Einstein-Cartan gravity with scalar-fermion interactions

In this paper, we have considered the g-essence and its particular cases, k-essence and f-essence, within the framework of the Einstein-Cartan theory. We have shown that a single fermionic field can give rise to the accelerated expansion within the Einstein-Cartan theory. The exact analytical solution of the Einstein-Cartan-Dirac equations is found. This solution describes the accelerated expansion of the Universe with the equation of state parameter $w=-1$ as in the case of $\Lambda$CDM model.Comment: 6 pages, title is change

A Dynamical Solution to the Problem of a Small Cosmological Constant and Late-time Cosmic Acceleration

Increasing evidence suggests that most of the energy density of the universe consists of a dark energy component with negative pressure, a ``cosmological constant" that causes the cosmic expansion to accelerate. In this paper, we address the puzzle of why this component comes to dominate the universe only recently rather than at some much earlier epoch. We present a class of theories based on an evolving scalar field where the explanation is based entirely on internal dynamical properties of the solutions. In the theories we consider, the dynamics causes the scalar field to lock automatically into a negative pressure state at the onset of matter-domination such that the present epoch is the earliest possible time, consistent with nucleosynthesis restrictions, when it can start to dominate.Comment: 5 pages, 3 figure

Trans-Planckian wimpzillas

Two previously proposed conjectures--gravitational trans-Planckian particle creation in the expanding universe, and the existence of ultra-heavy stable particles with masses up to the Planck scale (wimpzillas)--are combined in a proposal for trans-Planckian particle creation of wimpzillas. This new scenario leads to a huge enhancement in their production compared to mechanisms put forward earlier. As a result, it requires the trans-Planckian particle creation parameter to be rather small to avoid overproduction of such particles, much less than that is required for observable effects in the primordial perturbation spectrum. This ensures also that wimpzillas are mainly created at the end of primordial inflation. Conditions under which trans-Planckian wimpzillas can constitute the present dark matter are determined.Comment: Replaced with the version to be published in JCAP. Division into sections introduced, discussion expanded, references added, conclusions unchange

Preheating in Derivatively-Coupled Inflation Models

We study preheating in theories where the inflaton couples derivatively to scalar and gauge fields. Such couplings may dominate in natural models of inflation, in which the flatness of the inflaton potential is related to an approximate shift symmetry of the inflaton. We compare our results with previously studied models with non-derivative couplings. For sufficiently heavy scalar matter, parametric resonance is ineffective in reheating the universe, because the couplings of the inflaton to matter are very weak. If scalar matter fields are light, derivative couplings lead to a mild long-wavelength instability that drives matter fields to non-zero expectation values. In this case however, long-wavelength fluctuations of the light scalar are produced during inflation, leading to a host of cosmological problems. In contrast, axion-like couplings of the inflaton to a gauge field do not lead to production of long-wavelength fluctuations during inflation. However, again because of the weakness of the couplings to the inflaton, parametric resonance is not effective in producing gauge field quanta.Comment: 10 pages, 9 figure

Nuevas aplicaciones de la cápsula endoscópica: PILLCAM™ ESO

ABSTRACT Capsule endoscopy has opened a new era in small bowel examination. Its indications are now welldefined and currently, wireless capsule endoscopy is considered as the first-line imaging tool for the diagnosis of small bowel diseases. ECE has been shown to be feasible, safe and a good alternative technique in patients refusing conventional endoscopy. Although results reported in both GERD and cirrhotic patients are encouraging, great differences in terms of accuracy (particularly in GERD patients) have been found in published studies. These differences have been attributed to study designs, the lack of adequate experience and inconvenience of ingestion protocols. In summary, more large-scale studies evaluating the new 14-fps capsule, adequate ECE-experience and new modified ingestion protocols are still needed

К вопросу о первичном ареале Artemisia dracunculus L.

