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The observation that Type Ia supernovae are fainter than expected given their red shifts has led to the conclusion that the expansion of the universe is accelerating. The widely accepted hypothesis is that this acceleration is caused by a cosmological constant or, more generally, some dark energy field that pervades the universe. This hypothesis presents a challenge to physics so severe that one is motivated to explore alternative explanations. In this paper, we explore whether the data from Type Ia supernovae can be explained with an idea that is almost as old as that of the cosmological constant, namely, that the strength of gravity varies on a cosmic timescale. This topic is an ideal one for investigation by an undergraduate physics major because the entire chain of reasoning from models to data analysis is well within the mathematical and conceptual ...

International Nuclear Information System (INIS)

We compare the existing observational data on type Ia supernovae with the evolutions of the Universe predicted by a one-parameter family of tachyon models which we have introduced recently [Phys. Rev. D 69, 123512 (2004)]. Among the set of the trajectories of the model which are compatible with the data there is a consistent subset for which the Universe ends up in a new type of soft cosmological singularity dubbed big brake. This opens up yet another scenario for the future history of the Universe besides the one predicted by the standard #LAMBDA#CDM model.

CERN Document Server

We propose a new method to measure the metallicity of Type Ia supernova progenitors using Mn and Cr lines in the X-ray spectra of young supernova remnants. We show that the Mn to Cr mass ratio in Type Ia supernova ejecta is tightly correlated with the initial metallicity of the progenitor, as determined by the neutron excess of the white dwarf material before thermonuclear runaway. We use this correlation, together with the flux of the Cr and Mn Kalpha X-ray lines in the Tycho supernova remnant recently detected by Suzaku (Tamagawa et al. 2008) to derive a metallicity of log(Z) = -1.32 (+0.67,-0.33) for the progenitor of this supernova, which corresponds to log(Z/Zsun)= 0.60 (+0.31,-0.60) according to the latest determination of the solar metallicity by Asplund et al. (2005). The uncertainty in the measurement is large, but metallicities ...

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The current status of cosmological observations is presented; and the light curves and radiation spectra from supernova SN1987A are used in comparison between expected and observed universal nucleosynthesis and star evolution data./aip/.

CERN Document Server

We develop and demonstrate the methodology of testing multi-dimensional supernova models against observations by studying the properties of one example of the detonation from failed deflagration (DFD) explosion model of thermonuclear supernovae. Using time-dependent multi-dimensional radiative transfer calculations, we generate the synthetic broadband optical light curves, near-infrared light curves, color evolution curves, full spectral time-series, and spectropolarization of the model, as seen from various viewing angles. All model observables are critically evaluated against examples of well-observed, standard Type Ia supernovae (SNe Ia). We explore the consequences of the intrinsic model asphericity by studying the dependence of the model emission on viewing angle, and by quantifying the resulting dispersion in (and internal correlations between) various model observables. These ...

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The problem on change of deuterium abundance in the process of galactic evolution (star evolution, supernova explosions, nucleosynthesis in supermassive objects) is considered. It is shown that the observable deuterium quantity in the interstellar medium must correspond to its cosmological abundance. This conclusion is independent of the rate of accretion of intergalactic gas by Galaxy. The effect of hypothetical pregalactic active objects on cosmological deuterium is small. It is poind out that observations of interstellar deuterium in absorbtion at lambda=91.6 cm are significant.

CERN Document Server

The delayed detonation model describes the observational properties of the majority of type Ia supernovae very well. Using numerical data from a three-dimensional deflagration model for type Ia supernovae, the intermittency of the turbulent velocity field and its implications on the probability of a deflagration-to-detonation (DDT) transition are investigated. From structure functions of the turbulent velocity fluctuations, we determine intermittency parameters based on the log-normal and the log-Poisson models. On the other hand, the analysis of the turbulent velocity fluctuations in the vicinity of the flame front by Roepke suggests a much higher probability of large velocity fluctuations on the grid scale in comparison to the log-normal intermittency model. Following Pan et al., we computed probability density functions for a DDT for the different distributions. Assuming that a DDT can occur in the ...

CERN Document Server

If quantum fields exist in extra compact dimensions, they will give rise to a quantum vacuum or Casimir energy. That vacuum energy will manifest itself as a cosmological constant. The fact that supernova and cosmic microwave background data indicate that the cosmological constant is of the same order as the critical mass density to close the universe supplies a lower bound on the size of the extra dimensions. Recent laboratory constraints on deviations from Newton's law place an upper limit. The allowed region is so small as to suggest that either extra compact dimensions do not exist, or their number is about to be tightly constrained by experimental data.

CERN Document Server

Constraints on the original Cardassian model and the modified polytropic Cardassian model are examined from the latest derived 397 Type Ia supernova (SNe Ia) data, the size of baryonic acoustic oscillation peak from the Sloan Digital Sky Survey (SDSS), the position of first acoustic peak of the Cosmic Microwave Background radiation (CMB) from the five years Wilkinson Microwave Anisotropy Probe (WMAP), the x-ray gas mass fractions in clusters of galaxies, and the observational H(z) data. In the original Cardassian model with these combined data set, we find $\\Omega_{m0}=0.271^{+0.014}_{-0.014}, n=0.035^{+0.049}_{-0.049}$ at $1 \\sigma$ confidence level. And in the modified polytropic Cardassian model, we find that $\\Omega_{m0}=0.271^{+0.014}_{-0.015}$, $n=-0.091^{+0.331}_{-1.908}$ and $\\beta=0.824^{+0.750}_{-0.622}$ within $1\\sigma$ confidence level. According to these observations, the acceleration of the universe ...

CERN Document Server

We study the sensitivity to neutrino masses of a Galactic supernova neutrino signal as could be measured with the detectors presently in operation and with future large volume water \\v{C}erencov and scintillator detectors. The analysis uses the full statistics of neutrino events. The method proposed uses the principles of Bayesian inference reasoning and has shown a remarkably independence of astrophysical assumptions. We show that, after accounting for the uncertainties in the detailed astrophysical description of the neutrino signal and taking into account the effects of neutrino oscillations in the supernova mantle, detectors presently in operation can have enough sensitivity to reveal a neutrino mass (or to set upper limits) at the level of 1 eV. This is sensibly better than present results from tritium $\\beta$-decay experiments, competitive with the most conservative limits from neutrinoless double $\\beta$-decay and less precise but ...

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Neutrino processes role in star evolution and onset of supernovae explosion

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No abstract prepared.

CERN Document Server

We calculated the matter effect, including both the Earth and supernova, on the detection of neutrinos from type II supernovae at the proposed Daya Bay reactor neutrino experiment. It is found that apart from the dependence on the flip probability P_H inside the supernova and the mass hierarchy of neutrinos, the amount of the Earth matter effect depends on the direction of the incoming supernova neutrinos, and reaches the biggest value when the incident angle of neutrinos is around 93^\\circ. In the reaction channel \\bar{\

DEFF Research Database (Denmark)

Udgivelsesdato: 1988-Jul

CERN Document Server

Gamma-Ray Bursts (GRBs) are thought to originate at cosmological distances from the most powerful explosions in the Universe. If GRBs are not beamed then the distribution of their number as a function of gamma-ray flux implies that they occur once per (0.3-40) million years per bright galaxy and that they deposit >10^{53} ergs into their surrounding interstellar medium. The blast wave generated by a GRB explosion would be washed out by interstellar turbulence only after tens of millions of years when it finally slows down to a velocity of 10 km/s. This rather long lifetime implies that there could be up to several tens of active GRB remnants in each galaxy at any given time. For many years, radio observations have revealed the enigmatic presence of expanding neutral-hydrogen (HI) supershells of kpc radius in the Milky Way and in other nearby galaxies. The properties of some supershells cannot be easily explained in terms of conventional sources such as stellar ...

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the picture will download the highest resolution version available. Supernovae in the Whirlpool Image Credit & Copyright: R Jay Gabany Explanation: Where do spiral galaxies keep...

International Nuclear Information System (INIS)

1983. p. 225. USSR Boydachenko, IV Evstyukhina, IA Devyatko, YN Moskovskij

CERN Document Server

In this paper, we first discuss the detection of supernova neutrino on Earth. Then we propose a possible method to acquire information about $\\theta_{13}$ smaller than $1.5^\\circ$ by detecting the ratio of the event numbers of different flavor supernova neutrinos. Such an sensitivity cannot yet be achieved by the Daya Bay reactor neutrino experiment.

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Design of Damage-Tolerant Composite Sandwich Panels with Tear Straps. Sukra Helitek Inc. 3146 Greenwood Road. Ames, IA 50014-4504 ...

CERN Document Server

We present constraints on theoretical models of Type Ia SNe using spatially resolved ASCA X-ray spectroscopy of four galaxy clusters: Abell 496, Abell 2199, Abell 3571 & Perseus. All four clusters have central Fe abundance enhancements and an ensemble of abundance ratios are used to show that most of the Fe in the central regions of the clusters comes from SN Ia. At the center of each cluster, simultaneous analysis of spectra from all ASCA instruments shows that the Ni to Fe abundance ratio (normalized by the solar ratio) is ~ 4. We use the Ni/Fe ratio as a discriminator between SN Ia explosion models: the Ni/Fe ratio of ejecta from the "Convective Deflagration" model W7 is consistent with the observations, while those of "delayed detonation" models are not consistent at the 90% confidence level.

International Nuclear Information System (INIS)

(Dec 1971). United States Ryan, MP Jr. v. 68(2) p. 541-555. cosmological

International Nuclear Information System (INIS)

Core-collapse supernovae are among Nature's most energetic events. They mark the end of massive star evolution and pollute the interstellar medium with the life-enabling ashes of thermonuclear burning. Despite their importance for the evolution of galaxies and life in the universe, the details of the core-collapse supernova explosion mechanism remain in the dark and pose a daunting computational challenge. We outline the multi-dimensional, multi-scale, and multi-physics nature of the core-collapse supernova problem and discuss computational strategies and requirements for its solution. Specifically, we highlight the axisymmetric (2D) radiation-MHD code VULCAN/2D and present results obtained from the first full-2D angle-dependent neutrino radiation-hydrodynamics simulations of the post-core-bounce supernova evolution. We then go on to discuss the new code Zelmani which is based on the open-source HPC ...

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Form as the end result of massive star evolution; Type II supernova: collapse of iron core in highly evolved massive star; outer regions blasted away in ...

Science.gov (United States)

Apr 23, 2009 ... Wolf-Rayet stars have over 20 times the mass of the Sun and are thought to be in a brief, pre-supernova phase of massive star evolution. ...

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We examine the late-time behavior of initially expanding homogeneous cosmological models satisfying Einstein's equation with a positive cosmological constant ..lambda... It is shown that such models of all Bianchi types except IX exponentially evolve toward the de Sitter solution, with time scale (3/..lambda..)/sup 1/2/. The behavior of Bianchi type-IX universes is similar, provided that ..lambda.. is sufficiently large compared with spatial-curvature terms. Thus, a positive cosmological constant provides an effective means of isotropizing homogeneous universes.

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A technique has been developed which enables the direct sputter generation of atomic negative ion beams of all members of the Group IA elements (Li, Na, K, Rb and Cs). The method is based on the use of sputter samples formed by pressing mixtures of the carbonates of the Group IA elements and 10% (atomic) Cu, Ag or other metal powders. The following intensities are typical of those observed from carbonate samples subjected to approx. = 3 keV cesium ion bombardment: Li/sup -/: greater than or equal to 0.5 ..mu..A; Na/sup -/: greater than or equal to 0.5 ..mu..A; K/sup -/: greater than or equal to 0.5 ..mu..A; Rb/sup -/: greater than or equal to 0.5 ..mu..A; Cs/sup -/: greater than or equal to 0.2 ..mu..A.

CERN Document Server

One hope to solve the cosmological constant problem is to identify a symmetry principle, based on which the cosmological constant can be reduced either to zero, or to a tiny value. Here, we note that requiring that the vacuum state is Lorentz invariant significantly reduces the theoretical value of the vacuum energy density. Hence, this also reduces the discrepancy between the observed value of the cosmological constant and its theoretical expectation, down from 123 orders of magnitude to 56 orders of magnitude. We find that, at one loop level, massless particles do not yield any contribution to the cosmological constant. Another important consequence of Lorentz symmetry is stabilization of the gravitational hierarchy: the cosmological constant (divided by Newton's constant) does not run as the quartic power of the renormalization group scale, but instead only logarithmically.

