http://www.hindawi.comThe latest articles from Hindawi Publishing Corporation© 2012, Hindawi Publishing Corporation. All rights reserved.http://www.hindawi.com/journals/aa/2011/327641/Our groups in Brazil, France and Italy have been active, among others in the world, in performing experiments on physical-chemical effects induced by fast ions colliding with solids (frozen gases, carbonaceous and organic materials, silicates, etc.) of astrophysical interest. The used ions span a very large range of energies, from a few keV to hundreds MeV. Here we present a summary of the results obtained so far on the formation of oxidants (hydrogen peroxide and ozone) after ion irradiation of frozen water, carbon dioxide and their mixtures. Irradiation of pure water ice produces hydrogen peroxide whatever is the used ion and at different temperatures. Irradiation of carbon dioxide and water frozen mixtures result in the production of molecules among which hydrogen peroxide and ozone. The experimental results are discussed in the light of the relevance they have to support the presence of an energy source for biosphere on Europa and other icy moons in the outer Solar System.Philippe Boduch, Enio Frota da Silveira, Alicja Domaracka, Oscar Gomis, Xue Yang Lv, Maria Elisabetta Palumbo, Sergio Pilling, Hermann Rothard, Eduardo Seperuelo Duarte, and Giovanni StrazzullaCopyright © 2011 Philippe Boduch et al. All rights reserved.http://www.hindawi.com/journals/aa/2011/953936/Viking missions reported adverse conditions for life in Mars surface. High hydrogen signal obtained by Mars orbiters has increased the interest in subsurface prospection as putative protected Mars environment with life potential. Permafrost has attracted considerable interest from an astrobiological point of view due to the recently reported results from the Mars exploration rovers. Considerable studies have been developed on extreme ecosystems and permafrost in particular, to evaluate the possibility of life on Mars and to test specific automated life detection instruments for space missions. The biodiversity of permafrost located on the Bering Land Bridge National Preserve has been studied as an example of subsurface protected niche of astrobiological interest. Different conventional (enrichment and isolation) and molecular ecology techniques (cloning, fluorescence “in situ” probe hybridization, FISH) have been used for isolation and bacterial identification.F. Gómez, O. Prieto-Ballesteros, D. Fernández-Remolar, J. A. Rodríguez-Manfredi, M. Fernández-Sampedro, M. Postigo Cacho, J. Torres Redondo, N. Rodríguez, J. Gómez-Elvira, and R. AmilsCopyright © 2011 F. Gómez et al. All rights reserved.http://www.hindawi.com/journals/aa/2011/189379/The idea that quantum gravity can be realized at the TeV scale is extremely attractive to theorists and experimentalists alike. This proposal leads to extra spacial dimensions large compared to the Planck scale. Here, we give a very systematic view of the foundations of the theories with large extra dimensions and their physical consequences.V. H. Satheeshkumar and P. K. SureshCopyright © 2011 V. H. Satheeshkumar and P. K. Suresh. All rights reserved.http://www.hindawi.com/journals/aa/2011/143698/This paper presents optical and Hα imaging for a large sample of LSB galaxies selected from the PSS-II catalogs (Schombert et al., 1992). As noted in previous work, LSB galaxies span a range of luminosities (-10>MV>-20) and sizes (0.3 kpc<RV25<10 kpc), although they are consistent in their irregular morphology. Their Hα luminosities (L(Hα)) range from 1036 to 1041 ergs s-1 (corresponding to a range in star formation, using canonical prescriptions, from 10-5 to 1 M⨀ yr-1). Although their optical colors are at the extreme blue edge for galaxies, they are similar to the colors of dwarf galaxies (Van Zee, 2001) and gas-rich irregulars (Hunter and Elmegreen, 2006). However, their star formation rates per unit stellar mass are a factor of ten less than other galaxies of the same baryonic mass, indicating that they are not simply quiescent versions of more active star-forming galaxies. This paper presents the data, reduction techniques, and new philosophy of data storage and presentation. Later papers in this series will explore the stellar population and star formation history of LSB galaxies using this dataset.James Schombert, Tamela Maciel, and Stacy McGaughCopyright © 2011 James Schombert et al. All rights reserved.http://www.hindawi.com/journals/aa/2011/174873/In the recent years, non-Gaussianity and statistical isotropy of the Cosmic Microwave Background (CMB) was investigated with various statistical measures, first and foremost by means of the measurements of the WMAP satellite. In this