Phase transition of the nucleon-antinucleon plasma at different ratios

We investigate phase transitions for the Walecka model at very high temperatures. As is well known, depending on the parametrization of this model and for the particular case of a zero chemical potential ($\mu$), a first order phase transition is possible \cite{theis}. We investigate this model for the case in which $\mu \ne 0$. It turns out that, in this situation, phases with different values of antinucleon-nucleon ratios and net baryon densities may coexist. We present the temperature versus antinucleon-nucleon ratio as well as the temperature versus the net baryon density for the coexistence region. The temperature versus chemical potential phase diagram is also presented.Comment: 5 pages, 8 figure

Running of the contact interactions in chiral N3LO potentials from subtractive renormalization

In this work a subtracted kernel renormalization procedure (SKM) is applied to the chiral NN potential up to next-to-next-to-next-to-leading-order ((NLO)-L-3) to obtain the running of the renormalized contact strengths with the subtraction scale mu and the phase shifts for all uncoupled waves with contact interaction (S, P, D). We use two potentials constructed within the framework of Weinberg's approach to ChEFT, which provide a very accurate description of NN scattering data below laboratory energies E similar to 350 MeV, namely Epelbaum, Glockle and Meissner (N3LO-EGM) and Entem and Machleidt (N3LO-EM). For both potentials, we consider a large cutoff (30 fm(-1)) and analyze the phases and the running of the contact strengths with the subtraction point mu by making a fit of the K-matrix with five subtractions to the K-matrix from the Nijmegen II potential at low energies (E <= 20 MeV).In this work a subtracted kernel renormalization procedure (SKM) is applied to the chiral NN potential up to next-to-next-to-next-to-leading-order (N 3 LO) to obtain the running of the renormalized contact strengths with the subtraction scale μ and the ph630FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOsem informaçãosem informação37th Brazilian Meeting on Nuclear PhysicsS.S. is partially supported by FAPESP and V.S.T. would like to thank FAEPEX, FAPESP and CNPq for financial support

Nonlinear Klein-Gordon equation and the Bose-Einstein condensation

El interés por la ecuación de Klein-Gordon con diferentes potenciales ha aumentado en los últimos años debido a su posible aplicaciones en Cosmología, Física de Hadrones y Física de Altas Energías. En este trabajo, investigamos las soluciones de la ecuación de Klein–Ecuación para bosones bajo la influencia de un potencial externo utilizando el método de Feshbach-Villars. Presentamos resultados detallados en dos casos: el potencial de Coulomb y el potencial armónico. Para el segundo caso, estudiamos los efectos de la auto-interacción de partículas dentro de una aproximación de de campo medio. Mostramos que nuestros resultados convergen suavemente a la solución de la ecuación de Schrödinger para los mismos sistemas a medida que disminuyen los efectos relativistas. En inglés: The interest in the Klein–Gordon equation with different potentials has increased in recent years due to its possible applications in Cosmology, Hadron Physics and High-Energy Physics. In this work, we investigate the solutions of the Klein–Gordon equation for bosons under the influence of an external potential by using the Feshbach–Villars method. We present detailed results for two cases: the Coulombic potential and the harmonic potential. For the latter case, we studied the effects of self-interacting particles by adopting a mean-field approach. We show that our results converge smoothly to the solution of the Schrödinger equation for the same systems as the relativistic effects diminish.FQM-225CNPq-Brazil 304244/2018-0Consejería de ConocimientoConselho Nacional de Desenvolvimento Científico e TecnológicoFAEPEX 2019/010889-1, 3258/19Investigación y Universidad of the Junta de AndalucíaJunta de Andalucía-Consejería de Economía y Conocimiento 2014-2020 Operational ProgramFundação de Amparo à Pesquisa do Estado de São Paulo 2021/12954-5Conselho Nacional de Desenvolvimento Científico e Tecnológico 306615/2018-5European Regional Development Fund RYC-2016-20678, SOMM17/6105/UGRJunta de Andalucía A-FQM-178-UGR18, FQM-225Instituto Nacional de Ciência e Tecnologia: Física Nuclear e Aplicações 2016/17612-7, 464 898/2014-5Consejería de Conocimiento, Investigación y Universidad, Junta de Andalucí

Symmetries of the Similarity Renormalization Group for Nuclear Forces

We analyze the role played by Long Distance Symmetries within the context of the Similarity Renormalization Group (SRG) approach, which is based on phase-shift preserving continuous unitary transformations that evolve hamiltonians with a cutoff on energy differences. We find that there is a SRG cutoff for which almost perfect fulfillment of Wigner symmetry is found. We discuss the possible consequences of such finding.Comment: 16 pages, 6 figures, to appear in Physical Review

Unitary neutron matter in the on-shell limit

37th Brazilian Meeting on Nuclear Physics. Sao Paulo (Brazil), 8-12 September 2014.We compute the Bertsch parameter for neutron matter by using nucleon-nucleon interactions that are fully diagonal in momentum space. We analyze the on-shell limit with the similarity renormalization group and compare the results for a simple separable toy model to realistic calculations with high precision NN potentials.E.R.A. would like to thank the Spanish DGI (Grant FIS2011-24149) and Junta de Andalucia (Grant FQM225) for support. S.S. is partially supported by FAPESP and V.S.T. thanks FAEPEX, FAPESP and CNPq for financial support

Power counting and renormalization group invariance in the subtracted kernel method for the two-nucleon system

We apply the subtracted kernel method (SKM), a renormalization approach based on recursive multiple subtractions performed in the kernel of the scattering equation, to the chiral nucleon-nucleon (NN) interactions up to next-to-next-to-leading-order (NNLO). We evaluate the phase-shifts in the 1S0 channel at each order in Weinberg's power counting scheme and in a modified power counting scheme which yields a systematic power-law improvement. We also explicitly demonstrate that the SKM procedure is renormalization group invariant under the change of the subtraction scale through a non-relativistic Callan-Symanzik flow equation for the evolution of the renormalized NN interactions.Comment: Accepted for publication in Journal of Physics G: Nuclear and Particle Physic

Efeito de Plastificantes à base de Poliisobutenos nas Propriedades Físicas e Mecânicas do Polipropilen

Neste trabalho investigou-se o efeito de poliisobutenos (PIB´s), de massas molares variando de 480 a 1.600 g/mol, no polipropileno isotático. Composições contendo até 7% dos PIB´s foram preparadas em misturador interno e corpos de prova foram confeccionados a partir de placas moldadas por compressão. Foram realizados ensaios de resistência à tração, microscopia eletrônica de varredura (MEV), difração de raios X (DRX), calorimetria exploratória diferencial (DSC) e índice de fluidez (IF). Os resultados de índice de fluidez indicaram uma acentuada redução na viscosidade com a presença dos plastificantes. Os ensaios mecânicos comprovaram o efeito plastificante dos PIB´s, em relação ao PP puro, com queda na tensão de escoamento e módulo elástico. As análises de DRX mostraram uma redução no grau de cristalinidade do polipropileno. As micrografias obtidas por MEV não evidenciaram a ocorrência de separação de fase, sugerindo que os componentes formam misturas miscíveis