WebGrazer Summary

Thu Nov 05 18:25:20 PST 2009


hep-ph

[3]  arXiv:0911.0972 [ps, pdf, other]
Title:Study of B_{c}\to J/\psi K decays in the perturbative QCD approach
Comments: 4 pages,1 figure
Subjects: High Energy Physics - Phenomenology (hep-ph)

In this note, we calculate the branching ratio of B_c\to J/\psi K in the framework of perturbative QCD approach based on k_T factorization. This decay can occur only via tree level diagrams in the Standard Model. We find that the branching ratio of B_c\to J/\psi K is about (2-3)\times10^{-4}. The large branching ratio and the clear signals of the final states make the measurement of B_c\to J/\psi K easily at LHC-b experiments.

CiteULike logo

[4]  arXiv:0911.0994 [ps, pdf, other]
Title:Asymmetry observables in e+ e- --> pi+ pi- gamma in the phi region within a chiral unitary approach
Authors: L. Roca, E. Oset
Subjects: High Energy Physics - Phenomenology (hep-ph)

We make a theoretical study of the charge and forward-backward pion asymmetries in the e+e- --> pi+ pi- gamma process on and off the phi resonance energy. These observables are rather sensitive to the inner details of the theoretical models to describe the reaction. In addition to the standard implementation of the initial state radiation (ISR) and the Bremsstrahlung contribution to the final state radiation (FSR), we use the techniques of the chiral unitary approach to evaluate the contribution from the mechanisms of phi decay into pi+pi-gamma. This contribution involves the implementation of final state interaction from direct chiral loops, the exchange of vector and axial-vector resonances and the final state interaction through the consideration of the meson-meson unitarized amplitudes, which where found important in a previous work describing the phi --> pi pi gamma. We find a good reproduction of the experimental data from KLOE for the forward-backward asymmetry, both at the phi peak and away from it. We also make predictions for the angular distributions of the charge asymmetry and show that this observable is very sensitive to the chiral loops involved in phi radiative decay.

CiteULike logo

[5]  arXiv:0911.0997 [ps, pdf, other]
Title:One-loop effective potential in M4 x T2 with and without 't Hooft flux
Subjects: High Energy Physics - Phenomenology (hep-ph)

We review the basic notions of compactification in the presence of a background flux. In extra-dimentional models with more than five dimensions, Scherk and Schwarz boundary conditions have to satisfy 't Hooft consistency conditions. Different vacuum configurations can be obtained, depending whether trivial or non-trivial 't Hooft flux is considered. The presence of the "magnetic" background flux provide, in addition, a mechanism for producing four-dimensional chiral fermions. Particularizing to the six-dimensional case, we calculate the one-loop effective potential for a U(N) gauge theory on M4 x T2. We firstly review the well known results of the trivial 't Hooft flux case, where one-loop contributions produce the usual Hosotani dynamical symmetry breaking. Finally we applied our result for describing, for the first time, the one-loop contributions in the non-trivial 't Hooft flux case.

CiteULike logo

[6]  arXiv:0911.1006 [ps, pdf, other]
Title:Realistic Flipped SU(5) from Orbifold SO(10)
Comments: 25 pages, 1 fig
Subjects: High Energy Physics - Phenomenology (hep-ph)

We propose a realistic flipped SU(5) model derived from a five-dimensional orbifold SO(10) model. The Standard Model (SM) fermion masses and mixings are explained by combining the traditional Froggatt-Nielsen mechanism with the five-dimensional wave function profiles of the SM fermions. Employing tree-level spontaneous R-symmetry breaking in the hidden sector and extra(ordinary) gauge mediation, we obtain realistic supersymmetry breaking soft mass terms with non-vanishing gaugino masses. Including the messenger fields at the intermediate scale and Kaluza-Klein states at the compactification scale, we study gauge coupling unification. We show that the SO(10) unified gauge coupling is very strong and the unification scale can be much higher than the compactification scale. We briefly discuss proton decay as well.

CiteULike logo

[7]  arXiv:0911.1018 [ps, pdf, other]
Title:Explaining LSND and MiniBooNE using altered neutrino dispersion relations
Comments: 3 pages, 1 figure, Proceedings for Erice 2009 Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physics
Subjects: High Energy Physics - Phenomenology (hep-ph)

We investigate the possibility to explain the MiniBooNE anomaly by CPT and Lorentz symmetry violating neutrino-antineutrino oscillations in a two generation framework. We work with four non-zero CPT-violating parameters that allow for resonant enhancements in neutrino-antineutrino oscillation phenomena in vacuo which are suitably described in terms of charge conjugation eigenstates of the system. We study the relation between the flavor, charge conjugation and mass eigenbasis of neutrino-antineutrino oscillations and examine the interplay between the available CPT-violating parameter space and possible resonance structures.

