Constraining the Natural MSSM through tunneling to color-breaking vacua at zero and non-zero temperature

We re-evaluate the constraints on the parameter space of the minimal supersymmetric standard model from tunneling to charge- and/or color-breaking minima, taking into account thermal corrections. We pay particular attention to the region known as the Natural MSSM, where the masses of the scalar partners of the top quarks are within an order of magnitude or so of the electroweak scale. These constraints arise from the interaction between these scalar tops and the Higgs fields, which allows the possibility of parameter points having deep charge- and color-breaking true vacua. In addition to requiring that our electro-weak-symmetry-breaking, yet QCD- and electromagnetism-preserving vacuum has a sufficiently long lifetime at zero temperature, also demanding stability against thermal tunneling further restricts the allowed parameter space.Comment: 7 pages, 2 figures, software available from http://vevacious.hepforge.org/ - version 2 matches that accepted for publication in Phys. Lett.

Vevacious: A Tool For Finding The Global Minima Of One-Loop Effective Potentials With Many Scalars

Several extensions of the Standard Model of particle physics contain additional scalars implying a more complex scalar potential compared to that of the Standard Model. In general these potentials allow for charge and/or color breaking minima besides the desired one with correctly broken SU(2)_L times U(1)_Y . Even if one assumes that a metastable local minimum is realized, one has to ensure that its lifetime exceeds that of our universe. We introduce a new program called Vevacious which takes a generic expression for a one-loop effective potential energy function and finds all the tree-level extrema, which are then used as the starting points for gradient-based minimization of the one-loop effective potential. The tunneling time from a given input vacuum to the deepest minimum, if different from the input vacuum, can be calculated. The parameter points are given as files in the SLHA format (though is not restricted to supersymmetric models), and new model files can be easily generated automatically by the Mathematica package SARAH. This code uses HOM4PS2 to find all the minima of the tree-level potential, PyMinuit to follow gradients to the minima of the one-loop potential, and CosmoTransitions to calculate tunneling times.Comment: 44 pages, 1 figure, manual for publicly available software, v2 corresponds to version accepted for publication in EPJC [clearer explanation of scale dependence and region of validity, explicit mention that SLHA files should have blocks matching those expected by model files, updated references

