Hawking radiation of nonsingular black holes in two dimensions

In this letter we study the process of Hawking radiation of a black hole assuming the existence of a limiting physical curvature scale. The particular model is constructed using the Limiting Curvature Hypothesis (LCH) and in the context of two-dimensional dilaton gravity. The black hole solution exhibits properties of the standard Schwarzschild solution at large values of the radial coordinate. However, near the center, the black hole is nonsingular and the metric becomes that of de Sitter spacetime. The Hawking temperature is calculated using the method of complex paths. We find that such black holes radiate eternally and never completely evaporate. The final state is an eternally radiating relic, near the fundamental scale, which should make a viable dark matter candidate. We briefly comment on the black hole information loss problem and the production of such black holes in collider experiments.Comment: 8 pages, 4 figures; minor revisions; references added; version to appear in JHE

Towards a Stringy Resolution of the Cosmological Singularity

We study cosmological solutions to the low-energy effective action of heterotic string theory including possible leading order $\alpha'$ corrections and a potential for the dilaton. We consider the possibility that including such stringy corrections can resolve the initial cosmological singularity. Since the exact form of these corrections is not known the higher-derivative terms are constructed so that they vanish when the metric is de Sitter spacetime. The constructed terms are compatible with known restrictions from scattering amplitude and string worldsheet beta-function calculations. Analytic and numerical techniques are used to construct a singularity-free cosmological solution. At late times and low-curvatures the metric is asymptotically Minkowski and the dilaton is frozen. In the high-curvature regime the universe enters a de Sitter phase.Comment: 6 pages, 2 Figures; minor revisions; references added; REVTeX 4; version to appear in Phys. Rev.

A Curvature Principle for the interaction between universes

We propose a Curvature Principle to describe the dynamics of interacting universes in a multi-universe scenario and show, in the context of a simplified model, how interaction drives the cosmological constant of one of the universes toward a vanishingly small value. We also conjecture on how the proposed Curvature Principle suggests a solution for the entropy paradox of a universe where the cosmological constant vanishes.Comment: Essay selected for an honorable mention by the Gravity Research Foundation, 2007. Plain latex, 8 page

ХИРУРГИЧЕСКОЕ ЛЕЧЕНИЕ ИЗОЛИРОВАННОЙ АСЕПТИЧЕСКОЙ НЕСТАБИЛЬНОСТИ ВЕРТЛУЖНОГО КОМПОНЕНТА У ПАЦИЕНТОВ СО СТАБИЛЬНЫМ ФЕМОРАЛЬНЫМ КОМПОНЕНТОМ

Background: Aseptic acetabular loosening currently occupies the 1st place in the structure of delayed complications after total hip arthroplasty. The basis of treatment is the replacement of a loosening cup and a pair of friction. The tactics of surgical treatment of the stable correctly oriented femoral component have not been determined, thoroughly which confirms the relevance of the study.Aims: Compare the effectiveness of total hip revision and isolated acetabular revision in patients with aseptic acetabular loosening and stable correctly oriented femoral component.Materials and methods: The study presented the results of surgical treatment performed in 44 patients (45 revisions) with isolated aseptic acetabular loosening and stable correctly oriented femoral component were presented, Patients were divided into two groups depending on the severity of surgery. The first group included 16 patients with a total revision due to irregular cone of the stem. The second group included 28 patients (29 revisions) with an isolated replacement of the unstable cup and a pair of friction.Results: In the 1st group, revision surgery was performed to replace both cup with the friction pair and stable correctly oriented stem which finally results in lower postoperative red blood counts (erythrocytes, hemoglobin, hematocrit), as well as higher intraoperative blood loss volume and longer duration of surgical intervention if compare to the 2nd group where the stable correctly oriented femoral component was not changed. Postoperative results assessed using Harris scales and Oxford Hip Score in the comparison group were at a higher level during the whole period of follow-up. A moderate coorelation between the severity of the revision intervention and its results was detected.Conclusions: Preservation of a stable correctly oriented stem allows to reduce the severity of the revision intervention which improves the results and shortens the period of patient rehabilitation.Обоснование. Асептическая нестабильность вертлужного компонента в настоящее время занимает первое место в структуре отдаленных осложнений тотального эндопротезирования тазобедренного сустава. Основу лечения составляет замена расшатанной чашки эндопротеза и пары трения (головка-вкладыш). Тактика действий в отношении же стабильного правильно ориентированного феморального компонента до сих пор не определена, что и подтверждает актуальность исследования.Цель исследования ― сравнить эффективность тотальной замены компонентов эндопротеза и изолированной ревизии чашки эндопротеза у пациентов с асептической нестабильностью вертлужного компонента и стабильным правильно ориентированным феморальным компонентом.Методы. Представлены результаты проспективного контролируемого исследования 44 пациентов (45 ревизий) с изолированной асептической нестабильностью вертлужного компонента и стабильным правильно ориентированным феморальным компонентом, которые в зависимости от объема проведенного вмешательства были разделены на две группы. В 1-ю группу были включены 16 пациентов (16 ревизий) с тотальной ревизией компонентов эндопротеза по причине отсутствия головок под нестандартный конус ножки. Во 2-ю группу вошли 28 пациентов (29 ревизий) с изолированной заменой расшатанной чашки эндопротеза и пары трения.Результаты. В 1-й группе, где ревизионное вмешательство помимо замены нестабильной чашки эндопротеза и пары трения включало удаление и замену стабильной правильно ориентированной ножки эндопротеза, были получены более низкие послеоперационные показатели красной крови (эритроциты, гемоглобин, гематокрит), а также более высокие значения объема интраоперационной кровопотери и продолжительности оперативного вмешательства, чем во 2-й группе, где стабильный правильно ориентированный феморальный компонент сохранялся. Послеоперационные результаты, оцененные при помощи шкал Харриса и Oxford Hip Score, во 2-й группе на всех сроках наблюдения находились на более высоком уровне. Между тяжестью ревизионного вмешательства и его результатами была выявлена корреляционная связь средней силы.Заключение. Сохранение стабильного правильно ориентированного феморального компонента позволяет снизить тяжесть ревизионного вмешательства, что способствует улучшению его результатов и сокращению сроков реабилитации пациентов

