Nonlocal Gravitational Models and Exact Solutions

A nonlocal gravity model with a function $f(\Box^{-1} R)$, where $\Box$ is the d'Alembert operator, is considered. The algorithm, allowing to reconstruct $f(\Box^{-1} R)$, corresponding to the given Hubble parameter and the state parameter of the matter, is proposed. Using this algorithm, we find the functions $f(\Box^{-1} R)$, corresponding to de Sitter solutions.Comment: 5 pages, v2: refs. added, to appear in the proceedings of the International Workshop "Supersymmetries and Quantum Symmetries" (SQS'2011), Dubna, Russia, July 18-23, 2011, http://theor.jinr.ru/sqs/2011

Changing trends in pediatric tonsil surgery

Objectives: We analyzed trends in tonsil surgery over a 10-year period in a single tertiary care hospital and evaluated the effects of these changes on use of hospital services and healthcare costs. Methods: This was a retrospective cohort study based on data from databases at the Department of Otorhinolaryngology, Helsinki University Hospital, Helsinki, Finland. Children under 16 years of age with tonsillectomy (TE) or tonsillotomy (TT) performed during 2007-2016 were included in the study. Results: In 10 years, 4979 tonsil surgeries were performed on 4951 children: TE in 3170 (64%) and TT in 1781 (36%) children. The total number of tonsil surgeries stayed nearly constant. TT operations commenced in the study hospital in 2009 and from 2012 onwards have been more common than TE procedures. Altogether 279 patients visited the emergency department because of complications; TE patients had 9.0 visits/100 surgeries and TT patients 1.8 visits/100 surgeries. The most common complication was postoperative hemorrhage: 200 cases (6.3%) in the TE group and 11 cases (0.6%) in the TT group. During the two-year follow-up after tonsil surgery the total costs of healthcare services were significantly lower in the TT group than in the TE group. Conclusion: Considerable changes have occurred in tonsil surgery in children during the 10-year study period; TT is today performed more often than TE. As a consequence, complications, readmissions to hospital, and number of patients treated in the operating room because of postoperative hemorrhage have decreased, lowering the costs of healthcare.Peer reviewe

Monopolar tonsillotomy versus cold dissection tonsillectomy in children : Prospective study on postoperative recovery

Objectives: To compare postoperative self-reported recovery results with monopolar tonsillotomy and cold dissection tonsillectomy in children. To evaluate the feasibility of the monopolar technique in tonsillotomy. Methods: Children Results: Altogether 166 patients were recruited; 103 (62%) returned the questionnaire. The first pain-free day with tonsillotomy was day 5 and with tonsillectomy day 11. After tonsillotomy, patients returned to normal activities faster, e.g. they were able to eat normally 6.5 days earlier than tonsillectomy patients. During the first postoperative week weight dropped after tonsillectomy, but not after tonsillotomy. The length of home care was 6 days with tonsillotomy and 10 days with tonsillectomy. The incidence of postoperative hemorrhage (including minor bleedings at home) was 14% after tonsillotomy and 32% after tonsillectomy. Hemorrhages needing interventions were 0% with tonsillotomy and 2% with tonsillectomy. Conclusion: Children operated on with monopolar tonsillotomy recovered faster and had less postoperative hemorrhage than those undergoing tonsillectomy. They were able to return earlier to daycare/school and their caregivers back to work. Recovery results with monopolar tonsillotomy were equal to other tonsillotomy techniques reported in the literature, hence the monopolar technique can be considered an alternative method to perform tonsillotomy.Peer reviewe

Palatini formulation of modified gravity with a nonminimal curvature-matter coupling

We derive the field equations and the equations of motion for massive test particles in modified theories of gravity with an arbitrary coupling between geometry and matter by using the Palatini formalism. We show that the independent connection can be expressed as the Levi-Civita connection of an auxiliary, matter Lagrangian dependent metric, which is related with the physical metric by means of a conformal transformation. Similarly to the metric case, the field equations impose the non-conservation of the energy-momentum tensor. We derive the explicit form of the equations of motion for massive test particles in the case of a perfect fluid, and the expression of the extra-force is obtained in terms of the matter-geometry coupling functions and of their derivatives. Generally, the motion is non-geodesic, and the extra force is orthogonal to the four-velocity.Comment: 7 pages, no figures; v2, revised and corrected version; new Section adde

Primordial statistical anisotropy generated at the end of inflation

We present a new mechanism for generating primordial statistical anisotropy of curvature perturbations. We introduce a vector field which has a non-minimal kinetic term and couples with a waterfall field in hybrid inflation model. In such a system, the vector field gives fluctuations of the end of inflation and hence induces a subcomponent of curvature perturbations. Since the vector has a preferred direction, the statistical anisotropy could appear in the fluctuations. We present the explicit formula for the statistical anisotropy in the primordial power spectrum and the bispectrum of curvature perturbations. Interestingly, there is the possibility that the statistical anisotropy does not appear in the power spectrum but does appear in the bispectrum. We also find that the statistical anisotropy provides the shape dependence to the bispectrum.Comment: 9 pages, This version supersedes the JCAP version. Minor revision

Cosmology of a Scalar Field Coupled to Matter and an Isotropy-Violating Maxwell Field

Motivated by the couplings of the dilaton in four-dimensional effective actions, we investigate the cosmological consequences of a scalar field coupled both to matter and a Maxwell-type vector field. The vector field has a background isotropy-violating component. New anisotropic scaling solutions which can be responsible for the matter and dark energy dominated epochs are identified and explored. For a large parameter region the universe expands almost isotropically. Using that the CMB quadrupole is extremely sensitive to shear, we constrain the ratio of the matter coupling to the vector coupling to be less than 10^(-5). Moreover, we identify a large parameter region, corresponding to a strong vector coupling regime, yielding exciting and viable cosmologies close to the LCDM limit.Comment: Refs. added, some clarifications. Published in JHEP10(2012)06

Initial Conditions for Vector Inflation

Recently, a model of inflation using non-minimally coupled massive vector fields has been proposed. For a particular choice of non-minimal coupling parameter and for a flat FRW model, the model is reduced to the model of chaotic inflation with massive scalar field. We study the effect of non-zero curvature of the universe on the onset of vector inflation. We find that in a curved universe the dynamics of vector inflation can be different from chaotic inflation, and the fraction of the initial conditions leading to inflationary solutions is reduced compared with the chaotic inflation case.Comment: 12 pages, 5 figures, version to be published in JCA

Power Asymmetry in Cosmic Microwave Background Fluctuations from Full Sky to Sub-degree Scales: Is the Universe Isotropic?

We repeat and extend the analysis of Eriksen et al 2004 and Hansen et al 2004 testing the isotropy of the Cosmic Microwave Background (CMB) fluctuations. We find that the hemispherical power asymmetry previously reported for the largest scales l=2-40 extend to much smaller scales. In fact, for the full multipole range l=2-600, significantly more power is found in the hemisphere centered at (theta=107 deg., phi=226 deg.) in galactic co-latitude and longitude than in the opposite hemisphere consistent with the previously detected direction of asymmetry for l=2-40. We adopt a model selection test where the direction and amplitude of asymmetry as well as the multipole range are free parameters. A model with an asymmetric distribution of power for l=2-600 is found to be preferred over the isotropic model at the 0.4% significance level taking into account the additional parameters required to describe it. A similar direction of asymmetry is found independently in all six subranges of 100 multipoles between l=2-600 and none of our 9800 isotropic simulated maps show a similarly consistent direction of asymmetry over such a large multipole range. No known systematic effects or foregrounds are found to be able to explain the asymmetry.Comment: Submitted to Ap