Quantum Effect and Curvature Strength of Naked Singularities

There are many solutions to the Einstein field equations that demonstrate naked singularity (NS) formation after regular evolution. It is possible, however, that such a quantum effect as particle creation prevents NSs from forming. We investigate the relation between the curvature strength and the quantum effects of NSs in a very wide class of spherical dust collapse. Through a perturbative calculation, we find that if the NS is very strong, the quantum particle creation diverges as the Cauchy horizon is approached, while if the NS is very weak, the creation should be finite. In the context of cosmic censorship, strong NSs will be subjected to the backreaction of quantum effects and may disappear or be hidden behind horizons, while weak NSs will not.Comment: 21 pages, 1 table, 3 figures. Final version to appear in Progress of Theoretical Physic

Conformally Schwarzschild cosmological black holes

We thoroughly investigate conformally Schwarzschild spacetimes in different coordinate systems to seek for physically reasonable models of a cosmological black hole. We assume that a conformal factor depends only on the time coordinate and that the spacetime is asymptotically flat Friedmann-Lema\^{\i}tre-Robertson-Walker universe filled by a perfect fluid obeying a linear equation state $p=w\rho$ with $w>-1/3$. In this class of spacetimes, the McClure-Dyer spacetime, constructed in terms of the isotropic coordinates, and the Thakurta spacetime, constructed in terms of the standard Schwarzschild coordinates, are identical and do not describe a cosmological black hole. In contrast, the Sultana-Dyer and Culetu classes of spacetimes, constructed in terms of the Kerr-Schild and Painlev\'{e}-Gullstrand coordinates, respectively, describe a cosmological black hole. In the Sultana-Dyer case, the corresponding matter field in general relativity can be interpreted as a combination of a homogeneous perfect fluid and an inhomogeneous null fluid, which is valid everywhere in the spacetime unlike Sultana and Dyer's interpretation. In the Culetu case, the matter field can be interpreted as a combination of a homogeneous perfect fluid and an inhomogeneous anisotropic fluid. However, in both cases, the total energy-momentum tensor violates all the standard energy conditions at a finite value of the radial coordinate in late times. As a consequence, the Sultana-Dyer and Culetu black holes for $-1/3<w\le 1$ cannot describe the evolution of a primordial black hole after its horizon entry.Comment: 58 pages, 10 figures, 8 tables; v3, this version corrects the published version according to the corrigendum (2023 Class. Quantum Grav. 40, 079501). The main results remain unchange

Análise dos elementos de mudança organizacional e lean office aplicados a uma unidade contábil

Orientador : Maria do Carmo Duarte FreitasCo-orientador: Ana Carolina GreefMonografia (graduação) - Universidade Federal do Paraná, Setor de Ciências Sociais Aplicadas, Curso de Gestão da Informação.Inclui referênciasResumo : Pesquisa exploratória e qualitativa que objetiva a identificação de elementos de mudança organizacional e Lean Office convergentes, assim, contribuírem para efetividade do processo de transformações, em uma unidade contábil de uma empresa mista de cunho social, com base no pensamento enxuto. Apresenta como literatura a Gestão da Informação, a mudança organizacional e o Lean Office. Estabelece uma relação entre as etapas de processo de mudança apresentado por Kotter e as ações do pensamento enxuto. Identifica, por meio de um estudo de caso em uma unidade organizacional contábil, os elementos convergentes identificados. Analisa os resultados obtidos por meio do confronto com as teorias estudadas no referencial teórico. O estudo indica o comportamento e o preparo de uma unidade organizacional para processo de mudanças com base no conceito Lean. Por meio do resultado obtido conclui-se que o preparo do ambiente não é inteiramente adequado para receber tais transformações. Entretanto, evidencia-se que o preparo para recebê-las deve ser implantado nesses ambientes, sobretudo pela carga de mudanças que esses lugares têm sido submetidos

Self-similar cosmological solutions with dark energy. II: black holes, naked singularities and wormholes

We use a combination of numerical and analytical methods, exploiting the equations derived in a preceding paper, to classify all spherically symmetric self-similar solutions which are asymptotically Friedmann at large distances and contain a perfect fluid with equation of state $p=(\gamma -1)\mu$ with $0<\gamma<2/3$. The expansion of the Friedmann universe is accelerated in this case. We find a one-parameter family of self-similar solutions representing a black hole embedded in a Friedmann background. This suggests that, in contrast to the positive pressure case, black holes in a universe with dark energy can grow as fast as the Hubble horizon if they are not too large. There are also self-similar solutions which contain a central naked singularity with negative mass and solutions which represent a Friedmann universe connected to either another Friedmann universe or some other cosmological model. The latter are interpreted as self-similar cosmological white hole or wormhole solutions. The throats of these wormholes are defined as two-dimensional spheres with minimal area on a spacelike hypersurface and they are all non-traversable because of the absence of a past null infinity.Comment: 12 pages, 19 figures, 1 table, final version to appear in Physical Review

Response time differences during hand mental rotation

This study explored gender differences in correct response rates and response times on a task involving left or right arrow selection and another involving the transformation of mental rotation of the hand. We recruited 15 healthy, right-handed men (age 24.5 ± 6.4) and 15 healthy, right-handed women (age 21.3 ± 4.9). For the tasks, we used pictures of left and right arrows and 32 hand pictures (left and right, palm and back) placed in cons (each at 45° from 0° to 315°). Hand and arrow pictures alternated and were shown at random. Participants decided as quickly as possible whether each picture was left or right. To compare the time taken for the transformation of mental rotation of the hand, we subtracted the average arrow response time from that for the left and right hand pictures for each participant. Correct response rates did not differ significantly between men and women or left and right for either arrow or hand pictures. Regardless of gender, the response time was longer for the left arrow picture than right arrow picture. The response time for the hand picture was longest for both men and women for pictures at rotation angles that were most difficult to align with participants’ hands. While there was no difference between men’s responses for left and right hand pictures, the responses of women were longer for left than right hand pictures and also than those of men. These findings suggest that both men and women mainly perform the hand mental rotation task with implicit motor imagery. On the other hand, the gender difference in performance might be explained by the difference in balance with other strategies, such as visual imagery, and by cognitive, neurophysiological, and morphological differences

Linalool Odor-Induced Anxiolytic Effects in Mice

In folk medicine, it has long been believed that odorous compounds derived from plant extracts can have anxiolytic effects. Among them, linalool, one of the terpene alcohols in lavender extracts, has been reported to have the anxiolytic effects. However, the anxiolytic nature of the linalool odor itself as well as its potential action through the olfactory system has not been thoroughly examined. In this study, we examined the anxiolytic effects of linalool odor with light/dark box test and with elevated plus maze (EPM), and found that linalool odor has an anxiolytic effect without motor impairment in mice. The effect was not observed in anosmic mice, indicating that it was triggered by olfactory input evoked by linalool odor. Furthermore, the effect was antagonized by flumazenil, indicating that the linalool odor-induced anxiolytic effect was mediated by γ-aminobutyric acid (GABA)ergic transmission via benzodiazepine (BDZ)-responsive GABAA receptors. These results provide information about the potential central neuronal mechanisms underlying the odor-induced anxiolytic effects and the foundation for exploring clinical application of linalool odor in anxiety treatments