CiteULike logo

[9]  arXiv:0911.1031 [ps, pdf, other]
Title:Understanding the evolution of transverse-momentum dependent parton densities
Comments: 4 pages. Talk presented by the first author at Workshop on the International Workshop "Transverse Partonic Structure of Hadrons", 21-26 Jun 2009, Erevan, Armenia
Subjects: High Energy Physics - Phenomenology (hep-ph)

Different approaches to define transverse-momentum dependent parton distribution functions are considered from the point of view of their renormalization-group properties. The associated one-loop anomalous dimensions of these quantities are presented and compared to each other. We give arguments in favor of the "pure light-like" definition, and the use of the light-cone gauge.

CiteULike logo

[10]  arXiv:0911.1085 [ps, pdf, other]
Title:Signal and Background in e+e- ->t anti-t H
Comments: 9 pages, 2 figures, presented at the XXXIII International Conference of Theoretical Physics, "Matter to the Deepest", Ustron, Poland, September 11-16, 2009
Subjects: High Energy Physics - Phenomenology (hep-ph)

We discuss the reaction of associated production of a top quark pair and a Higgs boson at the future e+e- linear collider that can be used to determine the top-Higgs Yukawa coupling. Taking into account decays of the top quarks and the light Higgs boson leads to reactions with 8 fermions in the final state which, in the framework of the standard model, receive contributions typically from many thousands Feynman diagrams. An overwhelming majority of the diagrams comprises the off resonance background to the resonant signal of associated production and decay of the top quark pair and Higgs boson. We address the signal and background issue by comparing cross sections calculated with the signal diagrams only and with the complete sets of the diagrams.

CiteULike logo

[11]  arXiv:0911.1086 [ps, pdf, other]
Title:Laboratory Tests of Chameleon Models
Comments: Contribution to the "5th Patras Workshop on Axions, WIMPs and WISPs", Durham 13-17 July 2009
Subjects: High Energy Physics - Phenomenology (hep-ph)

We present a cursory overview of chameleon models of dark energy and their laboratory tests with an emphasis on optical and Casimir experiments. Optical experiments measuring the ellipticity of an initially polarised laser beam are sensitive to the coupling of chameleons to photons. The next generation of Casimir experiments may be able to unravel the nature of the scalar force mediated by the chameleon between parallel plates.

CiteULike logo

[12]  arXiv:0911.1120 [pdf, other]
Title:Freeze-In Production of FIMP Dark Matter
Comments: 30 pages, 7 figures, PDFLaTex
Subjects: High Energy Physics - Phenomenology (hep-ph)

We propose an alternate, calculable mechanism of dark matter genesis, "thermal freeze-in," involving a Feebly Interacting Massive Particle (FIMP) interacting so feebly with the thermal bath that it never attains thermal equilibrium. As with the conventional "thermal freeze-out" production mechanism, the relic abundance reflects a combination of initial thermal distributions together with particle masses and couplings that can be measured in the laboratory or astrophysically. The freeze-in yield is IR dominated by low temperatures near the FIMP mass and is independent of unknown UV physics, such as the reheat temperature after inflation. Moduli and modulinos of string theory compactifications that receive mass from weak-scale supersymmetry breaking provide implementations of the freeze-in mechanism, as do models that employ Dirac neutrino masses or GUT-scale-suppressed interactions. Experimental signals of freeze-in and FIMPs can be spectacular, including the production of new metastable coloured or charged particles at the LHC as well as the alteration of big bang nucleosynthesis.

CiteULike logo

[13]  arXiv:0911.1124 [ps, pdf, other]
Title:Antiproton and Radio Constraints on the Dark Matter Interpretation of the Fermi Gamma Ray Observations of the Galactic Center
Comments: 4 pages, 2 figures
Subjects: High Energy Physics - Phenomenology (hep-ph)

Recently, it was suggested that the gamma rays observed by the Fermi Gamma Ray Space Telescope from the direction of the galactic center could surprisingly well be described by a dark matter annihilation scenario, both in terms of their angular distribution and energy spectrum. Here, I point out that such a scenario would be in considerable tension with existing antiproton data, in particular the new PAMELA measurements. Radio data are even more constraining, thus disfavoring the dark matter hypothesis and making an astrophysical explanation of the observations much more plausible.

