EUCLID mission. EUCLID is a mission concept for studying the Dark Energy that is hypothesized to account for the accelerating cosmic expansion. ...

If expanding and contracting regions coexist in the universe, the speed of the cosmic volume expansion can be accelerated. We construct simple inhomogeneous dust-filled universe models in which the speed of the cosmic volume expansion is accelerated for finite periods. ...

Cosmic acceleration has come to be a standard, and perhaps required, ingredient in our current understanding of the universe. In the early universe, under the name of inflation, a phase of accelerated expansion is used to solve many problems with the standard Hot Big Bang cosmology. In the late universe, ...

A possible slowing down of the cosmic expansion is investigated through a cosmographic approach. By expanding the luminosity distance to fourth order and fitting the SN Ia data from the most recent compilations (Union, Constitution and Union 2), the marginal likelihood distributions for the deceleration parameter today suggest a recent reduction of the ...

at the speed of light; the blue spheres represent an expanding patch of space. As expansion accelerates, fewer; in an expanding universe, gravity simply slows the expansion. The question then became, Is gravity strong enough the discovery of cosmic expansion, cosmologists constructed a model of ...

and contracting regions coexist in the universe, the speed of the cosmic vol- ume expansion can be accelerated. We construct simple inhomogeneous dust-#12;lled universe models in which the speed of the cosmic volume expansion The accelerating expansion ...

The cosmic expansion history tests the dynamics of the global evolution of the universe and its energy density contents, while the cosmic growth history tests the evolution of the inhomogeneous part of the energy density. Precision comparison of the two histories can distinguish the nature of the physics responsible for the ...

Using very distant supernovae as standard candles, one can trace the history of cosmic expansion and try to find out what's currently speeding it up.

The cosmic triangle is introduced as a way of representing the past, present and future status of the universe. Our current location within the cosmic triangle is determined by the answers to three questions: How much matter is in the universe? Is the expansion rate slowing down or speeding up? And, is the universe flat? A review of ...

The widely accepted model of our cosmos is that it began from a Big Bang event some 13.7 billion years ago from a single point source. From a twin universe perspective, the standard stellar model of nuclear fusion can account for the Dark Energy needed to explain the mechanism for our present-day accelerated expansion. The same theories can also be used to ...

The widely accepted model of our cosmos is that it began from a Big Bang event some 13.7 billion years ago from a single point source. From a twin universe perspective, the standard stellar model of nuclear fusion can account for the Dark Energy needed to explain the mechanism for our present-day accelerated expansion. The same theories can also be used to ...

The cosmic expansion history proceeds in broad terms from a radiation dominated epoch to matter domination to an accelerated, dark energy dominated epoch. We investigate whether intermittent periods of acceleration (from a canonical, minimally coupled scalar field) are possible in the early universe � between Big ...

It is argued that all notions associated with the origin of life should be related with the participatory anthropic principle of Wheeler and must be extended into the realm of the multiverse. Also discussed is the notion that life can only be possible in a given universe during a finite period along which such a universe expands in an accelerated fashion. We advance finally ...

Recent observational studies of distant supernovae have suggested the existence of cosmic vacuum whose energy density exceeds the total density of all the other energy components in the Universe. The vacuum produces the field of antigravity that causes the cosmological expansion to accelerate. It is this ...

If spacetime undergoes quantum fluctuations, an electromagnetic wavefront will acquire uncertainties in direction as well as phase as it propagates through spacetime. These uncertainties can show up in interferometric observations of distant quasars as a decreased fringe visibility. The Very Large Telescope and Keck interferometers may be on the verge of probing spacetime fluctuations which, we ...

... Title : On Cosmic Ray Generation By Pulsars. ... The consequences for cosmic ray acceleration by pulsars are investigated. (Author). ...

If general relativity (GR) describes the expansion of the Universe, the observed cosmic acceleration implies the existence of a "dark energy." However, while the Universe is on average homogeneous on large scales, it is inhomogeneous on smaller scales. While GR governs the dynamics of the inhomogeneous Universe, the averaged ...

Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable consequences in many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has proven very difficult to measure directly. ...

Interactions between dark matter and dark energy with a given equation of state are known to modify the cosmic dynamics. On the other hand, the strength of these interactions is subject to strong observational constraints. Here we discuss a model in which the transition from decelerated to accelerated expansion of the Universe arises ...

Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large ...

candidate provides plausible explanations for the accelerating expansion of the Universe, dark energy, both and ultra�high energy (UHE) cosmic rays, dark energy and the accelerating expansion of the cosmos and how matter particles also included dark energy, new star ignition, the spherical ...

lectures. I discuss the pos+ible consequences of forming cosmic strings .... theory of the early universe successfully predicts the Hubble expansion, the microwave background ..... V, invariant when acting on it. In the phase transition ...

The current accelerated expansion of our universe could be due to an unknown energy component (dark energy) or a modification of general relativity (modified gravity). In the literature it has been proposed that combining the probes of the cosmic expansion history and growth history can distinguish between dark ...