Gestão escolar demotrática e qualidade social da educação

This article examines the tensions between managerialist and democratic perspectives in contemporary Brazilian education policies, highlighting contradictions between discourse and practice. Although guiding documents such as the LDB and PNE convey emancipatory and inclusive ideals for education, government programs have emphasized accountability, quantitative results and market logics. At the same time, austerity measures such as EC 95 strangle in practice any possibility of implementing the progressive principles laid down in the legislation. This tension reveals broader disputes in the political arena, with sectors committed to the commercialization of education historically confronting the struggles for a public, free and quality school for all. There is an urgent need to reinvent the role of the state beyond regulation, reclaiming its leading role as provider and maintainer of the material conditions for the realization of the right to education.This reinvention involves collective mobilization to build educational processes that are contextualized, emancipatory and opposed to curricular lightening. It requires democratically run schools, with popular participation in pedagogical decisions and the use of resources. This demands an educational policy that is faithful to the interests of the majority, overcoming the privatist and managerialist agenda that undermines its democratizing potential. The universalization of quality standards as a right demands this reinvented public school, ethically committed to our people.O presente artigo examina as tensões entre perspectivas gerencialistas e democráticas nas políticas educacionais brasileiras contemporâneas, evidenciando contradições entre discursos e práticas. Embora documentos orientadores como LDB e PNE veiculem ideais emancipatórios e inclusivos para a educação, programas governamentais têm enfatizado accountability, resultados quantitativos e lógicas de mercado. Concomitantemente, medidas de austeridade como a EC 95 estrangulam na prática qualquer possibilidade de efetivação dos princípios progressistas previstos na legislação. Esse tensionamento revela disputas mais amplas na arena política, com setores comprometidos com a mercantilização do ensino confrontando historicamente as lutas por uma escola pública, gratuita e de qualidade para todos. Urge reinventar o papel do Estado para além da regulação, resgatando seu protagonismo como provedor e mantenedor de condições materiais à efetivação do direito à educação.Tal reinvenção passa pela mobilização coletiva pela construção de processos educativos contextualizados, emancipadores e contrários ao aligeiramento curricular. Requer escolas geridas democraticamente, com participação popular nas decisões pedagógicas e uso dos recursos. Reivindica-se assim uma política educacional fiel aos interesses das maiorias, superando a agenda privatista e gerencialista que solapa seus potenciais democratizantes. A universalização do padrão de qualidade como direito demanda essa escola pública reinventada e comprometida ethicamente com nossa gente.O presente artigo examina as tensões entre perspectivas gerencialistas e democráticas nas políticas educacionais brasileiras contemporâneas, evidenciando contradições entre discursos e práticas. Embora documentos orientadores como LDB e PNE veiculem ideais emancipatórios e inclusivos para a educação, programas governamentais têm enfatizado accountability, resultados quantitativos e lógicas de mercado. Concomitantemente, medidas de austeridade como a EC 95 estrangulam na prática qualquer possibilidade de efetivação dos princípios progressistas previstos na legislação. Esse tensionamento revela disputas mais amplas na arena política, com setores comprometidos com a mercantilização do ensino confrontando historicamente as lutas por uma escola pública, gratuita e de qualidade para todos. Urge reinventar o papel do Estado para além da regulação, resgatando seu protagonismo como provedor e mantenedor de condições materiais à efetivação do direito à educação.Tal reinvenção passa pela mobilização coletiva pela construção de processos educativos contextualizados, emancipadores e contrários ao aligeiramento curricular. Requer escolas geridas democraticamente, com participação popular nas decisões pedagógicas e uso dos recursos. Reivindica-se assim uma política educacional fiel aos interesses das maiorias, superando a agenda privatista e gerencialista que solapa seus potenciais democratizantes. A universalização do padrão de qualidade como direito demanda essa escola pública reinventada e comprometida ethicamente com nossa gente

Astrometry of mutual approximations between natural satellites. Application to the Galilean moons

Typically we can deliver astrometric positions of natural satellites with errors in the 50-150 mas range. Apparent distances from mutual phenomena, have much smaller errors, less than 10 mas. However, this method can only be applied during the equinox of the planets. We developed a method that can provide accurate astrometric data for natural satellites -- the mutual approximations. The method can be applied when any two satellites pass close by each other in the apparent sky plane. The fundamental parameter is the central instant $t_0$ of the passage when the distances reach a minimum. We applied the method for the Galilean moons. All observations were made with a 0.6 m telescope with a narrow-band filter centred at 889 nm with width of 15 nm which attenuated Jupiter's scattered light. We obtained central instants for 14 mutual approximations observed in 2014-2015. We determined $t_0$ with an average precision of 3.42 mas (10.43 km). For comparison, we also applied the method for 5 occultations in the 2009 mutual phenomena campaign and for 22 occultations in the 2014-2015 campaign. The comparisons of $t_0$ determined by our method with the results from mutual phenomena show an agreement by less than 1-sigma error in $t_0$, typically less than 10 mas. This new method is particularly suitable for observations by small telescopes.Comment: 13 pages, 11 figures and 8 tables. Based on observations made at the Laborat\'orio Nacional de Astrof\'isica (LNA), Itajub\'a-MG, Brazi

Taming the magnetoresistance anomaly in graphite

At low temperatures, graphite presents a magnetoresistance anomaly which manifests as a transition to a high-resistance state (HRS) above a certain critical magnetic field $\text{B}_\text{c}$. Such HRS is currently attributed to a c-axis charge-density-wave taking place only when the lowest Landau level is populated. By controlling the charge carrier concentration of a gated sample through its charge neutrality level (CNL), we were able to experimentally modulate the HRS in graphite for the first time. We demonstrate that the HRS is triggered both when electrons and holes are the majority carriers but is attenuated near the CNL. Taking screening into account, our results indicate that the HRS possess a strong in-plane component and can occur below the quantum limit, being at odds with the current understanding of the phenomenon. We also report the effect of sample thickness on the HRS