Física

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Programa de Pós-Graduação em Física

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A classificação de Bianchi e a construção de Taub das métricas cosmológicas anisotrópicas
(Universidade Federal do Espírito Santo, 2024-07-15) Scardini, Lucas Oliveira; Gonçalves, Sergio Vitorino de Borba ; https://orcid.org/; http://lattes.cnpq.br/; https://orcid.org/; http://lattes.cnpq.br/; Monerat, Germano Amaral; https://orcid.org/; http://lattes.cnpq.br/; Alvarenga, Flávio Gimenes; https://orcid.org/; http://lattes.cnpq.br/; Spalenza, Wesley; https://orcid.org/; http://lattes.cnpq.br/
The study of the cosmos is of utmost importance for understanding the origin of the Universe. One of the foundations in these studies is the metric used, which is commonly homogeneous and isotropic. However, there are works that utilize anisotropic or inhomogeneous metrics. Anisotropic metrics have been divided into different types by the work of Abraham Taub, who based his classification on Luigi Bianchi’s classification of anisotropic manifolds. This dissertation has two objectives: the first is to construct anisotropic metrics starting with a simple review of general relativity. The second is to demonstrate the importance of studying models that do not adhere to the cosmological principle
A Dinâmica Cosmológica na gravidade f(R,T)
(Universidade Federal do Espírito Santo, 2023-09-14) Dias, Ana Paula Jeakel; Velten, Hermano Endlich Schneider; https://orcid.org/0000000251557998; http://lattes.cnpq.br/0282590467459210; https://orcid.org/; http://lattes.cnpq.br/6453445416677178; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Carames, Thiago Roberto da Possa; https://orcid.org/0000-0001-6349-8297; http://lattes.cnpq.br/0327463936831546
We begin with a comprehensive analysis of the key concepts in General Relativity and Cosmology, thus laying a strong foundation that will enable a thorough understanding of the central topic addressed in this research. Subsequently, we delve into the core of this study, where we conduct a detailed review of the current state of f(R; T) theories, where T represents the trace of the energy-momentum tensor Tμν, concerning the evolution of the cosmological background expansion of Friedmann-Lemaître-Robertson-Walker (FLRW). We start focusing on the modified Friedmann equations for the case of a minimally coupled gravitational Lagrangian of the type f(R; T) = R+ αeβΤ + γnTn. With this choice one covers all existing proposals in the literature via four free parameters. All relevant f(R; T) models as well as the CDM model can be achieved in the appropriate limit. We show that in such a minimally coupled case there exists a useful constraining relation between the effective total matter density with an arbitrary equation of state parameter and the modified gravity parameters. Then, with this association the modified gravity sector can be independently constrained using estimations of the gas mass fraction in galaxy clusters. Further, using cosmological background cosmic chronometers data and demanding the universe is old enough to accommodate the existence of Galactic globular clusters with estimated age of at least ~ 14 Gyrs we find a narrow range of the modified gravity free parameter space in which this class of theories remains viable for the late time cosmological evolution. As expected, this preferred parameter space region accommodates the CDM limit of f(R; T) models. However, when analysing the cosmological dynamics including a radiation component, we find that this energy density interacts with the matter field and it does not scale according to the typical a-4 behavior, being a the scale factor. We conclude stating that f(R; T) gravity is not able to provide a full cosmological scenario and should be ruled out as a modified gravity alternative to the dark energy phenomena.