We study the cosmic expansion history by reconstructing the deceleration parameter q(z) from the SDSS-II type Ia supernova sample (SNIa) with two different light curve fits (MLCS2k2 and SALT-II), the baryon acoustic oscillation (BAO) distance ratio, the cosmic microwave background (CMB) shift parameter, and the lookback time-redshift ...

In an undulant universe, cosmic expansion is characterized by alternating periods of acceleration and deceleration. We examine cosmologies in which the dark-energy equation of state varies periodically with the number of e-foldings of the scale factor of the universe, and use observations to constrain the frequency of oscillation. We ...

Nov 19, 2004 ... Anomalous Cosmic Ray Hydrogen. Cosmic rays can be accelerated in different ways. Some cosmic rays (called anomalous cosmic rays or ...

We elaborate on the proposal that the observed acceleration of the Universe is the result of the backreaction of cosmological perturbations, rather than the effect of a negative-pressure dark energy fluid or a modification of general relativity. Through the effective Friedmann equations describing an inhomogeneous Universe after smoothing, we demonstrate that ...

Using new cross section measurements of Ni into Co, data on the Co/Ni ratio in cosmic rays from the HEAO C spacecraft have been reinterpreted in terms of the time between nucleosynthesis and the acceleration of cosmic rays, delta t. The observed Co/Ni ratio is now consistent with interstellar fragmentation only, leading to a small or ...

Cosmic parallax is the change of angular separation between a pair of sources at cosmological distances induced by an anisotropic expansion. An accurate astrometric experiment like Gaia could observe or put constraints on cosmic parallax. Examples of anisotropic cosmological models are Lemaitre-Tolman-Bondi void models for off-center ...

to the determination of the expansion history of the universe is discussed. Work by two separate research teams, these proceedings) to measure the expansion history of the universe. Using independent methods of correcting Type Ia. #12; FIGURE 1. Discoveries of spectroscopically con#12;rmed Type Ia supernovae at cosmological dis- tances up

It is the common consensus that the expansion of a universe always slows down if the gravity provided by the energy sources therein is attractive and accordingly one needs to invoke dark energy as a source of anti-gravity for understanding the cosmic acceleration. To examine this point we find counterexamples for a spherically ...

Consistency relations between growth of structure and expansion history observables exist for any physical explanation of cosmic acceleration. We perform MCMC likelihood exploration of these relations, using future SNAP supernova and Planck CMB data to derive the expected variation in the growth and distance functions and the Hubble ...

Increasing evidence suggests that most of the energy density of the universe consists of a dark energy component with negative pressure that causes the cosmic expansion to accelerate. We address why this component comes to dominate the universe only recently. We present a class of theories based on an evolving scalar field where the ...

The study investigates the acceleration of cosmic rays by superrelativistic plasma waves. The pulsar

We examine the variation of the fine structure constant in the context of a two-field quintessence model. We find that, for solutions that lead to a transient late period of accelerated expansion, it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of {alpha} from the Oklo reactor, meteorite analysis, ...

Cosmology is undergoing a revolution. With recent precise measurements of the cosmic microwave background radiation, large galaxy redshift surveys, better measurements of the expansion rate of the Universe and a host of other astrophysical observations, there is now a standard, highly constrained cosmological model. It is not a cosmology that was ...

We recently introduced the concept of ''k-essence'' as a dynamical solution for explaining naturally why the universe has entered an epoch of accelerated expansion at a late stage of its evolution. The solution avoids fine-tuning of parameters and anthropic arguments. Instead, k-essence is based on the idea of a ...

The cosmographic expansion history of the universe is investigated by using the 557 type Ia supernovae from the Union2 Compilation set along with the current estimates involving the product of the CMB acoustic scale ?A and the BAO peak at two different redshifts. Using a well-behaved parameterization for the deceleration parameter, q(z) = q0 + q1z/(1 + z), we estimate the ...

A timely combination of new theoretical ideas and observational discoveries has brought about significant advances in our understanding of cosmic evolution. Computer simulations have played a key role in these developments by providing the means to interpret astronomical data in the context of physical and cosmological theory. In the current paradigm, our Universe has a flat ...

The source of energy for cosmic-ray acceleration appears to be shock waves driven by supernova (SNe) ejecta. An obvious implication of this premise is that cosmic rays are accelerated where supernovae are found. The great majority (80 - 90%) of SNe (SNII & SNIb\\c) are formed by the core collapse of young (3 to ...

Galactic cosmic rays (CRs) are widely believed to be accelerated by shock waves associated with the expansion of supernova ejecta into the interstellar medium. A key issue in this long-standing conjecture is a theoretical prediction that the interstellar magnetic field can be substantially amplified at the shock of a young supernova ...

A wind-type solution is obtained in an axisymmetric spacetime in the case when matter has angular momentum. An application of the solution in understanding the acceleration of matter in radio jets as it flows along the funnel of a thick accretion disk is suggested. It is observed that the location of the critical point depends strongly upon the angular momentum of the wind. ...