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... t.., tt:,tifv! th - cui,nt !shor tfal 1 in breaching capAbiii tN wi h i- 1!,-ia . ~ ... Before the 1967 war, the Israeli Training ... trained Arab opponents. ...

UK PubMed Central (United Kingdom)

Type II collagen-induced arthritis (CIA) in mice is an autoimmune experimental model for rheumatoid arthritis. Susceptibility to CIA is associated with certain major histocompatibility complex class...Full Text Available

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... B I 3 IT TAKES MORE THAN WOODLAND CAMOUFLAGE PAINT! 1X I ... ITEMS/SYSTEMS sm . 4J eo IA''5 FOR CAMOUFLAGE Page 18. SECTION ...

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We present results from ab-initio electronic-structure calculations of mechanical properties of the rhombohedral phase of vanadium reported in recent experiments (R Ia), and other predicted high-pressure phases (R Ib and bcc), focusing on properties relevant to dynamic experiments. We find that of the three transitions the largest volume collapse (1.3%) is for the R Ia to R Ib transition. Calculations of the single crystal and polycrystal elastic constants reveal a remarkably small discontinuity across the phase transitions even at zero temperature where the transitions are first order.

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This paper reports on Monte Carlo path integral simulations of a Bianchi Type IX cosmology which yield a wave function which reflects the known chaotic dynamics of the classical system and predicts a significant probability for a correlation between large universe volume and large anisotropy.

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We show the existence of a rather general class of closed cosmological models of Bianchi type IX that do not exhibit recollapse but expand for all times. This is despite the fact that these models satisfy the strong energy condition by a wide margin.

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We discuss the asymptotic dynamical evolution of spatially homogeneous brane-world cosmological models close to the initial singularity. We find that generically the cosmological singularity is isotropic in Bianchi type IX brane-world models and consequently these models do not exhibit Mixmaster or chaotic-like behaviour close to the initial singularity. We argue that this is typical of more general cosmological models in the brane-world scenario. In particular, we show that an isotropic singularity is a past-attractor in all orthogonal Bianchi models and is a local past-attractor in a class of inhomogeneous brane-world models. (letter to the editor)

International Nuclear Information System (INIS)

We discuss various superstring effective actions and, in particular, their common sector which leads to the so-called pre-big-bang cosmology (cosmology in a weak coupling limit of heterotic superstring theory. Using the conformal relationship between these two theories we present Kasner asymptotic solutions of Bianchi type IX geometries within these theories and make predictions about possible emergence of chaos. Finally, we present a possible method of generating Horava-Witten cosmological solutions out of the well-known general relativistic or pre-big-bang solutions.

International Nuclear Information System (INIS)

A Bianchi type-IX cosmological model has been found as a solution of Einstien's vacuum field equations with a cosmological constant. The solution represents a rotating generalziation fo the de Sitter universe. This universe shows a transition to exponential expansion and the vorticity begins to decay exponentially at the grand-unified-theory time. The point of time for this transition is independent of the magnitude of the vorticity. During the Guth inflationary era the vorticity decays by a factor of the order 10"-"1"4"2.

International Nuclear Information System (INIS)

We describe exact cosmological solutions with rotation and expansion in the low-energy effective string theory. These models are spatially homogeneous (closed Bianchi type IX) and they belong to the family of shear-free metrics which are causal (no closed timelike curves are allowed), admit no parallax effects and do not disturb the isotropy of the background radiation. The dilaton and the axion fields are nontrivial, in general, and we consider both cases with and without the central charge (effective cosmological constant).

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The propriety of the cosmic no-hair conjecture to the Bianchi-type-IX spacetime is discussed from a quantum cosmological point of view. It is shown that most, but not all, classical universes which are created quantum cosmologically are inflationary. The probability of inflation among such universes is also discussed.

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Nordstroem's first theory of gravitation, which is a Lorentz covariant scalar theory, is discussed, and the cosmological solution to the field equation is derived. It is shown that there are two physically equivalent representations of the theory that differ in the system of units with which measurements are made. The cosmological solution is found to be an infinite, Euclidean universe with a big bang and a big crunch.

British Library Electronic Table of Contents (United Kingdom)

Neutrinos have recently been shown to have collective phenomenon which causes them to flavor transform near the center of the supernova. These flavor transformations can potentially impact supernova nucleosynthesis, particularly for processes that occur near the core, such as the r-process. In this paper we explore the effects of collective oscillations on a supernova r-process. We find that magnitude of the effect depends senstivitely on the astrophysical conditions?in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. Because of this delicate balance, a more definitive understanding of the astrophysical conditions is necesssary. Here, we explore scenarios based on outflow models currently in ...

CERN Document Server

In this paper, we first calculate the realistic Earth matter effects on the detection of type II supernova neutrinos at the Daya Bay reactor neutrino experiment which is currently under construction. It is found that the Earth matter effects depend on the neutrino incident angle \\theta, the neutrino mass hierarchy \\Delta m_{31}^{2}, the crossing probability at the high resonance region inside the supernova, P_H, the neutrino temperature, T_{\\alpha}, and the pinching parameter in the neutrino spectrum, \\eta_{\\alpha}. We give the expression for the dependence of P_H on the neutrino mixing angle \\theta_{13}. With this we obtain the relations between \\theta_{13} and the event numbers for various reaction channels of supernova neutrinos. Using these relations, we propose a possible way to measure \\theta_{13} smaller than 1.5^\\circ. Such a sensitivity cannot be achieved by the Daya Bay neutrino experiment (the ...

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This review covers research done at Lawrence Livermore National Laboratory in the fields of astronomy and astrophysics. The research areas mentioned are as follows: star evolution, supernovae, and nucleosynthesis; stellar atmospheres and winds; galaxies and the interstellar medium; and high-energy astrophysics.

Science.gov (United States)

There is an increased emphasis on hyphenated techniques such as immunoaffinity LC/MS/MS (IA-LC/MS/MS) or IA-LC/MRM. These techniques offer competitive advantages with respect to sensitivity and selectivity over traditional LC/MS and are complementary to ligand binding assays (LBA) or ELISA's. However, these techniques are not entirely straightforward and there are several tips and tricks to routine sample analysis. We describe here our methods and procedures for how to perform online IA-LC/MS/MS including a detailed protocol for the preparation of antibody (Ab) enrichment columns. We have included sample trapping and Ab methods. Furthermore, we highlight tips, tricks, minimal and optimal approaches. This technology has been shown to be viable for several applications, species and fluids from small molecules to proteins and biomarkers to PK assays. PMID:21872661

British Library Electronic Table of Contents (United Kingdom)

The traffic flow information guidance can improve the operating efficiency of regional traffic. On the basis of the information guidance model and survey data, this paper takes advantage of the VISSIM software to simulate the traffic in a region within the Southwest Second Ring of Beijing constructed by six roads and six intersections and makes a comparative evaluation on the operation of the regional road traffic flow before and after the implementation of the traffic flow information guidance measures. The analysis of five different guided flow cases shows that if the guided left-turn traffic flows in southbound I.A increases from 10% to 30%, the travel time of the left-turn traffic flow in southbound I.A has a reduction from 18% to 42%, and its delay also reduces from 234 s to 164 s. In...

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Recent work on [ital N]=2 supersymmetric Bianchi type IX cosmologies coupled to a scalar field is extended to a general treatment of homogeneous quantum cosmologies with explicitly solvable momentum constraints, i.e., Bianchi types I, II, VII, VIII in addition to the Bianchi type IX, and special cases, namely, the Freidmann universes, the Kantowski-Sachs space, and Taub-NUT space. In addition to the earlier explicit solution of the Wheeler-DeWitt equation for Bianchi type IX, describing a virtual wormhole fluctuation, an additional explicit solution is given and identified with the no-boundary state.''

CERN Document Server

We perform a detailed phase-space analysis of various phantom cosmological models, where the dark energy sector interacts with the dark matter one. We examine whether there exist late-time scaling attractors, corresponding to an accelerating universe and possessing dark energy and dark matter densities of the same order. We find that all the examined models, although accepting stable late-time accelerated solutions, cannot alleviate the coincidence problem, unless one imposes a form of fine-tuning in the model parameters. It seems that interacting phantom cosmology cannot fulfill the basic requirement that led to its construction.

CERN Document Server

This is a design study into the capabilities of the Australian Square Kilometre Array Pathfinder (ASKAP) in performing a full-sky low redshift neutral hydrogen survey, termed WALLABY, and the potential cosmological constraints one can attain from measurement of the matter power spectrum. We find that the full sky survey will likely attain 600,000 redshifts which, when combined with expected Planck CMB data, will constrain the Dark Energy equation of state to 20%, for the first time making cosmological constraints from radio observations competitive with the best existing optical surveys.

CERN Document Server

The discovery that the cosmic expansion is accelerating has been followed by an intense theoretical and experimental response in physics and astronomy. The discovery implies that our most basic notions about how gravity work are violated on cosmological distance scales. One simple fix is the introduction of a cosmological constant into the field equations for general relativity. However, the extremely small value of the cosmological constant, relative to theoretical expectations, has led theorists to explore a wide variety of alternative explanations that involve the introduction of an exotic negative-pressure fluid or a modification of general relativity. Here we briefly review the evidence for cosmic acceleration. We then survey some of the theoretical attempts to account for it, including the cosmological constant, quintessence and its variants, mass-varying neutrinos, and modifications of general ...

CERN Document Server

The next decade promises an observational revolution which will change cosmology forever. The precise measurement of the angular anisotropy of the cosmic microwave background should specify to a few percent all of the parameters of the cosmological model which effect astrophysics. The growth of structure will then be determined (but not yet observed) until gravitational collapse becomes highly non-linear and stars, galaxies and active galactic nuclei (AGN) form. These processes are hard to model with basic physics because they are complex and allow a rich variety of expression. Instead observations will determine when the first stars and quasars formed, and how and when galaxies assembled. If we can reconcile the numerous contradictions which characterize the subject today, cosmology will become a mature subject, founded on the agreement between detailed, inclusive and realistic models, which make precise predictions, and ...

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We investigate the quantum cosmology of spatially homogeneous models with compact spatial sections admitting a u(2) isometry algebra. The metric ansatz in these models is that of Bianchi type IX with two scale factors set to be equal. We apply the Hartle-Hawking no-boundary path integral prescription and find the semi-classical contributions to the wave function. Exact formulae are obtainable for certain contributions and otherwise the limits of large and small anisotropy (for the pure vacuum case) and large spatial volume or small anisotropy (for the case with a positive cosmological constant) are considered. For the pure vacuum case we find no semiclassical components which would correspond to Lorentzian universes. For the case with a cosmological constant the Hartle-Hawking boundary conditions formally constrain one of the parameters in the Lorentzian solutions to be purely imaginary. Possible interpretations of this ...

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The obtained results in presently study demonstrate that the feasibility of the detection of the sentry ganglion in cervix uterine cancer using a boarding by laparoscopic via, being necessary the use of twice labelled as much with patent blue and radioisotope (colloid of labelled rhenium with "9"9"mTc, total dose of 3 MCi) to achieve the identification of the ganglion. (Author)

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We use two-dimensional hydrodynamical simulations to investigate the properties of dense ejecta clumps (bullets) in a core collapse supernova remnant, motivated by the observation of protrusions probably caused by clumps in the Vela supernova remnant. The ejecta, with an inner flat and an outer steep power law density distribution, were assumed to freely expand into an ambient medium with a constant density, $\\sim 0.1$ H atoms cm$^{-3}$ for the case of Vela. At an age of $10^4$ yr, the reverse shock front is expected to have moved back to the center of the remnant. Ejecta clumps with an initial density contrast $\\chi \\sim 100$ relative to their surroundings are found to be rapidly fragmented and decelerated. In order to cause a pronounced protrusion on the blast wave, as observed in the Vela remnant, $\\chi \\sim 1000$ may be required. In this case, the clump should be near the inflection point in the ejecta density profile, at an ejecta ...