CiteULike logo

[22]  arXiv:0908.4122 (replaced) [ps, pdf, other]
Title:SO(10) domain-wall brane models
Comments: 16 pages, 2 figures A new section has been added on page 12. 3 new paragraphs have been added to the end of section (IV B) 'Localising Fermions' and 1 new paragraph has been added to section (IV C)'Adding Warped Gravity'. A new reference has been added to the bibliography at position [29]. The paper has been accepted in to Phys. Rev. D
Subjects: High Energy Physics - Phenomenology (hep-ph)
CiteULike logo

[23]  arXiv:0909.1495 (replaced) [pdf, other]
Title:Prospects for the Measurement of the Unitarity Triangle Angle gamma from B0 to DK+pi- Decays
Comments: 12 pages, 10 figures. v2 as published
Journal-ref: Phys. Rev. D80, 092002 (2009)
Subjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex)
CiteULike logo

[24]  arXiv:0910.1350 (replaced) [ps, pdf, other]
Title:Gluon-initiated production of a Kaluza-Klein gluon in a Bulk Randall-Sundrum model
Comments: 31 pages, 7 figures. v2: Added references
Subjects: High Energy Physics - Phenomenology (hep-ph)
CiteULike logo


hep-th

[4]  arXiv:0911.0967 [ps, pdf, other]
Title:Hints of Integrability Beyond the Planar Limit
Comments: 25+1 pages
Subjects: High Energy Physics - Theory (hep-th)

The problem of computing the anomalous dimensions of a class of (nearly) half-BPS operators with a large R-charge is reduced to the problem of diagonalizing a Cuntz oscillator chain. Due to the large dimension of the operators we consider, non-planar corrections must be summed to correctly construct the Cuntz oscillator dynamics. These non-planar corrections do not represent quantum corrections in the dual gravitational theory, but rather, they account for the backreaction from the heavy operator whose dimension we study. Non-planar corrections accounting for quantum corrections seem to spoil integrability, in general. It is interesting to ask if non-planar corrections that account for the backreaction also spoil integrability. We find a limit in which our Cuntz chain continues to admit extra conserved charges suggesting that integrability might survive.

CiteULike logo

[6]  arXiv:0911.1035 [ps, pdf, other]
Title:N-Body Nuclear Forces at Short Distances in Holographic QCD
Comments: 4 pages
Subjects: High Energy Physics - Theory (hep-th)

We provide a calculation of N-body (N>2) nucleon interactions at short distances in holographic QCD. In the Sakai-Sugimoto model of large N_c massless QCD, N baryons are described by N Yang-Mills instantons in 5 spacetime dimensions. We compute a classical short distance interaction hamiltonian for N 'tHooft instantons. This corresponds to N baryons sharing identical classical spins and isospins. We find that genuine N-body nuclear forces turn out to vanish for N>2, at the leading order. This suggests that classical N-body forces are always suppressed compared with 2-body forces.

CiteULike logo

[7]  arXiv:0911.1063 [ps, pdf, other]
Title:The cosmological constant and higher dimensional dilatation symmetry
Authors: C. Wetterich
Comments: 38 pages, 1 figure
Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

We discuss the hypothesis of a fixed point for quantum gravity coupled to a scalar, in the limit where the scalar field goes to infinity, accompanied by a suitable scaling of the metric. We propose that no scalar potential is present for the dilatation symmetric quantum effective action at the fixed point. Dimensional reduction of such a higher dimensional effective action leads to solutions with a vanishing effective four-dimensional constant. Under rather general circumstances these are the only quasistatic stable solutions with finite four-dimensional gravitational constant. If cosmological runaway solutions approach the fixed point as time goes to infinity, the cosmological constant vanishes asymptotically. For our old Universe the fixed point is not yet reached completely, resulting in a tiny amount of dark energy, comparable to dark matter. We discuss explicitly higher dimensional geometries which realize such asymptotic solutions for $t\to\infty$. They include Ricci-flat spaces as well as warped spaces, potentially with singularities.