We present constraints on the cosmic growth history with recent cosmological data, allowing for deviations from {Lambda}CDM as might arise if cosmic acceleration is due to modifications to general relativity or inhomogeneous dark energy. We combine measures of the cosmic expansion history, from ...

We give detailed proofs of several new no-go theorems for constructing flat four-dimensional accelerating universes from warped dimensional reduction. These new theorems improve upon previous ones by weakening the energy conditions, by including time-dependent compactifications, and by treating accelerated expansion that is not ...

General relativistic corrections to the expansion rate of the Universe arise when the Einstein equations are averaged over a spatial volume in a locally inhomogeneous cosmology. It has been suggested that they may contribute to the observed cosmic acceleration. In this paper, we propose a new scheme that utilizes numerical simulations ...

Modified gravity provides a possible explanation for the currently observed cosmic acceleration. In this paper, we study general classes of modified gravity models. The Einstein-Hilbert action is modified by using general functions of the Ricci and the Gauss-Bonnet scalars, both in the metric and in the Palatini formalisms. We do not use an explicit form ...

... RESEARCH MANAGEMENT, ELECTRON ACCELERATORS, COSMIC RAYS, LINEAR ACCELERATORS, PARTICLE ACCELERATORS. ...

A unified treatment of mass varying dark matter coupled to cosmonlike dark energy is shown to result in effective generalized Chaplygin gas (GCG) scenarios. The mass varying mechanism is treated as a cosmon field inherent effect. Coupling dark matter with dark energy allows for reproducing the conditions for the present cosmic acceleration and for ...

A unified treatment of mass varying dark matter coupled to cosmonlike dark energy is shown to result in effective generalized Chaplygin gas (GCG) scenarios. The mass varying mechanism is treated as a cosmon field inherent effect. Coupling dark matter with dark energy allows for reproducing the conditions for the present cosmic acceleration and for ...

A spatially homogeneous and anisotropic Bianchi type-I cosmological model is obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A 113:467, 1986) when the source for energy momentum tensor is a bulk viscous fluid containing one dimensional cosmic strings. Some physical and kinematical properties of the model are discussed. It is ...

Consistency relations between growth of structure and expansion history observables exist for any physical explanation of cosmic acceleration, be it a cosmological constant, scalar field quintessence, or a general component of dark energy that is smooth relative to dark matter on small scales. The high-quality supernova sample ...

The coincidence problem of late cosmic acceleration constitutes a serious riddle with regard to our understanding of the evolution of the Universe. Here we argue that this problem may someday be solved - or better understood - by expressing the Hubble expansion rate as a function of the ratio of densities (dark matter/dark energy) and ...

In this work, a generalization of the Mazur-Mottola gravastar model is explored, by considering a matching of an interior solution governed by the dark energy equation of state, w ? p/? < -1/3, to an exterior Schwarzschild vacuum solution at a junction interface, situated near to where the event horizon is expected to form. The motivation for implementing this generalization arises from the ...

Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show that if the quintessence density is at least 1% of the critical density at the surface of last scattering the cosmic microwave background ...

We find a solution for exponential inflation in a Brans-Dicke generalized model, where the coupling �constant� is variable. While in General Relativity the equation of state is p=- ?, here we find p= ? ?, where ?<-2/3. The negativity of cosmic pressure implies acceleration of the expansion, even with ?<0.

Is Dark Energy justified as an alternative to the cosmological constant LAMBDA in order to explain the acceleration of the cosmic expansion? It turns out that a straightforward dimensional analysis of Einstein equation provides us with clear evidences that the geometrical nature of LAMBDA is the only viable source to this phenomenon, ...

A large number of observations suggest that our universe entered at low redshifts a stage with accelerated expansion rate. Many models, Dark Energy (DE) models, able to explain this departure from conventional cosmology have been proposed. These models are conceptually very different, either introducing some new component with sufficiently negative ...

################## arXiv:astro�ph/0103175 12 Mar 2001 Constraining the properties of dark energy. The presence of dark energy in the Universe is inferred directly from the accelerated expansion of the Universe, and indirectly, from measurements of cosmic microwave background (CMB) anisotropy. Dark energy contributes about

We present a short (and necessarily incomplete) review of the evidence for the accelerated expansion of the Universe. The most direct probe of acceleration relies on the detailed study of supernovae (SN) of type Ia. Assuming that these are standardizable candles and that they fairly sample a homogeneous and isotropic Universe, the ...

General relativistic corrections to the expansion rate of the universe arise when the Einstein equations are averaged over a spatial volume in a locally inhomogeneous cosmology. It has been suggested that they may contribute to the observed cosmic acceleration. In this talk, we propose a new scheme that enables us to use N-body ...

The observed accelerated cosmic expansion is problematic in that it seems to require an otherwise unobserved dark energy for its origin. A possible alternative explanation has been recently given, which attempts to account for this expansion in terms of a hypothesized matter-anti-matter repulsion. This repulsion or ...