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The Thomsen and Frandsen (1983) cosmological test employing the observed correlation between elliptical galaxy surface brightness and scale size in order to avoid problems due to dynamical evolution is presently extended to make use of arbitrary galaxy samples. The explicit dependence on stellar evolution is also demonstrated. On the assumption that this evolution is calculable, an equation for the deceleration parameter entirely in terms of observables is derived. The test is applied to two available samples. 25 references.

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The possibility of having inflation in a renormalizable cosmological model is investigated. The cosmic no-hair conjecture is proved to hold for all Bianchi types except Bianchi type IX. By the use of a conformal transformation on the metric we show that these models are equivalent to the ones described by the Einstein-Hilbert action for gravity minimally coupled to a set of scalar fields with inflationary potentials. Henceforth, we prove that inflationary solutions behave as attractors in solution space, making it a natural event in the evolution of such models.

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The t<0 branch of pre-big bang cosmological scenarios is subject to a gravitational wave instability. The unstable behaviour of tensor perturbations is derived in a very simple way in Hwang's covariant and gauge-invariant formalism developed for extended theories of gravity. A simple interpretation of this instability as the effect of an ''antifriction'' is given, and it is argued that a universe must eventually enter the expanding phase. (orig.)

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The dimensionally reduced effective action of the bosonic sector of the heterotic string in critical dimensions is employed to derive a Wheeler-DeWitt equation for the Bianchi type-IX cosmology. An exact solution is found that becomes strongly peaked around the isotropic limit as the volume of the three-geometry increases. In principle the global O(6,6) symmetry of the effective action can be employed to generate new solutions from the one presented here.

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(B204) The meeting will bring together observers and theorists in a highly interactive format, to further connect the local and cosmological star formation communities. Forward looking talks, aimed at the other communities, will survey terminology, achievements, problems and aspirations. Discussion will focus on the definition of the key questions, how the different communities can help each other, and preparations for the incorporation of realistic star formation into cosmological simulations.

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Supernova explosions within wind-driven bubbles are studied with 2D hydrodynamical calculations. Two different density distributions for the ejecta are considered: (i) a smooth, unfragmented power-law stratification, and (ii) a fragmented distribution. As in 1D models, the presence of the shell of interstellar swept-up matter causes the rapid evolution of the remnant to the radiative phase. The main 2D effects, for both fragmented and unfragmented ejecta, include: (i) substantial chaotic deviations from a purely radial flow in the remnant interior, (ii) efficient turbulent mixing between the ejecta and the shocked wind, resulting in homogenization of the former wind cavity, and (iii) severe distortion of the wind-driven shell by cooling and Rayleigh-Taylor instabilities. (author).

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As an explosion develops in the collapsed core of a massive star, neutrino emission drives convection in a hot bubble of radiation, nucleons, and pairs just outside a proto-neutron star. Shortly thereafter, neutrinos drive a wind-like outflow from the neutron star. In both the convective bubble and the early wind, weak interactions temporarily cause a proton excess (Y{sub e} {approx}> 0.50) to develop in the ejected matter. This situation lasts for at least the first second, and the approximately 0.05-0.1 M{sub {circle_dot}} that is ejected has an unusual composition that may be important for nucleosynthesis. Using tracer particles to follow the conditions in a two-dimensional model of a successful supernova explosion calculated by Janka, Buras, and Rampp (2003), they determine the composition of this material. most of it is helium and {sup 56}Ni. The rest is relatively rare species produced by the decay of proton-rich isotopes unstable to positron emission. ...

CERN Document Server

Cosmological constant a.k.a. dark energy problem is considered to be one major challenge in modern cosmology. Here we present a model where large scale structure formation causes spatially-flat FRW universe to fragment into numerous `FRW islands' surrounded by vacuum. We show that this mechanism can explain the origin of dark energy as well as the late time cosmic acceleration. This explanation of dark energy does not require any exotic matter source nor an extremely fine-tuned cosmological constant. This explanation is given within classical general relativity and relies on the fact that our universe has been undergoing structure formation since its recent past.

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General relativity postulates the Minkowski space-time to be the standard flat geometry against which we compare all curved space-times and the gravitational ground state where particles, quantum fields and their vacuum states are primarily conceived. On the other hand, experimental evidences show that there exists a non-zero cosmological constant, which implies in a deSitter space-time, not compatible with the assumed Minkowski structure. Such inconsistency is shown to be a consequence of the lack of a application independent curvature standard in Riemann's geometry, leading eventually to the cosmological constant problem in general relativity. We show how the curvature standard in Riemann's geometry can be fixed by Nash's theorem on locally embedded Riemannian geometries, which imply in the existence of extra dimensions. The resulting gravitational theory is more general than general relativity, similar to brane-world gravity, but where the ...

CERN Document Server

After mathematicians and physicists had learned that the structure of physical space was not necessarily Euclidean, it became conceivable that the global topological structure of space was non-trivial. In the context of the late 19th century debates on physical space this speculation gave rise to the problem of classifying spaces of constant curvature from a topological point of view. William Kingdon Clifford, Felix Klein and Wilhelm Killing, the latter of whom devoted a substantial amount of work to the topic in the early 1890s, clearly perceived this problem as relevant for both mathematics and natural philosophy (i.e., physics or cosmology). To some extent, a cosmological interest may even be found among those authors who restated the space form problem in more modern terms in the early 20th century, such as Heinz Hopf.

CERN Document Server

Gravitational lensing distorts the cosmic microwave background (CMB) temperature and polarization fields and encodes valuable information on distances and growth rates at intermediate redshifts into the lensed power spectra. The non-Gaussian bandpower covariance induced by the lenses is negligible to l=2000 for all but the B polarization field where it increases the net variance by up to a factor of 10 and favors an observing strategy with 3 times more area than if it were Gaussian. To quantify the cosmological information, we introduce two lensing observables, characterizing nearly all of the information, which simplify the study of non-Gaussian impact, parameter degeneracies, dark energy models, and complementarity with other cosmological probes. Information on the intermediate redshift parameters rapidly becomes limited by constraints on the cold dark matter density and initial amplitude of fluctuations as observations improve. Extraction of ...

International Nuclear Information System (INIS)

CBA/Ca mice were infected by either the intravenous or intraperitoneal route with Mycobacterium microti and the subsequent changes in local macrophage populations examined. Following infection, the number of macrophages increased and they showed greater expression of both MHC Class II molecules. This response was not dependent on viability of the mycobacteria, in contrast to reports with other microorganisms such as Listeria. Studies in sublethally irradiated mice indicated that persistent antigen could give rise to a response after a period of host recovery which was radiation dose dependent. This procedure also highlighted differences in the regulation of different murine class II antigens in vivo, as seen by delayed re-expression of I-E antigens. Macrophage accessory cell function, as assessed by an in vitro T cell proliferation assay, correlated with Ia expression after fixation, but not after indomethacin treatment; this highlights the diverse nature of ...

International Nuclear Information System (INIS)

We investigate the evolution of Type Ib/c supernova (SN Ib/c) progenitors in close binary systems, using new evolutionary models that include the effects of rotation, with initial masses of 12-25 M_s_u_n for the primary components, and of single helium stars with initial masses of 2.8-20 M_s_u_n. We find that, despite the impact of tidal interaction on the rotation of primary stars, the amount of angular momentum retained in the core at the presupernova stage in different binary model sequences converges to a value similar to those found in previous single star models. This amount is large enough to produce millisecond pulsars, but too small to produce magnetars or long gamma-ray bursts. We employ the most up-to-date estimate for the Wolf-Rayet mass-loss rate, and its implications for SN Ib/c progenitors are discussed in detail. In terms of stellar structure, SN Ib/c progenitors in binary systems at solar metallicity are predicted to have a wide range of final ...

Energy Technology Data Exchange (ETDEWEB)

The PIUS reactor utilizes simplified, inherent, passive, or other innovative means to accomplish safety functions. Accordingly, the PIUS reactor is subject to the requirements of 10CFR52.47(b)(2)(i)(A). This regulation requires that the applicant adequately demonstrate the performance of each safety feature, interdependent effects among the safety features, and a sufficient data base on the safety features of the design to assess the analytical tools used for safety analysis. Los Alamos has assessed the quality and completeness of the existing and planned data bases used by Asea Brown Boveri to validate its safety analysis codes and other relevant data bases. Only a limited data base of separate effect and integral tests exist at present. This data base is not adequate to fulfill the requirements of 10CFR52.47(b)(2)(i)(A). Asea Brown Boveri has stated that it plans to conduct more separate effect and integral test programs. If appropriately ...

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The canonical quantum theory of gravity-quantum geometrodynamics (QG)-is applied to the homogeneous Bianchi type IX cosmological model. As a result, a framework for the quantum theory of homogeneous cosmologies is developed. We show that the theory is internally consistent and prove that it possesses the correct classical limit (the theory of general relativity). To emphasize the special role that the constraints play in this new theory, we compare it to the traditional ADM square-root and Wheeler-DeWitt quantization schemes. We show that, unlike traditional approaches, QG leads to a well-defined Schroedinger equation for the wavefunction of the universe that is inherently coupled to the expectation value of the constraint equations. This coupling to the constraints is responsible for the appearance of a coherent spacetime picture. Thus, the physical meaning of the constraints of the theory is quite different from Dirac's ...

International Nuclear Information System (INIS)

A Monte Carlo simulation of the vacuum Bianchi type-IX (mixmaster) cosmology yields a significant correlation between large universe volume and high anisotropy. An analog of the model's chaotic classical behavior is seen in the break up of the universe wave function at large volume into fingers in the corners of the minisuperspace anisotropy potential.

International Nuclear Information System (INIS)

It is proven that there do not exist any diagonal Bianchi type-IX universes which expand for an infinite time, provided only that the matter satisfies the dominant energy condition and has non-negative average principal pressures.

International Nuclear Information System (INIS)

The energy-momentum tensor of a massless spinor field is constructed and studied based on the previously proposed interpretation of quantum effects of such a field in the anisotropic metric of Bianchi type IX. The characteristic properties of the energy-momentum tensor in the mixed universe model are discussed.

International Nuclear Information System (INIS)

We investigate the quantum cosmology of spatially homogeneous models with compact spatial sections admitting a u(2) isometry algebra. The metric ansatz in these models is that of Bianchi type IX with two scale factors set to be equal. We apply the Hartle-Hawking no-boundary path integral prescription and find the semi-classical contributions to the wave function. Exact formulae are obtainable for certain contributions and otherwise the limits of large and small anisotropy (for the pure vacuum case) and large spatial volume or small anisotropy (for the case with a positive cosmological constant) are considered. For the pure vacuum case we find no rapidly oscillating semiclassical components in the wave function, and hence do not recover lorentzian space-time as a prediction of the no-boundary proposal. For the case with a cosmological constant the wave function does contain rapidly oscillating components and thus predicts ...

CERN Document Server

We investigate several varying-mass dark-matter particle models in the framework of phantom cosmology. We examine whether there exist late-time cosmological solutions, corresponding to an accelerating universe and possessing dark energy and dark matter densities of the same order. Imposing exponential or power-law potentials and exponential or power-law mass dependence, we conclude that the coincidence problem cannot be solved or even alleviated. Thus, if dark energy is attributed to the phantom paradigm, varying-mass dark matter models cannot fulfill the basic requirement that led to their construction.

Energy Technology Data Exchange (ETDEWEB)

The geodesic equation for space-like objects moving along a circular trajectory in the expanding universe is considered. Our analysis leads to the conclusion that ancient cosmological tachyons may exist in the present-day world and may play an important role in (i) the internal structure of hadrons conceived as nonlocal objects called strings, (ii) the T-symmetry violation observed in the weak K-decays, (iii) the multidimensional unified field theories of Kaluza-Klein type, and in (iv) the classical models of charged particles which combine ordinary electromagnetism with a self-interacting version of Newtonian gravity. 18 refs.

