White dwarf constraints on dark matter particles

Matter budget in the Universe together with primordial nucleosynthesis bounds on baryonic density suggests that dark matter in galaxies should have non-baryonic nature. On the other hand, considerable agreement of a variety of astrophysical observations with standard physics can serve as a source of constraints on non-standard ideas. In this context we consider G117-B15A pulsating white dwarf for which the rate of period change of its fundamental mode has been accurately measured. This star has been claimed the most stable oscillator ever recorded in the optical band. Here we use this object to derive a bound on theories with large extra dimensions as well as to constrain supersymmetric dark matter

White dwarfs as a source of constraints on exotic physics

In this paper we briefly review main ideas underlying the constraints on exotic physics coming from Astrophysics already used by the others. Next we present a new bound coming from the White Dwarf cooling. Such stringent bound is possible due to accurate measurements offered by astroseismology. Specifically we consider the G117-B15A pulsating white dwarf (ZZ Ceti star) for which the speed of the period increase has been accurately measured for its fundamental oscillation mode. It has been claimed that this mode detected in G117-B15A is perhaps the most stable oscillation ever recorded in the optical band. Then we review our result concerning the bounds on compactification scale in the theory with large extra dimensions according to Arkani-Hamed, Dimopoulos and Dvali. Because an additional channel of energy loss (Kaluza-Klein gravitons) would speed up the cooling rate, one is able to use the aforementioned stability to derive a bound on compactification scale. We find the lower bound on compactification scale to be Ms > 14.3 TeV/c2 which is more stringent than solar or red-giant bounds, as well as the bound coming from LEP. In final section we point out that pulsating hot “pre-White Dwarf” PG 1159-035 (GW Virginis) whose oscillation period increases at the rate of the order of magnitude larger than predicted could be a promising object for further investigations

Gravitational Lenses as Standard Rulers in Cosmology

The accelerating expansion of the Universe is a great challenge for both physics and cosmology. From the observational point of view, it is crucial to have various methods to assess cosmic expansion history, which can be alternative to standard candles (SNIa in cosmological context). Strongly gravitationally lensed systems create such a new opportunity by combining stellar kinematics with lensing geometry. Using strong gravitational lenses as probes of cosmic expansion is becoming attractive in light of ongoing surveys like SLACS based on different protocols than older searches focused on potential sources. In this approach, pursued recently by the authors, strongly lensed systems with known central velocity dispersions act as “standard rulers” — Einstein radius being standardized by stellar kinematics

Constraints on Cosmic Equation of State from Joint Analysis of Standard Rulers and Standard Candles

A key issue of contemporary cosmology is the problem of currently accelerating expansion of the Universe. The nature of this phenomenon is one of the most outstanding problems of physics and astronomy today. Its origin may be attributed to either unknown exotic material component with negative pressure — so-called Dark Energy (DE), to infra red modification of gravity at cosmological scale or requires to relax the assumption of homogeneity of the Universe. The strength of modern cosmology lies in consistency across independent pieces of evidence (like e.g. CMB anisotropies, the large-scale distribution of galaxies, the observed abundances of light elements, etc.) rather than in single one, crucial experiment. In this spirit we performed a joint analysis of two dark energy models using five different tests. These tests will be called diagnostics and include the data coming from supernovae, Gamma Ray Bursts, CMB acoustic peaks, Baryon Acoustic Oscillations and strong lensing systems. Part of the diagnostics makes use of the angular diameter distance, and part of them uses the luminosity distance splitting these probes into two categories: Standard Rules and Standard Candles. It was shown that combined analysis of them had higher restrictive power in the parameter space. The best fits we obtained for the model parameters in joint analysis turned out to prefer cases effectively equivalent to CDM model. Our findings are in agreement with paralel studies performed by other authors on different sets of diagnostic probes

Distance Duality in Different Cosmological Models

At cosmological scales, one can actually measure two types of distances: luminosity distance dL and angular diameter distance dA. Within General Relativity, providing there are no processes eliminating photons from the beam, these two distances are related by the so-called distance duality relation. In this paper we used the measurements of the angular diameter distance of 38 cluster of galaxies by Bonamente et al. together with our own fits on the latest Union2 compilation of supernovae to test the distance duality relation in different cosmological models invoked to explain accelerating expansion of the Universe. Our results demonstrate that distance duality violation parameter (z) does not depend on the cosmological model assumed, but considerably depends on assumptions about mass density distribution profile of the cluster. Maximum likelihood estimates of might be interpreted as the distance duality violation. However, this effect is more pronounced for isothermal models of clusters than for the models based on hydrostatic equilibrium. This suggests that more sophisticated and accurate modeling of clusters mass density profiles is needed before the X-ray + SZ technique becomes competitive to other methods of measuring distances