paper, we focus on the analyses that were accomplished with a measure of local type, the so-called Scaling Index Method (SIM). The SIM is able to detect structural characteristics of a given data set and has proven to be highly valuable in CMB analysis. It was used for comparing the data set with simulations as well as surrogates, which are full-sky maps generated by randomisation of previously selected features of the original map. During these investigations, strong evidence for non-Gaussianities as well as asymmetries and local features could be detected. In combination with the surrogates approach, the SIM detected the highest significances for non-Gaussianity to date.G. Rossmanith, H. Modest, C. Räth, A. J. Banday, K. M. Górski, and G. MorfillCopyright © 2011 G. Rossmanith et al. All rights reserved.http://www.hindawi.com/journals/aa/2011/196852/We argue that the hypothesis of the gravitational repulsion between matter and antimatter can be tested at the Ice Cube, a neutrino telescope, recently constructed at the South Pole. If there is such a gravitational repulsion, the gravitational field, deep inside the horizon of a black hole, might create neutrino-antineutrino pairs from the quantum vacuum. While neutrinos must stay confined inside the horizon, the antineutrinos should be violently ejected. Hence, a black hole (made from matter) should behave as a point-like source of antineutrinos. Our simplified calculations suggest that the antineutrinos emitted by supermassive black holes in the centre of the Milky Way and Andromeda Galaxy could be detected by the new generation of neutrino telescopes.Dragan Slavkov HajdukovicCopyright © 2011 Dragan Slavkov Hajdukovic. All rights reserved.http://www.hindawi.com/journals/aa/2011/412620/Relativistic radiative transfer in a relativistic spherical flow is examined in the fully special relativistic treatment. Under the assumption of a constant flow speed and using a variable (prescribed) Eddington factor, we analytically solve the relativistic moment equations in the comoving frame for several restricted cases, and obtain relativistic Milne-Eddington type solutions. In contrast to the plane-parallel case where the solutions exhibit the exponential behavior on the optical depth, the solutions have power-law forms. In the case of the radiative equilibrium, for example, the radiative flux has a power-law term multiplied by the exponential term. In the case of the local thermodynamic equilibrium with a uniform source function in the comoving frame, the radiative flux has a power-law form on the optical depth. This is because there is an expansion effect (curvature effect) in the spherical wind and the background density decreases as the radius increases.Jun FukueCopyright © 2011 Jun Fukue. All rights reserved.http://www.hindawi.com/journals/aa/2010/184284/This paper is a review on the observational Hubble parameter data that have gained increasing attention in recent years for their illuminating power on the dark side of the universe: the dark matter, dark energy, and the dark age. Currently, there are two major methods of independent observational H(z) measurement, which we summarize as the “differential age method” and the “radial BAO size method.” Starting with fundamental cosmological notions such as the spacetime coordinates in an expanding universe, we present the basic principles behind the two methods. We further review the two methods in greater detail, including the source of errors. We show how the observational H(z) data present itself as a useful tool in the study of cosmological models and parameter constraint, and we also discuss several issues associated with their applications. Finally, we point the reader to a future prospect of upcoming observation programs that will lead to some major improvements in the quality of observational H(z) data.Tong-Jie Zhang, Cong Ma, and Tian LanCopyright © 2010 Tong-Jie Zhang et al. All rights reserved.http://www.hindawi.com/journals/aa/2010/586590/Magnetic fields are everywhere in nature, and they play an important role in every astronomical environment which involves the formation of plasma and currents. It is natural therefore to suppose that magnetic fields could be present in the turbulent high-temperature environment of the big bang. Such a primordial magnetic field (PMF) would be expected to manifest itself in the cosmic microwave background (CMB) temperature and polarization anisotropies, and also in the formation of large-scale structure. In this paper, we summarize the theoretical framework which we have developed to calculate the PMF power spectrum to high precision. Using this formulation, we summarize calculations of the effects of a PMF which take accurate