A energia de Casimir e a energia de transição de fase Ferromagnética em Duplas Perovskquitas
(Universidade Federal do Espírito Santo, 2017-05-26) Rocha, Jefferson Rodrigues; Orlando, Marcos Tadeu D’Azeredo; Orlando, Marcos Tadeu DAzeredo; Nogueira, José Alexandre; Batista, Antonio Brasil; Soares, Jacyra Ramos; Orlando, Marcos Tadeu D’Azeredo; Justo Filho, João Francisco
This thesis is based on Bordag’s theory of Casimir energy. This proposal relates the Casimir energy between conductor plasma planes and the thermal energy in the transition in double ferromagnetic conductive perovskites. Using this association it was possible to calculate the critical temperature of Curie ???? relating the fraction of the energy between these materials and the parameters of Sommerfeld ?? of each compound. To evaluate experimentally our proposal we considered the transition temperatures ???? and the parameters of 3 samples: ????2??????????6,????2?? ????????6 e ????2?? ????????6.We have found that for these samples the distance ?? between the conducting planes is associated with the Curie temperature Tc. Our proposal for the calculation of ???? is consistent with the values found in the literature for samples with these characteristics (ferrometal and conductive). Based on our theory we proposed the preparation of a new sample that presented a parameter ?? similar to that of the sample ????2??????????6 thus generating a Curie temperature ???? ˜ 635??,namely:????1.8??0.2??????????6. This new compound is a double perovskite with ferromagnetic metallic characteristics and octahedral geometry formed by planes containing ??????6 and presenting ?? ?? = 635??.
A Equação de Schroedinger em um Cenário de Comprimento Mínimo.
(Universidade Federal do Espírito Santo, 2019-11-29) Goncalves, André Oakes de Oliveira; Nogueira, Jose Alexandre; https://orcid.org/; http://lattes.cnpq.br/6774401855734421; https://orcid.org/; http://lattes.cnpq.br/; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Furtado, Raphael Goes; https://orcid.org/; http://lattes.cnpq.br/; Dorsch, Glauber Carvalho; https://orcid.org/; http://lattes.cnpq.br/; Constantinidis, Clisthenis Ponce; http://lattes.cnpq.br/1328163673123152; Spalenza, Wesley; Francisco, Ronald Oliveira; Marra, Valerio; https://orcid.org/0000000277731579; http://lattes.cnpq.br/6846011112691877
In order to quantify a gravitation, several images predicted the existence of a third length in nature. The retrieval mechanism is quantum mechanics WHERE Heisenberg s principle is modified, making it impossible for the uncertainty particle position to be
A Influência da mecanossíntese na estabilização da fase tipo NaZn13 nos compostos [La0,95(RE)0,05]Fe11,4Si1,6 (RE = Y ou Gd)
(Universidade Federal do Espírito Santo, 2007-10-30) Alves, André Luíz; Proveti, José Rafael Cápua; Caetano, Edson Passamani; Nunes Filho, Evaristo; Sommer, Rubem Luis; Larica, Carlos
We have studied the stabilization of NaZn13 phase in the intermetallic compound of generic composition LaFe11,4sp1,6 (sp = Si, Al). This stabilization was investigated through the partial substitution of Fe by atoms of Al and Si, and trough the substitution of La by Y or Gd, which are rare earths elements with no orbital contribution to the magnetic moments. We have chosen to study the compounds with stoichiometry LaFe11,4sp1,6 (sp = Al, Si), with y = 0,88, for which compounds are metamagnetic. We firstly studied NaZn13 phase formation in some mixed compounds of composition LaFe11,4(AlxSi1-x)1,6 (0 less or equals x less or equals 1), prepared using an electric arc furnace. The compounds were characterized by Mössbauer Spectroscopy, X Rays Diffraction and Energy Dispersive X Ray Spectroscopy. Some compositions have a predominant NaZn13 phase, while in other regions the fraction of the NaZn13 phase is relative small due to the presence of other phases formed by segregation. We have also investigated the partial substitution of La atoms by atoms of Y and Gd, in the following compounds La1-x(RE)xFe11,4Si1,6 (RE = Gd or Y), with x= 5%. This substitution doesn t modify significantly the stabilization of the NaZn13 phase compared to the non-substituted compound and the fraction of the segregated a-Fe phase is maintained around 50%. We have used a new procedure using the mechanical alloying to prepare LaFe11,4Si1,6 compounds. It consists in submitting the melted sample to a 0.5 to 1 hour long high energy ball milling process and then in annealing the sample. The process induced a significant reduction of the rich-Fe phase formation compared to a conventional process. Therefore, the process allows to obtain samples with a higher fraction of the desired NaZn13 phase. Therefore, the process allows obtaining samples with a higher fraction of the desired NaZn13 phase
A Quantização da Gravitação em 3D com Constante Cosmológica Positiva
(Universidade Federal do Espírito Santo, 2012-07-31) Almaraz, Zui Agustin Oporto; Constantinidis, Clisthenis Ponce; Piguet, Olivier; Vanzella, Daniel Augusto Turolla; Ribeiro, Maria Cristina Batoni Abdalla; Alvarenga, Flávio Gimenes; Gomes, Jose Francisco; Gonçalves, Sergio Vitorino de Borba
It was shown by Bonzom and Livine that 2+1 gravity with cosmological constant contains an ambiguity that depends on a Barbero–Immirzi-like parameter ? known from 4D gravity. Based on this fact, we showed that, for the ? > 0 case, the Lorentzian theory can be partially reduced, thanks to a suitable gauge fixing, to a Chern–Simons theory with compact gauge group SU(2). Then we revised already known loop quantization of Chern–Simons theory for the case of a space with the topology of a cylinder. Finally we construct a quantum observable which, despite having a not trivial spectrum at the quantum level, it corresponds to a classical quantity identically null.
