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Cosmography, as an integral branch of cosmology, strives to characterize the Universe without relying on pre-determined cosmological models. This model-independent approach utilizes Taylor series expansions around the current epoch, providing a direct correlation with cosmological observations and the potential to constrain theoretical models. Various observable quantities in cosmology can be described as different combinations of cosmographic parameters. Furthermore, one can apply cosmography to models with a varying speed of light. In this case, the Hubble parameter can be expressed by the same combination of cosmographic parameters for both the standard model and varying speed-of-light models. However, for the luminosity distance, the two models are represented by different combinations of cosmographic parameters. Hence, luminosity distance might provide a method to constrain the parameters in varying speed-of-light models. [ABSTRACT FROM AUTHOR]

In this study, our main purpose is to study a model which is homogenous and anisotropic describing early stage of Universe in non-minimally coupled scalar theory. It is quite interesting to study a model describing early stage in modified theory which is related to scalar field. In this context, we introduced Kantowski–Sachs metric for perfect fluid in non-minimally coupled scalar theory. Exact solution of field equations is attained for f (R , ϕ) = (1 + ξ η 2 ϕ 2) R model. Matter distributions for radiation, cosmic string and cosmological constant are investigated for constructed model. For different selections of arbitrary constants, Kantowski–Sachs model shows three different behaviors related with Hubble parameter and deceleration parameter. Also, some observational parameters, such as luminosity distance, angular diameter distance and distance modulus, are obtained for Kantowski–Sachs Universe. Lastly, we get Statefinder parameters for the model. All properties of constructed model are discussed from a physical and geometric point of view. [ABSTRACT FROM AUTHOR]

According to a new tired-light cosmological model, where H (z) = H 0 (1 + z) , the number density of galaxies has been nearly constant over the last 10 Gyr, at least, meaning that, as far as galaxy counts are concerned, the Universe has been stationary. In this context, an analysis of the luminosity distances of quasars and supernovae Ia shows that the Universe is far from being as transparent as assumed nowadays, the photon lifetime along the line-of-sight being one third of the Hubble time. Such a "low" value could mean that there are huge amounts of grey dust in the inter galactic medium, that have so far escaped detection. It could also be a signature of "new physics," namely, a consequence of the decay of photons into lighter particles. The tired-light model advocated in this study would be falsified if, for instance, the time-dilation of remote events was shown to have a general character, that is, if it were definitely observed for phenomena other than the light curves of supernovae Ia. On the other hand, further developments are needed in order to turn this model into an actual cosmology. In particular, the physical origin of the current stability of the Universe on galactic scales remains to be identified. [ABSTRACT FROM AUTHOR]

The luminosity distance d L is possibly the most important distance scale in cosmology and therefore accurate and efficient methods for its computation is paramount in modern precision cosmology. Yet in most cosmological models the luminosity distance cannot be expressed by a simple analytic function in terms of the redshift z and the cosmological parameters, and is instead represented in terms of an integral. Although one can revert to numerical integration techniques utilizing quadrature algorithms to evaluate such an integral, the high accuracy required in modern cosmology makes this a computationally demanding process. In this paper, we use the Parker–Sochacki method (PSM) to generate a series approximate solution for the luminosity distance in spatially flat Λ CDM cosmology by solving a polynomial system of nonlinear differential equations. When compared with other techniques proposed recently, which are mainly based on the Padé approximant, the expression for the luminosity distance obtained via the PSM leads to a significant improvement in the accuracy in the redshift range 0 ≤ z ≤ 2.5 . Moreover, we show that this technique can be easily applied to other more complicated cosmological models, and its multistage approach can be used to generate analytic approximations that are valid on a wider redshift range. [ABSTRACT FROM AUTHOR]

In this paper, we considered the study of Friedmann–Robertson–Walker (FRW) model in the framework of f (Q , T) gravity, an extension of symmetric teleparallel gravity, recently defined by Xu et al. [ f (Q , T) gravity, Eur. Phys. J. C 79 (2019) 708]. The nonlinear model f (Q , T) = − α Q − β T 2 , where α > 0 and β > 0 are constants, is taken into account. The equation of state of perfect fluid is assumed and 31 points of Hubble data are used to constrain the value of model parameter. To explore the evolution of the universe, the numerical solutions of cosmological implications, such as Hubble parameter, deceleration parameter, apparent magnitude and luminosity distance, are determined and the energy conditions are examined. The theoretical results of Hubble parameter are compared with Λ CDM model. Further, 57 Supernova data (42 from Supernova cosmology project and 15 from Calán/Tolono supernova survey) are also used to have consistent results of apparent magnitude and luminosity distance. [ABSTRACT FROM AUTHOR]