The latest cosmological data point to a model of the universe that is self-consistent but deeply weird. It seems that most matter in our universe is non-baryonic and hidden from direct view. Meanwhile, a repulsive "dark energy" causes the expansion of the universe to proceed at an accelerating rate. Sources of current data include studies of the ...

This paper consists in analyzing an action that describes boson and fermion fields minimally coupled to the gravity and a common matter field. The self-interaction potentials of the fields are not chosen a priori but from the Noether symmetry approach. The Noether forms of the potentials allow the boson field to play the role of dark energy and matter and the fermion field to behave as standard ...

Turbulence-driven plasma accelerators produced by magnetized accretion disks around black holes are proposed as the mechanism mainly responsible for observed cosmic ray protons with ultra high energies 10{sup 19}-10{sup 21} eV. The magnetized disk produces a voltage comparable to these cosmic ray energies. Here we present a Poynting ...

Apr 16, 2010 ... Possible scenarios for the expansion (and possibly contraction) of the ... is causing the expansion of the universe to speed up (accelerate). ...

Distribution, acceleration, and energy losses of cosmic rays in the vicinity of molecular clouds are investigated. Observations indicating increased cosmic ray density inside molecular clouds are discussed. The necessary condition for cosmic ray accelerat...

Among various phenomenological ? models, a time-dependent model dot{?}� H3 is selected here to investigate the ?-CDM cosmology. The model can follow from dynamics, underlying the origin of ?. Using this model the expressions for the time-dependent equation of state parameter ? and other physical parameters are derived. It is shown that in H 3 model accelerated ...

We consider a 5-dimensional scalar-tensor theory which is a direct generalization of the original 4-dimensional Brans-Dicke theory to five dimensions. By assuming that there is a hypersurface-orthogonal spacelike Killing vector field in the underlying 5-dimensional spacetime, the theory is reduced to a 4-dimensional theory where the 4-metric is coupled with two scalar fields. The cosmological ...

We investigate cosmological consequences of a class of exponential f(R) gravity in the Palatini formalism. By using the current largest type Ia Supernova sample along with determinations of the cosmic expansion at intermediary and high-z we impose tight constraints on the model parameters. Differently from other f(R) models, we find solutions of transient ...

I briefly discuss the challenges presented by attempting to modify general relativity to obtain an explanation for the observed accelerated expansion of the universe. Foremost among these are the questions of theoretical consistency � the avoidance of ghosts in particular � and the constraints imposed by precision local tests of gravity within the ...

Numerous cosmic ray propagation and acceleration problems require knowledge of the propagation speed

... SOLAR COSMIC RAYS, ACCELERATION, TRAPPING(CHARGED PARTICLES), PROTONS, MAGNETIC MIRRORS, SOLAR FLARES, POLAR ...

Wave stability of a two-fluid hydrodynamical model describing the acceleration of cosmic rays by the

Electromagnetic and particle energy fluxes are equipartitioned in a superrelativistic plasma wave. The consequences for cosmic ray acceleration by pulsars are investigated. (Author)

A two-fluid hydrodynamical model governing the transport of cosmic rays in a relativistically moving

... in high-energy nuclear interactions, first using cosmic rays as the source of such particles and more recently using the accelerator at CERN, Geneva ...

In this paper we assess possible roles of stochastic acceleration by random electric field and plasma motion in the production and transport of energetic particles in the heliosphere. Stochastic acceleration can occur in the presence of multiple small-scale magnetohydrodynamic waves propagating in different directions. Usually, this type of stochastic ...

In recent years, the old problem of cosmic-ray acceleration and propagation has become alive again, with the discovery of the diffusive shock acceleration mechanism, and with the first measurements of the cosmic-ray antiproton flux, which appears to be hi...

The transformation of the energy of an accelerating, expanding universe into internal energy of cosmic objects is discussed. The well known fact that Hubble expansion is observed on scale lengths two or more orders of magnitude smaller than the �cells of homogeneity� is taken into account, along with observational data indicating ...

In dynamic spacetimes in which asymmetric gravitational collapse/expansion is taking place, the timelike geodesic equation appears to exhibit an interesting property: Relative to the collapsing configuration, free test particles undergo gravitational �acceleration� and form a double-jet configuration parallel to the axis of collapse. We illustrate this ...

Using torsion two-form we present a new Lorentz gauge invariant U(1) topological field theory in Riemann Cartan space time manifold U4. By virtue of the decomposition theory of U(1) gauge potential and the phi-mapping topological current theory, it is proven that the U(1) complex scalar field phi(x) can be looked upon as the order parameter field in our Universe, and a set of zero points of phi(x) ...

cosmic-ray acceleration sites and will lead to the study of the energy spectrum of individual sources. This, combined with the study of the attenuation of cosmic ...

Recent evidence suggests that most of the energy in the universe consists of some form of dark energy that is gravitationally self-repulsive and that is causing the expansion rate of the universe to accelerate. We review the evidence, including recent measurements of the cosmic microwave background by the DASI, BOOMerang and MAXIMA ...