CERN Document Server

The collapse of a massive star's core, followed by a neutrino-driven, asymmetric supernova explosion, can naturally lead to pulsar recoils and neutron star kicks. Here, we present a two-dimensional, radiation-hydrodynamic simulation in which core collapse leads to significant acceleration of a fully-formed, nascent neutron star (NS) via an induced, neutrino-driven explosion. During the explosion, a ~10% anisotropy in the low-mass, high-velocity ejecta lead to recoil of the high-mass neutron star. At the end of our simulation, the NS has achieved a velocity of ~150 km s$^{-1}$ and is accelerating at ~350 km s$^{-2}$, but has yet to reach the ballistic regime. The recoil is due almost entirely to hydrodynamical processes, with anisotropic neutrino emission contributing less than 2% to the overall kick magnitude. Since the observed distribution of neutron star kick velocities peaks at ~300-400 km s$^{-1}$, recoil due to anisotropic core-collapse ...

CERN Document Server

NGC 2770 has been the host of three supernovae of Type Ib during the last 10 years, SN 1999eh, SN 2007uy and SN 2008D. SN 2008D attracted special attention due to the serendipitous discovery of an associated X-ray transient. In this paper, we study the properties of NGC 2770 and specifically the three SN sites to investigate whether this galaxy is in any way peculiar to cause a high frequency of SNe Ib. We model the global SED of the galaxy from broadband data and derive a star-formation and SN rate comparable to the values of the Milky Way. We further study the galaxy using longslit spectroscopy covering the major axis and the three SN sites. From the spectroscopic study we find subsolar metallicities for the SN sites, a high extinction and a moderate star-formation rate. In a high resolution spectrum, we also detect diffuse interstellar bands in the line-of-sight towards SN 2008. A comparison of NGC 2770 to the global properties of a galaxy sample with high SN ...

Science.gov (United States)

The Micro-X instrument is a rocket borne, X-ray imaging spectrometer planned for launch in October 2011. An array of 128 Transition Edge Sensors (TESs) on a 600 micron pitch will observe incoming photons in the 0.2-3 keV energy band with an energy resolution of 2-4 eV at 1 keV. X-rays will be focused onto the TES array by a conically approximated Wolter optic with an effective area of 300 cm^2 giving the instrument a field of view of 11.8 arcmin. This performance will constitute a substantial improvement over current non-dispersive detectors for X-ray spectroscopy of extended sources and will be the first demonstration of a TES-based microcalorimeter in space. The TESs will utilize the 50 mK stage of an Adiabatic Demagnetization Refrigerator (ADR) as a heat bath, and will be read out by a SQUID time division multiplexer. The first flight of the Micro-X instrument will observe the Puppis A supernova remnant. Future targets include the core of the Virgo cluster and ...

International Nuclear Information System (INIS)

Nucleosynthesis and energy production in stellar environments depend critically on nuclear reaction cross sections. Reactions induced by alpha particles are important in the helium burning stage of stars, novae, and supernovae events. They involve light to medium weight nuclei up to about Z=32, and center-of-mass energies up to about 20 MeV. We are working on a project to compile and evaluate cross section data for alpha-induced reactions. These data will eventually be used to derive #alpha#-nucleus potential parameters. (author)

Science.gov (United States)

The article examines the contribution of the Military Medical Academy as an educational, research and medical institutions in the establishment and development of the national Russian manned spaceflight. Lists the names of the Academy's scientists, working in laboratories and in the Cosmonaut Training Center. In 1958 the academy was formed Department of Aviation Medicine from the research laboratories of aviation medicine, psychophysiology, and encephalography, a division of pressure chambers and furnaces. Direct contribution to the preparation of the first manned space flight made by graduates of the academy, E.A. Karpov (the first chief of Cosmonauts Training Center. Yuri Gagarin) and I.A. Kolosov. Over the half century history of the Russian Space Military Medical Academy, prepared and sent to the CPC Gagarin more than 110 of its graduates. PMID:21770320

Energy Technology Data Exchange (ETDEWEB)

Recently the authors showed that tetrazolium salts can be obtained during the oxidation of substituted 1,3,5-triarylformazans with potassium permanganate in a two-phase organic solvent-water system. The role of phase-transfer catalyst in this reaction is played by the tetrazolium salt, which is formed in a small amount as the result of oxidation of the formazan at the phase boundary. The method is distinguished by its extreme simplicity. However, the yield of the tetrazolium salts fluctuates within wide limits and does not exceed 62%. This is due to the fact that as the reaction proceeds the pH of the aqueous phase increases from 6 to 12. At the same time it is known that tetrazolium salts are unstable in aqueous alkaline solutions. They found that if the aqueous phase is replaced by aqueous hydrochloric acid (5 wt. %) the yields of the tetrazolium salts (Ia-g) are increased to 70-87%. For convenience of isolation the readily water-soluble tetrazolium chlorides ...

CERN Document Server

A (n +1)-dimensional Einstein-Gauss-Bonnet (EGB) model is considered. For diagonal cosmological type metrics the equations of motion are reduced to a set of Lagrange equations. The effective Lagrangian contains two minisuperspace metrics on R^n. The first one is the well-known 2-metric of pseudo-Euclidean signature and the second one is the Finslerian 4-metric that is proportional to n-dimensional Berwald-Moor 4-metric. When a synchronous-like time gauge is considered the equations of motion are reduced to an autonomous system of first order differential equations. For the case of the pure Gauss-Bonnet model two exact solutions with power-law and exponential dependence of scale factors (w.r.t. synchronous-like variable) are obtained. In cosmological case the first solution was obtained earlier by A. Toporensky and P. Tretyakov for n = 5 (and verified for n = 6,7). A generalization of the effective Lagrangian to the Lowelock case is conjectured. ...

CERN Document Server

A new N-body and hydrodynamical code, called RAMSES, is presented. It has been designed to study structure formation in the universe with high spatial resolution. The code is based on Adaptive Mesh Refinement (AMR) technique, with a tree based data structure allowing recursive grid refinements on a cell-by-cell basis. The N-body solver is very similar to the one developed for the ART code (Kravtsov et al. 97), with minor differences in the exact implementation. The hydrodynamical solver is based on a second-order Godunov method, a modern shock-capturing scheme known to compute accurately the thermal history of the fluid component. The accuracy of the code is carefully estimated using various test cases, from pure gas dynamical tests to cosmological ones. The specific refinement strategy used in cosmological simulations is described, and potential spurious effects associated to shock waves propagation in the resulting AMR grid are discussed and ...

CERN Document Server

We provide a quantitative assessment of the probability distribution function of the concentration parameter of galaxy clusters. We do so by using the probability distribution function of halo formation times, calculated by means of the excursion set formalism, and a formation redshift-concentration scaling derived from results of N-body simulations. Our results suggest that the observed high concentrations of several clusters are quite unlikely in the standard Lambda CDM cosmological model, but that due to various inherent uncertainties, the statistical range of the predicted distribution may be significantly wider than commonly acknowledged. In addition, the probability distribution function of the Einstein radius of A1689 is evaluated, confirming that the observed value of ~45" +/- 5" is very improbable in the currently favoured cosmological model. If, however, a variance of ~20% in the theoretically predicted value of the virial radius is ...

CERN Document Server

Peculiar velocities induce apparent line of sight displacements of galaxies in redshift space, distorting the pattern of clustering in the radial versus transverse directions. On large scales, the amplitude of the distortion yields a measure of the dimensionless linear growth rate \\ff of fluctuations, which is related to the cosmological density \\Omega and the linear bias factor b in linearly biassed standard cosmology by \\ff \\approx \\Omega^{0.6} /b. To make the maximum statistical use of the data in a wide angle redshift survey, and for the greatest accuracy, the spherical character of the distortion needs to be treated properly, rather than in the simpler plane parallel approximation. In the linear regime, the redshift space correlation function is described by a spherical distortion operator acting on the true correlation function. It is pointed out here that there exists an operator, which is essentially the logarithmic derivative with ...

CERN Document Server

The Fourier transform of cosmological density perturbations can be represented in terms of amplitudes and phases for each Fourier mode. We investigate the phase evolution of these modes using a mixture of analytical and numerical techniques. Using a toy model of one-dimensional perturbations evolving under the Zel'dovich approximation as an initial motivation, we develop a statistic that quantifies the information content of the distribution of phases. Using numerical simulations beginning with more realistic Gaussian random-phase initial conditions, we show that the information content of the phases grows from zero in the initial conditions, first slowly and then rapidly when structures become non-linear. This growth of phase information can be expressed in terms of an effective entropy: Gaussian initial conditions are a maximum entropy realisation of the initial power spectrum, gravitational evolution decreases the phase entropy. We show that our definition of ...

CERN Document Server

The Kosambi-Cartan-Chern (KCC) theory represents a powerful mathematical method for the analysis of dynamical systems. In this approach one describes the evolution of a dynamical system in geometric terms, by considering it as a geodesic in a Finsler space. By associating a non-linear connection and a Berwald type connection to the dynamical system, five geometrical invariants are obtained, with the second invariant giving the Jacobi stability of the system. The Jacobi (in)stability is a natural generalization of the (in)stability of the geodesic flow on a differentiable manifold endowed with a metric (Riemannian or Finslerian) to the non-metric setting. In the present paper we review the basic mathematical formalism of the KCC theory, and present some specific applications of this method in general relativity, cosmology and astrophysics. In particular we investigate the Jacobi stability of the general relativistic static fluid sphere with a linear barotropic ...

International Nuclear Information System (INIS)

Within the framework of the Bianchi type-IX homogeneous space, we set up a system of coupled equations for the cosmic scale factors, scalar field, and radiative energy density. At the tree level, the equations are written in a self-consistent, Hartree-Fock form. For phi"4 theory, the system of nine first-order differential equations is solved numerically for a varying ratio of the energy of anisotropy to the vacuum energy. As the vacuum energy increases, there appears to be less reheating, since the energy of anisotropy is more efficiently converted into isotropic expansion. If the energy of anisotropy is large enough, the inflationary phase is prevented. In this case, a series of cosmological phase transitions will take place each time the square of the effective mass changes its sign.

CERN Document Server

Model selection aims to determine which theoretical models are most plausible given some data, without necessarily asking about the preferred values of the model parameters. A common model selection question is to ask when new data require introduction of an additional parameter, describing a newly-discovered physical effect. We review several model selection statistics, and then focus on use of the Bayesian evidence, which implements the usual Bayesian analysis framework at the level of models rather than parameters. We describe our CosmoNest code, which is the first computationally-efficient implementation of Bayesian model selection in a cosmological context. We apply it to recent WMAP satellite data, examining the need for a perturbation spectral index differing from the scale-invariant (Harrison-Zel'dovich) case.

Energy Technology Data Exchange (ETDEWEB)

The relative merits and difficlties of the primary and secondry origin hypotheses for the observed cosmic-ray antiprotons, including the new low-energy measurement of Buffington, et al are discussed. We conclude that the cosmic-ray antiproton data may be evidence for antimatter galaxies and baryon symmetric cosmology. The present bar P data are consistent with a primary extragalactic component having /p /equiv 1+/- 3.2/0.7x10 to the -4 independent of energy. We propose that the primary extragalactic cosmic ray antiprotons are most likely from active galaxies and that expected disintegration of bar alpha/alpha ban alpha/alpha. We further predict a value for ban alpha/alpha /equiv 10 to the -5, within range of future cosmic ray detectors.

International Nuclear Information System (INIS)

We investigate the asymptotic properties of the Bianchi type IX cosmological model in the brane-world scenario. The matter content is assumed to be a combination of a perfect fluid and a minimimally coupled scalar field that is restricted to the brane. A detailed qualitative analysis of the Bianchi type IX brane-world containing a scalar field having an exponential potential is undertaken. It is found that the brane-Robertson-Walker solution is a local source for the expanding Bianchi type IX models, and if k"2<2 the ever-expanding Bianchi IX models asymptote to the power-law inflationary solution. The only other local sink is the contracting brane-Robertson Walker solution. An analysis of the Bianchi type IX models with a scalar field with a general potential is discussed, and it is shown that in the case of expanding models, for physical scalar field potentials close to the initial singularity, the scalar field is effectively massless, and the solution is ...