CiteULike logo

[13]  arXiv:0911.0129 (cross-list from math.RT) [ps, pdf, other]
Title:Super duality and irreducible characters of ortho-symplectic Lie superalgebras
Comments: 34 pages
Subjects: Representation Theory (math.RT); High Energy Physics - Theory (hep-th)

We formulate and establish a super duality which connects parabolic categories $O$ between the ortho-symplectic Lie superalgebras and classical Lie algebras of $BCD$ types. This provides a complete and conceptual solution of the irreducible character problem for the ortho-symplectic Lie superalgebras in a parabolic category $O$, which includes all finite-dimensional irreducible modules, in terms of classical Kazhdan-Lusztig polynomials.

CiteULike logo

[16]  arXiv:0911.0802 (cross-list from gr-qc) [ps, pdf, other]
Title:On the global structure of the Pomeransky-Senkov black holes
Comments: 72 pages, 20 figures
Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

We construct analytic extensions of the Pomeransky-Senkov metrics with multiple Killing horizons and asymptotic regions. We show that, in our extensions, the singularities associated to an obstruction to differentiability of the metric lie beyond event horizons. We analyze the topology of the non-empty singular set, which turns out to be parameter-dependent. We present numerical evidence for stable causality of the domain of outer communications. The resulting global structure is somewhat reminiscent of that of Kerr space-time.

CiteULike logo

[17]  arXiv:0911.0864 (cross-list from gr-qc) [ps, pdf, other]
Title:The ideal relativistic rotating gas as a perfect fluid with spin
Authors: F. Becattini, L. Tinti (University of Florence, Italy)
Comments: 23 pages, 1 figure
Subjects: General Relativity and Quantum Cosmology (gr-qc); Statistical Mechanics (cond-mat.stat-mech); High Energy Physics - Theory (hep-th)

We show that the ideal relativistic spinning gas at complete thermodynamical equilibrium is a fluid with a non-vanishing spin density tensor \sigma_\mu \nu. After having obtained the expression of the local spin-dependent phase space density f(x,p)_(\sigma \tau) in the Boltzmann approximation, we derive the spin density tensor and show that it is proportional to the acceleration tensor Omega_\mu \nu constructed with the Frenet-Serret tetrad. We recover the proper generalization of the fundamental thermodynamical relation, involving an additional term -(1/2) \Omega_\mu \nu \sigma^\mu \nu. We also show that the spin density tensor has a non-vanishing projection onto the four-velocity field, i.e. t^\mu= sigma_\mu \nu u^\nu \ne 0, in contrast to the common assumption t^\mu = 0, known as Frenkel condition, in the thus-far proposed theories of relativistic fluids with spin. We briefly address the viewpoint of the accelerated observer and inertial spin effects.

CiteULike logo

[20]  arXiv:0708.1270 (replaced) [ps, pdf, other]
Title:Black Hole Entropy Function, Attractors and Precision Counting of Microstates
Authors: Ashoke Sen
Comments: LaTeX file, 196 pages, based on lectures given at various schools; v2: added appendix E containing analysis of the multiple D5-brane system, expanded discussion on duality orbits, other minor changes, references added; v3: equations (5.6.20) and (5.6.21) corrected; v4: minor corrections to equations (C.19), (C.20)
Journal-ref: Gen.Rel.Grav.40:2249-2431,2008
Subjects: High Energy Physics - Theory (hep-th)
CiteULike logo

[25]  arXiv:0906.1345 (replaced) [ps, pdf, other]
Title:Primordial Non-Gaussianities from the Trispectra in Multiple Field Inflationary Models
Comments: 36 pages, 8 eps figures; v2 more general two-field model considered, JCAP version
Journal-ref: JCAP11(2009)007
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
CiteULike logo

[32]  arXiv:0910.1345 (replaced) [ps, pdf, other]
Title:Renormalization of Lorentz non-invariant actions and manifest T-duality
Comments: V2: reference added, version to appear in Nucl. Phys. B
Subjects: High Energy Physics - Theory (hep-th)
CiteULike logo