One possible explanation for the origin of the dark energy which contributes the apparent cosmic acceleration involves general relativistic corrections to the Friedmann expansion for a locally inhomogeneous cosmology. The general solution of this scenario has not been established except for cases with special symmetry like the ...

In this work we study the cosmology of the general f(T) gravity theory. We express the modified Einstein equations using covariant quantities, and derive the gauge-invariant perturbation equations in covariant form. We consider a specific choice of f(T), designed to explain the observed late-time accelerating cosmic expansion without ...

Language: English ...

... Accession Number : AD0057522. Title : Cosmic Rays, Nuclear Physics, and Linear Accelerator Studies. Descriptive Note : Annual rept. no. 4,. ...

... Accession Number : AD0024291. Title : Cosmic Rays, Nuclear Physics, and Linear Accelerator Studies. Descriptive Note : Annual rept. no. 3. ...

An assessment is made of the role of interstellar acceleration that would occur in the diffusion model of cosmic-ray propagation through scattering by weak irregularities in the galactic magnetic field.

The origin of cosmic rays and applicable laboratory experiments are discussed. Some of the problems of shock acceleration for the production of cosmic rays are discussed in the context of astrophysical conditions. These are: The presumed unique explanatio...

The acceleration of the cosmic expansion may be due to a new component of physical energy density or a modification of physics itself. Mapping the expansion of cosmic scales and the growth of large scale structure in tandem can provide insights to distinguish between the two origins. Using ...

The acceleration of the cosmic expansion may be due to a new component of physical energy density or a modification of physics itself. Mapping the expansion of cosmic scales and the growth of large scale structure in tandem can provide insights to distinguish between the two origins. Using ...

Observational evidence increasingly supports the scenario where cosmic rays are accelerated at supernova remnant (SNR) shocks. Both thermal and non-thermal emission from these objects, in a wide range of wavelengths, indicate the presence of extremely energetic particles in SNRs, and the development of analytical and semi-analytical models of SNR evolution ...

We investigate the course of cosmic expansion in its recent past using the Constitution SN Ia sample, along with baryon acoustic oscillations (BAO) and cosmic microwave background (CMB) data. Allowing the equation of state of dark energy (DE) to vary, we find that a coasting model of the universe (q{sub 0}=0) fits the data about as ...

We establish a new self-consistent model in order to explain from a unified viewpoint two key features of the cosmological evolution: the inflation in the early Universe and the late-time accelerated expansion. The key element of this new model is the Archimedean-type coupling of the dark matter with dark energy, which form the so-called ...

In order to make the increase of Astronomical Unit consistent with observations of the Earth's orbital period variation, an increase of the Solar dark matter as 10-12/yr is needed. This implies that dark matter has an increase ratio, and therefore supports Dirac's multiplicative matter creation, and provides another explanation to the accelerating ...

Since the early days of the theory of electromagnetism and of gravity the idea of space, then space-time, as a sort of physical continuum hovered the scientific community. Actually general relativity shows the strong similarity that exists between the geometrical properties of space-time and the ones of a strained elastic continuum. The bridge between geometry and the elastic potential, as well in ...

A web of interlocking observations has established that the expansion of the Universe is speeding up and not slowing, revealing the presence of some form of repulsive gravity. Within the context of general relativity the cause of cosmic acceleration is a highly elastic ( p�-?), very smooth form of energy called �dark energy� ...

The metric f(R) theories of gravity are generalized to five-dimensional spacetimes. By assuming a hypersurface-orthogonal Killing vector field representing the compact fifth dimension, the five-dimensional theories are reduced to their four-dimensional formalism. Then we study the cosmology of a special class of f(R)={alpha}R{sup m} models in a spatially flat Friedmann-Robertson-Walker spacetime. ...

We consider Double Quintessence models for which the Dark Energy sector consists of two coupled scalar fields. We study, in particular, the possibility to have a transient acceleration in these models. In both Double Quintessence models studied here, it is shown that, if acceleration occurs, it is necessarily transient. We consider also the possibility to ...

Massive redshift surveys of galaxies beyond the local Universe (i.e.z>0.3) provide an exhaustive probe of the observed acceleration of cosmic expansion. While they have the ability to measure the expansion history H(z) through Baryonic Acoustic Oscillations in the galaxy power spectrum, they can at the same time ...

Observations of distant supernovae indicate that the Universe is now in a phase of accelerated expansion the physical cause of which is a mystery. Formally, this requires the inclusion of a term acting as a negative pressure in the equations of cosmic expansion, accounting for about 75 per cent of the total energy ...

... THE NATURE AND INTERACTIONS OF HIGH ... Descriptors : (*PARTICLES, ENERGY), COSMIC RAYS, DETECTORS, PARTICLE ACCELERATORS ...

... Descriptors : *NUCLEAR PHYSICS, *PARTICLES, ACCELERATION, BEVATRONS, COSMIC RAYS, DEGRADATION, ENERGY, THEORY. ...

