High-Energy Physics Seminars: “Hydrodynamics with polarization”

Using the Lagrangian hydrodynamic approach [1] we derive the ideal hydrodynamic limit of a fluid with a net polarization of the microscopic degrees of freedom. We discuss the relevance of this dynamics in the light of the experimental study of Hadron (Lambda and vector meson) polarization and other spin-dependent observables in heavy ion collisions, and conclude that our approach is the first term in an effective theory expansion appropriate to study these phenomena quantitatively.

[1] D.Montenegro, G.Torrieri, PRD, in press, arXiv:1604.05291

Hydrodynamics with polarization

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IFSC OSA Student Chapter: “Professor Eric Van Stryland seminars”

We from IFSC OSA Student Chapter have the honour to receive Prof. Eric Van Stryland as part of the Travelling Lecturer program of the Optical Society. Prof. Stryland will give two seminars, a brief one about the history of The Optical Society and other pointing out fundamental aspects of his cutting-edge research. You are welcome to attend both seminars that will be held at Sala F-210 (Administration building) at 2 p.m of November 11th. Take a look below for further information about Prof. Stryland and the seminars.

History of The Optical Society (OSA)

I’ll give a brief introduction of how OSA began in 1916 and how it has turned into an international professional home for nearly 20,000 scientists and engineers. Its offerings are highly respected international refereed journals along with international conferences on optics and photonics. However, it is also a professional network for students and professionals to interact, develop careers in optics and photonics, and much more. It is my professional home and should become yours.

Nonlinear spectroscopy: absorption and refraction

At high optical irradiance of short pulse lasers, the absorption and refraction of materials changes temporarily. We have been developing nonlinear spectroscopic tools for measuring these changes of nonlinear absorption (NLA) and nonlinear refraction (NLR). The tools include Z-scan that separately yields the sign and magnitude of both NLA and NLR, pump-probe for the dynamics of NLA, and our newly developed Beam-Deflection technique that gives the dynamics of NLR. This last technique is so sensitive that it can measure the nonlinear refraction of air (λ/20,000 induced phase change). I will also discuss the interesting and intuitive relations between NLR and NLA determined by causality (nonlinear Kramers-Kronig relations). This leads to a discussion of nondegenerate nonlinearities, e.g. 2-photon absorption (2PA) with two different energy photons. We find orders of magnitude enhancement of 2PA for photon energy rations of ~10. We then utilize these nonlinearities for devices including gated IR detection with uncooled wide-gap semiconductors for 3D LIDAR and the possibility of a 2-photon laser.

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“Measurement of leptonic cosmic rays with AMS-02, interpretation in terms of dark matter and pulsar”

Over the last two decades, there has been a strong interest in the cosmic ray positron fraction which exhibit an excess of high energy positrons whose origin is still highly uncertain. The Alpha Magnetic Spectrometer (AMS-02) is a general purpose high-energy particle physics detector operational on the International Space Station since May 2011. During its unique long duration mission AMS-02 is collecting large amount of data to study the behaviour of cosmic ray electrons and positrons with unprecedented precision. The latest measurements of positron fraction, positron flux and electron flux with AMS-02 will benpresented. The interpretation of the positron excess in terms of pulsar or dark matter will be presented in this talk.

Filosofísica: “Mais um breve passeio pela Filosofia contemporânea da Matemática”

Nesse seminário, o membro do grupo de estudos Uirá Matos prosseguirá nos guiando em incursão pelos territórios da Filosofia da Matemática, em uma continuação do seu panorama das mais atuais (ou nem tanto) questões do campo.

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Filosofísica: “Os ‘raios N’ de René Blondlot: uma anomalia (na história) da ciência”

O físico francês René Prospet Blondlot (1849-1930) fez grandes trabalhos. Seus estudos para medir a velocidade de ondas hertzianas (eletromagnéticas) são bastante originais, obtendo o valor de 298.000 Km/s experimentalmente. René Blondlot ganhou vários prêmios da Academia de Ciência de Paris.

No começo do século XX o nosso personagem rincipal começa a estudar as características dos raios X, recém-descobertos, e em 1903 divulga seus achados sobre uma nova radiação, os “raios N”. Essa descoberta fez sucesso, uma nova área da física nasceu, houve trabalhos aplicando os raios N ao estudo do sistema nervoso. Em 1905 a maioria dos físicos, incluindo revistas científicas, concluiu que essa radiação não existia.

Os argumentos contrários à existência dessa radiação se baseavam na suposição de que René e outros viam o que queriam ver, por autossugestão. O que é esquecido é que Blondlot respondeu a essas críticas seriamente, com evidências fotográficas. Mesmo assim o assunto morreu. Essa apresentação tem por objetivo adentrar essa rica história e analisar os argumentos e evidências da época. Há ainda muitos mistérios sobre esse estranho episódio.

High-Energy Physics: “Scattering Amplitudes: from theoretical considerations to LHC applications”

The Feynman rules appear as a simple way to calculate scattering amplitudes, however some complications appear if the multiplicity of particles is large. For example, in the 2 to 2 scattering of gluons there are only 4 Feynman diagrams but if we add two extra gluons it grows to 220 diagrams. In the 80’s Stephen Parke and Tomasz Taylor found an incredible way to simplify the calculation of some classes of n-gluons scattering amplitudes based on helicity arguments. Since then, a lot of progress has been made on improving the amplitude techniques and on the understanding of the S-matrix physics. After a review of the spinor helicity formalism and some well known results based on it, I will discuss how we can use the helicity structure of scattering amplitudes in the SM and in the context of an effective Lagrangian description of BSM dynamics. The analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 to 2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. This have a big impact on how we should perform the EFT analysis and where we should search for new physics.

