B=1 Soliton of the Nambu - Jona-Lasinio model in medium}

The solitonic sector of the Nambu - Jona-Lasinio model with baryon number one is solved in the presence of an external medium. The calculations fully include the polarization of both the Dirac sea and the medium as well as the Pauli blocking effect. We found that with an increasing density the medium destabilizes the soliton. At finite medium density the soliton mass gets reduced whereas the mean square baryon radius shows an increase - a swelling of the soliton. At some critical density of about two times nuclear matter density there is no localized solution - the soliton disappears.Comment: PHYSTEX, 14 pages, 5 figures (available upon request), Preprint RUB-TPII-26/9

Phantom Friedmann Cosmologies and Higher-Order Characteristics of Expansion

We discuss a more general class of phantom ($p < -\varrho$) cosmologies with various forms of both phantom ($w -1$) matter. We show that many types of evolution which include both Big-Bang and Big-Rip singularities are admitted and give explicit examples. Among some interesting models, there exist non-singular oscillating (or "bounce") cosmologies, which appear due to a competition between positive and negative pressure of variety of matter content. From the point of view of the current observations the most interesting cosmologies are the ones which start with a Big-Bang and terminate at a Big-Rip. A related consequence of having a possibility of two types of singularities is that there exists an unstable static universe approached by the two asymptotic models - one of them reaches Big-Bang, and another reaches Big-Rip. We also give explicit relations between density parameters $\Omega$ and the dynamical characteristics for these generalized phantom models, including higher-order observational characteristics such as jerk and "kerk". Finally, we discuss the observational quantities such as luminosity distance, angular diameter, and source counts, both in series expansion and explicitly, for phantom models. Our series expansion formulas for the luminosity distance and the apparent magnitude go as far as to the fourth-order in redshift $z$ term, which includes explicitly not only the jerk, but also the "kerk" (or "snap") which may serve as an indicator of the curvature of the universe.Comment: REVTEX 4, 23 pages, references updated, to appear in Annals of Physics (N.Y.

The Problem of Matter Stability in the Nambu--Jona-Lasinio Model

We reinvestigate the conditions for stable matter solutions in the Nambu--Jona-Lasinio (NJL) model. In mean field approximation the NJL model can be regarded as an extension of the Walecka mean field model to include negative energy fermion states. While this extension is necessary to allow for a chiral phase transition, it was found some time ago that at the same time it destroys the wanted saturation properties of the Walecka model. We reformulate this problem in terms of the thermodynamic potential and find that there is indeed a connection between these two features. We show that the minimum of the thermodynamic potential which corresponds to stable nuclear matter in the Walecka model is shifted from a finite to zero effective fermion mass in the chiral NJL model. This shift is closely related to the chiral phase transition. Under certain conditions the shifted minima may still lead to stable matter solutions but only in the chirally restored phase. We discuss a possible interpretation of these solutions as a schematic bag model description.Comment: 21 pages, LaTeX, 5 postscript figures, Nucl. Phys. A, in pres

ENSINO DE MICROBIOLOGIA NOS ANOS INICIAIS: O USO DE JOGOS NA PROMOÇÃO DA APRENDIZAGEM SIGNIFICATIVA

Recentemente, com a pandemia de COVID-19, ficou evidente a necessidade de compreender a microbiologia por meio do desenvolvimento do pensamento científico desde os Anos Iniciais, não no sentido de formar pequenos cientistas, mas de fomentar nos alunos habilidades para que possam se posicionar diante dos temas da sociedade de forma crítica, construindo assim uma aprendizagem significativa. Neste contexto, o uso de jogos pode ser um poderoso instrumento para o desenvolvimento da aprendizagem significativa por meio das relações sociais. Assim, define-se que o objetivo deste trabalho foi investigar o potencial de um jogo envolvendo microbiologia para o Ensino de Ciências com alunos do primeiro ano do Ensino Fundamental, como forma de promover a Aprendizagem Significativa e desenvolver o pensamento científico. A pesquisa foi um estudo de caso de natureza qualitativa e contou com etapas como Brainstorming, aula expositiva sobre seres microscópicos e principais doenças causadas por eles, jogo autoral “Detetives do mundo microscópico” e avaliação da aprendizagem. Os resultados mostraram que o jogo foi capaz de sanar as lacunas conceituais, promoveu de maneira significativa a incorporação de novos conceitos acerca do tema abordado e deu subsídios para que os alunos desenvolvessem habilidades para o pensamento científico.  Article visualizations