A Supercondutividade e o Formalismo de Nambu
(Universidade Federal do Espírito Santo, 2013-04-26) Eleutério, Fernando Henrique Santos; Belich Junior, Humberto; Hernaski, Carlos André; Passos, Carlos Augusto Cardoso; Orlando, Marcos Tadeu DAzeredo; Belich Junior, Humberto
In this paper we presented a study of the superconducting phase transition, which outlines the thermodynamics involved in a description of the mean field (order parameter). The Ginzburg-Landau model uses an order-parameter-dependent functional to describe the thermodynamic phase transition involving. The free energy function given in terms of this parameter provides the essential elements to extract the behavior of entropy, specific heat, and the number of superelectrons. However, this model does not explain how the pair of electrons can overcome the Coulomb repulsion energy and stabilize. Using the formalism of Nambu it is possible to expose how this occurs. On the other hand, the superconducting ceramics (eg, Hg, Re-1223, studied at the Group of Applied Physics UFES) consist of grains that form an interpenetrating set Josephson microjunction (the "weak-link"). Thus one can use the concepts in this type of join to present the microscopic physical processes involved in high-temperature superconductors. Finally, in this thesis one describes the formation of this type of joint.
A Theoretical Study of Samarium Hexaboride (SmB6) as a Possible Candidate for Light Dark Matter (LDM) direct detection
(Universidade Federal do Espírito Santo, 2023-12-22) Loyola, Thiago Dias; Paz, Wendel Silva; http://lattes.cnpq.br/8332147920469110; http://lattes.cnpq.br/3435636351009428; Belich Junior, Humberto; http://lattes.cnpq.br/3879935393431243; Spalenza, Wesley; Freitas, Tales Costa de
The mystery surrounding the existence of dark matter, prompted by a substantial mismatch between theoretical predictions and experimental observations in galaxies and galaxy clusters, remains a formidable mystery awaiting resolution. A pivotal aspect of unraveling this mystery lies in its detection. It is crucial to note that this persistent enigma has led us to the formulation of different models detailing its composition and interactions with ordinary matter. In the scope of the present study, our focus centers on Light Dark Matter (LDM). Furthermore, we operate under the assumption that its interactions occur through a dark photon that is transformed into a visible photon and absorbed during the interaction process. In the subsequent discussion on the direct detection of new particles using a target, our primary objective revolves around quantifying parameters intricately linked to the interaction between the particle and the target. It is still crucial to emphasize that the nature of the target may lead us down distinct avenues within the realm of physics since molecule targets and crystal targets are analyzed by different approximations, boundary conditions, and symmetries. However, the quest for heightened interaction probability steers us inevitably into the domain of Material Science, where the size of the target becomes a pivotal determinant of success. In the context of the light-dark matter, the material selected must meet some specific criteria, including scalability, band gap, Fermi velocity, and topology, and these stand for the points that will guide us through all subsequent development up to the positive conclusion concerning the use of Samarium Hexaboride (SmB6) as a target in this detection process.
