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Orientador: Prof. Dr. Celso Chikahiro Nishi Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, Santo André, 2022. A simetria de CP e violada no Modelo Padrao pela fase da matriz CKM no setor eletrofraco e, alem disso, a presenca do termo ¿Æ no setor forte do Modelo Padrao tambem violaria CP. O problema de CP forte consiste em explicar porque esta ultima violacao nao e observada experimentalmente e o valor de ¿Æ deve ser tao pequeno. Modelos do tipo Nelson-Barr sao modelos com violacao espontanea de CP que conseguem explicar simultaneamente o valor da fase da CKM e do termo ¿Æ. Modelos desse tipo necessitam da presenca de quarks vetoriais que transmitem a violacao de CP para o Modelo Padrao. Neste trabalho, vai se estudar diferentes modelos do tipo Nelson-Barr com um ou dois quarks vetoriais, com CP usual e CP4. Tambem foram abordadas as consequencias fenomenologicas e os limites experimentais do setor eletrofraco e da fisica de sabor para modelos do tipo Nelson-Bar com diferentes conteudos de quarks vetoriais. The CP symmetry is violated in the Standard Model by the phase of the CKM matrix in the electroweak sector and, in addition, the presence of the è term in the strong sector would violate CP as well. The strong CP problem consists on explaining why this last violation is not experimentally observed and the value of è should be so small. Nelson-Barr models are models with spontaneous CP violation that are capable of explaining simultaneously the value of the CKM phase and the è term. Models of this kind require the presence of vector-like quarks that transmit the CP violation to the SM. In this work, we study two models of Nelson-Barr type: the first is the minimal extension of the SM with the usual CP symmetry and the second with the non-conventional CP symmetry, CP4. We also discuss the phenomenological consequences and experimental limits from the electroweak sector and flavor physics for Nelson-Barr models with different contents of vector-like quarks.

Progress in particle and nuclear physics 124, 103947 - (2022). doi:10.1016/j.ppnp.2022.103947, This review demonstrates the unique role of the neutrino by discussing in detail the physics of and with neutrinos. We deal with neutrino sources, neutrino oscillations, absolute masses, interactions, the possible existence of sterile neutrinos, and theoretical implications. In addition, synergies of neutrino physics with other research fields are found, and requirements to continue successful neutrino physics in the future, in terms of technological developments and adequate infrastructures, are stressed., Published by Pergamon Press, Frankfurt, M.

In a recent paper (arXiv:1905.07348v1), Dyson scheme to deal with density matrix of non-Hermitian Hamiltonians has been used to investigate the entanglement of states of a PT-symmetric bosonic system. They found that von Neumann entropy can show a different behavior in the broken and unbroken regime. We show that their results can be recast in terms of an abstract model of pseudo-Hermitian random matrices. It is found however that, although the formalism is practically the same, the entanglement is not of Fock states but of Bell states., Comment: 15 pages, 2 figures

We investigate the statistical properties of eigenvalues of pseudo-Hermitian random matrices whose eigenvalues are real or complex conjugate. It is shown that when the spectrum splits into separated sets of real and complex conjugate eigenvalues, the real ones show characteristics of an intermediate incomplete spectrum, that is, of a so-called thinned ensemble. On the other hand, the complex ones show repulsion compatible with cubic-order repulsion of non normal matrices for the real matrices, but higher order repulsion for the complex and quaternion matrices.

The Lieb-Oxford bound is a constraint upon approximate exchange-correlation functionals. We explore a nonempirical tightening of that bound in both universal and electron number-dependent form. The test functional is PBE. Regarding both atomization energies (slightly worsened) and bond lengths (slightly improved), we find the PBE functional to be remarkably insensitive to the value of the Lieb-Oxford bound. This both rationalizes the use of the original Lieb-Oxford constant in PBE and suggests that enhancement factors more sensitive to sharpened constraints await discovery.

Bose systems, subject to the action of external random potentials, are considered. For describing the system properties, under the action of spatially random potentials of arbitrary strength, the stochastic mean-field approximation is employed. When the strength of disorder increases, the extended Bose-Einstein condensate fragments into spatially disconnected regions, forming a granular condensate. Increasing the strength of disorder even more transforms the granular condensate into the normal glass. The influence of time-dependent external potentials is also discussed. Fast varying temporal potentials, to some extent, imitate the action of spatially random potentials. In particular, strong time-alternating potential can induce the appearance of a nonequilibrium granular condensate., latex file, 26 pages, 1 figure

After summarizing the status of the Standard Model, we focus on the Hierarchy Problem and why we believe this strongly suggests the need for new physics at the TeV scale. We then concentrate on theories with extra dimensions and their possible manifestations at this scale., Presented at the First Latin American Workshop on High Energy Physics, Porto Alegre, December 3-5 2005