[33]  arXiv:0910.1601 (replaced) [ps, pdf, other]
Title:Essentials of Blackfold Dynamics
Comments: 37 pages, v2 minor comments and a reference added
Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
CiteULike logo


astro-ph cosmology

[4]  arXiv:0911.0976 [ps, pdf, other]
Title:Neutrino mass from cosmology: Impact of high-accuracy measurement of the Hubble constant
Comments: 22 pages, 6 figures, 12 tables
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Non-zero neutrino mass would affect the evolution of the Universe in observable ways, and a strong constraint on the mass can be achieved using combinations of cosmological data sets. We focus on the power spectrum of cosmic microwave background (CMB) anisotropies, the Hubble constant H_0, and the length scale for baryon acoustic oscillations (BAO) to investigate the constraint on the neutrino mass, m_nu. We analyze data from multiple existing CMB studies (WMAP5, ACBAR, CBI, BOOMERANG, and QUAD), recent measurement of H_0 (SHOES), with about two times lower uncertainty (5%) than previous estimates, and recent treatments of BAO from the Sloan Digital Sky Survey (SDSS). We obtained an upper limit of m_nu < 0.2eV (95% C.L.), for a flat LambdaCDM model. This is a 40% reduction in the limit derived from previous H_0 estimates and one-third lower than can be achieved with extant CMB and BAO data. We also analyze the impact of smaller uncertainty on measurements of H_0 as may be anticipated in the near term, in combination with CMB data from the Planck mission, and BAO data from the SDSS/BOSS program. We demonstrate the possibility of a 5 sigma detection for a fiducial neutrino mass of 0.1eV or a 95% upper limit of 0.04eV for a fiducial of m_nu = 0eV. These constraints are about 50% better than those achieved without external constraint. We further investigate the impact on modeling where the dark-energy equation of state is constant but not necessarily -1, or where a non-flat universe is allowed. In these cases, the next-generation accuracies of Planck, BOSS, and 1% measurement of H_0 would all be required to obtain the limit m_nu < 0.05 - 0.06eV (95% C.L.) for the fiducial of m_nu = 0eV. The independence of systematics argues for pursuit of both BAO and H_0 measurements.

CiteULike logo

[8]  arXiv:0911.1056 [ps, pdf, other]
Title:Detection of distant AGN by MAGIC: the transparency of the Universe to high-energy photons
Authors: Marco Roncadelli (1), Alessandro De Angelis (2), Oriana Mansutti (3) ((1) INFN, Sezione di Pavia, Italy, (2) Dipartimento di Fisica, Universita' di Udine, and INAF and INFN, Sezioni di Trieste, Italy, (3) Dipartimento di Fisica, Universita' di Udine, and INFN, Sezione di Trieste, Italy)
Comments: 4 pages, 1 figure, Proceeding of the Conference "4th Patras Workshop on Axions, WIMPs and WISPs"
Journal-ref: DESY Conf. Proc., June 18, 2008, pp. 53-56
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

The recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided photon oscillations into a veri light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect explains the observed spectrum of 3C279. Our prediction can be tested in the near future by the satellite-borne GLAST detector as well as by the ground-based Imaging Atmospheric Cherenkov Telescpoes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensive Air Shower arrays ARGO-YBJ and MILAGRO.

CiteULike logo

[10]  arXiv:0911.1069 [ps, pdf, other]
Title:3D Spectroscopy of Local Luminous Compact Blue Galaxies: Kinematics of NGC 7673
Authors: J. Pérez-Gallego (1), R. Guzmán (1), A. Castillo-Morales (2), F. J. Castander (3), J. Gallego (2), C. A. Garland (4), N. Gruel (1), D. J. Pisano (5), S. F. Sánchez (6), J. Zamorano (2) ((1) Department of Astronomy, University of Florida; (2) Departamento de Astrofísica, Universidad Complutense de Madrid; (3) Institut de Ciències de l'Espai (ICE/CSIC), Universitat Autònoma de Barcelona; (4) Department of Natural Sciences, Castleton State College; (5) Department of Physics, West Virginia University (WVU/NRAO); (6) Centro Astronómico Hispano Alemán)
Comments: Accepted for publication by MNRAS. The paper contains 10 figures and 2 tables
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

The kinematic properties of the ionized gas of local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are presented using three dimensional data taken with the PPAK integral field unit at the 3.5-m telescope in the Centro Astron\'omico Hispano Alem\'an. Our data reveal an asymmetric rotating velocity field with a peak to peak difference of 60 km s$^{-1}$. The kinematic centre is found to be at the position of a central velocity width maximum ($\sigma=54\pm1$ km s$^{-1}$), which is consistent with the position of the luminosity-weighted centroid of the entire galaxy. The position angle of the minor rotation axis is 168$^{\circ}$ as measured from the orientation of the velocity field contours. At least two decoupled kinematic components are found. The first one is compact and coincides with the position of the second most active star formation region (clump B). The second one is extended and does not have a clear optical counterpart. No evidence of active galactic nuclei activity or supernovae galactic winds powering any of these two components has been found. Our data, however, show evidence in support of a previously proposed minor merger scenario in which a dwarf galaxy, tentatively identified with clump B, is falling into NGC 7673. and triggers the starburst. Finally, it is shown that the dynamical mass of this galaxy may be severely underestimated when using the derived rotation curve or the integrated velocity width, under the assumption of virialization.