International Nuclear Information System (INIS)

The propagating of tachyons in an expanding universe is discussed. It is shown that a primordial tachyon in the big-bang universe cannot survive unless it had very large energy initially. In an indefinitely expanding universe the tachyon trajectory turns back in time. This time barrier is found to exist even in the quantum mechanical discussion of tachyons. This property is used to set limits on the mass of a tachyon. The possible astronomical checks on the hypothesis that neutrinos or photons may be tachyonic are also discussed. (author).

International Nuclear Information System (INIS)

We demonstrate the existence of shear-free cosmological models with rotation and expansion which support inflationary scenarios. The corresponding metrics belong to the family of spatially homogeneous models with the geometry of the closed universe (Bianchi type IX). We show that the global vorticity does not prevent inflation and can even accelerate it.

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The baryogenesis process in the early hot universe is investigated by means of relativistic kinetic theory. An exact solution to the kinetic equations for supermassive bosons serves to refine previous results: the optimum baryon-production domain is now complemented by bosons of low mass, thus removing the cosmological lower bound that had limited the mass of superheavy bosons. 14 references.

Energy Technology Data Exchange (ETDEWEB)

It is proven that there do not exist any Bianchi type-IX universes which expand for an infinite time, provided only that the matter satisfies the dominant energy condition and has non-negative average pressure (i.e., a non-negative trace of the spatial projection of the stress-energy tensor). This generalizes a proof recently given by us for the case of diagonal Bianchi type-IX solutions.

CERN Document Server

We study the dynamics of the scalar tensor cosmological model in the presence of tachyon field. In an alternative approach, in two exponential and power law form of the scalar field functions in the model, field equations are solved by simultaneously best fitting the model parameters with the most recent observational data. This approach gives us an observationally verified interpretation of the dynamics of the universe. We then discuss the best fitted of equation of state parameter, the statefinder parameters and the reconstructed scalar field in the model.

Energy Technology Data Exchange (ETDEWEB)

We analyze the behavior of some Bianchi type-IX, mixmaster cosmological models possessing extra dimensions. We find that, unlike the three-dimensional case, they do not exhibit chaotic behavior on approach to their initial singularity. A finite sequence of stochastic mixmaster oscillations is, in general, replaced by monotonic contraction of the three-space scale factors on approach to a singularity whenever additional spatial dimensions exist with the metric form we consider.

Energy Technology Data Exchange (ETDEWEB)

We apply Hawking's proposal for the initial state of the Universe to a rotating Bianchi type-IX minisuperspace model in order to examine the problem of rotation in a closed cosmology. Using the Feynman path-integral techniques instead of the Wheeler-DeWitt equation, we are able to say that for a small angular velocity the closed Friedmann-Robertson-Walker model is indeed the most probable initial state for the Universe.

International Nuclear Information System (INIS)

Spatially homogeneous space-times of Bianchi type IX are considered. A general scheme for the derivation of exact solutions of Einstein's equations corresponding to perfect fluid plus pure radiation fields is outlined. Some simple rotating Bianchi type IX cosmological models are presented. The details of these solutions are also discussed. 9 refs. (author).

Energy Technology Data Exchange (ETDEWEB)

The determination of relative abundances of helium and deuterium in Jupiter and Saturn provides estimates of the primordial abundances of these elements. The values so inferred can be compared with theoretical predictions of the standard model of the big-bang theory as a test of the model and suggest either that deuterium is more efficiently consumed in subsequent nucleosynthesis than hitherto assumed, or that the standard big-bang model should be revised in order for there to have been less production of primordial helium.

Energy Technology Data Exchange (ETDEWEB)

The relative merits and difficulties of the primary and secondary origin hypotheses for the observed cosmic ray antiprotons, including the low energy measurement of Buffington, were examined. It is concluded that the cosmic ray antiproton data may be strong evidence for antimatter galaxies and baryon symmetric cosmology. The present antiproton data are consistent with a primary extragalactic component having antiproton/proton approximately equal to .0032 + or - 0.7.

CERN Document Server

We study the high energy behaviour of Yang-Mills theory under the inclusion of gravity. In the weak-gravity limit, the running gauge coupling receives no contribution from the gravitational sector, if all symmetries are preserved. This holds true with and without cosmological constant. We also show that asymptotic freedom persists in general field-theory-based gravity scenarios including gravitational shielding as well as asymptotically safe gravity.

Science.gov (United States)

Cosmological N-body and hydrodynamic simulations start with a realization of a random density fluctuation field representing a cosmological model at an early epoch. The density field is often replaced by a set of particles whose positions and velocities are set to conform to the desired density field. Each particle represents a cloud of huge number of real particles. Positions and velocities of particles are subsequently integrated by various numerical codes. We have simulated a set of collisionless collapses of Gaussian density peaks by using the PM and P(3) M codes. We find that in cosmological simulations the physics at scales below the mean particle separation(MPS) is dominated by inaccuracies in describing the initial density field, and cannot be studied even by the high force-resolution codes. Since density fluctuations are ill-defined at scales smaller than MPS, it is desirable not to amplify this problem during the ...

Energy Technology Data Exchange (ETDEWEB)

We consider the problem of rotation in a homogeneous Bianchi type IX cosmological model. Studying the Wheeler-De Witt equation corresponding to this minisuperspace, and adopting a particular choice of the factor ordering, we are able to find a particular solution which is strongly peaked about isotropy. This result confirms all the previous investigations in this field, and suggests the conclusion that the machian nature of our universe is the natural, i.e. most likely, outcome of the Planck epoch. (orig.).

Energy Technology Data Exchange (ETDEWEB)

In this paper we discuss a number of astrophysical environments and how improved nuclear data could facilitate a better understanding of them. One area of interest includes proton and alpha-particle reactions with unstable nuclei which are necessary for understanding the nucleosynthesis and energy generation in hot hydrogen-burning environments. Efforts underway at LLNL and elsewhere to develop the technology for the measurement of these reaction rates are discussed. Heavy-element nucleosynthesis in the late stages of red-giant stars and supernovae requires a complete network of neutron capture rates and beta-decay rates for nuclei near and far from stability. Experimental and theoretical efforts at LLNL to supply the input data and to model the nucleosynthetic environments will be outlined. Suggestions are made as to which nuclear data are most critical for the various scenarios. 42 refs., 11 figs., 1 tab.

International Nuclear Information System (INIS)

We identify a source coincident with SN 2009kr in Hubble Space Telescope pre-explosion images. The object appears to be a single point source with an intrinsic color V - I = 1.1 #+-# 0.25 and M_V = -7.6 #+-# 0.6. If this is a single star, it would be a yellow supergiant of log L/L _s_u_n #approx# 5.1 and a mass of 15"+"5 _-_4 M _s_u_n. The spatial resolution does not allow us yet to definitively determine if the progenitor object is a single star, a binary system, or a compact cluster. We show that the early light curve is similar to a Type IIL SN, but the prominent H#alpha# P-Cygni profiles and the signature of the end of a recombination phase are reminiscent of a Type IIP. The evolution of the expanding ejecta will play an important role in understanding the progenitor object.

CERN Document Server

This paper presents a review of the history, motivation and current status of high energy neutrino telescopes. Many years after these detectors were first conceived, the operation of kilometer-cubed scale detectors is finally on the horizon at both the South Pole and in the Mediterranean Sea. These new detectors will perhaps provide us the first view of high energy astrophysical objects with a new messenger particle and provide us with our first real glimpse of the distant universe at energies above those accessible by gamma-ray instruments. Some of the topics that can be addressed by these new instruments include the origin of cosmic rays, the nature of dark matter, and the mechanisms at work in high energy astrophysical objects such as gamma-ray bursts, active galactic nuclei, pulsar wind nebula and supernova remnants.

DEFF Research Database (Denmark)

The recently observed X-ray synchrotron emission from four supernova remnants (SNRs) has strengthened the evidence that cosmic-ray electrons are accelerated in SNRs. We show that if this is indeed the case, the local electron spectrum will be strongly time-dependent, at least above roughly 30 GeV. The time dependence stems from the Poisson fluctuations in the number of SNRs within a certain volume and within a certain time interval. As far as cosmic-ray electrons are concerned, the Galaxy looks like actively bubbling Swiss cheese rather than a steady, homogeneously filled system. Our finding has important consequences for studies of the Galactic diffuse gamma-ray emission, for which a strong excess over model predictions above 1 GeV has recently been reported. While these models relied on an electron injection spectrum with index 2.4 (chosen to fit the local electron flux up to 1 TeV), we show that an electron injection index of around 2.0 would (1) be consistent ...

Energy Technology Data Exchange (ETDEWEB)

We consider spatially homogeneous (but generally non-isotropic) cosmologies in the recently proposed Horava-Lifshitz gravity and compare them to those of general relativity using Hamiltonian methods. In all cases, the problem is described by an effective point particle moving in a potential well with exponentially steep walls. Focusing on the closed-space cosmological model (Bianchi type IX), the mixmaster dynamics is now completely dominated by the quadratic Cotton tensor potential term for a very small volume of the universe. Unlike general relativity, where the evolution toward the initial singularity always exhibits chaotic behavior with alternating Kasner epochs, the anisotropic universe in Horava-Lifshitz gravity (with parameter lambda > 1/3) is described by a particle moving in a frozen potential well with fixed (but arbitrary) energy E. Alternating Kasner epochs still provide a good description of the early universe for very ...

CERN Document Server

Lyman-limit absorption systems can play many important roles during and after cosmological reionization. Unfortunately, due to the prohibitively large dynamic range required, it is impossible to self-consistently include these systems in cosmological simulations. Using fast and versatile semi-numeric simulations, we systematically explore the spatial distribution of absorption systems during and following reionization. We self-calibrate the resulting number of absorbers to the mean free path (mfp) of the ionizing ultraviolet background (UVB), and present results at a given mfp and neutral hydrogen fraction. We use a simple optical depth criterion to identify the locations of absorbers. Our approach is fairly robust to uncertainties such as missing subgrid structure. Unlike at lower redshifts where the UVB is relatively uniform, at higher redshifts the fluctuations in the UVB and the HII morphology of reionization can drive the large-scale ...

International Nuclear Information System (INIS)

To systematically analyze the dynamical implications of the matter content in cosmology, we generalize earlier dynamical systems approaches so that perfect fluids with a general barotropic equation of state can be treated. We focus on locally rotationally symmetric Bianchi type IX and Kantowski-Sachs orthogonal perfect fluid models, since such models exhibit a particularly rich dynamical structure and also illustrate typical features of more general cases. For these models, we recast Einstein's field equations into a regular system on a compact state space, which is the basis for our analysis. We prove that models expand from a singularity and recollapse to a singularity when the perfect fluid satisfies the strong energy condition. When the matter source admits Einstein's static model, we present a comprehensive dynamical description, which includes the qualitative asymptotic behavior, of models in the neighborhood of the Einstein model; the results refute earlier ...

Energy Technology Data Exchange (ETDEWEB)

The quantum behavior of the vacuum Bianchi type-IX universe with the cosmological constant is investigated in terms of the Ashtekar variables. An exact solution to the quantum Hamiltonian constraint in the holomorphic representation is given. This solution reduces to the Hartle-Hawking wave function in the spatially isotropic sector and extends in the triad representation to the classically forbidden region where the determinant of the spatial metric becomes negative. The analysis of the quantum Robertson-Walker universe indicates that if the superspace is extended to such a classically forbidden region, the holomorphic representation picks up some restricted class of solutions in general. This observation leads to a new ansatz on the boundary condition of the Universe. In particular, the behavior of the Lorentzian and Euclidean WKB orbits corresponding to the solution suggests a new picture on the semiclassical behavior of the quantum Universe: that the Universe ...

CERN Document Server

Gravitational lensing by the dual cusp catastrophes of the cold dark matter (CDM) caustic rings at cosmological distances may provide the tantalizing opportunity to detect CDM indirectly, and discriminate between axions and weakly interacting massive particles (WIMPs). Caustics are places where the CDM particles are naturally focussed. Our focus is upon the caustic rings which are closed tubes whose cross-section is an elliptic umbilic catastrophe with three dual cusps. A caustic ring has a specific density profile, a specific geometry and, therefore, precisely calculable gravitational lensing signatures. The magnification monotonically increases as the line of sight approaches to the cusps where it diverges in the limit of zero velocity dispersion. In this limit, we find 37% magnification at a sample point near the outer cusps of the CDM caustic rings at cosmological distances. In the presence of finite velocity dispersion, the lower and upper ...

