Thermal corpuscular black holes

We study the corpuscular model of an evaporating black hole consisting of a specific quantum state for a large number $N$ of self-confined bosons. The single-particle spectrum contains a discrete ground state of energy $m$ (corresponding to toy gravitons forming the black hole), and a gapless continuous spectrum (to accommodate for the Hawking radiation with energy $\omega>m$). Each constituent is in a superposition of the ground state and a Planckian distribution at the expected Hawking temperature in the continuum. We first find that, assuming the Hawking radiation is the leading effect of the internal scatterings, the corresponding $N$-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy $M=N\,m$ and a Planckian distribution for $E>M$ at the same Hawking temperature. From this collective state, we compute the partition function and obtain an entropy which reproduces the usual area law with a logarithmic correction precisely related with the Hawking component. By means of the horizon wave-function for the system, we finally show the backreaction of modes with $\omega>m$ reduces the Hawking flux. Both corrections, to the entropy and to the Hawking flux, suggest the evaporation properly stops for vanishing mass, if the black hole is in this particular quantum state.Comment: PDFLaTeX, 15 pages, 2 figure. Version to appear in PR

Consistent Cosmic Microwave Background Spectra from Quantum Depletion

Following a new quantum cosmological model proposed by Dvali and Gomez, we quantitatively investigate possible modifications to the Hubble parameter and following corrections to the cosmic microwave background spectrum. In this model, scalar and tensor perturbations are generated by the quantum depletion of the background inflaton and graviton condensate respectively. We show how the inflaton mass affects the power spectra and the tensor-to-scalar ratio. Masses approaching the Planck scale would lead to strong deviations, while standard spectra are recovered for an inflaton mass much smaller than the Planck mass.Comment: 23 pages, 9 figures; revised version to match published versio

Black holes as self-sustained quantum states, and Hawking radiation

We employ the recently proposed formalism of the "horizon wave-function" to investigate the emergence of a horizon in models of black holes as Bose-Einstein condensates of gravitons. We start from the Klein-Gordon equation for a massless scalar (toy graviton) field coupled to a static matter current. The (spherically symmetric) classical field reproduces the Newtonian potential generated by the matter source, and the corresponding quantum state is given by a coherent superposition of scalar modes with continuous occupation number. Assuming an attractive self-interaction that allows for bound states, one finds that (approximately) only one mode is allowed, and the system can be confined in a region of the size of the Schwarzschild radius. This radius is then shown to correspond to a proper horizon, by means of the horizon wave-function of the quantum system, with an uncertainty in size naturally related to the expected typical energy of Hawking modes. In particular, this uncertainty decreases for larger black hole mass (with larger number of light scalar quanta), in agreement with semiclassical expectations, a result which does not hold for a single very massive particle. We finally speculate that a phase transition should occur during the gravitational collapse of a star, ideally represented by a static matter current and Newtonian potential, that leads to a black hole, again ideally represented by the condensate of toy gravitons, and suggest an effective order parameter that could be used to investigate this transition.Comment: 25 pages, 6 figures. Improved text and typos fixed. Final version to appear in PR

Thermal BEC black holes

We review some features of BEC models of black holes obtained by means of the HWF formalism. We consider the KG equation for a toy graviton field coupled to a static matter current in spherical symmetry. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with continuous occupation number. An attractive self-interaction is needed for bound states to form, so that (approximately) one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The HWF is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons), in agreement with semiclassical calculations and different from a single very massive particle. The spectrum contains a discrete ground state of energy $m$ (the bosons forming the black hole), and a continuous spectrum with energy $\omega > m$ (representing the Hawking radiation and modelled with a Planckian distribution at the expected Hawking temperature). The $N$-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy $M = N m$ and a Planckian distribution for $E > M$ at the same Hawking temperature. The partition function is then found to yield the usual area law for the entropy, with a logarithmic correction related with the Hawking component. The backreaction of modes with $\omega > m$ is also shown to reduce the Hawking flux and the evaporation properly stops for vanishing mass.Comment: 30 pages, pdflatex with 6 figures. Review paper prepared for Entropy special issue "Entropy in Quantum Gravity and Quantum Cosmology

People-related TQM practices: the role of metaperceptions

Purpose– The authors investigate the role of people-related Total Quality Management (TQM) practices, specifically metaperceptions, in hearing care students’ vocational decision-making. In Italy, audiologists are health professionals and must hold a degree in hearing care. They operate according to clinical principles but must also develop marketing and commercial skills. While employers take these aspects for granted, the expectations of hearing care students often differ from reality. Thus, the authors aim to investigate the vocational expectations of hearing care students. Design/methodology/approach– A survey was distributed to 600 hearing care students. Multiple regression analysis with bootstrapped confidence intervals was employed to test the hypotheses. Findings–Studentswhoperceivedaudiologyastheircallingweremoreinterestedintheclinicalaspectsthan the marketing and commercial aspects of audiology. Moreover, those desiring a meaningful career path in audiology were more interested in becoming a store owner or franchisee. Social implications– Universities and recruiters should consider the influence of relevant others’ metaperceptions on students’ self-perceptions of their aptitudes for different careers. Universities should assist studentstoidentifyaptitudesthatare relevanttocareer-related decision-making.Inthis context,people-related TQMcanhelp students avoid incorrect aspirations and expectations. Originality/value– This study is the first to investigate the role of metaperceptions from a people-related TQMperspective. Metaperceptions play a crucial role in determining the correct course of study as well as job satisfaction and expectations

THE USE OF PORTFOLIO MANAGEMENT FOR STRATEGIC ALIGNMENT – A SURVEY WITH BRAZILIAN COMPANIES

The number of organizations that use the Project Portfolio Management - PPM has increased considerablyworldwide, as it provides an approach to the coordinated management of the components portfolio,aiming to achieve the strategies of organizations. The objective of this work was, thru a quantitativeresearch, presents Brazilian organizations use of PPM as a mechanism to promote alignment with thestrategic management. The results obtained in this research were compared with the data results obtainedin PMSurvey.org´s 2012 research. A survey submited for 56 brazilian public and private companies wasused for this study to identify project´s portfolio alignment with strategic goals and objectives.The number of organizations that use the Project Portfolio Management - PPM has increased considerablyworldwide, as it provides an approach to the coordinated management of the components portfolio,aiming to achieve the strategies of organizations. The objective of this work was, thru a quantitativeresearch, presents Brazilian organizations use of PPM as a mechanism to promote alignment with thestrategic management. The results obtained in this research were compared with the data results obtainedin PMSurvey.org´s 2012 research. A survey submited for 56 brazilian public and private companies wasused for this study to identify project´s portfolio alignment with strategic goals and objectives