Technically natural dark energy from Lorentz breaking

We construct a model of dark energy with a technically natural small contribution to cosmic acceleration, i.e. this contribution does not receive corrections from other scales in the theory. The proposed acceleration mechanism appears generically in the low-energy limit of gravity theories with violation of Lorentz invariance that contain a derivatively coupled scalar field Theta. The latter may be the Goldstone field of a broken global symmetry. The model, that we call Theta-CDM, is a valid effective field theory up to a high cutoff just a few orders of magnitude below the Planck scale. Furthermore, it can be ultraviolet-completed in the context of Horava gravity. We discuss the observational predictions of the model. Even in the absence of a cosmological constant term, the expansion history of the Universe is essentially indistinguishable from that of Lambda-CDM. The difference between the two theories appears at the level of cosmological perturbations. We find that in Theta-CDM the matter power spectrum is enhanced at subhorizon scales compared to Lambda-CDM. This property can be used to discriminate the model from Lambda-CDM with current cosmological data.Comment: A few equations in the Appendix correcte

The Lorentz Integral Transform (LIT) method and its applications to perturbation induced reactions

The LIT method has allowed ab initio calculations of electroweak cross sections in light nuclear systems. This review presents a description of the method from both a general and a more technical point of view, as well as a summary of the results obtained by its application. The remarkable features of the LIT approach, which make it particularly efficient in dealing with a general reaction involving continuum states, are underlined. Emphasis is given on the results obtained for electroweak cross sections of few--nucleon systems. Their implications for the present understanding of microscopic nuclear dynamics are discussed.Comment: 83 pages, 31 figures. Topical review. Corrected typo

Primordial gravitational waves in inflationary braneworld

We study primordial gravitational waves from inflation in Randall-Sundrum braneworld model. The effect of small change of the Hubble parameter during inflation is investigated using a toy model given by connecting two de Sitter branes. We analyze the power spectrum of final zero-mode gravitons, which is generated from the vacuum fluctuations of both initial Kaluza-Klein modes and zero-mode. The amplitude of fluctuations is confirmed to agree with the four-dimensional one at low energies, whereas it is enhanced due to the normalization factor of zero-mode at high energies. We show that the five-dimensional spectrum can be well approximated by applying a simple mapping to the four-dimensional fluctuation amplitude.Comment: 16 pages, 4 figures, typos correcte

Narrowing the window for millicharged particles by CMB anisotropy

We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q\sim 10^{-6}-10^{-1} in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming Big Bang nucleosynthesis value for the baryon abundance we find that only a small fraction of cold dark matter, Omega_{mcp}h_0^2 < 0.007 (at 95% CL), may consists of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphoton millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511 keV gamma-rays from the Galactic bulge may be an indication that a (small) fraction of CDM is comprised of the millicharged particles.Comment: 10 pages, 3 figures; v2: journal version, references adde

Noether and Belinfante corrected types of currents for perturbations in the Einstein-Gauss-Bonnet gravity

In the framework of an arbitrary $D$-dimensional metric theory, perturbations are considered on arbitrary backgrounds that are however solutions of the theory. Conserved currents for perturbations are presented following two known prescriptions: canonical N{\oe}ther theorem and Belinfante symmetrization rule. Using generalized formulae, currents in the Einstein-Gauss-Bonnet (EGB) gravity for arbitrary types of perturbations on arbitrary curved backgrounds (not only vacuum) are constructed in an explicit covariant form. Special attention is paid to the energy-momentum tensors for perturbations which are an important part in the structure of the currents. We use the derived expressions for two applied calculations: a) to present the energy density for weak flat gravitational waves in $D$-dimensional EGB gravity; b) to construct the mass flux for the Maeda-Dadhich-Molina 3D radiating black holes of a Kaluza-Klein type in 6D EGB gravity.Comment: 22 pages, no figures, version accepted to CQ

Cosmological perturbations from braneworld inflation with a Gauss-Bonnet term

Braneworld inflation is a phenomenology related to string theory that describes high-energy modifications to general relativistic inflation. The observable universe is a braneworld embedded in 5-dimensional anti de Sitter spacetime. Whe the 5-dimensional action is Einstein-Hilbert, we have a Randall-Sundrum type braneworld. The amplitude of tensor and scalar perturbations from inflation is strongly increased relative to the standard results, although the ratio of tensor to scalar amplitudes still obeys the standard consistency relation. If a Gauss-Bonnet term is included in the action, as a high-energy correction motivated by string theory, we show that there are important changes to the Randall-Sundrum case. We give an exact analysis of the tensor perturbations. They satisfy the same wave equation and have the same spectrum as in the Randall-Sundrum case, but the Gauss-Bonnet change to the junction conditions leads to a modified amplitude of gravitational waves. The amplitude is no longer monotonically increasing with energy scale, but decreases asymptotically after an initial rise above the standard level. Using an approximation that neglects bulk effects, we show that the amplitude of scalar perturbations has a qualitatively similar behaviour to the tensor amplitude. In addition, the tensor to scalar ratio breaks the standard consistency relation.Comment: Minor alterations to match published versio