Abordagem relativística para o átomo de hidrogênio em um cenário de comprimento mínimo introduzido pela álgebra Lorentz-covariante de Quesne-Tkachuk
(Universidade Federal do Espírito Santo, 2013-11-29) Francisco, Ronald Oliveira; Fabris, Júlio César; Nogueira, José Alexandre; Helayel Neto, José Abdalla; Bazeia Filho, Dionisio; Rodrigues, Davi Cabral
One of the reasons for gravity can not be included in the standard model is its non-renormalizability. Almost all the proposals for the quantization of gravity leads to existence of a minimal length which acts as a natural regulator. That effect suggests a generalized uncertaintly relations between position and momentum operators what results in a modified commutation relation between these operators, and thus changing the whole structure of quantum mechanics. In this work we calculate the magnitude of this minimum length through the energy of the ground state of the hydrogen atom in Dirac’s theory, based on the Quesne-Tkachuck commutation relation. Comparing with experimental data, we obtained the value of the minimum length is orders of magnitude less than or equal to 10-20m
Algoritmos de amostragem por rejeição dinâmica aplicados a busca descentralizada em redes de mundo pequeno com topologia fractal
(Universidade Federal do Espírito Santo, 2021-11-23) Amaral, Leonardo Aguiar do; Belich Junior, Humberto; https://orcid.org/0000-0002-8795-1735; http://lattes.cnpq.br/3879935393431243; https://orcid.org/0000-0001-8951-4304; http://lattes.cnpq.br/3747190706760201; Soares, Thales Costa; https://orcid.org/0000-0001-8734-6642; http://lattes.cnpq.br/4676057702132305; Canal Neto, Antônio; https://orcid.org/0000-0002-8556-618X; http://lattes.cnpq.br/9283775492064031; Spalenza, Wesley; https://orcid.org/0000-0001-9644-3938; http://lattes.cnpq.br/2687428810786056; Mota, Vinicius Candido; https://orcid.org/0000000183680803; http://lattes.cnpq.br/4038237972209273; Favarato, Cássio Cecato; https://orcid.org/0000-0002-7599-595X; http://lattes.cnpq.br/0364649580177297
In this research, we study Kleinberg’s navigation in small-world networks using the dynamic rejection sampling algorithm proposed by Mathieu and Comte. Unlike conventional techniques, this approach dispenses with the use of periodic boundary conditions that deform the lattice and convert it into a toroid. Instead, acceptance masks are used superimposed on the studied square network to offer an additional acceptance criterion for the acquisition of long-range links, without violating the fundamental precepts that govern the statistical distribution of these connections, resulting in a drastic drop in the complexity of the algorithm. This work aims to extend Mathieu and Comte’s approach to networks with fractal topology (Sierpinski’s Square), this is done through the development of an auxiliary computational routine (fractal_search) which makes fractal geometry detectable to acceptance masks. This is a step of great relevance for the entire process regarding the complexity of the algorithm since the knowledge accumulated in the literature in the last decade indicates that the emergence of routing in fractal networks requires that they have extremely large sizes. Our routine was designed to operate recursively and harmonically with fractal self-similarity, which guarantees a performance compatible with the tasks it will perform during the simulation. The approach adopted in conducting this work was consistent with the forecasts and results already consolidated and published in journals specialized in the field of network science, such as the existence of a clustering exponent that minimizes the delivery time, when it assumes values identical to the dimension of the analyzed network (αmin = df ), besides the appearance of the proportionality of the delivery time with the logarithm of the network size (T ∼ ln2L). It was also demonstrated that the number of realizations (R), used to compose the sampling space of the statistical analysis of the simulation, and the network size (L), have interdependence and have a significant impact on the processing time. Finally, we performed a performance test using the execution time as a comparative parameter, which demonstrated the superiority of the proposed method compared to traditional methods.