It is proposed that the acceleration of cosmic rays is distributed over their propagation through interstellar space. Thus after most nuclear fragmentation reactions in the interstellar medium, cosmic rays gain about a factor of 5 in energy. This hypothesis resolves several discrepancies in composition at different energies. The ...

Aims: The extensive observations of the supernova SN 1993J at radio wavelengths make this object a unique target for the study of particle acceleration in a supernova shock. Methods: To describe the radio synchrotron emission we use a model that couples a semianalytic description of nonlinear diffusive shock acceleration with self-similar solutions for ...

Nuclear and atomic processes shaping the composition of the cosmic radiation prior to propagation are reviewed. The role of selective ionization and rigidity-dependent effects is emphasized. The elemental and isotopic cosmic-ray source abundances are used to place empirical constraints on idealized acceleration models.

This NASA web page has multiple resources about cosmic rays. Topics: composition of the sun, acceleration, galactic cosmic rays, anomalous cosmic rays, solar energy, nuclear synthesis.

Great many experiments confirm the newly discovered and theoretically deduced plasma-redshift cross-section and the associated heating in the coronas of the Sun, stars, galaxies, and quasars. The experiments show that the intergalactic plasma has an average electron density Ne=0.0002 per cubic cm with an average per particle temperature of 2.7 million K. These densities and temperatures predict ...

Several key features of the coronal propagation of solar cosmic rays have previously been explained by a ''magnetic bottle'' model proposed by Schatten and Mullan. The major apparent difficulty with that model is that expansion of the closed bottle might have a severe cooling effect on the cosmic ...

Two problems associated with the question of whether a large number of cosmic rays produced in the early stages of expansion of a supernova bubble would be trapped in it are discussed.

Dark Energy/Cosmic Times Kick-off Meeting. Dark Energy/Cosmic Times ... Dark Energy is meant to explain observations that show that the expansion of the ...

Tool for mapping expansion history Galaxy cluster searchesGalaxy cluster searches BIMA Diabolo SuZIE FREQUENCY

A general analysis and evaluation are made of data, presented at the International Conference on Cosmic Radiation in Moscow, July 1959, on the origin of cosmic rays. Basic and new data on primary cosmic radiation, on the life-time and motion of cosmic rays, on cosmic ray sources and the ...

We propose to study the cosmic acceleration through a precise measurement of the expansion history of the universe (Hubble parameter as a function of redshift) out to redshift z=1. This measurement will result from detailed study of the evolution of the galaxy cluster population over cosmic time using (1) forefront ...

We study the evolution of matter density perturbations in Galileon cosmology where the late-time cosmic acceleration can be realized by a field kinetic energy. We obtain full perturbation equations at linear order in the presence of five covariant Lagrangians Li (i=1,?,5) satisfying the Galileon symmetry ???????+b? in the flat space-time. The equations for ...

A moderate investment of observing time with the International X-ray Observatory to study high-redshift galaxy clusters detected in future large-scale surveys, will provide cosmological measurements of fundamental importance. IXO observations, combined with lensing follow-up, will measure the perturbation growth factor from z=0-2 with an accuracy comparable to, or possibly better than, that ...

Recent experiments on large air showers indicate that cosnfic rays exist with such high energy that they canaot be confined in the galaxy and they carnot be accelerated in the galaxy by hydromagnetic processes. fumthermore, the timne scase for acceleration in extragalactic space cannot reasonably be made smaller than the ...

also leads to an accelerating expansion. If the accelerating expansion last forever the universe to be in accelerating expansion state and will do so forever in the future. It should be noted that this universe can ! \\Gamma10=21 which is considerably smaller than ...

A comprehensive solution to the cosmic conundrum is presented that also resolves key paradoxes of quantum mechanics and relativity. A simple mathematical model, the Gravity Nullification model (GNM), is proposed that integrates the missing physics of the spontaneous relativistic conversion of mass to energy into the existing physics theories, specifically a simplified general ...

In some classes of inflationary models, a violation of the null energy condition (NEC) is expected during the phase of accelerated expansion. The most striking observational effect would be a "blue" spectrum of primordial gravitational waves with a spectral index nT larger than zero. In this brief paper, we first update the current constraints on the ...

We study Lorentz-violating models of massive gravity which preserve rotations and are invariant under time-dependent shifts of the spatial coordinates. In the linear approximation the Newtonian potential in these models has an extra confining term proportional to the distance from the source. We argue that during cosmological expansion the Universe may be driven to an ...

Models with vector fields acquiring a nonvanishing vacuum expectation value along one spatial direction have been proposed to sustain a prolonged stage of anisotropic accelerated expansion. Such models have been used for realizations of early time inflation, with a possible relation to the large scale cosmic microwave background ...

On the basis of the observed facts of the cosmic-ray storm, a model of the mechanism of the cosmic-ray storm is proposed, considering the connection with other related phenomena, such as the solar and terrestrial phenomena. As a result of the investigation, it is concluded that the essential mechanism of the cosmic-ray storm ...