Consistency equations in Randall-Sundrum cosmology: a test for braneworld inflation

In the context of an inflationary Randall-Sundrum Type II braneworld (RS2) we calculate spectral indices and amplitudes of cosmological scalar and tensor perturbations, up to second order in slow-roll parameters. Under very simple assumptions, extrapolating next-order formulae from first-order calculations in the case of a de Sitter brane, we see that the degeneracy between standard and braneworld lowest-order consistency equations is broken, thus giving different signatures of early-universe inflationary expansion. Using the latest results from WMAP for estimates of cosmological observables, it is shown that future data and missions can in principle discriminate between standard and braneworld scenarios.Comment: 13 pages; v3: supersedes the published version, corrected misprint

Relationship of the White Coat Effect with Endpoints and Several Prognostic Indicators in Hypertensive Patients Treated with Regular Antihypertensive Therapy

Aim of the study was to evaluate in a prospective cohort study the relationship between the severity of the white coat effect (WHE) in patients with hypertension, who treated with regular antihypertensive therapy, and the composite endpoint, several prognostic indicators, in a routine clinical practice.Material and Methods. We analyzed the data of a prospective cohort study, which included 125 patients with hypertension who received regular antihypertensive therapy. The study consisted of three visits (baseline, 6 and 12 months) and an outcome data collection period (30.1±7.6 months of follow-up after the third visit). This study included three visits every 3 months: 1 visit – screening, ambulatory blood pressure monitoring (ABPM) session, Echo; 2 – assessment of the patient’s status and the therapy effectiveness; 3- assessment of the patient’s status, ABPM session, Echo (the total number of ABPM was 239, Echo - 240). The primary composite endpoint included death for any reason angina pectoris, transient ischemic attack, development of chronic heart failure, arterial revascularization, frequent ventricular extrasystoles, atrial fibrillation, secondary - deterioration of the cardiovascular diseases course and tertiary endpoint – deterioration of the arterial hypertension, concomitant diseases course.Results. The study involved 125 patients: 28 men (22%), 97 women (78%), mean age was 62.6±0.8 years, duration of hypertension 11.6±0.8 years, height 163.6±0.7 cm, body weight 83.1±1.4 kg. The baseline mean daytime systolic BP (SBP) was 125.1±9.8 and diastolic (DBP) – 76.1±7.0 mm Hg, age was 62.8±9.0 years, the WCE level for SBP was 16.5±1.4, for DBP 10.9±0.7 mm Hg. We identified a positive correlation between tertiary composite endpoint data and WCE: for systolic WCE (SWCE) (F = 4.7, p&lt;0.031). We found correlations between WCE and Echo parameters: 1) SWCE level had with LVMI (r = 0.16. p&lt;0.017); 2) diastolic WCE (DWCE) had negative relationship with LV contractility parameters.Conclusions. Thus, only systolic WCE level had correlation with composite endpoint data and LVMI. DWCE level had negative associations with echocardiography LV contractility parameters

Influence of Gamma-Ray Emission on the Isotopic Composition of Clouds in the Interstellar Medium

We investigate one mechanism of the change in the isotopic composition of cosmologically distant clouds of interstellar gas whose matter was subjected only slightly to star formation processes. According to the standard cosmological model, the isotopic composition of the gas in such clouds was formed at the epoch of Big Bang nucleosynthesis and is determined only by the baryon density in the Universe. The dispersion in the available cloud composition observations exceeds the errors of individual measurements. This may indicate that there are mechanisms of the change in the composition of matter in the Universe after the completion of Big Bang nucleosynthesis. We have calculated the destruction and production rates of light isotopes (D, 3He, 4He) under the influence of photonuclear reactions triggered by the gamma-ray emission from active galactic nuclei (AGNs). We investigate the destruction and production of light elements depending on the spectral characteristics of the gamma-ray emission. We show that in comparison with previous works, taking into account the influence of spectral hardness on the photonuclear reaction rates can increase the characteristic radii of influence of the gamma-ray emission from AGNs by a factor of 2-8. The high gamma-ray luminosities of AGNs observed in recent years increase the previous estimates of the characteristic radii by two orders of magnitude. This may suggest that the influence of the emission from AGNs on the change in the composition of the medium in the immediate neighborhood (the host galaxy) has been underestimated.Comment: 13 pages, 13 figures, 3 table