Algumas considerações sobre conjuntos de bases para cálculos de propriedades elétricas
(Universidade Federal do Espírito Santo, 2009-10-13) Arruda, Priscilla Mendes; Canal Neto, Antônio; Muniz, Eduardo Perini; Franco, Mauro Lúcio; Jorge, Francisco Elias; Canal Neto, Antônio
Recently, segmented contracted basis sets of double, triple, and quadruple zeta valence quality plus polarization functions (XZP, X=D, T, and Q, respectively) for the atoms from H to Ar were reported. In this work, with the objective of having a better description of polarizabilities, the QZP set was augmented with diffuse (s and p symmetries) and polarization (p, d, f, and g symmetries) functions that were chosen to maximize the mean dipole polarizability at the UHF and UMP2 levels, respectively. At the HF and B3LYP levels of theory, electric dipole moment and static polarizability for a sample of molecules were evaluated. Comparison with experimental data and results obtained with a similar size basis set, whose diffuse functions were optimized for the ground state energy of the anion, was done
Análise Hamiltoniana de Teorias de Gravitação pela Abordagem Simplética.
(Universidade Federal do Espírito Santo, 2021-06-17) Junior, Mariniel Souza Galvao; Rodrigues, Davi Cabral; https://orcid.org/0000000316835443; http://lattes.cnpq.br/5465449494182034; https://orcid.org/; http://lattes.cnpq.br/; Fabris, Julio Cesar; https://orcid.org/000000018880107X; http://lattes.cnpq.br/5193649615872035; Neto, Nelson Pinto; https://orcid.org/; http://lattes.cnpq.br/6196081550581346; Junior, Roldao da Rocha; https://orcid.org/; http://lattes.cnpq.br/; Guimaraes, Marcelo Santos; Sotkov, Galen Mihaylov; http://lattes.cnpq.br/6372536076880230
We show how to systematically apply the Faddeev-Jackiw symplectic method to General Relativity (GR), GR extensions and tetrad gravity coupled to fermions. We also develop a completely symplectic analysis for the computing of gauge symmetries and apply the
Análise perturbativa em modelos cosmológicos fantasmas
(Universidade Federal do Espírito Santo, 2010-02-19) Jardim, Deborah Faragó; Fabris, Júlio César; Tonini, Eduardo Valentino; Dito, Giuseppe; Silva, Saulo Carneiro de Souza; Gonçalves, Sergio Vitorino de Borba; Zimdahl, Winfried Ernst Wilhelm
Dark energy models have became extensively studied in recent years. Earlier proposals have emerged this century to describe the Universe by means of a fluid whose equation of state was breaking with the paradigm imposed by the standard cosmology. Fluid of this kind require to violate some energy conditions and have a very peculiar behavior, denominated for this reason "phantom fluid". This work investigates the structures formation through the study of cosmological perturbations in Universe which scenario is the phantom cosmology. They have proposed two models, the first them by solving the perturbed equations for scalar modes, using a hydrodynamic and fields representation for the fluid and then making the asymptotic behavior analysis. The second model is a composite of two fluids, one component of pressureless matter and another with negative pressure, represented by a self-interacting scalar field . In this case, the solution was obtained by numerical calculation. Results were confronted with the observational data and it showed models phantom of this nature are quite possible and its open a new window of research
Análise quantitativa dos teores de lignina e celulose em materiais de biomassa por RMN de 13C no estado sólido
(Universidade Federal do Espírito Santo, 2015-06-19) Cipriano, Daniel Fernandes; Freitas, Jair Carlos Checon de; Azevedo, Eduardo Ribeiro de; Alfonso, Jorge Luis Gonzalez; Schettino Junior, Miguel Ângelo
This work is dedicated to the study and development of an experimental method that allows the use of solid state 13C nuclear magnetic resonance (NMR) spectroscopy, with cross polarization (CP) and magic angle spinning (MAS), to determine the lignin and cellulose contents in lignocellulosic materials. The validity of the method was tested on di erent biomass materials by comparison to the corresponding contents obtained by the Klason method. The method was also used in a comparative study of sugarcane bagasse samples subjected to acid treatments for di erent times. For the development of the method, standard samples of cellulose and lignin as well as mixtures of both materials in known proportions were analyzed by 13C CP/MAS NMR. After acquiring the NMR spectra, graphs were constructed relating the intensity of selected spectral regions to the mass of the component responsible for that intensity. It was observed that the lignin contents of most of the analyzed lignocellulosic materials agreed well with the contents determined directly by chemical analysis. On the other hand, the cellulose contents were not correctly predicted, possibly due to the overlap of hemicellulose and cellulose signals in the NMR spectra. Regarding the acid-treated sugarcane bagasse samples, an increase in the lignin contents of the samples subjected to longer acid treatments was observed, concomitantly with the increase in the fraction of structurally ordered cellulose.