quantitative account of the time evolution of the cutoff scale. We review the constructed numerical program, which is without approximation, and an improvement over the approach used in a number of previous works for studying the effect of the PMF on the cosmological perturbations. We demonstrate how the PMF is an important cosmological physical process on small scales. We also summarize the current constraints on the PMF amplitude Bλ and the power spectral index nB which have been deduced from the available CMB observational data by using our computational framework.Dai G. Yamazaki, Kiyotomo Ichiki, Toshitaka Kajino, and Grant J. MathewsCopyright © 2010 Dai G. Yamazaki et al. All rights reserved.http://www.hindawi.com/journals/aa/2010/904379/We analyze and review cosmological models in which the dynamics of a single scalar field accounts for a unified description of the Dark Matter and Dark Energy sectors, dubbed Unified Dark Matter (UDM) models. In this framework, we consider the general Lagrangian of k-essence, which allows to find solutions around which the scalar field describes the desired mixture of Dark Matter and Dark Energy. We also discuss static and spherically symmetric solutions of Einstein's equations for a scalar field with noncanonical kinetic term, in connection with galactic halo rotation curves.Daniele Bertacca, Nicola Bartolo, and Sabino MatarreseCopyright © 2010 Daniele Bertacca et al. All rights reserved.http://www.hindawi.com/journals/aa/2009/217420/The so-called f(R)-gravity has recently attracted a lot of interest since it could be, in principle, able to explain the accelerated expansion of the Universe without adding unknown forms of dark energy/dark matter but, more simply, extending the General Relativity by generic functions of the Ricci scalar. However, apart several phenomenological models, there is no final f(R)-theory capable of fitting all the observations and addressing all the issues related to the presence of dark energy and dark matter. An alternative approach could be to “reconstruct” the form of f(R) starting from data without imposing particular classes of model. Besides, adopting the same philosophy, we take into account the possibility that galaxy cluster masses, estimated at X-ray wavelengths, could be explained, without dark matter, reconstructing the weak-field limit of analytic f(R) models. The corrected gravitational potential, obtained in this approximation, is used to estimate the total mass of a sample of 12 well-shaped clusters of galaxies.Salvatore Capozziello and Vincenzo SalzanoCopyright © 2009 Salvatore Capozziello and Vincenzo Salzano. All rights reserved.http://www.hindawi.com/journals/aa/2010/735487/We investigate the effect of possible a priori “imprinting” effects of general relativity itself on satellite/spacecraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the sun's gravitational field. It turns out that the “imprint” of general relativity on the Astronomical Unit and the solar gravitational constant GM⊙, not solved for in the so far performed spacecraft-based time-delay tests, induces an a priori bias of the order of 10-6 in typical solar system ranging experiments aimed to measure the space curvature PPN parameter γ. It is too small by one order of magnitude to be of concern for the performed Cassini experiment, but it would affect future planned or proposed tests aiming to reach a 10-7–10-9 accuracy in determining γ.Lorenzo IorioCopyright © 2010 Lorenzo Iorio. All rights reserved.http://www.hindawi.com/journals/aa/2009/632064/The cosmological constant problem is principally concerned with trying to understand how the zero-point energy of quantum fields contributes to gravity. Here we take the approach that by addressing a fundamental unresolved issue in quantum theory, we can gain a better understanding of the problem. Our starting point is the observation that the notion of classical time is external to quantum mechanics. Hence there must exist an equivalent reformulation of quantum mechanics which does not refer to an external classical time. Such a reformulation is a limiting case of a more general quantum theory which becomes nonlinear on the Planck mass/energy scale. The nonlinearity gives rise to a quantum-classical duality which maps a “strongly quantum, weakly gravitational” dynamics to a “weakly quantum, strongly gravitational” dynamics. This duality predicts the existence of a tiny nonzero cosmological constant of the order of the square of the Hubble constant, which could be a possible source for the observed cosmic acceleration. Such a nonlinearity could also be responsible for the collapse of the wave function during a quantum measurement.T. P. SinghCopyright © 2009 T. P. Singh. All