The luminosity distance dL is possibly the most important distance scale in cosmology and therefore accurate and efficient methods for its computation is paramount in modern precision cosmology. Yet in most cosmological models the luminosity distance cannot be expressed by a simple analytic function in terms of the redshift z and the cosmological parameters, and is instead represented in terms of an integral. Although one can revert to numerical integration techniques utilizing quadrature algorithms to evaluate such an integral, the high accuracy required in modern cosmology makes this a computationally demanding process. In this paper, we use the Parker–Sochacki method (PSM) to generate a series approximate solution for the luminosity distance in spatially flat ΛCDM cosmology by solving a polynomial system of nonlinear differential equations. When compared with other techniques proposed recently, which are mainly based on the Padé approximant, the expression for the luminosity distance obtained via the PSM leads to a significant improvement in the accuracy in the redshift range 0≤z≤2.5. Moreover, we show that this technique can be easily applied to other more complicated cosmological models, and its multistage approach can be used to generate analytic approximations that are valid on a wider redshift range.

A brief overview of the history of the origin and development of the cosmological distance scale based on redshift is given. Statistical aspects of the problem of calibration of scales of this type are considered on the analogy with the problems of calibration of measuring instruments. An analysis is presented of the first data on the basis of which the "accelerating expansion of the Universe" was detected. The metrological consequences of anisotropy for distance scale are analyzed. [ABSTRACT FROM AUTHOR]

Abstract By using the supernovae type Ia (SNIa) data we study influence of the anisotropy (although low) on the evolution of the universe and compare ΛCDM model with 6 representative parametrizations of the recent Hubble expansion history H (z). To compare these models we use the maximum likelihood method for find that the best fit dynamical w (z) and q (z) obtained from the SNIa dataset. We have performed a comparative analysis of t hree SNIa datasets such as, the 194 SNIa (0 ≤ z ≤ 1.75), the Supernova Legacy Survey (SNLS) dataset (238 data points 0.15 < z < 1.1) a nd the most recent Pantheon sample (1048 data points 0.01 < z < 2.3). In particular we find the best fit value of ΛCDM model Ω σ 0 = 0.013 ± 0.008 , χ min 2 = 197.56 with 194 SNIa, Ω σ 0 = − 0.003 ± 0.033 , χ min 2 = 230.656 with 238 SNLS a nd Ω σ 0 = 0.011 ± 0.013 , χ min 2 = 1012.55 w ith 1048 Pantheon sample. The analysis shows that by considering the anisotropy, it leads to more best fit parameters in all models (except of SCDM) with SNIa data. We also use two statistical tests such as the usual χ min 2 / d o f and p-test to compare different dark energy models. According to both statistical tests and considering anisotropy, the ΛCDM model that is providing the best fit to ΛCDM of FRW model. An even better fit would result with an optimization of the data using effects of anisotropy from the beginning. [ABSTRACT FROM AUTHOR]

In the present paper, the work of Moreas et al. [P. H. R. S. Moraes, G. Ribeiro and R. A. C. Correa, A transition from a decelerated to an accelerated phase of the universe expansion from the simplest non-trivial polynomial function of T in the f (R , T) formalism, Astrophys. Space Sci.361 (2016) 227–231] is extended to study the FRW model in f (R , T) gravity. The expressions for deceleration and Hubble parameters are determined in terms of redshift. The age of the universe is established using 4 2 high-redshift type Ia supernovae data from the Supernova cosmology project and 15 low-redshift type Ia supernovae data from the Calán/Tolono Supernova survey [S. Permutter et al., Measurements of Omega and Lambda from 42 High-Redshift Supernovae, Astrophys. J.517 (1999) 565–585]. For these redshifts, the data of observed apparent magnitude and luminosity distance are used for the comparison with the obtained theoretical values. [ABSTRACT FROM AUTHOR]