Обсуждается флорогенезисный статус Artemisia dracunculus L. на территории Северной Америки, Западной Европы и Украины. В результате анализа имеющихся материалов расширены границы первичного ареала вида на территории Украины.The floragenesis status of Artemisia dracunculus L. on the territory of North America, Western Europe and Ukraine has been discussed. The analysis of available materials has shown that the borders of the primary natural habitat on the territory of Ukraine has been extended

Scale Invariance from Modified Dispersion Relations

In this paper, inspired by the investigations on the theory of cosmological perturbations in Ho\v{r}ava-Liftshit cosmology, we calculated the spectrum of primordial perturbation leaded by a scalar field with modified dispersion relation \omega\sim k^z/a^{p-1}, in which z is the critical exponent and p is generally not equal to z. We discussed that for fixed z, if the spectrum is required to be scale invariant, how should p depend on the background evolution. We concluded that there is always a room of parameters for the generation of scale invariant spectrum.Comment: 8 pages, 2 figure

Predictive model for the emergence of Xylotrechus arvicola (Coleoptera: Cerambycidae) in La Rioja vineyards (Spain)

Xylotrechus arvicola (Coleoptera, Cerambycidae) (Olivier) is a polyphagous borer which attacks different woody species in natural habitats in Spain. This coleopteran is also becoming a real impacting pest in several Spanish wine producing territories. Infested vines show adult exit holes, rachitic shoots, a higher incidence of wood fungal diseases and fragility. At the beginning of the 1990s, a heavy increase of infestation was observed in La Rioja vineyards, the only Qualified Guarantee of Origin Region (A.O.C.) in Spain. Due to the endophytic development of the larvae of X. arvicola, adults are the designated target for the integrated management. Therefore, the aim of the present paper was to study the flight period of the pest and to calculate the value of degree-days for the emergence of both sexes from data collected in the field during 2003-2008 in a Tempranillo cultivar in Tirgo (La Rioja). Adult emergences occurred from the end of May to mid-August and a certain degree of protandry was detected. The predictive models obtained for each year fit a sinusoidal curve in all cases, except for males in 2004, when the adjustment was polynomial. The obtained correlation coefficients were considerably high, as the value 0.99 was exceeded in 72 % of the cases. These results obtained in La Rioja vineyards suggest that control strategies aimed at the reduction of the adult population of X. arvicola in the view of the integrated management, should be performed between mid-June and the end of July.

The unification of inflation and late-time acceleration in the frame of kk-essence

By using the formulation of the reconstruction, we explicitly construct models of $k$-essence, which unify the inflation in the early universe and the late accelerating expansion of the present universe by a single scalar field. Due to the higher derivative terms, the solution describing the unification can be stable in the space of solutions, which makes the restriction for the initial condition relaxed. The higher derivative terms also eliminate tachyon. Therefore we can construct a model describing the time development, which cannot be realized by a usual inflaton or quintessence models of the canonical scalar field due to the instability or the existence of tachyon. We also propose a mechanism of the reheating by the quantum effects coming from the variation of the energy density of the scalar field.Comment: LaTeX, 13 pages, 10 figure

On a class of stable, traversable Lorentzian wormholes in classical general relativity

It is known that Lorentzian wormholes must be threaded by matter that violates the null energy condition. We phenomenologically characterize such exotic matter by a general class of microscopic scalar field Lagrangians and formulate the necessary conditions that the existence of Lorentzian wormholes imposes on them. Under rather general assumptions, these conditions turn out to be strongly restrictive. The most simple Lagrangian that satisfies all of them describes a minimally coupled massless scalar field with a reversed sign kinetic term. Exact, non-singular, spherically symmetric solutions of Einstein's equations sourced by such a field indeed describe traversable wormhole geometries. These wormholes are characterized by two parameters: their mass and charge. Among them, the zero mass ones are particularly simple, allowing us to analytically prove their stability under arbitrary space-time dependent perturbations. We extend our arguments to non-zero mass solutions and conclude that at least a non-zero measure set of these solutions is stable.Comment: 23 pages, 4 figures, uses RevTeX4. v2: Changes to accommodate added references. Statement about masses of the wormhole correcte