CiteULike logo

[19]  arXiv:0911.0980 (cross-list from astro-ph.GA) [ps, pdf, other]
Title:Chemo-dynamical simulations of galaxies
Authors: Chiaki Kobayashi
Comments: 6 pages, 3 figures, To appear in IAU Symposium 265, Chemical Abundances in the Universe: Connecting First Stars to Planets
Subjects: Galaxy Astrophysics (astro-ph.GA); Cosmology and Extragalactic Astrophysics (astro-ph.CO)

We simulate the formation and evolution of galaxies with a self-consistent 3D hydrodynamical model including star formation, supernova feedback, and chemical enrichment. Hypernova feedback plays an essential role not only in solving the [Zn/Fe] problem, but also reproducing the cosmic star formation rate history and the mass-metallicity relations. In a Milky-Way type galaxy, kinematics and chemical abundances are different in bulge, disk, and thick disk because of different star formation histories and the contribution of Type Ia Supernovae.

CiteULike logo

[28]  arXiv:0911.0138 (replaced) [ps, pdf, other]
Title:HST Discovery of a z = 3.9 Multiply Imaged Galaxy Behind the Complex Cluster Lens WARPS J1415.1+36 at z = 1.026
Comments: 5 pages, 2 figures, accepted by ApJL. See this http URL for additional information pertaining to the HST Cluster SN Survey. (This added URL is the only change in this version.)
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)
CiteULike logo


astro-ph high energy

[2]  arXiv:0911.0926 [pdf]
Title:Sub-luminous type Ia supernovae from the mergers of equal-mass white dwarfs with M~0.9 M_sun
Comments: Accepted to Nature
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)

Type Ia supernovae (SNe Ia) are thought to result from thermonuclear explosions of carbon-oxygen white dwarf stars. Existing models generally explain the observed properties, with the exception of the sub-luminous 1991-bg-like supernovae. It has long been suspected that the merger of two white dwarfs could give rise to a type Ia event, but hitherto simulations have failed to produce an explosion. Here we report a simulation of the merger of two equal-mass white dwarfs that leads to an underluminous explosion, though at the expense of requiring a single common-envelope phase, and component masses of ~0.9 M_sun. The light curve is too broad, but the synthesized spectra, red colour and low expansion velocities are all close to what is observed for sub-luminous 1991bg-like events. While mass ratios can be slightly less than one and still produce an underluminous event, the masses have to be in the range 0.83-0.9 M_sun.

CiteULike logo

[12]  arXiv:0911.1056 (cross-list from astro-ph.CO) [ps, pdf, other]
Title:Detection of distant AGN by MAGIC: the transparency of the Universe to high-energy photons
Authors: Marco Roncadelli (1), Alessandro De Angelis (2), Oriana Mansutti (3) ((1) INFN, Sezione di Pavia, Italy, (2) Dipartimento di Fisica, Universita' di Udine, and INAF and INFN, Sezioni di Trieste, Italy, (3) Dipartimento di Fisica, Universita' di Udine, and INFN, Sezione di Trieste, Italy)
Comments: 4 pages, 1 figure, Proceeding of the Conference "4th Patras Workshop on Axions, WIMPs and WISPs"
Journal-ref: DESY Conf. Proc., June 18, 2008, pp. 53-56
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

The recent detection of blazar 3C279 by MAGIC has confirmed previous indications by H.E.S.S. that the Universe is more transparent to very-high-energy gamma rays than previously thought. We show that this fact can be reconciled with standard blazar emission models provided photon oscillations into a veri light Axion-Like Particle occur in extragalactic magnetic fields. A quantitative estimate of this effect explains the observed spectrum of 3C279. Our prediction can be tested in the near future by the satellite-borne GLAST detector as well as by the ground-based Imaging Atmospheric Cherenkov Telescpoes H.E.S.S., MAGIC, CANGAROO III, VERITAS and by the Extensive Air Shower arrays ARGO-YBJ and MILAGRO.

CiteULike logo



yesterday, 2 days back, 3 days back
Daily Trackback

This summary was produced automatically by WebGrazer.