The 194 supernova Ia data and the effect of anisotropy are combined to reconstruct the dark energy equation of state parameter w (z) and the deceleration parameter q (z). Using the supernovae type Ia data, we evaluate the anisotropy effects (although low) on dark energy parametrization w = w 0 + w 1 z / (1 + z) and we compare the results with Λ CDM model. Present supernova observations are analyzed using a standard χ 2 method and the minimal χ 2 values obtained for each model are compared. We confirm the difficulty of discriminating between these models using present SNIa data only. By means of the maximum likelihood method, we find that the best-fit dynamical w (z) and q (z) parameters (w 0 , w 1) are obtained from the SNIa dataset. In particular, we find the best-fit values of Λ CDM model ( Ω σ 0 = 0.013, χ min 2 = 197.559) for Ω m 0 = 0.3 and ( Ω σ 0 = 0.02, χ min 2 = 196.983) for Ω m 0 = 0.27. Finally, we found that the presence of anisotropy is confirmed in mentioned models via SNIa dataset. [ABSTRACT FROM AUTHOR]

The metal-poor subpopulation of globular cluster (GC) systems exhibits a correlation between the GC average colour and luminosity, especially in those systems associated with massive elliptical galaxies. More luminous (more massive) GCs are typically redder and hence more metal-rich. This 'blue tilt' is often interpreted as a mass–metallicity relation stemming from GC self-enrichment, whereby more massive GCs retain a greater fraction of the enriched gas ejected by their evolving stars, fostering the formation of more metal-rich secondary generations. We examine the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) simulations of the formation and evolution of galaxies and their GC populations, and find that their GCs exhibit a colour–luminosity relation similar to that observed in local galaxies, without the need to invoke mass-dependent self-enrichment. We find that the blue tilt is most appropriately interpreted as a dearth of massive, metal-poor GCs: the formation of massive GCs requires high interstellar gas surface densities, conditions that are most commonly fostered by the most massive, and hence most metal-rich, galaxies, at the peak epoch of GC formation. The blue tilt is therefore a consequence of the intimate coupling between the small-scale physics of GC formation and the evolving properties of interstellar gas hosted by hierarchically assembling galaxies. [ABSTRACT FROM AUTHOR]

We present two new NuSTAR observations of the narrow-line Seyfert 1 (NLS1) galaxy Mrk 766 and give constraints on the two scenarios previously proposed to explain its spectrum and that of other NLS1s: relativistic reflection and partial covering. The NuSTAR spectra show a strong hard (>15  keV) X-ray excess, while simultaneous soft X-ray coverage of one of the observations provided by XMM–Newton constrains the ionized absorption in the source. The pure reflection model requires a black hole of high spin (a > 0.92) viewed at a moderate inclination ($$i=46_{-4}^{+1}\, ^\circ$$). The pure partial covering model requires extreme parameters: the cut-off of the primary continuum is very low ($$22_{-5}^{+7}$$  keV) in one observation and the intrinsic X-ray emission must provide a large fraction (75 per cent) of the bolometric luminosity. Allowing a hybrid model with both partial covering and reflection provides more reasonable absorption parameters and relaxes the constraints on reflection parameters. The fractional variability reduces around the iron K band and at high energies including the Compton hump, suggesting that the reflected emission is less variable than the continuum. [ABSTRACT FROM AUTHOR]

The cosmic distance duality relation (DDR), which connects the angular diameter distance and luminosity distance through a simple formula DA ($$z$$)(1 + $$z$$)2/ DL ($$z$$) ≡ 1, is an important relation in cosmology. Therefore, testing the validity of DDR is of great importance. In this paper, we test the possible violation of DDR using the available local data including type Ia supernovae (SNe Ia), galaxy clusters, and baryon acoustic oscillations (BAO). We write the modified DDR as DA ($$z$$)(1 + $$z$$)2/ DL ($$z$$) = η($$z$$), and consider two different parameterizations of η($$z$$), namely η1($$z$$) = 1 + η0 $$z$$ and η2($$z$$) = 1 + η0 $$z$$ /(1 + $$z$$). The luminosity distance from SNe Ia are compared with the angular diameter distance from galaxy clusters and BAO at the same redshift. Two different cluster data are used here, i.e. elliptical clusters and spherical clusters. The parameter η0 is obtained using the Markov chain Monte Carlo methods. It is found that η0 can be strictly constrained by the elliptical clusters + BAO data, with the best-fitting values η0 = −0.04 ± 0.12 and η0 = −0.05 ± 0.22 for the first and second parametrizations, respectively. However, the spherical clusters + BAO data couldn't strictly constrain η0 due to the large intrinsic scatter. In any case studied here, no evidence for the violation of DDR is found. [ABSTRACT FROM AUTHOR]