Análise termobarométrica aplicada à decomposição do oxalato de cálcio hidratado.
(Universidade Federal do Espírito Santo, 2017-04-10) Cevolani, Messias Bicalho; Cunha, Alfredo Gonçalves; Oliveira, José Roberto de; Alfonso, Jorge Luis Gonzales; Bueno, Thiago Eduardo Pedreira
This work is concerned with the characterization of the Thermobarometric Analysis technique applied to the decomposition of Calcium Oxalate Monohydrate (CaC2O4.H2O). This decomposition occurs in three steps with three different gaseous products. This is a technique that makes it possible to obtain direct measurements of temperature and pressure simultaneously during the heat treatment process, this was done in constant volume inside a quartz bulb. Consequently, it was possible to identify thermodynamic parameters of the phase transition and verify the energy conservation quantity such as enthalpy, entropy and Gibbs free energy through the pressure and temperature measurements. The samples were decomposed by varying systematically the initial experimental conditions such as mass, heating rate, heat treatment final temperature and initial pressure. The present results allowed the identification and description of several physical phenomena related to the compound decomposition process. It was possible to identify that an increase in pressure displaced the of the first and third steps transition temperature to higher levels. In the second transition step, the increase in pressure caused the transition temperature to move to lower levels. It has been observed a proportional relationship between mass and the pressure for each transition steps. Therefore, the mass variation also displaces the transition temperatures of the three decomposition steps. Analyzing the initial pressures of each experiment, it was possible to identify a small amounts of H2O, such as humidity, in many samples and in the quartz bulb dedicated to the process. The amount of H2O relative to this humidity is exponential in relation to the initial pressure used to close the ampoules. In this work, it also discovered some limitations of the Thermobarometric Analysis technique when applied to the decomposition of CaC2O4.H2O. By this way, the temperature range limited to 800°C was identified as the most adequate for the experiments of this work.
Anisotropia unidirecional anômala induzida em bicamadas NiFe/IrMn
(Universidade Federal do Espírito Santo, 2015-08-31) Krohling, Alisson Carlos; Nascimento, Valberto Pedruzzi; Bueno, Thiago Eduardo Pedreira; Pereira, Rodrigo Dias; Moscon, Paulo Sérgio; Caetano, Edson Passamani
In this Master dissertation, anomalous unidirectional anisotropy and Exchange Bias effect on multilayer Si(100)/Ta(3nm)/NiFe(3nm)/IrMn(7nm)/Ta(1nm), prepared at room temperature by DC Sputtering, were systematically studied by X-ray difraction and magnetization measurements. In particular, as-prepared and heat at 600 K samples were investigated by X-ray diffraction in low (reflectivity) and high (conventional) angle geometries to characterize the bulk and interface film structural properties. Magnetization measurements, performed in a broad temperature range (300 - 600 K), were done to study magnetic properties of these two samples (as-prepared and annealed). Room temperature M(H) curves have shown a horizontal loop shift effect for the as-prepared sample. This effect was here associated with an anomalous unidirectional anisotropy induced during the sample preparation procedure (intrinsic properties), i. e., an effect that is present before the field cooling process needed to induce the Exchange bias effect. This anomalous behavior, observed in as-prepared Si(100)/Ta(3nm)/NiFe(3nm)/IrMn(7nm)/Ta(1nm) film, may be explained assuming an interface interduffusion effect without structural change at the Ta/NiFe interface. This interdiffusion effect, that occurs during the sample preparation, favors a magnetically harder NiFeTa phase (when compared with the NiFe phase); consequently there will be for the as-prepared film two magnetic contributions: (i) a soft NiFe phase magnetically coupled to the IrMn layer and that will be responsible for the observed horizontal loop shift effect (anomalous unidirectional anisotropy) and (ii) a harder NiFeTa phase, which is not influenced by the anomalous unidirectional anisotropy, but that have their magnetic moments rotated incoherently with those spins of the NiFe layer. The combination of low and high temperatures magnetic and structural data indicates that it is possible to remove this anomalous anisotropy when the sample is heated around the interval 520-570 K, which is the blocking temperature range of this effect. However, the high temperature data suggest an enhancement of the interface atomic interdiffusions Ta/NiFe and NiFe/IrMn, leading to a sample degradation as well as formation of a NiFeIrMnTa phase, with a completely disappearance of the NiFe contribution.