An overview is given in section 1, of uncertain building blocks of present-day cosmologies. Thereafter, these edited lecture notes deal with the following four special problems: (1) They advertise Wiltshire's result-making `dark energy' obsolete-that accelerated cosmic expansion may be an artefact, due to an incorrect evaluation of the ...

The accelerated expansion of the universe is interpreted as an effect of a defect in space-time treated as a four-dimensional continuum endowed with physical properties. The analogy is with texture defects in material continua, like dislocations and disclinations, described in terms of a singular displacement vector field. A Lagrangian for empty space-time ...

The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10 exp 18 eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucle...

This thesis concentrates on the acceleration and propagation of energetic particles in turbulent cosmic plasmas. The stochastic acceleration of relativistic electrons by long-wavelength weak magnetohydrodynamic turbulence is considered and a model is disc...

These papers deal with experimental and theoretical studies of cosmic rays, particularly with respect to the origin of the particles, cosmic-ray modulation in the solar system, solar particles, muons and neutrinos, high-energy particle physics, extensive air showers, and observational techniques. Topics include cosmic-ray ...

Supernova observations show that the expansion of the universe has been speeding up. This unexpected acceleration is ascribed to a dark energy that pervades space. Supernova data, combined with other observations, indicate that the universe is about 14 billion years old and is composed of about 30%matter and 70%dark energy. New observational programs can ...

Novel physics founded on a dual and commensurate space-time universe explicates the nature of dark matter and energy [see APS 2007 Spring Meeting]. Its governing principles also illuminate how the dark matter and energy become unobservable, why the dark energy still suffuses the universe while the observable energy had long faded into the cosmic microwave background, how the ...

Traditionally, inflationary models are analyzed in terms of parameters such as the scalar spectral index n{sub s} and the tensor to scalar ratio r, while dark energy models are studied in terms of the equation of state parameter w. Motivated by the fact that both deal with periods of accelerated expansion, we study the evolution of w during inflation, in ...

Traditionally, inflationary models are analyzed in terms of parameters such as the scalar spectral index ns and the tensor to scalar ratio r, while dark energy models are studied in terms of the equation of state parameter w. Motivated by the fact that both deal with periods of accelerated expansion, we study the evolution of w during inflation, in order ...

Observations indicate that the expansion of the Universe is accelerating, which is attributed to a `dark energy' component that opposes gravity. There is a purely geometric test of the expansion of the Universe (the Alcock-Paczynski test), which would provide an independent way of investigating the abundance () and equation of state () ...

The accelerating expansion of the Universe at recent epochs has called into question the validity of general relativity on cosmological scales. One probe of gravity is a comparison of expansion history of the Universe with the history of structure growth via gravitational instability: general relativity predicts a specific relation ...

Traditionally, inflationary models are analyzed in terms of parameters such as the scalar spectral index n{sub s} and the tensor to scalar ratio r, while dark energy models are studied in terms of the equation of state parameter w. Motivated by the fact that both deal with periods of accelerated expansion, we study the evolution of w during inflation, in ...

Galactic cosmic rays (CRs) are widely believed to be accelerated by shock waves associated with the expansion of supernova ejecta into the interstellar medium. A key issue in this long-standing conjecture is a theoretical prediction that the interstellar magnetic field can be substantially amplified at the shock of a young supernova ...

... to investigate ram accelerator phenomena using expansion tube and shock tube facilities. ... to establish modern experimental capabilities for ...

The present cosmic accelerating stage is discussed through a new kinematic method based on the Sunyaev-Zel'dovich effect (SZE) and X-ray surface brightness data from galaxy clusters. By using the SZE/X-ray data from 38 galaxy clusters in the redshift range 0.14<=z<=0.89 [Bonament et al., Astrop. J. 647, 25 (2006)] it is found that the present ...

We explore consistency among different distance measures, including Supernovae Type Ia data, measurements of the Hubble parameter, and determination of the Baryon acoustic oscillation scale. We present new constraints on the cosmic transparency combining H(z) data together with the latest Supernovae Type Ia data compilation. This combination, in the context of a flat ?CDM ...

We consider here a spherically symmetric but inhomogeneous universe filled with a massless scalar field. The model obeys two constraints. The first one is that the gradient of the scalar field is timelike everywhere. The second constraint is that the radial coordinate basis vector is a unit vector field in the comoving coordinate system. We find that the resultant dynamical solutions compose a ...

We consider scalar-Gauss-Bonnet and modified Gauss-Bonnet gravities and reconstruct these theories from the universe expansion history. In particular, we are able to construct versions of those theories (with and without ordinary matter), in which the matter-dominated era makes a transition to the cosmic acceleration epoch. In several ...

of which cluster configuration is chosen is determined by reaction channel and nuclear structure considerations. The convergence of a cluster expansion ...

... the absorbing material between the cloud chamber and the Geiger counter used to trigger the chamber expansion. This ...

