19,003 research outputs found

    Quantum Fluctuations of Planck Mass as Mutation Mechanism in a Theory of Evolution of the Universe

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    Contributed talk at the Seventh Marcel Grossman Meeting on Gravity, June 24-30. A theory of evolution of the universe requires both a mutation mechanism and a selection mechanism. We believe that both can be encountered in the stochastic approach to quantum cosmology. In Brans-Dicke chaotic inflation, the quantum fluctuations of Planck mass behave as mutations, such that new inflationary domains may contain values of Planck mass that differ slightly from their parent's. The selection mechanism establishes that the value of Planck mass should be such as to increase the proper volume of the inflationary domain, which will then generate more offsprings. This mechanism predicts that the effective Planck scale at the end of inflation should be much larger than any given scale in the model.Comment: 3 pages, Stanford University preprint SU-ITP-94-32, IEM-FT-92/9

    Preheating the universe in hybrid inflation

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    One of the fundamental problems of modern cosmology is to explain the origin of all the matter and radiation in the Universe today. The inflationary model predicts that the oscillations of the scalar field at the end of inflation will convert the coherent energy density of the inflaton into a large number of particles, responsible for the present entropy of the Universe. The transition from the inflationary era to the radiation era was originally called reheating, and we now understand that it may consist of three different stages: preheating, in which the homogeneous inflaton field decays coherently into bosonic waves (scalars and/or vectors) with large occupation numbers; backreaction and rescattering, in which different energy bands get mixed; and finally decoherence and thermalization, in which those waves break up into particles that thermalize and acquire a black body spectrum at a certain temperature. These three stages are non-perturbative, non-linear and out of equilibrium, and we are just beginning to understand them. In this talk I will concentrate on the preheating part, putting emphasis on the differences between preheating in chaotic and in hybrid inflation.Comment: 6 pages, LaTeX, uses moriond.sty (included), no figures. Contribution to the proceedings of Moriond 98, Fundamental Parameters in Cosmology, Les Arcs, France (January 17-24, 1998

    Primordial Gravitational Waves and the local B-mode polarization of the CMB

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    A stochastic background of primordial gravitational waves could be detected soon in the polarization of the CMB and/or with laser interferometers. There are at least three GWB coming from inflation: those produced during inflation and associated with the stretching of space-time modes; those produced at the violent stage of preheating after inflation; and those associated with the self-ordering of Goldstone modes if inflation ends via a global symmetry breaking scenario, like in hybrid inflation. Each GW background has its own characteristic spectrum with specific features. We discuss the prospects for detecting each GWB and distinguishing between them with a very sensitive probe, the local B-mode of CMB polarization.Comment: 5 pages, 6 figures, to appear in the Proceedings of Moriond Cosmology 201

    Particle Physics and Cosmology

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    In this talk I review the present status of inflationary cosmology and its emergence as the basic paradigm behind the Standard Cosmological Model, with parameters determined today at better than 10% level from CMB and LSS observations.Comment: 12 pages, LaTeX, uses frascatiphys_R.sty (included). Plenary talk, to appear in the Proceedings of the First International Workshop on Frontier Science, October 6-11, 2002, Frascati (Italy

    Evidence for single top quark production at D0

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    The results of the first analysis to show evidence for production of single top quarks are presented. Using 0.9 fb-1 of data collected with the D0 detector at the Fermilab Tevatron, the analysis is performed in the electron+jets and muon+jets decay modes, taking special care in modeling the large backgrounds, applying a new powerful b-quark tagging algorithm and using three multivariate techniques to extract the small signal in the data. The combined measured production cross section is 4.8 +- 1.3 pb. The probability to measure a cross section at this value or higher in the absence of a signal is 0.027%, corresponding to a 3.5 standard deviation significance.Comment: 6 pages, 4 figures. Presented at 42nd Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 10-17 Mar 200

    PALLIATIVE CARE ELDERLY PATIENTS WITH SLEEPING DISORDERS ARE POORLY TREATED

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    Background: Sleep disorders are frequent in patients with advanced cancer receiving palliative-care, especially in elderly patients (1). Sleep disorders during palliative-care may be related with anxiety, opioids related central-sleep apnoea or corticoids therapy between others (2). Our aim was to quantify the effectiveness of hypnotic medication in the sleep quality in advanced cancer receiving palliative-care elderly patients. Material and methods: A descriptive cross-sectional study was conducted in elderly patients with advanced cancer receiving palliative-care exploring their sleep quantity and quality (approved by Local Ethical Committee). Patients who were in our palliative care program and didn´t have any exclusion criteria: Age below 60 years, with ability to communicate effectively, and without cognitive failure and/or delirium, and/or psychotic illness. The Pittsburgh Sleep Quality Index (PSQI) questionnaire and EVA scales were used to measured sleep quality and pain and anxiety levels. Patient under corticoids treatment were compared with other non-sleep disorders risky treatment. Results are expressed as mean ± sem. and were compared by Student t test and ANOVA test followed by Bonferroni post-test. Results: Patients, N=138, 63.8% male, aged 70.9±1.1 years old with diagnostic of 28.3% gastro-intestinal, 15.9% mama/gynaecological , 13% pulmonary, 12.3% urinary, 6.5% liver, 4.3% central nervous system, 1.4% pancreatic, and 18.1% others types of terminal cancer were enrolled. Patients were treated with no oncologic treatment (78.3%), chemotherapy (12.3%), radiotherapy (5.1%), hormone therapy (3.6%), or immunotherapy (0.7%). 54.3% were treated with corticoids vs. 20.3% under other sleep disorders risky treatment and 25.4% with no treatment. The sleep disturbances prevalence were 81.2% in the total population and 90.4% in patients treated with corticoids (p<0.05). However a 54.3% of the patients received benzodiazepines, zolpidem or chlormethiazole. 65.2% of the patients need more than three times rescue hypnotic medication during the last week. Bad sleeper showed significantly higher intensity of pain, asthenia, sadness, anxiety, nausea, dyspnea and discomfort. Discussion: Sleep disorders may be primary or, more commonly, a secondary symptom of the advancing disease process. Multiple pharmacologic and non-pharmacologic interventions may be used for the management of sleep disturbances in palliative medicine. However, many patients do not seek medical attention for sleep disturbances, and health care providers tend to under-diagnose this condition and under-treat it when diagnosed, thus missing an opportunity to improve the quality of life of patients already suffering from the burden of terminal disease. The diversity of patients under palliative care makes management of sleep disorders particularly challenging and highly needed to be individualized. Conclusion. Elderly patients with advanced cancer subjected to palliative care received insufficient hypnotic medication especially under corticoids co-treatment. References: (1) Sateia MJ and Lang BJ. 2008. Curr Oncol Rep 10(4):309-18. (2) Yennurajalingam S et al. 2011. J Pain Symptom Manage 41(1):49-56.University of Malaga. Campus of International Excellence Andalucia Tech

    Looking for single top quarks in D0 data

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    The search for the electroweak production of top quarks is entering an exciting time: with the ever increasing luminosity furnished by the Tevatron ppbar Collider at Fermilab and sophisticated analysis techniques we are now able to approach the expected standard model production cross section for this new mode of production. Using 370pb-1 of D0 data and likelihoods as discriminants to extract the signal from the large backgrounds, we set upper limits on the standard model production cross section in the s-channel of 5.0 pb and in the t-channel of 4.4 pb, at 95% confidence level.Comment: 5 pages, 3 figures. Contributed to the proceedings of the 34th International Meeting on Fundamental Physics. El Escorial, Spain, April 200
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