Aprendizagem de máquina aplicada a métodos de classificação de supernovas
(Universidade Federal do Espírito Santo, 2018-09-06) Silva, Rodrigo Duarte; Casarini, Luciano; Marra, Valerio; Fabris, Júlio César; Reis, Ribamar Rondon de Rezende dos
Future observational research with investments, telescopes and technologies never before seen, are being proposed in an attempt to unravel the mysteries of the Universe. In our work, we provide an overview of this scenario, with special attention to the classification of supernovae that will be done by LSST (Large Synoptic Survey Telescope) from 2022. Initially, we introduce the physics that involve the Supernova event and its observation, with the objective of treating the problem of photometric classification of supernovae. We provide important references in the use of different machine learning and neural networks for this purpose. We include results from the use of some of the computational methods and the theory behind them, highlighting their potentialities and vunerabilities. Machine learning methods may involve supervision or not. We aim to describe the application of these powerful tools in the analysis of observational data and verify unexpected results.
Aproximação de campo fraco e ondas gravitacionais
(Universidade Federal do Espírito Santo, 2019-10-29) Santos, Josianne Catarina de Sousa Rodrigues dos; Belich Junior, Humberto ; https://orcid.org/; http://lattes.cnpq.br/3879935393431243; https://orcid.org/0000000161628254; http://lattes.cnpq.br/4791740315602454; Leal, Fernando Jose Lira; https://orcid.org/0000-0001-8932-6776; http://lattes.cnpq.br/2197913737177329; Martins, Gabriel Luchini; https://orcid.org/000-0001-6627-3034; http://lattes.cnpq.br/3344738411070832; Neto, Jose Abdalla Helayel; https://orcid.org/0000-0001-8310-518X; http://lattes.cnpq.br/4044332658989430
In 1915, the general relativity theory (TRG) was proposed by Albert Einstein. This theory is a generalization of the relativity principle of motion for systems where include gravitatio nal field and is based on a three postulates. For construction of the TRG, is required to use mathematical tools of curved space, no longer restricted to the Euclidean space. A way to do this is through algebra tensor, however, it is in the topology study that this study is most com plete. After the construction of TRG, Einstein predicted the existence of gravitational waves, it was finally detected on September 14, 2015, in the USA, one hundred years after the predict. This waves has specific characteristics, but with some similarities with electromagnetic waves. Therefore, this work show the construction of this theory, and the motivation for this was the detected of the gravitational waves in 2015, and this work finishing with the interaction the gra vitational waves with the matter and its polarization
As supernovas tipo Ia e a cosmologia
(Universidade Federal do Espírito Santo, 2010-08-09) Oliveira, Paulo Louzada Castro de; Fabris, Júlio César; Ricaldi, William Santiago Hipolito; Alcaniz, Jailson Souza de
This dissertation is dedicated to the investigation on the nature of the dark matter and dark energy in the Universe through the technique that uses the observations of explosions os supernovae type Ia as indicators of distances, used at the end of the last century to detect the acelerated expansion of the Universe. Since then some projects dedicated to observation of supernovae where executed and published their results, which are used here to estimate parameters and compare cosmological models. The objective of this work is to study the power of the test based on the distances to supernovae and its response to different cosmological models and free parameters. To begin with we review the standard model of Cosmology and the evidences that suport the existance of dark matter and dark energy, followed by a study on the supernovae itself and its various observational and astrophysical aspects that allow the construction of the magnitude calibration techniques and the estimatives of its distances. Before moving on to the cosmological analyses we introduce the appropriate tool which is the bayesian statistics, studied here only in its basic tools and aplications. At last we aply these tools to the supernovae data sets available in the literature know as the Gold, SNLS, Essence and Constitution, to study some cosmological models, beginning with the concordance ?CDM model and the ?CDM parametrization that tests the supposition that ?X = -1 for the dark energy. After that we test two dynamical vaccum energy ?(t) models and a special case of the quartessence Generalized Chaplygin Gas model. The results show that when used alone the supernovae data sets leeds to quite less expressive results when compared to the literature where they are used together with other evidences. And also two of the data sets including the most up to date show unexpected irregularities that point to the existance of still uncontrolled effects on the magnitude calibration techniques. Both results show that the cosmological test based on supernovae data will go through another significant improvement on its quality in the near future.