CERN Document Server

A diagrammatic approach to calculate n-point correlators of the primordial curvature perturbation \\zeta was developed a few years ago following the spirit of the Feynman rules in Quantum Field Theory. The methodology is very useful and time-saving, as it is for the case of the Feynman rules in the particle physics context, but, unfortunately, is not very well known by the cosmology community. In the present work, we extend such an approach in order to include not only scalar field perturbations as the generators of \\zeta, but also vector field perturbations. The purpose is twofold: first, we would like the diagrammatic approach (which we would call the Feynman-like rules) to become widespread among the cosmology community; second, we intend to give an easy tool to formulate any correlator of \\zeta for those cases that involve vector field perturbations and that, therefore, may generate prolonged stages of anisotropic expansion and/or ...

CERN Document Server

The detailed formulation for loop quantum cosmology (LQC) in the Bianchi I model with a scalar massless field has been constructed. In this paper, its effective dynamics is studied in two improved strategies for implementing the LQC discreteness corrections. Both schemes show that the big bang is replaced by the big bounces, which take place up to three times, once in each diagonal direction, when the area or volume scale factor approaches the critical values in the Planck regime measured by the reference of the scalar field momentum. These two strategies give different evolutions: In one scheme, the effective dynamics is independent of the choice of the finite sized cell prescribed to make Hamiltonian finite; in the other, the effective dynamics reacts to the macroscopic scales introduced by the boundary conditions. Both schemes reveal interesting symmetries of scaling, which are reminiscent of the relational interpretation of quantum mechanics and also suggest ...

International Nuclear Information System (INIS)

We find instanton/cosmological solutions with biaxial Bianchi-IX symmetry, involving nontrivial spatial dependence of the CP"1-CP"2-sigma-models coupled to gravity. Such manifolds arise in N = 1, d 4 supergravity with supermatter actions and hence the solutions can be embedded in supergravity. There is a natural way in which the standard coordinates of these manifolds can be mapped into the four-dimensional physical space. Due to its special symmetry, we start with CP"2 with its corresponding scalar ansatz; this further requires the spacetime to be SU(2) x U(1)-invariant. The problem then reduces to a set of ordinary differential equations whose analytical properties and solutions are discussed. Among the solutions there is a surprising, special family of exact solutions which owe their existence to the nontrivial topology of CP"2 and are in 1-1 correspondence with matter-free Bianchi-IX metrics. These solutions can also be found by coupling CP"1 to gravity. The ...

CERN Document Server

A decreasing gravitational constant, G, coupled with angular momentum conservation is expected to increrase a planetary semimajor axis, a, as \\dot a/a=-\\dot G/G. Analysis of lunar laser ranging data strongly limits such temporal variations and constrains a local (~1 AU) scale expansion of the solar system as \\dot a/a=-\\dot G/G =-(4\\pm9)\\times10^{-13} yr^{-1}, including that due to cosmological effects.

Energy Technology Data Exchange (ETDEWEB)

We study an analytical solution to the Einstein's equations in 2 + 1-dimensions. The space-time is dynamical and has a line symmetry. The matter content is a minimally coupled, massless, scalar field. Depending on the value of certain parameters, this solution represents three distinct space-times. The first one is at space-time. Then, we have a big bang model with a negative curvature scalar and a real scalar field. The last case is a big bang model with event horizons where the curvature scalar vanishes and the scalar field changes from real to purely imaginary. (author)

Energy Technology Data Exchange (ETDEWEB)

This paper reviews and elaborates on the issue of the dilaton transformation under the usual {tau} {yields} {alpha}{prime}/{tau} target space duality and its non-static generalization (or {sigma}-model duality). It is found that the transformation law {tau} {yields} {alpha}{prime}/{tau}, {phi} {yields} {phi} In ({tau}/{alpha}{prime}) which guarantees duality at the one-loop {sigma}-model level should be modified at two (and higher) loop order. The non-static duality is illustrated on the example of cosmological solutions in D {ge} 2 with time-dependent radii of space torus.

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The diagonal and symmetric Bianchi type IX models are coupled to a homogeneous spinor field. An action for the combined fields is constructed, where the orthonormal basis used is given explicitly in terms of the metric. This allows one to vary the action with respect to the metric and the spinor fields only. Next, a Hamiltonian formulation is given, and a qualitative solution for the problem is presented. We also show that the k = +1 FRW (Friedmann--Robertson--Walker) model is not compatible with a homogeneous spinor field, while the more complicated models are.

Energy Technology Data Exchange (ETDEWEB)

The authors draw the story of the concept of infinity in sciences from the ancient Greek civilization to modern times, from the Greek idea of atom to quantum physics and cosmology. It is shown how what was considered as limits in ancient times, have been progressively seen as unknown worlds, and are now being investigated with the use of big machines like particle accelerators. This book is composed of 3 main chapters: 1) the quest for the infinitely big, 2) the quest for the infinitely small, and 3) the big-bang theory that appears as the meeting point of the 2 infinites. (A.C.)

International Nuclear Information System (INIS)

We investigate the dynamics of an 11-dimensional homogeneous cosmological model. We assume that the t = const hypersurfaces are products of a 3-dimensional Bianchi type-IX space and a 7-dimensional torus. Most results of our investigation hold when the 7-dimensional torus is replaced by an m-dimensional torus T/sup m/. We show that for a large class of vacuum solutions the physical space expands while the microspace contracts providing a natural mechanism of dimensional reduction. Matter satisfying a simple barotropic equation of state always breaks the process of dynamical dimensional reduction. With special attention we study the behavior of our model close to the initial singularity. In contrast with the 4-dimensional Bianchi type-IX cosmological model the Kasner solution always describes an approach to the initial singularity. We study the transition from the Kasner regime to the oscillatory regime. We show that matter does not ...

CERN Document Server

Observations of the Type II-P (plateau) Supernova (SN) 1999em and Type IIn (narrow emission line) SN 1998S have enabled estimation of the profile of the SN ejecta, the structure of the circumstellar medium (CSM) established by the pre-SN stellar wind, and the nature of the shock interaction. SN 1999em is the first and only Type II-P detected at both X-ray and radio wavelengths. It is the least radio luminous and one of the least X-ray luminous SN ever detected (except for the unusual and very close SN 1987A). The Chandra X-ray data indicate non-radiative interaction of SN ejecta with a power-law density profile (rho \\propto r^{-n} with n ~ 7) with a pre-SN wind with a low mass loss rate of ~2 \\times 10^{-6} Msun/yr for a wind velocity of 10 km/sec, in close agreement with radio mass-loss rate estimates. The Chandra data show an unexpected, temporary rise in the 0.4--2.0 keV X-ray flux at ~100 days after explosion. SN 1998S appears reasonably typical of Type IIn ...

International Nuclear Information System (INIS)

We calculated the energies of asymmetric nuclear matter at zero and finite temperatures with the cluster variational method. At zero temperature, the expectation value of the two-body Hamiltonian composed of the kinetic energies and the AV18 two-body forces is calculated with the Jastrow wave function in the two-body cluster approximation. The obtained two-body energy is in good agreement with the result with the Fermi Hypernetted Chain (FHNC) calculation by Akmal et al. The energy caused by the UIX three-body forces is treated somewhat phenomenologically so that the total energy reproduces the empirical saturation point. Furthermore, the parameters included in the three-body energy are readjusted so that the Thomas-Fermi (TF) calculations with use of the obtained energy of nuclear matter reproduce the gross feature of the experimental data on atomic nuclei. The nuclear species in the neutron star crust obtained by the TF calculation are reasonable. The free energies of asymmetric ...

CERN Document Server

Neutrino emission drives neutron star cooling for the first several hundreds of years after its birth. Given the low energy ($\\sim$ keV) nature of this process, one expects very few nonstandard particle physics contributions which could affect this rate. Requiring that any new physics contributions involve light degrees of freedom, one of the likely candidates which can affect the cooling process would be a nonzero magnetic moment for the neutrino. To illustrate, we compute the emission rate for neutrino pair bremsstrahlung in neutron-neutron scattering through photon-neutrino magnetic moment coupling. We also present analogous differential rates for neutrino scattering off nucleons and electrons that determine neutrino opacities in supernovae. Employing current upper bounds from collider experiments on the tau magnetic moment, we find that the neutrino emission rate can exceed the rate through neutral current electroweak interaction by a factor two, signalling ...

CERN Document Server

We review X-ray plasma diagnostics based on the line ratios of He-like ions. Triplet/singlet line intensities can be used to determine electronic temperature and density, and were first developed for the study of the solar corona. Since the launches of the X-ray satellites Chandra and XMM-Newton, these diagnostics have been extended and used (from CV to Si XIII) for a wide variety of astrophysical plasmas such as stellar coronae, supernova remnants, solar system objects, active galactic nuclei, and X-ray binaries. Moreover, the intensities of He-like ions can be used to determine the ionization process(es) at work, as well as the distance between the X-ray plasma and the UV emission source for example in hot stars. In the near future thanks to the next generation of X-ray satellites (e.g., Astro-H and IXO), higher-Z He-like lines (e.g., iron) will be resolved, allowing plasmas with higher temperatures and densities to be probed. Moreover, the so-called satellite ...

International Nuclear Information System (INIS)

Pulsations driven by partial ionization of hydrogen in the envelope are often considered important for driving winds from red supergiants (RSGs). In particular, it has been suggested by some authors that the pulsation growth rate in an RSG can be high enough to trigger an unusually strong wind (or a superwind), when the luminosity-to-mass ratio becomes sufficiently large. Using both hydrostatic and hydrodynamic stellar evolution models with initial masses ranging from 15 to 40 M_s_u_n, we investigate (1) how the pulsation growth rate depends on the global parameters of supergiant stars and (2) what would be the consequences of a pulsation-driven superwind, if it occurred, for the late stages of massive star evolution. We suggest that such a superwind history would be marked by a runaway increase, followed by a sudden decrease, of the wind's mass-loss rate. The impact on the late evolution of massive stars would be substantial, with stars losing a huge fraction of their H-envelope even ...

International Nuclear Information System (INIS)

We report the detection of X-ray pulsations with a period of ?315.87 ms from the 2009 XMM-Newton observation for the radio-quiet ?-ray pulsar, LAT PSR J0007+7303, centered in the supernova remnant CTA 1. The detected pulsed period is consistent with the ?-ray periodicity at the same epoch found with the Fermi Gamma-ray Space Telescope. The broader sinusoidal structure in the folded light curve of the X-ray emission is dissimilar to that of the ?-ray emission, and the phase of the peak is about 0.5 shifting from the peak in the ?-ray bands, indicating that the main component of the X-rays originates from different sites of the pulsar. We conclude that the main component of the X-ray pulsation is contributed by the thermal emission from the neutron star. Although with a significantly different characteristic age, PSR J0007+7303 is similar to Geminga in emission properties of X-rays and ?-rays; this makes PSR J0007+7303 the second radio-quiet ?-ray pulsar with ...

Energy Technology Data Exchange (ETDEWEB)

We give relations for the embedding of spatially-flat Friedmann-Robertson-Walker cosmological models of Einstein's theory in flat manifolds of the type used in Kaluza-Klein theory. We present embedding diagrams that depict different 4D universes as hypersurfaces in a higher-dimensional flat manifold. The morphology of the hypersurfaces is found to depend on the equation of state of the matter. The hypersurfaces possess a line-like curvature singularity infinitesimally close to the t 0{sup +} 3-surface, where t is the time expired since the big bang. The family of timelike comoving geodesics on any given hypersurface is found to have a caustic on the singular line, which we conclude is the 5D position of the point-like big bang.