We report the results of our spectrophotometric monitoring campaign for AT 2017be in NGC 2537. Its light curve reveals a fast rise to an optical maximum, followed by a plateau lasting about 30 d, and finally a fast decline. Its absolute peak magnitude (Mr  ≃ −12 mag) is fainter than that of core-collapse supernovae, and is consistent with those of supernova impostors and other intermediate-luminosity optical transients. The quasi-bolometric light-curve peaks at ∼2 × 1040 erg s−1, and the late-time photometry allows us to constrain an ejected 56Ni mass of ∼8 × 10−4 M⊙. The spectra of AT 2017 be show minor evolution over the observational period, a relatively blue continuum showing at early phases, which becomes redder with time. A prominent H α emission line always dominates over other Balmer lines. Weak Fe  ii features, Ca  ii H&K, and the Ca ii NIR triplet are also visible, while P-Cygni absorption troughs are found in a high-resolution spectrum. In addition, the [Ca  ii ] λλ7291, 7324 doublet is visible in all spectra. This feature is typical of intermediate-luminosity red transients (ILRTs), similar to SN 2008S. The relatively shallow archival Spitzer data are not particularly constraining. On the other hand, a non-detection in deeper near-infrared HST images disfavours a massive Luminous Blue Variable eruption as the origin for AT 2017be. As has been suggested for other ILRTs, we propose that AT 2017be is a candidate for a weak electron-capture supernova explosion of a superasymptotic giant branch star, still embedded in a thick dusty envelope. [ABSTRACT FROM AUTHOR]

We examine how the various observable statistical properties of the fast radio burst (FRB) population relate back to their fundamental physical properties in a model-independent manner. We analyse the flux density and fluence distributions of FRBs as a tool to investigate their luminosity distance distribution and the evolution of their prevalence throughout cosmic history. We examine in detail particular scenarios in which the burst population follows some power of the cosmic star formation rate. FRBs present an important additional measurable over source counts of existing cosmological populations, namely the dispersion measure. Based on the known redshift of FRB121102 (the repeater) we expect at least 50 per cent of the dispersion measure to be attributable to the intergalactic medium and hence it can be used as a proxy for distance. We develop the framework to interpret the dispersion measure distribution, and investigate how the effect of Helium reionization in the intergalactic medium is evident in this distribution. Examination of existing data suggests that the FRB luminosity function is flatter than a critical slope, making FRBs easily detectable to large distances; in this regime the reduction in flux density with distance is outweighed by the increase in the number of bright bursts within the search volume. [ABSTRACT FROM AUTHOR]

The STAR experiment at RHIC has been taking data since 2000. During that time, new detectors have been added, RHIC luminosity has increased, and STAR’s physics goals have become more focused. The Trigger System has evolved in parallel to be able to provide more precise triggering capabilities at higher rates. In this article the major improvements to the STAR Trigger are described, along with the future upgrade path. [ABSTRACT FROM AUTHOR]

We update our previous search for trapped magnetic monopoles in LHC Run 2 using nearly six times more integrated luminosity and including additional models for the interpretation of the data. The MoEDAL forward trapping detector, comprising 222 kg of aluminium samples, was exposed to 2.11 fb −1 of 13 TeV proton–proton collisions near the LHCb interaction point and analysed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges equal to the Dirac charge or above are excluded in all samples. The results are interpreted in Drell–Yan production models for monopoles with spins 0, 1/2 and 1: in addition to standard point-like couplings, we also consider couplings with momentum-dependent form factors. The search provides the best current laboratory constraints for monopoles with magnetic charges ranging from two to five times the Dirac charge. [ABSTRACT FROM AUTHOR]

