O nosso departamento congrega docente que atuam em diversas áreas de pesquisa, notadamente Ciências dos Materiais, Física Computacional, Astrofísica, Cosmologia e Gravitação, Big Bang, Matéria Escura, Energia Escura, Relatividade Geral e teorias gravitacionais alternativas.. Temos um curso de bacharelado em física com ênfases em ciências dos materiais e física básica e um curso de Licenciatura em Física. Atuamos nos cursos de Pós-graduação em Física de Materiais (FIMAT), Rede Temática em Engenharia de Materiais - REDEMAT, Mestrado Profissional em Estudo de Ciência (MPEC) e outros programas em colaboração com outros departamentos da UFOP. 

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Roteiros de Práticas para FIS105

Roteiros de Práticas para FIS105 – Fundamentos de Física Experimental

PET Fisica - UFOP




Publicações Recentes do Departamento de Física

Daouda M, Fabris JC, Oliveira AM, Smirnov F, Velten HES. Nonconservative traceless type gravity. International Journal of Modern Physics D [Internet]. 2019;28 (15) :1950175. Publisher's VersionAbstract
Extensions of the gravity theory in order to obtain traceless field equations have been widely considered in the literature. The leading example of such class of theories is the unimodular gravity, but there are other possibilities like the mimetic gravity and the Rastall gravity with a coupling parameter λ = 1/2. The unimodular gravity proposal is a very interesting approach in order to address the cosmological constant problem. When coupled to matter, such theories may imply that the energy–momentum tensor is not divergence free anymore. In this paper, a unimodular type theory will be developed by evading the conservation T;μμν = 0. The cosmological consequences of the later, both at background as well as for scalar and tensor perturbations, are explored. Possible further extensions of this approach are discussed as well as its connection with the traditional unimodular gravity.
Barboza APM, Souza ACR, Matos MJS, Brant JC, Barbosa TC, Chacham H, Mazzoni MSC, Neves BRA. Graphene/h-BN heterostructures under pressure: From van der Waals to covalent. Carbon [Internet]. 2019;155 :108 - 113. Publisher's VersionAbstract
Scanning probe microscopy and ab initio calculations reveal modifications on the electronic and structural properties of graphene/h-BN heterostructures induced by compression. Using AFM and EFM techniques, with charge injection being made in the heterostructures at different pressures, the charge injection efficiency monotonically decreases with increasing pressure for monolayer-graphene (MLG)+BN heterostructures, indicative of a conductor-insulator electronic transition. Bilayer-graphene (BLG)+BN and trilayer-graphene (TLG)+BN heterostructures show a non-monotonic behavior of charge injection versus pressure, indicative of competing electronic structure modifications. First-principle calculations of these systems indicate a pressure-induced van der Waals-to-covalent interlayer transition, where such interlayer covalent binding, in the presence of water molecules, results in a disordered insulating structure for the MLG + BN case, while it leads to an ordered conducting structure for both BLG + BN and TLG + BN heterostructures. These opposing effects may have a strong influence on graphene/h-BN-based electronic devices and their physics under pressurized environments.
Brando G, Falciano FT, Linder EV, Velten HES. Modified gravity away from a $\upLambda$CDM background. Journal of Cosmology and Astroparticle Physics [Internet]. 2019;2019 (11) :018–018. Publisher's VersionAbstract
Within the effective field theory approach to cosmic acceleration, the background expansion can be specified separately from the gravitational modifications. We explore the impact of modified gravity in a background different from a cosmological constant plus cold dark matter (ΛCDM) on the stability and cosmological observables, including covariance between gravity and expansion parameters. In No Slip Gravity the more general background allows more gravitational freedom, including both positive and negative Planck mass running. We examine the effects on cosmic structure growth, as well as showing that a viable positive integrated Sachs-Wolfe effect crosscorrelation easily arises from this modified gravity theory. Using current data we constrain parameters with a Monte Carlo analysis, finding a bound on the running |αM,max|≲ 0.03 (95% CL) for the adopted form at all cosmic times. We provide the modified hi_class code publicly on GitHub, now enabling computation and inclusion of the redshift space distortion observable fσ8 as well as the No Slip Gravity modifications.
Lourenço GM, Keesen F, Fagundes R, Luna P, Silva AC, Ribeiro SP, Arashiro E. Recruitment and entropy decrease during trail formation by foraging ants. Insectes Sociaux [Internet]. 2019. Publisher's VersionAbstract