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The primary aims of the BESS-Polar program are precise measurements of the low-energy antiproton spectrum and search for cosmologically significant antimatter, which would provide new clues to understand the early Universe. The second flight (BESS-Polar II) over Antarctica was successfully carried out in December 2007 - January 2008. We performed 24.5 days scientific observation just at the solar minimum. The payload worked well during the flight and 4.7 billion cosmic-ray events were collected, which corresponds to 10-20 times statistics of the BESS data taken in the previous solar minimum period (1995 and 1997). Based on the BESS-Polar II data, we will present recent preliminary results of cosmic-ray antiproton measurements and sensitive search for antimatter. (authors)

CERN Document Server

Relativistic strongly magnetized winds outflowing from fast-rotating compact objects like millisecond pulsars with surface magnetic fields of $\\sim 10^{15}-10^{16}$ G are plausible sources of cosmological $\\gamma$-ray bursts. In such winds, there are at least three regions where extremely powerful X-ray and $\\gamma$-ray emission may be generated. The first radiating region is the wind photosphere that is at a distance of $\\sim 10^9$ cm from the compact object. The second radiating region is at a distance of $\\sim 10^{13}-10^{14}$ cm. In this region, the striped component of the wind field is transformed into large-amplitude electromagnetic waves. The third radiating region is at a distance of $\\sim 10^{16}-10^{17}$ cm, where deceleration of the wind due to its interaction with an ambient medium becomes important. Radiation from all these regions is considered.

CERN Document Server

This essay aims to summarize the main physical features arising from a new supersymmetric theory of gravitation. Based on preliminary discussions about classical field theory, cosmology, algebra and group theory, and taking formal results and theoretical considerations in comparison with several contributions from great authors, present work deals with gravity inside the limits of a meta-field theory, that is, a non-quantized but consistent representation of supergravity, the supersymmetry between gravitons and gravitinos. The introduction of meta-fields furnishes an independent framework for the study of gravity despite of constraints of quantization, treating the supersymmetric partners as deterministic actors of gravitation and not simply probabilistic entities. I explain my belief that gravitational field, by its own nature, is not quantizable in the same foot as the other fields, what does not means that we can not understand gravity by similar formal veins. ...

CERN Document Server

We review and extend in several directions recent results on the asymptotic safety approach to quantum gravity. The central issue in this approach is the search of a Fixed Point having suitable properties, and the tool that is used is a type of Wilsonian renormalization group equation. We begin by discussing various cutoff schemes, i.e. ways of implementing the Wilsonian cutoff procedure. We compare the beta functions of the gravitational couplings obtained with different schemes, studying first the contribution of matter fields and then the so-called Einstein-Hilbert truncation, where only the cosmological constant and Newton's constant are retained. In this context we make connection with old results, in particular we reproduce the results of the epsilon expansion and the perturbative one loop divergences. We then apply the Renormalization Group to higher derivative gravity. In the case of a general action quadratic in curvature we recover, within certain ...

International Nuclear Information System (INIS)

In this letter we discuss the connection between so-called homoclinic chaos and the violation of energy conditions in locally rotationally symmetric Bianchi type IX models, where the matter is assumed to be nontilted dust and a positive cosmological constant. We show that homoclinic chaos in these models is an artifact of unphysical assumptions: it requires that there exist solutions with positive matter energy density #rho#>0 that evolve through the singularity and beyond as solutions with negative matter energy density #rho#<0. Homoclinic chaos is absent when it is assumed that the dust particles always retain their positive mass. In addition, we discuss more general models: for solutions that are not locally rotationally symmetric we demonstrate that the construction of extensions through the singularity, which is required for homoclinic chaos, is not possible in general.

CERN Document Server

Disorder on the string theory landscape may significantly affect dynamics of eternal inflation leading to the possibility for some vacua on the landscape to become dynamically preferable over others. We systematically study effects of a generic disorder on the landscape starting by identifying a sector with built-in disorder -- a set of de Sitter vacua corresponding to compactifications of the Type IIB string theory on Calabi-Yau manifolds with a number of warped Klebanov-Strassler throats attached randomly to the bulk part of the Calabi-Yau. Further, we derive continuum limit of the vacuum dynamics equations on the landscape. Using methods of dynamical renormalization group we determine the late time behavior of the probability distribution for an observer to measure a given value of the cosmological constant. We find the diffusion of the probability distribution to significantly slow down in sectors of the landscape where the number of nearest neighboring vacua ...

Energy Technology Data Exchange (ETDEWEB)

The relativistic time dilation is reviewed in a cosmological context. We show that a clock or twin paradox does not arise if cosmic time is properly taken into account. The receding galaxy background provides a unique frame of reference, and the proper times of geodesic as well as accelerated observers can be linked to the universal cosmic time parameter. This suggests to compare the proper time differentials of the respective observers by determining their state of motion in the galaxy grid. In this way, each observer can figure out whether his proper time is dilated or contracted relative to any other. In particular one can come to unambiguous conclusions on the aging of uniformly moving observers, without reference to asymmetries in measurement procedures or accelerations they may have undergone.

CERN Document Server

The central engine of Gamma Ray Bursts is hidden from direct probing with photons mainly due to the high densities involved. Inferences on their properties are thus made from their cosmological setting, energetics, low-energy counterparts and variability. If GRBs are powered by hypercritical accretion onto compact objects, on small spatial scales the flow will exhibit fluctuations, which could in principle be reflected in the power output of the central engine and ultimately in the high energy prompt emission. Here we address this issue by characterizing the variability in neutrino cooled accretion flows through local shearing box simulations with magnetic fields, and then convolving them on a global scale with large scale dynamical simulations of accretion disks. The resulting signature is characteristic, and sensitive to the details of the cooling mechanism, providing in principle a discriminant for GRB central engine properties.

CERN Document Server

A fully consistent linear perturbation theory for cosmology is derived in the presence of quantum corrections as they are suggested by properties of inverse volume operators in loop quantum gravity. The underlying constraints present a consistent deformation of the classical system, which shows that the discreteness in loop quantum gravity can be implemented in effective equations without spoiling space-time covariance. Nevertheless, non-trivial quantum corrections do arise in the constraint algebra. Since correction terms must appear in tightly controlled forms to avoid anomalies, detailed insights for the correct implementation of constraint operators can be gained. The procedures of this article thus provide a clear link between fundamental quantum gravity and phenomenology.

Energy Technology Data Exchange (ETDEWEB)

The palladium(II) and platinum(II)complexes(where, (M(L){sub 2}X{sub 2}), M=Pd(II), Pt(II); L=isoxazole (isox), 3, 5-dimethylisoxazole(3, 5-diMeisox), 3-methyl, 5-phenylisoxazole(3-Me, 5-Ph-isox), and 4-amino-3, 5-di-methylisoxazole (4-ADI); X=Cl, Br) with isoxazole and its derivatives were investigated on antitumor activity by MM2 and EHMO calculation. Because for all the complexes the {sigma}MO energy level (E{sub {sigma}}{sub (M-X)} between d{sub x}{sup 2}{sub -y}{sup 2} orbital of central metal and p{sub x} orbital of halogen atom is less than {sigma}MO energy level E{sub {sigma}}{sub (M-N)} between d{sub x}{sup 2}{sub -y}{sup 2} orbital of central metal and p{sub x} orbital of N atom, without exception. And judging, from the lower E{sub {sigma}}{sub (M-X)} value in trans, the bonding strength was found to be weaker in trans isomer than in cis. For the Pd(II) and Pt(II) complexes which have planar ligands, it was shown that for all the complexes dissociation of X-atom in the Pd(II) ...

Science.gov (United States)

Eight phospholipases A2 (PLAs) and four three-finger-toxins (3FTx) from the pooled venom of Bungarus fasciatus (Bf) were previously studied and sequenced, but their expression pattern in individual Bf venom and possible geographic variations remained to be investigated. We herein analyze the individual venom of two Bf specimens from Kolkata (designated as KBf) to address this question. Seven PLAs and five 3FTx were purified from the KBf venoms, and respective cDNAs were cloned from venom glands of one of the snakes. Comparison of their mass and N-terminal sequence revealed that all the PLAs were conserved in both KBf venoms, but that two of their 3FTx isoforms were variable. When comparing the sequences of these KBf-PLAs with those published, only one was found to be identical to that of Bf Vb-2, and the other five were 94-98% identical to those of Bf II, III, Va, VI and XI-2, respectively. Notably, the most abundant PLA isoforms of Bf and KBf venoms contain Pro31 substitution. They ...

International Nuclear Information System (INIS)

Acanthamoeba castellanii myosins IA and IB demonstrate the catalytic properties of a myosin and can support analogues of contractile and motile activity in vitro, but their single, low molecular weight heavy chains, roughly globular shapes, and inabilities to self-assemble into filaments make them structurally atypical myosins. The authors present the complete amino acid sequence of the 128-kDa myosin IB heavy chain, which they deduced from the nucleotide sequence of the gene and which reveals that the polypeptide is a fusion of myosin-like and non-myosin-like sequences. Specifically, the amino-terminal #approx# 76 kDa of amino acid sequence is highly similar to the globular head sequences of conventional myosins. By contrast, the remaining #approx# 51 kDa of sequence shows no similarity to any portion of conventional myosin sequences, contains regions that are rich in glycine, proline, and alanine residues, and lacks the distinctive sequence characteristics of an ...

International Nuclear Information System (INIS)

We evaluate the neutrino fluxes to be expected from neutralino lightest supersymmetric particle (LSP) annihilations inside the Sun, within the minimal supersymmetric extension of the standard model with supersymmetry-breaking scalar and gaugino masses constrained to be universal at the grand unified theory scale [the constrained minimal supersymmetric standard model (CMSSM)]. We find that there are large regions of typical CMSSM (m_1_/_2,m_0) planes where the LSP density inside the Sun is not in equilibrium, so that the annihilation rate may be far below the capture rate. We show that neutrino fluxes are dependent on the solar model at the 20% level, and adopt the AGSS09 model of Serenelli et al. for our detailed studies. We find that there are large regions of the CMSSM (m_1_/_2,m_0) planes where the capture rate is not dominated by spin-dependent LSP-proton scattering, e.g., at large m_1_/_2 along the CMSSM coannihilation strip. We calculate neutrino fluxes above various threshold ...

International Nuclear Information System (INIS)

The stability properties of a class of spacetimes with quasiregular singularities is discussed. Quasiregular singularities are the end points of incomplete, inextendible geodesics at which the Riemann tensor and its derivatives remain at least bounded in all parallel-propagated orthonormal (PPON) frames; observers approaching such a singularity would find that their world lines come to an end in a finite proper time. The Taub-NUT (Newman-Unti-Tamburino)-type cosmologies investigated are R"1 x T"3 and R"3 x S"1 flat Kasner spacetimes, the two-parameter family of spatially homogeneous but anisotropic Bianchi type-IX Taub-NUT spacetimes, and an infinite-dimensional family of Einstein-Rosen-Gowdy spacetimes studied by Moncrief. The behavior of matter near the quasiregular singularity in each of these spacetimes is explored through an examination of the behavior of the stress-energy tensors and scalars for conformally coupled and minimally coupled, massive and massless ...

Energy Technology Data Exchange (ETDEWEB)

An extensive study of the effects of correlations on both charged and neutral current weak interaction rates in dense matter is performed. Both strong and electromagnetic correlations are considered. The propagation of particle-hole interactions in the medium plays an important role in determining the neutrino mean free paths. The effects due to Pauli blocking and density, spin, and isospin correlations in the medium significantly reduce the neutrino cross sections. As a result of the lack of experimental information at high density, these correlations are necessarily model dependent. For example, spin correlations in nonrelativistic models are found to lead to larger suppressions of neutrino cross sections compared to those of relativistic models. This is due to the tendency of the nonrelativistic models to develop spin instabilities. Notwithstanding the above caveats, and the differences between nonrelativistic and relativistic approaches such as the spin- and isospin-dependent ...

International Nuclear Information System (INIS)

We investigate the possibility of kaon condensation in the dense interior of neutron stars through the s-wave interaction of kaons with nucleons. We include nucleon-nucleon interactions by using simple parametrizations of realistic forces, and include electrons and muons in #beta#-equilibrium. The equation of state above the condensate threshold is derived in the mean field approximation. The conditions under which kaon condensed cores undergo a transition to quark matter containing strange quarks are also established.The critical density for kaon condensation lies in the range (2.3-5.0)#rho#_0, where #rho#_0=0.16 fm"-"3 is the equilibrium density of nuclear matter. The critical density depends largely on the value of the strangeness content of the proton, the size of which is controversial. For too large a value of the strangeness content, matter with a kaon condensate is not sufficiently stiff to support the lower limit of 1.44 M_o_e_d_o_t for a neutron star. Kaon condensation ...