The recent analysis of low-redshift supernovae (SN) has increased the apparent tension between the value of estimated from low and high redshift observations such as the cosmic microwave background (CMB) radiation. At the same time other observations have provided evidence of the existence of local radial inhomogeneities extending in different directions up to a redshift of about . About of the Cepheids used for SN calibration are directly affected because they are located along the directions of these inhomogeneities. We compute with different methods the effects of these inhomogeneities on the low-redshift luminosity and angular diameter distance using an exact solution of the Einstein's equations, linear perturbation theory and a low-redshift expansion. We confirm that at low redshift the dominant effect is the nonrelativistic Doppler redshift correction, which is proportional to the volume averaged density contrast and to the comoving distance from the center. We derive a new simple formula relating directly the luminosity distance to the monopole of the density contrast, which does not involve any metric perturbation. We then use it to develop a new inversion method to reconstruct the monopole of the density field from the deviations of the redshift uncorrected observed luminosity distance respect to the CDM prediction based on cosmological parameters obtained from large scale observations. The inversion method confirms the existence of inhomogeneities whose effects were not previously taken into account because the [G. Lavaux and M. J. Hudson, Mon. Not. R. Astron. Soc. 416 (2011) 2840] density field maps used to obtain the peculiar velocity [J. Carrick et al., Mon. Not. R. Astron. Soc. 450 (2015) 317] for redshift correction were for , which is not a sufficiently large scale to detect the presence of inhomogeneities extending up to . The inhomogeneity does not affect the high redshift luminosity distance because the volume averaged density contrast tends to zero asymptotically, making the value of obtained from CMB observations insensitive to any local structure. The inversion method can provide a unique tool to reconstruct the density field at high redshift where only SN data is available, and in particular to normalize correctly the density field respect to the average large scale density of the Universe. [ABSTRACT FROM AUTHOR]

The formation history of giant planets determines their primordial structure and consequent evolution. We simulate various formation paths of Jupiter to determine its primordial entropy, and find that a common outcome is for proto-Jupiter to have non-convective regions in its interior. We use planet formation models to calculate how the entropy and post-formation luminosity depend on model properties such as the solid accretion rate and opacity, and show that the gas accretion rate and its time evolution play a key role in determining the entropy profile. The predicted luminosity of Jupiter shortly after formation varies by a factor of 2-3 for different choices of model parameters. We find that entropy gradients inside Jupiter persist for ~10Myr after formation. We suggest that these gradients should be considered together with heavy-element composition gradients when modelling Jupiter's evolution and internal structure. [ABSTRACT FROM AUTHOR]

Understanding Lyα emitting galaxies (LAEs) can be a key to reveal cosmic reionization and galaxy formation in the early Universe. Based on halo merger trees and Lyα radiation transfer calculations, we model redshift evolution of LAEs and their observational properties at z ≥ 6. We consider ionized bubbles associated with individual LAEs and IGM (integer-galactic medium) transmission of Lyα photons. We find that Lyα luminosity tightly correlates with halo mass and stellar mass, while the relation with star formation rate has a large dispersion. Comparing our models with the observed luminosity function by Konno et al., we suggest that LAEs at z ~ 7 have galactic wind of Vout ... 100 kms-1 and HI column density of NHI 1020 cm-2. Number density of bright LAEs rapidly decreases as redshift increases, due to both lower star formation rate and smaller HII bubbles. Our model predicts future wide deep surveys with next-generation telescopes, such as James Webb Space Telescope, European Extremely Large Telescope, and ThirtyMetre Telescope, can detect LAEs at z~10 with a number density of nLAE ~ a few x 10-6 Mpc-3 for the ?ux sensitivity of 10-18 erg cm-2 S-1. When giant HII bubbles are formed by clustering LAEs, the number density of observable LAEs can increase by a factor of few. By combining these surveys with future 21-cm observations, it could be possible to detect both LAEs with LLyα ... 1042 erg s-1 and their associated giant HII bubbles with the size ... 250 kpc at z ~ 10. [ABSTRACT FROM AUTHOR]