rights reserved.http://www.hindawi.com/journals/aa/2009/752439/The only viable alternative to dark matter is one in which Newtonian dynamics or gravity breaks down in the limit of low accelerations, as in modified Newtonian dynamics (MONDs). This hypothesis, suggested by Milgrom, has been successful in explaining systematic properties of spiral and elliptical galaxies and predicting in detail the observed rotation curves of spiral galaxies with only one additional parameter—a critical acceleration which is on the order of the cosmologically interesting value of cHo. MOND may be viewed as an algorithm for calculating the distribution of force in an astronomical object from the observed distribution of baryonic matter. The fact that it works very well on the scale of galaxies is problematic for cold dark matter (CDM). Here I present evidence in favor of this assertion and claim that this is, in effect, a falsification of CDM on the scale of galaxies.R. H. SandersCopyright © 2009 R. H. Sanders. All rights reserved.http://www.hindawi.com/journals/aa/2009/931920/We discuss recent laboratory experiments with rotating superconductors and show that three so far unexplained experimentally observed effects (anomalous acceleration signals, anomalous gyroscope signals, Cooper pair mass excess) can be physically explained in terms of a possible interaction of dark energy with Cooper pairs. Our approach is based on a Ginzburg-Landau-like model of electromagnetic dark energy, where gravitationally active photons obtain mass in the superconductor. We show that this model can account simultaneously for the anomalous acceleration and anomalous gravitomagnetic fields around rotating superconductors measured by Tajmar et al. and for the anomalous Cooper pair mass in superconductive Niobium, measured by Cabrera and Tate. It is argued that these three different physical effects are ultimately different experimental manifestations of the simultaneous spontaneous breaking of gauge invariance and of the principle of general covariance in superconductive materials.Clovis Jacinto de Matos and Christian BeckCopyright © 2009 Clovis Jacinto de Matos and Christian Beck. All rights reserved.http://www.hindawi.com/journals/aa/2009/306821/We present new analysis of the birth rate of AXPs and SGRS and their associated SNRs. Using Kolmogorov-Smirnov statistics together with parametric fits based on a robust estimator, we find a birth rate of ∼1/(1000 years) for AXPs/SGRs and their associated SNRs. These high rates suggest that all massive stars (greater than ∼(23–32)M⊙) give rise to remnants with magnetar-like fields. Observations indicate a limited fraction of high magnetic fields in these progenitors; thus our study is suggestive of magnetic field amplification. Dynamo mechanisms during the birth of the neutron stars require spin rates much faster than either observations or theory indicate. We propose that massive stars produce neutron stars with normal (∼1012 G) magnetic fields, which are then amplified to 1014-1015 G after a delay of hundreds of years. The amplification is speculated to be a consequence of color ferromagnetism and to occur with a delay after the neutron star core reaches quark deconfinement density (i.e., the quark-nova scenario). The delayed amplification allows one to interpret simultaneously the high birth rate and high magnetic fields of AXPs/SGRs and their link to massive stars.Denis Leahy and Rachid OuyedCopyright © 2009 Denis Leahy and Rachid Ouyed. All rights reserved.http://www.hindawi.com/journals/aa/2009/463521/If a quark-nova occurs inside a collapsar, the interaction between the quark-nova ejecta (relativistic iron-rich chunks) and the collapsar envelope leads to features indicative of those observed in Gamma Ray Bursts. The quark-nova ejecta collides with the stellar envelope creating an outward moving cap (Γ∼ 1–10) above the polar funnel. Prompt gamma-ray burst emission from internal shocks in relativistic jets (following accretion onto the quark star) becomes visible after the cap becomes optically thin. Model features include (i) precursor activity (optical, X-ray, γ-ray), (ii) prompt γ-ray emission, and (iii) afterglow emission. We discuss SN-less long duration GRBs, short hard GRBs (including association and nonassociation with star forming regions), dark GRBs, the energetic X-ray flares detected in Swift GRBs, and the near-simultaneous optical and γ-ray prompt emission observed in GRBs in the context of our model.Rachid Ouyed, Denis Leahy, Jan Staff, and Brian NiebergalCopyright © 2009 Rachid Ouyed et al. All rights reserved.http://www.hindawi.com/journals/aa/2009/309024/we continue our study of the CMB temperature polarization (TE) cross-correlation