parameter sets there is no critical point and the pure neutron matter is predicted to be bound.
Recen Revista Ciencias Exatas E Naturais, Dec 14, 2010
Resumo: O descobrimento e o desenvolvimento de técnicas utilizando a tecnologia com material radi... more Resumo: O descobrimento e o desenvolvimento de técnicas utilizando a tecnologia com material radioativo proporcionou benefícios a diversos segmentos da sociedade. Dentre eles, o setor de alimentos que, por meio desses, não só conseguiu abrandar, mas também evitar uma série de ocorrências hospitalares, ao mesmo tempo que obteve aumento da lucratividade nos produtos perecíveis por meio do uso de feixes radioativos. A irradiação pode contribuir muito para minimizar a ação de microorganismos, que diminuem a vida útil dos alimentos, bem como em processos de esterilização. Desmistificar a teoria e dar informações cientificamente embasadas à população, que tem receio da utilização dessas técnicas, é função dos que trabalham na área. Nesse sentido, o professor de ensino médio, se bem informado, pode contribuir com a popularização das tecnologias nucleares.
A disciplina de Eletromagnetismo é conhecida na física básica como aquela com maior grau de dific... more A disciplina de Eletromagnetismo é conhecida na física básica como aquela com maior grau de dificuldades de compreensão, tanto em nível conceitual quanto ao que se refere aos cálculos efetuados. As dificuldades encontradas por tantos alunos, mesmo com várias obras afins no mercado foi à principal motivação dos autores, acostumados a ministrar esta disciplina em diferentes instituições. Sendo um curso básico, tivemos o cuidado de prepará-lo usando as ferramentas matemáticas compatíveis com a formação curricular desse aluno, como por exemplo, fazendo uso quase exclusivo de coordenadas cartesianas, sem, contudo, poupar a árdua tarefa de deduzir passagens matemáticas, que na maioria das vezes são deixadas como tarefas para os alunos, que na verdade nem sempre as realizam e comprometem assim a evolução da construção de seu aprendizado. Além disso, resolvemos na íntegra um grande número de exercícios, apresentados como exemplos ao longo do texto, conciliando assim teoria e prática e suas ...
Revista Brasileira de Ensino de Física, 2005
Discutimos um método bastante simples de se introduzir o estudo do oscilador x 3 amortecido, tant... more Discutimos um método bastante simples de se introduzir o estudo do oscilador x 3 amortecido, tanto teórica como experimentalmente, em cursos elementares de Física. Dados experimentais do deslocamento de um oscilador x 3 em função do tempo, obtidos em medidas de ultrasom, são bem reproduzidos quando forças dissipativas são levadas em conta através de umúnico parâmetro. Palavras-chave: oscilador X 3 , amortecimento, ensino de Física. A simple method for introducing a damped x 3 oscillator in basic courses is discussed. The oscillator position as a function of time obtained from ultrason measurement are well reproduced in the case when the damping effects are taken into account through a single free parameter.
Physical Review C, 1999
The standard nuclear matter incompressibility K0 is determined by a data fit based on a model of ... more The standard nuclear matter incompressibility K0 is determined by a data fit based on a model of nuclear energy functional and the scaling assumption of the nuclear breathing mode. The selected nuclear data used in this fit are taken from a limited set of nuclei which have both the measured mass M and the isoscalar giant monopole resonance energy EM. The obtained value of K0, based on 26 experimental points corresponding to 18 spherical nuclei with 89<=A<=209, is 220+/-20 MeV.
Physical Review C, 1998
An absorption model based on the eikonal approximation of the nuclear optical model is proposed f... more An absorption model based on the eikonal approximation of the nuclear optical model is proposed for the transverse and the forward energy distributions in ultrarelativistic heavy-ion collisions. It is shown that the measured distributions can be expressed by their geometric distribution convoluted by a Gaussian distribution with centroid and width determined by the collision geometry and the average properties of N-N collisions. This result provides a physical argument for the formula used in the data fitting of the transverse energy distribution in the literature. The forward energy distribution formula is shown to be applicable for the data fitting.
Physical Review C, 1997
A Thomas-Fermi theory with a linear scaling assumption is proposed for the breathing mode of nucl... more A Thomas-Fermi theory with a linear scaling assumption is proposed for the breathing mode of nuclear collective motion. It leads to a general result KA=+KGD-2EC/A which states that the incompressibility KA of a finite nucleus A mainly equals the nuclear matter incompressibility K(rho,delta) averaged over the nucleon density distribution rho(r) of nucleus A, added to a term KGD contributed from the gradients of nucleon densities, with twice the Coulomb energy per nucleon EC/A subtracted. The nuclear matter equation of state given by the Thomas-Fermi statistical model with a Seyler-Blanchard-type interaction is employed to calculate the nuclear matter incompressibility K(rho,delta) and a localized approximation of the Seyler-Blanchard-type interaction, which is shown to be similar to the Skyrme-type interaction, is developed to calculate the value of KGD. KGD and -2EC/A contribute about 20-10 % and 1-5 %, respectively, to the nuclear incompressibility KA, from the light to the heavy nuclei. The shell and the even-odd effects are discussed by a scaling model which shows that these effects can be neglected for medium and heavy nuclei. The anharmonic effect is shown to be significant only for light nuclei. The leptodermous expansion of KA is obtained and the contribution from the curvature term proportional to A-2/3 is discussed. The calculated isoscalar giant monopole resonance energy EM for a variety of nuclei are shown to be in agreement with experimental measurements.