Social insects utilise a complex spatial orientation system mediated by chemical signals. This study investigated how the foraging behaviour of ants (Dorymyrmex thoracicus) varies depending on the quantity of an available resource using a field experiment. Further, we demonstrated computationally that ant displacement is compatible with a model based on pheromone deposition. Our experiment tested how the resource size (large or small) and availability (one or two simultaneous patches) of resources offered influence the number of recruited ants (traffic flow) and the speed of traffic flow both moving towards a resource and returning to the colony. The results showed that the returning flow was higher than the going flow independent of resource. The traffic flow towards a single resource was higher than the flow for either of two simultaneous resources patches offered; thus, multiple resources sources split the flow, regardless of the fact that resource size did not affect foraging choices. Our results indicated that the ants used an orientation mechanism that can be reproduced by a theoretical computer model. With our model, we showed that initially, the displacement of ants followed no clearly detectable pattern. However, with increasing levels of ant recruitment and consequent pheromone deposition on the most used trails, returning displacement revealed the formation of shorter and more organised trails. The model revealed key transition between periods of order and disorder that continued until the flow of information reached an organised state (Shannon entropy). This study highlights an exceptional mechanism of foraging optimisation in eusocial insects.
Boriero D, Schwarz DJ, Velten H. Flavour Composition and Entropy Increase of Cosmological Neutrinos After Decoherence. Universe [Internet]. 2019;5 (10). Publisher's VersionAbstract
We propose that gravitational interactions of cosmic neutrinos with the statistically homogeneous and isotropic fluctuations of space-time lead to decoherence. This working hypothesis, which we describe by means of a Lindblad operator, is applied to the system of two- and three-flavour neutrinos undergoing vacuum oscillations and the consequences are investigated. As a result of this decoherence we find that the neutrino entropy would increase as a function of initial spectral distortions, mixing angles and charge-parity (CP)-violation phase. Subsequently we discuss the chances to discover such an increase observationally (in principle). We also present the expected flavour composition of the cosmic neutrino background after decoherence is completed. The physics of two- or three-flavour oscillation of cosmological neutrinos resembles in many aspects two- or three-level systems in atomic clocks, which were recently proposed by Weinberg for the study of decoherence phenomena.
Calheiro DS, Bianchi RF. Tuning the detection limit in hybrid organic-inorganic materials for improving electrical performance of sensing devices. Sensors and Actuators A: Physical [Internet]. 2019;298 :111480. Publisher's VersionAbstract
Research in hybrid electronics has included advances in materials, devices and architectures. However, in practice, controversy still exists on some details which limit hybrid materials to high-performance applications, such as processing–structure–design–property relations. This paper describes a practical approach to enhancing the sensing performance of a prototype ammonia gas sensor based on electrical conductivity changes, percolation theory and current limitation to a semiconducting polymer-metal oxide medium. This device is based on fully-gravure printed polyaniline/indium - tin oxide nanocomposites, Pani100−xITOx [0 ≤ x≤ 100% (wt/wt)], layers on a freestanding high-density polyethylene substrate. We find that the electrical current of the device decreases and tends to saturate as the gas concentration increases, and the value of this electrical current limit (IL) depends on x: the higher the value of x, the smaller the IL, when the current that flows through the electronic device was dominated by the ITO-nanoparticle filled PAni, which increase the concentration of hopping carriers and contribute to the desired electrical response of a heterogeneous gas sensor. In this regime, we find a good linear relationship between x and ammonia concentration. These findings suggest new directions for future research on the development and investigation of organic-inorganic devices in which the electrical current variation is desired for enhanced sensitivity and stability of hybrid sensors.

Publicações de Livros do Departamento de Física

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