Seminários do Grupo de Óptica: “Optical spectroscopy and microscopy studies of biological objects”

Spectroscopic and microscopic techniques allow analysis of various aspects of biological systems on molecular level. One of the common problems of such studies is overlapping of absorption or fluorescence spectra of biological molecules of interest. Several examples of how to separate them are shown for in vitro and in vivo systems. These examples include analysis of competitive binding of two molecules (anticancer drugs, mutagens and biologically active substances) to nucleic acids via absorption spectroscopy, separation of fluorescence spectra of Photosystems via time-resolved fluorescence spectroscopy and microscopy and analysis of Forster Resonance Energy Transfer (FRET) between voltage-sensitive fluorescence proteins. As a result constants of binding of anticancer drugs and mutagens to nucleic acids are determined for molecules that absorb light in the same region with nucleic acids. Also composition and ratio of Photosystems is determined in leaves, which opens room for non-invasive “express” analysis of these parameters in plants, allowing determination of optimal growing conditions and presence of diseases. FRET studies of voltage sensitive fluorescent protein help to figure out the mechanism of its action and improve its functionality. In general, it is shown that number of different approaches can be used to analyze overlapping absorption and fluorescence spectra of biological molecules on different levels of organization in vitro and in vivo.

High-Energy Physics Seminars: “Vertex Functions and Bound States in Strongly Interacting Theories”

Protons and neutrons, the particles which make up the nuclei of atoms, are comprised of tiny constituents called quarks. Quantum chromodynamics (QCD) is a field theory which describes the so-called strong “colour” force, mediated by gluons, which binds the quarks together and is responsible for formation of nucleons and other objects, collectively known as hadrons. While there is ample experimental evidence that this theory is correct, there are certain phenomena related to hadrons which are not yet fully understood within the QCD framework. We attempt to elucidate some of these issues by studying QCD and similar models by means of the Dyson-Schwinger and Bethe-Salpeter (DS/BS) functional formalism. This approach allows one to work with the basic degrees of freedom of QCD, the quarks and gluons (which are not directly detectable in experiments, being eternally bound within hadrons), while at the same time giving access to physical observables like hadron masses and decay constants. We briefly discuss the main ideas behind the DS/BS framework, and give examples of its applications through an investigation of one of the fundamental interaction vertices in QCD, as well as a calculation of light hadron masses in a model similar to chromodynamics. Our findings help in building towards a better understanding of not just QCD but strongly-interacting theories in general, which is important since some of these templates play an important role in other areas of high-energy particle physics.

Seminário: “Recent advances in polymers from renewable resources”

 Research and development related to polymers from renewable resources have witnessed a spectacular development from the beginning of this millennium, with a progressively deeper and wider involvement of both academia and industry. This lecture aims at providing a succinct “state of the art” of this exciting field through a number of examples of recent advances, including contributions from my research groups. Two main approaches are discussed, namely: The chemical modification of natural polymers. This topic covers the synthesis and characterization of novel materials and composites arising from the surface, in-depth and bulk transformation of celulose fibers, including nanofibers, chitosan, starch, lignin and natural rubber. The synthesis and polymerization of monomers derived from renewable resources. The variety of such monomers and macromonomers has already reached a remarkably wide spectrum and is increasing incessantly. The examples provided in this context deal with small molecules derived from sugars and polysaccharides, lignin, and larger structures derived from vegetable oils. Particular emphasis is placed on furan monomers and furan chemistry, which provide a new class of polymer chemistry, including the application of structure-specific mechanisms like the Diels-Alder click reaction. Additionally, the peculiar properties of some of these new macromolecular materials, such as poly(lactic acid), other polyesters, polyamides and polyurethanes, are highlighted to show, among other features, their unique applications, e.g. recyclability and self-mendability.

Interessados em participar do seminário devem realizar inscrição por formulário on-line para previsão de público e envio de certificado de participação

High-Energy Physics Seminars: “Scattering Amplitudes”

The Feynman rules appear as a simple way to calculate scattering amplitudes, however some complications appear if the multiplicity of particles is large. For example, in the 2 to 2 scattering of gluons there are only 4 Feynman diagrams but if we add two extra gluons it grows to 220 diagrams. In the 80’s Stephen Parke and Tomasz Taylor found an incredible way to simplify the calculation of some classes of n-gluons scattering amplitudes based on helicity arguments. Since then, a lot of progress has been made on improving the amplitude techniques and on the understanding of the S-matrix physics. After a review of the spinor helicity formalism and some well known results based on it, I will discuss how we can use the helicity structure of scattering amplitudes in the SM and in the context of an effective Lagrangian description of BSM dynamics. The analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 to 2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. This have a big impact on how we should perform the EFT analysis and where we should search for new physics.

Filosofísica: “As mulheres, a ciência e a filosofia”

Uma breve discussão de como as origens da produção científica e filosófica proporcionaram o apagamento histórico dos registros intelectuais e científicos das mulheres.