Photoinduction of seed germination in Arabidopsis thaliana is modulated by phototropins

Light exposure is an important environmental factor which breaks seed dormancy in many plant species. Phytochromes have been identified as playing a crucial role in perception of the light signal that releases seed germination in Arabidopsis. Phototropins (Phot1, Phot2) are blue/UV-photoreceptors in plants which mediate phototropic responses, chloroplast relocation, hypocotyl growth inhibition and stomata opening. We studied germination under different light conditions in Arabidopsis Phot1-null and Phot2-null mutants and in a double phot1phot2 mutant. Germination of single phot1 and phot2 mutants in darkness was much lower than in wildtype (WT) seeds, whereas double phot1phot2 mutant lacking both functional phototropins germinated at frequency comparable to WT seeds, irrespective of light and temperature conditions. Light treatment of imbibed seeds was essential for effective germination of phot1, irrespective of low-temperature conditioning. In contrast, cold stratification promoted dark germination of phot2 seeds after imbibition in dim light. Low germination frequency of phot1 seeds under low light intensity suggests that the presence of functional Phot1 might be crucial for effective germination at these conditions. The lower germination frequency of phot2 seeds under continuous light suggests that Phot2 might be responsible for stimulating germination of seeds exposed to direct daylight. Thus, the phototropin system may cooperate with phytochromes regulating the germination competence of seeds under different environmental conditions

Variations in xanthophyll composition in etiolated seedlings of Arabidopsis thaliana correlate with protochlorophyllide accumulation

Protochlorophyllide (Pchlide) accumulation and xantophyll composition were studied in 5-day old etiolated seedlings of three ecotypes of Arabidopsis thaliana: Columbia (Col-0), Landsberg erecta (Ler) and Wassiliewska (Ws). The total Pchlide level as measured by fluorescence spectroscopy varied significantly between ecotypes. A rapid HPLC method revealed quantitative differences in carotenoid composition. It was found that in the Ler ecotype any enhanced accumulation of Pchlide correlates with an increased level of lutein, suggesting the role of enzymes involved in lutein synthesis in cross-regulation between chlorophyll and carotenoid biosynthetic pathways. The function of the dark-accumulated carotenoid pool in seedling de-etiolation is discussed

Carboxylated and undercarboxylated osteocalcin in metabolic complications of human obesity and prediabetes

Background Carboxylated osteocalcin (Gla‐OC) participates in bone remodeling, whereas the undercarboxylated form (Glu‐OC) takes part in energy metabolism. This study was undertaken to compare the blood levels of Glu‐OC and Gla‐OC in nonobese, healthy obese, and prediabetic volunteers and correlate it with the metabolic markers of insulin resistance and early markers of inflammation. Methods Nonobese (body mass index [BMI] <30 kg/m2 ; n = 34) and obese subjects (30 <BMI <40 kg/m2 ; n = 98), both sexes, aged 25 to 65 years, were divided into healthy control, normal weight subjects, healthy obese, and obese with biochemical markers of prediabetes. The subgroups with obesity and low or high Gla‐OC or Glu‐OC were also considered for statistical analysis. After 2 weeks of diet standardization, venous blood was sampled for the determination of Gla‐OC, Glu‐OC, lipid profile, parameters of inflammation (hsCRP, interleukin 6, sE‐selectin, sPECAM‐1, and monocyte chemoattractant protein 1), and adipokines (leptin, adiponectin, visfatin, and resistin). Results Gla‐OC in obese patients was significantly lower compared to nonobese ones (11.36 ± 0.39 vs 12.69 ± 0.90 ng/mL, P = .048) and weakly correlated with hsCRP (r = −0.18, P = .042), visfatin concentration (r = −0.19, P = .033), and BMI (r = −0.17, P = .047). Glu‐OC was negatively associated with fasting insulin levels (r = −0.18, P = .049) and reduced in prediabetic individuals compared with healthy obese volunteers (3.04 ± 0.28 vs 4.48 ± 0.57, P = .025). Conclusions Decreased blood concentration of Glu‐OC may be a selective early symptom of insulin resistance in obesity, whereas the decreased level of Gla‐OC seems to be associated with the appearance of early markers of low grade inflammation accompanying obesity