Bases gaussianas geradas com os métodos Monte Carlo Simulated Annealing e Particle Swarm Optimization.
(Universidade Federal do Espírito Santo, 2017-10-03) Reis, Thiago Mello dos; Alfonso, Jorge Luis Gonzalez; Caetano, Edson Passamani; Continentino, Mucio Amado; Nascimento, Valberto Pedruzzi; Macedo, Waldemar Augusto de Almeida
The Monte Carlo Simulated Annealing and Particle Swarm Optimization methods were used to generate adapted Gaussian basis set for the atoms from H to Ar, in the ground state. A study about the e ciency and the reliability of each method was performed. In order to check the reliability of the proposed methods, we perform an speci c study considering a training set of 15 atoms, namely: N, Mg, Al, Cl, T i, N i, Br, Sr, Ru, P d, Sb, Cs, Ir, Tl, At. First of all, the Improved Generator Coordinate Hartree-Fock Method was applied to generate adapted basis which was used as start point to generate new Gaussian basis sets. After that, the Monte Carlo Simulated Annealing and Particle Swarm Optimization methods were developed from parallel studies, however following the same procedure so as we could have the possibility to compare them. Previously applying of the developed methods we perform some calibrations in order to de ne the values of the parameters of the algorithms; we perform studies about annealing schedules (for the Monte Carlo Simulated Annealing method), the total of swarm's particle (for the Particle Swarm Optimization method), and the total of steps for each algorithm. After the calibration procedure, both methods were applied, with the variational principle, to the Hartree-Fock wave function to give us the fully optimized Gaussian basis sets. Next, the basis sets were contracted by considering the lowest total energy loss, prioritizing the contraction of the most internal exponents. The last two steps of our procedure were the addition of polarized and di use functions, respectively. These procedures were performed by using the methods which we developed in this work through calculations to the MP2 level. The basis sets that have been generated in this work were used in some atomic and molecular calculations; we compare such results with relevant results from literature. We veri ed that, if we consider the same computational e ciency for both Monte Carlo Simulated Annealing and Particle Swarm Optimization methods, there is a vi small di erence between them as regards the accuracy, so that by using the Monte Carlo Simulated Annealing method we obtain best results. When we compare the results of this work with those from literature we note similar results for the properties that were studied, however the proposed methods in this work are more e cient, and we can de ne a single total numbers of steps for the algorithms even though we are treating with di erent atomic systems. In addition, we verify that the proposed methods in this work are more accurate than other similar methods presented in the literature, in the task of nding the global minima of the uncontracted basis sets to HF level of theory. It will be necessary to perform additional studies to check the real relationship between the accuracy of the methods. We do not verify the in uence of several parameters of the Particle Swarm Optimization algorithm in this work. The fact that the developed methods in this work have been constructed through Double Zeta basis does not prevent them to be used for larger basis sets, the two methods are able to be applied to generate Gaussian basis sets in the atomic environment for Gaussian basis sets with di erent qualities

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