as a source of information about primordial gravitational waves (PGWs). In a previous paper, we considered two methods for detecting PGWs using the TE cross-correlation. The first method is the zero multipole method, where we find the multipole, ℓ0, where the TE cross-correlation power spectrum, CℓTE, first changes sign. The second method Wiener filters the CMB TE data to remove the density perturbation contribution to the TE power spectrum. We then use statistical tests to determine if there is a detection of negative residual TE correlation and hence a detection of primordial gravitational waves, the only source of negative TE correlation at these superhorizon scales. In this paper, we will apply these tests to the WMAP 5-year data. We find that the TE power spectrum consistent with r < 2.0 at 95% confidence with no additional assumptions about the PGWs. If we assume that the PGWs are generated by inflation, then we get r < 1.0 at 95% confidence.N. J. Miller, B. G. Keating, and A. G. PolnarevCopyright © 2009 N. J. Miller et al. All rights reserved.http://www.hindawi.com/journals/aa/2008/870804/Conventional equilibrium statistical mechanics of open gravitational systems is known to be problematical. We first recall that spherical stars/galaxies acquire unbounded radii, become infinitely massive, and evaporate away continuously if one uses the standard Maxwellian distribution fB (which maximizes the usual Boltzmann-Shannon entropy and hence has a tail extending to infinity). Next, we show that these troubles disappear automatically if we employ the exact most probable distribution f (which maximizes the combinatorial entropy and hence possesses a sharp cutoff tail). Finally, if astronomical observation is carried out on a large galaxy, then the Poisson equation together with thermal de Broglie wavelength provides useful information about the cutoff radius rK, cutoff energy εK, and the huge quantum number K up to which the cluster exists. Thereby, a refinement over the empirical lowered isothermal King models, is achieved. Numerically, we find that the most probable distribution (MPD) prediction fits well the number density profile near the outer edge of globular clusters.Ritesh Kumar Dubey, V. J. Menon, M. K. Pandey, and D. N. TripathiCopyright © 2008 Ritesh Kumar Dubey et al. All rights reserved.http://www.hindawi.com/journals/aa/2008/425412/The effect of perturbations in Coriolis and cetrifugal forces on the nonlinear stability of the equilibrium point of the Robe's (1977) restricted circular three-body problem has been studied when the density parameter K is zero. By applying Kolmogorov-Arnold-Moser (KAM) theory, it has been found that the equilibrium point is stable for all mass ratios μ in the range of linear stability 8/9+(2/3)((43/25)ϵ1−(10/3)ϵ)<μ<1, where ϵ and ϵ1 are, respectively, the perturbations in Coriolis and centrifugal forces, except for five mass ratios μ1=0.93711086−1.12983217ϵ+1.50202694ϵ1, μ2 = 0.9672922−0.5542091ϵ+ 1.2443968ϵ1, μ3=0.9459503−0.70458206ϵ+ 1.28436549ϵ1, μ4=0.9660792−0.30152273ϵ + 1.11684064ϵ1, μ5=0.893981−2.37971679ϵ + 1.22385421ϵ1, where the theory is not applicable.P. P. Hallan and Khundrakpam Binod MangangCopyright © 2008 P. P. Hallan and Khundrakpam Binod Mangang. All rights reserved.http://www.hindawi.com/journals/aa/2008/268647/We use the corrections to the Newton-Einstein secular precessions of the longitudes of perihelia ϖ˙ of some planets (Mercury, Earth, Mars, Jupiter, Saturn) of the Solar System, phenomenologically estimated as solve-for parameters by the Russian astronomer E. V. Pitjeva in a global fit of almost one century of data with the EPM2004 ephemerides, in order to put on the test the expression for the perihelion precession induced by a uniform cosmological constant Λ in the framework of the Schwarzschild-de Sitter (or Kottler) space-time. We compare such an extra rate to the estimated corrections to the planetary perihelion precessions by taking their ratio for different pairs of planets instead of using one perihelion at a time for each planet separately, as done so far in literature. The answer is negative, even by further rescaling by a factor 10 (and even 100 for Saturn) the errors in the estimated extra precessions of the perihelia released by Pitjeva. Our conclusions hold also for any other metric perturbation having the same dependence on the spatial coordinates, as those induced by other general relativistic cosmological scenarios and by many modified models of gravity. Currently ongoing and planned interplanetary spacecraft-based missions should improve our knowledge of the planets' orbits allowing for more stringent constraints.Lorenzo IorioCopyright © 2008 Lorenzo Iorio. All rights reserved.