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arXiv2007

Practical wavelet design on the sphere

We address the question of designing isotropic analysis functions on the sphere which are perfectly limited in the spectral domain and optimally localized in the spatial domain. This work is motivated by the need of localized analysis tools in domains where the data is lying on the sphere, e.g.{} the science of the Cosmic Microwave Background. Our construction is derived from the localized frames introduced by Narcowich, Petrushev, Ward, 2006. The analysis frames are optimized for given applications and compared numerically using various criteria.

math.NA↗

arXiv2007

Search for large-scale anisotropies with the Auger Observatory

We use more than two years of data from the Pierre Auger Observatory to search for anisotropies on large scales in different energy windows. We account for various systematics in the acceptance, in particular due to the array growth and weather variations. We present the results of analyses and consistency checks looking for patterns in the right ascension modulation of the cosmic ray distribution. No significant anisotropies of this kind are observed.

astro-ph↗

arXiv2007

Measurement of the UHECR energy spectrum from hybrid data of the Pierre Auger Observatory

More than two years of fluorescence detector data collected in coincidence with at least one station of the surface detector array (``hybrid data'') are used to measure the flux and energy spectrum of cosmic rays above about 10$^{18}$ eV. The hybrid measurement extends towards lower energies the spectrum measured with the surface detector data only, and provides a cross-check with an independent data set. The determination of the fluorescence detector aperture and of its live-time, which is the major aspect of this measurement, is illustrated in detail. Our current estimate of the corresponding systematic uncertainties are given.

astro-ph↗

arXiv2007

A search for possible anisotropies of cosmic rays with 0.1<E<10 EeV in the region of the Galactic Centre

We present updated results for anisotropy searches in the direction of the Galactic Center (GC) at energies in the ranges: 0.1<E<1 EeV and 1<E<10 EeV. We use data from the Pierre Auger Observatory up to March, 2007. Present analyzes are therefore based on a substantially larger data set than our previous published results. A limit on the flux coming from a hypothetical point-like neutron source at the GC for 1<E<10 EeV was imposed, and searches for extended excesses were also performed.

astro-ph↗

arXiv2007

Holographic trace anomaly at finite temperature

We find an exact coordinate transformation rule from the $AdS_5$ Schwarzschild black hole in the Poincare and the global patch to the Fefferman-Graham coordinate system. Using these results, we evaluate the corresponding holographic stress tensor and trace anomaly of the boundary theory as a function of the radial coordinate. Following the AdS/CFT correspondence, we reinterpret the radial coordinate dependence of the trace anomaly as the Wilsonian renormalization group(RG) flow of the boundary theory.

hep-th↗

arXiv2007

Constraints on top-down models for the origin of UHECRs from the Pierre Auger Observatory data

Taking into account the Pierre Auger Observatory limits on the photon fraction among the highest energy cosmic rays, we show that the models based on the decay of super-heavy dark matter in the halo of our Galaxy are essentially excluded from being the sources of UHECRs unless their contribution becomes significant only above 100 EeV. Some top-down models based on topological defects are however compatible with the current data and may be best constrained in the future by the high-energy neutrino flux limit.

astro-ph↗

arXiv2007

The optical spectrum of R Coronae Borealis close to 2003 decline

Two sets of high-resolution spectra of R CrB obtained during the 2003 light decline are described. The first set was obtained on the descending branch of the light curve when V ~12.0 and the second one in the recovery phase with V ~7.5. The usual sharp and broad emissions are described and the lines radial velocities measured. C_2 Swan system (0,0) band was found to be in emission for the first set. The other C_2 bands were in absorption. Few CN red system (5,1) band rotational lines and low excitation FeI lines were in absorption. A table with measured radial velocities of various spectral features is presented.

astro-ph↗

arXiv2007

Triadophilia: A Special Corner in the Landscape

It is well known that there are a great many apparently consistent vacua of string theory. We draw attention to the fact that there appear to be very few Calabi--Yau manifolds with the Hodge numbers h^{11} and h^{21} both small. Of these, the case (h^{11}, h^{21})=(3,3) corresponds to a manifold on which a three generation heterotic model has recently been constructed. We point out also that there is a very close relation between this manifold and several familiar manifolds including the `three-generation' manifolds with χ=-6 that were found by Tian and Yau, and by Schimmrigk, during early investigations. It is an intriguing possibility that we may live in a naturally defined corner of the landscape. The location of these three generation models with respect to a corner of the landscape is so striking that we are led to consider the possibility of transitions between heterotic vacua. The possibility of these transitions, that we here refer to as transgressions, is an old idea that goes back to Witten. Here we apply this idea to connect three generation vacua on different Calabi-Yau manifolds.