Physical Review C, 2000
ABSTRACT A comparison of the nuclear matter equations of state based on Skyrme, Myers-Swiatecki, ... more ABSTRACT A comparison of the nuclear matter equations of state based on Skyrme, Myers-Swiatecki, and Tondeur interactions is given. It is shown that the difference among these equations of state is not significant in most of the relative neutron excess range which is of interest for both heavy ion collisions and supernova explosion calculations. However, if the equation is fitted to the same standard state, the equation based on the Tondeur interaction is softer than others provided the relative neutron excess is not close to 0.
Physical Review C, 1999
The nuclear central density is calculated from the nuclear charge-density parameters measured by ... more The nuclear central density is calculated from the nuclear charge-density parameters measured by elastic electron scattering and muonic atom spectroscopy. The nucleon number and asymmetry dependences of the obtained nuclear central density are discussed based on the macroscopic description of nuclei. It is shown that the nuclear central density decreases slowly as the nucleon number or the nuclear asymmetry increases. The proton number and neutron number dependences of the nuclear central density show some structure that seems like the shell effect, since density peaks are formed around the proton and neutron magic numbers. The data fit to the nuclear half density radii measured by muonic atom spectroscopy yields the nuclear radius constant r0=1.141 fm, and the data fit to the calculated nuclear central densities gives an estimation for the nuclear matter incompressibility K0 in the range around 220-250 MeV.
International Journal of Mathematical Education in Science and Technology, 2009
In basic physics courses at undergraduate level, the dynamics of self-propelled bodies is present... more In basic physics courses at undergraduate level, the dynamics of self-propelled bodies is presented as an example of momentum conservation law applied to systems with time-varying mass. However, is often studied the simple situation of free motion or the motion under the action of a constant gravitational field. In this work, we investigate the more realistic case of time-dependent motion
European Journal of Physics, 2008
We present a study of the ascending vertical motion of a self-propelled body under a uniform grav... more We present a study of the ascending vertical motion of a self-propelled body under a uniform gravitational field suffering the action of two different types of air friction forces: linear on the velocity, which is valid for slowly moving bodies, and quadratic on the velocity. We study the special case where the thrust force is a decreasing function of mass,
European Journal of Physics, 2009
ABSTRACT In continuation of a previous work [1], we present an analytic study of ascending vertic... more ABSTRACT In continuation of a previous work [1], we present an analytic study of ascending vertical motion of a rocket subjected to a quadratic drag for the case where the mass-variation law is a linear function of time. We discuss the detailed analytical solution of the model differential equations in closed form. Examples of application are presented and discussed. This paper is intended for undergraduate physics teachers and for graduate students.
Communications in Theoretical Physics, 2006
Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties ... more Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy a1 and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility K0 much higher than expected. For most parameter sets there exists a critical point (ρc, δc), where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M , which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass (1.2M) is obtained for r 0.9 fm.
… in Theoretical Physics, 2006
Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties ... more Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy a1 and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility K0 much higher than expected. For most parameter sets there exists a critical point (ρc, δc), where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M , which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass (1.2M) is obtained for r 0.9 fm.
… in Theoretical Physics, 2006
Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties ... more Effects of excluded volume of nucleons on nuclear matter are studied, and the nuclear properties that follow from different relativistic mean-field model parametrizations are compared. We show that, for all tested parametrizations, the resulting volume energy a1 and the symmetry energy J are around the acceptable values of 16 MeV and 30 MeV, and the density symmetry L is around 100 MeV. On the other hand, models that consider only linear terms lead to incompressibility K0 much higher than expected. For most parameter sets there exists a critical point (ρc, δc), where the minimum and the maximum of the equation of state are coincident and the incompressibility equals zero. This critical point depends on the excluded volume parameter r. If this parameter is larger than 0.5 fm, there is no critical point and the pure neutron matter is predicted to be bound. The maximum value for neutron star mass is 1.85M , which is in agreement with the mass of the heaviest observed neutron star 4U0900-40 and corresponds to r = 0.72 fm. We also show that the light neutron star mass (1.2M) is obtained for r 0.9 fm.
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Papers by Arnaldo Santiago