We present the results of an outflow and infall survey towards a distance-limited sample of 31 massive star-forming regions drawn from the Red MSX source (RMS) survey. The presence of young, active outflows is identified from SiO (8–7) emission and the infall dynamics are explored using HCO+/H13CO+ (4–3) emission. We investigate if the infall and outflow parameters vary with source properties, exploring whether regions hosting potentially young active outflows show similarities or differences with regions harbouring more evolved, possibly momentum-driven, 'fossil' outflows. SiO emission is detected towards approximately 46 per cent of the sources. When considering sources with and without an SiO detection (i.e. potentially active and fossil outflows, respectively), only the 12CO outflow velocity shows a significant difference between samples, indicating SiO is more prevalent towards sources with higher outflow velocities. Furthermore, we find the SiO luminosity increases as a function of the Herschel 70   $\mu$ m to WISE 22  $\mu$ m flux ratio, suggesting the production of SiO is prevalent in younger, more embedded regions. Similarly, we find tentative evidence that sources with an SiO detection have a smaller bolometric luminosity-to-mass ratio, indicating SiO (8–7) emission is associated with potentially younger regions. We do not find a prevalence towards sources displaying signatures of infall in our sample. However, the higher energy HCO+ transitions may not be the best suited tracer of infall at this spatial resolution in these regions. [ABSTRACT FROM AUTHOR]

Waveforms of gravitational waves provide information about a variety of parameters for the binary system merging. However, standard calculations have been performed assuming a FLRW universe with no perturbations. In reality this assumption should be dropped: we show that the inclusion of cosmological perturbations translates into corrections to the estimate of astrophysical parameters derived for the merging binary systems. We compute corrections to the estimate of the luminosity distance due to velocity, volume, lensing and gravitational potential effects. Our results show that the amplitude of the corrections will be negligible for current instruments, mildly important for experiments like the planned DECIGO, and very important for future ones such as the Big Bang Observer. [ABSTRACT FROM AUTHOR]

The recent Advanced LIGO detections of coalescing black hole binaries (BHBs) imply a large population of such systems emitting at milli-Hz frequencies, accessible to the Laser Interferometer Space Antenna (LISA). We show that these systems provide a new class of cosmological standard sirens.Direct LISA luminosity distance -Dl - measurements, combined with the inhomogeneous redshift - z - distribution of possible host galaxies provide an effective way to populate the Dl-z diagram at z < 0.1, thus allowing a precise local measurement of the Hubble expansion rate. To be effective, the method requires a sufficiently precise LISA distance determination and sky localization of a sizeable number of BHBs, which is best achieved for a six-link detector configuration. We find that, for a BHB population consistent with current fiducial LIGO rates, the Hubble constant H0 can be determined at the ~5 per cent and ~2 per cent level (68 per cent confidence), assuming two and five million kilometre armlength, respectively. [ABSTRACT FROM AUTHOR]

We introduce a new test to study the cosmological principle with galaxy clusters. Galaxy clusters exhibit a tight correlation between the luminosity and temperature of the X-ray-emitting intracluster medium. While the luminosity measurement depends on cosmological parameters through the luminosity distance, the temperature determination is cosmology-independent. We exploit this property to test the isotropy of the luminosity distance over the full extragalactic sky, through the normalization a of the LX-T scaling relation and the cosmological parameters Ωm and H0. To this end, we use two almost independent galaxy cluster samples: the ASCA Cluster Catalog (ACC) and the XMM Cluster Survey (XCS-DR1). Interestingly enough, these two samples appear to have the same pattern for a with respect to the Galactic longitude. More specifically, we identify one sky region within l ∼ (-15°; 90°) (Group A) that shares very different best-fit values for the normalization of the LX-T relation for both ACC and XCS-DR1 samples. We use the Bootstrap and Jackknife methods to assess the statistical significance of these results. We find the deviation of Group A, compared to the rest of the sky in terms of a, to be ∼2:7σ for ACC and ∼3:1σ for XCS-DR1. This tension is not significantly relieved after excluding possible outliers and is not attributed to different redshift (z), temperature (T), or distributions of observable uncertainties. Moreover, a redshift conversion to the cosmic microwave background (CMB) frame does not have an important impact on our results. Using also the HIFLUGCS sample, we show that a possible excess of cool-core clusters in this region, is not able to explain the obtained deviations. Furthermore, we tested for a dependence of the results on supercluster environment, where the fraction of disturbed clusters might be enhanced, possibly affecting the LX-T relation. We indeed find a trend in the XCS-DR1 sample for supercluster members to be underluminous compared to field clusters. However, the fraction of supercluster members is similar in the different sky regions, so this cannot explain the observed differences, either. Constraining Ωm and H0 via the redshift evolution of LX-T and the luminosity distance via the flux-luminosity conversion, we obtain approximately the same deviation amplitudes as for a. It is interesting that the general observed behavior of Ωm for the sky regions that coincide with the CMB dipole is similar to what was found with other cosmological probes such as supernovae Ia. The reason for this behavior remains to be identified. [ABSTRACT FROM AUTHOR]