Surgical Treatment Of Diaphyseal Femur Fractures

In this article advantages and disadvantages of author's transosseous osteosynthesis methods of diaphyseal femur fractures are described. Sort-term and long-term results of patients treatment with femur fractures are disscusse

Biomechanical Basis Of External Fixation In Patients With Femur Fractures

Advantages of osteosynthesis of femur fractures by means of rod type external fixation devices have been under the study. Computer modelling on the basis of methods of deformable firm body mechanics for pin and rod devices for external fixation has been performe

Topological Defects as Seeds for Eternal Inflation

We investigate the global structure of inflationary universe both by analytical methods and by computer simulations of stochastic processes in the early Universe. We show that the global structure of the universe depends crucially on the mechanism of inflation. In the simplest models of chaotic inflation the Universe looks like a sea of thermalized phase surrounding permanently self-reproducing inflationary domains. In the theories where inflation occurs near a local extremum of the effective potential corresponding to a metastable state, the Universe looks like de Sitter space surrounding islands of thermalized phase. A similar picture appears even if the state $\phi = 0$ is unstable but the effective potential has a discrete symmetry $\phi \to =-\phi$. In this case the Universe becomes divided into domains containing different phases. These domains will be separated from each other by domain walls. However, unlike ordinary domain walls, these domain walls will inflate, and their thickness will exponentially grow. In the theories with continuous symmetries inflation generates exponentially expanding strings and monopoles surrounded by thermalized phase. Inflating topological defects will be stable, and they will unceasingly produce new inflating topological defects. This means that topological defects may play a role of indestructible seeds for eternal inflation.Comment: 21 pages, 17 figures (not included), Stanford University preprint SU--ITP--94--

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Breast cancer risk genes: association analysis in more than 113,000 women

BACKGROUNDGenetic testing for breast cancer susceptibility is widely used, but for many genes, evidence of an association with breast cancer is weak, underlying risk estimates are imprecise, and reliable subtype-specific risk estimates are lacking.METHODSWe used a panel of 34 putative susceptibility genes to perform sequencing on samples from 60,466 women with breast cancer and 53,461 controls. In separate analyses for protein-truncating variants and rare missense variants in these genes, we estimated odds ratios for breast cancer overall and tumor subtypes. We evaluated missense-variant associations according to domain and classification of pathogenicity.RESULTSProtein-truncating variants in 5 genes (ATM, BRCA1, BRCA2, CHEK2, and PALB2) were associated with a risk of breast cancer overall with a P value of less than 0.0001. Protein-truncating variants in 4 other genes (BARD1, RAD51C, RAD51D, and TP53) were associated with a risk of breast cancer overall with a P value of less than 0.05 and a Bayesian false-discovery probability of less than 0.05. For protein-truncating variants in 19 of the remaining 25 genes, the upper limit of the 95% confidence interval of the odds ratio for breast cancer overall was less than 2.0. For protein-truncating variants in ATM and CHEK2, odds ratios were higher for estrogen receptor (ER)-positive disease than for ER-negative disease; for protein-truncating variants in BARD1, BRCA1, BRCA2, PALB2, RAD51C, and RAD51D, odds ratios were higher for ER-negative disease than for ER-positive disease. Rare missense variants (in aggregate) in ATM, CHEK2, and TP53 were associated with a risk of breast cancer overall with a P value of less than 0.001. For BRCA1, BRCA2, and TP53, missense variants (in aggregate) that would be classified as pathogenic according to standard criteria were associated with a risk of breast cancer overall, with the risk being similar to that of protein-truncating variants.CONCLUSIONSThe results of this study define the genes that are most clinically useful for inclusion on panels for the prediction of breast cancer risk, as well as provide estimates of the risks associated with protein-truncating variants, to guide genetic counseling. (Funded by European Union Horizon 2020 programs and others.)Molecular tumour pathology - and tumour geneticsMTG1 - Moleculaire genetica en pathologie van borstkanke