Baryons as non-topological chiral solitons

The present review gives a survey of recent developments and applications of the Nambu--Jona-Lasinio model with $N_f=2$ and $N_f=3$ quark flavors for the structure of baryons. The model is an effective chiral quark theory which incorporates the SU(N$_f$)$_L\otimes$SU(N$_f$)$_R\otimes$U(1)$_V$ approximate symmetry of Quantum chromodynamics. The approach describes the spontaneous chiral symmetry breaking and dynamical quark mass generation. Mesons appear as quark-antiquark excitations and baryons arise as non-topological solitons with three valence quarks and a polarized Dirac sea. For the evaluation of the baryon properties the present review concentrates on the non-linear Nambu--Jona-Lasinio model with quark and Goldstone degrees of freedom which is identical to the Chiral quark soliton model obtained from the instanton liquid model of the QCD vacuum. In this non-linear model, a wide variety of observables of baryons of the octet and decuplet is considered. These include, in particular, electromagnetic, axial, pseudoscalar and pion nucleon form factors and the related static properties like magnetic moments, radii and coupling constants of the nucleon as well as the mass splittings and electromagnetic form factors of hyperons. Predictions are given for the strange form factors, the scalar form factor and the tensor charge of the nucleon.Comment: 104 pages, 27 figures as uuencoded and compressed postscript files , hardcopy available upon request; Prog.Part.Nucl.Phys. 37 (1996) (in print

The Minimal Scale Invariant Extension of the Standard Model

We perform a systematic analysis of an extension of the Standard Model that includes a complex singlet scalar field and is scale invariant at the tree level. We call such a model the Minimal Scale Invariant extension of the Standard Model (MSISM). The tree-level scale invariance of the model is explicitly broken by quantum corrections, which can trigger electroweak symmetry breaking and potentially provide a mechanism for solving the gauge hierarchy problem. Even though the scale invariant Standard Model is not a realistic scenario, the addition of a complex singlet scalar field may result in a perturbative and phenomenologically viable theory. We present a complete classification of the flat directions which may occur in the classical scalar potential of the MSISM. After calculating the one-loop effective potential of the MSISM, we investigate a number of representative scenarios and determine their scalar boson mass spectra, as well as their perturbatively allowed parameter space compatible with electroweak precision data. We discuss the phenomenological implications of these scenarios, in particular, whether they realize explicit or spontaneous CP violation, neutrino masses or provide dark matter candidates. In particular, we find a new minimal scale-invariant model of maximal spontaneous CP violation which can stay perturbative up to Planck-mass energy scales, without introducing an unnaturally large hierarchy in the scalar-potential couplings.Comment: 71 pages, 34 eps figures, numerical error corrected, clarifying comments adde

Disseminated Microsporidiosis in an Immunosuppressed Patient

We report a case of disseminated microsporidiosis in a patient with multiple myeloma who had received an allogeneic stem cell transplant requiring substantial immunosuppression. The causative organism was identified as Tubulinosema acridophagus, confirming this genus of microsporidia as a novel human pathogen

The soft supersymmetry breaking in D=5 supergravity compactified on S_1/Z_2 orbifolds

We study the origin of the supersymmetry breaking induced by the mediation of gravity and the radion multiplet from the hidden to the visible brane in the context of the N=2, D=5 supergravity compactified on S_1/Z_2 orbifolds. The soft supersymmetry breaking terms for scalar masses, trilinear scalar couplings and gaugino masses are calculated to leading order in the five dimensional Newton's constant k_5^2 and the gravitino mass m_{3/2}. These are finite and non-vanishing, with the scalar soft masses be non-tachyonic, and are all expressed in terms of the gravitino mass and the length scale R of the fifth dimension. The soft supersymmetry breaking parameters are thus correlated and the phenomenological implications are discussed.Comment: 16 pages, 3 figures, 1 Table, final version to appear in Physics Letters B, slightly shortened, comments added, typos correcte

Nucleon Form Factors from 5D Skyrmions

Several aspects of hadron physics are well described by a simple 5D effective field theory. Baryons arise in this scenario as "large" (and therefore calculable) 5D skyrmions. We extend and refine the existing analysis of this 5D soliton, which is fairly non-trivial due to the need of numerical methods. We perform the complete quantization of those collective coordinates which are relevant for computing the static observables like the nucleon form factors. We compare the result with simple expectations about large-N_c QCD and with the experimental data. An agreement within 30% is found.Comment: 30 pages, 6 figures; v2: References added and typos corrected; v3: Version published in Nucl. Phys.