We use a sample of 808 quasars selected by Risaliti and Lusso to estimate two important cosmological parameters: the percentage of matter in the Universe Ωm and the Hubble constant. The method is based on an auxiliary experimental correlation between the luminosity of quasars in the Xray band and UV band in the form log LX = β + γ log LUV. For the flat ΛCDM model our fit gives Ωm = 0.21 ± 0.12. Our main results are the following. The fraction of matter (baryonic + dark) contained in the Universe is 21% according to our estimate and is smaller than the one found by other authors using Type Ia Supernovae (though, considering the large error, our result is consistent with the supernova data). The Einstein-de Sitter model is outside the 95% confidence interval of our best fit curve. In order to determine also the Hubble constant, we were compelled to fix one of the free parameters (β, γ, H0, Ωm) and to determine the others with the non-linear least square method. We have proceeded in two different ways. Increasing h0 = H0/100 with a step of 0.01 in the range from 0.65 to 0.95, we obtain a Hubble constant H0 = 74.6 ± 2.4 (km/s)/Mpc in agreement with the values found using CMB, supernovae and cepheids. On the other hand, increasing the parameter m = β/γ with a step of 0.03 in the range from 13.4 to 14.4, we obtain the same result (but with a greater statistical error), and hence a self-consistent model, only assuming β ≥ 8.21. [ABSTRACT FROM AUTHOR]

We test the possible deviation of the cosmic distance duality relation DA(z)(1 + z)2/DL(z) ≡ 1 using the standard candles/rulers in a fully model-independent manner. Type Ia supernovae are used as the standard candles to derive the luminosity distance DL(z), and ultracompact radio sources are used as the standard rulers to obtain the angular diameter distance DA(z). We write the deviation of distance duality relation as DA(z)(1 + z)2/DL(z) = η(z). Specifically, we use two parametrizations of η(z), i.e. η1(z) = 1 + η0z and η2(z) = 1 + η0z/(1 + z). The parameter η0 is obtained using the Markov chain Monte Carlo methods by comparing DL(z) and DA(z) at the same redshift. The best-fitting results are η0 =-0.06 ± 0.05 and -0.18 ± 0.16 for the first and second parametrizations, respectively. Our results depend on neither the cosmological models nor the matter contents or the curvature of the Universe. [ABSTRACT FROM AUTHOR]

Aims: In this work, we address the issue of peculiar velocity measurement in a perturbed Friedmann universe using the deviations from measured luminosity distances of standard candles from background FRW universe. We want to show and quantify the statement that in intermediate redshifts (), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing. We also want to indicate the importance of relativistic calculations for peculiar velocity measurement at all redshifts. Methods: For this task, we discuss the relativistic correction on luminosity distance and redshift measurement and show the contribution of each of the corrections as lensing term, peculiar velocity of the source and Sachs-Wolfe effect. Then, we use the SNe Ia sample of Union 2, to investigate the relativistic effects, we consider. Results: We show that, using the conventional peculiar velocity method, that ignores the lensing effect, will result in an overestimate of the measured peculiar velocities at intermediate redshifts. Here, we quantify this effect. We show that at low redshifts the lensing effect is negligible compare to the effect of peculiar velocity. From the observational point of view, we show that the uncertainties on luminosity of the present SNe Ia data prevent us from precise measuring the peculiar velocities even at low redshifts (). [ABSTRACT FROM AUTHOR]

We discuss production of two μ + μ − pairs in ultraperipheral ultrarelativistic heavy ion collisions at the LHC. We take into account electromagnetic (two-photon) double-scattering production and for a first time direct γγ production of four muons in one scattering. We study the unexplored process γ γ → μ + μ − μ + μ − . We present predictions for total and differential cross sections. Measurable nuclear cross sections are obtained and corresponding differential distributions and counting rates are presented. [ABSTRACT FROM AUTHOR]