hep-th↗

arXiv2007

Spinar Paradigm and Gamma Ray Bursts Central Engine

A spinar is a quasi-equilibrium collapsing object whose equilibrium is maintained by the balance of centrifugal and gravitational forces and whose evolution is determined by its magnetic field. The spinar quasi equilibrium model recently discussed as the course for extralong X-ray plateu in GRB (Lipunov & Gorbovskoy, 2007). We propose a simple non stationary three-parameter collapse model with the determining role of rotation and magnetic field in this paper. The input parameters of the theory are the mass, angular momentum, and magnetic field of the collapsar. The model includes approximate description of the following effects: centrifugal force, relativistic effects of the Kerr metrics, pressure of nuclear matter, dissipation of angular momentum due to magnetic field, decrease of the dipole magnetic moment due to compression and general-relativity effects (the black hole has no hare), neutrino cooling, time dilatation, and gravitational redshift. The model describes the temporal behavior of the central engine and demonstrates the qualitative variety of the types of such behavior in nature. We apply our approach to explain the observed features of gamma-ray bursts of all types. In particular, the model allows the phenomena of precursors, x-ray and optical bursts, and the appearance of a plateau on time scales of several thousand seconds to be unified.

astro-ph↗

arXiv2007

An HI study of three long-tailed irregular galaxies in the cluster Abell1367

We present the results on the distribution and kinematics of H$\sc{i}$ gas with higher sensitivity and in one case of higher spectral resolution as well than reported earlier, of three irregular galaxies CGCG 097073, 097079 and 097087 (UGC 06697) in the cluster Abell 1367. These galaxies are known to exhibit long (50$-$75 kpc) tails of radio continuum and optical emission lines (H$α$) pointing away from the cluster centre and arcs of starformation on the opposite sides of the tails. These features as well as the H{\sc i} properties, with two of the galaxies (CGCG 097073 and 097079) exhibiting sharper gradients in H{\sc i} intensity on the side of the tails, are consistent with the H{\sc i} gas being affected by the ram pressure of the intracluster medium. However the H{\sc i} emission in all the three galaxies extends to much smaller distances than the radio-continuum and H$α$ tails, and are possibly still bound to the parent galaxies. Approximately 20$-$30 per cent of the H{\sc i} mass is seen to accumulate on the downstream side due to the effects of ram pressure.

astro-ph↗

arXiv2007

Measurement of Aerosols at the Pierre Auger Observatory

The air fluorescence detectors (FDs) of the Pierre Auger Observatory are vital for the determination of the air shower energy scale. To compensate for variations in atmospheric conditions that affect the energy measurement, the Observatory operates an array of monitoring instruments to record hourly atmospheric conditions across the detector site, an area exceeding 3,000 square km. This paper presents results from four instruments used to characterize the aerosol component of the atmosphere: the Central Laser Facility (CLF), which provides the FDs with calibrated laser shots; the scanning backscatter lidars, which operate at three FD sites; the Aerosol Phase Function monitors (APFs), which measure the aerosol scattering cross section at two FD locations; and the Horizontal Attenuation Monitor (HAM), which measures the wavelength dependence of aerosol attenuation.

astro-ph↗

arXiv2007

A cool R Coronae Borealis star Z UMi

The high resolution spectra of a R CrB type star Z UMi are analysed. The atmospheric parameters of Z UMi are estimated: Teff=5250+/-250K and log g=0.5+/-0.3. This places Z UMi among the coolest R CrB stars. The hydrogen deficiency of Z UMi is confirmed. The abundances of other elements resemble those found for the minority group of R CrB stars. We note very low iron abundance, [Fe/H]=-1.85, and an excess of lithium, [Li/Fe]=+1.9.