The Big Bang - Cosmic Expansion. According to Big Bang theory, the scale of the universe increases with time at a rate that depends on the density of matter ...

from spherical symmetry, and illuminate the physical origin of the empirical correlations used to standardize these supernovae as measures of cosmic expansion. I then...

The observation that type Ia supernovae (SNe Ia) are fainter than expected given their redshifts 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 some dark energy field that pervades the universe. We explore ...

Neutrinos coupled to an underlying scalar field in the scenario for unification of mass varying dark matter and cosmon-like dark energy is examined. In the presence of a tiny component of mass varying neutrinos, the conditions for the present cosmic acceleration and for the stability issue are reproduced. It is assumed that sterile neutrinos behave like ...

An impressive amount of different astrophysical data converges towards the picture of a spatially flat Universe undergoing today a phase of accelerated expansion. The nature of the dark energy dominating the energy content of the Universe is still unknown, and a lot of different scenarios are viable candidates to explain cosmic ...

Epstein, R. I.: 1980, 'The Acceleration of Interstellar Grains and the Composition of the Cosmic. Rays', Mon. Not. R. Astr. Soc., 193, 723729. ...

Jun 1, 1983 ... Subject Terms: ASTRONOMICAL MODELS; COSMIC RAYS; INTERSTELLAR MATTER; MATHEMATICAL MODELS; PARTICLE ACCELERATION; POWER SPECTRA; ...

are a type of cosmic ray that move away from the Sun due to plasma heating, acceleration, and numerous other forces; on the scale of cosmic radiation, ...

Experiments on the search for magnetic monopoles in cosmic radiation, in different substances on the Earth and at accelerators are described. It is noted that the flux of cosmic monopoles is very small and its reliable registration requires too much effor...

We propose new methods for estimating the energy of the incident particles in high-energy cosmic-ray collisions. We demonstrate their validity in accelerator experiments.

Dec 29, 2006 ... Cosmic rays: A stream of particles that have been accelerated to ... The Delta II is the latest generation of Delta medium-launch vehicle. ...

Electromagnetic and particle energy fluxes are equipartitioned in a superrelativistic plasma wave. The consequences for cosmic-ray acceleration by pulsars are investigated. (Author)

This paper summarizes highlights of the OG3.1, 3.2 and 3.3 sessions of the 26th International Cosmic

Studies with CRS data will provide information on the energy content, origin and acceleration process, life history, and dynamics of cosmic rays in the ...

In some galaxies, matter falling onto a supermassive black hole is ejected in narrow jets moving at close to the speed of light. New observations provide insight into the workings of these cosmic accelerators.

The observation of neutrinos from cosmic accelerators will be revolutionary. High energy neutrinos are closely connected to ultrahigh energy cosmic rays and their sources. Cosmic ray sources are likely to produce neutrinos and the propagation of ultrahigh cosmic rays from distant sources can ...

The self-accelerating braneworld model (DGP) can be tested from measurements of the expansion history of the Universe and the formation of structure. Current constraints on the expansion history from supernova luminosity distances, the cosmic microwave background (CMB), and the Hubble constant exclude the simplest ...

After the solar wind termination shock crossings of the Voyager spacecraft, the acceleration of anomalous cosmic rays has become a very contentious subject. In this paper we examine several topics pertinent to anomalous cosmic ray oxygen acceleration and transport using a numerical cosmic ray ...

Our universe experienced the accelerated expansion at least twice; an extreme inflationary acceleration in the early universe and the recent mild acceleration. By introducing the Bose-Einstein condensation (BEC) phase of a boson field, we have been developing a unified model of dark energy (DE) and dark matter (DM) ...

Our universe experienced the accelerated expansion at least twice; an extreme inflationary acceleration in the early universe and the recent mild acceleration. By introducing the Bose-Einstein condensation (BEC) phase of a boson field, we have been developing a unified model of dark energy (DE) and dark matter (DM) ...

Observations exploring the contemporary cosmic acceleration have sparked interest in dark energy models possessing equations of state with w<-1. We review how the cosmic expansion history of a Dvali-Gabadadze-Porrati (DGP) braneworld model with a standard brane cosmological constant can mimic that of ...

After Hubble's discovery of cosmic expansion, cosmologists expected that the mass and fate of the Universe would be revealed by its deceleration. In the 1990's two teams took up the challenge to measure the cosmic deceleration using yardsticks built from exploding stars called supernovae. I was a member of the High-z Team. In the fall ...

With a model independent method the expansion history H(z), the deceleration parameter q(z) of the universe and the equation of state w(z) for the dark energy are reconstructed directly from the 192 Sne Ia (type Ia supernovae) data points which are contained in the new ESSENCE (Equation of State: Supernovae Trace Cosmic Expansion) Sne ...

Observations of distant supernovae and the fluctuations in the cosmic microwave background (CMB) indicate that the expansion of the Universe may be accelerating under the action of a 'cosmological constant' or some other form of 'dark energy'. This dark energy now appears to dominate the Universe and not only alters its ...