DEFF Research Database (Denmark)

Abstract This paper tries to investigate the problem of memory through one of its most intriguing patterns - chiasmus - reflected in old poetry, sacred texts, philosophy and theology, visual arts, as well as biology. It aims to search for some provisory explanation of why man was able once to acquire such excellence in memorizing internally thousands of lines of poetry, whereas now memory is expelled outside the human body and mind in a mere digital file. Contrasting the so-called "wish-dream for immortality" of the contemporary post-human body, this paper takes another path and looks into some old cosmologies and visions in which chiasmus constantly emerged as an enduring cultural paradigm with ontological relevance. Spanning from Plato to Christian theology, up to the contemporary Neo-Platonism of archetypal psychology, this paper hopes to put forth, if not a theory, at least a vision about man and cosmos, cosmos and man, a chiastic epiphany in which the body and ...

CERN Document Server

Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy ...

CERN Document Server

Towards the end of the 19th century, Kelvin pronounced as the "clouds of physics" 1) the failure of the Michelson-Morely experiment to detect an ether wind, 2) the violation of the classical mechanical equipartition theorem in statistical thermodynamics. And he believed that the removal of these clouds would bring physics to an end. But as we know, the removal of these clouds led to the two great breakthoughts of modern physics: 1) The theory of relativity, and 2) to quantum mechanics. Towards the end of the 20th century more clouds of physics became apparent. They are 1) the riddle of quantum gravity, 2) the superluminal quantum correlations, 3) the small cosmological constant. Furthermore, there is the riddle of dark energy making up 70% of the physical universe, the non-baryonic cold dark matter making up 26% and the very small initial entropy of the universe. An attempt is made to explain the importance of these clouds for the future of physics. Conjectures for ...

International Nuclear Information System (INIS)

Seeing convolved two-dimensional de Vaucouleurs profiles have been fitted to digital images of the brightest elliptical galaxies in two nearby groups of galaxies and three clusters of galaxies with redshifts in the range 0.06 to 0.15. The digital images were created by scanning electronographic plates obtained by the use of several versions of the RGO electronographic camera. The linear relation between effective surface brightness #mu#/sub e/ and the logarithm of the effective radius r/sub e/, first discovered by Kormendy to be valid for nearby elliptical galaxies, is found to be equally valid for the largest and brightest galaxies in rich clusters of galaxies. The apparent universal nature of that relation indicates that the same type of processes might have been involved during the formation of all ellipticals from cD galaxies in clusters to fainter ellipticals in small groups. It is suggested that the (I/sub e/,r/sub e/) relation is not changed by the expected dynamical evolution ...

CERN Document Server

Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionisation history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio obsevations. This leakage leads to a portion of the complex linear polarisation signal finding its way into Stokes I, and inhibits the detection of the non-polarised cosmological signal from the epoch of reionisation. In this work, we show that rotation measure synthesis can be used to recover the signature of cosmic hydrogen reionisation in the presence of contamination by polarised foregrounds. To achieve this, we apply the rotation measure synthesis technique to the Stokes I ...

CERN Document Server

Primordial black holes are unique probes of cosmology, general relativity, quantum gravity and non standard particle physics. They can be considered as the ultimate particle accelerator in their last (explosive) moments since they are supposed to reach, very briefly, the Planck temperature. Upper limits on the primordial black hole number density of mass $M_{\\star} = 5 10^{14}$ g, the Hawking mass (born in the big-bang terminating their life presently), is determined comparing their predicted cumulative $\\gamma$-ray emission, galaxy-wise, to the one observed by the EGRET satellite, once corrected for non thermal $\\gamma$-ray background emission induced by cosmic ray protons and electrons interacting with light and matter in the Milky Way. A model with free gas emissivities is used to map the Galaxy in the 100 MeV photon range, where the peak of the primordial black hole emission is expected. The best gas emissivities and additional model parameters are obtained ...

Energy Technology Data Exchange (ETDEWEB)

We present new theoretical predictions for the galaxy three-point correlation function (3PCF) using high-resolution dissipationless cosmological simulations of a flat {Lambda}CDM Universe which resolve galaxy-size halos and subhalos. We create realistic mock galaxy catalogs by assigning luminosities and colors to dark matter halos and subhalos, and we measure the reduced 3PCF as a function of luminosity and color in both real and redshift space. As galaxy luminosity and color are varied, we find small differences in the amplitude and shape dependence of the reduced 3PCF, at a level qualitatively consistent with recent measurements from the SDSS and 2dFGRS. We confirm that discrepancies between previous 3PCF measurements can be explained in part by differences in binning choices. We explore the degree to which a simple local bias model can fit the simulated 3PCF. The agreement between the model predictions and galaxy 3PCF measurements lends further credence to the ...

International Nuclear Information System (INIS)

The dynamics of a general Bianchi type-IX model with three scale factors is examined. The matter content of the model is assumed to be comoving dust plus a positive cosmological constant. The model presents a critical point of saddle-center-center type in the finite region of phase space. This critical point engenders in the phase space dynamics the topology of stable and unstable four dimensional tubes RxS"3, where R is a saddle direction and S"3 is the manifold of unstable periodic orbits in the center-center sector. A general characteristic of the dynamical flow is an oscillatory mode about orbits of an invariant plane of the dynamics which contains the critical point and a Friedmann-Robertson-Walker (FRW) singularity. We show that a pair of tubes (one stable, one unstable) emerging from the neighborhood of the critical point towards the FRW singularity have homoclinic transversal crossings. The homoclinic intersection manifold has topology RxS"2 and is ...

Energy Technology Data Exchange (ETDEWEB)

Particle physics is driven by five great topics. Neutrino oscillations and masses are now at the fore. The standard model with extensions to supersymmetry and a Higgs to generate mass explains much of the field. The origins of CP violation are not understood. The possibility of extra dimensions has raised tantalizing new questions. A fifth topic lurking in the background is the possibility of something totally different. Many of the questions raised by these topics require powerful new accelerators. It is not an overstatement to say that for some of the issues, the accelerator is almost the experiment. Indeed some of the questions require machines beyond our present capability. As this volume attests, there are parts of the particle physics program that have been significantly advanced without the use of accelerators such as the subject of neutrino oscillations and many aspects of the particle-cosmology interface. At this stage in the development of physics, both ...

CERN Document Server

If high-redshift QSOs are ejected from the nuclei of low-redshift galaxies, as some have claimed, a large portion of their redshift must be intrinsic (non-Doppler). If these intrinsic components have preferred values, redshifts will tend to cluster around these preferred values and produce peaks in the redshift distribution. Doppler ejection and Hubble flow components will broaden each peak. Because ejection velocities are randomly directed and Hubble flow components are always positive, in this model all peaks are expected to show an asymmetry, extending further out in the red wing. If peaks are present showing this predicted asymmetry, it can lead directly to an estimate of quasar distances. Using two quasar samples, one with high redshifts and one with low, it is shown here that not only do all peaks in these two redshift distributions occur at previously predicted preferred values, they also all show the predicted extra extension in the red wing. For the low and high redshift ...

CERN Document Server

We conjecture that all CP violations (both Dirac and Majorana types) arise from a common origin in neutrino seesaw. With this conceptually attractive and simple conjecture, we deduce that mu-tau breaking shares the common origin with all CP violations. We study the common origin of mu-tau and CP breaking in the Dirac mass matrix of seesaw Lagrangian (with right-handed neutrinos being mu-tau blind), which uniquely leads to inverted mass-ordering of light neutrinos. We then predict different correlations between the two small mu-tau breaking observables theta_{13} - 0 and theta_{23} -45, which can be tested against our previous normal mass-ordering scheme by the on-going oscillation experiments. We also analyze the correlations of theta_{13} with Jarlskog invariant and neutrinoless double-beta-decay observable. From the common origin of CP and mu-tau breaking in the neutrino seesaw, we establish a direct link between the low energy CP violations and the cosmological ...

CERN Document Server

If gamma-ray bursts originate in galaxies at cosmological distances, the host galaxy should be detected if a burst error box is searched deep enough; are the host galaxies present? We present and implement a statistical methodology which evaluates whether the observed galaxy detections in a burst's error box are consistent with the presence of the host galaxy, or whether all the detections can be attributed to unrelated background galaxies. This methodology requires the model-dependent distribution of host galaxy fluxes. While our methodology was derived for galaxies in burst error boxes, it can be applied to other candidate host objects (e.g., active galaxies) and to other types of error boxes. As examples, we apply this methodology to two published studies of burst error boxes. We find that the nine error boxes observed by Larson and McLean (1997) are too large to discriminate between the presence or absence of host galaxies, while the absence of bright galaxies ...

Energy Technology Data Exchange (ETDEWEB)

The authors analyze the consequences of models of structure formation for higher-order (n-point) galaxy correlation functions in the mildly non-linear regime. Several variations of the standard {Omega} = 1 cold dark matter model with scale-invariant primordial perturbations have recently been introduced to obtain more power on large scales, R{sub p} {approximately}20 h{sup {minus}1} Mpc, e.g., low-matter-density (non-zero cosmological constant) models, {open_quote}tilted{close_quote} primordial spectra, and scenarios with a mixture of cold and hot dark matter. They also include models with an effective scale-dependent bias, such as the cooperative galaxy formation scenario of Bower, et al. The authors show that higher-order (n-point) galaxy correlation functions can provide a useful test of such models and can discriminate between models with true large-scale power in the density field and those where the galaxy power arises from scale-dependent bias: a bias with ...

Energy Technology Data Exchange (ETDEWEB)

This Report of activity displays the work developed at Centre d`Etude Nucleaires de Bordeaux-Gradignan (CENBG) in the period 1995-1996. A number of 68 short progress notes are presented in the fields of Cosmic particles (3), Nuclear Astrophysics (4), High Spins-Large Deformations (8), Basic Interactions (9), Exotic Nuclei (10), Hybrid Systems (4), Theoretical Physics (28), Cellular Microanalysis by means of Nuclear Probes (3) and Technical Development (3). The main problems attacked at CENBG, established as orientations by scientific board of IN2P3 (CENBG is a UMR of Bordeaux-1 Univ. and CNRS-IN2P3) are the following: the research of Majorana/Dirac nature of neutrino (in the framework of NEMO Experiment) in relation with the problem of origin of mass in the Universe and the cosmological puzzle of dark matter, the investigation of the origin of high energy (20 to 200 GeV) cosmic radiation (in the framework of CELESTE Experiment), the study of extreme issues in ...

International Nuclear Information System (INIS)

The main goals of nuclear astrophysics have been to probe the interiors of stars, stellar explosions, the early moments of cosmic expansion, and the formation and evolution of galaxies and cosmic structure by measurement and application of the relevant nuclear physics. The approach to these goals have generally been from three directions: 1) Careful measurements of the relevant nuclear reactions; 2) Detailed computer models of the relevant astrophysical environments; and 3) Observations of the relevant terrestrial and extra-terrestrial atomic and isotopic abundances. These approaches provide not only insight into the formation and evolution of the elements, but are also pillars upon which a variety of cosmological models as well as models for physics beyond the standard model of particle physics can stand or fall. At present there is a very exciting frontier on all three of these approaches. The development and applications of radioactive-ion-beam and ...

International Nuclear Information System (INIS)

An IAEA databank lists a number of reported cases of illicitly trafficked nuclear or other radioactive materials. Apart from the traditional concern with nuclear proliferation, the post September 11th public is now wary of a possible attack by terrorists with a nuclear or radiation dispersion device (RDD). Until now, the seized quantities have not been sufficient to manufacture a nuclear explosive device, but they might be enough to construct an RDD. Recognizing the latent global challenge to public health and safety, the G8 States (Japan, USA, Germany, France, UK, Italy, Canada, and Russia) have called for 'joint international efforts to identify and suppress illicit supply' of, and demand for, nuclear material and to deter potential traffickers. One measure gaining in significance is to identify seized material and trace it back to its origin the objective of an emerging science known as nuclear forensics. Repeatedly nuclear or other radioactive material of unknown origin are ...