astro-ph↗

arXiv2007

Primordial gas heating by dark matter and structure formation

Dark matter (DM) decays and annihilations might heat and partially reionize the Universe at high redshift. Although this effect is not important for the cosmic reionization, the gas heating due to DM particles might affect the structure formation. In particular, the critical halo mass for collapse is increased up to a factor of ~2. Also the fraction of gas which collapses inside the smallest halos is substantially reduced with respect to the cosmological value. These effects imply that DM decays and annihilations might delay the formation of the first structures and reduce the total star mass in the smallest halos.

astro-ph↗

arXiv2007

Coupled phantom field in loop quantum cosmology

A model of phantom scalar field dark energy under exponential potential coupling to barotropic dark matter fluid in loop quantum cosmology is addressed here. We derive a closed-autonomous system for cosmological dynamics in this scenario. The expansion in loop quantum universe has a bounce even in presence of the phantom field. The greater decaying from dark matter to dark phantom energy results in greater energy storing in the phantom field. This results in further turning point of the field. Greater coupling also delays bouncing time. In the case of phantom decaying, oscillation in phantom density makes small oscillation in the increasing matter density.

gr-qc↗

arXiv2008

Comments on the Unified approach to the construction of Classical confidence intervals

The paper comments on properties of the so-called "Unified approach to the construction of classical confidence intervals", in which confidence intervals are computed in a Neyman construction using the likelihood ratio as ordering quantity. In particular, two of the main results of a paper by Feldman and Cousins (F&C) are discussed. It is shown that in the case of central intervals the so-called flip-flopping problem, occuring in the specific scenario where the experimenter decides to quote a standard upper limit or a confidence interval depending on the measurement, can be easily avoided by choosing appropriate confidence levels for the standard upper limits and confidence intervals. In the F&C paper "upper limit" is defined as the upper edge of a confidence interval, whose lower edge coincides with the physical limit. With this definition of upper limit (F&C limit), in an approach which uses the likelihood ratio as ordering quantity, two-sided confidence intervals automatically change over to "upper limits" as the signal becomes weaker (Unified approach). In the present paper it is pointed out that this behaviour is not a special property of this approach, because approaches with other ordering principles, like central intervals, symmetric intervals or highest-probability intervals, exhibit the same behaviour. The Unified approach is presented in the F&C paper as a solution to the flip-flopping problem. This might suggest that the F&C limit is a standard upper limit. In order to exclude any misunderstanding, it is proposed in the present paper to call the F&C limit "upper edge of the confidence interval", even if its lower edge coincides with the physical limit.

physics.data-an↗

arXiv2007

Photon spectra from final stages of a primordial black hole evaporation in different theoretical models

Possibilities of an experimental search for gamma-ray bursts from primordial black hole (PBH) evaporations in space are reconsidered. It is argued that the corresponding constraints which can be obtained in experiments with cosmic ray detectors strongly depend on theoretical approach used for a description of the PBH evaporation process. Predictions of several theoretical models for gamma-ray spectra from final stages of PBH life (integrated over time) are given.

astro-ph↗

arXiv2007

Selection and reconstruction of very inclined air showers with the Surface Detector of the Pierre Auger Observatory

The water-Cherenkov tanks of the Pierre Auger Observatory can detect particles at all zenith angles and are therefore well-suited for the study of inclined and horizontal air showers (60 - 90 degrees). Such showers are characterised by a dominance of the muonic component at ground, and by a very elongated and asymmetrical footprint which can even exhibit a lobular structure due to the bending action of the geomagnetic field. Dedicated algorithms for the selection and reconstruction of such events, as well as the corresponding acceptance calculation, have been set up on basis of muon maps obtained from shower simulations.

astro-ph↗

arXiv2007

Eight powers of ten: similarities in black hole accretion on all mass scales

In this paper we discuss the recent advances in the quantitative comparison of accretion, and the accretion:jet coupling, in accreting black holes in both X-ray binaries (where M ~ 10Msun) and Active Galactic Nuclei (10^5Msun < M < 10^9Msun). These similarities include the radiative efficiency and jet power as a function of accretion rate, which are themselves probably the origin of the `fundamental plane of black hole activity'. A second `fundamental plane' which connects mass, accretion rate and timing properties provides us with a further physical diagnostic. Patterns of radio loudness (i.e. jet production) as a function of luminosity and accretion state are shown to be similar for X-ray binaries and AGN. Finally we discuss how neutron stars are a useful control sample, and what the future may hold for this field.

astro-ph↗